テキスト比較

2 つのテキストファイルの違いを見つける

Real-time diff

Unified diff

Collapse lines

Highlight change

Syntax highlighting

ツール

Diffchecker Desktop The most secure way to run Diffchecker. Get the Diffchecker Desktop app: your diffs never leave your computer!Get Desktop

aimd_rate_control.cc

Created 5 years agoDiff never expires

Lines
Total
Removed

Words
Total
Removed

To continue using this feature, upgrade to Diffchecker Pro View Pricing

444 lines

Lines
Total
Added

Words
Total
Added

To continue using this feature, upgrade to Diffchecker Pro View Pricing

425 lines

* 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.

#define MS_CLASS "webrtc::AimdRateControl"

// #define MS_LOG_DEV_LEVEL 3

#include "modules/remote_bitrate_estimator/aimd_rate_control.h"

Text moved from lines 23-30

#include <inttypes.h>

#include <algorithm>

#include <cassert>

#include <cmath>

#include <cstdio>

#include <string>

#include "absl/strings/match.h"

#include "api/transport/network_types.h"

#include "api/units/data_rate.h"

#include "modules/remote_bitrate_estimator/include/bwe_defines.h"

#include "modules/remote_bitrate_estimator/overuse_detector.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 "Logger.hpp"

Text moved to lines 13-20

#include "MediaSoupErrors.hpp"

#include <inttypes.h>

#include <algorithm>

#include <cmath>

#include <cstdio>

#include <string>

namespace webrtc {

namespace {

constexpr TimeDelta kDefaultRtt = TimeDelta::Millis<200>();

constexpr TimeDelta kDefaultRtt = TimeDelta::Millis(200);

constexpr double kDefaultBackoffFactor = 0.85;

constexpr char kBweBackOffFactorExperiment[] = "WebRTC-BweBackOffFactor";

bool IsEnabled(const WebRtcKeyValueConfig& field_trials,

absl::string_view key) {

return field_trials.Lookup(key).find("Enabled") == 0;

return absl::StartsWith(field_trials.Lookup(key), "Enabled");

}

bool IsNotDisabled(const WebRtcKeyValueConfig& field_trials,

absl::string_view key) {

return !absl::StartsWith(field_trials.Lookup(key), "Disabled");

}

double ReadBackoffFactor(const WebRtcKeyValueConfig& key_value_config) {

std::string experiment_string =

key_value_config.Lookup(kBweBackOffFactorExperiment);

double backoff_factor;

int parsed_values =

sscanf(experiment_string.c_str(), "Enabled-%lf", &backoff_factor);

if (parsed_values == 1) {

if (backoff_factor >= 1.0) {

MS_WARN_TAG(bwe, "Back-off factor must be less than 1.");

RTC_LOG(WARNING) << "Back-off factor must be less than 1.";

} else if (backoff_factor <= 0.0) {

MS_WARN_TAG(bwe, "Back-off factor must be greater than 0.");

RTC_LOG(WARNING) << "Back-off factor must be greater than 0.";

} else {

return backoff_factor;

}

RTC_LOG(LS_WARNING) << "Failed to parse parameters for AimdRateControl "

MS_WARN_TAG(bwe, "Failed to parse parameters for AimdRateControl experiment from field trial string. Using default.");

"experiment from field trial string. Using default.";

return kDefaultBackoffFactor;

}

} // namespace

AimdRateControl::AimdRateControl(const WebRtcKeyValueConfig* key_value_config)

: AimdRateControl(key_value_config, /* send_side =*/false) {}

AimdRateControl::AimdRateControl(const WebRtcKeyValueConfig* key_value_config,

bool send_side)

: min_configured_bitrate_(congestion_controller::GetMinBitrate()),

max_configured_bitrate_(DataRate::kbps(30000)),

max_configured_bitrate_(DataRate::KilobitsPerSec(30000)),

current_bitrate_(max_configured_bitrate_),

latest_estimated_throughput_(current_bitrate_),

link_capacity_(),

rate_control_state_(kRcHold),

time_last_bitrate_change_(Timestamp::MinusInfinity()),

time_last_bitrate_decrease_(Timestamp::MinusInfinity()),

time_first_throughput_estimate_(Timestamp::MinusInfinity()),

bitrate_is_initialized_(false),

beta_(IsEnabled(*key_value_config, kBweBackOffFactorExperiment)

? ReadBackoffFactor(*key_value_config)

: kDefaultBackoffFactor),

in_alr_(false),

rtt_(kDefaultRtt),

send_side_(send_side),

in_experiment_(!AdaptiveThresholdExperimentIsDisabled(*key_value_config)),

no_bitrate_increase_in_alr_(

IsEnabled(*key_value_config,

"WebRTC-DontIncreaseDelayBasedBweInAlr")),

smoothing_experiment_(false),

estimate_bounded_backoff_(

IsEnabled(*key_value_config, "WebRTC-Bwe-EstimateBoundedBackoff")),

IsNotDisabled(*key_value_config,

"WebRTC-Bwe-EstimateBoundedBackoff")),

estimate_bounded_increase_(

IsEnabled(*key_value_config, "WebRTC-Bwe-EstimateBoundedIncrease")),

IsNotDisabled(*key_value_config,

"WebRTC-Bwe-EstimateBoundedIncrease")),

initial_backoff_interval_("initial_backoff_interval"),

low_throughput_threshold_("low_throughput", DataRate::Zero()),

link_capacity_fix_("link_capacity_fix") {

capacity_deviation_ratio_threshold_("cap_thr", 0.2),

capacity_limit_deviation_factor_("cap_lim", 1) {

// E.g

// WebRTC-BweAimdRateControlConfig/initial_backoff_interval:100ms,

// WebRTC-BweAimdRateControlConfig/initial_backoff_interval:100ms/

// low_throughput:50kbps/

ParseFieldTrial({&initial_backoff_interval_, &link_capacity_fix_},

ParseFieldTrial({&initial_backoff_interval_, &low_throughput_threshold_},

key_value_config->Lookup("WebRTC-BweAimdRateControlConfig"));

if (initial_backoff_interval_) {

MS_DEBUG_TAG(bwe, "Using aimd rate control with initial back-off interval: %s",

RTC_LOG(LS_INFO) << "Using aimd rate control with initial back-off interval"

ToString(*initial_backoff_interval_).c_str());

