Fix timing frames and FEC conflict

webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 376 matching lines @@
     auto packet = last ? std::move(last_packet)
                        : rtc::MakeUnique<RtpPacketToSend>(*rtp_header);
     if (!packetizer->NextPacket(packet.get()))
       return false;
     RTC_DCHECK_LE(packet->payload_size(),
                   last ? max_data_payload_length - last_packet_reduction_len
                        : max_data_payload_length);
     if (!rtp_sender_->AssignSequenceNumber(packet.get()))
       return false;
 
+    bool protect_packet =
+            (packetizer->GetProtectionType() == kProtectedPacket);
     // Put packetization finish timestamp into extension.
     if (last && is_timing_frame) {
       packet->set_packetization_finish_time_ms(clock_->TimeInMilliseconds());
+      // TODO(ilnik): Due to webrtc:7859, packets with timing extensions are not
+      // protected by FEC. It reduces FEC efficiency a bit. When FEC is moved
+      // below the pacer, it can be re-enabled for these packets.
+      // NOTE: Any RTP stream processor in the network, modifying 'network'
+      // timestamps in the timing frames extension have to be an end-point for
+      // FEC, otherwise recovered by FEC packets will be corrupted.
+      protect_packet = false;
     }
 
-    const bool protect_packet =
-        (packetizer->GetProtectionType() == kProtectedPacket);
     if (flexfec_enabled()) {
       // TODO(brandtr): Remove the FlexFEC code path when FlexfecSender
       // is wired up to PacedSender instead.
       SendVideoPacketWithFlexfec(std::move(packet), storage, protect_packet);
     } else if (red_enabled) {
       SendVideoPacketAsRedMaybeWithUlpfec(std::move(packet), storage,
                                           protect_packet);
     } else {
       SendVideoPacket(std::move(packet), storage);
     }
@@ skipping 29 matching lines @@
   rtc::CritScope cs(&crit_);
   return retransmission_settings_;
 }
 
 void RTPSenderVideo::SetSelectiveRetransmissions(uint8_t settings) {
   rtc::CritScope cs(&crit_);
   retransmission_settings_ = settings;
 }
 
 }  // namespace webrtc