i need it to build a synchronized audio/video player
a solution exist with Python, but it's stuck in a very old Raspbian version... and not compatible with Jessie (and also I don't know anything about Python :-) )
I would be curious to see this the code for this solution.
You can use GStreamer with some backend such as Clutter, or GTK+. They work very well. That requires a bit of coding, of course. I have a few of them under my Github user aalex. VLC is another higher-level option. (it's highly scriptable)