Provided by: libav-tools_9.20-0ubuntu0.14.04.1_amd64 
NAME
avconv - avconv video converter
SYNOPSIS
avconv [global options] [[infile options][-i infile]]... {[outfile options] outfile}...
DESCRIPTION
avconv is a very fast video and audio converter that can also grab from a live audio/video source. It can
also convert between arbitrary sample rates and resize video on the fly with a high quality polyphase
filter.
avconv reads from an arbitrary number of input "files" (which can be regular files, pipes, network
streams, grabbing devices, etc.), specified by the "-i" option, and writes to an arbitrary number of
output "files", which are specified by a plain output filename. Anything found on the command line which
cannot be interpreted as an option is considered to be an output filename.
Each input or output file can in principle contain any number of streams of different types
(video/audio/subtitle/attachment/data). Allowed number and/or types of streams can be limited by the
container format. Selecting, which streams from which inputs go into output, is done either automatically
or with the "-map" option (see the Stream selection chapter).
To refer to input files in options, you must use their indices (0-based). E.g. the first input file is
0, the second is 1 etc. Similarly, streams within a file are referred to by their indices. E.g. "2:3"
refers to the fourth stream in the third input file. See also the Stream specifiers chapter.
As a general rule, options are applied to the next specified file. Therefore, order is important, and you
can have the same option on the command line multiple times. Each occurrence is then applied to the next
input or output file. Exceptions from this rule are the global options (e.g. verbosity level), which
should be specified first.
Do not mix input and output files -- first specify all input files, then all output files. Also do not
mix options which belong to different files. All options apply ONLY to the next input or output file and
are reset between files.
• To set the video bitrate of the output file to 64kbit/s:
avconv -i input.avi -b 64k output.avi
• To force the frame rate of the output file to 24 fps:
avconv -i input.avi -r 24 output.avi
• To force the frame rate of the input file (valid for raw formats only) to 1 fps and the frame rate of
the output file to 24 fps:
avconv -r 1 -i input.m2v -r 24 output.avi
The format option may be needed for raw input files.
DETAILED DESCRIPTION
The transcoding process in avconv for each output can be described by the following diagram:
_______ ______________ _________ ______________ ________
| | | | | | | | | |
| input | demuxer | encoded data | decoder | decoded | encoder | encoded data | muxer | output |
| file | ---------> | packets | ---------> | frames | ---------> | packets | -------> | file |
|_______| |______________| |_________| |______________| |________|
avconv calls the libavformat library (containing demuxers) to read input files and get packets containing
encoded data from them. When there are multiple input files, avconv tries to keep them synchronized by
tracking lowest timestamp on any active input stream.
Encoded packets are then passed to the decoder (unless streamcopy is selected for the stream, see further
for a description). The decoder produces uncompressed frames (raw video/PCM audio/...) which can be
processed further by filtering (see next section). After filtering the frames are passed to the encoder,
which encodes them and outputs encoded packets again. Finally those are passed to the muxer, which writes
the encoded packets to the output file.
Filtering
Before encoding, avconv can process raw audio and video frames using filters from the libavfilter
library. Several chained filters form a filter graph. avconv distinguishes between two types of
filtergraphs - simple and complex.
Simple filtergraphs
Simple filtergraphs are those that have exactly one input and output, both of the same type. In the above
diagram they can be represented by simply inserting an additional step between decoding and encoding:
_________ __________ ______________
| | | | | |
| decoded | simple filtergraph | filtered | encoder | encoded data |
| frames | -------------------> | frames | ---------> | packets |
|_________| |__________| |______________|
Simple filtergraphs are configured with the per-stream -filter option (with -vf and -af aliases for video
and audio respectively). A simple filtergraph for video can look for example like this:
_______ _____________ _______ _____ ________
| | | | | | | | | |
| input | ---> | deinterlace | ---> | scale | ---> | fps | ---> | output |
|_______| |_____________| |_______| |_____| |________|
Note that some filters change frame properties but not frame contents. E.g. the "fps" filter in the
example above changes number of frames, but does not touch the frame contents. Another example is the
"setpts" filter, which only sets timestamps and otherwise passes the frames unchanged.
Complex filtergraphs
Complex filtergraphs are those which cannot be described as simply a linear processing chain applied to
one stream. This is the case e.g. when the graph has more than one input and/or output, or when output
stream type is different from input. They can be represented with the following diagram:
_________
| |
| input 0 |\ __________
|_________| \ | |
\ _________ /| output 0 |
\ | | / |__________|
_________ \| complex | /
| | | |/
| input 1 |---->| filter |\
|_________| | | \ __________
/| graph | \ | |
/ | | \| output 1 |
_________ / |_________| |__________|
| | /
| input 2 |/
|_________|
Complex filtergraphs are configured with the -filter_complex option. Note that this option is global,
since a complex filtergraph by its nature cannot be unambiguously associated with a single stream or
file.
A trivial example of a complex filtergraph is the "overlay" filter, which has two video inputs and one
video output, containing one video overlaid on top of the other. Its audio counterpart is the "amix"
filter.
Stream copy
Stream copy is a mode selected by supplying the "copy" parameter to the -codec option. It makes avconv
omit the decoding and encoding step for the specified stream, so it does only demuxing and muxing. It is
useful for changing the container format or modifying container-level metadata. The diagram above will in
this case simplify to this:
_______ ______________ ________
| | | | | |
| input | demuxer | encoded data | muxer | output |
| file | ---------> | packets | -------> | file |
|_______| |______________| |________|
Since there is no decoding or encoding, it is very fast and there is no quality loss. However it might
not work in some cases because of many factors. Applying filters is obviously also impossible, since
filters work on uncompressed data.
STREAM SELECTION
By default avconv tries to pick the "best" stream of each type present in input files and add them to
each output file. For video, this means the highest resolution, for audio the highest channel count. For
subtitle it's simply the first subtitle stream.
You can disable some of those defaults by using "-vn/-an/-sn" options. For full manual control, use the
"-map" option, which disables the defaults just described.
OPTIONS
All the numerical options, if not specified otherwise, accept in input a string representing a number,
which may contain one of the SI unit prefixes, for example 'K', 'M', 'G'. If 'i' is appended after the
prefix, binary prefixes are used, which are based on powers of 1024 instead of powers of 1000. The 'B'
postfix multiplies the value by 8, and can be appended after a unit prefix or used alone. This allows
using for example 'KB', 'MiB', 'G' and 'B' as number postfix.
Options which do not take arguments are boolean options, and set the corresponding value to true. They
can be set to false by prefixing with "no" the option name, for example using "-nofoo" in the command
line will set to false the boolean option with name "foo".
Stream specifiers
Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers are used to precisely
specify which stream(s) does a given option belong to.
A stream specifier is a string generally appended to the option name and separated from it by a colon.
E.g. "-codec:a:1 ac3" option contains "a:1" stream specifer, which matches the second audio stream.
Therefore it would select the ac3 codec for the second audio stream.
A stream specifier can match several stream, the option is then applied to all of them. E.g. the stream
specifier in "-b:a 128k" matches all audio streams.
An empty stream specifier matches all streams, for example "-codec copy" or "-codec: copy" would copy all
the streams without reencoding.
Possible forms of stream specifiers are:
stream_index
Matches the stream with this index. E.g. "-threads:1 4" would set the thread count for the second
stream to 4.
stream_type[:stream_index]
stream_type is one of: 'v' for video, 'a' for audio, 's' for subtitle, 'd' for data and 't' for
attachments. If stream_index is given, then matches stream number stream_index of this type.
Otherwise matches all streams of this type.
p:program_id[:stream_index]
If stream_index is given, then matches stream number stream_index in program with id program_id.
Otherwise matches all streams in this program.
Generic options
These options are shared amongst the av* tools.
-L Show license.
-h, -?, -help, --help [arg]
Show help. An optional parameter may be specified to print help about a specific item.
Possible values of arg are:
decoder=decoder_name
Print detailed information about the decoder named decoder_name. Use the -decoders option to get
a list of all decoders.
encoder=encoder_name
Print detailed information about the encoder named encoder_name. Use the -encoders option to get
a list of all encoders.
demuxer=demuxer_name
Print detailed information about the demuxer named demuxer_name. Use the -formats option to get a
list of all demuxers and muxers.
muxer=muxer_name
Print detailed information about the muxer named muxer_name. Use the -formats option to get a
list of all muxers and demuxers.
-version
Show version.
-formats
Show available formats.
The fields preceding the format names have the following meanings:
D Decoding available
E Encoding available
-codecs
Show all codecs known to libavcodec.
Note that the term 'codec' is used throughout this documentation as a shortcut for what is more
correctly called a media bitstream format.
-decoders
Show available decoders.
-encoders
Show all available encoders.
-bsfs
Show available bitstream filters.
-protocols
Show available protocols.
-filters
Show available libavfilter filters.
-pix_fmts
Show available pixel formats.
-sample_fmts
Show available sample formats.
-loglevel loglevel | -v loglevel
Set the logging level used by the library. loglevel is a number or a string containing one of the
following values:
quiet
panic
fatal
error
warning
info
verbose
debug
By default the program logs to stderr, if coloring is supported by the terminal, colors are used to
mark errors and warnings. Log coloring can be disabled setting the environment variable
AV_LOG_FORCE_NOCOLOR or NO_COLOR, or can be forced setting the environment variable
AV_LOG_FORCE_COLOR. The use of the environment variable NO_COLOR is deprecated and will be dropped
in a following Libav version.
AVOptions
These options are provided directly by the libavformat, libavdevice and libavcodec libraries. To see the
list of available AVOptions, use the -help option. They are separated into two categories:
generic
These options can be set for any container, codec or device. Generic options are listed under
AVFormatContext options for containers/devices and under AVCodecContext options for codecs.
private
These options are specific to the given container, device or codec. Private options are listed under
their corresponding containers/devices/codecs.
For example to write an ID3v2.3 header instead of a default ID3v2.4 to an MP3 file, use the id3v2_version
private option of the MP3 muxer:
avconv -i input.flac -id3v2_version 3 out.mp3
All codec AVOptions are obviously per-stream, so the chapter on stream specifiers applies to them
Note -nooption syntax cannot be used for boolean AVOptions, use -option 0/-option 1.
Note2 old undocumented way of specifying per-stream AVOptions by prepending v/a/s to the options name is
now obsolete and will be removed soon.
Codec AVOptions
-b[:stream_specifier] integer (output,audio,video)
set bitrate (in bits/s)
-bt[:stream_specifier] integer (output,video)
Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate tolerance specifies how far
ratecontrol is willing to deviate from the target average bitrate value. This is not related to
minimum/maximum bitrate. Lowering tolerance too much has an adverse effect on quality.
-flags[:stream_specifier] flags (input/output,audio,video)
Possible values:
mv4 use four motion vectors per macroblock (MPEG-4)
qpel
use 1/4-pel motion compensation
loop
use loop filter
qscale
use fixed qscale
gmc use gmc
mv0 always try a mb with mv=<0,0>
input_preserved
pass1
use internal 2-pass ratecontrol in first pass mode
pass2
use internal 2-pass ratecontrol in second pass mode
gray
only decode/encode grayscale
emu_edge
do not draw edges
psnr
error[?] variables will be set during encoding
truncated
naq normalize adaptive quantization
ildct
use interlaced DCT
low_delay
force low delay
global_header
place global headers in extradata instead of every keyframe
bitexact
use only bitexact functions (except (I)DCT)
aic H.263 advanced intra coding / MPEG-4 AC prediction
cbp Deprecated, use mpegvideo private options instead
qprd
Deprecated, use mpegvideo private options instead
ilme
interlaced motion estimation
cgop
closed GOP
-sub_id[:stream_specifier] integer ()
-me_method[:stream_specifier] integer (output,video)
set motion estimation method
Possible values:
zero
zero motion estimation (fastest)
full
full motion estimation (slowest)
epzs
EPZS motion estimation (default)
esa esa motion estimation (alias for full)
tesa
tesa motion estimation
dia diamond motion estimation (alias for EPZS)
log log motion estimation
phods
phods motion estimation
x1 X1 motion estimation
hex hex motion estimation
umh umh motion estimation
iter
iter motion estimation
-extradata_size[:stream_specifier] integer ()
-time_base[:stream_specifier] rational number ()
-g[:stream_specifier] integer (output,video)
set the group of picture (GOP) size
-ar[:stream_specifier] integer (input/output,audio)
set audio sampling rate (in Hz)
-ac[:stream_specifier] integer (input/output,audio)
set number of audio channels
-cutoff[:stream_specifier] integer (output,audio)
set cutoff bandwidth
-frame_size[:stream_specifier] integer (output,audio)
-frame_number[:stream_specifier] integer ()
-delay[:stream_specifier] integer ()
-qcomp[:stream_specifier] float (output,video)
video quantizer scale compression (VBR). Constant of ratecontrol equation. Recommended range for
default rc_eq: 0.0-1.0
-qblur[:stream_specifier] float (output,video)
video quantizer scale blur (VBR)
-qmin[:stream_specifier] integer (output,video)
minimum video quantizer scale (VBR)
-qmax[:stream_specifier] integer (output,video)
maximum video quantizer scale (VBR)
-qdiff[:stream_specifier] integer (output,video)
maximum difference between the quantizer scales (VBR)
-bf[:stream_specifier] integer (output,video)
use 'frames' B frames
-b_qfactor[:stream_specifier] float (output,video)
QP factor between P- and B-frames
-rc_strategy[:stream_specifier] integer (output,video)
ratecontrol method
-b_strategy[:stream_specifier] integer (output,video)
strategy to choose between I/P/B-frames
-ps[:stream_specifier] integer (output,video)
RTP payload size in bytes
-mv_bits[:stream_specifier] integer ()
-header_bits[:stream_specifier] integer ()
-i_tex_bits[:stream_specifier] integer ()
-p_tex_bits[:stream_specifier] integer ()
-i_count[:stream_specifier] integer ()
-p_count[:stream_specifier] integer ()
-skip_count[:stream_specifier] integer ()
-misc_bits[:stream_specifier] integer ()
-frame_bits[:stream_specifier] integer ()
-codec_tag[:stream_specifier] integer ()
-bug[:stream_specifier] flags (input,video)
work around not autodetected encoder bugs
Possible values:
autodetect
old_msmpeg4
some old lavc-generated MSMPEG4v3 files (no autodetection)
xvid_ilace
Xvid interlacing bug (autodetected if FOURCC == XVIX)
ump4
(autodetected if FOURCC == UMP4)
no_padding
padding bug (autodetected)
amv
ac_vlc
illegal VLC bug (autodetected per FOURCC)
qpel_chroma
std_qpel
old standard qpel (autodetected per FOURCC/version)
qpel_chroma2
direct_blocksize
direct-qpel-blocksize bug (autodetected per FOURCC/version)
edge
edge padding bug (autodetected per FOURCC/version)
hpel_chroma
dc_clip
ms work around various bugs in Microsoft's broken decoders
trunc
truncated frames
-lelim[:stream_specifier] integer (output,video)
single coefficient elimination threshold for luminance (negative values also consider DC coefficient)
-celim[:stream_specifier] integer (output,video)
single coefficient elimination threshold for chrominance (negative values also consider DC
coefficient)
-strict[:stream_specifier] integer (input/output,audio,video)
how strictly to follow the standards
Possible values:
very
strictly conform to a older more strict version of the spec or reference software
strict
strictly conform to all the things in the spec no matter what the consequences
normal
unofficial
allow unofficial extensions
experimental
allow non-standardized experimental things
-b_qoffset[:stream_specifier] float (output,video)
QP offset between P- and B-frames
-err_detect[:stream_specifier] flags (input,audio,video)
set error detection flags
Possible values:
crccheck
verify embedded CRCs
bitstream
detect bitstream specification deviations
buffer
detect improper bitstream length
explode
abort decoding on minor error detection
-has_b_frames[:stream_specifier] integer ()
-block_align[:stream_specifier] integer ()
-mpeg_quant[:stream_specifier] integer (output,video)
use MPEG quantizers instead of H.263
-qsquish[:stream_specifier] float (output,video)
how to keep quantizer between qmin and qmax (0 = clip, 1 = use differentiable function)
-rc_qmod_amp[:stream_specifier] float (output,video)
experimental quantizer modulation
-rc_qmod_freq[:stream_specifier] integer (output,video)
experimental quantizer modulation
-rc_override_count[:stream_specifier] integer ()
-rc_eq[:stream_specifier] string (output,video)
Set rate control equation. When computing the expression, besides the standard functions defined in
the section 'Expression Evaluation', the following functions are available: bits2qp(bits),
qp2bits(qp). Also the following constants are available: iTex pTex tex mv fCode iCount mcVar var isI
isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex avgTex.
-maxrate[:stream_specifier] integer (output,audio,video)
Set maximum bitrate tolerance (in bits/s). Requires bufsize to be set.
-minrate[:stream_specifier] integer (output,audio,video)
Set minimum bitrate tolerance (in bits/s). Most useful in setting up a CBR encode. It is of little
use otherwise.