" "

<< ToString(*initial_backoff_interval_) << ".";

}

MS_DEBUG_TAG(bwe, "Using aimd rate control with back off factor: %f ", beta_);

RTC_LOG(LS_INFO) << "Using aimd rate control with back off factor " << beta_;

ParseFieldTrial(

{&capacity_deviation_ratio_threshold_, &capacity_limit_deviation_factor_},

key_value_config->Lookup("WebRTC-Bwe-AimdRateControl-NetworkState"));

}

AimdRateControl::~AimdRateControl() {}

void AimdRateControl::SetStartBitrate(DataRate start_bitrate) {

current_bitrate_ = start_bitrate;

latest_estimated_throughput_ = current_bitrate_;

bitrate_is_initialized_ = true;

}

void AimdRateControl::SetMinBitrate(DataRate min_bitrate) {

MS_DEBUG_DEV("[min_bitrate:%" PRIi64 "]", min_bitrate.bps());

min_configured_bitrate_ = min_bitrate;

current_bitrate_ = std::max(min_bitrate, current_bitrate_);

}

bool AimdRateControl::ValidEstimate() const {

return bitrate_is_initialized_;

}

TimeDelta AimdRateControl::GetFeedbackInterval() const {

// Estimate how often we can send RTCP if we allocate up to 5% of bandwidth

// to feedback.

const DataSize kRtcpSize = DataSize::bytes(80);

const DataSize kRtcpSize = DataSize::Bytes(80);

const DataRate rtcp_bitrate = current_bitrate_ * 0.05;

const TimeDelta interval = kRtcpSize / rtcp_bitrate;

const TimeDelta kMinFeedbackInterval = TimeDelta::ms(200);

const TimeDelta kMinFeedbackInterval = TimeDelta::Millis(200);

const TimeDelta kMaxFeedbackInterval = TimeDelta::ms(1000);

const TimeDelta kMaxFeedbackInterval = TimeDelta::Millis(1000);

return interval.Clamped(kMinFeedbackInterval, kMaxFeedbackInterval);

}

bool AimdRateControl::TimeToReduceFurther(Timestamp at_time,

DataRate estimated_throughput) const {

const TimeDelta bitrate_reduction_interval =

rtt_.Clamped(TimeDelta::ms(10), TimeDelta::ms(200));

rtt_.Clamped(TimeDelta::Millis(10), TimeDelta::Millis(200));

if (at_time - time_last_bitrate_change_ >= bitrate_reduction_interval) {

return true;

}

if (ValidEstimate()) {

// TODO(terelius/holmer): Investigate consequences of increasing

// the threshold to 0.95 * LatestEstimate().

const DataRate threshold = 0.5 * LatestEstimate();

return estimated_throughput < threshold;

}

return false;

}

bool AimdRateControl::InitialTimeToReduceFurther(Timestamp at_time) const {

if (!initial_backoff_interval_) {

return ValidEstimate() &&

TimeToReduceFurther(at_time,

LatestEstimate() / 2 - DataRate::bps(1));

LatestEstimate() / 2 - DataRate::BitsPerSec(1));

}

// TODO(terelius): We could use the RTT (clamped to suitable limits) instead

// of a fixed bitrate_reduction_interval.

if (time_last_bitrate_decrease_.IsInfinite() ||

at_time - time_last_bitrate_decrease_ >= *initial_backoff_interval_) {

return true;

}

return false;

}

DataRate AimdRateControl::LatestEstimate() const {

return current_bitrate_;

}

void AimdRateControl::SetRtt(TimeDelta rtt) {

rtt_ = rtt;

}

DataRate AimdRateControl::Update(const RateControlInput* input,

Timestamp at_time) {

// RTC_CHECK(input);

RTC_CHECK(input);

// Set the initial bit rate value to what we're receiving the first half

// second.

// TODO(bugs.webrtc.org/9379): The comment above doesn't match to the code.

if (!bitrate_is_initialized_) {

const TimeDelta kInitializationTime = TimeDelta::seconds(5);

const TimeDelta kInitializationTime = TimeDelta::Seconds(5);

// RTC_DCHECK_LE(kBitrateWindowMs, kInitializationTime.ms());

RTC_DCHECK_LE(kBitrateWindowMs, kInitializationTime.ms());

if (time_first_throughput_estimate_.IsInfinite()) {

if (input->estimated_throughput)

time_first_throughput_estimate_ = at_time;

} else if (at_time - time_first_throughput_estimate_ >

kInitializationTime &&

input->estimated_throughput) {

current_bitrate_ = *input->estimated_throughput;

bitrate_is_initialized_ = true;

}

current_bitrate_ = ChangeBitrate(current_bitrate_, *input, at_time);

ChangeBitrate(*input, at_time);

return current_bitrate_;

}

void AimdRateControl::SetInApplicationLimitedRegion(bool in_alr) {

in_alr_ = in_alr;

}

void AimdRateControl::SetEstimate(DataRate bitrate, Timestamp at_time) {

bitrate_is_initialized_ = true;

DataRate prev_bitrate = current_bitrate_;

current_bitrate_ = ClampBitrate(bitrate, bitrate);

current_bitrate_ = ClampBitrate(bitrate);

time_last_bitrate_change_ = at_time;

if (current_bitrate_ < prev_bitrate) {

time_last_bitrate_decrease_ = at_time;

}

void AimdRateControl::SetNetworkStateEstimate(

const absl::optional<NetworkStateEstimate>& estimate) {

network_estimate_ = estimate;

}

double AimdRateControl::GetNearMaxIncreaseRateBpsPerSecond() const {

// RTC_DCHECK(!current_bitrate_.IsZero());

RTC_DCHECK(!current_bitrate_.IsZero());

const TimeDelta kFrameInterval = TimeDelta::seconds(1) / 30;

const TimeDelta kFrameInterval = TimeDelta::Seconds(1) / 30;

DataSize frame_size = current_bitrate_ * kFrameInterval;

const DataSize kPacketSize = DataSize::bytes(1200);

const DataSize kPacketSize = DataSize::Bytes(1200);

double packets_per_frame = std::ceil(frame_size / kPacketSize);

DataSize avg_packet_size = frame_size / packets_per_frame;

// Approximate the over-use estimator delay to 100 ms.

