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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_sender.h"
#include <string.h>
#include <list>
#include <utility>
#include "absl/strings/string_view.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.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_header_extensions.h"
#include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
namespace {
// Let first sequence number be in the first half of the interval.
constexpr uint16_t kMaxInitRtpSeqNumber = 0x7fff;
// See breakdown in flexfec_header_reader_writer.cc.
constexpr size_t kFlexfecMaxHeaderSize = 32;
// Since we will mainly use FlexFEC to protect video streams, we use a 90 kHz
// clock for the RTP timestamps. (This is according to the RFC, which states
// that it is RECOMMENDED to use the same clock frequency for FlexFEC as for
// the protected media stream.)
// The constant converts from clock millisecond timestamps to the 90 kHz
// RTP timestamp.
const int kMsToRtpTimestamp = kVideoPayloadTypeFrequency / 1000;
// How often to log the generated FEC packets to the text log.
constexpr TimeDelta kPacketLogInterval = TimeDelta::Seconds(10);
RtpHeaderExtensionMap RegisterSupportedExtensions(
const std::vector<RtpExtension>& rtp_header_extensions) {
RtpHeaderExtensionMap map;
for (const auto& extension : rtp_header_extensions) {
if (extension.uri == TransportSequenceNumber::Uri()) {
map.Register<TransportSequenceNumber>(extension.id);
} else if (extension.uri == AbsoluteSendTime::Uri()) {
map.Register<AbsoluteSendTime>(extension.id);
} else if (extension.uri == TransmissionOffset::Uri()) {
map.Register<TransmissionOffset>(extension.id);
} else if (extension.uri == RtpMid::Uri()) {
map.Register<RtpMid>(extension.id);
} else {
RTC_LOG(LS_INFO)
<< "FlexfecSender only supports RTP header extensions for "
"BWE and MID, so the extension "
<< extension.ToString() << " will not be used.";
}
}
return map;
}
} // namespace
FlexfecSender::FlexfecSender(
int payload_type,
uint32_t ssrc,
uint32_t protected_media_ssrc,
absl::string_view mid,
const std::vector<RtpExtension>& rtp_header_extensions,
rtc::ArrayView<const RtpExtensionSize> extension_sizes,
const RtpState* rtp_state,
Clock* clock)
: clock_(clock),
random_(clock_->TimeInMicroseconds()),
payload_type_(payload_type),
// Reset RTP state if this is not the first time we are operating.
// Otherwise, randomize the initial timestamp offset and RTP sequence
// numbers. (This is not intended to be cryptographically strong.)
timestamp_offset_(rtp_state ? rtp_state->start_timestamp
: random_.Rand<uint32_t>()),
ssrc_(ssrc),
protected_media_ssrc_(protected_media_ssrc),
mid_(mid),
seq_num_(rtp_state ? rtp_state->sequence_number
: random_.Rand(1, kMaxInitRtpSeqNumber)),
ulpfec_generator_(
ForwardErrorCorrection::CreateFlexfec(ssrc, protected_media_ssrc),
clock_),
rtp_header_extension_map_(
RegisterSupportedExtensions(rtp_header_extensions)),
header_extensions_size_(
RtpHeaderExtensionSize(extension_sizes, rtp_header_extension_map_)),
fec_bitrate_(/*max_window_size=*/TimeDelta::Seconds(1)) {
// This object should not have been instantiated if FlexFEC is disabled.
RTC_DCHECK_GE(payload_type, 0);
RTC_DCHECK_LE(payload_type, 127);
}
FlexfecSender::~FlexfecSender() = default;
// We are reusing the implementation from UlpfecGenerator for SetFecParameters,
// AddRtpPacketAndGenerateFec, and FecAvailable.
void FlexfecSender::SetProtectionParameters(
const FecProtectionParams& delta_params,
const FecProtectionParams& key_params) {
ulpfec_generator_.SetProtectionParameters(delta_params, key_params);
}
void FlexfecSender::AddPacketAndGenerateFec(const RtpPacketToSend& packet) {
// TODO(brandtr): Generalize this SSRC check when we support multistream
// protection.
RTC_DCHECK_EQ(packet.Ssrc(), protected_media_ssrc_);
ulpfec_generator_.AddPacketAndGenerateFec(packet);
}
std::vector<std::unique_ptr<RtpPacketToSend>> FlexfecSender::GetFecPackets() {
RTC_CHECK_RUNS_SERIALIZED(&ulpfec_generator_.race_checker_);
std::vector<std::unique_ptr<RtpPacketToSend>> fec_packets_to_send;
fec_packets_to_send.reserve(ulpfec_generator_.generated_fec_packets_.size());
size_t total_fec_data_bytes = 0;
for (const auto* fec_packet : ulpfec_generator_.generated_fec_packets_) {
std::unique_ptr<RtpPacketToSend> fec_packet_to_send(
new RtpPacketToSend(&rtp_header_extension_map_));
fec_packet_to_send->set_packet_type(
RtpPacketMediaType::kForwardErrorCorrection);
fec_packet_to_send->set_allow_retransmission(false);
// RTP header.
fec_packet_to_send->SetMarker(false);
fec_packet_to_send->SetPayloadType(payload_type_);
fec_packet_to_send->SetSequenceNumber(seq_num_++);
fec_packet_to_send->SetTimestamp(
timestamp_offset_ +
static_cast<uint32_t>(kMsToRtpTimestamp *
clock_->TimeInMilliseconds()));
// Set "capture time" so that the TransmissionOffset header extension
// can be set by the RTPSender.
fec_packet_to_send->set_capture_time(clock_->CurrentTime());
fec_packet_to_send->SetSsrc(ssrc_);
// Reserve extensions, if registered. These will be set by the RTPSender.
fec_packet_to_send->ReserveExtension<AbsoluteSendTime>();
fec_packet_to_send->ReserveExtension<TransmissionOffset>();
fec_packet_to_send->ReserveExtension<TransportSequenceNumber>();
// Possibly include the MID header extension.
if (!mid_.empty()) {
// This is a no-op if the MID header extension is not registered.
fec_packet_to_send->SetExtension<RtpMid>(mid_);
}
// RTP payload.
uint8_t* payload =
fec_packet_to_send->AllocatePayload(fec_packet->data.size());
memcpy(payload, fec_packet->data.cdata(), fec_packet->data.size());
total_fec_data_bytes += fec_packet_to_send->size();
fec_packets_to_send.push_back(std::move(fec_packet_to_send));
}
if (!fec_packets_to_send.empty()) {
ulpfec_generator_.ResetState();
}
Timestamp now = clock_->CurrentTime();
if (!fec_packets_to_send.empty() &&
now - last_generated_packet_ > kPacketLogInterval) {
RTC_LOG(LS_VERBOSE) << "Generated " << fec_packets_to_send.size()
<< " FlexFEC packets with payload type: "
<< payload_type_ << " and SSRC: " << ssrc_ << ".";
last_generated_packet_ = now;
}
MutexLock lock(&mutex_);
fec_bitrate_.Update(total_fec_data_bytes, now);
return fec_packets_to_send;
}
// The overhead is BWE RTP header extensions and FlexFEC header.
size_t FlexfecSender::MaxPacketOverhead() const {
return header_extensions_size_ + kFlexfecMaxHeaderSize;
}
DataRate FlexfecSender::CurrentFecRate() const {
MutexLock lock(&mutex_);
return fec_bitrate_.Rate(clock_->CurrentTime()).value_or(DataRate::Zero());
}
absl::optional<RtpState> FlexfecSender::GetRtpState() {
RtpState rtp_state;
rtp_state.sequence_number = seq_num_;
rtp_state.start_timestamp = timestamp_offset_;
return rtp_state;
}
} // namespace webrtc
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