add on_action_suggested callback for qos analyser which receive input and output (decision) of the algorithm

Allow these filter to specify if they support non-YUV420P
format (e.g: YUYV). If true, feed them with this format instead
of using pixconv.

If some incomplete VP8 frame is left after an iteration of vp8rtpfmt_unpacker_process, keep them for next iteration.

disconnect callbacks from rtp session when AudioStream is destroyed, otherwise they remain in the rtp session, which is kept for further updates of the session (reINVITE)

add update method in qos analyser interface for burst management/bandwidth computation in stateful qos

This mechanism is now handled in oRTP by using the RTCP send algorithm defined in the RFC 3550.