TimeDelta response_time = rtt_ + TimeDelta::ms(100);

TimeDelta response_time = rtt_ + TimeDelta::Millis(100);

if (in_experiment_)

response_time = response_time * 2;

double increase_rate_bps_per_second =

(avg_packet_size / response_time).bps<double>();

double kMinIncreaseRateBpsPerSecond = 4000;

return std::max(kMinIncreaseRateBpsPerSecond, increase_rate_bps_per_second);

}

TimeDelta AimdRateControl::GetExpectedBandwidthPeriod() const {

const TimeDelta kMinPeriod =

const TimeDelta kMinPeriod = TimeDelta::Seconds(2);

smoothing_experiment_ ? TimeDelta::ms(500) : TimeDelta::seconds(2);

const TimeDelta kDefaultPeriod = TimeDelta::Seconds(3);

const TimeDelta kDefaultPeriod = TimeDelta::seconds(3);

const TimeDelta kMaxPeriod = TimeDelta::Seconds(50);

const TimeDelta kMaxPeriod = TimeDelta::seconds(50);

double increase_rate_bps_per_second = GetNearMaxIncreaseRateBpsPerSecond();

if (!last_decrease_)

return smoothing_experiment_ ? kMinPeriod : kDefaultPeriod;

return kDefaultPeriod;

double time_to_recover_decrease_seconds =

last_decrease_->bps() / increase_rate_bps_per_second;

TimeDelta period = TimeDelta::seconds(time_to_recover_decrease_seconds);

TimeDelta period = TimeDelta::Seconds(time_to_recover_decrease_seconds);

return period.Clamped(kMinPeriod, kMaxPeriod);

}

DataRate AimdRateControl::ChangeBitrate(DataRate new_bitrate,

void AimdRateControl::ChangeBitrate(const RateControlInput& input,

const RateControlInput& input,

Timestamp at_time) {

absl::optional<DataRate> new_bitrate;

DataRate estimated_throughput =

input.estimated_throughput.value_or(latest_estimated_throughput_);

if (input.estimated_throughput)

latest_estimated_throughput_ = *input.estimated_throughput;

// An over-use should always trigger us to reduce the bitrate, even though

// we have not yet established our first estimate. By acting on the over-use,

// we will end up with a valid estimate.

if (!bitrate_is_initialized_ &&

input.bw_state != BandwidthUsage::kBwOverusing)

return current_bitrate_;

return;

ChangeState(input, at_time);

// We limit the new bitrate based on the troughput to avoid unlimited bitrate

// increases. We allow a bit more lag at very low rates to not too easily get

// stuck if the encoder produces uneven outputs.

const DataRate troughput_based_limit =

1.5 * estimated_throughput + DataRate::KilobitsPerSec(10);

switch (rate_control_state_) {

case kRcHold:

break;

case kRcIncrease:

if (estimated_throughput > link_capacity_.UpperBound())

link_capacity_.Reset();

// Do not increase the delay based estimate in alr since the estimator

// will not be able to get transport feedback necessary to detect if

// the new estimate is correct.

if (!(send_side_ && in_alr_ && no_bitrate_increase_in_alr_)) {

// If we have previously increased above the limit (for instance due to

// probing), we don't allow further changes.

if (current_bitrate_ < troughput_based_limit &&

!(send_side_ && in_alr_ && no_bitrate_increase_in_alr_)) {

DataRate increased_bitrate = DataRate::MinusInfinity();

if (link_capacity_.has_estimate()) {

// The link_capacity estimate is reset if the measured throughput

// is too far from the estimate. We can therefore assume that our

// target rate is reasonably close to link capacity and use additive

// increase.

DataRate additive_increase =

AdditiveRateIncrease(at_time, time_last_bitrate_change_);

new_bitrate += additive_increase;

increased_bitrate = current_bitrate_ + additive_increase;

} else {

// If we don't have an estimate of the link capacity, use faster ramp

// up to discover the capacity.

DataRate multiplicative_increase = MultiplicativeRateIncrease(

at_time, time_last_bitrate_change_, new_bitrate);

at_time, time_last_bitrate_change_, current_bitrate_);

new_bitrate += multiplicative_increase;

increased_bitrate = current_bitrate_ + multiplicative_increase;

}

new_bitrate = std::min(increased_bitrate, troughput_based_limit);

}

time_last_bitrate_change_ = at_time;

break;

case kRcDecrease:

case kRcDecrease: {

// TODO(srte): Remove when |estimate_bounded_backoff_| has been validated.

DataRate decreased_bitrate = DataRate::PlusInfinity();

if (network_estimate_ && capacity_deviation_ratio_threshold_ &&

!estimate_bounded_backoff_) {

// Set bit rate to something slightly lower than the measured throughput

estimated_throughput = std::max(estimated_throughput,

// to get rid of any self-induced delay.

network_estimate_->link_capacity_lower);

decreased_bitrate = estimated_throughput * beta_;

}

if (decreased_bitrate > current_bitrate_ && !link_capacity_fix_) {

if (estimated_throughput > low_throughput_threshold_) {

// TODO(terelius): The link_capacity estimate may be based on old

// Set bit rate to something slightly lower than the measured throughput

// throughput measurements. Relying on them may lead to unnecessary

// to get rid of any self-induced delay.

// BWE drops.

new_bitrate = estimated_throughput * beta_;

if (new_bitrate > current_bitrate_) {

// Avoid increasing the rate when over-using.

if (link_capacity_.has_estimate()) {

new_bitrate = beta_ * link_capacity_.estimate();

}

if (estimate_bounded_backoff_ && network_estimate_) {

new_bitrate = std::max(

new_bitrate, network_estimate_->link_capacity_lower * beta_);

}

} else {

new_bitrate = estimated_throughput;

if (link_capacity_.has_estimate()) {

new_bitrate = std::max(new_bitrate, link_capacity_.estimate());

decreased_bitrate = beta_ * link_capacity_.estimate();

}

new_bitrate = std::min(new_bitrate, low_throughput_threshold_.Get());

}

new_bitrate = std::min(new_bitrate, current_bitrate_);

if (estimate_bounded_backoff_ && network_estimate_) {

decreased_bitrate = std::max(

decreased_bitrate, network_estimate_->link_capacity_lower * beta_);

}

// Avoid increasing the rate when over-using.

if (decreased_bitrate < current_bitrate_) {

new_bitrate = decreased_bitrate;