-bufsize[:stream_specifier] integer (output,audio,video)
set ratecontrol buffer size (in bits)
-rc_buf_aggressivity[:stream_specifier] float (output,video)
currently useless
-i_qfactor[:stream_specifier] float (output,video)
QP factor between P- and I-frames
-i_qoffset[:stream_specifier] float (output,video)
QP offset between P- and I-frames
-rc_init_cplx[:stream_specifier] float (output,video)
initial complexity for 1-pass encoding
-dct[:stream_specifier] integer (output,video)
DCT algorithm
Possible values:
auto
autoselect a good one (default)
fastint
fast integer
int accurate integer
mmx
altivec
faan
floating point AAN DCT
-lumi_mask[:stream_specifier] float (output,video)
compresses bright areas stronger than medium ones
-tcplx_mask[:stream_specifier] float (output,video)
temporal complexity masking
-scplx_mask[:stream_specifier] float (output,video)
spatial complexity masking
-p_mask[:stream_specifier] float (output,video)
inter masking
-dark_mask[:stream_specifier] float (output,video)
compresses dark areas stronger than medium ones
-idct[:stream_specifier] integer (input/output,video)
select IDCT implementation
Possible values:
auto
int
simple
simplemmx
mmi
arm
altivec
sh4
simplearm
simplearmv5te
simplearmv6
simpleneon
simplealpha
h264
vp3
ipp
xvidmmx
faani
floating point AAN IDCT
-slice_count[:stream_specifier] integer ()
-ec[:stream_specifier] flags (input,video)
set error concealment strategy
Possible values:
guess_mvs
iterative motion vector (MV) search (slow)
deblock
use strong deblock filter for damaged MBs
-bits_per_coded_sample[:stream_specifier] integer ()
-pred[:stream_specifier] integer (output,video)
prediction method
Possible values:
left
plane
median
-aspect[:stream_specifier] rational number (output,video)
sample aspect ratio
-debug[:stream_specifier] flags (input/output,audio,video,subtitles)
print specific debug info
Possible values:
pict
picture info
rc rate control
bitstream
mb_type
macroblock (MB) type
qp per-block quantization parameter (QP)
mv motion vector
dct_coeff
skip
startcode
pts
er error recognition
mmco
memory management control operations (H.264)
bugs
vis_qp
visualize quantization parameter (QP), lower QP are tinted greener
vis_mb_type
visualize block types
buffers
picture buffer allocations
thread_ops
threading operations
-vismv[:stream_specifier] integer (input,video)
visualize motion vectors (MVs)
Possible values:
pf forward predicted MVs of P-frames
bf forward predicted MVs of B-frames
bb backward predicted MVs of B-frames
-cmp[:stream_specifier] integer (output,video)
full-pel ME compare function
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
dctmax
chroma
-subcmp[:stream_specifier] integer (output,video)
sub-pel ME compare function
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
dctmax
chroma
-mbcmp[:stream_specifier] integer (output,video)
macroblock compare function
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
dctmax
chroma
-ildctcmp[:stream_specifier] integer (output,video)
interlaced DCT compare function
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
dctmax
chroma
-dia_size[:stream_specifier] integer (output,video)
diamond type & size for motion estimation
-last_pred[:stream_specifier] integer (output,video)
amount of motion predictors from the previous frame
-preme[:stream_specifier] integer (output,video)
pre motion estimation
-precmp[:stream_specifier] integer (output,video)
pre motion estimation compare function
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
dctmax
chroma
-pre_dia_size[:stream_specifier] integer (output,video)
diamond type & size for motion estimation pre-pass
-subq[:stream_specifier] integer (output,video)
sub-pel motion estimation quality
-dtg_active_format[:stream_specifier] integer ()
-me_range[:stream_specifier] integer (output,video)
limit motion vectors range (1023 for DivX player)
-ibias[:stream_specifier] integer (output,video)
intra quant bias
-pbias[:stream_specifier] integer (output,video)
inter quant bias
-color_table_id[:stream_specifier] integer ()
-global_quality[:stream_specifier] integer (output,audio,video)
-coder[:stream_specifier] integer (output,video)
Possible values:
vlc variable length coder / Huffman coder
ac arithmetic coder
raw raw (no encoding)
rle run-length coder
deflate
deflate-based coder
-context[:stream_specifier] integer (output,video)
context model
-slice_flags[:stream_specifier] integer ()
-xvmc_acceleration[:stream_specifier] integer ()
-mbd[:stream_specifier] integer (output,video)
macroblock decision algorithm (high quality mode)
Possible values:
simple
use mbcmp (default)
bits
use fewest bits
rd use best rate distortion
-stream_codec_tag[:stream_specifier] integer ()
-sc_threshold[:stream_specifier] integer (output,video)
scene change threshold
-lmin[:stream_specifier] integer (output,video)
minimum Lagrange factor (VBR)
-lmax[:stream_specifier] integer (output,video)
maximum Lagrange factor (VBR)
-nr[:stream_specifier] integer (output,video)
noise reduction
-rc_init_occupancy[:stream_specifier] integer (output,video)
number of bits which should be loaded into the rc buffer before decoding starts
-inter_threshold[:stream_specifier] integer (output,video)
-flags2[:stream_specifier] flags (input/output,audio,video)
Possible values:
fast
allow non-spec-compliant speedup tricks
sgop
Deprecated, use mpegvideo private options instead
noout
skip bitstream encoding
local_header
place global headers at every keyframe instead of in extradata
skiprd
Deprecated, use mpegvideo private options instead
-error[:stream_specifier] integer (output,video)
-qns[:stream_specifier] integer (output,video)
deprecated, use mpegvideo private options instead
-threads[:stream_specifier] integer (input/output,video)
Possible values:
auto
autodetect a suitable number of threads to use
-me_threshold[:stream_specifier] integer (output,video)
motion estimation threshold
-mb_threshold[:stream_specifier] integer (output,video)
macroblock threshold
-dc[:stream_specifier] integer (output,video)
intra_dc_precision
-nssew[:stream_specifier] integer (output,video)
nsse weight
-skip_top[:stream_specifier] integer (input,video)
number of macroblock rows at the top which are skipped
-skip_bottom[:stream_specifier] integer (input,video)
number of macroblock rows at the bottom which are skipped
-profile[:stream_specifier] integer (output,audio,video)
Possible values:
unknown
aac_main
aac_low
aac_ssr
aac_ltp
aac_he
aac_he_v2
aac_ld
aac_eld
dts
dts_es
dts_96_24
dts_hd_hra
dts_hd_ma
-level[:stream_specifier] integer (output,audio,video)
Possible values:
unknown
-skip_threshold[:stream_specifier] integer (output,video)
frame skip threshold
-skip_factor[:stream_specifier] integer (output,video)
frame skip factor
-skip_exp[:stream_specifier] integer (output,video)
frame skip exponent
-skipcmp[:stream_specifier] integer (output,video)
frame skip compare function
Possible values:
sad sum of absolute differences, fast (default)
sse sum of squared errors
satd
sum of absolute Hadamard transformed differences
dct sum of absolute DCT transformed differences
psnr
sum of squared quantization errors (avoid, low quality)
bit number of bits needed for the block
rd rate distortion optimal, slow
zero
0
vsad
sum of absolute vertical differences
vsse
sum of squared vertical differences
nsse
noise preserving sum of squared differences
dctmax
chroma
-border_mask[:stream_specifier] float (output,video)
increase the quantizer for macroblocks close to borders
-mblmin[:stream_specifier] integer (output,video)
minimum macroblock Lagrange factor (VBR)
-mblmax[:stream_specifier] integer (output,video)
maximum macroblock Lagrange factor (VBR)
-mepc[:stream_specifier] integer (output,video)
motion estimation bitrate penalty compensation (1.0 = 256)
-skip_loop_filter[:stream_specifier] integer (input,video)
Possible values:
none
default
noref
bidir
nokey
all
-skip_idct[:stream_specifier] integer (input,video)
Possible values:
none
default
noref
bidir
nokey
all
-skip_frame[:stream_specifier] integer (input,video)
Possible values:
none
default
noref
bidir
nokey
all
-bidir_refine[:stream_specifier] integer (output,video)
refine the two motion vectors used in bidirectional macroblocks
-brd_scale[:stream_specifier] integer (output,video)
downscale frames for dynamic B-frame decision
-keyint_min[:stream_specifier] integer (output,video)
minimum interval between IDR-frames (x264)
-refs[:stream_specifier] integer (output,video)
reference frames to consider for motion compensation
-chromaoffset[:stream_specifier] integer (output,video)
chroma QP offset from luma
-trellis[:stream_specifier] integer (output,audio,video)
rate-distortion optimal quantization
-sc_factor[:stream_specifier] integer (output,video)
multiplied by qscale for each frame and added to scene_change_score
-mv0_threshold[:stream_specifier] integer (output,video)
-b_sensitivity[:stream_specifier] integer (output,video)
adjust sensitivity of b_frame_strategy 1
-compression_level[:stream_specifier] integer (output,audio,video)
-min_prediction_order[:stream_specifier] integer (output,audio)
-max_prediction_order[:stream_specifier] integer (output,audio)
-timecode_frame_start[:stream_specifier] integer (output,video)
GOP timecode frame start number, in non-drop-frame format
-request_channels[:stream_specifier] integer (input,audio)
set desired number of audio channels
-bits_per_raw_sample[:stream_specifier] integer ()
-channel_layout[:stream_specifier] integer (input/output,audio)
Possible values:
-request_channel_layout[:stream_specifier] integer (input,audio)
Possible values:
-rc_max_vbv_use[:stream_specifier] float (output,video)
-rc_min_vbv_use[:stream_specifier] float (output,video)
-ticks_per_frame[:stream_specifier] integer (input/output,audio,video)
-color_primaries[:stream_specifier] integer (input/output,video)
-color_trc[:stream_specifier] integer (input/output,video)
-colorspace[:stream_specifier] integer (input/output,video)
-color_range[:stream_specifier] integer (input/output,video)
-chroma_sample_location[:stream_specifier] integer (input/output,video)
-log_level_offset[:stream_specifier] integer ()
set the log level offset
-slices[:stream_specifier] integer (output,video)
number of slices, used in parallelized encoding
-thread_type[:stream_specifier] flags (input/output,video)
select multithreading type
Possible values:
slice
frame
-audio_service_type[:stream_specifier] integer (output,audio)
audio service type
Possible values:
ma Main Audio Service
ef Effects
vi Visually Impaired
hi Hearing Impaired
di Dialogue
co Commentary
em Emergency
vo Voice Over
ka Karaoke
-request_sample_fmt[:stream_specifier] integer (input,audio)
Possible values:
u8 8-bit unsigned integer
s16 16-bit signed integer
s32 32-bit signed integer
flt 32-bit float
dbl 64-bit double
u8p 8-bit unsigned integer planar
s16p
16-bit signed integer planar
s32p
32-bit signed integer planar
fltp
32-bit float planar
dblp
64-bit double planar
Format AVOptions
-probesize integer (input)
set probing size
-packetsize integer (output)
set packet size
-fflags flags (input/output)
Possible values:
ignidx
ignore index
genpts
generate pts
nofillin
do not fill in missing values that can be exactly calculated
noparse
disable AVParsers, this needs nofillin too
igndts
ignore dts
discardcorrupt
discard corrupted frames
nobuffer
reduce the latency introduced by optional buffering
-analyzeduration integer (input)
how many microseconds are analyzed to estimate duration
-cryptokey hexadecimal string (input)
decryption key
-indexmem integer (input)
max memory used for timestamp index (per stream)
-rtbufsize integer (input)
max memory used for buffering real-time frames
-fdebug flags (input/output)
print specific debug info
Possible values:
ts
-max_delay integer (input/output)
maximum muxing or demuxing delay in microseconds
-fpsprobesize integer (input)
number of frames used to probe fps
-f_err_detect flags (input)
set error detection flags (deprecated; use err_detect, save via avconv)
Possible values:
crccheck
verify embedded CRCs
bitstream
detect bitstream specification deviations
buffer
detect improper bitstream length
explode
abort decoding on minor error detection
-err_detect flags (input)
set error detection flags
Possible values:
crccheck
verify embedded CRCs
bitstream
detect bitstream specification deviations
buffer
detect improper bitstream length
explode
abort decoding on minor error detection
Main options
-f fmt (input/output)
Force input or output file format. The format is normally autodetected for input files and guessed
from file extension for output files, so this option is not needed in most cases.
-i filename (input)
input file name
-y (global)
Overwrite output files without asking.
-c[:stream_specifier] codec (input/output,per-stream)
-codec[:stream_specifier] codec (input/output,per-stream)
Select an encoder (when used before an output file) or a decoder (when used before an input file) for
one or more streams. codec is the name of a decoder/encoder or a special value "copy" (output only)
to indicate that the stream is not to be reencoded.
For example
avconv -i INPUT -map 0 -c:v libx264 -c:a copy OUTPUT
encodes all video streams with libx264 and copies all audio streams.
For each stream, the last matching "c" option is applied, so
avconv -i INPUT -map 0 -c copy -c:v:1 libx264 -c:a:137 libvorbis OUTPUT
will copy all the streams except the second video, which will be encoded with libx264, and the 138th
audio, which will be encoded with libvorbis.
-t duration (output)
Stop writing the output after its duration reaches duration. duration may be a number in seconds, or
in "hh:mm:ss[.xxx]" form.
-fs limit_size (output)
Set the file size limit.
-ss position (input/output)
When used as an input option (before "-i"), seeks in this input file to position. When used as an
output option (before an output filename), decodes but discards input until the timestamps reach
position. This is slower, but more accurate.
position may be either in seconds or in "hh:mm:ss[.xxx]" form.
-itsoffset offset (input)
Set the input time offset in seconds. "[-]hh:mm:ss[.xxx]" syntax is also supported. The offset is
added to the timestamps of the input files. Specifying a positive offset means that the
corresponding streams are delayed by offset seconds.
-metadata[:metadata_specifier] key=value (output,per-metadata)
Set a metadata key/value pair.
An optional metadata_specifier may be given to set metadata on streams or chapters. See
"-map_metadata" documentation for details.
This option overrides metadata set with "-map_metadata". It is also possible to delete metadata by
using an empty value.
For example, for setting the title in the output file:
avconv -i in.avi -metadata title="my title" out.flv
To set the language of the first audio stream:
avconv -i INPUT -metadata:s:a:0 language=eng OUTPUT
-target type (output)
Specify target file type ("vcd", "svcd", "dvd", "dv", "dv50"). type may be prefixed with "pal-",
"ntsc-" or "film-" to use the corresponding standard. All the format options (bitrate, codecs, buffer
sizes) are then set automatically. You can just type:
avconv -i myfile.avi -target vcd /tmp/vcd.mpg
Nevertheless you can specify additional options as long as you know they do not conflict with the
standard, as in:
avconv -i myfile.avi -target vcd -bf 2 /tmp/vcd.mpg
-dframes number (output)
Set the number of data frames to record. This is an alias for "-frames:d".
-frames[:stream_specifier] framecount (output,per-stream)
Stop writing to the stream after framecount frames.
-q[:stream_specifier] q (output,per-stream)
-qscale[:stream_specifier] q (output,per-stream)
Use fixed quality scale (VBR). The meaning of q is codec-dependent.
-filter[:stream_specifier] filter_graph (output,per-stream)
filter_graph is a description of the filter graph to apply to the stream. Use "-filters" to show all
the available filters (including also sources and sinks).
See also the -filter_complex option if you want to create filter graphs with multiple inputs and/or
outputs.
-pre[:stream_specifier] preset_name (output,per-stream)
Specify the preset for matching stream(s).
-stats (global)
Print encoding progress/statistics. On by default.
-attach filename (output)
Add an attachment to the output file. This is supported by a few formats like Matroska for e.g. fonts
used in rendering subtitles. Attachments are implemented as a specific type of stream, so this option
will add a new stream to the file. It is then possible to use per-stream options on this stream in
the usual way. Attachment streams created with this option will be created after all the other
streams (i.e. those created with "-map" or automatic mappings).
Note that for Matroska you also have to set the mimetype metadata tag:
avconv -i INPUT -attach DejaVuSans.ttf -metadata:s:2 mimetype=application/x-truetype-font out.mkv
(assuming that the attachment stream will be third in the output file).
-dump_attachment[:stream_specifier] filename (input,per-stream)
Extract the matching attachment stream into a file named filename. If filename is empty, then the
value of the "filename" metadata tag will be used.
E.g. to extract the first attachment to a file named 'out.ttf':
avconv -dump_attachment:t:0 out.ttf INPUT
To extract all attachments to files determined by the "filename" tag:
avconv -dump_attachment:t "" INPUT
Technical note -- attachments are implemented as codec extradata, so this option can actually be used
to extract extradata from any stream, not just attachments.
Video Options
-vframes number (output)
Set the number of video frames to record. This is an alias for "-frames:v".
-r[:stream_specifier] fps (input/output,per-stream)
Set frame rate (Hz value, fraction or abbreviation).
As an input option, ignore any timestamps stored in the file and instead generate timestamps assuming
constant frame rate fps.
As an output option, duplicate or drop input frames to achieve constant output frame rate fps (note
that this actually causes the "fps" filter to be inserted to the end of the corresponding
filtergraph).
-s[:stream_specifier] size (input/output,per-stream)
Set frame size.
As an input option, this is a shortcut for the video_size private option, recognized by some demuxers
for which the frame size is either not stored in the file or is configurable -- e.g. raw video or
video grabbers.
As an output option, this inserts the "scale" video filter to the end of the corresponding
filtergraph. Please use the "scale" filter directly to insert it at the beginning or some other
place.
The format is wxh (default - same as source). The following abbreviations are recognized:
sqcif
128x96
qcif
176x144
cif 352x288
4cif
704x576
16cif
1408x1152
qqvga
160x120
qvga
320x240
vga 640x480
svga
800x600
xga 1024x768
uxga
1600x1200
qxga
2048x1536
sxga
1280x1024
qsxga
2560x2048
hsxga
5120x4096
wvga
852x480
wxga
1366x768
wsxga
1600x1024
wuxga
1920x1200
woxga
2560x1600
wqsxga
3200x2048
wquxga
3840x2400
whsxga
6400x4096
whuxga
7680x4800
cga 320x200
ega 640x350
hd480
852x480
hd720
1280x720
hd1080
1920x1080
-aspect[:stream_specifier] aspect (output,per-stream)
Set the video display aspect ratio specified by aspect.
aspect can be a floating point number string, or a string of the form num:den, where num and den are
the numerator and denominator of the aspect ratio. For example "4:3", "16:9", "1.3333", and "1.7777"
are valid argument values.
-vn (output)
Disable video recording.
-vcodec codec (output)
Set the video codec. This is an alias for "-codec:v".
-pass[:stream_specifier] n (output,per-stream)
Select the pass number (1 or 2). It is used to do two-pass video encoding. The statistics of the
video are recorded in the first pass into a log file (see also the option -passlogfile), and in the
second pass that log file is used to generate the video at the exact requested bitrate. On pass 1,
you may just deactivate audio and set output to null, examples for Windows and Unix:
avconv -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y NUL
avconv -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y /dev/null
-passlogfile[:stream_specifier] prefix (output,per-stream)
Set two-pass log file name prefix to prefix, the default file name prefix is ``av2pass''. The
complete file name will be PREFIX-N.log, where N is a number specific to the output stream.
-vf filter_graph (output)
filter_graph is a description of the filter graph to apply to the input video. Use the option
"-filters" to show all the available filters (including also sources and sinks). This is an alias
for "-filter:v".
Advanced Video Options
-pix_fmt[:stream_specifier] format (input/output,per-stream)
Set pixel format. Use "-pix_fmts" to show all the supported pixel formats.
-sws_flags flags (input/output)
Set SwScaler flags.
-vdt n
Discard threshold.
-rc_override[:stream_specifier] override (output,per-stream)
rate control override for specific intervals
-deinterlace
Deinterlace pictures. This option is deprecated since the deinterlacing is very low quality. Use
the yadif filter with "-filter:v yadif".
-vstats
Dump video coding statistics to vstats_HHMMSS.log.
-vstats_file file
Dump video coding statistics to file.
-top[:stream_specifier] n (output,per-stream)
top=1/bottom=0/auto=-1 field first
-dc precision
Intra_dc_precision.
-vtag fourcc/tag (output)
Force video tag/fourcc. This is an alias for "-tag:v".
-qphist (global)
Show QP histogram.
-force_key_frames[:stream_specifier] time[,time...] (output,per-stream)
Force key frames at the specified timestamps, more precisely at the first frames after each specified
time. This option can be useful to ensure that a seek point is present at a chapter mark or any
other designated place in the output file. The timestamps must be specified in ascending order.
-copyinkf[:stream_specifier] (output,per-stream)
When doing stream copy, copy also non-key frames found at the beginning.
Audio Options
-aframes number (output)
Set the number of audio frames to record. This is an alias for "-frames:a".
-ar[:stream_specifier] freq (input/output,per-stream)
Set the audio sampling frequency. For output streams it is set by default to the frequency of the
corresponding input stream. For input streams this option only makes sense for audio grabbing devices
and raw demuxers and is mapped to the corresponding demuxer options.
-aq q (output)
Set the audio quality (codec-specific, VBR). This is an alias for -q:a.
-ac[:stream_specifier] channels (input/output,per-stream)
Set the number of audio channels. For output streams it is set by default to the number of input
audio channels. For input streams this option only makes sense for audio grabbing devices and raw
demuxers and is mapped to the corresponding demuxer options.
-an (output)
Disable audio recording.
-acodec codec (input/output)
Set the audio codec. This is an alias for "-codec:a".
-sample_fmt[:stream_specifier] sample_fmt (output,per-stream)
Set the audio sample format. Use "-sample_fmts" to get a list of supported sample formats.
-af filter_graph (output)
filter_graph is a description of the filter graph to apply to the input audio. Use the option
"-filters" to show all the available filters (including also sources and sinks). This is an alias
for "-filter:a".
Advanced Audio options:
-atag fourcc/tag (output)
Force audio tag/fourcc. This is an alias for "-tag:a".
Subtitle options:
-scodec codec (input/output)
Set the subtitle codec. This is an alias for "-codec:s".
-sn (output)
Disable subtitle recording.
Advanced options
-map [-]input_file_id[:stream_specifier][,sync_file_id[:stream_specifier]] | [linklabel] (output)
Designate one or more input streams as a source for the output file. Each input stream is identified
by the input file index input_file_id and the input stream index input_stream_id within the input
file. Both indices start at 0. If specified, sync_file_id:stream_specifier sets which input stream is
used as a presentation sync reference.
