rtpsession: feedback rtcp queue grows indefinitely until session end

Submitted by Jason Litzinger

Link to original bug (#739985)

Description

In short, when an rtcp feedback packet is received, it is queued based on the value of rtcp_feedback_retention_window, which defaults to 2 seconds. The queue is pruned periodically in rtp_source_timeout() according to:

while ((pkt = g_queue_peek_tail (src->retained_feedback)) &&
GST_BUFFER_TIMESTAMP (pkt) < feedback_retention_window)
gst_buffer_unref (g_queue_pop_tail (src->retained_feedback));

The problem is that the buffer timestamp, set when queued, comes from the packet info's running time field:

rtp_session_process_feedback():
<snip>
rtp_source_retain_rtcp_packet (src, packet, pinfo->running_time)

And is initialized in rtp_session_process_rtcp() with -1:

update_packet_info (sess, &pinfo, FALSE, FALSE, FALSE, buffer, current_time,
-1, ntpnstime);

In a setup with a high quantity of NACKs, this results in a queue of significant size.

It seems like pinfo->current_time might be a better field to use for the buffer timestamp, but that's speculation on my part.

Version: 1.4.4