| /* |
| * 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() { |
| RTC_DCHECK_RUN_ON(&sequence_checker_); |
| received_packets_.clear(); |
| fec_->ResetState(&recovered_packets_); |
| } |
| |
| FecPacketCounter UlpfecReceiverImpl::GetPacketCounter() const { |
| RTC_DCHECK_RUN_ON(&sequence_checker_); |
| 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 RtpPacketReceived& rtp_packet, |
| uint8_t ulpfec_payload_type) { |
| RTC_DCHECK_RUN_ON(&sequence_checker_); |
| // TODO(bugs.webrtc.org/11993): We get here via Call::DeliverRtp, so should be |
| // moved to the network thread. |
| |
| 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; |
| } |
| |
| 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->is_recovered = rtp_packet.recovered(); |
| 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 { |
| received_packet->pkt->data.EnsureCapacity(rtp_packet.size() - |
| kRedHeaderLength); |
| // Copy RTP header. |
| received_packet->pkt->data.SetData(rtp_packet.data(), |
| rtp_packet.headers_size()); |
| // Set payload type. |
| uint8_t& payload_type_byte = received_packet->pkt->data.MutableData()[1]; |
| payload_type_byte &= 0x80; // Reset RED payload type. |
| payload_type_byte += payload_type; // Set media payload type. |
| // Copy payload and padding data, after the RED header. |
| received_packet->pkt->data.AppendData( |
| rtp_packet.data() + rtp_packet.headers_size() + kRedHeaderLength, |
| rtp_packet.size() - rtp_packet.headers_size() - kRedHeaderLength); |
| } |
| |
| 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() { |
| RTC_DCHECK_RUN_ON(&sequence_checker_); |
| |
| // 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; |
| recovered_packet_callback_->OnRecoveredPacket(packet->data.data(), |
| packet->data.size()); |
| // 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); |
| } |
| } |
| if (!received_packet->is_recovered) { |
| // Do not pass recovered packets to FEC. Recovered packet might have |
| // different set of the RTP header extensions and thus different byte |
| // representation than the original packet, That will corrupt |
| // FEC calculation. |
| 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; |
| recovered_packet_callback_->OnRecoveredPacket(packet->data.data(), |
| packet->data.size()); |
| } |
| |
| return 0; |
| } |
| |
| } // namespace webrtc |