The first "-map" option on the command line specifies the source for output stream 0, the second
"-map" option specifies the source for output stream 1, etc.
A "-" character before the stream identifier creates a "negative" mapping. It disables matching
streams from already created mappings.
An alternative [linklabel] form will map outputs from complex filter graphs (see the -filter_complex
option) to the output file. linklabel must correspond to a defined output link label in the graph.
For example, to map ALL streams from the first input file to output
avconv -i INPUT -map 0 output
For example, if you have two audio streams in the first input file, these streams are identified by
"0:0" and "0:1". You can use "-map" to select which streams to place in an output file. For example:
avconv -i INPUT -map 0:1 out.wav
will map the input stream in INPUT identified by "0:1" to the (single) output stream in out.wav.
For example, to select the stream with index 2 from input file a.mov (specified by the identifier
"0:2"), and stream with index 6 from input b.mov (specified by the identifier "1:6"), and copy them
to the output file out.mov:
avconv -i a.mov -i b.mov -c copy -map 0:2 -map 1:6 out.mov
To select all video and the third audio stream from an input file:
avconv -i INPUT -map 0:v -map 0:a:2 OUTPUT
To map all the streams except the second audio, use negative mappings
avconv -i INPUT -map 0 -map -0:a:1 OUTPUT
Note that using this option disables the default mappings for this output file.
-map_metadata[:metadata_spec_out] infile[:metadata_spec_in] (output,per-metadata)
Set metadata information of the next output file from infile. Note that those are file indices (zero-
based), not filenames. Optional metadata_spec_in/out parameters specify, which metadata to copy. A
metadata specifier can have the following forms:
g global metadata, i.e. metadata that applies to the whole file
s[:stream_spec]
per-stream metadata. stream_spec is a stream specifier as described in the Stream specifiers
chapter. In an input metadata specifier, the first matching stream is copied from. In an output
metadata specifier, all matching streams are copied to.
c:chapter_index
per-chapter metadata. chapter_index is the zero-based chapter index.
p:program_index
per-program metadata. program_index is the zero-based program index.
If metadata specifier is omitted, it defaults to global.
By default, global metadata is copied from the first input file, per-stream and per-chapter metadata
is copied along with streams/chapters. These default mappings are disabled by creating any mapping of
the relevant type. A negative file index can be used to create a dummy mapping that just disables
automatic copying.
For example to copy metadata from the first stream of the input file to global metadata of the output
file:
avconv -i in.ogg -map_metadata 0:s:0 out.mp3
To do the reverse, i.e. copy global metadata to all audio streams:
avconv -i in.mkv -map_metadata:s:a 0:g out.mkv
Note that simple 0 would work as well in this example, since global metadata is assumed by default.
-map_chapters input_file_index (output)
Copy chapters from input file with index input_file_index to the next output file. If no chapter
mapping is specified, then chapters are copied from the first input file with at least one chapter.
Use a negative file index to disable any chapter copying.
-debug
Print specific debug info.
-benchmark (global)
Show benchmarking information at the end of an encode. Shows CPU time used and maximum memory
consumption. Maximum memory consumption is not supported on all systems, it will usually display as
0 if not supported.
-timelimit duration (global)
Exit after avconv has been running for duration seconds.
-dump (global)
Dump each input packet to stderr.
-hex (global)
When dumping packets, also dump the payload.
-re (input)
Read input at native frame rate. Mainly used to simulate a grab device.
-vsync parameter
Video sync method.
passthrough
Each frame is passed with its timestamp from the demuxer to the muxer.
cfr Frames will be duplicated and dropped to achieve exactly the requested constant framerate.
vfr Frames are passed through with their timestamp or dropped so as to prevent 2 frames from having
the same timestamp.
auto
Chooses between 1 and 2 depending on muxer capabilities. This is the default method.
With -map you can select from which stream the timestamps should be taken. You can leave either video
or audio unchanged and sync the remaining stream(s) to the unchanged one.
-async samples_per_second
Audio sync method. "Stretches/squeezes" the audio stream to match the timestamps, the parameter is
the maximum samples per second by which the audio is changed. -async 1 is a special case where only
the start of the audio stream is corrected without any later correction. This option has been
deprecated. Use the "asyncts" audio filter instead.
-copyts
Copy timestamps from input to output.
-copytb
Copy input stream time base from input to output when stream copying.
-shortest (output)
Finish encoding when the shortest input stream ends.
-dts_delta_threshold
Timestamp discontinuity delta threshold.
-muxdelay seconds (input)
Set the maximum demux-decode delay.
-muxpreload seconds (input)
Set the initial demux-decode delay.
-streamid output-stream-index:new-value (output)
Assign a new stream-id value to an output stream. This option should be specified prior to the output
filename to which it applies. For the situation where multiple output files exist, a streamid may be
reassigned to a different value.
For example, to set the stream 0 PID to 33 and the stream 1 PID to 36 for an output mpegts file:
avconv -i infile -streamid 0:33 -streamid 1:36 out.ts
-bsf[:stream_specifier] bitstream_filters (output,per-stream)
Set bitstream filters for matching streams. bistream_filters is a comma-separated list of bitstream
filters. Use the "-bsfs" option to get the list of bitstream filters.
avconv -i h264.mp4 -c:v copy -bsf:v h264_mp4toannexb -an out.h264
avconv -i file.mov -an -vn -bsf:s mov2textsub -c:s copy -f rawvideo sub.txt
-tag[:stream_specifier] codec_tag (output,per-stream)
Force a tag/fourcc for matching streams.
-cpuflags mask (global)
Set a mask that's applied to autodetected CPU flags. This option is intended for testing. Do not use
it unless you know what you're doing.
-filter_complex filtergraph (global)
Define a complex filter graph, i.e. one with arbitrary number of inputs and/or outputs. For simple
graphs -- those with one input and one output of the same type -- see the -filter options.
filtergraph is a description of the filter graph, as described in Filtergraph syntax.
Input link labels must refer to input streams using the "[file_index:stream_specifier]" syntax (i.e.
the same as -map uses). If stream_specifier matches multiple streams, the first one will be used. An
unlabeled input will be connected to the first unused input stream of the matching type.
Output link labels are referred to with -map. Unlabeled outputs are added to the first output file.
Note that with this option it is possible to use only lavfi sources without normal input files.
For example, to overlay an image over video
avconv -i video.mkv -i image.png -filter_complex '[0:v][1:v]overlay[out]' -map
'[out]' out.mkv
Here "[0:v]" refers to the first video stream in the first input file, which is linked to the first
(main) input of the overlay filter. Similarly the first video stream in the second input is linked to
the second (overlay) input of overlay.
Assuming there is only one video stream in each input file, we can omit input labels, so the above is
equivalent to
avconv -i video.mkv -i image.png -filter_complex 'overlay[out]' -map
'[out]' out.mkv
Furthermore we can omit the output label and the single output from the filter graph will be added to
the output file automatically, so we can simply write
avconv -i video.mkv -i image.png -filter_complex 'overlay' out.mkv
To generate 5 seconds of pure red video using lavfi "color" source:
avconv -filter_complex 'color=red' -t 5 out.mkv
TIPS
• For streaming at very low bitrate application, use a low frame rate and a small GOP size. This is
especially true for RealVideo where the Linux player does not seem to be very fast, so it can miss
frames. An example is:
avconv -g 3 -r 3 -t 10 -b 50k -s qcif -f rv10 /tmp/b.rm
• The parameter 'q' which is displayed while encoding is the current quantizer. The value 1 indicates
that a very good quality could be achieved. The value 31 indicates the worst quality. If q=31 appears
too often, it means that the encoder cannot compress enough to meet your bitrate. You must either
increase the bitrate, decrease the frame rate or decrease the frame size.
• If your computer is not fast enough, you can speed up the compression at the expense of the
compression ratio. You can use '-me zero' to speed up motion estimation, and '-g 0' to disable motion
estimation completely (you have only I-frames, which means it is about as good as JPEG compression).
• To have very low audio bitrates, reduce the sampling frequency (down to 22050 Hz for MPEG audio,
22050 or 11025 for AC-3).
• To have a constant quality (but a variable bitrate), use the option '-qscale n' when 'n' is between 1
(excellent quality) and 31 (worst quality).
EXAMPLES
Preset files
A preset file contains a sequence of option=value pairs, one for each line, specifying a sequence of
options which can be specified also on the command line. Lines starting with the hash ('#') character are
ignored and are used to provide comments. Empty lines are also ignored. Check the presets directory in
the Libav source tree for examples.
Preset files are specified with the "pre" option, this option takes a preset name as input. Avconv
searches for a file named preset_name.avpreset in the directories $AVCONV_DATADIR (if set), and
$HOME/.avconv, and in the data directory defined at configuration time (usually $PREFIX/share/avconv) in
that order. For example, if the argument is "libx264-max", it will search for the file
libx264-max.avpreset.
Video and Audio grabbing
If you specify the input format and device then avconv can grab video and audio directly.
avconv -f oss -i /dev/dsp -f video4linux2 -i /dev/video0 /tmp/out.mpg
Note that you must activate the right video source and channel before launching avconv with any TV viewer
such as
xawtv ("http://linux.bytesex.org/xawtv/") by Gerd Knorr. You also have to set the audio recording levels
correctly with a standard mixer.
X11 grabbing
Grab the X11 display with avconv via
avconv -f x11grab -s cif -r 25 -i :0.0 /tmp/out.mpg
0.0 is display.screen number of your X11 server, same as the DISPLAY environment variable.
avconv -f x11grab -s cif -r 25 -i :0.0+10,20 /tmp/out.mpg
0.0 is display.screen number of your X11 server, same as the DISPLAY environment variable. 10 is the
x-offset and 20 the y-offset for the grabbing.
Video and Audio file format conversion
Any supported file format and protocol can serve as input to avconv:
Examples:
• You can use YUV files as input:
avconv -i /tmp/test%d.Y /tmp/out.mpg
It will use the files:
/tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
/tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
The Y files use twice the resolution of the U and V files. They are raw files, without header. They
can be generated by all decent video decoders. You must specify the size of the image with the -s
option if avconv cannot guess it.
• You can input from a raw YUV420P file:
avconv -i /tmp/test.yuv /tmp/out.avi
test.yuv is a file containing raw YUV planar data. Each frame is composed of the Y plane followed by
the U and V planes at half vertical and horizontal resolution.
• You can output to a raw YUV420P file:
avconv -i mydivx.avi hugefile.yuv
• You can set several input files and output files:
avconv -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg
Converts the audio file a.wav and the raw YUV video file a.yuv to MPEG file a.mpg.
• You can also do audio and video conversions at the same time:
avconv -i /tmp/a.wav -ar 22050 /tmp/a.mp2
Converts a.wav to MPEG audio at 22050 Hz sample rate.
• You can encode to several formats at the same time and define a mapping from input stream to output
streams:
avconv -i /tmp/a.wav -map 0:a -b 64k /tmp/a.mp2 -map 0:a -b 128k /tmp/b.mp2
Converts a.wav to a.mp2 at 64 kbits and to b.mp2 at 128 kbits. '-map file:index' specifies which
input stream is used for each output stream, in the order of the definition of output streams.
• You can transcode decrypted VOBs:
avconv -i snatch_1.vob -f avi -c:v mpeg4 -b:v 800k -g 300 -bf 2 -c:a libmp3lame -b:a 128k snatch.avi
This is a typical DVD ripping example; the input is a VOB file, the output an AVI file with MPEG-4
video and MP3 audio. Note that in this command we use B-frames so the MPEG-4 stream is DivX5
compatible, and GOP size is 300 which means one intra frame every 10 seconds for 29.97fps input
video. Furthermore, the audio stream is MP3-encoded so you need to enable LAME support by passing
"--enable-libmp3lame" to configure. The mapping is particularly useful for DVD transcoding to get
the desired audio language.
NOTE: To see the supported input formats, use "avconv -formats".
• You can extract images from a video, or create a video from many images:
For extracting images from a video:
avconv -i foo.avi -r 1 -s WxH -f image2 foo-%03d.jpeg
This will extract one video frame per second from the video and will output them in files named
foo-001.jpeg, foo-002.jpeg, etc. Images will be rescaled to fit the new WxH values.
If you want to extract just a limited number of frames, you can use the above command in combination
with the -vframes or -t option, or in combination with -ss to start extracting from a certain point
in time.
For creating a video from many images:
avconv -f image2 -i foo-%03d.jpeg -r 12 -s WxH foo.avi
The syntax "foo-%03d.jpeg" specifies to use a decimal number composed of three digits padded with
zeroes to express the sequence number. It is the same syntax supported by the C printf function, but
only formats accepting a normal integer are suitable.
• You can put many streams of the same type in the output:
avconv -i test1.avi -i test2.avi -map 1:1 -map 1:0 -map 0:1 -map 0:0 -c copy -y test12.nut
The resulting output file test12.nut will contain the first four streams from the input files in
reverse order.
• To force CBR video output:
avconv -i myfile.avi -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k out.m2v
• The four options lmin, lmax, mblmin and mblmax use 'lambda' units, but you may use the QP2LAMBDA
constant to easily convert from 'q' units:
avconv -i src.ext -lmax 21*QP2LAMBDA dst.ext
EXPRESSION EVALUATION
When evaluating an arithmetic expression, Libav uses an internal formula evaluator, implemented through
the libavutil/eval.h interface.
An expression may contain unary, binary operators, constants, and functions.
Two expressions expr1 and expr2 can be combined to form another expression "expr1;expr2". expr1 and
expr2 are evaluated in turn, and the new expression evaluates to the value of expr2.
The following binary operators are available: "+", "-", "*", "/", "^".
The following unary operators are available: "+", "-".
The following functions are available:
sinh(x)
cosh(x)
tanh(x)
sin(x)
cos(x)
tan(x)
atan(x)
asin(x)
acos(x)
exp(x)
log(x)
abs(x)
squish(x)
gauss(x)
isinf(x)
Return 1.0 if x is +/-INFINITY, 0.0 otherwise.
isnan(x)
Return 1.0 if x is NAN, 0.0 otherwise.
mod(x, y)
max(x, y)
min(x, y)
eq(x, y)
gte(x, y)
gt(x, y)
lte(x, y)
lt(x, y)
st(var, expr)
Allow to store the value of the expression expr in an internal variable. var specifies the number of
the variable where to store the value, and it is a value ranging from 0 to 9. The function returns
the value stored in the internal variable.
ld(var)
Allow to load the value of the internal variable with number var, which was previously stored with
st(var, expr). The function returns the loaded value.
while(cond, expr)
Evaluate expression expr while the expression cond is non-zero, and returns the value of the last
expr evaluation, or NAN if cond was always false.
ceil(expr)
Round the value of expression expr upwards to the nearest integer. For example, "ceil(1.5)" is "2.0".
floor(expr)
Round the value of expression expr downwards to the nearest integer. For example, "floor(-1.5)" is
"-2.0".
trunc(expr)
Round the value of expression expr towards zero to the nearest integer. For example, "trunc(-1.5)" is
"-1.0".
sqrt(expr)
Compute the square root of expr. This is equivalent to "(expr)^.5".
not(expr)
Return 1.0 if expr is zero, 0.0 otherwise.
Note that:
"*" works like AND
"+" works like OR
thus
if A then B else C
is equivalent to
A*B + not(A)*C
In your C code, you can extend the list of unary and binary functions, and define recognized constants,
so that they are available for your expressions.
The evaluator also recognizes the International System number postfixes. If 'i' is appended after the
postfix, powers of 2 are used instead of powers of 10. The 'B' postfix multiplies the value for 8, and
can be appended after another postfix or used alone. This allows using for example 'KB', 'MiB', 'G' and
'B' as postfix.
Follows the list of available International System postfixes, with indication of the corresponding powers
of 10 and of 2.
y -24 / -80
z -21 / -70
a -18 / -60
f -15 / -50
p -12 / -40
n -9 / -30
u -6 / -20
m -3 / -10
c -2
d -1
h 2
k 3 / 10
K 3 / 10
M 6 / 20
G 9 / 30
T 12 / 40
P 15 / 40
E 18 / 50
Z 21 / 60
Y 24 / 70
ENCODERS
Encoders are configured elements in Libav which allow the encoding of multimedia streams.
When you configure your Libav build, all the supported native encoders are enabled by default. Encoders
requiring an external library must be enabled manually via the corresponding "--enable-lib" option. You
can list all available encoders using the configure option "--list-encoders".
You can disable all the encoders with the configure option "--disable-encoders" and selectively enable /
disable single encoders with the options "--enable-encoder=ENCODER" / "--disable-encoder=ENCODER".
The option "-codecs" of the av* tools will display the list of enabled encoders.
AUDIO ENCODERS
A description of some of the currently available audio encoders follows.
ac3 and ac3_fixed
AC-3 audio encoders.
These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as the undocumented
RealAudio 3 (a.k.a. dnet).
The ac3 encoder uses floating-point math, while the ac3_fixed encoder only uses fixed-point integer math.
This does not mean that one is always faster, just that one or the other may be better suited to a
particular system. The floating-point encoder will generally produce better quality audio for a given
bitrate. The ac3_fixed encoder is not the default codec for any of the output formats, so it must be
specified explicitly using the option "-acodec ac3_fixed" in order to use it.
AC-3 Metadata
The AC-3 metadata options are used to set parameters that describe the audio, but in most cases do not
affect the audio encoding itself. Some of the options do directly affect or influence the decoding and
playback of the resulting bitstream, while others are just for informational purposes. A few of the
options will add bits to the output stream that could otherwise be used for audio data, and will thus
affect the quality of the output. Those will be indicated accordingly with a note in the option list
below.
These parameters are described in detail in several publicly-available documents.
*<A/52:2010 - Digital Audio Compression (AC-3) (E-AC-3) Standard
("http://www.atsc.org/cms/standards/a_52-2010.pdf")>
*<A/54 - Guide to the Use of the ATSC Digital Television Standard
("http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf")>
*<Dolby Metadata Guide
("http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/18_Metadata.Guide.pdf")>
*<Dolby Digital Professional Encoding Guidelines
("http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/46_DDEncodingGuidelines.pdf")>
Metadata Control Options
-per_frame_metadata boolean
Allow Per-Frame Metadata. Specifies if the encoder should check for changing metadata for each frame.
0 The metadata values set at initialization will be used for every frame in the stream. (default)
1 Metadata values can be changed before encoding each frame.
Downmix Levels
-center_mixlev level
Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing
to stereo. This field will only be written to the bitstream if a center channel is present. The value
is specified as a scale factor. There are 3 valid values:
0.707
Apply -3dB gain
0.595
Apply -4.5dB gain (default)
0.500
Apply -6dB gain
-surround_mixlev level
Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when
downmixing to stereo. This field will only be written to the bitstream if one or more surround
channels are present. The value is specified as a scale factor. There are 3 valid values:
0.707
Apply -3dB gain
0.500
Apply -6dB gain (default)
0.000
Silence Surround Channel(s)
Audio Production Information
Audio Production Information is optional information describing the mixing environment. Either none or
both of the fields are written to the bitstream.
-mixing_level number
Mixing Level. Specifies peak sound pressure level (SPL) in the production environment when the mix
was mastered. Valid values are 80 to 111, or -1 for unknown or not indicated. The default value is
-1, but that value cannot be used if the Audio Production Information is written to the bitstream.
Therefore, if the "room_type" option is not the default value, the "mixing_level" option must not be
-1.
-room_type type
Room Type. Describes the equalization used during the final mixing session at the studio or on the
dubbing stage. A large room is a dubbing stage with the industry standard X-curve equalization; a
small room has flat equalization. This field will not be written to the bitstream if both the
"mixing_level" option and the "room_type" option have the default values.
0
notindicated
Not Indicated (default)
1
large
Large Room
2
small
Small Room
Other Metadata Options
-copyright boolean
Copyright Indicator. Specifies whether a copyright exists for this audio.
