this patch enables the use of the AAC and AC3 encoders in ffmpeg.
These are marked as experimental, yet they seem to be in widespread use
and all the information I could find on what makes them experimental is that
they create files with suboptimal quality per bitrate, i.e. for a given bitrate the quality
achieved could be better. This seems to be an issue only for lower bitrates, any
rates >160kbps seem to be transparent anyways.
Note: I have not tested the patch more than just quickly encoding one test file,
I don't have time to look at this longer unfortunately at the moment.