blob: 5cc7724fec93503fd085ed809c31b714af9ee91c [file] [log] [blame]
/*
* 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/rtp_sender.h"
#include <algorithm>
#include <limits>
#include <memory>
#include <string>
#include <utility>
#include "absl/strings/match.h"
#include "absl/strings/string_view.h"
#include "api/array_view.h"
#include "api/rtc_event_log/rtc_event_log.h"
#include "logging/rtc_event_log/events/rtc_event_rtp_packet_outgoing.h"
#include "modules/rtp_rtcp/include/rtp_cvo.h"
#include "modules/rtp_rtcp/source/byte_io.h"
#include "modules/rtp_rtcp/source/rtp_generic_frame_descriptor_extension.h"
#include "modules/rtp_rtcp/source/rtp_header_extensions.h"
#include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
#include "modules/rtp_rtcp/source/time_util.h"
#include "rtc_base/arraysize.h"
#include "rtc_base/checks.h"
#include "rtc_base/experiments/field_trial_parser.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_minmax.h"
#include "rtc_base/rate_limiter.h"
#include "rtc_base/time_utils.h"
namespace webrtc {
namespace {
// Max in the RFC 3550 is 255 bytes, we limit it to be modulus 32 for SRTP.
constexpr size_t kMaxPaddingLength = 224;
constexpr size_t kMinAudioPaddingLength = 50;
constexpr size_t kRtpHeaderLength = 12;
// Min size needed to get payload padding from packet history.
constexpr int kMinPayloadPaddingBytes = 50;
// Determines how much larger a payload padding packet may be, compared to the
// requested padding size.
constexpr double kMaxPaddingSizeFactor = 3.0;
template <typename Extension>
constexpr RtpExtensionSize CreateExtensionSize() {
return {Extension::kId, Extension::kValueSizeBytes};
}
template <typename Extension>
constexpr RtpExtensionSize CreateMaxExtensionSize() {
return {Extension::kId, Extension::kMaxValueSizeBytes};
}
// Size info for header extensions that might be used in padding or FEC packets.
constexpr RtpExtensionSize kFecOrPaddingExtensionSizes[] = {
CreateExtensionSize<AbsoluteSendTime>(),
CreateExtensionSize<TransmissionOffset>(),
CreateExtensionSize<TransportSequenceNumber>(),
CreateExtensionSize<PlayoutDelayLimits>(),
CreateMaxExtensionSize<RtpMid>(),
CreateExtensionSize<VideoTimingExtension>(),
};
// Size info for header extensions that might be used in video packets.
constexpr RtpExtensionSize kVideoExtensionSizes[] = {
CreateExtensionSize<AbsoluteSendTime>(),
CreateExtensionSize<AbsoluteCaptureTimeExtension>(),
CreateExtensionSize<TransmissionOffset>(),
CreateExtensionSize<TransportSequenceNumber>(),
CreateExtensionSize<PlayoutDelayLimits>(),
CreateExtensionSize<VideoOrientation>(),
CreateExtensionSize<VideoContentTypeExtension>(),
CreateExtensionSize<VideoTimingExtension>(),
CreateMaxExtensionSize<RtpStreamId>(),
CreateMaxExtensionSize<RepairedRtpStreamId>(),
CreateMaxExtensionSize<RtpMid>(),
{RtpGenericFrameDescriptorExtension00::kId,
RtpGenericFrameDescriptorExtension00::kMaxSizeBytes},
};
// Size info for header extensions that might be used in audio packets.
constexpr RtpExtensionSize kAudioExtensionSizes[] = {
CreateExtensionSize<AbsoluteSendTime>(),
CreateExtensionSize<AbsoluteCaptureTimeExtension>(),
CreateExtensionSize<AudioLevel>(),
CreateExtensionSize<InbandComfortNoiseExtension>(),
CreateExtensionSize<TransmissionOffset>(),
CreateExtensionSize<TransportSequenceNumber>(),
CreateMaxExtensionSize<RtpMid>(),
};
// Non-volatile extensions can be expected on all packets, if registered.
