Cast: Avoid retransmit if we sent the same packet recently (less than RTT)

media/cast/audio_sender/audio_sender.cc

Index: media/cast/audio_sender/audio_sender.cc
diff --git a/media/cast/audio_sender/audio_sender.cc b/media/cast/audio_sender/audio_sender.cc
index 27b42d0dc8c2ac08757cb561d208f849c5835baa..6da7b9ad930bbdb757323699a21b994d030b23ee 100644
--- a/media/cast/audio_sender/audio_sender.cc
+++ b/media/cast/audio_sender/audio_sender.cc
@@ -106,7 +106,17 @@ void AudioSender::SendEncodedAudioFrame(
 void AudioSender::ResendPackets(
     const MissingFramesAndPacketsMap& missing_frames_and_packets) {
   DCHECK(cast_environment_->CurrentlyOn(CastEnvironment::MAIN));
-  transport_sender_->ResendPackets(true, missing_frames_and_packets, false);
+
+  base::TimeDelta rtt;
+  base::TimeDelta avg_rtt;
+  base::TimeDelta min_rtt;
+  base::TimeDelta max_rtt;
+  rtcp_.Rtt(&rtt, &avg_rtt, &min_rtt, &max_rtt);
+
+  // It would probably be better to use the 10% percentile rtt
+  // rather than the min.

[palmer, 2014/06/18 21:18:02]

File a bug to study this, so it doesn't get forgotten. (Maybe you already have
done so.) Then reference the bug # here.

[hubbe, 2014/06/18 21:20:35]

No real need, alpha is deep in that study right now..

+  transport_sender_->ResendPackets(
+      true, missing_frames_and_packets, false, rtt);

[Alpha Left Google, 2014/06/18 21:07:37]

Sorry one last thing I missed in the last review. I think it is best to leave
audio RTX untouched. Audio packets don't degrade performance as bad as video RTX
packets. And receiver currently only NACK once that means audio packet has at
most 2 chance to send. Removing the resend can lead to only once chance to send.

[hubbe, 2014/06/18 21:20:35]

Changed back to min_rtt

 }
 
 void AudioSender::IncomingRtcpPacket(scoped_ptr<Packet> packet) {