0
off No Copyright Exists (default)
1
on Copyright Exists
-dialnorm value
Dialogue Normalization. Indicates how far the average dialogue level of the program is below digital
100% full scale (0 dBFS). This parameter determines a level shift during audio reproduction that sets
the average volume of the dialogue to a preset level. The goal is to match volume level between
program sources. A value of -31dB will result in no volume level change, relative to the source
volume, during audio reproduction. Valid values are whole numbers in the range -31 to -1, with -31
being the default.
-dsur_mode mode
Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround (Pro Logic). This field
will only be written to the bitstream if the audio stream is stereo. Using this option does NOT mean
the encoder will actually apply Dolby Surround processing.
0
notindicated
Not Indicated (default)
1
off Not Dolby Surround Encoded
2
on Dolby Surround Encoded
-original boolean
Original Bit Stream Indicator. Specifies whether this audio is from the original source and not a
copy.
0
off Not Original Source
1
on Original Source (default)
Extended Bitstream Information
The extended bitstream options are part of the Alternate Bit Stream Syntax as specified in Annex D of the
A/52:2010 standard. It is grouped into 2 parts. If any one parameter in a group is specified, all values
in that group will be written to the bitstream. Default values are used for those that are written but
have not been specified. If the mixing levels are written, the decoder will use these values instead of
the ones specified in the "center_mixlev" and "surround_mixlev" options if it supports the Alternate Bit
Stream Syntax.
Extended Bitstream Information - Part 1
-dmix_mode mode
Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt (Dolby Surround) or Lo/Ro
(normal stereo) as the preferred stereo downmix mode.
0
notindicated
Not Indicated (default)
1
ltrt
Lt/Rt Downmix Preferred
2
loro
Lo/Ro Downmix Preferred
-ltrt_cmixlev level
Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the center channel when
downmixing to stereo in Lt/Rt mode.
1.414
Apply +3dB gain
1.189
Apply +1.5dB gain
1.000
Apply 0dB gain
0.841
Apply -1.5dB gain
0.707
Apply -3.0dB gain
0.595
Apply -4.5dB gain (default)
0.500
Apply -6.0dB gain
0.000
Silence Center Channel
-ltrt_surmixlev level
Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when
downmixing to stereo in Lt/Rt mode.
0.841
Apply -1.5dB gain
0.707
Apply -3.0dB gain
0.595
Apply -4.5dB gain
0.500
Apply -6.0dB gain (default)
0.000
Silence Surround Channel(s)
-loro_cmixlev level
Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the center channel when
downmixing to stereo in Lo/Ro mode.
1.414
Apply +3dB gain
1.189
Apply +1.5dB gain
1.000
Apply 0dB gain
0.841
Apply -1.5dB gain
0.707
Apply -3.0dB gain
0.595
Apply -4.5dB gain (default)
0.500
Apply -6.0dB gain
0.000
Silence Center Channel
-loro_surmixlev level
Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when
downmixing to stereo in Lo/Ro mode.
0.841
Apply -1.5dB gain
0.707
Apply -3.0dB gain
0.595
Apply -4.5dB gain
0.500
Apply -6.0dB gain (default)
0.000
Silence Surround Channel(s)
Extended Bitstream Information - Part 2
-dsurex_mode mode
Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX (7.1 matrixed to 5.1).
Using this option does NOT mean the encoder will actually apply Dolby Surround EX processing.
0
notindicated
Not Indicated (default)
1
on Dolby Surround EX Off
2
off Dolby Surround EX On
-dheadphone_mode mode
Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone encoding (multi-channel
matrixed to 2.0 for use with headphones). Using this option does NOT mean the encoder will actually
apply Dolby Headphone processing.
0
notindicated
Not Indicated (default)
1
on Dolby Headphone Off
2
off Dolby Headphone On
-ad_conv_type type
A/D Converter Type. Indicates whether the audio has passed through HDCD A/D conversion.
0
standard
Standard A/D Converter (default)
1
hdcd
HDCD A/D Converter
Other AC-3 Encoding Options
-stereo_rematrixing boolean
Stereo Rematrixing. Enables/Disables use of rematrixing for stereo input. This is an optional AC-3
feature that increases quality by selectively encoding the left/right channels as mid/side. This
option is enabled by default, and it is highly recommended that it be left as enabled except for
testing purposes.
Floating-Point-Only AC-3 Encoding Options
These options are only valid for the floating-point encoder and do not exist for the fixed-point encoder
due to the corresponding features not being implemented in fixed-point.
-channel_coupling boolean
Enables/Disables use of channel coupling, which is an optional AC-3 feature that increases quality by
combining high frequency information from multiple channels into a single channel. The per-channel
high frequency information is sent with less accuracy in both the frequency and time domains. This
allows more bits to be used for lower frequencies while preserving enough information to reconstruct
the high frequencies. This option is enabled by default for the floating-point encoder and should
generally be left as enabled except for testing purposes or to increase encoding speed.
-1
auto
Selected by Encoder (default)
0
off Disable Channel Coupling
1
on Enable Channel Coupling
-cpl_start_band number
Coupling Start Band. Sets the channel coupling start band, from 1 to 15. If a value higher than the
bandwidth is used, it will be reduced to 1 less than the coupling end band. If auto is used, the
start band will be determined by the encoder based on the bit rate, sample rate, and channel layout.
This option has no effect if channel coupling is disabled.
-1
auto
Selected by Encoder (default)
DEMUXERS
Demuxers are configured elements in Libav which allow to read the multimedia streams from a particular
type of file.
When you configure your Libav build, all the supported demuxers are enabled by default. You can list all
available ones using the configure option "--list-demuxers".
You can disable all the demuxers using the configure option "--disable-demuxers", and selectively enable
a single demuxer with the option "--enable-demuxer=DEMUXER", or disable it with the option
"--disable-demuxer=DEMUXER".
The option "-formats" of the av* tools will display the list of enabled demuxers.
The description of some of the currently available demuxers follows.
image2
Image file demuxer.
This demuxer reads from a list of image files specified by a pattern.
The pattern may contain the string "%d" or "%0Nd", which specifies the position of the characters
representing a sequential number in each filename matched by the pattern. If the form "%d0Nd" is used,
the string representing the number in each filename is 0-padded and N is the total number of 0-padded
digits representing the number. The literal character '%' can be specified in the pattern with the string
"%%".
If the pattern contains "%d" or "%0Nd", the first filename of the file list specified by the pattern must
contain a number inclusively contained between 0 and 4, all the following numbers must be sequential.
This limitation may be hopefully fixed.
The pattern may contain a suffix which is used to automatically determine the format of the images
contained in the files.
For example the pattern "img-%03d.bmp" will match a sequence of filenames of the form img-001.bmp,
img-002.bmp, ..., img-010.bmp, etc.; the pattern "i%%m%%g-%d.jpg" will match a sequence of filenames of
the form i%m%g-1.jpg, i%m%g-2.jpg, ..., i%m%g-10.jpg, etc.
The size, the pixel format, and the format of each image must be the same for all the files in the
sequence.
The following example shows how to use avconv for creating a video from the images in the file sequence
img-001.jpeg, img-002.jpeg, ..., assuming an input framerate of 10 frames per second:
avconv -i 'img-%03d.jpeg' -r 10 out.mkv
Note that the pattern must not necessarily contain "%d" or "%0Nd", for example to convert a single image
file img.jpeg you can employ the command:
avconv -i img.jpeg img.png
-pixel_format format
Set the pixel format (for raw image)
-video_size size
Set the frame size (for raw image)
-framerate rate
Set the frame rate
-loop bool
Loop over the images
-start_number start
Specify the first number in the sequence
applehttp
Apple HTTP Live Streaming demuxer.
This demuxer presents all AVStreams from all variant streams. The id field is set to the bitrate variant
index number. By setting the discard flags on AVStreams (by pressing 'a' or 'v' in avplay), the caller
can decide which variant streams to actually receive. The total bitrate of the variant that the stream
belongs to is available in a metadata key named "variant_bitrate".
MUXERS
Muxers are configured elements in Libav which allow writing multimedia streams to a particular type of
file.
When you configure your Libav build, all the supported muxers are enabled by default. You can list all
available muxers using the configure option "--list-muxers".
You can disable all the muxers with the configure option "--disable-muxers" and selectively enable /
disable single muxers with the options "--enable-muxer=MUXER" / "--disable-muxer=MUXER".
The option "-formats" of the av* tools will display the list of enabled muxers.
A description of some of the currently available muxers follows.
crc
CRC (Cyclic Redundancy Check) testing format.
This muxer computes and prints the Adler-32 CRC of all the input audio and video frames. By default audio
frames are converted to signed 16-bit raw audio and video frames to raw video before computing the CRC.
The output of the muxer consists of a single line of the form: CRC=0xCRC, where CRC is a hexadecimal
number 0-padded to 8 digits containing the CRC for all the decoded input frames.
For example to compute the CRC of the input, and store it in the file out.crc:
avconv -i INPUT -f crc out.crc
You can print the CRC to stdout with the command:
avconv -i INPUT -f crc -
You can select the output format of each frame with avconv by specifying the audio and video codec and
format. For example to compute the CRC of the input audio converted to PCM unsigned 8-bit and the input
video converted to MPEG-2 video, use the command:
avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f crc -
See also the framecrc muxer.
framecrc
Per-frame CRC (Cyclic Redundancy Check) testing format.
This muxer computes and prints the Adler-32 CRC for each decoded audio and video frame. By default audio
frames are converted to signed 16-bit raw audio and video frames to raw video before computing the CRC.
The output of the muxer consists of a line for each audio and video frame of the form: stream_index,
frame_dts, frame_size, 0xCRC, where CRC is a hexadecimal number 0-padded to 8 digits containing the CRC
of the decoded frame.
For example to compute the CRC of each decoded frame in the input, and store it in the file out.crc:
avconv -i INPUT -f framecrc out.crc
You can print the CRC of each decoded frame to stdout with the command:
avconv -i INPUT -f framecrc -
You can select the output format of each frame with avconv by specifying the audio and video codec and
format. For example, to compute the CRC of each decoded input audio frame converted to PCM unsigned 8-bit
and of each decoded input video frame converted to MPEG-2 video, use the command:
avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f framecrc -
See also the crc muxer.
hls
Apple HTTP Live Streaming muxer that segments MPEG-TS according to the HTTP Live Streaming specification.
It creates a playlist file and numbered segment files. The output filename specifies the playlist
filename; the segment filenames receive the same basename as the playlist, a sequential number and a .ts
extension.
avconv -i in.nut out.m3u8
-hls_time seconds
Set the segment length in seconds.
-hls_list_size size
Set the maximum number of playlist entries.
-hls_wrap wrap
Set the number after which index wraps.
-start_number number
Start the sequence from number.
image2
Image file muxer.
The image file muxer writes video frames to image files.
The output filenames are specified by a pattern, which can be used to produce sequentially numbered
series of files. The pattern may contain the string "%d" or "%0Nd", this string specifies the position
of the characters representing a numbering in the filenames. If the form "%0Nd" is used, the string
representing the number in each filename is 0-padded to N digits. The literal character '%' can be
specified in the pattern with the string "%%".
If the pattern contains "%d" or "%0Nd", the first filename of the file list specified will contain the
number 1, all the following numbers will be sequential.
The pattern may contain a suffix which is used to automatically determine the format of the image files
to write.
For example the pattern "img-%03d.bmp" will specify a sequence of filenames of the form img-001.bmp,
img-002.bmp, ..., img-010.bmp, etc. The pattern "img%%-%d.jpg" will specify a sequence of filenames of
the form img%-1.jpg, img%-2.jpg, ..., img%-10.jpg, etc.
The following example shows how to use avconv for creating a sequence of files img-001.jpeg,
img-002.jpeg, ..., taking one image every second from the input video:
avconv -i in.avi -vsync 1 -r 1 -f image2 'img-%03d.jpeg'
Note that with avconv, if the format is not specified with the "-f" option and the output filename
specifies an image file format, the image2 muxer is automatically selected, so the previous command can
be written as:
avconv -i in.avi -vsync 1 -r 1 'img-%03d.jpeg'
Note also that the pattern must not necessarily contain "%d" or "%0Nd", for example to create a single
image file img.jpeg from the input video you can employ the command:
avconv -i in.avi -f image2 -frames:v 1 img.jpeg
-start_number number
Start the sequence from number.
MOV/MP4/ISMV
The mov/mp4/ismv muxer supports fragmentation. Normally, a MOV/MP4 file has all the metadata about all
packets stored in one location (written at the end of the file, it can be moved to the start for better
playback using the qt-faststart tool). A fragmented file consists of a number of fragments, where packets
and metadata about these packets are stored together. Writing a fragmented file has the advantage that
the file is decodable even if the writing is interrupted (while a normal MOV/MP4 is undecodable if it is
not properly finished), and it requires less memory when writing very long files (since writing normal
MOV/MP4 files stores info about every single packet in memory until the file is closed). The downside is
that it is less compatible with other applications.
Fragmentation is enabled by setting one of the AVOptions that define how to cut the file into fragments:
-movflags frag_keyframe
Start a new fragment at each video keyframe.
-frag_duration duration
Create fragments that are duration microseconds long.
-frag_size size
Create fragments that contain up to size bytes of payload data.
-movflags frag_custom
Allow the caller to manually choose when to cut fragments, by calling "av_write_frame(ctx, NULL)" to
write a fragment with the packets written so far. (This is only useful with other applications
integrating libavformat, not from avconv.)
-min_frag_duration duration
Don't create fragments that are shorter than duration microseconds long.
If more than one condition is specified, fragments are cut when one of the specified conditions is
fulfilled. The exception to this is "-min_frag_duration", which has to be fulfilled for any of the other
conditions to apply.
Additionally, the way the output file is written can be adjusted through a few other options:
-movflags empty_moov
Write an initial moov atom directly at the start of the file, without describing any samples in it.
Generally, an mdat/moov pair is written at the start of the file, as a normal MOV/MP4 file,
containing only a short portion of the file. With this option set, there is no initial mdat atom, and
the moov atom only describes the tracks but has a zero duration.
Files written with this option set do not work in QuickTime. This option is implicitly set when
writing ismv (Smooth Streaming) files.
-movflags separate_moof
Write a separate moof (movie fragment) atom for each track. Normally, packets for all tracks are
written in a moof atom (which is slightly more efficient), but with this option set, the muxer writes
one moof/mdat pair for each track, making it easier to separate tracks.
This option is implicitly set when writing ismv (Smooth Streaming) files.
Smooth Streaming content can be pushed in real time to a publishing point on IIS with this muxer.
Example:
avconv -re <<normal input/transcoding options>> -movflags isml+frag_keyframe -f ismv http://server/publishingpoint.isml/Streams(Encoder1)
mpegts
MPEG transport stream muxer.
This muxer implements ISO 13818-1 and part of ETSI EN 300 468.
The muxer options are:
-mpegts_original_network_id number
Set the original_network_id (default 0x0001). This is unique identifier of a network in DVB. Its main
use is in the unique identification of a service through the path Original_Network_ID,
Transport_Stream_ID.
-mpegts_transport_stream_id number
Set the transport_stream_id (default 0x0001). This identifies a transponder in DVB.
-mpegts_service_id number
Set the service_id (default 0x0001) also known as program in DVB.
-mpegts_pmt_start_pid number
Set the first PID for PMT (default 0x1000, max 0x1f00).
-mpegts_start_pid number
Set the first PID for data packets (default 0x0100, max 0x0f00).
The recognized metadata settings in mpegts muxer are "service_provider" and "service_name". If they are
not set the default for "service_provider" is "Libav" and the default for "service_name" is "Service01".
avconv -i file.mpg -c copy \
-mpegts_original_network_id 0x1122 \
-mpegts_transport_stream_id 0x3344 \
-mpegts_service_id 0x5566 \
-mpegts_pmt_start_pid 0x1500 \
-mpegts_start_pid 0x150 \
-metadata service_provider="Some provider" \
-metadata service_name="Some Channel" \
-y out.ts
null
Null muxer.
This muxer does not generate any output file, it is mainly useful for testing or benchmarking purposes.
For example to benchmark decoding with avconv you can use the command:
avconv -benchmark -i INPUT -f null out.null
Note that the above command does not read or write the out.null file, but specifying the output file is
required by the avconv syntax.
Alternatively you can write the command as:
avconv -benchmark -i INPUT -f null -
matroska
Matroska container muxer.
This muxer implements the matroska and webm container specs.
The recognized metadata settings in this muxer are:
title=title name
Name provided to a single track
language=language name
Specifies the language of the track in the Matroska languages form
STEREO_MODE=mode
Stereo 3D video layout of two views in a single video track
mono
video is not stereo
left_right
Both views are arranged side by side, Left-eye view is on the left
bottom_top
Both views are arranged in top-bottom orientation, Left-eye view is at bottom
top_bottom
Both views are arranged in top-bottom orientation, Left-eye view is on top
checkerboard_rl
Each view is arranged in a checkerboard interleaved pattern, Left-eye view being first
checkerboard_lr
Each view is arranged in a checkerboard interleaved pattern, Right-eye view being first
row_interleaved_rl
Each view is constituted by a row based interleaving, Right-eye view is first row
row_interleaved_lr
Each view is constituted by a row based interleaving, Left-eye view is first row
col_interleaved_rl
Both views are arranged in a column based interleaving manner, Right-eye view is first column
col_interleaved_lr
Both views are arranged in a column based interleaving manner, Left-eye view is first column
anaglyph_cyan_red
All frames are in anaglyph format viewable through red-cyan filters
right_left
Both views are arranged side by side, Right-eye view is on the left
anaglyph_green_magenta
All frames are in anaglyph format viewable through green-magenta filters
block_lr
Both eyes laced in one Block, Left-eye view is first
block_rl
Both eyes laced in one Block, Right-eye view is first
For example a 3D WebM clip can be created using the following command line:
avconv -i sample_left_right_clip.mpg -an -c:v libvpx -metadata STEREO_MODE=left_right -y stereo_clip.webm
segment
Basic stream segmenter.
The segmenter muxer outputs streams to a number of separate files of nearly fixed duration. Output
filename pattern can be set in a fashion similar to image2.
Every segment starts with a video keyframe, if a video stream is present. The segment muxer works best
with a single constant frame rate video.
Optionally it can generate a flat list of the created segments, one segment per line.
segment_format format
Override the inner container format, by default it is guessed by the filename extension.
segment_time t
Set segment duration to t seconds.
segment_list name
Generate also a listfile named name.
segment_list_size size
Overwrite the listfile once it reaches size entries.
segment_wrap limit
Wrap around segment index once it reaches limit.
avconv -i in.mkv -c copy -map 0 -f segment -list out.list out%03d.nut
mp3
The MP3 muxer writes a raw MP3 stream with an ID3v2 header at the beginning and optionally an ID3v1 tag
at the end. ID3v2.3 and ID3v2.4 are supported, the "id3v2_version" option controls which one is used. The
legacy ID3v1 tag is not written by default, but may be enabled with the "write_id3v1" option.
For seekable output the muxer also writes a Xing frame at the beginning, which contains the number of
frames in the file. It is useful for computing duration of VBR files.
The muxer supports writing ID3v2 attached pictures (APIC frames). The pictures are supplied to the muxer
in form of a video stream with a single packet. There can be any number of those streams, each will
correspond to a single APIC frame. The stream metadata tags title and comment map to APIC description
and picture type respectively. See <http://id3.org/id3v2.4.0-frames> for allowed picture types.
Note that the APIC frames must be written at the beginning, so the muxer will buffer the audio frames
until it gets all the pictures. It is therefore advised to provide the pictures as soon as possible to
avoid excessive buffering.
