Currently mate-extra/mate-media-1.8.0[aac] depends on media-plugins/gst-plugins-ffmpeg. This, for some reason, requires <media-video/libav-10:0. Can this be bumped to media-video/libav-11? Reproducible: Always
In summary... Debian has a patch to support libav-11 but it breaks for older versions as it doesn't have the needed ifdefs to handle all versions :S *** This bug has been marked as a duplicate of bug 519258 ***