// Volatile ones, such as VideoContentTypeExtension which is only set on
// key-frames, are removed to simplify overhead calculations at the expense of
// some accuracy.
bool IsNonVolatile(RTPExtensionType type) {
switch (type) {
case kRtpExtensionTransmissionTimeOffset:
case kRtpExtensionAudioLevel:
case kRtpExtensionCsrcAudioLevel:
case kRtpExtensionAbsoluteSendTime:
case kRtpExtensionTransportSequenceNumber:
case kRtpExtensionTransportSequenceNumber02:
case kRtpExtensionRtpStreamId:
case kRtpExtensionRepairedRtpStreamId:
case kRtpExtensionMid:
case kRtpExtensionGenericFrameDescriptor:
case kRtpExtensionDependencyDescriptor:
return true;
case kRtpExtensionInbandComfortNoise:
case kRtpExtensionAbsoluteCaptureTime:
case kRtpExtensionVideoRotation:
case kRtpExtensionPlayoutDelay:
case kRtpExtensionVideoContentType:
case kRtpExtensionVideoLayersAllocation:
case kRtpExtensionVideoTiming:
case kRtpExtensionColorSpace:
case kRtpExtensionVideoFrameTrackingId:
return false;
case kRtpExtensionNone:
case kRtpExtensionNumberOfExtensions:
RTC_DCHECK_NOTREACHED();
return false;
}
RTC_CHECK_NOTREACHED();
}
bool HasBweExtension(const RtpHeaderExtensionMap& extensions_map) {
return extensions_map.IsRegistered(kRtpExtensionTransportSequenceNumber) ||
extensions_map.IsRegistered(kRtpExtensionTransportSequenceNumber02) ||
extensions_map.IsRegistered(kRtpExtensionAbsoluteSendTime) ||
extensions_map.IsRegistered(kRtpExtensionTransmissionTimeOffset);
}
} // namespace
RTPSender::RTPSender(const RtpRtcpInterface::Configuration& config,
RtpPacketHistory* packet_history,
RtpPacketSender* packet_sender)
: clock_(config.clock),
random_(clock_->TimeInMicroseconds()),
audio_configured_(config.audio),
ssrc_(config.local_media_ssrc),
rtx_ssrc_(config.rtx_send_ssrc),
flexfec_ssrc_(config.fec_generator ? config.fec_generator->FecSsrc()
: absl::nullopt),
packet_history_(packet_history),
paced_sender_(packet_sender),
sending_media_(true), // Default to sending media.
max_packet_size_(IP_PACKET_SIZE - 28), // Default is IP-v4/UDP.
rtp_header_extension_map_(config.extmap_allow_mixed),
// RTP variables
rid_(config.rid),
always_send_mid_and_rid_(config.always_send_mid_and_rid),
ssrc_has_acked_(false),
rtx_ssrc_has_acked_(false),
csrcs_(),
rtx_(kRtxOff),
supports_bwe_extension_(false),
retransmission_rate_limiter_(config.retransmission_rate_limiter) {
// This random initialization is not intended to be cryptographic strong.
timestamp_offset_ = random_.Rand<uint32_t>();
RTC_DCHECK(paced_sender_);
RTC_DCHECK(packet_history_);
RTC_DCHECK_LE(rid_.size(), RtpStreamId::kMaxValueSizeBytes);
UpdateHeaderSizes();
}
RTPSender::~RTPSender() {
// TODO(tommi): Use a thread checker to ensure the object is created and
// deleted on the same thread. At the moment this isn't possible due to
// voe::ChannelOwner in voice engine. To reproduce, run:
// voe_auto_test --automated --gtest_filter=*MixManyChannelsForStressOpus
// TODO(tommi,holmer): We don't grab locks in the dtor before accessing member
// variables but we grab them in all other methods. (what's the design?)
// Start documenting what thread we're on in what method so that it's easier
// to understand performance attributes and possibly remove locks.