Examples:
Write an mp3 with an ID3v2.3 header and an ID3v1 footer:
avconv -i INPUT -id3v2_version 3 -write_id3v1 1 out.mp3
Attach a picture to an mp3:
avconv -i input.mp3 -i cover.png -c copy -metadata:s:v title="Album cover"
-metadata:s:v comment="Cover (Front)" out.mp3
INPUT DEVICES
Input devices are configured elements in Libav which allow to access the data coming from a multimedia
device attached to your system.
When you configure your Libav build, all the supported input devices are enabled by default. You can list
all available ones using the configure option "--list-indevs".
You can disable all the input devices using the configure option "--disable-indevs", and selectively
enable an input device using the option "--enable-indev=INDEV", or you can disable a particular input
device using the option "--disable-indev=INDEV".
The option "-formats" of the av* tools will display the list of supported input devices (amongst the
demuxers).
A description of the currently available input devices follows.
alsa
ALSA (Advanced Linux Sound Architecture) input device.
To enable this input device during configuration you need libasound installed on your system.
This device allows capturing from an ALSA device. The name of the device to capture has to be an ALSA
card identifier.
An ALSA identifier has the syntax:
hw:<CARD>[,<DEV>[,<SUBDEV>]]
where the DEV and SUBDEV components are optional.
The three arguments (in order: CARD,DEV,SUBDEV) specify card number or identifier, device number and
subdevice number (-1 means any).
To see the list of cards currently recognized by your system check the files /proc/asound/cards and
/proc/asound/devices.
For example to capture with avconv from an ALSA device with card id 0, you may run the command:
avconv -f alsa -i hw:0 alsaout.wav
For more information see: <http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html>
bktr
BSD video input device.
dv1394
Linux DV 1394 input device.
fbdev
Linux framebuffer input device.
The Linux framebuffer is a graphic hardware-independent abstraction layer to show graphics on a computer
monitor, typically on the console. It is accessed through a file device node, usually /dev/fb0.
For more detailed information read the file Documentation/fb/framebuffer.txt included in the Linux source
tree.
To record from the framebuffer device /dev/fb0 with avconv:
avconv -f fbdev -r 10 -i /dev/fb0 out.avi
You can take a single screenshot image with the command:
avconv -f fbdev -frames:v 1 -r 1 -i /dev/fb0 screenshot.jpeg
See also <http://linux-fbdev.sourceforge.net/>, and fbset(1).
jack
JACK input device.
To enable this input device during configuration you need libjack installed on your system.
A JACK input device creates one or more JACK writable clients, one for each audio channel, with name
client_name:input_N, where client_name is the name provided by the application, and N is a number which
identifies the channel. Each writable client will send the acquired data to the Libav input device.
Once you have created one or more JACK readable clients, you need to connect them to one or more JACK
writable clients.
To connect or disconnect JACK clients you can use the jack_connect and jack_disconnect programs, or do it
through a graphical interface, for example with qjackctl.
To list the JACK clients and their properties you can invoke the command jack_lsp.
Follows an example which shows how to capture a JACK readable client with avconv.
# Create a JACK writable client with name "libav".
$ avconv -f jack -i libav -y out.wav
# Start the sample jack_metro readable client.
$ jack_metro -b 120 -d 0.2 -f 4000
# List the current JACK clients.
$ jack_lsp -c
system:capture_1
system:capture_2
system:playback_1
system:playback_2
libav:input_1
metro:120_bpm
# Connect metro to the avconv writable client.
$ jack_connect metro:120_bpm libav:input_1
For more information read: <http://jackaudio.org/>
libdc1394
IIDC1394 input device, based on libdc1394 and libraw1394.
oss
Open Sound System input device.
The filename to provide to the input device is the device node representing the OSS input device, and is
usually set to /dev/dsp.
For example to grab from /dev/dsp using avconv use the command:
avconv -f oss -i /dev/dsp /tmp/oss.wav
For more information about OSS see: <http://manuals.opensound.com/usersguide/dsp.html>
pulse
pulseaudio input device.
To enable this input device during configuration you need libpulse-simple installed in your system.
The filename to provide to the input device is a source device or the string "default"
To list the pulse source devices and their properties you can invoke the command pactl list sources.
avconv -f pulse -i default /tmp/pulse.wav
server AVOption
The syntax is:
-server <server name>
Connects to a specific server.
name AVOption
The syntax is:
-name <application name>
Specify the application name pulse will use when showing active clients, by default it is "libav"
stream_name AVOption
The syntax is:
-stream_name <stream name>
Specify the stream name pulse will use when showing active streams, by default it is "record"
sample_rate AVOption
The syntax is:
-sample_rate <samplerate>
Specify the samplerate in Hz, by default 48kHz is used.
channels AVOption
The syntax is:
-channels <N>
Specify the channels in use, by default 2 (stereo) is set.
frame_size AVOption
The syntax is:
-frame_size <bytes>
Specify the number of byte per frame, by default it is set to 1024.
fragment_size AVOption
The syntax is:
-fragment_size <bytes>
Specify the minimal buffering fragment in pulseaudio, it will affect the audio latency. By default it is
unset.
sndio
sndio input device.
To enable this input device during configuration you need libsndio installed on your system.
The filename to provide to the input device is the device node representing the sndio input device, and
is usually set to /dev/audio0.
For example to grab from /dev/audio0 using avconv use the command:
avconv -f sndio -i /dev/audio0 /tmp/oss.wav
video4linux2
Video4Linux2 input video device.
The name of the device to grab is a file device node, usually Linux systems tend to automatically create
such nodes when the device (e.g. an USB webcam) is plugged into the system, and has a name of the kind
/dev/videoN, where N is a number associated to the device.
Video4Linux2 devices usually support a limited set of widthxheight sizes and framerates. You can check
which are supported using -list_formats all for Video4Linux2 devices.
Some usage examples of the video4linux2 devices with avconv and avplay:
# Grab and show the input of a video4linux2 device.
avplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0
# Grab and record the input of a video4linux2 device, leave the
framerate and size as previously set.
avconv -f video4linux2 -input_format mjpeg -i /dev/video0 out.mpeg
vfwcap
VfW (Video for Windows) capture input device.
The filename passed as input is the capture driver number, ranging from 0 to 9. You may use "list" as
filename to print a list of drivers. Any other filename will be interpreted as device number 0.
x11grab
X11 video input device.
This device allows to capture a region of an X11 display.
The filename passed as input has the syntax:
[<hostname>]:<display_number>.<screen_number>[+<x_offset>,<y_offset>]
hostname:display_number.screen_number specifies the X11 display name of the screen to grab from. hostname
can be omitted, and defaults to "localhost". The environment variable DISPLAY contains the default
display name.
x_offset and y_offset specify the offsets of the grabbed area with respect to the top-left border of the
X11 screen. They default to 0.
Check the X11 documentation (e.g. man X) for more detailed information.
Use the dpyinfo program for getting basic information about the properties of your X11 display (e.g. grep
for "name" or "dimensions").
For example to grab from :0.0 using avconv:
avconv -f x11grab -r 25 -s cif -i :0.0 out.mpg
# Grab at position 10,20.
avconv -f x11grab -r 25 -s cif -i :0.0+10,20 out.mpg
follow_mouse AVOption
The syntax is:
-follow_mouse centered|<PIXELS>
When it is specified with "centered", the grabbing region follows the mouse pointer and keeps the pointer
at the center of region; otherwise, the region follows only when the mouse pointer reaches within PIXELS
(greater than zero) to the edge of region.
For example:
avconv -f x11grab -follow_mouse centered -r 25 -s cif -i :0.0 out.mpg
# Follows only when the mouse pointer reaches within 100 pixels to edge
avconv -f x11grab -follow_mouse 100 -r 25 -s cif -i :0.0 out.mpg
show_region AVOption
The syntax is:
-show_region 1
If show_region AVOption is specified with 1, then the grabbing region will be indicated on screen. With
this option, it's easy to know what is being grabbed if only a portion of the screen is grabbed.
For example:
avconv -f x11grab -show_region 1 -r 25 -s cif -i :0.0+10,20 out.mpg
# With follow_mouse
avconv -f x11grab -follow_mouse centered -show_region 1 -r 25 -s cif -i :0.0 out.mpg
OUTPUT DEVICES
Output devices are configured elements in Libav which allow to write multimedia data to an output device
attached to your system.
When you configure your Libav build, all the supported output devices are enabled by default. You can
list all available ones using the configure option "--list-outdevs".
You can disable all the output devices using the configure option "--disable-outdevs", and selectively
enable an output device using the option "--enable-outdev=OUTDEV", or you can disable a particular input
device using the option "--disable-outdev=OUTDEV".
The option "-formats" of the av* tools will display the list of enabled output devices (amongst the
muxers).
A description of the currently available output devices follows.
alsa
ALSA (Advanced Linux Sound Architecture) output device.
oss
OSS (Open Sound System) output device.
sndio
sndio audio output device.
PROTOCOLS
Protocols are configured elements in Libav which allow to access resources which require the use of a
particular protocol.
When you configure your Libav build, all the supported protocols are enabled by default. You can list all
available ones using the configure option "--list-protocols".
You can disable all the protocols using the configure option "--disable-protocols", and selectively
enable a protocol using the option "--enable-protocol=PROTOCOL", or you can disable a particular protocol
using the option "--disable-protocol=PROTOCOL".
The option "-protocols" of the av* tools will display the list of supported protocols.
A description of the currently available protocols follows.
concat
Physical concatenation protocol.
Allow to read and seek from many resource in sequence as if they were a unique resource.
A URL accepted by this protocol has the syntax:
concat:<URL1>|<URL2>|...|<URLN>
where URL1, URL2, ..., URLN are the urls of the resource to be concatenated, each one possibly specifying
a distinct protocol.
For example to read a sequence of files split1.mpeg, split2.mpeg, split3.mpeg with avplay use the
command:
avplay concat:split1.mpeg\|split2.mpeg\|split3.mpeg
Note that you may need to escape the character "|" which is special for many shells.
file
File access protocol.
Allow to read from or read to a file.
For example to read from a file input.mpeg with avconv use the command:
avconv -i file:input.mpeg output.mpeg
The av* tools default to the file protocol, that is a resource specified with the name "FILE.mpeg" is
interpreted as the URL "file:FILE.mpeg".
gopher
Gopher protocol.
hls
Read Apple HTTP Live Streaming compliant segmented stream as a uniform one. The M3U8 playlists describing
the segments can be remote HTTP resources or local files, accessed using the standard file protocol. The
nested protocol is declared by specifying "+proto" after the hls URI scheme name, where proto is either
"file" or "http".
hls+http://host/path/to/remote/resource.m3u8
hls+file://path/to/local/resource.m3u8
Using this protocol is discouraged - the hls demuxer should work just as well (if not, please report the
issues) and is more complete. To use the hls demuxer instead, simply use the direct URLs to the m3u8
files.
http
HTTP (Hyper Text Transfer Protocol).
mmst
MMS (Microsoft Media Server) protocol over TCP.
mmsh
MMS (Microsoft Media Server) protocol over HTTP.
The required syntax is:
mmsh://<server>[:<port>][/<app>][/<playpath>]
md5
MD5 output protocol.
Computes the MD5 hash of the data to be written, and on close writes this to the designated output or
stdout if none is specified. It can be used to test muxers without writing an actual file.
Some examples follow.
# Write the MD5 hash of the encoded AVI file to the file output.avi.md5.
avconv -i input.flv -f avi -y md5:output.avi.md5
# Write the MD5 hash of the encoded AVI file to stdout.
avconv -i input.flv -f avi -y md5:
Note that some formats (typically MOV) require the output protocol to be seekable, so they will fail with
the MD5 output protocol.
pipe
UNIX pipe access protocol.
Allow to read and write from UNIX pipes.
The accepted syntax is:
pipe:[<number>]
number is the number corresponding to the file descriptor of the pipe (e.g. 0 for stdin, 1 for stdout, 2
for stderr). If number is not specified, by default the stdout file descriptor will be used for writing,
stdin for reading.
For example to read from stdin with avconv:
cat test.wav | avconv -i pipe:0
# ...this is the same as...
cat test.wav | avconv -i pipe:
For writing to stdout with avconv:
avconv -i test.wav -f avi pipe:1 | cat > test.avi
# ...this is the same as...
avconv -i test.wav -f avi pipe: | cat > test.avi
Note that some formats (typically MOV), require the output protocol to be seekable, so they will fail
with the pipe output protocol.
rtmp
Real-Time Messaging Protocol.
The Real-Time Messaging Protocol (RTMP) is used for streaming multimedia content across a TCP/IP network.
The required syntax is:
rtmp://<server>[:<port>][/<app>][/<instance>][/<playpath>]
The accepted parameters are:
server
The address of the RTMP server.
port
The number of the TCP port to use (by default is 1935).
app It is the name of the application to access. It usually corresponds to the path where the application
is installed on the RTMP server (e.g. /ondemand/, /flash/live/, etc.). You can override the value
parsed from the URI through the "rtmp_app" option, too.
playpath
It is the path or name of the resource to play with reference to the application specified in app,
may be prefixed by "mp4:". You can override the value parsed from the URI through the "rtmp_playpath"
option, too.
listen
Act as a server, listening for an incoming connection.
timeout
Maximum time to wait for the incoming connection. Implies listen.
Additionally, the following parameters can be set via command line options (or in code via "AVOption"s):
rtmp_app
Name of application to connect on the RTMP server. This option overrides the parameter specified in
the URI.
rtmp_buffer
Set the client buffer time in milliseconds. The default is 3000.
rtmp_conn
Extra arbitrary AMF connection parameters, parsed from a string, e.g. like "B:1 S:authMe O:1
NN:code:1.23 NS:flag:ok O:0". Each value is prefixed by a single character denoting the type, B for
Boolean, N for number, S for string, O for object, or Z for null, followed by a colon. For Booleans
the data must be either 0 or 1 for FALSE or TRUE, respectively. Likewise for Objects the data must
be 0 or 1 to end or begin an object, respectively. Data items in subobjects may be named, by
prefixing the type with 'N' and specifying the name before the value (i.e. "NB:myFlag:1"). This
option may be used multiple times to construct arbitrary AMF sequences.
rtmp_flashver
Version of the Flash plugin used to run the SWF player. The default is LNX 9,0,124,2.
rtmp_flush_interval
Number of packets flushed in the same request (RTMPT only). The default is 10.
rtmp_live
Specify that the media is a live stream. No resuming or seeking in live streams is possible. The
default value is "any", which means the subscriber first tries to play the live stream specified in
the playpath. If a live stream of that name is not found, it plays the recorded stream. The other
possible values are "live" and "recorded".
rtmp_pageurl
URL of the web page in which the media was embedded. By default no value will be sent.
rtmp_playpath
Stream identifier to play or to publish. This option overrides the parameter specified in the URI.
rtmp_subscribe
Name of live stream to subscribe to. By default no value will be sent. It is only sent if the option
is specified or if rtmp_live is set to live.
rtmp_swfhash
SHA256 hash of the decompressed SWF file (32 bytes).
rtmp_swfsize
Size of the decompressed SWF file, required for SWFVerification.
rtmp_swfurl
URL of the SWF player for the media. By default no value will be sent.
rtmp_swfverify
URL to player swf file, compute hash/size automatically.
rtmp_tcurl
URL of the target stream. Defaults to proto://host[:port]/app.
For example to read with avplay a multimedia resource named "sample" from the application "vod" from an
RTMP server "myserver":
avplay rtmp://myserver/vod/sample
rtmpe
Encrypted Real-Time Messaging Protocol.
The Encrypted Real-Time Messaging Protocol (RTMPE) is used for streaming multimedia content within
standard cryptographic primitives, consisting of Diffie-Hellman key exchange and HMACSHA256, generating a
pair of RC4 keys.
rtmps
Real-Time Messaging Protocol over a secure SSL connection.
The Real-Time Messaging Protocol (RTMPS) is used for streaming multimedia content across an encrypted
connection.
rtmpt
Real-Time Messaging Protocol tunneled through HTTP.
The Real-Time Messaging Protocol tunneled through HTTP (RTMPT) is used for streaming multimedia content
within HTTP requests to traverse firewalls.
rtmpte
Encrypted Real-Time Messaging Protocol tunneled through HTTP.
The Encrypted Real-Time Messaging Protocol tunneled through HTTP (RTMPTE) is used for streaming
multimedia content within HTTP requests to traverse firewalls.
rtmpts
Real-Time Messaging Protocol tunneled through HTTPS.
The Real-Time Messaging Protocol tunneled through HTTPS (RTMPTS) is used for streaming multimedia content
within HTTPS requests to traverse firewalls.
rtmp, rtmpe, rtmps, rtmpt, rtmpte
Real-Time Messaging Protocol and its variants supported through librtmp.
Requires the presence of the librtmp headers and library during configuration. You need to explicitly
configure the build with "--enable-librtmp". If enabled this will replace the native RTMP protocol.
This protocol provides most client functions and a few server functions needed to support RTMP, RTMP
tunneled in HTTP (RTMPT), encrypted RTMP (RTMPE), RTMP over SSL/TLS (RTMPS) and tunneled variants of
these encrypted types (RTMPTE, RTMPTS).
The required syntax is:
<rtmp_proto>://<server>[:<port>][/<app>][/<playpath>] <options>
where rtmp_proto is one of the strings "rtmp", "rtmpt", "rtmpe", "rtmps", "rtmpte", "rtmpts"
corresponding to each RTMP variant, and server, port, app and playpath have the same meaning as specified
for the RTMP native protocol. options contains a list of space-separated options of the form key=val.
See the librtmp manual page (man 3 librtmp) for more information.
For example, to stream a file in real-time to an RTMP server using avconv:
avconv -re -i myfile -f flv rtmp://myserver/live/mystream
To play the same stream using avplay:
avplay "rtmp://myserver/live/mystream live=1"
rtp
Real-Time Protocol.
rtsp
RTSP is not technically a protocol handler in libavformat, it is a demuxer and muxer. The demuxer
supports both normal RTSP (with data transferred over RTP; this is used by e.g. Apple and Microsoft) and
Real-RTSP (with data transferred over RDT).
The muxer can be used to send a stream using RTSP ANNOUNCE to a server supporting it (currently Darwin
Streaming Server and Mischa Spiegelmock's
RTSP server ("http://github.com/revmischa/rtsp-server")).
The required syntax for a RTSP url is:
rtsp://<hostname>[:<port>]/<path>
The following options (set on the avconv/avplay command line, or set in code via "AVOption"s or in
"avformat_open_input"), are supported:
Flags for "rtsp_transport":
udp Use UDP as lower transport protocol.
tcp Use TCP (interleaving within the RTSP control channel) as lower transport protocol.
udp_multicast
Use UDP multicast as lower transport protocol.
http
Use HTTP tunneling as lower transport protocol, which is useful for passing proxies.
Multiple lower transport protocols may be specified, in that case they are tried one at a time (if the
setup of one fails, the next one is tried). For the muxer, only the "tcp" and "udp" options are
supported.
Flags for "rtsp_flags":
filter_src
Accept packets only from negotiated peer address and port.
listen
Act as a server, listening for an incoming connection.
When receiving data over UDP, the demuxer tries to reorder received packets (since they may arrive out of
order, or packets may get lost totally). This can be disabled by setting the maximum demuxing delay to
zero (via the "max_delay" field of AVFormatContext).
When watching multi-bitrate Real-RTSP streams with avplay, the streams to display can be chosen with
"-vst" n and "-ast" n for video and audio respectively, and can be switched on the fly by pressing "v"
and "a".
Example command lines:
To watch a stream over UDP, with a max reordering delay of 0.5 seconds:
avplay -max_delay 500000 -rtsp_transport udp rtsp://server/video.mp4
To watch a stream tunneled over HTTP:
avplay -rtsp_transport http rtsp://server/video.mp4
To send a stream in realtime to a RTSP server, for others to watch:
avconv -re -i <input> -f rtsp -muxdelay 0.1 rtsp://server/live.sdp
To receive a stream in realtime:
avconv -rtsp_flags listen -i rtsp://ownaddress/live.sdp <output>
sap
Session Announcement Protocol (RFC 2974). This is not technically a protocol handler in libavformat, it
is a muxer and demuxer. It is used for signalling of RTP streams, by announcing the SDP for the streams
regularly on a separate port.
