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References: https://wiki.multimedia.cx/index.php/YUV4MPEG2 https://github.com/FFmpeg/FFmpeg/blob/eee3b7e2/libavformat/yuv4mpegenc.c#L74-L166 The primary purpose is to add high bit-depth y4m support, which is commonly used for testing codecs. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5997>