To decode m4a file (QT files with AAC inside), gstreamer needs the the faad plugin (which is already required), but also the QT demuxer (qtdemux) which is currently part of the gst-plugins-bad packages. So please add gst-plugins-bad as a dep if the aac flag is set (or maybe make it into a separate package).
gst-plugins-faad inherits the gst-plugins-bad eclass which should install the gst-plugins-bad package. It looks like the problem is that qtdemux is commented out of the plugins installed by the eclass. Maybe something for gstreamer herd to look at.
The gst-plugins-bad eclass does not make the plugin inheriting it dep on gst-plugins-bad. media-libs/gst-plugins-bad installs qtdemux. So make your app dep on that if you want iso/mov/mp4 demuxing.
The original bug was that rhythmbox 0.9.x should depend on gst-plugins-bad if AAC flag is set... and this is not fixed. I'm restoring the initial summary.. And since rhtyhmbox is a shared gnome/gstreamer/sound herds maintenance, one of you has to fix it (otherwise I will..)
No need to be snippy. It was an honest mistake. Such a dep cannot be added, as ia64 has rhythmbox keyworded, but not gst-plugins-bad. ia64: Can you keyword gst-plugins-bad? Or mask the aac flag? Or should we drop keywords from rhythmbox?
I will look at this later tonight. Right now depping on any -bad plugins means rhythmbox will never be able to get marked stable because gstreamer herd will never mark bad plugins as stable. Since these plugins aren't required for rhythmbox to run...it isn't needed to dep on them even in a use? case. tester or anybody else: do you have any comments on that? Would you prefer a note at the end explaining this and giving instructions on what plugins to install(or pointing to a gst-doc if there is a good one) or to just have it stay ~arch and add the dep?
For me both situations are fine. Just if you opt for the note, remove the AAC use flag and have a note saying that you need the bad and faad plugins for m4a playback to work.
I have removed the aac use flag and added an elog message at the end of the ebuild to inform users of this issue. Zaheer tells me that eventually there will be support in gstreamer to detect missing plugins and offer to install them via your distro so hopefully these issues won't happen again.