}

if (bitrate_is_initialized_ && estimated_throughput < current_bitrate_) {

constexpr double kDegradationFactor = 0.9;

if (!new_bitrate.has_value()) {

if (smoothing_experiment_ &&

last_decrease_ = DataRate::Zero();

new_bitrate < kDegradationFactor * beta_ * current_bitrate_) {

// If bitrate decreases more than a normal back off after overuse, it

// indicates a real network degradation. We do not let such a decrease

// to determine the bandwidth estimation period.

last_decrease_ = absl::nullopt;

} else {

last_decrease_ = current_bitrate_ - new_bitrate;

last_decrease_ = current_bitrate_ - *new_bitrate;

}

if (estimated_throughput < link_capacity_.LowerBound()) {

// The current throughput is far from the estimated link capacity. Clear

// the estimate to allow an immediate update in OnOveruseDetected.

link_capacity_.Reset();

}

bitrate_is_initialized_ = true;

link_capacity_.OnOveruseDetected(estimated_throughput);

// Stay on hold until the pipes are cleared.

rate_control_state_ = kRcHold;

time_last_bitrate_change_ = at_time;

time_last_bitrate_decrease_ = at_time;

break;

}

default:

MS_THROW_ERROR("unknown rate control state");

assert(false);

}

return ClampBitrate(new_bitrate, estimated_throughput);

current_bitrate_ = ClampBitrate(new_bitrate.value_or(current_bitrate_));

}

DataRate AimdRateControl::ClampBitrate(DataRate new_bitrate,

DataRate AimdRateControl::ClampBitrate(DataRate new_bitrate) const {

DataRate estimated_throughput) const {

if (estimate_bounded_increase_ && network_estimate_) {

// Allow the estimate to increase as long as alr is not detected to ensure

// that there is no BWE values that can make the estimate stuck at a too

// low bitrate. If an encoder can not produce the bitrate necessary to

// fully use the capacity, alr will sooner or later trigger.

if (!(send_side_ && no_bitrate_increase_in_alr_)) {

// Don't change the bit rate if the send side is too far off.

// We allow a bit more lag at very low rates to not too easily get stuck if

// the encoder produces uneven outputs.

const DataRate max_bitrate =

1.5 * estimated_throughput + DataRate::kbps(10);

if (new_bitrate > current_bitrate_ && new_bitrate > max_bitrate) {

new_bitrate = std::max(current_bitrate_, max_bitrate);

}

if (network_estimate_ &&

(estimate_bounded_increase_ || capacity_limit_deviation_factor_)) {

DataRate upper_bound = network_estimate_->link_capacity_upper;

new_bitrate = std::min(new_bitrate, upper_bound);

}

new_bitrate = std::max(new_bitrate, min_configured_bitrate_);

return new_bitrate;

}

DataRate AimdRateControl::MultiplicativeRateIncrease(

Timestamp at_time,

Timestamp last_time,

DataRate current_bitrate) const {

double alpha = 1.08;

if (last_time.IsFinite()) {

auto time_since_last_update = at_time - last_time;

alpha = pow(alpha, std::min(time_since_last_update.seconds<double>(), 1.0));

}

DataRate multiplicative_increase =

std::max(current_bitrate * (alpha - 1.0), DataRate::bps(1000));

std::max(current_bitrate * (alpha - 1.0), DataRate::BitsPerSec(1000));

return multiplicative_increase;

}

DataRate AimdRateControl::AdditiveRateIncrease(Timestamp at_time,

Timestamp last_time) const {

double time_period_seconds = (at_time - last_time).seconds<double>();

double data_rate_increase_bps =

GetNearMaxIncreaseRateBpsPerSecond() * time_period_seconds;

return DataRate::bps(data_rate_increase_bps);

return DataRate::BitsPerSec(data_rate_increase_bps);

}

void AimdRateControl::ChangeState(const RateControlInput& input,

Timestamp at_time) {

switch (input.bw_state) {

case BandwidthUsage::kBwNormal:

if (rate_control_state_ == kRcHold) {

time_last_bitrate_change_ = at_time;

rate_control_state_ = kRcIncrease;

}

break;

case BandwidthUsage::kBwOverusing:

if (rate_control_state_ != kRcDecrease) {

rate_control_state_ = kRcDecrease;

}

break;

case BandwidthUsage::kBwUnderusing:

rate_control_state_ = kRcHold;

break;

default:

MS_THROW_ERROR("unknown input.bw_state");

assert(false);

}

} // namespace webrtc

保存された差分

原文

ファイルを開く

/*
 *  Copyright (c) 2014 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.
 */

#define MS_CLASS "webrtc::AimdRateControl"
// #define MS_LOG_DEV_LEVEL 3

#include "modules/remote_bitrate_estimator/aimd_rate_control.h"
#include "api/transport/network_types.h"
#include "api/units/data_rate.h"
#include "modules/remote_bitrate_estimator/include/bwe_defines.h"
#include "modules/remote_bitrate_estimator/overuse_detector.h"
#include "rtc_base/experiments/field_trial_parser.h"
#include "rtc_base/numerics/safe_minmax.h"

#include "Logger.hpp"
#include "MediaSoupErrors.hpp"

#include <inttypes.h>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <string>

namespace webrtc {
namespace {

constexpr TimeDelta kDefaultRtt = TimeDelta::Millis<200>();
constexpr double kDefaultBackoffFactor = 0.85;

constexpr char kBweBackOffFactorExperiment[] = "WebRTC-BweBackOffFactor";

bool IsEnabled(const WebRtcKeyValueConfig& field_trials,
               absl::string_view key) {
  return field_trials.Lookup(key).find("Enabled") == 0;
}

double ReadBackoffFactor(const WebRtcKeyValueConfig& key_value_config) {
  std::string experiment_string =
      key_value_config.Lookup(kBweBackOffFactorExperiment);
  double backoff_factor;
  int parsed_values =
      sscanf(experiment_string.c_str(), "Enabled-%lf", &backoff_factor);
  if (parsed_values == 1) {
    if (backoff_factor >= 1.0) {
      MS_WARN_TAG(bwe, "Back-off factor must be less than 1.");
    } else if (backoff_factor <= 0.0) {
      MS_WARN_TAG(bwe, "Back-off factor must be greater than 0.");
    } else {
      return backoff_factor;
    }
  }