}
rtc::ArrayView<const RtpExtensionSize> RTPSender::FecExtensionSizes() {
return rtc::MakeArrayView(kFecOrPaddingExtensionSizes,
arraysize(kFecOrPaddingExtensionSizes));
}
rtc::ArrayView<const RtpExtensionSize> RTPSender::VideoExtensionSizes() {
return rtc::MakeArrayView(kVideoExtensionSizes,
arraysize(kVideoExtensionSizes));
}
rtc::ArrayView<const RtpExtensionSize> RTPSender::AudioExtensionSizes() {
return rtc::MakeArrayView(kAudioExtensionSizes,
arraysize(kAudioExtensionSizes));
}
void RTPSender::SetExtmapAllowMixed(bool extmap_allow_mixed) {
MutexLock lock(&send_mutex_);
rtp_header_extension_map_.SetExtmapAllowMixed(extmap_allow_mixed);
}
bool RTPSender::RegisterRtpHeaderExtension(absl::string_view uri, int id) {
MutexLock lock(&send_mutex_);
bool registered = rtp_header_extension_map_.RegisterByUri(id, uri);
supports_bwe_extension_ = HasBweExtension(rtp_header_extension_map_);
UpdateHeaderSizes();
return registered;
}
bool RTPSender::IsRtpHeaderExtensionRegistered(RTPExtensionType type) const {
MutexLock lock(&send_mutex_);
return rtp_header_extension_map_.IsRegistered(type);
}
void RTPSender::DeregisterRtpHeaderExtension(absl::string_view uri) {
MutexLock lock(&send_mutex_);
rtp_header_extension_map_.Deregister(uri);
supports_bwe_extension_ = HasBweExtension(rtp_header_extension_map_);
UpdateHeaderSizes();
}
void RTPSender::SetMaxRtpPacketSize(size_t max_packet_size) {
RTC_DCHECK_GE(max_packet_size, 100);
RTC_DCHECK_LE(max_packet_size, IP_PACKET_SIZE);
MutexLock lock(&send_mutex_);
max_packet_size_ = max_packet_size;
}
size_t RTPSender::MaxRtpPacketSize() const {
return max_packet_size_;
}
void RTPSender::SetRtxStatus(int mode) {
MutexLock lock(&send_mutex_);
if (mode != kRtxOff &&
(!rtx_ssrc_.has_value() || rtx_payload_type_map_.empty())) {
RTC_LOG(LS_ERROR)
<< "Failed to enable RTX without RTX SSRC or payload types.";
return;
}
rtx_ = mode;
}
int RTPSender::RtxStatus() const {
MutexLock lock(&send_mutex_);
return rtx_;
}
void RTPSender::SetRtxPayloadType(int payload_type,
int associated_payload_type) {
MutexLock lock(&send_mutex_);
RTC_DCHECK_LE(payload_type, 127);
RTC_DCHECK_LE(associated_payload_type, 127);
if (payload_type < 0) {
RTC_LOG(LS_ERROR) << "Invalid RTX payload type: " << payload_type << ".";
return;
}
rtx_payload_type_map_[associated_payload_type] = payload_type;
}
int32_t RTPSender::ReSendPacket(uint16_t packet_id) {
int32_t packet_size = 0;
const bool rtx = (RtxStatus() & kRtxRetransmitted) > 0;
std::unique_ptr<RtpPacketToSend> packet =
packet_history_->GetPacketAndMarkAsPending(
packet_id, [&](const RtpPacketToSend& stored_packet) {
// Check if we're overusing retransmission bitrate.
// TODO(sprang): Add histograms for nack success or failure
// reasons.
packet_size = stored_packet.size();
std::unique_ptr<RtpPacketToSend> retransmit_packet;
if (retransmission_rate_limiter_ &&
!retransmission_rate_limiter_->TryUseRate(packet_size)) {
return retransmit_packet;
}
if (rtx) {
retransmit_packet = BuildRtxPacket(stored_packet);
} else {
retransmit_packet =
std::make_unique<RtpPacketToSend>(stored_packet);
}
if (retransmit_packet) {
retransmit_packet->set_retransmitted_sequence_number(
stored_packet.SequenceNumber());
}
return retransmit_packet;
});
if (packet_size == 0) {
// Packet not found or already queued for retransmission, ignore.
