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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/remote_bitrate_estimator/remote_estimator_proxy.h"
#include <algorithm>
#include <limits>
#include <memory>
#include <utility>
#include "api/units/data_size.h"
#include "modules/rtp_rtcp/source/rtcp_packet/remote_estimate.h"
#include "modules/rtp_rtcp/source/rtcp_packet/transport_feedback.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_minmax.h"
#include "system_wrappers/include/clock.h"
namespace webrtc {
namespace {
// The maximum allowed value for a timestamp in milliseconds. This is lower
// than the numerical limit since we often convert to microseconds.
static constexpr int64_t kMaxTimeMs =
std::numeric_limits<int64_t>::max() / 1000;
TimeDelta GetAbsoluteSendTimeDelta(uint32_t new_sendtime,
uint32_t previous_sendtime) {
static constexpr uint32_t kWrapAroundPeriod = 0x0100'0000;
RTC_DCHECK_LT(new_sendtime, kWrapAroundPeriod);
RTC_DCHECK_LT(previous_sendtime, kWrapAroundPeriod);
uint32_t delta = (new_sendtime - previous_sendtime) % kWrapAroundPeriod;
if (delta >= kWrapAroundPeriod / 2) {
// absolute send time wraps around, thus treat deltas larger than half of
// the wrap around period as negative. Ignore reordering of packets and
// treat them as they have approximately the same send time.
return TimeDelta::Zero();
}
return TimeDelta::Micros(int64_t{delta} * 1'000'000 / (1 << 18));
}
} // namespace
RemoteEstimatorProxy::RemoteEstimatorProxy(
TransportFeedbackSender feedback_sender,
const FieldTrialsView* key_value_config,
NetworkStateEstimator* network_state_estimator)
: feedback_sender_(std::move(feedback_sender)),
send_config_(key_value_config),
last_process_time_(Timestamp::MinusInfinity()),
network_state_estimator_(network_state_estimator),
media_ssrc_(0),
feedback_packet_count_(0),
packet_overhead_(DataSize::Zero()),
send_interval_(send_config_.default_interval.Get()),
send_periodic_feedback_(true),
previous_abs_send_time_(0),
abs_send_timestamp_(Timestamp::Zero()) {
RTC_LOG(LS_INFO)
<< "Maximum interval between transport feedback RTCP messages (ms): "
<< send_config_.max_interval->ms();
}
RemoteEstimatorProxy::~RemoteEstimatorProxy() {}
void RemoteEstimatorProxy::MaybeCullOldPackets(int64_t sequence_number,
Timestamp arrival_time) {
if (periodic_window_start_seq_ >=
packet_arrival_times_.end_sequence_number() &&
arrival_time - Timestamp::Zero() >= send_config_.back_window.Get()) {
// Start new feedback packet, cull old packets.
packet_arrival_times_.RemoveOldPackets(
sequence_number, arrival_time - send_config_.back_window.Get());
}
}
void RemoteEstimatorProxy::IncomingPacket(int64_t arrival_time_ms,
size_t payload_size,
const RTPHeader& header) {
if (arrival_time_ms < 0 || arrival_time_ms >= kMaxTimeMs) {
RTC_LOG(LS_WARNING) << "Arrival time out of bounds: " << arrival_time_ms;
return;
}
Packet packet = {.arrival_time = Timestamp::Millis(arrival_time_ms),
.size = DataSize::Bytes(header.headerLength + payload_size),
.ssrc = header.ssrc};
if (header.extension.hasTransportSequenceNumber) {
packet.transport_sequence_number = header.extension.transportSequenceNumber;
}
if (header.extension.hasAbsoluteSendTime) {
packet.absolute_send_time_24bits = header.extension.absoluteSendTime;
}
packet.feedback_request = header.extension.feedback_request;
IncomingPacket(packet);
}
void RemoteEstimatorProxy::IncomingPacket(Packet packet) {
MutexLock lock(&lock_);
media_ssrc_ = packet.ssrc;
int64_t seq = 0;
if (packet.transport_sequence_number.has_value()) {
seq = unwrapper_.Unwrap(*packet.transport_sequence_number);
if (send_periodic_feedback_) {
MaybeCullOldPackets(seq, packet.arrival_time);
if (!periodic_window_start_seq_ || seq < *periodic_window_start_seq_) {
periodic_window_start_seq_ = seq;
}
}
// We are only interested in the first time a packet is received.
