Support Chinese AVS2/AVS3 inside mkv container

[AntarcticanWaffles]

This got requested a few years ago, things have changed and now mpv built with the correct libraries (libdavs2 and libuavs3d) can play avs2 and avs3 video inside the mpeg .ts format, but it cannot play videos in the mkv container.

Ffplay can play these files, i got them from https://github.com/xatabhk/avs2-avs3-video-samples.

> mpv.com .\test5_avs2.mkv
[mkv] Unknown/unsupported CodecID (V_AVS2) or missing/bad CodecPrivate data (track 1).
 (+) Video --vid=1 (*) ( 1024x576 24.000fps)
 (+) Audio --aid=1 (*) (aac 2ch 48000Hz)
     Audio --aid=2 --alang=eng 'Commentary' (aac 1ch 22050Hz)
 (+) Subs  --sid=1 --slang=eng (*) (ass)
     Subs  --sid=2 --slang=hun (ass)
     Subs  --sid=3 --slang=ger (ass)
     Subs  --sid=4 --slang=fre (ass)
     Subs  --sid=5 --slang=spa (ass)
     Subs  --sid=6 --slang=ita (ass)
     Subs  --sid=7 --slang=jpn (ass)
     Subs  --sid=8 (ass)
File tags:
 Comment: Matroska Validation File 8, secondary audio commentary track, misc subtitle tracks
 Title: Big Buck Bunny - test 8
Failed to initialize a decoder for codec ''.
Video: no video

Exiting... (Errors when loading file)

MPV version:

mpv 0.34.0-485-g6b9b032d51 Copyright © 2000-2022 mpv/MPlayer/mplayer2 projects
 built on Tue Sep 27 09:18:09 AEST 2022
FFmpeg library versions:
   libavutil       57.37.100
   libavcodec      59.48.100
   libavformat     59.33.100
   libswscale      6.8.112
   libavfilter     8.49.100
   libswresample   4.9.100
FFmpeg version: N-108376-g15f0d00b06-g179830108d+3

[BlueSwordM]

This isn't really an mpv request. You should instead talk with the Matroska dev to include support for such formats.

[CounterPillow]

No it is an mpv request, we keep a list of known codec IDs that needs to be updated.

[BlueSwordM]

Indeed. In fact, as noted on IRC by JEEB, AVS2 and AVS3 is indeed supported by the Matroska spec.