How to create an audio stream using mpeg4 liquidsoap + icecast? We do not want to use a third-party utility such as ffmpeg, can we do it only on liquidsoap? Thank you!
Liquidsoap can play mp4 as long as you have the appropriate libraries compiled in your liquidsoap installation.
The library you probably want is ocaml-faad.
If its not in your liquidsoap installation you can compile liquidsoap from source. Be sure that ocaml-faad is uncommented in the PACKAGES file.
https://github.com/savonet/liquidsoap-full/blob/master/PACKAGES.default#L93
You can try playing a static playlist of mpeg4 files: http://savonet.sourceforge.net/doc-svn/reference.html#playlist
or a single file: http://savonet.sourceforge.net/doc-svn/reference.html#single
Hope that helps!