if (packet_arrival_times_.has_received(seq)) {
return;
}
packet_arrival_times_.AddPacket(seq, packet.arrival_time);
// Limit the range of sequence numbers to send feedback for.
if (!periodic_window_start_seq_.has_value() ||
periodic_window_start_seq_.value() <
packet_arrival_times_.begin_sequence_number()) {
periodic_window_start_seq_ =
packet_arrival_times_.begin_sequence_number();
}
if (packet.feedback_request) {
// Send feedback packet immediately.
SendFeedbackOnRequest(seq, *packet.feedback_request);
}
}
if (network_state_estimator_ && packet.absolute_send_time_24bits) {
PacketResult packet_result;
packet_result.receive_time = packet.arrival_time;
abs_send_timestamp_ += GetAbsoluteSendTimeDelta(
*packet.absolute_send_time_24bits, previous_abs_send_time_);
previous_abs_send_time_ = *packet.absolute_send_time_24bits;
packet_result.sent_packet.send_time = abs_send_timestamp_;
packet_result.sent_packet.size = packet.size + packet_overhead_;
packet_result.sent_packet.sequence_number = seq;
network_state_estimator_->OnReceivedPacket(packet_result);
}
}
TimeDelta RemoteEstimatorProxy::Process(Timestamp now) {
MutexLock lock(&lock_);
if (!send_periodic_feedback_) {
return TimeDelta::PlusInfinity();
}
Timestamp next_process_time = last_process_time_ + send_interval_;
if (now >= next_process_time) {
last_process_time_ = now;
SendPeriodicFeedbacks();
return send_interval_;
}
return next_process_time - now;
}
void RemoteEstimatorProxy::OnBitrateChanged(int bitrate_bps) {
// TwccReportSize = Ipv4(20B) + UDP(8B) + SRTP(10B) +
// AverageTwccReport(30B)
// TwccReport size at 50ms interval is 24 byte.
// TwccReport size at 250ms interval is 36 byte.
// AverageTwccReport = (TwccReport(50ms) + TwccReport(250ms)) / 2
constexpr DataSize kTwccReportSize = DataSize::Bytes(20 + 8 + 10 + 30);
const DataRate kMinTwccRate =
kTwccReportSize / send_config_.max_interval.Get();
// Let TWCC reports occupy 5% of total bandwidth.
DataRate twcc_bitrate =
DataRate::BitsPerSec(send_config_.bandwidth_fraction * bitrate_bps);
// Check upper send_interval bound by checking bitrate to avoid overflow when
// dividing by small bitrate, in particular avoid dividing by zero bitrate.
TimeDelta send_interval = twcc_bitrate <= kMinTwccRate
? send_config_.max_interval.Get()
: std::max(kTwccReportSize / twcc_bitrate,
send_config_.min_interval.Get());
MutexLock lock(&lock_);
send_interval_ = send_interval;
}
void RemoteEstimatorProxy::SetSendPeriodicFeedback(
bool send_periodic_feedback) {
MutexLock lock(&lock_);
send_periodic_feedback_ = send_periodic_feedback;
}
void RemoteEstimatorProxy::SetTransportOverhead(DataSize overhead_per_packet) {
MutexLock lock(&lock_);
packet_overhead_ = overhead_per_packet;
}
void RemoteEstimatorProxy::SendPeriodicFeedbacks() {
// `periodic_window_start_seq_` is the first sequence number to include in
// the current feedback packet. Some older may still be in the map, in case
// a reordering happens and we need to retransmit them.
