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/*
* Copyright (c) 2015 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/pacing/packet_router.h"
#include <algorithm>
#include <limits>
#include "modules/rtp_rtcp/include/rtp_rtcp.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "modules/rtp_rtcp/source/rtcp_packet/transport_feedback.h"
#include "rtc_base/atomicops.h"
#include "rtc_base/checks.h"
#include "rtc_base/timeutils.h"
namespace webrtc {
namespace {
constexpr int kRembSendIntervalMs = 200;
} // namespace
PacketRouter::PacketRouter()
: last_send_module_(nullptr),
last_remb_time_ms_(rtc::TimeMillis()),
last_send_bitrate_bps_(0),
bitrate_bps_(0),
max_bitrate_bps_(std::numeric_limits<decltype(max_bitrate_bps_)>::max()),
active_remb_module_(nullptr),
transport_seq_(0) {}
PacketRouter::~PacketRouter() {
RTC_DCHECK(rtp_send_modules_.empty());
RTC_DCHECK(rtcp_feedback_senders_.empty());
RTC_DCHECK(sender_remb_candidates_.empty());
RTC_DCHECK(receiver_remb_candidates_.empty());
RTC_DCHECK(active_remb_module_ == nullptr);
}
void PacketRouter::AddSendRtpModule(RtpRtcp* rtp_module, bool remb_candidate) {
rtc::CritScope cs(&modules_crit_);
RTC_DCHECK(std::find(rtp_send_modules_.begin(), rtp_send_modules_.end(),
rtp_module) == rtp_send_modules_.end());
// Put modules which can use regular payload packets (over rtx) instead of
// padding first as it's less of a waste
if ((rtp_module->RtxSendStatus() & kRtxRedundantPayloads) > 0) {
rtp_send_modules_.push_front(rtp_module);
} else {
rtp_send_modules_.push_back(rtp_module);
}
if (remb_candidate) {
AddRembModuleCandidate(rtp_module, /* media_sender = */ true);
}
}
void PacketRouter::RemoveSendRtpModule(RtpRtcp* rtp_module) {
rtc::CritScope cs(&modules_crit_);
MaybeRemoveRembModuleCandidate(rtp_module, /* media_sender = */ true);
auto it =
std::find(rtp_send_modules_.begin(), rtp_send_modules_.end(), rtp_module);
RTC_DCHECK(it != rtp_send_modules_.end());
rtp_send_modules_.erase(it);
if (last_send_module_ == rtp_module) {
last_send_module_ = nullptr;
}
}
void PacketRouter::AddReceiveRtpModule(RtcpFeedbackSenderInterface* rtcp_sender,
bool remb_candidate) {
rtc::CritScope cs(&modules_crit_);
RTC_DCHECK(std::find(rtcp_feedback_senders_.begin(),
rtcp_feedback_senders_.end(),
rtcp_sender) == rtcp_feedback_senders_.end());
rtcp_feedback_senders_.push_back(rtcp_sender);
if (remb_candidate) {
AddRembModuleCandidate(rtcp_sender, /* media_sender = */ false);
}
}
void PacketRouter::RemoveReceiveRtpModule(
RtcpFeedbackSenderInterface* rtcp_sender) {
rtc::CritScope cs(&modules_crit_);
MaybeRemoveRembModuleCandidate(rtcp_sender, /* media_sender = */ false);
auto it = std::find(rtcp_feedback_senders_.begin(),
rtcp_feedback_senders_.end(), rtcp_sender);
RTC_DCHECK(it != rtcp_feedback_senders_.end());
rtcp_feedback_senders_.erase(it);
}
bool PacketRouter::TimeToSendPacket(uint32_t ssrc,
uint16_t sequence_number,
int64_t capture_timestamp,
bool retransmission,
const PacedPacketInfo& pacing_info) {
rtc::CritScope cs(&modules_crit_);
for (auto* rtp_module : rtp_send_modules_) {
if (!rtp_module->SendingMedia()) {
continue;
}
if (ssrc == rtp_module->SSRC() || ssrc == rtp_module->FlexfecSsrc()) {
if ((rtp_module->RtxSendStatus() & kRtxRedundantPayloads) &&
rtp_module->HasBweExtensions()) {
// This is now the last module to send media, and has the desired
// properties needed for payload based padding. Cache it for later use.
