oracular (3) Media::Convert::Asset.3pm.gz
NAME
Media::Convert::Asset - Media::Convert representation of a media asset
SYNOPSIS
use Media::Convert::Asset;
use Media::Convert::ProfileFactory;
use Media::Convert::Pipe;
# convert any input file to VP9 at recommended settings for vertical resolution and frame rate
my $input = Media::Convert::Asset->new(url => $input_filename);
my $profile = Media::Convert::ProfileFactory->new("vp9", $input);
my $output = Media::Convert::Asset->new(url => $output_filename, reference => $profile);
Media::Convert::Pipe->new(inputs => [$input], output => $output)->run();
# do that again; but this time, force vorbis audio:
$output = Media::Convert::Asset->new(url => $other_filename, reference => $profile);
$output->audio_codec("libvorbis");
Media::Convert::Pipe->new(inputs => [$input], output => $output)->run();
# Merge the video stream from one file with the audio stream from another,
# and convert to VP9
use Media::Convert::Map;
my $input_v = Media::Convert::Asset->new(url => $input_video_filename);
my $input_a = Media::Convert::Asset->new(url => $input_audio_filename);
$profile = Media::Convert::ProfileFactory->new("vp9", $input);
$output = Media::Convert::Asset->new(url => $merged_filename, reference => $profile);
my $map_v = Media::Convert::Map->new(input => $input_v, type => "stream", choice => "video");
my $map_a = Media::Convert::Map->new(input => $input_a, type => "stream", choice => "audio");
Media::Convert::Pipe->new(inputs => [$input_a, $input_v], map => [$map_a, $map_v], output => $output)->run();
DESCRIPTION
The "Media::Convert::Asset" package is used to represent media assets inside "Media::Convert". It is a
"Moose"-based base class for much of the other classes in "Media::Convert".
There is one required attribute, "url", which represents the filename of the asset.
If the "url" attribute points to an existing file and an attempt is made to read any of the codec,
framerate, bit rate, or similar attributes (without explicitly writing to them first), then
"Media::Convert::Asset" will call "ffprobe" on the file in question, and use that to populate the
requested attributes. If it does not, or "ffprobe" is incapable of detecting the requested attribute
(which may be the case for things like audio or video bitrate), then the attribute in question will
resolve to "undef".
If the "url" attribute does not point to an existing file and an attempt is made to read any of the
codec, framerate, bit rate, or similar attributes (without explicitly writing to them first), then they
will resolve to "undef". However, if the "reference" attribute is populated with another
"Media::Convert::Asset" object, then reading any of the codec, framerate, bit rate, or similar attributes
(without explicitly writing to them first) will resolve to the value of the requested attribute that is
set or detected on the "reference" object.
The return value of "Media::Convert::ProfileFactory->create()" is also a Media::Convert object, but with
different implementations of some of the probing methods; this allows it to choose the correct values for
things like bitrate and encoder speed based on properties set in the input object provided to the
"Media::Convert::ProfileFactory->create()" method.
For more information on how to use the files referred to in the "Media::Convert::Asset" object in an
ffmpeg command line, please see "Media::Convert::Pipe".
ATTRIBUTES
The following attributes are supported by "Media::Convert::Asset". All attributes will be probed from
ffprobe output unless noted otherwise.
url
The filename of the asset this object should deal with. Required at construction time. Will not be
probed.
mtime
The mtime of the file backing this asset. Only defined if the file exists at the time the attribute is
first read, and is not updated later on.
duration
The duration of this asset.
duration_frames
The number of frames in this asset.
duration_style
The time unit is used for the "duration" attribute. One of 'seconds' (default) or 'frames'. Will not be
probed.