MS_WARN_TAG(bwe, "Failed to parse parameters for AimdRateControl experiment from field trial string. Using default.");

return kDefaultBackoffFactor;
}

}  // namespace

AimdRateControl::AimdRateControl(const WebRtcKeyValueConfig* key_value_config)
    : AimdRateControl(key_value_config, /* send_side =*/false) {}

AimdRateControl::AimdRateControl(const WebRtcKeyValueConfig* key_value_config,
                                 bool send_side)
    : min_configured_bitrate_(congestion_controller::GetMinBitrate()),
      max_configured_bitrate_(DataRate::kbps(30000)),
      current_bitrate_(max_configured_bitrate_),
      latest_estimated_throughput_(current_bitrate_),
      link_capacity_(),
      rate_control_state_(kRcHold),
      time_last_bitrate_change_(Timestamp::MinusInfinity()),
      time_last_bitrate_decrease_(Timestamp::MinusInfinity()),
      time_first_throughput_estimate_(Timestamp::MinusInfinity()),
      bitrate_is_initialized_(false),
      beta_(IsEnabled(*key_value_config, kBweBackOffFactorExperiment)
                ? ReadBackoffFactor(*key_value_config)
                : kDefaultBackoffFactor),
      in_alr_(false),
      rtt_(kDefaultRtt),
      send_side_(send_side),
      in_experiment_(!AdaptiveThresholdExperimentIsDisabled(*key_value_config)),
      no_bitrate_increase_in_alr_(
          IsEnabled(*key_value_config,
                    "WebRTC-DontIncreaseDelayBasedBweInAlr")),
      smoothing_experiment_(false),
      estimate_bounded_backoff_(
          IsEnabled(*key_value_config, "WebRTC-Bwe-EstimateBoundedBackoff")),
      estimate_bounded_increase_(
          IsEnabled(*key_value_config, "WebRTC-Bwe-EstimateBoundedIncrease")),
      initial_backoff_interval_("initial_backoff_interval"),
      low_throughput_threshold_("low_throughput", DataRate::Zero()),
      capacity_deviation_ratio_threshold_("cap_thr", 0.2),
      capacity_limit_deviation_factor_("cap_lim", 1) {
  // E.g
  // WebRTC-BweAimdRateControlConfig/initial_backoff_interval:100ms,
  // low_throughput:50kbps/
  ParseFieldTrial({&initial_backoff_interval_, &low_throughput_threshold_},
                  key_value_config->Lookup("WebRTC-BweAimdRateControlConfig"));
  if (initial_backoff_interval_) {
    MS_DEBUG_TAG(bwe, "Using aimd rate control with initial back-off interval: %s",
                     ToString(*initial_backoff_interval_).c_str());
  }
  MS_DEBUG_TAG(bwe, "Using aimd rate control with back off factor: %f ", beta_);
  ParseFieldTrial(
      {&capacity_deviation_ratio_threshold_, &capacity_limit_deviation_factor_},
      key_value_config->Lookup("WebRTC-Bwe-AimdRateControl-NetworkState"));
}

AimdRateControl::~AimdRateControl() {}

void AimdRateControl::SetStartBitrate(DataRate start_bitrate) {
  current_bitrate_ = start_bitrate;
  latest_estimated_throughput_ = current_bitrate_;
  bitrate_is_initialized_ = true;
}

void AimdRateControl::SetMinBitrate(DataRate min_bitrate) {
  MS_DEBUG_DEV("[min_bitrate:%" PRIi64 "]", min_bitrate.bps());

min_configured_bitrate_ = min_bitrate;
  current_bitrate_ = std::max(min_bitrate, current_bitrate_);
}

bool AimdRateControl::ValidEstimate() const {
  return bitrate_is_initialized_;
}

TimeDelta AimdRateControl::GetFeedbackInterval() const {
  // Estimate how often we can send RTCP if we allocate up to 5% of bandwidth
  // to feedback.
  const DataSize kRtcpSize = DataSize::bytes(80);
  const DataRate rtcp_bitrate = current_bitrate_ * 0.05;
  const TimeDelta interval = kRtcpSize / rtcp_bitrate;
  const TimeDelta kMinFeedbackInterval = TimeDelta::ms(200);
  const TimeDelta kMaxFeedbackInterval = TimeDelta::ms(1000);
  return interval.Clamped(kMinFeedbackInterval, kMaxFeedbackInterval);
}

bool AimdRateControl::TimeToReduceFurther(Timestamp at_time,
                                          DataRate estimated_throughput) const {
  const TimeDelta bitrate_reduction_interval =
      rtt_.Clamped(TimeDelta::ms(10), TimeDelta::ms(200));
  if (at_time - time_last_bitrate_change_ >= bitrate_reduction_interval) {
    return true;
  }
  if (ValidEstimate()) {
    // TODO(terelius/holmer): Investigate consequences of increasing
    // the threshold to 0.95 * LatestEstimate().
    const DataRate threshold = 0.5 * LatestEstimate();
    return estimated_throughput < threshold;
  }
  return false;
}

bool AimdRateControl::InitialTimeToReduceFurther(Timestamp at_time) const {
  if (!initial_backoff_interval_) {
    return ValidEstimate() &&
           TimeToReduceFurther(at_time,
                               LatestEstimate() / 2 - DataRate::bps(1));
  }
  // TODO(terelius): We could use the RTT (clamped to suitable limits) instead
  // of a fixed bitrate_reduction_interval.
  if (time_last_bitrate_decrease_.IsInfinite() ||
      at_time - time_last_bitrate_decrease_ >= *initial_backoff_interval_) {
    return true;
  }
  return false;
}

DataRate AimdRateControl::LatestEstimate() const {
  return current_bitrate_;
}

void AimdRateControl::SetRtt(TimeDelta rtt) {
  rtt_ = rtt;
}

DataRate AimdRateControl::Update(const RateControlInput* input,
                                 Timestamp at_time) {
  // RTC_CHECK(input);