RTC_DCHECK(!packet);
return 0;
}
if (!packet) {
// Packet was found, but lambda helper above chose not to create
// `retransmit_packet` out of it.
return -1;
}
packet->set_packet_type(RtpPacketMediaType::kRetransmission);
packet->set_fec_protect_packet(false);
std::vector<std::unique_ptr<RtpPacketToSend>> packets;
packets.emplace_back(std::move(packet));
paced_sender_->EnqueuePackets(std::move(packets));
return packet_size;
}
void RTPSender::OnReceivedAckOnSsrc(int64_t extended_highest_sequence_number) {
MutexLock lock(&send_mutex_);
bool update_required = !ssrc_has_acked_;
ssrc_has_acked_ = true;
if (update_required) {
UpdateHeaderSizes();
}
}
void RTPSender::OnReceivedAckOnRtxSsrc(
int64_t extended_highest_sequence_number) {
MutexLock lock(&send_mutex_);
bool update_required = !rtx_ssrc_has_acked_;
rtx_ssrc_has_acked_ = true;
if (update_required) {
UpdateHeaderSizes();
}
}
void RTPSender::OnReceivedNack(
const std::vector<uint16_t>& nack_sequence_numbers,
int64_t avg_rtt) {
packet_history_->SetRtt(TimeDelta::Millis(5 + avg_rtt));
for (uint16_t seq_no : nack_sequence_numbers) {
const int32_t bytes_sent = ReSendPacket(seq_no);
if (bytes_sent < 0) {
// Failed to send one Sequence number. Give up the rest in this nack.
RTC_LOG(LS_WARNING) << "Failed resending RTP packet " << seq_no
<< ", Discard rest of packets.";
break;
}
}
}
bool RTPSender::SupportsPadding() const {
MutexLock lock(&send_mutex_);
return sending_media_ && supports_bwe_extension_;
}
bool RTPSender::SupportsRtxPayloadPadding() const {
MutexLock lock(&send_mutex_);
return sending_media_ && supports_bwe_extension_ &&
(rtx_ & kRtxRedundantPayloads);
}
std::vector<std::unique_ptr<RtpPacketToSend>> RTPSender::GeneratePadding(
size_t target_size_bytes,
bool media_has_been_sent,
bool can_send_padding_on_media_ssrc) {
// This method does not actually send packets, it just generates
// them and puts them in the pacer queue. Since this should incur
// low overhead, keep the lock for the scope of the method in order
// to make the code more readable.
std::vector<std::unique_ptr<RtpPacketToSend>> padding_packets;
size_t bytes_left = target_size_bytes;
if (SupportsRtxPayloadPadding()) {
while (bytes_left >= kMinPayloadPaddingBytes) {
std::unique_ptr<RtpPacketToSend> packet =
packet_history_->GetPayloadPaddingPacket(
[&](const RtpPacketToSend& packet)
-> std::unique_ptr<RtpPacketToSend> {
// Limit overshoot, generate <= `kMaxPaddingSizeFactor` *
// `target_size_bytes`.
const size_t max_overshoot_bytes = static_cast<size_t>(
((kMaxPaddingSizeFactor - 1.0) * target_size_bytes) + 0.5);
if (packet.payload_size() + kRtxHeaderSize >
max_overshoot_bytes + bytes_left) {
return nullptr;
}
return BuildRtxPacket(packet);
});
if (!packet) {
break;
}
bytes_left -= std::min(bytes_left, packet->payload_size());
packet->set_packet_type(RtpPacketMediaType::kPadding);
padding_packets.push_back(std::move(packet));
}
}
MutexLock lock(&send_mutex_);
if (!sending_media_) {
return {};
}
size_t padding_bytes_in_packet;
const size_t max_payload_size =
max_packet_size_ - max_padding_fec_packet_header_;
if (audio_configured_) {
// Allow smaller padding packets for audio.