Deprecated; will be removed in a future release. Use duration_frames instead of setting this to a non-
default value.
video_codec
The codec in use for the video stream. Note that "ffprobe" will sometimes use a string (e.g., "vp8") that
is not the best choice when instructing "ffmpeg" to transcode video to the said codec (for vp8, the use
of "libvpx" is recommended). "Media::Convert::CodecMap" is used to map detected codecs to output codecs
and resolve this issue.
audio_codec
The codec in use for the audio stream. Note that "ffprobe" will sometimes use a string (e.g., "vorbis")
that is not the best choice when instructing "ffmpeg" to transcode audio to the said codec (for vorbis,
the use of "libvorbis" is recommended). "Media::Convert::CodecMap" is used to map detected codecs to
output codecs and resolve this issue.
video_size
A string representing the resolution of the video in "WxH" format, where W is the width and H is the
height.
This attribute is special in that in contrast to all the other attributes, it is not provided directly by
"ffprobe"; instead, when this parameter is read, the "video_width" and "video_height" attributes are read
and combined.
That does mean that you should not read this attribute, and based on that possibly set the height and/or
width attributes of a video (or vice versa). Instead, you should read either the "video_width" and
"video_height" attribute, or this one.
Failure to follow this rule will result in undefined behaviour.
video_width
The width of the video, in pixels.
video_height
The height of the video, in pixels.
video_bitrate
The bit rate of this video, in bits per second.
Note that not all container formats support probing the bitrate of the encoded video or audio; when read
on input objects with those that do not, this will resolve to "undef".
video_minrate
The minimum bit rate for this video, in bits per second.
Defaults to 0.5 * video_bitrate
video_maxrate
The maximum bit rate for this video, in bits per second.
Defaults to 1.45 * video_bitrate
video_preset
The value for the -preset parameter. Used by some codecs, like av1 (and pretty critical there).
aspect_ratio
The Display Aspect Ratio of a video. Note that with non-square pixels, this is not guaranteed to be what
one would expect when reading the "video_size" attribute.
audio_bitrate
The bit rate of the audio stream on this video, in bits per second
audio_samplerate
The sample rate of the audio, in samples per second
video_framerate
The frame rate of the video, as a fraction.
Note that in the weird US frame rate, this could be 30000/1001.
fragment_start
If set, this instructs Media::Convert on read to only read a particular part of the video from this file.
Should be specified in seconds; will not be probed.
quality
The quality used for the video encoding, i.e., the value passed to the "-crf" parameter. Mostly for use
by a profile. Will not be probed.
metadata
Can be used to set video metadata (as per "ffmpeg"'s "-metadata" parameter). Functions "add_metadata" and
"drop_metadata" can be used to add or remove individual metedata values. Will not be probed.
reference
If set to any "Media::Convert::Asset" object, then when any value is being probed, rather than trying to
run "ffprobe" on the file pointed to by our "url" attribute, we will use the value reported by the
referenced object.
Can be used in "build a file almost like this one, but with these things different" kind of scenarios.
Will not be probed (obviously).
pix_fmt
The pixel format (e.g., "yuv420p" or the likes) of the video.
astream_id
Returns the numeric ID for the first audio stream in this file. Useful for the implementation of stream
mappings etc; see "Media::Convert::Map"
blackspots
Returns an array of hashes. Each hash contains a member "start", "end", and "duration", containing the
start, end, and duration, respectively, of locations in the video file that are (almost) entirely black.
Could be used by a script for automatic review.
Note that the ffmpeg run required to detect blackness is CPU intensive and may require a very long time
to finish.
astream_ids
Returns an array with the IDs for the audio streams in this file.
astream_count
Returns the number of audio streams in this file.
audio_channel_count
Returns the number of channels in the first audio stream
vstream_id
Returns the numeric ID for the first video stream in this file. Useful for the implementation of stream
mappings etc; see "Media::Convert::Map"
extra_params
Add extra (output) parameters. This should be used sparingly, rather add some abstraction.
handles
• add_param (adds an extra parameter)
• drop_param (delete a parameter)
input_params
Add extra input parameters. This should be used sparingly, rather add some abstraction.
handles
• add_input_param (adds an extra parameter)
• drop_input_param (delete a parameter)
time_offset
Apply an input time offset to this video (only valid when used as an input video in
Media::Convert::Pipe). Can be used to apply A/V sync correction values.