Muxer
The syntax for a SAP url given to the muxer is:
sap://<destination>[:<port>][?<options>]
The RTP packets are sent to destination on port port, or to port 5004 if no port is specified. options
is a "&"-separated list. The following options are supported:
announce_addr=address
Specify the destination IP address for sending the announcements to. If omitted, the announcements
are sent to the commonly used SAP announcement multicast address 224.2.127.254 (sap.mcast.net), or
ff0e::2:7ffe if destination is an IPv6 address.
announce_port=port
Specify the port to send the announcements on, defaults to 9875 if not specified.
ttl=ttl
Specify the time to live value for the announcements and RTP packets, defaults to 255.
same_port=0|1
If set to 1, send all RTP streams on the same port pair. If zero (the default), all streams are sent
on unique ports, with each stream on a port 2 numbers higher than the previous. VLC/Live555 requires
this to be set to 1, to be able to receive the stream. The RTP stack in libavformat for receiving
requires all streams to be sent on unique ports.
Example command lines follow.
To broadcast a stream on the local subnet, for watching in VLC:
avconv -re -i <input> -f sap sap://224.0.0.255?same_port=1
Similarly, for watching in avplay:
avconv -re -i <input> -f sap sap://224.0.0.255
And for watching in avplay, over IPv6:
avconv -re -i <input> -f sap sap://[ff0e::1:2:3:4]
Demuxer
The syntax for a SAP url given to the demuxer is:
sap://[<address>][:<port>]
address is the multicast address to listen for announcements on, if omitted, the default 224.2.127.254
(sap.mcast.net) is used. port is the port that is listened on, 9875 if omitted.
The demuxers listens for announcements on the given address and port. Once an announcement is received,
it tries to receive that particular stream.
Example command lines follow.
To play back the first stream announced on the normal SAP multicast address:
avplay sap://
To play back the first stream announced on one the default IPv6 SAP multicast address:
avplay sap://[ff0e::2:7ffe]
tcp
Trasmission Control Protocol.
The required syntax for a TCP url is:
tcp://<hostname>:<port>[?<options>]
listen
Listen for an incoming connection
avconv -i <input> -f <format> tcp://<hostname>:<port>?listen
avplay tcp://<hostname>:<port>
udp
User Datagram Protocol.
The required syntax for a UDP url is:
udp://<hostname>:<port>[?<options>]
options contains a list of &-seperated options of the form key=val. Follow the list of supported
options.
buffer_size=size
set the UDP buffer size in bytes
localport=port
override the local UDP port to bind with
localaddr=addr
Choose the local IP address. This is useful e.g. if sending multicast and the host has multiple
interfaces, where the user can choose which interface to send on by specifying the IP address of that
interface.
pkt_size=size
set the size in bytes of UDP packets
reuse=1|0
explicitly allow or disallow reusing UDP sockets
ttl=ttl
set the time to live value (for multicast only)
connect=1|0
Initialize the UDP socket with "connect()". In this case, the destination address can't be changed
with ff_udp_set_remote_url later. If the destination address isn't known at the start, this option
can be specified in ff_udp_set_remote_url, too. This allows finding out the source address for the
packets with getsockname, and makes writes return with AVERROR(ECONNREFUSED) if "destination
unreachable" is received. For receiving, this gives the benefit of only receiving packets from the
specified peer address/port.
sources=address[,address]
Only receive packets sent to the multicast group from one of the specified sender IP addresses.
block=address[,address]
Ignore packets sent to the multicast group from the specified sender IP addresses.
Some usage examples of the udp protocol with avconv follow.
To stream over UDP to a remote endpoint:
avconv -i <input> -f <format> udp://<hostname>:<port>
To stream in mpegts format over UDP using 188 sized UDP packets, using a large input buffer:
avconv -i <input> -f mpegts udp://<hostname>:<port>?pkt_size=188&buffer_size=65535
To receive over UDP from a remote endpoint:
avconv -i udp://[<multicast-address>]:<port>
BITSTREAM FILTERS
When you configure your Libav build, all the supported bitstream filters are enabled by default. You can
list all available ones using the configure option "--list-bsfs".
You can disable all the bitstream filters using the configure option "--disable-bsfs", and selectively
enable any bitstream filter using the option "--enable-bsf=BSF", or you can disable a particular
bitstream filter using the option "--disable-bsf=BSF".
The option "-bsfs" of the av* tools will display the list of all the supported bitstream filters included
in your build.
Below is a description of the currently available bitstream filters.
aac_adtstoasc
chomp
dump_extradata
h264_mp4toannexb
imx_dump_header
mjpeg2jpeg
Convert MJPEG/AVI1 packets to full JPEG/JFIF packets.
MJPEG is a video codec wherein each video frame is essentially a JPEG image. The individual frames can be
extracted without loss, e.g. by
avconv -i ../some_mjpeg.avi -c:v copy frames_%d.jpg
Unfortunately, these chunks are incomplete JPEG images, because they lack the DHT segment required for
decoding. Quoting from <http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml>:
Avery Lee, writing in the rec.video.desktop newsgroup in 2001, commented that "MJPEG, or at least the
MJPEG in AVIs having the MJPG fourcc, is restricted JPEG with a fixed -- and *omitted* -- Huffman table.
The JPEG must be YCbCr colorspace, it must be 4:2:2, and it must use basic Huffman encoding, not
arithmetic or progressive. . . . You can indeed extract the MJPEG frames and decode them with a regular
JPEG decoder, but you have to prepend the DHT segment to them, or else the decoder won't have any idea
how to decompress the data. The exact table necessary is given in the OpenDML spec."
This bitstream filter patches the header of frames extracted from an MJPEG stream (carrying the AVI1
header ID and lacking a DHT segment) to produce fully qualified JPEG images.
avconv -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg
exiftran -i -9 frame*.jpg
avconv -i frame_%d.jpg -c:v copy rotated.avi
mjpega_dump_header
movsub
mp3_header_compress
mp3_header_decompress
noise
remove_extradata
FILTERGRAPH DESCRIPTION
A filtergraph is a directed graph of connected filters. It can contain cycles, and there can be multiple
links between a pair of filters. Each link has one input pad on one side connecting it to one filter from
which it takes its input, and one output pad on the other side connecting it to the one filter accepting
its output.
Each filter in a filtergraph is an instance of a filter class registered in the application, which
defines the features and the number of input and output pads of the filter.
A filter with no input pads is called a "source", a filter with no output pads is called a "sink".
Filtergraph syntax
A filtergraph can be represented using a textual representation, which is recognized by the -filter/-vf
and -filter_complex options in avconv and -vf in avplay, and by the
"avfilter_graph_parse()"/"avfilter_graph_parse2()" function defined in libavfilter/avfiltergraph.h.
A filterchain consists of a sequence of connected filters, each one connected to the previous one in the
sequence. A filterchain is represented by a list of ","-separated filter descriptions.
A filtergraph consists of a sequence of filterchains. A sequence of filterchains is represented by a list
of ";"-separated filterchain descriptions.
A filter is represented by a string of the form:
[in_link_1]...[in_link_N]filter_name=arguments[out_link_1]...[out_link_M]
filter_name is the name of the filter class of which the described filter is an instance of, and has to
be the name of one of the filter classes registered in the program. The name of the filter class is
optionally followed by a string "=arguments".
arguments is a string which contains the parameters used to initialize the filter instance, and are
described in the filter descriptions below.
The list of arguments can be quoted using the character "'" as initial and ending mark, and the character
'\' for escaping the characters within the quoted text; otherwise the argument string is considered
terminated when the next special character (belonging to the set "[]=;,") is encountered.
The name and arguments of the filter are optionally preceded and followed by a list of link labels. A
link label allows to name a link and associate it to a filter output or input pad. The preceding labels
in_link_1 ... in_link_N, are associated to the filter input pads, the following labels out_link_1 ...
out_link_M, are associated to the output pads.
When two link labels with the same name are found in the filtergraph, a link between the corresponding
input and output pad is created.
If an output pad is not labelled, it is linked by default to the first unlabelled input pad of the next
filter in the filterchain. For example in the filterchain:
nullsrc, split[L1], [L2]overlay, nullsink
the split filter instance has two output pads, and the overlay filter instance two input pads. The first
output pad of split is labelled "L1", the first input pad of overlay is labelled "L2", and the second
output pad of split is linked to the second input pad of overlay, which are both unlabelled.
In a complete filterchain all the unlabelled filter input and output pads must be connected. A
filtergraph is considered valid if all the filter input and output pads of all the filterchains are
connected.
Libavfilter will automatically insert scale filters where format conversion is required. It is possible
to specify swscale flags for those automatically inserted scalers by prepending "sws_flags=flags;" to the
filtergraph description.
Follows a BNF description for the filtergraph syntax:
<NAME> ::= sequence of alphanumeric characters and '_'
<LINKLABEL> ::= "[" <NAME> "]"
<LINKLABELS> ::= <LINKLABEL> [<LINKLABELS>]
<FILTER_ARGUMENTS> ::= sequence of chars (eventually quoted)
<FILTER> ::= [<LINKLABELS>] <NAME> ["=" <FILTER_ARGUMENTS>] [<LINKLABELS>]
<FILTERCHAIN> ::= <FILTER> [,<FILTERCHAIN>]
<FILTERGRAPH> ::= [sws_flags=<flags>;] <FILTERCHAIN> [;<FILTERGRAPH>]
AUDIO FILTERS
When you configure your Libav build, you can disable any of the existing filters using --disable-filters.
The configure output will show the audio filters included in your build.
Below is a description of the currently available audio filters.
aformat
Convert the input audio to one of the specified formats. The framework will negotiate the most
appropriate format to minimize conversions.
The filter accepts the following named parameters:
sample_fmts
A comma-separated list of requested sample formats.
sample_rates
A comma-separated list of requested sample rates.
channel_layouts
A comma-separated list of requested channel layouts.
If a parameter is omitted, all values are allowed.
For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
aformat=sample_fmts\=u8,s16:channel_layouts\=stereo
amix
Mixes multiple audio inputs into a single output.
For example
avconv -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
will mix 3 input audio streams to a single output with the same duration as the first input and a dropout
transition time of 3 seconds.
The filter accepts the following named parameters:
inputs
Number of inputs. If unspecified, it defaults to 2.
duration
How to determine the end-of-stream.
longest
Duration of longest input. (default)
shortest
Duration of shortest input.
first
Duration of first input.
dropout_transition
Transition time, in seconds, for volume renormalization when an input stream ends. The default value
is 2 seconds.
anull
Pass the audio source unchanged to the output.
ashowinfo
Show a line containing various information for each input audio frame. The input audio is not modified.
The shown line contains a sequence of key/value pairs of the form key:value.
A description of each shown parameter follows:
n sequential number of the input frame, starting from 0
pts Presentation timestamp of the input frame, in time base units; the time base depends on the filter
input pad, and is usually 1/sample_rate.
pts_time
presentation timestamp of the input frame in seconds
fmt sample format
chlayout
channel layout
rate
sample rate for the audio frame
nb_samples
number of samples (per channel) in the frame
checksum
Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio the data is treated as
if all the planes were concatenated.
plane_checksums
A list of Adler-32 checksums for each data plane.
asplit
Split input audio into several identical outputs.
The filter accepts a single parameter which specifies the number of outputs. If unspecified, it defaults
to 2.
For example
avconv -i INPUT -filter_complex asplit=5 OUTPUT
will create 5 copies of the input audio.
asyncts
Synchronize audio data with timestamps by squeezing/stretching it and/or dropping samples/adding silence
when needed.
The filter accepts the following named parameters:
compensate
Enable stretching/squeezing the data to make it match the timestamps. Disabled by default. When
disabled, time gaps are covered with silence.
min_delta
Minimum difference between timestamps and audio data (in seconds) to trigger adding/dropping samples.
Default value is 0.1. If you get non-perfect sync with this filter, try setting this parameter to 0.
max_comp
Maximum compensation in samples per second. Relevant only with compensate=1. Default value 500.
first_pts
Assume the first pts should be this value. The time base is 1 / sample rate. This allows for
padding/trimming at the start of stream. By default, no assumption is made about the first frame's
expected pts, so no padding or trimming is done. For example, this could be set to 0 to pad the
beginning with silence if an audio stream starts after the video stream or to trim any samples with a
negative pts due to encoder delay.
channelsplit
Split each channel in input audio stream into a separate output stream.
This filter accepts the following named parameters:
channel_layout
Channel layout of the input stream. Default is "stereo".
For example, assuming a stereo input MP3 file
avconv -i in.mp3 -filter_complex channelsplit out.mkv
will create an output Matroska file with two audio streams, one containing only the left channel and the
other the right channel.
To split a 5.1 WAV file into per-channel files
avconv -i in.wav -filter_complex
'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
-map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
side_right.wav
channelmap
Remap input channels to new locations.
This filter accepts the following named parameters:
channel_layout
Channel layout of the output stream.
map Map channels from input to output. The argument is a comma-separated list of mappings, each in the
"in_channel-out_channel" or in_channel form. in_channel can be either the name of the input channel
(e.g. FL for front left) or its index in the input channel layout. out_channel is the name of the
output channel or its index in the output channel layout. If out_channel is not given then it is
implicitly an index, starting with zero and increasing by one for each mapping.
If no mapping is present, the filter will implicitly map input channels to output channels preserving
index.
For example, assuming a 5.1+downmix input MOV file
avconv -i in.mov -filter 'channelmap=map=DL-FL,DR-FR' out.wav
will create an output WAV file tagged as stereo from the downmix channels of the input.
To fix a 5.1 WAV improperly encoded in AAC's native channel order
avconv -i in.wav -filter 'channelmap=1,2,0,5,3,4:channel_layout=5.1' out.wav
join
Join multiple input streams into one multi-channel stream.
The filter accepts the following named parameters:
inputs
Number of input streams. Defaults to 2.
channel_layout
Desired output channel layout. Defaults to stereo.
map Map channels from inputs to output. The argument is a comma-separated list of mappings, each in the
"input_idx.in_channel-out_channel" form. input_idx is the 0-based index of the input stream.
in_channel can be either the name of the input channel (e.g. FL for front left) or its index in the
specified input stream. out_channel is the name of the output channel.
The filter will attempt to guess the mappings when those are not specified explicitly. It does so by
first trying to find an unused matching input channel and if that fails it picks the first unused input
channel.
E.g. to join 3 inputs (with properly set channel layouts)
avconv -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
To build a 5.1 output from 6 single-channel streams:
avconv -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
'join=inputs=6:channel_layout=5.1:map=0.0-FL,1.0-FR,2.0-FC,3.0-SL,4.0-SR,5.0-LFE'
out
resample
Convert the audio sample format, sample rate and channel layout. This filter is not meant to be used
directly, it is inserted automatically by libavfilter whenever conversion is needed. Use the aformat
filter to force a specific conversion.
volume
Adjust the input audio volume.
The filter accepts the following named parameters:
volume
Expresses how the audio volume will be increased or decreased.
Output values are clipped to the maximum value.
The output audio volume is given by the relation:
<output_volume> = <volume> * <input_volume>
Default value for volume is 1.0.
precision
Mathematical precision.
This determines which input sample formats will be allowed, which affects the precision of the volume
scaling.
fixed
8-bit fixed-point; limits input sample format to U8, S16, and S32.
float
32-bit floating-point; limits input sample format to FLT. (default)
double
64-bit floating-point; limits input sample format to DBL.
Examples
• Halve the input audio volume:
volume=volume=0.5
volume=volume=1/2
volume=volume=-6.0206dB
• Increase input audio power by 6 decibels using fixed-point precision:
volume=volume=6dB:precision=fixed
AUDIO SOURCES
Below is a description of the currently available audio sources.
anullsrc
Null audio source, never return audio frames. It is mainly useful as a template and to be employed in
analysis / debugging tools.
It accepts as optional parameter a string of the form sample_rate:channel_layout.
sample_rate specify the sample rate, and defaults to 44100.
channel_layout specify the channel layout, and can be either an integer or a string representing a
channel layout. The default value of channel_layout is 3, which corresponds to CH_LAYOUT_STEREO.
Check the channel_layout_map definition in libavutil/channel_layout.c for the mapping between strings and
channel layout values.
Follow some examples:
# set the sample rate to 48000 Hz and the channel layout to CH_LAYOUT_MONO.
anullsrc=48000:4
# same as
anullsrc=48000:mono
abuffer
Buffer audio frames, and make them available to the filter chain.
This source is not intended to be part of user-supplied graph descriptions but for insertion by calling
programs through the interface defined in libavfilter/buffersrc.h.
It accepts the following named parameters:
time_base
Timebase which will be used for timestamps of submitted frames. It must be either a floating-point
number or in numerator/denominator form.
sample_rate
Audio sample rate.
sample_fmt
Name of the sample format, as returned by "av_get_sample_fmt_name()".
channel_layout
Channel layout of the audio data, in the form that can be accepted by "av_get_channel_layout()".
All the parameters need to be explicitly defined.
AUDIO SINKS
Below is a description of the currently available audio sinks.
anullsink
Null audio sink, do absolutely nothing with the input audio. It is mainly useful as a template and to be
employed in analysis / debugging tools.
abuffersink
This sink is intended for programmatic use. Frames that arrive on this sink can be retrieved by the
calling program using the interface defined in libavfilter/buffersink.h.
This filter accepts no parameters.
VIDEO FILTERS
When you configure your Libav build, you can disable any of the existing filters using --disable-filters.
The configure output will show the video filters included in your build.
Below is a description of the currently available video filters.
blackframe
Detect frames that are (almost) completely black. Can be useful to detect chapter transitions or
commercials. Output lines consist of the frame number of the detected frame, the percentage of blackness,
the position in the file if known or -1 and the timestamp in seconds.
In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value.
The filter accepts the syntax:
blackframe[=<amount>:[<threshold>]]
amount is the percentage of the pixels that have to be below the threshold, and defaults to 98.
threshold is the threshold below which a pixel value is considered black, and defaults to 32.
boxblur
Apply boxblur algorithm to the input video.
This filter accepts the parameters:
luma_power:luma_radius:chroma_radius:chroma_power:alpha_radius:alpha_power
Chroma and alpha parameters are optional, if not specified they default to the corresponding values set
for luma_radius and luma_power.
luma_radius, chroma_radius, and alpha_radius represent the radius in pixels of the box used for blurring
the corresponding input plane. They are expressions, and can contain the following constants:
w, h
the input width and height in pixels
cw, ch
the input chroma image width and height in pixels
hsub, vsub
horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2
and vsub is 1.
The radius must be a non-negative number, and must not be greater than the value of the expression
"min(w,h)/2" for the luma and alpha planes, and of "min(cw,ch)/2" for the chroma planes.
luma_power, chroma_power, and alpha_power represent how many times the boxblur filter is applied to the
corresponding plane.
Some examples follow:
• Apply a boxblur filter with luma, chroma, and alpha radius set to 2:
boxblur=2:1
• Set luma radius to 2, alpha and chroma radius to 0
boxblur=2:1:0:0:0:0
• Set luma and chroma radius to a fraction of the video dimension
boxblur=min(h,w)/10:1:min(cw,ch)/10:1
copy
Copy the input source unchanged to the output. Mainly useful for testing purposes.
crop
Crop the input video to out_w:out_h:x:y.