padding_bytes_in_packet = rtc::SafeClamp<size_t>(
bytes_left, kMinAudioPaddingLength,
rtc::SafeMin(max_payload_size, kMaxPaddingLength));
} else {
// Always send full padding packets. This is accounted for by the
// RtpPacketSender, which will make sure we don't send too much padding even
// if a single packet is larger than requested.
// We do this to avoid frequently sending small packets on higher bitrates.
padding_bytes_in_packet = rtc::SafeMin(max_payload_size, kMaxPaddingLength);
}
while (bytes_left > 0) {
auto padding_packet =
std::make_unique<RtpPacketToSend>(&rtp_header_extension_map_);
padding_packet->set_packet_type(RtpPacketMediaType::kPadding);
padding_packet->SetMarker(false);
if (rtx_ == kRtxOff) {
if (!can_send_padding_on_media_ssrc) {
break;
}
padding_packet->SetSsrc(ssrc_);
} else {
// Without abs-send-time or transport sequence number a media packet
// must be sent before padding so that the timestamps used for
// estimation are correct.
if (!media_has_been_sent &&
!(rtp_header_extension_map_.IsRegistered(AbsoluteSendTime::kId) ||
rtp_header_extension_map_.IsRegistered(
TransportSequenceNumber::kId))) {
break;
}
RTC_DCHECK(rtx_ssrc_);
RTC_DCHECK(!rtx_payload_type_map_.empty());
padding_packet->SetSsrc(*rtx_ssrc_);
padding_packet->SetPayloadType(rtx_payload_type_map_.begin()->second);
}
if (rtp_header_extension_map_.IsRegistered(TransportSequenceNumber::kId)) {
padding_packet->ReserveExtension<TransportSequenceNumber>();
}
if (rtp_header_extension_map_.IsRegistered(TransmissionOffset::kId)) {
padding_packet->ReserveExtension<TransmissionOffset>();
}
if (rtp_header_extension_map_.IsRegistered(AbsoluteSendTime::kId)) {
padding_packet->ReserveExtension<AbsoluteSendTime>();
}
padding_packet->SetPadding(padding_bytes_in_packet);
bytes_left -= std::min(bytes_left, padding_bytes_in_packet);
padding_packets.push_back(std::move(padding_packet));
}
return padding_packets;
}
bool RTPSender::SendToNetwork(std::unique_ptr<RtpPacketToSend> packet) {
RTC_DCHECK(packet);
auto packet_type = packet->packet_type();
RTC_CHECK(packet_type) << "Packet type must be set before sending.";
if (packet->capture_time() <= Timestamp::Zero()) {
packet->set_capture_time(clock_->CurrentTime());
}
std::vector<std::unique_ptr<RtpPacketToSend>> packets;
packets.emplace_back(std::move(packet));
paced_sender_->EnqueuePackets(std::move(packets));
return true;
}
void RTPSender::EnqueuePackets(
std::vector<std::unique_ptr<RtpPacketToSend>> packets) {
RTC_DCHECK(!packets.empty());
Timestamp now = clock_->CurrentTime();
for (auto& packet : packets) {
RTC_DCHECK(packet);
RTC_CHECK(packet->packet_type().has_value())
<< "Packet type must be set before sending.";
if (packet->capture_time() <= Timestamp::Zero()) {
packet->set_capture_time(now);
}
}
paced_sender_->EnqueuePackets(std::move(packets));
}
size_t RTPSender::FecOrPaddingPacketMaxRtpHeaderLength() const {
MutexLock lock(&send_mutex_);
return max_padding_fec_packet_header_;
}
size_t RTPSender::ExpectedPerPacketOverhead() const {
MutexLock lock(&send_mutex_);
return max_media_packet_header_;
}
std::unique_ptr<RtpPacketToSend> RTPSender::AllocatePacket() const {
MutexLock lock(&send_mutex_);
// TODO(danilchap): Find better motivator and value for extra capacity.
// RtpPacketizer might slightly miscalulate needed size,
// SRTP may benefit from extra space in the buffer and do encryption in place
// saving reallocation.
// While sending slightly oversized packet increase chance of dropped packet,
// it is better than crash on drop packet without trying to send it.
static constexpr int kExtraCapacity = 16;
auto packet = std::make_unique<RtpPacketToSend>(
&rtp_header_extension_map_, max_packet_size_ + kExtraCapacity);
packet->SetSsrc(ssrc_);
packet->SetCsrcs(csrcs_);
// Reserve extensions, if registered, RtpSender set in SendToNetwork.
packet->ReserveExtension<AbsoluteSendTime>();
packet->ReserveExtension<TransmissionOffset>();
packet->ReserveExtension<TransportSequenceNumber>();
// BUNDLE requires that the receiver "bind" the received SSRC to the values
// in the MID and/or (R)RID header extensions if present. Therefore, the
// sender can reduce overhead by omitting these header extensions once it
// knows that the receiver has "bound" the SSRC.
// This optimization can be configured by setting
// `always_send_mid_and_rid_` appropriately.
//
// The algorithm here is fairly simple: Always attach a MID and/or RID (if
// configured) to the outgoing packets until an RTCP receiver report comes
// back for this SSRC. That feedback indicates the receiver must have
// received a packet with the SSRC and header extension(s), so the sender
// then stops attaching the MID and RID.
if (always_send_mid_and_rid_ || !ssrc_has_acked_) {
// These are no-ops if the corresponding header extension is not registered.
if (!mid_.empty()) {
packet->SetExtension<RtpMid>(mid_);
}
if (!rid_.empty()) {
packet->SetExtension<RtpStreamId>(rid_);
}
}
return packet;
}
size_t RTPSender::RtxPacketOverhead() const {
MutexLock lock(&send_mutex_);
if (rtx_ == kRtxOff) {
return 0;
}
size_t overhead = 0;
// Count space for the RTP header extensions that might need to be added to
// the RTX packet.
if (!always_send_mid_and_rid_ && (!rtx_ssrc_has_acked_ && ssrc_has_acked_)) {
// Prefer to reserve extra byte in case two byte header rtp header
// extensions are used.
static constexpr int kRtpExtensionHeaderSize = 2;
// Rtx packets hasn't been acked and would need to have mid and rrsid rtp
// header extensions, while media packets no longer needs to include mid and
// rsid extensions.
if (!mid_.empty()) {
overhead += (kRtpExtensionHeaderSize + mid_.size());
}
if (!rid_.empty()) {
overhead += (kRtpExtensionHeaderSize + rid_.size());
}
// RTP header extensions are rounded up to 4 bytes. Depending on already
// present extensions adding mid & rrsid may add up to 3 bytes of padding.
overhead += 3;
}
// Add two bytes for the original sequence number in the RTP payload.
overhead += kRtxHeaderSize;
return overhead;
}
void RTPSender::SetSendingMediaStatus(bool enabled) {
MutexLock lock(&send_mutex_);
sending_media_ = enabled;
}
bool RTPSender::SendingMedia() const {
MutexLock lock(&send_mutex_);
return sending_media_;
}
bool RTPSender::IsAudioConfigured() const {
return audio_configured_;
}
void RTPSender::SetTimestampOffset(uint32_t timestamp) {
MutexLock lock(&send_mutex_);
timestamp_offset_ = timestamp;
}
uint32_t RTPSender::TimestampOffset() const {
MutexLock lock(&send_mutex_);
return timestamp_offset_;
}
void RTPSender::SetMid(absl::string_view mid) {
// This is configured via the API.