if (!periodic_window_start_seq_)
return;
std::unique_ptr<rtcp::RemoteEstimate> remote_estimate;
if (network_state_estimator_) {
absl::optional<NetworkStateEstimate> state_estimate =
network_state_estimator_->GetCurrentEstimate();
if (state_estimate) {
remote_estimate = std::make_unique<rtcp::RemoteEstimate>();
remote_estimate->SetEstimate(state_estimate.value());
}
}
int64_t packet_arrival_times_end_seq =
packet_arrival_times_.end_sequence_number();
while (periodic_window_start_seq_ < packet_arrival_times_end_seq) {
auto feedback_packet = MaybeBuildFeedbackPacket(
/*include_timestamps=*/true, periodic_window_start_seq_.value(),
packet_arrival_times_end_seq,
/*is_periodic_update=*/true);
if (feedback_packet == nullptr) {
break;
}
RTC_DCHECK(feedback_sender_ != nullptr);
std::vector<std::unique_ptr<rtcp::RtcpPacket>> packets;
if (remote_estimate) {
packets.push_back(std::move(remote_estimate));
}
packets.push_back(std::move(feedback_packet));
feedback_sender_(std::move(packets));
// Note: Don't erase items from packet_arrival_times_ after sending, in
// case they need to be re-sent after a reordering. Removal will be
// handled by OnPacketArrival once packets are too old.
}
}
void RemoteEstimatorProxy::SendFeedbackOnRequest(
int64_t sequence_number,
const FeedbackRequest& feedback_request) {
if (feedback_request.sequence_count == 0) {
return;
}
int64_t first_sequence_number =
sequence_number - feedback_request.sequence_count + 1;
auto feedback_packet = MaybeBuildFeedbackPacket(
feedback_request.include_timestamps, first_sequence_number,
sequence_number + 1, /*is_periodic_update=*/false);
// This is called when a packet has just been added.
RTC_DCHECK(feedback_packet != nullptr);
// Clear up to the first packet that is included in this feedback packet.
packet_arrival_times_.EraseTo(first_sequence_number);
RTC_DCHECK(feedback_sender_ != nullptr);
std::vector<std::unique_ptr<rtcp::RtcpPacket>> packets;
packets.push_back(std::move(feedback_packet));
feedback_sender_(std::move(packets));
}
std::unique_ptr<rtcp::TransportFeedback>
RemoteEstimatorProxy::MaybeBuildFeedbackPacket(
bool include_timestamps,
int64_t begin_sequence_number_inclusive,
int64_t end_sequence_number_exclusive,
bool is_periodic_update) {
RTC_DCHECK_LT(begin_sequence_number_inclusive, end_sequence_number_exclusive);
int64_t start_seq =
packet_arrival_times_.clamp(begin_sequence_number_inclusive);
int64_t end_seq = packet_arrival_times_.clamp(end_sequence_number_exclusive);
// Create the packet on demand, as it's not certain that there are packets
// in the range that have been received.
std::unique_ptr<rtcp::TransportFeedback> feedback_packet = nullptr;
int64_t next_sequence_number = begin_sequence_number_inclusive;
for (int64_t seq = start_seq; seq < end_seq; ++seq) {
PacketArrivalTimeMap::PacketArrivalTime packet =
packet_arrival_times_.FindNextAtOrAfter(seq);
seq = packet.sequence_number;
if (seq >= end_seq) {
break;
}
if (feedback_packet == nullptr) {
feedback_packet =
std::make_unique<rtcp::TransportFeedback>(include_timestamps);
feedback_packet->SetMediaSsrc(media_ssrc_);
// Base sequence number is the expected first sequence number. This is
// known, but we might not have actually received it, so the base time
// shall be the time of the first received packet in the feedback.
feedback_packet->SetBase(
static_cast<uint16_t>(begin_sequence_number_inclusive & 0xFFFF),
packet.arrival_time);
feedback_packet->SetFeedbackSequenceNumber(feedback_packet_count_++);
}
if (!feedback_packet->AddReceivedPacket(static_cast<uint16_t>(seq & 0xFFFF),
packet.arrival_time)) {
// Could not add timestamp, feedback packet might be full. Return and
// try again with a fresh packet.
break;
}
next_sequence_number = seq + 1;
}
if (is_periodic_update) {
periodic_window_start_seq_ = next_sequence_number;
}
return feedback_packet;
}
} // namespace webrtc