The parameters are expressions containing the following constants:
E, PI, PHI
the corresponding mathematical approximated values for e (euler number), pi (greek PI), PHI (golden
ratio)
x, y
the computed values for x and y. They are evaluated for each new frame.
in_w, in_h
the input width and height
iw, ih
same as in_w and in_h
out_w, out_h
the output (cropped) width and height
ow, oh
same as out_w and out_h
n the number of input frame, starting from 0
pos the position in the file of the input frame, NAN if unknown
t timestamp expressed in seconds, NAN if the input timestamp is unknown
The out_w and out_h parameters specify the expressions for the width and height of the output (cropped)
video. They are evaluated just at the configuration of the filter.
The default value of out_w is "in_w", and the default value of out_h is "in_h".
The expression for out_w may depend on the value of out_h, and the expression for out_h may depend on
out_w, but they cannot depend on x and y, as x and y are evaluated after out_w and out_h.
The x and y parameters specify the expressions for the position of the top-left corner of the output
(non-cropped) area. They are evaluated for each frame. If the evaluated value is not valid, it is
approximated to the nearest valid value.
The default value of x is "(in_w-out_w)/2", and the default value for y is "(in_h-out_h)/2", which set
the cropped area at the center of the input image.
The expression for x may depend on y, and the expression for y may depend on x.
Follow some examples:
# crop the central input area with size 100x100
crop=100:100
# crop the central input area with size 2/3 of the input video
"crop=2/3*in_w:2/3*in_h"
# crop the input video central square
crop=in_h
# delimit the rectangle with the top-left corner placed at position
# 100:100 and the right-bottom corner corresponding to the right-bottom
# corner of the input image.
crop=in_w-100:in_h-100:100:100
# crop 10 pixels from the left and right borders, and 20 pixels from
# the top and bottom borders
"crop=in_w-2*10:in_h-2*20"
# keep only the bottom right quarter of the input image
"crop=in_w/2:in_h/2:in_w/2:in_h/2"
# crop height for getting Greek harmony
"crop=in_w:1/PHI*in_w"
# trembling effect
"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)"
# erratic camera effect depending on timestamp
"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
# set x depending on the value of y
"crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
cropdetect
Auto-detect crop size.
Calculate necessary cropping parameters and prints the recommended parameters through the logging system.
The detected dimensions correspond to the non-black area of the input video.
It accepts the syntax:
cropdetect[=<limit>[:<round>[:<reset>]]]
limit
Threshold, which can be optionally specified from nothing (0) to everything (255), defaults to 24.
round
Value which the width/height should be divisible by, defaults to 16. The offset is automatically
adjusted to center the video. Use 2 to get only even dimensions (needed for 4:2:2 video). 16 is best
when encoding to most video codecs.
reset
Counter that determines after how many frames cropdetect will reset the previously detected largest
video area and start over to detect the current optimal crop area. Defaults to 0.
This can be useful when channel logos distort the video area. 0 indicates never reset and return the
largest area encountered during playback.
delogo
Suppress a TV station logo by a simple interpolation of the surrounding pixels. Just set a rectangle
covering the logo and watch it disappear (and sometimes something even uglier appear - your mileage may
vary).
The filter accepts parameters as a string of the form "x:y:w:h:band", or as a list of key=value pairs,
separated by ":".
The description of the accepted parameters follows.
x, y
Specify the top left corner coordinates of the logo. They must be specified.
w, h
Specify the width and height of the logo to clear. They must be specified.
band, t
Specify the thickness of the fuzzy edge of the rectangle (added to w and h). The default value is 4.
show
When set to 1, a green rectangle is drawn on the screen to simplify finding the right x, y, w, h
parameters, and band is set to 4. The default value is 0.
Some examples follow.
• Set a rectangle covering the area with top left corner coordinates 0,0 and size 100x77, setting a
band of size 10:
delogo=0:0:100:77:10
• As the previous example, but use named options:
delogo=x=0:y=0:w=100:h=77:band=10
drawbox
Draw a colored box on the input image.
It accepts the syntax:
drawbox=<x>:<y>:<width>:<height>:<color>
x, y
Specify the top left corner coordinates of the box. Default to 0.
width, height
Specify the width and height of the box, if 0 they are interpreted as the input width and height.
Default to 0.
color
Specify the color of the box to write, it can be the name of a color (case insensitive match) or a
0xRRGGBB[AA] sequence.
Follow some examples:
# draw a black box around the edge of the input image
drawbox
# draw a box with color red and an opacity of 50%
drawbox=10:20:200:60:red@0.5"
drawtext
Draw text string or text from specified file on top of video using the libfreetype library.
To enable compilation of this filter you need to configure Libav with "--enable-libfreetype".
The filter also recognizes strftime() sequences in the provided text and expands them accordingly. Check
the documentation of strftime().
The filter accepts parameters as a list of key=value pairs, separated by ":".
The description of the accepted parameters follows.
fontfile
The font file to be used for drawing text. Path must be included. This parameter is mandatory.
text
The text string to be drawn. The text must be a sequence of UTF-8 encoded characters. This parameter
is mandatory if no file is specified with the parameter textfile.
textfile
A text file containing text to be drawn. The text must be a sequence of UTF-8 encoded characters.
This parameter is mandatory if no text string is specified with the parameter text.
If both text and textfile are specified, an error is thrown.
x, y
The offsets where text will be drawn within the video frame. Relative to the top/left border of the
output image. They accept expressions similar to the overlay filter:
x, y
the computed values for x and y. They are evaluated for each new frame.
main_w, main_h
main input width and height
W, H
same as main_w and main_h
text_w, text_h
rendered text width and height
w, h
same as text_w and text_h
n the number of frames processed, starting from 0
t timestamp expressed in seconds, NAN if the input timestamp is unknown
The default value of x and y is 0.
fontsize
The font size to be used for drawing text. The default value of fontsize is 16.
fontcolor
The color to be used for drawing fonts. Either a string (e.g. "red") or in 0xRRGGBB[AA] format (e.g.
"0xff000033"), possibly followed by an alpha specifier. The default value of fontcolor is "black".
boxcolor
The color to be used for drawing box around text. Either a string (e.g. "yellow") or in 0xRRGGBB[AA]
format (e.g. "0xff00ff"), possibly followed by an alpha specifier. The default value of boxcolor is
"white".
box Used to draw a box around text using background color. Value should be either 1 (enable) or 0
(disable). The default value of box is 0.
shadowx, shadowy
The x and y offsets for the text shadow position with respect to the position of the text. They can
be either positive or negative values. Default value for both is "0".
shadowcolor
The color to be used for drawing a shadow behind the drawn text. It can be a color name (e.g.
"yellow") or a string in the 0xRRGGBB[AA] form (e.g. "0xff00ff"), possibly followed by an alpha
specifier. The default value of shadowcolor is "black".
ft_load_flags
Flags to be used for loading the fonts.
The flags map the corresponding flags supported by libfreetype, and are a combination of the
following values:
default
no_scale
no_hinting
render
no_bitmap
vertical_layout
force_autohint
crop_bitmap
pedantic
ignore_global_advance_width
no_recurse
ignore_transform
monochrome
linear_design
no_autohint
end table
Default value is "render".
For more information consult the documentation for the FT_LOAD_* libfreetype flags.
tabsize
The size in number of spaces to use for rendering the tab. Default value is 4.
fix_bounds
If true, check and fix text coords to avoid clipping.
For example the command:
drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
will draw "Test Text" with font FreeSerif, using the default values for the optional parameters.
The command:
drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"
will draw 'Test Text' with font FreeSerif of size 24 at position x=100 and y=50 (counting from the top-
left corner of the screen), text is yellow with a red box around it. Both the text and the box have an
opacity of 20%.
Note that the double quotes are not necessary if spaces are not used within the parameter list.
For more information about libfreetype, check: <http://www.freetype.org/>.
fade
Apply fade-in/out effect to input video.
It accepts the parameters: type:start_frame:nb_frames
type specifies if the effect type, can be either "in" for fade-in, or "out" for a fade-out effect.
start_frame specifies the number of the start frame for starting to apply the fade effect.
nb_frames specifies the number of frames for which the fade effect has to last. At the end of the fade-in
effect the output video will have the same intensity as the input video, at the end of the fade-out
transition the output video will be completely black.
A few usage examples follow, usable too as test scenarios.
# fade in first 30 frames of video
fade=in:0:30
# fade out last 45 frames of a 200-frame video
fade=out:155:45
# fade in first 25 frames and fade out last 25 frames of a 1000-frame video
fade=in:0:25, fade=out:975:25
# make first 5 frames black, then fade in from frame 5-24
fade=in:5:20
fieldorder
Transform the field order of the input video.
It accepts one parameter which specifies the required field order that the input interlaced video will be
transformed to. The parameter can assume one of the following values:
0 or bff
output bottom field first
1 or tff
output top field first
Default value is "tff".
Transformation is achieved by shifting the picture content up or down by one line, and filling the
remaining line with appropriate picture content. This method is consistent with most broadcast field
order converters.
If the input video is not flagged as being interlaced, or it is already flagged as being of the required
output field order then this filter does not alter the incoming video.
This filter is very useful when converting to or from PAL DV material, which is bottom field first.
For example:
./avconv -i in.vob -vf "fieldorder=bff" out.dv
fifo
Buffer input images and send them when they are requested.
This filter is mainly useful when auto-inserted by the libavfilter framework.
The filter does not take parameters.
format
Convert the input video to one of the specified pixel formats. Libavfilter will try to pick one that is
supported for the input to the next filter.
The filter accepts a list of pixel format names, separated by ":", for example "yuv420p:monow:rgb24".
Some examples follow:
# convert the input video to the format "yuv420p"
format=yuv420p
# convert the input video to any of the formats in the list
format=yuv420p:yuv444p:yuv410p
fps
Convert the video to specified constant framerate by duplicating or dropping frames as necessary.
This filter accepts the following named parameters:
fps Desired output framerate.
frei0r
Apply a frei0r effect to the input video.
To enable compilation of this filter you need to install the frei0r header and configure Libav with
--enable-frei0r.
The filter supports the syntax:
<filter_name>[{:|=}<param1>:<param2>:...:<paramN>]
filter_name is the name to the frei0r effect to load. If the environment variable FREI0R_PATH is defined,
the frei0r effect is searched in each one of the directories specified by the colon separated list in
FREIOR_PATH, otherwise in the standard frei0r paths, which are in this order: HOME/.frei0r-1/lib/,
/usr/local/lib/frei0r-1/, /usr/lib/frei0r-1/.
param1, param2, ... , paramN specify the parameters for the frei0r effect.
A frei0r effect parameter can be a boolean (whose values are specified with "y" and "n"), a double, a
color (specified by the syntax R/G/B, R, G, and B being float numbers from 0.0 to 1.0) or by an
"av_parse_color()" color description), a position (specified by the syntax X/Y, X and Y being float
numbers) and a string.
The number and kind of parameters depend on the loaded effect. If an effect parameter is not specified
the default value is set.
Some examples follow:
# apply the distort0r effect, set the first two double parameters
frei0r=distort0r:0.5:0.01
# apply the colordistance effect, takes a color as first parameter
frei0r=colordistance:0.2/0.3/0.4
frei0r=colordistance:violet
frei0r=colordistance:0x112233
# apply the perspective effect, specify the top left and top right
# image positions
frei0r=perspective:0.2/0.2:0.8/0.2
For more information see: <http://piksel.org/frei0r>
gradfun
Fix the banding artifacts that are sometimes introduced into nearly flat regions by truncation to 8bit
colordepth. Interpolate the gradients that should go where the bands are, and dither them.
This filter is designed for playback only. Do not use it prior to lossy compression, because compression
tends to lose the dither and bring back the bands.
The filter takes two optional parameters, separated by ':': strength:radius
strength is the maximum amount by which the filter will change any one pixel. Also the threshold for
detecting nearly flat regions. Acceptable values range from .51 to 255, default value is 1.2, out-of-
range values will be clipped to the valid range.
radius is the neighborhood to fit the gradient to. A larger radius makes for smoother gradients, but also
prevents the filter from modifying the pixels near detailed regions. Acceptable values are 8-32, default
value is 16, out-of-range values will be clipped to the valid range.
# default parameters
gradfun=1.2:16
# omitting radius
gradfun=1.2
hflip
Flip the input video horizontally.
For example to horizontally flip the input video with avconv:
avconv -i in.avi -vf "hflip" out.avi
hqdn3d
High precision/quality 3d denoise filter. This filter aims to reduce image noise producing smooth images
and making still images really still. It should enhance compressibility.
It accepts the following optional parameters: luma_spatial:chroma_spatial:luma_tmp:chroma_tmp
luma_spatial
a non-negative float number which specifies spatial luma strength, defaults to 4.0
chroma_spatial
a non-negative float number which specifies spatial chroma strength, defaults to 3.0*luma_spatial/4.0
luma_tmp
a float number which specifies luma temporal strength, defaults to 6.0*luma_spatial/4.0
chroma_tmp
a float number which specifies chroma temporal strength, defaults to
luma_tmp*chroma_spatial/luma_spatial
lut, lutrgb, lutyuv
Compute a look-up table for binding each pixel component input value to an output value, and apply it to
input video.
lutyuv applies a lookup table to a YUV input video, lutrgb to an RGB input video.
These filters accept in input a ":"-separated list of options, which specify the expressions used for
computing the lookup table for the corresponding pixel component values.
The lut filter requires either YUV or RGB pixel formats in input, and accepts the options:
c0 (first pixel component)
c1 (second pixel component)
c2 (third pixel component)
c3 (fourth pixel component, corresponds to the alpha component)
The exact component associated to each option depends on the format in input.
The lutrgb filter requires RGB pixel formats in input, and accepts the options:
r (red component)
g (green component)
b (blue component)
a (alpha component)
The lutyuv filter requires YUV pixel formats in input, and accepts the options:
y (Y/luminance component)
u (U/Cb component)
v (V/Cr component)
a (alpha component)
The expressions can contain the following constants and functions:
E, PI, PHI
the corresponding mathematical approximated values for e (euler number), pi (greek PI), PHI (golden
ratio)
w, h
the input width and height
val input value for the pixel component
clipval
the input value clipped in the minval-maxval range
maxval
maximum value for the pixel component
minval
minimum value for the pixel component
negval
the negated value for the pixel component value clipped in the minval-maxval range , it corresponds
to the expression "maxval-clipval+minval"
clip(val)
the computed value in val clipped in the minval-maxval range
gammaval(gamma)
the computed gamma correction value of the pixel component value clipped in the minval-maxval range,
corresponds to the expression "pow((clipval-minval)/(maxval-minval),gamma)*(maxval-minval)+minval"
All expressions default to "val".
Some examples follow:
# negate input video
lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
# the above is the same as
lutrgb="r=negval:g=negval:b=negval"
lutyuv="y=negval:u=negval:v=negval"
# negate luminance
lutyuv=negval
# remove chroma components, turns the video into a graytone image
lutyuv="u=128:v=128"
# apply a luma burning effect
lutyuv="y=2*val"
# remove green and blue components
lutrgb="g=0:b=0"
# set a constant alpha channel value on input
format=rgba,lutrgb=a="maxval-minval/2"
# correct luminance gamma by a 0.5 factor
lutyuv=y=gammaval(0.5)
negate
Negate input video.
This filter accepts an integer in input, if non-zero it negates the alpha component (if available). The
default value in input is 0.
Force libavfilter not to use any of the specified pixel formats for the input to the next filter.
The filter accepts a list of pixel format names, separated by ":", for example "yuv420p:monow:rgb24".
Some examples follow:
# force libavfilter to use a format different from "yuv420p" for the
# input to the vflip filter
noformat=yuv420p,vflip
# convert the input video to any of the formats not contained in the list
noformat=yuv420p:yuv444p:yuv410p
null
Pass the video source unchanged to the output.
ocv
Apply video transform using libopencv.
To enable this filter install libopencv library and headers and configure Libav with --enable-libopencv.
The filter takes the parameters: filter_name{:=}filter_params.
filter_name is the name of the libopencv filter to apply.
filter_params specifies the parameters to pass to the libopencv filter. If not specified the default
values are assumed.
Refer to the official libopencv documentation for more precise information:
<http://opencv.willowgarage.com/documentation/c/image_filtering.html>
Follows the list of supported libopencv filters.
dilate
Dilate an image by using a specific structuring element. This filter corresponds to the libopencv
function "cvDilate".
It accepts the parameters: struct_el:nb_iterations.
struct_el represents a structuring element, and has the syntax: colsxrows+anchor_xxanchor_y/shape
cols and rows represent the number of columns and rows of the structuring element, anchor_x and anchor_y
the anchor point, and shape the shape for the structuring element, and can be one of the values "rect",
"cross", "ellipse", "custom".
If the value for shape is "custom", it must be followed by a string of the form "=filename". The file
with name filename is assumed to represent a binary image, with each printable character corresponding to
a bright pixel. When a custom shape is used, cols and rows are ignored, the number or columns and rows of
the read file are assumed instead.
The default value for struct_el is "3x3+0x0/rect".
nb_iterations specifies the number of times the transform is applied to the image, and defaults to 1.
Follow some example:
# use the default values
ocv=dilate
# dilate using a structuring element with a 5x5 cross, iterate two times
ocv=dilate=5x5+2x2/cross:2
# read the shape from the file diamond.shape, iterate two times
# the file diamond.shape may contain a pattern of characters like this:
# *
# ***
# *****
# ***
# *
# the specified cols and rows are ignored (but not the anchor point coordinates)
ocv=0x0+2x2/custom=diamond.shape:2
erode
Erode an image by using a specific structuring element. This filter corresponds to the libopencv
function "cvErode".
The filter accepts the parameters: struct_el:nb_iterations, with the same syntax and semantics as the
dilate filter.
smooth
Smooth the input video.
The filter takes the following parameters: type:param1:param2:param3:param4.
type is the type of smooth filter to apply, and can be one of the following values: "blur",
"blur_no_scale", "median", "gaussian", "bilateral". The default value is "gaussian".
param1, param2, param3, and param4 are parameters whose meanings depend on smooth type. param1 and param2
accept integer positive values or 0, param3 and param4 accept float values.
The default value for param1 is 3, the default value for the other parameters is 0.
These parameters correspond to the parameters assigned to the libopencv function "cvSmooth".
overlay
Overlay one video on top of another.
It takes two inputs and one output, the first input is the "main" video on which the second input is
overlayed.
It accepts the parameters: x:y.
x is the x coordinate of the overlayed video on the main video, y is the y coordinate. The parameters are
expressions containing the following parameters:
main_w, main_h
main input width and height
W, H
same as main_w and main_h
overlay_w, overlay_h
overlay input width and height
w, h
same as overlay_w and overlay_h
Be aware that frames are taken from each input video in timestamp order, hence, if their initial
timestamps differ, it is a a good idea to pass the two inputs through a setpts=PTS-STARTPTS filter to
have them begin in the same zero timestamp, as it does the example for the movie filter.
Follow some examples:
# draw the overlay at 10 pixels from the bottom right
# corner of the main video.
overlay=main_w-overlay_w-10:main_h-overlay_h-10
# insert a transparent PNG logo in the bottom left corner of the input
avconv -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
# insert 2 different transparent PNG logos (second logo on bottom
# right corner):
avconv -i input -i logo1 -i logo2 -filter_complex
'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
# add a transparent color layer on top of the main video,
# WxH specifies the size of the main input to the overlay filter
color=red.3:WxH [over]; [in][over] overlay [out]
You can chain together more overlays but the efficiency of such approach is yet to be tested.
pad
Add paddings to the input image, and places the original input at the given coordinates x, y.
It accepts the following parameters: width:height:x:y:color.
The parameters width, height, x, and y are expressions containing the following constants:
E, PI, PHI
the corresponding mathematical approximated values for e (euler number), pi (greek PI), phi (golden
ratio)
in_w, in_h
the input video width and height
iw, ih
same as in_w and in_h
out_w, out_h
the output width and height, that is the size of the padded area as specified by the width and height
expressions
ow, oh
same as out_w and out_h
x, y
x and y offsets as specified by the x and y expressions, or NAN if not yet specified
a input display aspect ratio, same as iw / ih
hsub, vsub
horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2
and vsub is 1.
