Not able to get audio caps for mp4

[Marc Leeman]

> I can successfully stream the video but I am not able get the audio.

That is probably because I removed the audio part in the examples :-)

Combine your first example with these pipelines and andjust where
needed for the audio codec. Make certain you use elements with the
correct caps (add -v to gst-launch) and double check with gst-inspect
on the elements.

You will probably not have the same issue than with mpeg4 and h264
(they are close and the typefind does not pick it up).