rtpsession: Delay the next regular RTCP packet after early RTCP

This is required to not exceed the short term average RTCP bitrate when
using early feedback as compared to without early feedback.

diff --git a/gst/rtpmanager/rtpsession.c b/gst/rtpmanager/rtpsession.c
index a216cd9..2c49fb1 100644 (file)
--- a/gst/rtpmanager/rtpsession.c
+++ b/gst/rtpmanager/rtpsession.c
@@ -3791,7 +3791,7 @@ gboolean
 rtp_session_request_early_rtcp (RTPSession * sess, GstClockTime current_time,
     GstClockTime max_delay)
 {
-  GstClockTime T_dither_max;
+  GstClockTime T_dither_max, T_rr;
   gboolean ret;
 
   /* Implements the algorithm described in RFC 4585 section 3.5.2 */
@@ -3812,6 +3812,8 @@ rtp_session_request_early_rtcp (RTPSession * sess, GstClockTime current_time,
     goto end;
   }
 
+  T_rr = sess->next_rtcp_check_time - sess->last_rtcp_send_time;
+
   /*  RFC 4585 section 3.5.2 step 2b */
   /* If the total sources is <=2, then there is only us and one peer */
   /* When there is one auxiliary stream the session can still do point
@@ -3821,7 +3823,7 @@ rtp_session_request_early_rtcp (RTPSession * sess, GstClockTime current_time,
     T_dither_max = 0;
   } else {
     /* Divide by 2 because l = 0.5 */
-    T_dither_max = sess->next_rtcp_check_time - sess->last_rtcp_send_time;
+    T_dither_max = T_rr;
     T_dither_max /= 2;
   }
 
@@ -3861,8 +3863,11 @@ rtp_session_request_early_rtcp (RTPSession * sess, GstClockTime current_time,
 
   /*  RFC 4585 section 3.5.2 step 6 */
   sess->allow_early = FALSE;
-  /* TODO(mparis): "R MUST recalculate tn = tp + 2*T_rr,
-   * and MUST set tp to the previous tn" */
+  /* Delay next regular RTCP packet to not exceed the short-term
+   * RTCP bandwidth when using early feedback as compared to
+   * without */
+  sess->next_rtcp_check_time = sess->last_rtcp_send_time + 2 * T_rr;
+  sess->last_rtcp_send_time += T_rr;
 
   GST_LOG_OBJECT (sess, "next early RTCP time %" GST_TIME_FORMAT,
       GST_TIME_ARGS (sess->next_early_rtcp_time));