NAME

       SReview::Video - SReview internal representation of an asset

SYNOPSIS

         use SReview::Video;
         use SReview::Video::ProfileFactory;
         use SReview::Videopipe;

         # convert any input file to VP9 at recommended settings for vertical resolution and frame rate
         my $input = SReview::Video->new(url => $input_filename);
         my $profile = SReview::Video::ProfileFactory->new("vp9", $input);
         my $output = SReview::Video->new(url => $output_filename, reference => $profile);
         SReview::Videopipe->new(inputs => [$input], output => $output)->run();

         # do that again; but this time, force vorbis audio:
         $output = SReview::Video->new(url => $other_filename, reference => $profile);
         $output->audio_codec("libvorbis");
         SReview::Videopipe->new(inputs => [$input], output => $output)->run();

DESCRIPTION

       The SReview::Video package is used to represent media assets inside SReview. It is a
       "Moose"-based base class for much of the other Video* classes in SReview.

       There is one required attribute, "url", which represents the filename of the video
       (however, for SReview::Video::NGinX, it should be an HTTP URL instead).

       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 "SReview::Video" 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 "SReview::Video" 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 "SReview::Video::ProfileFactory->create()" is also an SReview::Video
       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 "SReview::Video::ProfileFactory->create()" method.

       For more information on how to use the files referred to in the "SReview::Video" object in
       an ffmpeg command line, please see "SReview::Videopipe".

ATTRIBUTES

       The following attributes are supported by SReview::Video. 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_style
       The time unit is used for the "duration" attribute. One of 'seconds' (default) or
       'frames'. Will not be probed.

   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). "SReview::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). "SReview::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

   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 SReview 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 "SReview::Video" 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 "SReview::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.

   vstream_id
       Returns the numeric ID for the first video stream in this file. Useful for the
       implementation of stream mappings etc; see "SReview::Map"

   extra_params
       Add extra parameters. This should be used sparingly, rather add some abstraction.

   time_offset
       Apply an input time offset to this video (only valid when used as an input video in
       SReview::Videopipe). Can be used to apply A/V sync correction values.