modules/rtp_rtcp/source/ulpfec_receiver_impl.cc - src - Git at Google

 /*
  *  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.
  */

 #include "modules/rtp_rtcp/source/ulpfec_receiver_impl.h"

 #include <memory>
 #include <utility>

 #include "api/scoped_refptr.h"
 #include "modules/rtp_rtcp/source/rtp_packet_received.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/time_utils.h"

 namespace webrtc {

 std::unique_ptr<UlpfecReceiver> UlpfecReceiver::Create(
     uint32_t ssrc,
     RecoveredPacketReceiver* callback,
     rtc::ArrayView<const RtpExtension> extensions) {
   return std::make_unique<UlpfecReceiverImpl>(ssrc, callback, extensions);
 }

 UlpfecReceiverImpl::UlpfecReceiverImpl(
     uint32_t ssrc,
     RecoveredPacketReceiver* callback,
     rtc::ArrayView<const RtpExtension> extensions)
     : ssrc_(ssrc),
       extensions_(extensions),
       recovered_packet_callback_(callback),
       fec_(ForwardErrorCorrection::CreateUlpfec(ssrc_)) {}

 UlpfecReceiverImpl::~UlpfecReceiverImpl() {
   received_packets_.clear();
   fec_->ResetState(&recovered_packets_);
 }

 FecPacketCounter UlpfecReceiverImpl::GetPacketCounter() const {
   rtc::CritScope cs(&crit_sect_);
   return packet_counter_;
 }

 //     0                   1                    2                   3
 //     0 1 2 3 4 5 6 7 8 9 0 1 2 3  4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //    |F|   block PT  |  timestamp offset         |   block length    |
 //    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //
 //
 // RFC 2198          RTP Payload for Redundant Audio Data    September 1997
 //
 //    The bits in the header are specified as follows:
 //
 //    F: 1 bit First bit in header indicates whether another header block
 //        follows.  If 1 further header blocks follow, if 0 this is the
 //        last header block.
 //        If 0 there is only 1 byte RED header
 //
 //    block PT: 7 bits RTP payload type for this block.
 //
 //    timestamp offset:  14 bits Unsigned offset of timestamp of this block
 //        relative to timestamp given in RTP header.  The use of an unsigned
 //        offset implies that redundant data must be sent after the primary
 //        data, and is hence a time to be subtracted from the current
 //        timestamp to determine the timestamp of the data for which this
 //        block is the redundancy.
 //
 //    block length:  10 bits Length in bytes of the corresponding data
 //        block excluding header.

 bool UlpfecReceiverImpl::AddReceivedRedPacket(const RtpPacket& rtp_packet,
                                               uint8_t ulpfec_payload_type) {
   if (rtp_packet.Ssrc() != ssrc_) {
     RTC_LOG(LS_WARNING)
         << "Received RED packet with different SSRC than expected; dropping.";
     return false;
   }
   if (rtp_packet.size() > IP_PACKET_SIZE) {
     RTC_LOG(LS_WARNING) << "Received RED packet with length exceeds maximum IP "
                            "packet size; dropping.";
     return false;
   }
   rtc::CritScope cs(&crit_sect_);

   static constexpr uint8_t kRedHeaderLength = 1;

   if (rtp_packet.payload_size() == 0) {
     RTC_LOG(LS_WARNING) << "Corrupt/truncated FEC packet.";
     return false;
   }

   // Remove RED header of incoming packet and store as a virtual RTP packet.
   auto received_packet =
       std::make_unique<ForwardErrorCorrection::ReceivedPacket>();
   received_packet->pkt = new ForwardErrorCorrection::Packet();

   // Get payload type from RED header and sequence number from RTP header.
   uint8_t payload_type = rtp_packet.payload()[0] & 0x7f;
   received_packet->is_fec = payload_type == ulpfec_payload_type;
   received_packet->ssrc = rtp_packet.Ssrc();
   received_packet->seq_num = rtp_packet.SequenceNumber();

   if (rtp_packet.payload()[0] & 0x80) {
     // f bit set in RED header, i.e. there are more than one RED header blocks.
     // WebRTC never generates multiple blocks in a RED packet for FEC.
     RTC_LOG(LS_WARNING) << "More than 1 block in RED packet is not supported.";
     return false;
   }

