Thanks for your bugreport and the detailed description. This problem was a missing codec in the autoinstall whitelist. I added it and this problem should be fixed now.
@Sebastian: your analysis is correc, having caps intersection would be really good. but it did not trigger this problem. Cheers, Michael ** Changed in: gst-plugins-bad-multiverse0.10 (Ubuntu) Status: Needs Info => Fix Committed -- MP4 video does not have sound after installation of codecs https://launchpad.net/bugs/89999 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs