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/*
* 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 "modules/rtp_rtcp/include/flexfec_receiver.h"
#include <string.h>
#include <cstdint>
#include <memory>
#include "api/scoped_refptr.h"
#include "api/sequence_checker.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
#include "modules/rtp_rtcp/include/recovered_packet_receiver.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "modules/rtp_rtcp/source/forward_error_correction.h"
#include "modules/rtp_rtcp/source/rtp_packet_received.h"
#include "modules/rtp_rtcp/source/ulpfec_receiver.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
namespace {
// 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 TimeDelta kPacketLogInterval = TimeDelta::Seconds(10);
} // namespace
FlexfecReceiver::FlexfecReceiver(
uint32_t ssrc,
uint32_t protected_media_ssrc,
RecoveredPacketReceiver* recovered_packet_receiver)
: FlexfecReceiver(Clock::GetRealTimeClock(),
ssrc,
protected_media_ssrc,
recovered_packet_receiver) {}
FlexfecReceiver::FlexfecReceiver(
Clock* clock,
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) {
// 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_RUN_ON(&sequence_checker_);
// If this packet was recovered, it might be originating from
// ProcessReceivedPacket in this object. To avoid lifetime issues with
// `recovered_packets_`, we therefore break the cycle here.
// This might reduce decoding efficiency a bit, since we can't disambiguate
// recovered packets by RTX from recovered packets by FlexFEC.
if (packet.recovered())
return;
std::unique_ptr<ForwardErrorCorrection::ReceivedPacket> received_packet =
AddReceivedPacket(packet);
if (!received_packet)
return;
ProcessReceivedPacket(*received_packet);
}
FecPacketCounter FlexfecReceiver::GetPacketCounter() const {
RTC_DCHECK_RUN_ON(&sequence_checker_);
return packet_counter_;
}
// TODO(eladalon): Consider using packet.recovered() to avoid processing
// recovered packets here.
std::unique_ptr<ForwardErrorCorrection::ReceivedPacket>
FlexfecReceiver::AddReceivedPacket(const RtpPacketReceived& packet) {
RTC_DCHECK_RUN_ON(&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<ForwardErrorCorrection::ReceivedPacket> received_packet(
new ForwardErrorCorrection::ReceivedPacket());
received_packet->seq_num = packet.SequenceNumber();
received_packet->ssrc = packet.Ssrc();
received_packet->extensions = packet.extension_manager();
if (received_packet->ssrc == ssrc_) {
// This is a FlexFEC packet.
if (packet.payload_size() < kMinFlexfecHeaderSize) {
RTC_LOG(LS_WARNING) << "Truncated FlexFEC packet, discarding.";
return nullptr;
}
received_packet->is_fec = true;
++packet_counter_.num_fec_packets;
// Insert packet payload into erasure code.
received_packet->pkt = scoped_refptr<ForwardErrorCorrection::Packet>(
new ForwardErrorCorrection::Packet());
received_packet->pkt->data =
packet.Buffer().Slice(packet.headers_size(), packet.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 nullptr;
}
received_packet->is_fec = false;
// Insert entire packet into erasure code.
// Create a copy and fill with zeros all mutable extensions.
received_packet->pkt = scoped_refptr<ForwardErrorCorrection::Packet>(
new ForwardErrorCorrection::Packet());
RtpPacketReceived packet_copy(packet);
packet_copy.ZeroMutableExtensions();
received_packet->pkt->data = packet_copy.Buffer();
}
++packet_counter_.num_packets;
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.
void FlexfecReceiver::ProcessReceivedPacket(
const ForwardErrorCorrection::ReceivedPacket& received_packet) {
RTC_DCHECK_RUN_ON(&sequence_checker_);
// Decode.
ForwardErrorCorrection::DecodeFecResult decode_result =
erasure_code_->DecodeFec(received_packet, &recovered_packets_);
if (decode_result.num_recovered_packets == 0) {
return;
}
// Return recovered packets through callback.
for (const auto& recovered_packet : recovered_packets_) {
RTC_CHECK(recovered_packet);
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;
RTC_CHECK_GE(recovered_packet->pkt->data.size(), kRtpHeaderSize);
RtpPacketReceived parsed_packet(&received_packet.extensions);
if (!parsed_packet.Parse(recovered_packet->pkt->data)) {
continue;
}
parsed_packet.set_recovered(true);
// TODO(brandtr): Update here when we support protecting audio packets too.
parsed_packet.set_payload_type_frequency(kVideoPayloadTypeFrequency);
recovered_packet_receiver_->OnRecoveredPacket(parsed_packet);
// Periodically log the incoming packets at LS_INFO.
Timestamp now = clock_->CurrentTime();
bool should_log_periodically =
now - last_recovered_packet_ > kPacketLogInterval;
if (RTC_LOG_CHECK_LEVEL(LS_VERBOSE) || should_log_periodically) {
LoggingSeverity level = should_log_periodically ? LS_INFO : LS_VERBOSE;
RTC_LOG_V(level) << "Recovered media packet with SSRC: "
<< parsed_packet.Ssrc() << " seq "
<< parsed_packet.SequenceNumber() << " recovered length "
<< recovered_packet->pkt->data.size()
<< " received length "
<< received_packet.pkt->data.size()
<< " from FlexFEC stream with SSRC: " << ssrc_;
if (should_log_periodically) {
last_recovered_packet_ = now;
}
}
}
}
} // namespace webrtc
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