MutexLock lock(&send_mutex_);
RTC_DCHECK_LE(mid.length(), RtpMid::kMaxValueSizeBytes);
mid_ = std::string(mid);
UpdateHeaderSizes();
}
std::vector<uint32_t> RTPSender::Csrcs() const {
MutexLock lock(&send_mutex_);
return csrcs_;
}
void RTPSender::SetCsrcs(const std::vector<uint32_t>& csrcs) {
RTC_DCHECK_LE(csrcs.size(), kRtpCsrcSize);
MutexLock lock(&send_mutex_);
csrcs_ = csrcs;
UpdateHeaderSizes();
}
static void CopyHeaderAndExtensionsToRtxPacket(const RtpPacketToSend& packet,
RtpPacketToSend* rtx_packet) {
// Set the relevant fixed packet headers. The following are not set:
// * Payload type - it is replaced in rtx packets.
// * Sequence number - RTX has a separate sequence numbering.
// * SSRC - RTX stream has its own SSRC.
rtx_packet->SetMarker(packet.Marker());
rtx_packet->SetTimestamp(packet.Timestamp());
// Set the variable fields in the packet header:
// * CSRCs - must be set before header extensions.
// * Header extensions - replace Rid header with RepairedRid header.
const std::vector<uint32_t> csrcs = packet.Csrcs();
rtx_packet->SetCsrcs(csrcs);
for (int extension_num = kRtpExtensionNone + 1;
extension_num < kRtpExtensionNumberOfExtensions; ++extension_num) {
auto extension = static_cast<RTPExtensionType>(extension_num);
// Stream ID header extensions (MID, RSID) are sent per-SSRC. Since RTX
// operates on a different SSRC, the presence and values of these header
// extensions should be determined separately and not blindly copied.
if (extension == kRtpExtensionMid ||
extension == kRtpExtensionRtpStreamId) {
continue;
}
// Empty extensions should be supported, so not checking `source.empty()`.
if (!packet.HasExtension(extension)) {
continue;
}
rtc::ArrayView<const uint8_t> source = packet.FindExtension(extension);
rtc::ArrayView<uint8_t> destination =
rtx_packet->AllocateExtension(extension, source.size());
// Could happen if any:
// 1. Extension has 0 length.
// 2. Extension is not registered in destination.
// 3. Allocating extension in destination failed.
if (destination.empty() || source.size() != destination.size()) {
continue;
}
std::memcpy(destination.begin(), source.begin(), destination.size());
}
}
std::unique_ptr<RtpPacketToSend> RTPSender::BuildRtxPacket(
const RtpPacketToSend& packet) {
std::unique_ptr<RtpPacketToSend> rtx_packet;
// Add original RTP header.
{
MutexLock lock(&send_mutex_);
if (!sending_media_)
return nullptr;
RTC_DCHECK(rtx_ssrc_);
// Replace payload type.
auto kv = rtx_payload_type_map_.find(packet.PayloadType());
if (kv == rtx_payload_type_map_.end())
return nullptr;
rtx_packet = std::make_unique<RtpPacketToSend>(&rtp_header_extension_map_,
max_packet_size_);
rtx_packet->SetPayloadType(kv->second);
// Replace SSRC.
rtx_packet->SetSsrc(*rtx_ssrc_);
CopyHeaderAndExtensionsToRtxPacket(packet, rtx_packet.get());
// RTX packets are sent on an SSRC different from the main media, so the
// decision to attach MID and/or RRID header extensions is completely
// separate from that of the main media SSRC.
//
// Note that RTX packets must used the RepairedRtpStreamId (RRID) header
// extension instead of the RtpStreamId (RID) header extension even though
// the payload is identical.
if (always_send_mid_and_rid_ || !rtx_ssrc_has_acked_) {
// These are no-ops if the corresponding header extension is not
// registered.
if (!mid_.empty()) {
rtx_packet->SetExtension<RtpMid>(mid_);
}
if (!rid_.empty()) {
rtx_packet->SetExtension<RepairedRtpStreamId>(rid_);
}
}
}
RTC_DCHECK(rtx_packet);
uint8_t* rtx_payload =
rtx_packet->AllocatePayload(packet.payload_size() + kRtxHeaderSize);
if (rtx_payload == nullptr)
return nullptr;
// Add OSN (original sequence number).
