Change ForwardErrorCorrection class to accept one received packet at a time.

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 30 matching lines @@
       last_recovered_packet_ms_(-1) {
   // It's OK to create this object on a different thread/task queue than
   // the one used during main operation.
   sequence_checker_.Detach();
 }
 
 FlexfecReceiver::~FlexfecReceiver() = default;
 
 void FlexfecReceiver::OnRtpPacket(const RtpPacketReceived& packet) {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&sequence_checker_);
-  if (!AddReceivedPacket(packet)) {
+  std::unique_ptr<ReceivedPacket> received_packet = AddReceivedPacket(packet);
+  if (!received_packet)
     return;
-  }
-  ProcessReceivedPackets();
+
+  ProcessReceivedPacket(*received_packet);
 }
 
 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) {
+std::unique_ptr<ReceivedPacket> 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());
   received_packet->seq_num = packet.SequenceNumber();
   received_packet->ssrc = packet.Ssrc();
   if (received_packet->ssrc == ssrc_) {
     // This is a FlexFEC packet.
     if (packet.payload_size() < kMinFlexfecHeaderSize) {
       LOG(LS_WARNING) << "Truncated FlexFEC packet, discarding.";
-      return false;
+      return nullptr;
     }
     received_packet->is_fec = true;
     ++packet_counter_.num_fec_packets;
 
     // Insert packet payload into erasure code.
     // TODO(brandtr): Remove this memcpy when the FEC packet classes
     // are using COW buffers internally.
     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;
+      return nullptr;
     }
     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));
   ++packet_counter_.num_packets;
 
-  return true;
+  return received_packet;
 }
 
 // Note that the implementation of this member function and the implementation
 // in UlpfecReceiver::ProcessReceivedFec() are slightly different.
 // This implementation only returns _recovered_ media packets through the
 // callback, whereas the implementation in UlpfecReceiver returns _all inserted_
 // media packets through the callback. The latter behaviour makes sense
 // for ULPFEC, since the ULPFEC receiver is owned by the RtpVideoStreamReceiver.
 // Here, however, the received media pipeline is more decoupled from the
 // FlexFEC decoder, and we therefore do not interfere with the reception
 // of non-recovered media packets.
-bool FlexfecReceiver::ProcessReceivedPackets() {
+void FlexfecReceiver::ProcessReceivedPacket(
+    const ReceivedPacket& received_packet) {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&sequence_checker_);
 
   // Decode.
-  if (!received_packets_.empty()) {
-    if (erasure_code_->DecodeFec(&received_packets_, &recovered_packets_) !=
-        0) {
-      return false;
-    }
-  }
+  erasure_code_->DecodeFec(received_packet, &recovered_packets_);
+
   // Return recovered packets through callback.
   for (const auto& recovered_packet : recovered_packets_) {
     if (recovered_packet->returned) {
       continue;
     }
     ++packet_counter_.num_recovered_packets;
     // Set this flag first, since OnRecoveredPacket may end up here
     // again, with the same packet.
     recovered_packet->returned = true;
     recovered_packet_receiver_->OnRecoveredPacket(
         recovered_packet->pkt->data, recovered_packet->pkt->length);
     // Periodically log the incoming packets.
     int64_t now_ms = clock_->TimeInMilliseconds();
     if (now_ms - last_recovered_packet_ms_ > kPacketLogIntervalMs) {
       uint32_t media_ssrc =
           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