last_send_module_ = rtp_module;
}
return rtp_module->TimeToSendPacket(ssrc, sequence_number,
capture_timestamp, retransmission,
pacing_info);
}
}
return true;
}
size_t PacketRouter::TimeToSendPadding(size_t bytes_to_send,
const PacedPacketInfo& pacing_info) {
size_t total_bytes_sent = 0;
rtc::CritScope cs(&modules_crit_);
// First try on the last rtp module to have sent media. This increases the
// the chance that any payload based padding will be useful as it will be
// somewhat distributed over modules according the packet rate, even if it
// will be more skewed towards the highest bitrate stream. At the very least
// this prevents sending payload padding on a disabled stream where it's
// guaranteed not to be useful.
if (last_send_module_ != nullptr) {
RTC_DCHECK(std::find(rtp_send_modules_.begin(), rtp_send_modules_.end(),
last_send_module_) != rtp_send_modules_.end());
RTC_DCHECK(last_send_module_->HasBweExtensions());
total_bytes_sent += last_send_module_->TimeToSendPadding(
bytes_to_send - total_bytes_sent, pacing_info);
if (total_bytes_sent >= bytes_to_send) {
return total_bytes_sent;
}
}
// Rtp modules are ordered by which stream can most benefit from padding.
for (RtpRtcp* module : rtp_send_modules_) {
if (module->SendingMedia() && module->HasBweExtensions()) {
size_t bytes_sent = module->TimeToSendPadding(
bytes_to_send - total_bytes_sent, pacing_info);
total_bytes_sent += bytes_sent;
if (total_bytes_sent >= bytes_to_send)
break;
}
}
return total_bytes_sent;
}
void PacketRouter::SetTransportWideSequenceNumber(uint16_t sequence_number) {
rtc::AtomicOps::ReleaseStore(&transport_seq_, sequence_number);
}
uint16_t PacketRouter::AllocateSequenceNumber() {
int prev_seq = rtc::AtomicOps::AcquireLoad(&transport_seq_);
int desired_prev_seq;
int new_seq;
do {
desired_prev_seq = prev_seq;
new_seq = (desired_prev_seq + 1) & 0xFFFF;
// Note: CompareAndSwap returns the actual value of transport_seq at the
// time the CAS operation was executed. Thus, if prev_seq is returned, the
// operation was successful - otherwise we need to retry. Saving the
// return value saves us a load on retry.
prev_seq = rtc::AtomicOps::CompareAndSwap(&transport_seq_, desired_prev_seq,
new_seq);
} while (prev_seq != desired_prev_seq);
return new_seq;
}
void PacketRouter::OnReceiveBitrateChanged(const std::vector<uint32_t>& ssrcs,
uint32_t bitrate_bps) {
// % threshold for if we should send a new REMB asap.
const int64_t kSendThresholdPercent = 97;
// TODO(danilchap): Remove receive_bitrate_bps variable and the cast
// when OnReceiveBitrateChanged takes bitrate as int64_t.
int64_t receive_bitrate_bps = static_cast<int64_t>(bitrate_bps);
int64_t now_ms = rtc::TimeMillis();
{
rtc::CritScope lock(&remb_crit_);
// If we already have an estimate, check if the new total estimate is below
// kSendThresholdPercent of the previous estimate.
if (last_send_bitrate_bps_ > 0) {
int64_t new_remb_bitrate_bps =
last_send_bitrate_bps_ - bitrate_bps_ + receive_bitrate_bps;
if (new_remb_bitrate_bps <
kSendThresholdPercent * last_send_bitrate_bps_ / 100) {
// The new bitrate estimate is less than kSendThresholdPercent % of the
// last report. Send a REMB asap.
last_remb_time_ms_ = now_ms - kRembSendIntervalMs;
}
}
bitrate_bps_ = receive_bitrate_bps;
if (now_ms - last_remb_time_ms_ < kRembSendIntervalMs) {
return;
}
// NOTE: Updated if we intend to send the data; we might not have
// a module to actually send it.