   ++packet_counter_.num_packets;
   packet_counter_.num_bytes += rtp_packet.size();
   if (packet_counter_.first_packet_time_ms == -1) {
     packet_counter_.first_packet_time_ms = rtc::TimeMillis();
   }

   if (received_packet->is_fec) {
     ++packet_counter_.num_fec_packets;
     // everything behind the RED header
     received_packet->pkt->data =
         rtp_packet.Buffer().Slice(rtp_packet.headers_size() + kRedHeaderLength,
                                   rtp_packet.payload_size() - kRedHeaderLength);
   } else {
     auto red_payload = rtp_packet.payload().subview(kRedHeaderLength);
     received_packet->pkt->data.EnsureCapacity(rtp_packet.headers_size() +
                                               red_payload.size());
     // Copy RTP header.
     received_packet->pkt->data.SetData(rtp_packet.data(),
                                        rtp_packet.headers_size());
     // Set payload type.
     received_packet->pkt->data[1] &= 0x80;          // Reset RED payload type.
     received_packet->pkt->data[1] += payload_type;  // Set media payload type.
     // Copy payload data.
     received_packet->pkt->data.AppendData(red_payload.data(),
                                           red_payload.size());
   }

   if (received_packet->pkt->data.size() > 0) {
     received_packets_.push_back(std::move(received_packet));
   }
   return true;
 }

 // TODO(nisse): Drop always-zero return value.
 int32_t UlpfecReceiverImpl::ProcessReceivedFec() {
   crit_sect_.Enter();

   // If we iterate over |received_packets_| and it contains a packet that cause
   // us to recurse back to this function (for example a RED packet encapsulating
   // a RED packet), then we will recurse forever. To avoid this we swap
   // |received_packets_| with an empty vector so that the next recursive call
   // wont iterate over the same packet again. This also solves the problem of
   // not modifying the vector we are currently iterating over (packets are added
   // in AddReceivedRedPacket).
   std::vector<std::unique_ptr<ForwardErrorCorrection::ReceivedPacket>>
       received_packets;
   received_packets.swap(received_packets_);

   for (const auto& received_packet : received_packets) {
     // Send received media packet to VCM.
     if (!received_packet->is_fec) {
       ForwardErrorCorrection::Packet* packet = received_packet->pkt;
       crit_sect_.Leave();
       recovered_packet_callback_->OnRecoveredPacket(packet->data.data(),
                                                     packet->data.size());
       crit_sect_.Enter();
       // Create a packet with the buffer to modify it.
       RtpPacketReceived rtp_packet;
       const uint8_t* const original_data = packet->data.cdata();
       if (!rtp_packet.Parse(packet->data)) {
         RTC_LOG(LS_WARNING) << "Corrupted media packet";
       } else {
         rtp_packet.IdentifyExtensions(extensions_);
         // Reset buffer reference, so zeroing would work on a buffer with a
         // single reference.
         packet->data = rtc::CopyOnWriteBuffer(0);
         rtp_packet.ZeroMutableExtensions();
         packet->data = rtp_packet.Buffer();
         // Ensure that zeroing of extensions was done in place.
         RTC_DCHECK_EQ(packet->data.cdata(), original_data);
       }
     }
     fec_->DecodeFec(*received_packet, &recovered_packets_);
   }

   // Send any recovered media packets to VCM.
   for (const auto& recovered_packet : recovered_packets_) {
     if (recovered_packet->returned) {
       // Already sent to the VCM and the jitter buffer.
       continue;
     }
     ForwardErrorCorrection::Packet* packet = recovered_packet->pkt;
     ++packet_counter_.num_recovered_packets;
     // Set this flag first; in case the recovered packet carries a RED
     // header, OnRecoveredPacket will recurse back here.
     recovered_packet->returned = true;
     crit_sect_.Leave();
     recovered_packet_callback_->OnRecoveredPacket(packet->data.data(),
                                                   packet->data.size());
     crit_sect_.Enter();
   }

   crit_sect_.Leave();
   return 0;
 }

 }  // namespace webrtc
	/*
	* 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.
	*/

