Cast: Better redundancy for receiver RTCP events

Previously we always take the latest RTCP events from
ReceiverRtcpEventSubscriber (without clearing explicitly) and stuff the
packet with at most 200 bytes of data. This patch reintroduces the
resetting of ReceiverRtcpEventSubscriber map when data is read from it,
and it will be used as follows:

- Get data from ReceiverRtcpEventSubscriber and reset its map
- (Same as before) Impose 200 byte limit on rtcp receiver logs
- Fill packet with data
- Push a copy of data to redundancy buffer in RtcpSender
- If there is enough space left, fill packet with data that was used
  X_1 receiver logs ago
- If there is enough space left, fill packet with data that was used
  X_2 receiver logs ago
-- Where 0 < X_1 < X_2 <= B where B is the buffer size.
- Truncate buffer to discard old receiver logs if necessary.

This gives a more consistent redudancy factor of 3 for each event.
In here, X_1 = 10, X_2 = B = 20. So an event will be sent at reports
N, N+10, and N+20.


Additional items:
- fix ssrc mismatch in receiver app.
- removed unused function in cast_sender.{h,cc}.


BUG=349265

Review URL: https://codereview.chromium.org/203293009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@261921 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 3 insertions, 1 deletions

diff --git a/media/cast/audio_receiver/audio_receiver.cc b/media/cast/audio_receiver/audio_receiver.cc
index b214c52..b01a54f 100644
--- a/media/cast/audio_receiver/audio_receiver.cc
+++ b/media/cast/audio_receiver/audio_receiver.cc
@@ -271,7 +271,9 @@ void AudioReceiver::CastFeedback(const RtcpCastMessage& cast_message) {
   cast_environment_->Logging()->InsertFrameEvent(
       now, kAudioAckSent, rtp_timestamp, cast_message.ack_frame_id_);
 
-  rtcp_.SendRtcpFromRtpReceiver(&cast_message, &event_subscriber_);
+  ReceiverRtcpEventSubscriber::RtcpEventMultiMap rtcp_events;
+  event_subscriber_.GetRtcpEventsAndReset(&rtcp_events);
+  rtcp_.SendRtcpFromRtpReceiver(&cast_message, &rtcp_events);
 }
 
 base::TimeTicks AudioReceiver::GetPlayoutTime(base::TimeTicks now,