Comment 3 for bug 1310554

From what I understand this is caused by the removal of ffmpeg, replaced by libav (a fork) : http://askubuntu.com/questions/432542/is-ffmpeg-missing-from-the-official-repositories-in-14-04

For gmusicbrowser, the problem is that is uses gstreamer 0.10 which uses gstreamer0.10-ffmpeg to decode mpc (and lossless m4a too, probably more) which doesn't compile with libav, so it has been removed (https://bugs.launchpad.net/ubuntu/+source/gallery-app/+bug/1254033) as gstreamer 0.10 is deprecated in favor of 1.0

I've installed ffmpeg and gstreamer0.10-ffmpeg via the ppa mentioned in the askubuntu question above, and it does fix the playing of mpc and lossless m4a in gmusicbrowser, the ppa also contains a vlc that plays mpc. Of course it is not a proper fix