	#include "modules/rtp_rtcp/source/ulpfec_receiver_impl.h"

	#include <memory>
	#include <utility>

	#include "api/scoped_refptr.h"
	#include "modules/rtp_rtcp/source/rtp_packet_received.h"
	#include "rtc_base/logging.h"
	#include "rtc_base/time_utils.h"

	namespace webrtc {

	std::unique_ptr<UlpfecReceiver> UlpfecReceiver::Create(
	uint32_t ssrc,
	RecoveredPacketReceiver* callback,
	rtc::ArrayView<const RtpExtension> extensions) {
	return std::make_unique<UlpfecReceiverImpl>(ssrc, callback, extensions);
	}

	UlpfecReceiverImpl::UlpfecReceiverImpl(
	uint32_t ssrc,
	RecoveredPacketReceiver* callback,
	rtc::ArrayView<const RtpExtension> extensions)
	: ssrc_(ssrc),
	extensions_(extensions),
	recovered_packet_callback_(callback),
	fec_(ForwardErrorCorrection::CreateUlpfec(ssrc_)) {}

	UlpfecReceiverImpl::~UlpfecReceiverImpl() {
	received_packets_.clear();
	fec_->ResetState(&recovered_packets_);
	}

	FecPacketCounter UlpfecReceiverImpl::GetPacketCounter() const {
	rtc::CritScope cs(&crit_sect_);
	return packet_counter_;
	}

	// 0 1 2 3
	// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	// \|F\| block PT \| timestamp offset \| block length \|
	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	//
	//
	// RFC 2198 RTP Payload for Redundant Audio Data September 1997
	//
	// The bits in the header are specified as follows:
	//
	// F: 1 bit First bit in header indicates whether another header block
	// follows. If 1 further header blocks follow, if 0 this is the
	// last header block.
	// If 0 there is only 1 byte RED header
	//
	// block PT: 7 bits RTP payload type for this block.
	//
	// timestamp offset: 14 bits Unsigned offset of timestamp of this block
	// relative to timestamp given in RTP header. The use of an unsigned
	// offset implies that redundant data must be sent after the primary
	// data, and is hence a time to be subtracted from the current
	// timestamp to determine the timestamp of the data for which this
	// block is the redundancy.
	//
	// block length: 10 bits Length in bytes of the corresponding data
	// block excluding header.

	bool UlpfecReceiverImpl::AddReceivedRedPacket(const RtpPacket& rtp_packet,
	uint8_t ulpfec_payload_type) {
	if (rtp_packet.Ssrc() != ssrc_) {
	RTC_LOG(LS_WARNING)
	<< "Received RED packet with different SSRC than expected; dropping.";
	return false;
	}
	if (rtp_packet.size() > IP_PACKET_SIZE) {
	RTC_LOG(LS_WARNING) << "Received RED packet with length exceeds maximum IP "
	"packet size; dropping.";
	return false;
	}
	rtc::CritScope cs(&crit_sect_);

	static constexpr uint8_t kRedHeaderLength = 1;

	if (rtp_packet.payload_size() == 0) {
	RTC_LOG(LS_WARNING) << "Corrupt/truncated FEC packet.";
	return false;
	}

	// Remove RED header of incoming packet and store as a virtual RTP packet.
	auto received_packet =
	std::make_unique<ForwardErrorCorrection::ReceivedPacket>();
	received_packet->pkt = new ForwardErrorCorrection::Packet();

	// Get payload type from RED header and sequence number from RTP header.
	uint8_t payload_type = rtp_packet.payload()[0] & 0x7f;
	received_packet->is_fec = payload_type == ulpfec_payload_type;
	received_packet->ssrc = rtp_packet.Ssrc();
	received_packet->seq_num = rtp_packet.SequenceNumber();

	if (rtp_packet.payload()[0] & 0x80) {
	// f bit set in RED header, i.e. there are more than one RED header blocks.
	// WebRTC never generates multiple blocks in a RED packet for FEC.
	RTC_LOG(LS_WARNING) << "More than 1 block in RED packet is not supported.";
	return false;
	}

