Comment 22 for bug 1183829

I got the exact same bug on 14.04 - 64bits.

The problem comes from issue into GStreamer.
By default it uses libgstmusepack.so (in /usr/lib/x86_64-linux-gnu/gstreamer-0.10) to decode MPC. But the plugin is not working so it can't decode the file.

I have moved the file to my home directory to make it unreachable by gstreamer. So, Gstreamer is forced to use a better plugins (perhaps gstreamer-ffmpeg) to decode the mpc and it works.

So if the application build is own pipeline using gstreamer-ffmpeg or gstreamer-libav, there is no need to move/delete the file. But, if your application takes the gstreamer autogenerated pipeline it will lead you into issue.

The following command [gst-launch-0.10 filesrc location=123.mpc ! decodebin ! audioconvert ! audioresample ! autoaudiosink] asks to decodebin to build the decode pipeline. So, after the move of libgstmusepack.so, the decodebin build a pipeline without libgstmusepack.so. Make it working.

As Qt application use gstreamer built pipeline, we are falling in the bug.

I got some interesting hint in the page: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=671794