| SReview::Video(3pm) | User Contributed Perl Documentation | SReview::Video(3pm) |
SReview::Video - SReview internal representation of an asset
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();
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".
The following attributes are supported by SReview::Video. All attributes will be probed from ffprobe output unless noted otherwise.
The filename of the asset this object should deal with. Required at construction time. Will not be probed.
The duration of this asset.
The time unit is used for the "duration" attribute. One of 'seconds' (default) or 'frames'. Will not be probed.
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.
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.
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.
The width of the video, in pixels.
The height of the video, in pixels.
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".
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.
The bit rate of the audio stream on this video, in bits per second
The sample rate of the audio, in samples per second
The frame rate of the video, as a fraction.
Note that in the weird US frame rate, this could be 30000/1001.
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.
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.
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.
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).
The pixel format (e.g., "yuv420p" or the likes) of the video.
Returns the numeric ID for the first audio stream in this file. Useful for the implementation of stream mappings etc; see "SReview::Map"
Returns the numeric ID for the first video stream in this file. Useful for the implementation of stream mappings etc; see "SReview::Map"
Add extra parameters. This should be used sparingly, rather add some abstraction.
| 2019-02-17 | perl v5.28.1 |