// Set the initial bit rate value to what we're receiving the first half
  // second.
  // TODO(bugs.webrtc.org/9379): The comment above doesn't match to the code.
  if (!bitrate_is_initialized_) {
    const TimeDelta kInitializationTime = TimeDelta::seconds(5);
    // RTC_DCHECK_LE(kBitrateWindowMs, kInitializationTime.ms());
    if (time_first_throughput_estimate_.IsInfinite()) {
      if (input->estimated_throughput)
        time_first_throughput_estimate_ = at_time;
    } else if (at_time - time_first_throughput_estimate_ >
                   kInitializationTime &&
               input->estimated_throughput) {
      current_bitrate_ = *input->estimated_throughput;
      bitrate_is_initialized_ = true;
    }
  }

current_bitrate_ = ChangeBitrate(current_bitrate_, *input, at_time);
  return current_bitrate_;
}

void AimdRateControl::SetInApplicationLimitedRegion(bool in_alr) {
  in_alr_ = in_alr;
}

void AimdRateControl::SetEstimate(DataRate bitrate, Timestamp at_time) {
  bitrate_is_initialized_ = true;
  DataRate prev_bitrate = current_bitrate_;
  current_bitrate_ = ClampBitrate(bitrate, bitrate);
  time_last_bitrate_change_ = at_time;
  if (current_bitrate_ < prev_bitrate) {
    time_last_bitrate_decrease_ = at_time;
  }
}

void AimdRateControl::SetNetworkStateEstimate(
    const absl::optional<NetworkStateEstimate>& estimate) {
  network_estimate_ = estimate;
}

double AimdRateControl::GetNearMaxIncreaseRateBpsPerSecond() const {
  // RTC_DCHECK(!current_bitrate_.IsZero());
  const TimeDelta kFrameInterval = TimeDelta::seconds(1) / 30;
  DataSize frame_size = current_bitrate_ * kFrameInterval;
  const DataSize kPacketSize = DataSize::bytes(1200);
  double packets_per_frame = std::ceil(frame_size / kPacketSize);
  DataSize avg_packet_size = frame_size / packets_per_frame;

// Approximate the over-use estimator delay to 100 ms.
  TimeDelta response_time = rtt_ + TimeDelta::ms(100);
  if (in_experiment_)
    response_time = response_time * 2;
  double increase_rate_bps_per_second =
      (avg_packet_size / response_time).bps<double>();
  double kMinIncreaseRateBpsPerSecond = 4000;
  return std::max(kMinIncreaseRateBpsPerSecond, increase_rate_bps_per_second);
}

TimeDelta AimdRateControl::GetExpectedBandwidthPeriod() const {
  const TimeDelta kMinPeriod =
      smoothing_experiment_ ? TimeDelta::ms(500) : TimeDelta::seconds(2);
  const TimeDelta kDefaultPeriod = TimeDelta::seconds(3);
  const TimeDelta kMaxPeriod = TimeDelta::seconds(50);

double increase_rate_bps_per_second = GetNearMaxIncreaseRateBpsPerSecond();
  if (!last_decrease_)
    return smoothing_experiment_ ? kMinPeriod : kDefaultPeriod;
  double time_to_recover_decrease_seconds =
      last_decrease_->bps() / increase_rate_bps_per_second;
  TimeDelta period = TimeDelta::seconds(time_to_recover_decrease_seconds);
  return period.Clamped(kMinPeriod, kMaxPeriod);
}

DataRate AimdRateControl::ChangeBitrate(DataRate new_bitrate,
                                        const RateControlInput& input,
                                        Timestamp at_time) {
  DataRate estimated_throughput =
      input.estimated_throughput.value_or(latest_estimated_throughput_);
  if (input.estimated_throughput)
    latest_estimated_throughput_ = *input.estimated_throughput;

// An over-use should always trigger us to reduce the bitrate, even though
  // we have not yet established our first estimate. By acting on the over-use,
  // we will end up with a valid estimate.
  if (!bitrate_is_initialized_ &&
      input.bw_state != BandwidthUsage::kBwOverusing)
    return current_bitrate_;

ChangeState(input, at_time);

switch (rate_control_state_) {
    case kRcHold:
      break;

case kRcIncrease:
      if (estimated_throughput > link_capacity_.UpperBound())
        link_capacity_.Reset();

// Do not increase the delay based estimate in alr since the estimator
      // will not be able to get transport feedback necessary to detect if
      // the new estimate is correct.
      if (!(send_side_ && in_alr_ && no_bitrate_increase_in_alr_)) {
        if (link_capacity_.has_estimate()) {
          // The link_capacity estimate is reset if the measured throughput
          // is too far from the estimate. We can therefore assume that our
          // target rate is reasonably close to link capacity and use additive
          // increase.
          DataRate additive_increase =
              AdditiveRateIncrease(at_time, time_last_bitrate_change_);
          new_bitrate += additive_increase;
        } else {
          // If we don't have an estimate of the link capacity, use faster ramp
          // up to discover the capacity.
          DataRate multiplicative_increase = MultiplicativeRateIncrease(
              at_time, time_last_bitrate_change_, new_bitrate);
          new_bitrate += multiplicative_increase;
        }
      }

time_last_bitrate_change_ = at_time;
      break;

case kRcDecrease:
      // TODO(srte): Remove when |estimate_bounded_backoff_| has been validated.
      if (network_estimate_ && capacity_deviation_ratio_threshold_ &&
          !estimate_bounded_backoff_) {
        estimated_throughput = std::max(estimated_throughput,
                                        network_estimate_->link_capacity_lower);
      }
      if (estimated_throughput > low_throughput_threshold_) {
        // Set bit rate to something slightly lower than the measured throughput
        // to get rid of any self-induced delay.
        new_bitrate = estimated_throughput * beta_;
        if (new_bitrate > current_bitrate_) {
          // Avoid increasing the rate when over-using.
          if (link_capacity_.has_estimate()) {
            new_bitrate = beta_ * link_capacity_.estimate();
          }
        }
        if (estimate_bounded_backoff_ && network_estimate_) {
          new_bitrate = std::max(
              new_bitrate, network_estimate_->link_capacity_lower * beta_);
        }
      } else {
        new_bitrate = estimated_throughput;
        if (link_capacity_.has_estimate()) {
          new_bitrate = std::max(new_bitrate, link_capacity_.estimate());
        }
        new_bitrate = std::min(new_bitrate, low_throughput_threshold_.Get());
      }
      new_bitrate = std::min(new_bitrate, current_bitrate_);

