Multimedia container file system.
Someday this might end up as a 9p filesystem for various video container formats so other programs (vidya players) can identify formats and extract streams properly.
extra/ contains additional tools:
video/adtsdump, to dump ADTS headers in human readable form.
video/mkvdump, to dump MKV in human readable form.
video/ivf2raw, to rip raw video frames out of IVF.
It's not a filesystem yet, but it can extract subtitles, video streams (as IVF, some as OGG) and audio streams from MP4 and MKV.