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Some MKV videos are not working and I get this message:
Could not find GStreamer caps mapping for FFmpeg codec 'h264', and you are using an external libavcodec. This is most likely due to a packaging problem and/or libavcodec having been upgraded to a version that is not compatible with this version of gstreamer-ffmpeg. Make sure your gstreamer-ffmpeg and libavcodec packages come from the same source/repository.
How can I fix the
gstreamer-ffmpeg issue in Ubuntu 12.04?
These videos are working with VLC, but I rather use the Totem player as it is much more responsive.