ByteWriter<uint16_t>::WriteBigEndian(rtx_payload, packet.SequenceNumber());
// Add original payload data.
auto payload = packet.payload();
if (!payload.empty()) {
memcpy(rtx_payload + kRtxHeaderSize, payload.data(), payload.size());
}
// Add original additional data.
rtx_packet->set_additional_data(packet.additional_data());
// Copy capture time so e.g. TransmissionOffset is correctly set.
rtx_packet->set_capture_time(packet.capture_time());
return rtx_packet;
}
void RTPSender::SetRtpState(const RtpState& rtp_state) {
MutexLock lock(&send_mutex_);
timestamp_offset_ = rtp_state.start_timestamp;
ssrc_has_acked_ = rtp_state.ssrc_has_acked;
UpdateHeaderSizes();
}
RtpState RTPSender::GetRtpState() const {
MutexLock lock(&send_mutex_);
RtpState state;
state.start_timestamp = timestamp_offset_;
state.ssrc_has_acked = ssrc_has_acked_;
return state;
}
void RTPSender::SetRtxRtpState(const RtpState& rtp_state) {
MutexLock lock(&send_mutex_);
rtx_ssrc_has_acked_ = rtp_state.ssrc_has_acked;
}
RtpState RTPSender::GetRtxRtpState() const {
MutexLock lock(&send_mutex_);
RtpState state;
state.start_timestamp = timestamp_offset_;
state.ssrc_has_acked = rtx_ssrc_has_acked_;
return state;
}
void RTPSender::UpdateHeaderSizes() {
const size_t rtp_header_length =
kRtpHeaderLength + sizeof(uint32_t) * csrcs_.size();
max_padding_fec_packet_header_ =
rtp_header_length + RtpHeaderExtensionSize(kFecOrPaddingExtensionSizes,
rtp_header_extension_map_);
// RtpStreamId, Mid and RepairedRtpStreamId are treated specially in that
// we check if they currently are being sent. RepairedRtpStreamId can be
// sent instead of RtpStreamID on RTX packets and may share the same space.
// When the primary SSRC has already been acked but the RTX SSRC has not
// yet been acked, RepairedRtpStreamId needs to be taken into account
// separately.
const bool send_mid_rid_on_rtx =
rtx_ssrc_.has_value() &&
(always_send_mid_and_rid_ || !rtx_ssrc_has_acked_);
const bool send_mid_rid = always_send_mid_and_rid_ || !ssrc_has_acked_;
std::vector<RtpExtensionSize> non_volatile_extensions;
for (auto& extension :
audio_configured_ ? AudioExtensionSizes() : VideoExtensionSizes()) {
if (IsNonVolatile(extension.type)) {
switch (extension.type) {
case RTPExtensionType::kRtpExtensionMid:
if ((send_mid_rid || send_mid_rid_on_rtx) && !mid_.empty()) {
non_volatile_extensions.push_back(extension);
}
break;
case RTPExtensionType::kRtpExtensionRtpStreamId:
if (send_mid_rid && !rid_.empty()) {
non_volatile_extensions.push_back(extension);
}
break;
case RTPExtensionType::kRtpExtensionRepairedRtpStreamId:
if (send_mid_rid_on_rtx && !send_mid_rid && !rid_.empty()) {
non_volatile_extensions.push_back(extension);
}
break;
default:
non_volatile_extensions.push_back(extension);
}
}
}
max_media_packet_header_ =
rtp_header_length + RtpHeaderExtensionSize(non_volatile_extensions,
rtp_header_extension_map_);
// Reserve extra bytes if packet might be resent in an rtx packet.
if (rtx_ssrc_.has_value()) {
max_media_packet_header_ += kRtxHeaderSize;
}
}
} // namespace webrtc