	++packet_counter_.num_packets;
	packet_counter_.num_bytes += rtp_packet.size();
	if (packet_counter_.first_packet_time_ms == -1) {
	packet_counter_.first_packet_time_ms = rtc::TimeMillis();
	}

	if (received_packet->is_fec) {
	++packet_counter_.num_fec_packets;
	// everything behind the RED header
	received_packet->pkt->data =
	rtp_packet.Buffer().Slice(rtp_packet.headers_size() + kRedHeaderLength,
	rtp_packet.payload_size() - kRedHeaderLength);
	} else {
	auto red_payload = rtp_packet.payload().subview(kRedHeaderLength);
	received_packet->pkt->data.EnsureCapacity(rtp_packet.headers_size() +
	red_payload.size());
	// Copy RTP header.
	received_packet->pkt->data.SetData(rtp_packet.data(),
	rtp_packet.headers_size());
	// Set payload type.
	received_packet->pkt->data[1] &= 0x80; // Reset RED payload type.
	received_packet->pkt->data[1] += payload_type; // Set media payload type.
	// Copy payload data.
	received_packet->pkt->data.AppendData(red_payload.data(),
	red_payload.size());
	}

	if (received_packet->pkt->data.size() > 0) {
	received_packets_.push_back(std::move(received_packet));
	}
	return true;
	}

	// TODO(nisse): Drop always-zero return value.
	int32_t UlpfecReceiverImpl::ProcessReceivedFec() {
	crit_sect_.Enter();

	// If we iterate over \|received_packets_\| and it contains a packet that cause
	// us to recurse back to this function (for example a RED packet encapsulating
	// a RED packet), then we will recurse forever. To avoid this we swap
	// \|received_packets_\| with an empty vector so that the next recursive call
	// wont iterate over the same packet again. This also solves the problem of
	// not modifying the vector we are currently iterating over (packets are added
	// in AddReceivedRedPacket).
	std::vector<std::unique_ptr<ForwardErrorCorrection::ReceivedPacket>>
	received_packets;
	received_packets.swap(received_packets_);

	for (const auto& received_packet : received_packets) {
	// Send received media packet to VCM.
	if (!received_packet->is_fec) {
	ForwardErrorCorrection::Packet* packet = received_packet->pkt;
	crit_sect_.Leave();
	recovered_packet_callback_->OnRecoveredPacket(packet->data.data(),
	packet->data.size());
	crit_sect_.Enter();
	// Create a packet with the buffer to modify it.
	RtpPacketReceived rtp_packet;
	const uint8_t* const original_data = packet->data.cdata();
	if (!rtp_packet.Parse(packet->data)) {
	RTC_LOG(LS_WARNING) << "Corrupted media packet";
	} else {
	rtp_packet.IdentifyExtensions(extensions_);
	// Reset buffer reference, so zeroing would work on a buffer with a
	// single reference.
	packet->data = rtc::CopyOnWriteBuffer(0);
	rtp_packet.ZeroMutableExtensions();
	packet->data = rtp_packet.Buffer();
	// Ensure that zeroing of extensions was done in place.
	RTC_DCHECK_EQ(packet->data.cdata(), original_data);
	}
	}
	fec_->DecodeFec(*received_packet, &recovered_packets_);
	}

	// Send any recovered media packets to VCM.
	for (const auto& recovered_packet : recovered_packets_) {
	if (recovered_packet->returned) {
	// Already sent to the VCM and the jitter buffer.
	continue;
	}
	ForwardErrorCorrection::Packet* packet = recovered_packet->pkt;
	++packet_counter_.num_recovered_packets;
	// Set this flag first; in case the recovered packet carries a RED
	// header, OnRecoveredPacket will recurse back here.
	recovered_packet->returned = true;
	crit_sect_.Leave();
	recovered_packet_callback_->OnRecoveredPacket(packet->data.data(),
	packet->data.size());
	crit_sect_.Enter();
	}

	crit_sect_.Leave();
	return 0;
	}

	} // namespace webrtc