y4mdec: Parse extended headers written out by FFmpeg
References:
https://wiki.multimedia.cx/index.php/YUV4MPEG2
https://github.com/FFmpeg/FFmpeg/blob/eee3b7e2/libavformat/yuv4mpegenc.c#L74-L166
You can get sample media for testing in various places, such as https://opencontent.netflix.com/
The primary purpose was to add high bit-depth y4m support, which is commonly used for testing codecs.
Edited by Nirbheek Chauhan