Protected streams report RTP messages directly to the FlexFec streams

webrtc/modules/rtp_rtcp/source/flexfec_receiver.cc

 /*
  *  Copyright (c) 2016 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 41 matching lines @@
     return;
   }
   ProcessReceivedPackets();
 }
 
 FecPacketCounter FlexfecReceiver::GetPacketCounter() const {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&sequence_checker_);
   return packet_counter_;
 }
 
+// TODO(eladalon): Consider using packet.recovered() to avoid processing
+// recovered packets here.
 bool FlexfecReceiver::AddReceivedPacket(const RtpPacketReceived& packet) {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&sequence_checker_);
 
   // RTP packets with a full base header (12 bytes), but without payload,
   // could conceivably be useful in the decoding. Therefore we check
   // with a non-strict inequality here.
   RTC_DCHECK_GE(packet.size(), kRtpHeaderSize);
 
   // Demultiplex based on SSRC, and insert into erasure code decoder.
   std::unique_ptr<ReceivedPacket> received_packet(new ReceivedPacket());
@@ skipping 14 matching lines @@
     received_packet->pkt = rtc::scoped_refptr<Packet>(new Packet());
     auto payload = packet.payload();
     memcpy(received_packet->pkt->data, payload.data(), payload.size());
     received_packet->pkt->length = payload.size();
   } else {
     // This is a media packet, or a FlexFEC packet belonging to some
     // other FlexFEC stream.
     if (received_packet->ssrc != protected_media_ssrc_) {
       return false;
     }
+    // TODO(eladalon): It seems like, because of return-statement above,

[danilchap, 2017/07/24 15:37:25]

received_packet is a local variable: if return above, it will be destroyed.
only below it is pushed into member variable for later use.

[eladalon, 2017/07/24 15:53:55]

Right you are. Looks like I was confused between |received_packet| and |packet|
(which is const) when I filed this bug. At least, that's one theory for the
mistake.

+    // it could be that nobody ever ends up updating |is_fec|. Specifically,
+    // it seems like a media packet would never be set to |is_fec=false|
+    // if there is no FlexFEC stream protecting it.
+    // https://bugs.chromium.org/p/webrtc/issues/detail?id=7954
     received_packet->is_fec = false;
 
     // Insert entire packet into erasure code.
     // TODO(brandtr): Remove this memcpy too.
     received_packet->pkt = rtc::scoped_refptr<Packet>(new Packet());
     memcpy(received_packet->pkt->data, packet.data(), packet.size());
     received_packet->pkt->length = packet.size();
   }
 
   received_packets_.push_back(std::move(received_packet));
@@ skipping 39 matching lines @@
           ForwardErrorCorrection::ParseSsrc(recovered_packet->pkt->data);
       LOG(LS_VERBOSE) << "Recovered media packet with SSRC: " << media_ssrc
                       << " from FlexFEC stream with SSRC: " << ssrc_ << ".";
       last_recovered_packet_ms_ = now_ms;
     }
   }
   return true;
 }
 
 }  // namespace webrtc