VobSub rendering error

[aphirst]

Affected video file.

Play the file with mpv gundam_unicorn.mp4 --sid=2 --start=8, and observe the subtitles.

Expected output: VLC
Instead: mpv

I recall discussing this with wm4 on IRC a little while ago, and if I remember correctly the reason that it works in VLC is that it implements its own demuxer(?).

• mpv from git, also in releases since at least 0.3.0
• ffmpeg 2.1.3, but also for at least a few minor releases back

Note that it "sometimes" works with Libav. The issue might be in libavformat's mp4 demuxer not returning the vobsub codec data required to display the subtitle correctly.

I installed debian's mpv binary, and somehow it works there. It works even with mixed ffmpeg libraries:

mpv 0.3.5 (C) 2000-2013 mpv/MPlayer/mplayer2 projects
 built on 2014-02-12T22:36:40
libav library versions:
   libavutil       52.3.0 (runtime 52.48.101)
   libavcodec      54.35.0 (runtime 54.92.100)
   libavformat     54.20.3 (runtime 54.63.104)
   libswscale      2.1.1 (runtime 2.5.101)
   libavfilter     3.3.0 (runtime 3.90.100)
   libavresample   1.0.1 (runtime 1.1.0)

Quite trippy...

Built mpv-build, but with the latest Libav release, v9.11. It works.

mpv 0.3.5-git-76d771a (C) 2000-2013 mpv/MPlayer/mplayer2 projects
 built on 2014-02-13T17:25:58
libav library versions:
   libavutil       52.3.0
   libavcodec      54.35.0
   libavformat     54.20.3
   libswscale      2.1.1
   libavresample   1.0.1

With the latest ffmpeg release, n2.1.3, it's broken.

mpv 0.3.5-git-76d771a (C) 2000-2013 mpv/MPlayer/mplayer2 projects
 built on 2014-02-13T17:36:56
ffmpeg library versions:
   libavutil       52.48.101
   libavcodec      55.39.101
   libavformat     55.19.104
   libswscale      2.5.101
   libavfilter     3.90.100
   libavresample   1.1.0

[ghedo]

Incidentally, it's also broken with libav10 (from Debian experimental).

mpv 0.3.5 (C) 2000-2013 mpv/MPlayer/mplayer2 projects
 built on 2014-02-12T22:13:09
libav library versions:
   libavutil       53.2.0
   libavcodec      55.32.0
   libavformat     55.10.3
   libswscale      2.1.2
   libavfilter     4.1.0
   libavresample   1.1.0

Yep, just tried with Libav master, and it was broken.

mpv 0.3.5-git-76d771a (C) 2000-2013 mpv/MPlayer/mplayer2 projects
 built on 2014-02-13T17:45:13
libav library versions:
   libavutil       53.2.0
   libavcodec      55.34.0
   libavformat     55.12.0
   libswscale      2.1.2
   libavfilter     4.1.0
   libavresample   1.1.0

775253278914d82ca3598b2d48e4ce0c6e05452a is the first bad commit
commit 775253278914d82ca3598b2d48e4ce0c6e05452a
Author: Rémi Denis-Courmont <remi@remlab.net>
Date:   Sat Jan 12 17:53:47 2013 +0200

    vdpau: Add VC-1 decoding via hwaccel infrastructure

    Signed-off-by: Diego Biurrun <diego@biurrun.de>

:100755 100755 c62ea2d803b96f957bcec355e63a98c1bc429777 a2bf6e186af2fd2c4c16c9db79fb498383241b4a M  configure
:040000 040000 4cf379373b9fdbb25cc5f31e7c6da1392b622829 6836808a82826d61c7ad471a1081424924a5de37 M  libavcodec

Actually the same result I got last time. I have no clue why.

OK... it's because that commit bumps the libavcodec version, and the libavcodec version is checked somewhere in the subtitle code. So what happens is that the version bump makes mpv use the libavcodec vobsub decoder (sd_lavc), instead of the old mplayer one (sd_spu). And it appears the old mplayer decoder has saner defaults that make it display this file correctly (probably by coincidence). The following patch would fix it; however I actually wanted to get rid of the old mplayer decoder.

diff --git a/sub/dec_sub.c b/sub/dec_sub.c
index 46c5b3f..43876cc 100644
--- a/sub/dec_sub.c
+++ b/sub/dec_sub.c
@@ -46,8 +46,8 @@ static const struct sd_functions *sd_list[] = {
 #if HAVE_LIBASS
     &sd_ass,
 #endif
-    &sd_lavc,
     &sd_spu,
+    &sd_lavc,
     &sd_movtext,
     &sd_srt,
     &sd_microdvd,

Should be fixed properly now.