last_remb_time_ms_ = now_ms;
last_send_bitrate_bps_ = receive_bitrate_bps;
// Cap the value to send in remb with configured value.
receive_bitrate_bps = std::min(receive_bitrate_bps, max_bitrate_bps_);
}
SendRemb(receive_bitrate_bps, ssrcs);
}
void PacketRouter::SetMaxDesiredReceiveBitrate(int64_t bitrate_bps) {
RTC_DCHECK_GE(bitrate_bps, 0);
{
rtc::CritScope lock(&remb_crit_);
max_bitrate_bps_ = bitrate_bps;
if (rtc::TimeMillis() - last_remb_time_ms_ < kRembSendIntervalMs &&
last_send_bitrate_bps_ > 0 &&
last_send_bitrate_bps_ <= max_bitrate_bps_) {
// Recent measured bitrate is already below the cap.
return;
}
}
SendRemb(bitrate_bps, /*ssrcs=*/{});
}
bool PacketRouter::SendRemb(int64_t bitrate_bps,
const std::vector<uint32_t>& ssrcs) {
rtc::CritScope lock(&modules_crit_);
if (!active_remb_module_) {
return false;
}
// The Add* and Remove* methods above ensure that REMB is disabled on all
// other modules, because otherwise, they will send REMB with stale info.
active_remb_module_->SetRemb(bitrate_bps, ssrcs);
return true;
}
bool PacketRouter::SendTransportFeedback(rtcp::TransportFeedback* packet) {
rtc::CritScope cs(&modules_crit_);
// Prefer send modules.
for (auto* rtp_module : rtp_send_modules_) {
packet->SetSenderSsrc(rtp_module->SSRC());
if (rtp_module->SendFeedbackPacket(*packet)) {
return true;
}
}
for (auto* rtcp_sender : rtcp_feedback_senders_) {
packet->SetSenderSsrc(rtcp_sender->SSRC());
if (rtcp_sender->SendFeedbackPacket(*packet)) {
return true;
}
}
return false;
}
void PacketRouter::AddRembModuleCandidate(
RtcpFeedbackSenderInterface* candidate_module,
bool media_sender) {
RTC_DCHECK(candidate_module);
std::vector<RtcpFeedbackSenderInterface*>& candidates =
media_sender ? sender_remb_candidates_ : receiver_remb_candidates_;
RTC_DCHECK(std::find(candidates.cbegin(), candidates.cend(),
candidate_module) == candidates.cend());
candidates.push_back(candidate_module);
DetermineActiveRembModule();
}
void PacketRouter::MaybeRemoveRembModuleCandidate(
RtcpFeedbackSenderInterface* candidate_module,
bool media_sender) {
RTC_DCHECK(candidate_module);
std::vector<RtcpFeedbackSenderInterface*>& candidates =
media_sender ? sender_remb_candidates_ : receiver_remb_candidates_;
auto it = std::find(candidates.begin(), candidates.end(), candidate_module);
if (it == candidates.end()) {
return; // Function called due to removal of non-REMB-candidate module.
}
if (*it == active_remb_module_) {
UnsetActiveRembModule();
}
candidates.erase(it);
DetermineActiveRembModule();
}
void PacketRouter::UnsetActiveRembModule() {
RTC_CHECK(active_remb_module_);
active_remb_module_->UnsetRemb();
active_remb_module_ = nullptr;
}
void PacketRouter::DetermineActiveRembModule() {
// Sender modules take precedence over receiver modules, because SRs (sender
// reports) are sent more frequently than RR (receiver reports).
// When adding the first sender module, we should change the active REMB
// module to be that. Otherwise, we remain with the current active module.
RtcpFeedbackSenderInterface* new_active_remb_module;
if (!sender_remb_candidates_.empty()) {
new_active_remb_module = sender_remb_candidates_.front();
} else if (!receiver_remb_candidates_.empty()) {
new_active_remb_module = receiver_remb_candidates_.front();
} else {
new_active_remb_module = nullptr;
}
if (new_active_remb_module != active_remb_module_ && active_remb_module_) {
UnsetActiveRembModule();
}
active_remb_module_ = new_active_remb_module;
}
} // namespace webrtc