http://sei.meidokon.net/files/playback_fail.mkv

This is the first 10MB of a file that fails completely to playback in GStreamer. Totem properly shows the video information, but detects no audio (it should be FLAC). MPlayer has no problems dealing with it.

Further poking reveals some kind of generalised failure somewhere. The GNOME file properties dialogue never comes up, and feeding it to playbin with gst-launch the pipeline fails to PREROLL properly and never goes into PLAYING:

Setting pipeline to PAUSED ...
/GstPlayBin:playbin0/GstDecodeBin:decodebin0/GstTypeFindElement:typefind.GstPad:src: caps = video/x-matroska
Pipeline is PREROLLING ...
/GstPlayBin:playbin0/GstDecodeBin:decodebin0/GstMatroskaDemux:matroskademux0.GstPad:sink: caps = video/x-matroska

[...]

/GstPlayBin:playbin0/GstBin:textbin/GstBin:vbin/GstAutoVideoSink:videosink.GstGhostPad:sink.GstProxyPad:proxypad7: caps = video/x-raw-yuv, width=(int)720, height=(int)480, framerate=(fraction)1000000000/41708333, format=(fourcc)I420, interlaced=(boolean)false, pixel-aspect-ratio=(fraction)1/1
^CCaught interrupt -- handling interrupt.
Interrupt: Stopping pipeline ...
ERROR: pipeline doesn't want to preroll.

Version info for core packages:

gstreamer0.10-ffmpeg                     0.10.10-1
gstreamer0.10-plugins-bad                0.10.18-1ubuntu1
gstreamer0.10-plugins-bad-multiverse     0.10.18-0ubuntu1
gstreamer0.10-plugins-base               0.10.28-1
gstreamer0.10-plugins-good               0.10.21-1ubuntu2
gstreamer0.10-plugins-ugly               0.10.14-1
gstreamer0.10-plugins-ugly-multiverse    0.10.14-0ubuntu1
libgstreamer0.10-0                       0.10.28-1