Follows the description of the accepted parameters.
width, height
Specify the size of the output image with the paddings added. If the value for width or height is 0,
the corresponding input size is used for the output.
The width expression can reference the value set by the height expression, and vice versa.
The default value of width and height is 0.
x, y
Specify the offsets where to place the input image in the padded area with respect to the top/left
border of the output image.
The x expression can reference the value set by the y expression, and vice versa.
The default value of x and y is 0.
color
Specify the color of the padded area, it can be the name of a color (case insensitive match) or a
0xRRGGBB[AA] sequence.
The default value of color is "black".
Some examples follow:
# Add paddings with color "violet" to the input video. Output video
# size is 640x480, the top-left corner of the input video is placed at
# column 0, row 40.
pad=640:480:0:40:violet
# pad the input to get an output with dimensions increased bt 3/2,
# and put the input video at the center of the padded area
pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
# pad the input to get a squared output with size equal to the maximum
# value between the input width and height, and put the input video at
# the center of the padded area
pad="max(iw,ih):ow:(ow-iw)/2:(oh-ih)/2"
# pad the input to get a final w/h ratio of 16:9
pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
# double output size and put the input video in the bottom-right
# corner of the output padded area
pad="2*iw:2*ih:ow-iw:oh-ih"
pixdesctest
Pixel format descriptor test filter, mainly useful for internal testing. The output video should be equal
to the input video.
For example:
format=monow, pixdesctest
can be used to test the monowhite pixel format descriptor definition.
scale
Scale the input video to width:height and/or convert the image format.
The parameters width and height are expressions containing the following constants:
E, PI, PHI
the corresponding mathematical approximated values for e (euler number), pi (greek PI), phi (golden
ratio)
in_w, in_h
the input width and height
iw, ih
same as in_w and in_h
out_w, out_h
the output (cropped) width and height
ow, oh
same as out_w and out_h
dar, a
input display aspect ratio, same as iw / ih
sar input sample aspect ratio
hsub, vsub
horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" hsub is 2
and vsub is 1.
If the input image format is different from the format requested by the next filter, the scale filter
will convert the input to the requested format.
If the value for width or height is 0, the respective input size is used for the output.
If the value for width or height is -1, the scale filter will use, for the respective output size, a
value that maintains the aspect ratio of the input image.
The default value of width and height is 0.
Some examples follow:
# scale the input video to a size of 200x100.
scale=200:100
# scale the input to 2x
scale=2*iw:2*ih
# the above is the same as
scale=2*in_w:2*in_h
# scale the input to half size
scale=iw/2:ih/2
# increase the width, and set the height to the same size
scale=3/2*iw:ow
# seek for Greek harmony
scale=iw:1/PHI*iw
scale=ih*PHI:ih
# increase the height, and set the width to 3/2 of the height
scale=3/2*oh:3/5*ih
# increase the size, but make the size a multiple of the chroma
scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
# increase the width to a maximum of 500 pixels, keep the same input aspect ratio
scale='min(500, iw*3/2):-1'
select
Select frames to pass in output.
It accepts in input an expression, which is evaluated for each input frame. If the expression is
evaluated to a non-zero value, the frame is selected and passed to the output, otherwise it is discarded.
The expression can contain the following constants:
PI Greek PI
PHI golden ratio
E Euler number
n the sequential number of the filtered frame, starting from 0
selected_n
the sequential number of the selected frame, starting from 0
prev_selected_n
the sequential number of the last selected frame, NAN if undefined
TB timebase of the input timestamps
pts the PTS (Presentation TimeStamp) of the filtered video frame, expressed in TB units, NAN if undefined
t the PTS (Presentation TimeStamp) of the filtered video frame, expressed in seconds, NAN if undefined
prev_pts
the PTS of the previously filtered video frame, NAN if undefined
prev_selected_pts
the PTS of the last previously filtered video frame, NAN if undefined
prev_selected_t
the PTS of the last previously selected video frame, NAN if undefined
start_pts
the PTS of the first video frame in the video, NAN if undefined
start_t
the time of the first video frame in the video, NAN if undefined
pict_type
the type of the filtered frame, can assume one of the following values:
I
P
B
S
SI
SP
BI
interlace_type
the frame interlace type, can assume one of the following values:
PROGRESSIVE
the frame is progressive (not interlaced)
TOPFIRST
the frame is top-field-first
BOTTOMFIRST
the frame is bottom-field-first
key 1 if the filtered frame is a key-frame, 0 otherwise
pos the position in the file of the filtered frame, -1 if the information is not available (e.g. for
synthetic video)
The default value of the select expression is "1".
Some examples follow:
# select all frames in input
select
# the above is the same as:
select=1
# skip all frames:
select=0
# select only I-frames
select='eq(pict_type,I)'
# select one frame every 100
select='not(mod(n,100))'
# select only frames contained in the 10-20 time interval
select='gte(t,10)*lte(t,20)'
# select only I frames contained in the 10-20 time interval
select='gte(t,10)*lte(t,20)*eq(pict_type,I)'
# select frames with a minimum distance of 10 seconds
select='isnan(prev_selected_t)+gte(t-prev_selected_t,10)'
setdar
Set the Display Aspect Ratio for the filter output video.
This is done by changing the specified Sample (aka Pixel) Aspect Ratio, according to the following
equation: DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR
Keep in mind that this filter does not modify the pixel dimensions of the video frame. Also the display
aspect ratio set by this filter may be changed by later filters in the filterchain, e.g. in case of
scaling or if another "setdar" or a "setsar" filter is applied.
The filter accepts a parameter string which represents the wanted display aspect ratio. The parameter
can be a floating point number string, or an expression of the form num:den, where num and den are the
numerator and denominator of the aspect ratio. If the parameter is not specified, it is assumed the
value "0:1".
For example to change the display aspect ratio to 16:9, specify:
setdar=16:9
# the above is equivalent to
setdar=1.77777
See also the setsar filter documentation.
setpts
Change the PTS (presentation timestamp) of the input video frames.
Accept in input an expression evaluated through the eval API, which can contain the following constants:
PTS the presentation timestamp in input
PI Greek PI
PHI golden ratio
E Euler number
N the count of the input frame, starting from 0.
STARTPTS
the PTS of the first video frame
INTERLACED
tell if the current frame is interlaced
POS original position in the file of the frame, or undefined if undefined for the current frame
PREV_INPTS
previous input PTS
PREV_OUTPTS
previous output PTS
Some examples follow:
# start counting PTS from zero
setpts=PTS-STARTPTS
# fast motion
setpts=0.5*PTS
# slow motion
setpts=2.0*PTS
# fixed rate 25 fps
setpts=N/(25*TB)
# fixed rate 25 fps with some jitter
setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
setsar
Set the Sample (aka Pixel) Aspect Ratio for the filter output video.
Note that as a consequence of the application of this filter, the output display aspect ratio will change
according to the following equation: DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR
Keep in mind that the sample aspect ratio set by this filter may be changed by later filters in the
filterchain, e.g. if another "setsar" or a "setdar" filter is applied.
The filter accepts a parameter string which represents the wanted sample aspect ratio. The parameter can
be a floating point number string, or an expression of the form num:den, where num and den are the
numerator and denominator of the aspect ratio. If the parameter is not specified, it is assumed the
value "0:1".
For example to change the sample aspect ratio to 10:11, specify:
setsar=10:11
settb
Set the timebase to use for the output frames timestamps. It is mainly useful for testing timebase
configuration.
It accepts in input an arithmetic expression representing a rational. The expression can contain the
constants "PI", "E", "PHI", "AVTB" (the default timebase), and "intb" (the input timebase).
The default value for the input is "intb".
Follow some examples.
# set the timebase to 1/25
settb=1/25
# set the timebase to 1/10
settb=0.1
#set the timebase to 1001/1000
settb=1+0.001
#set the timebase to 2*intb
settb=2*intb
#set the default timebase value
settb=AVTB
showinfo
Show a line containing various information for each input video frame. The input video is not modified.
The shown line contains a sequence of key/value pairs of the form key:value.
A description of each shown parameter follows:
n sequential number of the input frame, starting from 0
pts Presentation TimeStamp of the input frame, expressed as a number of time base units. The time base
unit depends on the filter input pad.
pts_time
Presentation TimeStamp of the input frame, expressed as a number of seconds
pos position of the frame in the input stream, -1 if this information in unavailable and/or meaningless
(for example in case of synthetic video)
fmt pixel format name
sar sample aspect ratio of the input frame, expressed in the form num/den
s size of the input frame, expressed in the form widthxheight
i interlaced mode ("P" for "progressive", "T" for top field first, "B" for bottom field first)
iskey
1 if the frame is a key frame, 0 otherwise
type
picture type of the input frame ("I" for an I-frame, "P" for a P-frame, "B" for a B-frame, "?" for
unknown type). Check also the documentation of the "AVPictureType" enum and of the
"av_get_picture_type_char" function defined in libavutil/avutil.h.
checksum
Adler-32 checksum of all the planes of the input frame
plane_checksum
Adler-32 checksum of each plane of the input frame, expressed in the form "[c0 c1 c2 c3]"
split
Split input video into several identical outputs.
The filter accepts a single parameter which specifies the number of outputs. If unspecified, it defaults
to 2.
For example
avconv -i INPUT -filter_complex split=5 OUTPUT
will create 5 copies of the input video.
transpose
Transpose rows with columns in the input video and optionally flip it.
It accepts a parameter representing an integer, which can assume the values:
0 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
L.R L.l
. . -> . .
l.r R.r
1 Rotate by 90 degrees clockwise, that is:
L.R l.L
. . -> . .
l.r r.R
2 Rotate by 90 degrees counterclockwise, that is:
L.R R.r
. . -> . .
l.r L.l
3 Rotate by 90 degrees clockwise and vertically flip, that is:
L.R r.R
. . -> . .
l.r l.L
unsharp
Sharpen or blur the input video.
It accepts the following parameters:
luma_msize_x:luma_msize_y:luma_amount:chroma_msize_x:chroma_msize_y:chroma_amount
Negative values for the amount will blur the input video, while positive values will sharpen. All
parameters are optional and default to the equivalent of the string '5:5:1.0:5:5:0.0'.
luma_msize_x
Set the luma matrix horizontal size. It can be an integer between 3 and 13, default value is 5.
luma_msize_y
Set the luma matrix vertical size. It can be an integer between 3 and 13, default value is 5.
luma_amount
Set the luma effect strength. It can be a float number between -2.0 and 5.0, default value is 1.0.
chroma_msize_x
Set the chroma matrix horizontal size. It can be an integer between 3 and 13, default value is 5.
chroma_msize_y
Set the chroma matrix vertical size. It can be an integer between 3 and 13, default value is 5.
luma_amount
Set the chroma effect strength. It can be a float number between -2.0 and 5.0, default value is 0.0.
# Strong luma sharpen effect parameters
unsharp=7:7:2.5
# Strong blur of both luma and chroma parameters
unsharp=7:7:-2:7:7:-2
# Use the default values with B<avconv>
./avconv -i in.avi -vf "unsharp" out.mp4
vflip
Flip the input video vertically.
./avconv -i in.avi -vf "vflip" out.avi
yadif
Deinterlace the input video ("yadif" means "yet another deinterlacing filter").
It accepts the optional parameters: mode:parity:auto.
mode specifies the interlacing mode to adopt, accepts one of the following values:
0 output 1 frame for each frame
1 output 1 frame for each field
2 like 0 but skips spatial interlacing check
3 like 1 but skips spatial interlacing check
Default value is 0.
parity specifies the picture field parity assumed for the input interlaced video, accepts one of the
following values:
0 assume top field first
1 assume bottom field first
-1 enable automatic detection
Default value is -1. If interlacing is unknown or decoder does not export this information, top field
first will be assumed.
auto specifies if deinterlacer should trust the interlaced flag and only deinterlace frames marked as
interlaced
0 deinterlace all frames
1 only deinterlace frames marked as interlaced
Default value is 0.
VIDEO SOURCES
Below is a description of the currently available video sources.
buffer
Buffer video frames, and make them available to the filter chain.
This source is mainly intended for a programmatic use, in particular through the interface defined in
libavfilter/vsrc_buffer.h.
It accepts the following parameters:
width:height:pix_fmt_string:timebase_num:timebase_den:sample_aspect_ratio_num:sample_aspect_ratio.den
All the parameters need to be explicitly defined.
Follows the list of the accepted parameters.
width, height
Specify the width and height of the buffered video frames.
pix_fmt_string
A string representing the pixel format of the buffered video frames. It may be a number
corresponding to a pixel format, or a pixel format name.
timebase_num, timebase_den
Specify numerator and denomitor of the timebase assumed by the timestamps of the buffered frames.
sample_aspect_ratio.num, sample_aspect_ratio.den
Specify numerator and denominator of the sample aspect ratio assumed by the video frames.
For example:
buffer=320:240:yuv410p:1:24:1:1
will instruct the source to accept video frames with size 320x240 and with format "yuv410p", assuming
1/24 as the timestamps timebase and square pixels (1:1 sample aspect ratio). Since the pixel format with
name "yuv410p" corresponds to the number 6 (check the enum AVPixelFormat definition in
libavutil/pixfmt.h), this example corresponds to:
buffer=320:240:6:1:24
color
Provide an uniformly colored input.
It accepts the following parameters: color:frame_size:frame_rate
Follows the description of the accepted parameters.
color
Specify the color of the source. It can be the name of a color (case insensitive match) or a
0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The default value is "black".
frame_size
Specify the size of the sourced video, it may be a string of the form widthxheight, or the name of a
size abbreviation. The default value is "320x240".
frame_rate
Specify the frame rate of the sourced video, as the number of frames generated per second. It has to
be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid
video frame rate abbreviation. The default value is "25".
For example the following graph description will generate a red source with an opacity of 0.2, with size
"qcif" and a frame rate of 10 frames per second, which will be overlayed over the source connected to the
pad with identifier "in".
"color=red@0.2:qcif:10 [color]; [in][color] overlay [out]"
movie
Read a video stream from a movie container.
Note that this source is a hack that bypasses the standard input path. It can be useful in applications
that do not support arbitrary filter graphs, but its use is discouraged in those that do. Specifically in
avconv this filter should never be used, the -filter_complex option fully replaces it.
It accepts the syntax: movie_name[:options] where movie_name is the name of the resource to read (not
necessarily a file but also a device or a stream accessed through some protocol), and options is an
optional sequence of key=value pairs, separated by ":".
The description of the accepted options follows.
format_name, f
Specifies the format assumed for the movie to read, and can be either the name of a container or an
input device. If not specified the format is guessed from movie_name or by probing.
seek_point, sp
Specifies the seek point in seconds, the frames will be output starting from this seek point, the
parameter is evaluated with "av_strtod" so the numerical value may be suffixed by an IS postfix.
Default value is "0".
stream_index, si
Specifies the index of the video stream to read. If the value is -1, the best suited video stream
will be automatically selected. Default value is "-1".
This filter allows to overlay a second video on top of main input of a filtergraph as shown in this
graph:
input -----------> deltapts0 --> overlay --> output
^
|
movie --> scale--> deltapts1 -------+
Some examples follow:
# skip 3.2 seconds from the start of the avi file in.avi, and overlay it
# on top of the input labelled as "in".
movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
# read from a video4linux2 device, and overlay it on top of the input
# labelled as "in"
movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
nullsrc
Null video source, never return images. It is mainly useful as a template and to be employed in analysis
/ debugging tools.
It accepts as optional parameter a string of the form width:height:timebase.
width and height specify the size of the configured source. The default values of width and height are
respectively 352 and 288 (corresponding to the CIF size format).
timebase specifies an arithmetic expression representing a timebase. The expression can contain the
constants "PI", "E", "PHI", "AVTB" (the default timebase), and defaults to the value "AVTB".
frei0r_src
Provide a frei0r source.
To enable compilation of this filter you need to install the frei0r header and configure Libav with
--enable-frei0r.
The source supports the syntax:
<size>:<rate>:<src_name>[{=|:}<param1>:<param2>:...:<paramN>]
size is the size of the video to generate, may be a string of the form widthxheight or a frame size
abbreviation. rate is the rate of the video to generate, may be a string of the form num/den or a frame
rate abbreviation. src_name is the name to the frei0r source to load. For more information regarding
frei0r and how to set the parameters read the section frei0r in the description of the video filters.
Some examples follow:
# generate a frei0r partik0l source with size 200x200 and framerate 10
# which is overlayed on the overlay filter main input
frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
rgbtestsrc, testsrc
The "rgbtestsrc" source generates an RGB test pattern useful for detecting RGB vs BGR issues. You should
see a red, green and blue stripe from top to bottom.
The "testsrc" source generates a test video pattern, showing a color pattern, a scrolling gradient and a
timestamp. This is mainly intended for testing purposes.
Both sources accept an optional sequence of key=value pairs, separated by ":". The description of the
accepted options follows.
size, s
Specify the size of the sourced video, it may be a string of the form widthxheight, or the name of a
size abbreviation. The default value is "320x240".
rate, r
Specify the frame rate of the sourced video, as the number of frames generated per second. It has to
be a string in the format frame_rate_num/frame_rate_den, an integer number, a float number or a valid
video frame rate abbreviation. The default value is "25".
sar Set the sample aspect ratio of the sourced video.
duration
Set the video duration of the sourced video. The accepted syntax is:
[-]HH[:MM[:SS[.m...]]]
[-]S+[.m...]
See also the function "av_parse_time()".
If not specified, or the expressed duration is negative, the video is supposed to be generated
forever.
For example the following:
testsrc=duration=5.3:size=qcif:rate=10
will generate a video with a duration of 5.3 seconds, with size 176x144 and a framerate of 10 frames per
second.
VIDEO SINKS
Below is a description of the currently available video sinks.
buffersink
Buffer video frames, and make them available to the end of the filter graph.
This sink is intended for a programmatic use through the interface defined in libavfilter/buffersink.h.
nullsink
Null video sink, do absolutely nothing with the input video. It is mainly useful as a template and to be
employed in analysis / debugging tools.
METADATA
Libav is able to dump metadata from media files into a simple UTF-8-encoded INI-like text file and then
load it back using the metadata muxer/demuxer.
The file format is as follows:
1. A file consists of a header and a number of metadata tags divided into sections, each on its own
line.
2. The header is a ';FFMETADATA' string, followed by a version number (now 1).
3. Metadata tags are of the form 'key=value'
4. Immediately after header follows global metadata
5. After global metadata there may be sections with per-stream/per-chapter metadata.
6. A section starts with the section name in uppercase (i.e. STREAM or CHAPTER) in brackets ('[', ']')
and ends with next section or end of file.
7. At the beginning of a chapter section there may be an optional timebase to be used for start/end
values. It must be in form 'TIMEBASE=num/den', where num and den are integers. If the timebase is
missing then start/end times are assumed to be in milliseconds. Next a chapter section must contain
chapter start and end times in form 'START=num', 'END=num', where num is a positive integer.
8. Empty lines and lines starting with ';' or '#' are ignored.
9. Metadata keys or values containing special characters ('=', ';', '#', '\' and a newline) must be
escaped with a backslash '\'.
10. Note that whitespace in metadata (e.g. foo = bar) is considered to be a part of the tag (in the
example above key is 'foo ', value is ' bar').
A ffmetadata file might look like this:
;FFMETADATA1
title=bike\\shed
;this is a comment
artist=Libav troll team
[CHAPTER]
TIMEBASE=1/1000
START=0
#chapter ends at 0:01:00
END=60000
title=chapter \#1
[STREAM]
title=multi\
line
SEE ALSO
avplay(1), avprobe(1) and the Libav HTML documentation
AUTHORS
The Libav developers
2016-12-07 AVCONV(1)