if (bitrate_is_initialized_ && estimated_throughput < current_bitrate_) {
        constexpr double kDegradationFactor = 0.9;
        if (smoothing_experiment_ &&
            new_bitrate < kDegradationFactor * beta_ * current_bitrate_) {
          // If bitrate decreases more than a normal back off after overuse, it
          // indicates a real network degradation. We do not let such a decrease
          // to determine the bandwidth estimation period.
          last_decrease_ = absl::nullopt;
        } else {
          last_decrease_ = current_bitrate_ - new_bitrate;
        }
      }
      if (estimated_throughput < link_capacity_.LowerBound()) {
        // The current throughput is far from the estimated link capacity. Clear
        // the estimate to allow an immediate update in OnOveruseDetected.
        link_capacity_.Reset();
      }

bitrate_is_initialized_ = true;
      link_capacity_.OnOveruseDetected(estimated_throughput);
      // Stay on hold until the pipes are cleared.
      rate_control_state_ = kRcHold;
      time_last_bitrate_change_ = at_time;
      time_last_bitrate_decrease_ = at_time;
      break;

default:
      MS_THROW_ERROR("unknown rate control state");
  }
  return ClampBitrate(new_bitrate, estimated_throughput);
}

DataRate AimdRateControl::ClampBitrate(DataRate new_bitrate,
                                       DataRate estimated_throughput) const {
  // Allow the estimate to increase as long as alr is not detected to ensure
  // that there is no BWE values that can make the estimate stuck at a too
  // low bitrate. If an encoder can not produce the bitrate necessary to
  // fully use the capacity, alr will sooner or later trigger.
  if (!(send_side_ && no_bitrate_increase_in_alr_)) {
    // Don't change the bit rate if the send side is too far off.
    // We allow a bit more lag at very low rates to not too easily get stuck if
    // the encoder produces uneven outputs.
    const DataRate max_bitrate =
        1.5 * estimated_throughput + DataRate::kbps(10);
    if (new_bitrate > current_bitrate_ && new_bitrate > max_bitrate) {
      new_bitrate = std::max(current_bitrate_, max_bitrate);
    }
  }

if (network_estimate_ &&
      (estimate_bounded_increase_ || capacity_limit_deviation_factor_)) {
    DataRate upper_bound = network_estimate_->link_capacity_upper;
    new_bitrate = std::min(new_bitrate, upper_bound);
  }
  new_bitrate = std::max(new_bitrate, min_configured_bitrate_);
  return new_bitrate;
}

DataRate AimdRateControl::MultiplicativeRateIncrease(
    Timestamp at_time,
    Timestamp last_time,
    DataRate current_bitrate) const {
  double alpha = 1.08;
  if (last_time.IsFinite()) {
    auto time_since_last_update = at_time - last_time;
    alpha = pow(alpha, std::min(time_since_last_update.seconds<double>(), 1.0));
  }
  DataRate multiplicative_increase =
      std::max(current_bitrate * (alpha - 1.0), DataRate::bps(1000));
  return multiplicative_increase;
}

DataRate AimdRateControl::AdditiveRateIncrease(Timestamp at_time,
                                               Timestamp last_time) const {
  double time_period_seconds = (at_time - last_time).seconds<double>();
  double data_rate_increase_bps =
      GetNearMaxIncreaseRateBpsPerSecond() * time_period_seconds;
  return DataRate::bps(data_rate_increase_bps);
}

void AimdRateControl::ChangeState(const RateControlInput& input,
                                  Timestamp at_time) {
  switch (input.bw_state) {
    case BandwidthUsage::kBwNormal:
      if (rate_control_state_ == kRcHold) {
        time_last_bitrate_change_ = at_time;
        rate_control_state_ = kRcIncrease;
      }
      break;
    case BandwidthUsage::kBwOverusing:
      if (rate_control_state_ != kRcDecrease) {
        rate_control_state_ = kRcDecrease;
      }
      break;
    case BandwidthUsage::kBwUnderusing:
      rate_control_state_ = kRcHold;
      break;
    default:
      MS_THROW_ERROR("unknown input.bw_state");
  }
}

}  // namespace webrtc

変更されたテキスト

ファイルを開く

#include "modules/remote_bitrate_estimator/aimd_rate_control.h"

#include <inttypes.h>

#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <string>

#include "absl/strings/match.h"
#include "api/transport/network_types.h"
#include "api/units/data_rate.h"
#include "modules/remote_bitrate_estimator/include/bwe_defines.h"
#include "modules/remote_bitrate_estimator/overuse_detector.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"

namespace webrtc {
namespace {

constexpr TimeDelta kDefaultRtt = TimeDelta::Millis(200);
constexpr double kDefaultBackoffFactor = 0.85;

constexpr char kBweBackOffFactorExperiment[] = "WebRTC-BweBackOffFactor";

bool IsEnabled(const WebRtcKeyValueConfig& field_trials,
               absl::string_view key) {
  return absl::StartsWith(field_trials.Lookup(key), "Enabled");
}

bool IsNotDisabled(const WebRtcKeyValueConfig& field_trials,
                   absl::string_view key) {
  return !absl::StartsWith(field_trials.Lookup(key), "Disabled");
}

double ReadBackoffFactor(const WebRtcKeyValueConfig& key_value_config) {
  std::string experiment_string =
      key_value_config.Lookup(kBweBackOffFactorExperiment);
  double backoff_factor;
  int parsed_values =
      sscanf(experiment_string.c_str(), "Enabled-%lf", &backoff_factor);
  if (parsed_values == 1) {
    if (backoff_factor >= 1.0) {
      RTC_LOG(WARNING) << "Back-off factor must be less than 1.";
    } else if (backoff_factor <= 0.0) {
      RTC_LOG(WARNING) << "Back-off factor must be greater than 0.";
    } else {
      return backoff_factor;
    }
  }
  RTC_LOG(LS_WARNING) << "Failed to parse parameters for AimdRateControl "
                         "experiment from field trial string. Using default.";
  return kDefaultBackoffFactor;
}

}  // namespace

AimdRateControl::AimdRateControl(const WebRtcKeyValueConfig* key_value_config)
    : AimdRateControl(key_value_config, /* send_side =*/false) {}

