[Bug 776902] New: [matroska-mux] Produces corrupted files with empty tracks

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=776902

            Bug ID: 776902
           Summary: [matroska-mux] Produces corrupted files with empty
                    tracks
    Classification: Platform
           Product: GStreamer
           Version: unspecified
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: sancane.kurento at gmail.com
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

It seems that there is a bug when generating the muxer headers when an EOS is
received and not media has been processed previously.

You can try this issue with gst-launch:
$GST_DEBUG=2 gst-launch-1.0 videotestsrc num-buffers=0 ! x264enc ! .video_0
matroskamux ! filesink sync=FALSE async=FALSE location="file.mkv"

0:00:00.032486501 30736      0x24c3370 WARN             matroskamux
matroska-mux.c:3333:gst_matroska_mux_finish:0x24c4a00 unable to get final track
duration

The resulting file.mkv is a not playable file:
$gst-play-1.5 file.mkv 
Press 'k' to see a list of keyboard shortcuts.
Now playing /home/sancane/twilio/sources/vms-media-server/build/file.mkv
0:00:00.026630030 30784 0x7fae40130990 ERROR               ebmlread
ebml-read.c:152:gst_ebml_peek_id_length:<matroskademux0> Invalid EBML ID size
tag (0x0) at position 244 (0xf4)
0:00:00.026777265 30784 0x7fae40130990 ERROR              decodebin
gstdecodebin2.c:3069:no_more_pads_cb:<decodebin0> can't find group for element

ffprobe gives next info:
$ ffprobe file.mkv 
ffprobe version 2.8.10-0ubuntu0.16.04.1 Copyright (c) 2007-2016 the FFmpeg
developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1
--build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu
--incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl
--enable-shared --disable-stripping --disable-decoder=libopenjpeg
--disable-decoder=libschroedinger --enable-avresample --enable-avisynth
--enable-gnutls --enable-ladspa --enable-libass --enable-libbluray
--enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite
--enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme
--enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg
--enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger
--enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex
--enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis
--enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265
--enable-libxvid --enable-libzvbi --enable-openal --enable-opengl
--enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq
--enable-frei0r --enable-libx264 --enable-libopencv
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
  libpostproc    53.  3.100 / 53.  3.100
[matroska,webm @ 0x17e9c80] Read error at pos. 245 (0xf5)
[matroska,webm @ 0x17e9c80] Duplicate element
[matroska,webm @ 0x17e9c80] Read error at pos. 77 (0x4d)
[matroska,webm @ 0x17e9c80] Read error at pos. 105 (0x69)
[matroska,webm @ 0x17e9c80] Duplicate element
[matroska,webm @ 0x17e9c80] Read error at pos. 245 (0xf5)
[matroska,webm @ 0x17e9c80] Duplicate element
    Last message repeated 1 times
file.mkv: End of file

I'm not familiarized with matroska, but perhaps one could expect not to display
anything when trying to play a video like this instead of getting this amount
of errors, I mean, an empty media file should not have to end up with these
errors, they simply should play nothing because they contain nothing. Don't
they?

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