FFMPEG subtitles filter segfaults with matroska files

[Stephan Holljes]

Summary of the bug: FFMPEG crashes when trying to use the videofilter "subtitles" with matroska files that contain subtitle tracks.
How to reproduce: Encode a video with a the "subtitles" videofilter and use a matroska file as the subtitle file argument

% ffmpeg -i input ... outputffmpeg -i hataraku.mkv -c:a libmp3lame -c:v mpeg4 -sn -vf "subtitles=hataraku.mkv" -t 60 hataraku_hardsub.mkv

ffmpeg version N-52453-g12e3c1b Copyright (c) 2000-2013 the FFmpeg developers
  built on Apr 25 2013 00:02:29 with gcc 4.8.0 (GCC)
  configuration: --prefix=/home/klaxa/ffmpeg/build --disable-debug --disable-static --enable-avresample --enable-dxva2 --enable-fontconfig --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libv4l2 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-postproc --enable-runtime-cpudetect --enable-shared --enable-vdpau --enable-version3 --enable-x11grab
  libavutil      52. 27.100 / 52. 27.100
  libavcodec     55.  6.100 / 55.  6.100
  libavformat    55.  3.100 / 55.  3.100
  libavdevice    55.  0.100 / 55.  0.100
  libavfilter     3. 60.101 /  3. 60.101
  libavresample   1.  1.  0 /  1.  1.  0
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

I attached ffmpeg output with high log level, gdb output and valgrind output. Interestingly with valgrind ffmpeg does not segfault, but slowly proceeds to encode and produces the desired result, because of valgrind horribly slow though.

[Stephan Holljes]

log with ffmpeg -v 9 -loglevel 99

[Stephan Holljes]

gdb log with ffmpeg -v 9 -loglevel 99

[Stephan Holljes]

valgrind log

[Clément Bœsch]

Should be fixed in 035a3792c223d3b2bba79f38049bd6363b2d470d. Thanks for the report.