Moving src/webrtc into src/.

In order to eliminate the WebRTC Subtree mirror in Chromium, 
WebRTC is moving the content of the src/webrtc directory up
to the src/ directory.

NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
TBR=tommi@webrtc.org

Bug: chromium:611808
Change-Id: Iac59c5b51b950f174119565bac87955a7994bc38
Reviewed-on: https://webrtc-review.googlesource.com/1560
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19845}

modules/rtp_rtcp/source/flexfec_receiver.cc

@@ -0,0 +1,156 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/modules/rtp_rtcp/include/flexfec_receiver.h"
+
+#include "webrtc/rtc_base/logging.h"
+#include "webrtc/rtc_base/scoped_ref_ptr.h"
+
+namespace webrtc {
+
+namespace {
+
+using Packet = ForwardErrorCorrection::Packet;
+using ReceivedPacket = ForwardErrorCorrection::ReceivedPacket;
+
+// Minimum header size (in bytes) of a well-formed non-singular FlexFEC packet.
+constexpr size_t kMinFlexfecHeaderSize = 20;
+
+// How often to log the recovered packets to the text log.
+constexpr int kPacketLogIntervalMs = 10000;
+
+}  // namespace
+
+FlexfecReceiver::FlexfecReceiver(
+    uint32_t ssrc,
+    uint32_t protected_media_ssrc,
+    RecoveredPacketReceiver* recovered_packet_receiver)
+    : ssrc_(ssrc),
+      protected_media_ssrc_(protected_media_ssrc),
+      erasure_code_(
+          ForwardErrorCorrection::CreateFlexfec(ssrc, protected_media_ssrc)),
+      recovered_packet_receiver_(recovered_packet_receiver),
+      clock_(Clock::GetRealTimeClock()),
+      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)) {
+    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());
+  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;
+    }
+    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;
+    }
+    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;
+}
+
+// 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() {
+  RTC_DCHECK_CALLED_SEQUENTIALLY(&sequence_checker_);
+
+  // Decode.
+  if (!received_packets_.empty()) {
+    if (erasure_code_->DecodeFec(&received_packets_, &recovered_packets_) !=
+        0) {
+      return false;
+    }
+  }
+  // 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