Fix timing frames and FEC conflict

webrtc/modules/rtp_rtcp/source/rtp_sender.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_sender.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender.cc b/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
index 0dfa062e3c0749ea14fba7eee7c9b2d74ad198bb..cdd707978165d3395a993389502c1eaa7935da0b 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender.cc
@@ -743,11 +743,8 @@ bool RTPSender::PrepareAndSendPacket(std::unique_ptr<RtpPacketToSend> packet,
   packet_to_send->SetExtension<AbsoluteSendTime>(

[brandtr, 2017/06/21 11:05:39]

Can you add a comment here, and below, describing what the problem is to change
these header extensions here? And why there's a difference between
AbsoluteSendTime and VideoTimingExtension.

[ilnik, 2017/06/21 11:17:18]

Done.

       AbsoluteSendTime::MsTo24Bits(now_ms));
 
-  // TODO(ilnik): (webrtc:7859) For now we can't modify pacer exit timestamp in
-  // video timing extension because only some packets have it and it will break
-  // FEC recovered packets, which will lead to corruptions. Ideally, here
-  // |packet->set_pacer_exit_time_ms(now_ms)| should be called if
-  // |VideoTimingExtension| is present.
+  if (packet_to_send->HasExtension<VideoTimingExtension>())
+    packet_to_send->set_pacer_exit_time_ms(now_ms);
 
   PacketOptions options;
   if (UpdateTransportSequenceNumber(packet_to_send, &options.packet_id)) {
@@ -836,11 +833,8 @@ bool RTPSender::SendToNetwork(std::unique_ptr<RtpPacketToSend> packet,
   if (packet->capture_time_ms() > 0) {
     packet->SetExtension<TransmissionOffset>(
         kTimestampTicksPerMs * (now_ms - packet->capture_time_ms()));
-    // TODO(ilnik): (webrtc:7859) For now we can't modify pacer exit timestamp
-    // in video timing extension because only some packets have it an it will
-    // break FEC recovered packets, which will lead to corruptions. Ideally,
-    // here |packet->set_pacer_exit_time_ms(now_ms)| should be called if
-    // |VideoTimingExtension| is present.
+    if (packet->HasExtension<VideoTimingExtension>())
+      packet->set_pacer_exit_time_ms(now_ms);
   }
   packet->SetExtension<AbsoluteSendTime>(AbsoluteSendTime::MsTo24Bits(now_ms));