AimdRateControl::AimdRateControl(const WebRtcKeyValueConfig* key_value_config,
                                 bool send_side)
    : min_configured_bitrate_(congestion_controller::GetMinBitrate()),
      max_configured_bitrate_(DataRate::KilobitsPerSec(30000)),
      current_bitrate_(max_configured_bitrate_),
      latest_estimated_throughput_(current_bitrate_),
      link_capacity_(),
      rate_control_state_(kRcHold),
      time_last_bitrate_change_(Timestamp::MinusInfinity()),
      time_last_bitrate_decrease_(Timestamp::MinusInfinity()),
      time_first_throughput_estimate_(Timestamp::MinusInfinity()),
      bitrate_is_initialized_(false),
      beta_(IsEnabled(*key_value_config, kBweBackOffFactorExperiment)
                ? ReadBackoffFactor(*key_value_config)
                : kDefaultBackoffFactor),
      in_alr_(false),
      rtt_(kDefaultRtt),
      send_side_(send_side),
      in_experiment_(!AdaptiveThresholdExperimentIsDisabled(*key_value_config)),
      no_bitrate_increase_in_alr_(
          IsEnabled(*key_value_config,
                    "WebRTC-DontIncreaseDelayBasedBweInAlr")),
      estimate_bounded_backoff_(
          IsNotDisabled(*key_value_config,
                        "WebRTC-Bwe-EstimateBoundedBackoff")),
      estimate_bounded_increase_(
          IsNotDisabled(*key_value_config,
                        "WebRTC-Bwe-EstimateBoundedIncrease")),
      initial_backoff_interval_("initial_backoff_interval"),
      link_capacity_fix_("link_capacity_fix") {
  // E.g
  // WebRTC-BweAimdRateControlConfig/initial_backoff_interval:100ms/
  ParseFieldTrial({&initial_backoff_interval_, &link_capacity_fix_},
                  key_value_config->Lookup("WebRTC-BweAimdRateControlConfig"));
  if (initial_backoff_interval_) {
    RTC_LOG(LS_INFO) << "Using aimd rate control with initial back-off interval"
                        " "
                     << ToString(*initial_backoff_interval_) << ".";
  }
  RTC_LOG(LS_INFO) << "Using aimd rate control with back off factor " << beta_;
}

AimdRateControl::~AimdRateControl() {}

void AimdRateControl::SetStartBitrate(DataRate start_bitrate) {
  current_bitrate_ = start_bitrate;
  latest_estimated_throughput_ = current_bitrate_;
  bitrate_is_initialized_ = true;
}

void AimdRateControl::SetMinBitrate(DataRate min_bitrate) {
  min_configured_bitrate_ = min_bitrate;
  current_bitrate_ = std::max(min_bitrate, current_bitrate_);
}

bool AimdRateControl::ValidEstimate() const {
  return bitrate_is_initialized_;
}

TimeDelta AimdRateControl::GetFeedbackInterval() const {
  // Estimate how often we can send RTCP if we allocate up to 5% of bandwidth
  // to feedback.
  const DataSize kRtcpSize = DataSize::Bytes(80);
  const DataRate rtcp_bitrate = current_bitrate_ * 0.05;
  const TimeDelta interval = kRtcpSize / rtcp_bitrate;
  const TimeDelta kMinFeedbackInterval = TimeDelta::Millis(200);
  const TimeDelta kMaxFeedbackInterval = TimeDelta::Millis(1000);
  return interval.Clamped(kMinFeedbackInterval, kMaxFeedbackInterval);
}

bool AimdRateControl::TimeToReduceFurther(Timestamp at_time,
                                          DataRate estimated_throughput) const {
  const TimeDelta bitrate_reduction_interval =
      rtt_.Clamped(TimeDelta::Millis(10), TimeDelta::Millis(200));
  if (at_time - time_last_bitrate_change_ >= bitrate_reduction_interval) {
    return true;
  }
  if (ValidEstimate()) {
    // TODO(terelius/holmer): Investigate consequences of increasing
    // the threshold to 0.95 * LatestEstimate().
    const DataRate threshold = 0.5 * LatestEstimate();
    return estimated_throughput < threshold;
  }
  return false;
}

bool AimdRateControl::InitialTimeToReduceFurther(Timestamp at_time) const {
  if (!initial_backoff_interval_) {
    return ValidEstimate() &&
           TimeToReduceFurther(at_time,
                               LatestEstimate() / 2 - DataRate::BitsPerSec(1));
  }
  // TODO(terelius): We could use the RTT (clamped to suitable limits) instead
  // of a fixed bitrate_reduction_interval.
  if (time_last_bitrate_decrease_.IsInfinite() ||
      at_time - time_last_bitrate_decrease_ >= *initial_backoff_interval_) {
    return true;
  }
  return false;
}

DataRate AimdRateControl::LatestEstimate() const {
  return current_bitrate_;
}

void AimdRateControl::SetRtt(TimeDelta rtt) {
  rtt_ = rtt;
}

DataRate AimdRateControl::Update(const RateControlInput* input,
                                 Timestamp at_time) {
  RTC_CHECK(input);

// Set the initial bit rate value to what we're receiving the first half
  // second.
  // TODO(bugs.webrtc.org/9379): The comment above doesn't match to the code.
  if (!bitrate_is_initialized_) {
    const TimeDelta kInitializationTime = TimeDelta::Seconds(5);
    RTC_DCHECK_LE(kBitrateWindowMs, kInitializationTime.ms());
    if (time_first_throughput_estimate_.IsInfinite()) {
      if (input->estimated_throughput)
        time_first_throughput_estimate_ = at_time;
    } else if (at_time - time_first_throughput_estimate_ >
                   kInitializationTime &&
               input->estimated_throughput) {
      current_bitrate_ = *input->estimated_throughput;
      bitrate_is_initialized_ = true;
    }
  }

ChangeBitrate(*input, at_time);
  return current_bitrate_;
}

void AimdRateControl::SetInApplicationLimitedRegion(bool in_alr) {
  in_alr_ = in_alr;
}

void AimdRateControl::SetEstimate(DataRate bitrate, Timestamp at_time) {
  bitrate_is_initialized_ = true;
  DataRate prev_bitrate = current_bitrate_;
  current_bitrate_ = ClampBitrate(bitrate);
  time_last_bitrate_change_ = at_time;
  if (current_bitrate_ < prev_bitrate) {
    time_last_bitrate_decrease_ = at_time;
  }
}

void AimdRateControl::SetNetworkStateEstimate(
    const absl::optional<NetworkStateEstimate>& estimate) {
  network_estimate_ = estimate;
}

double AimdRateControl::GetNearMaxIncreaseRateBpsPerSecond() const {
  RTC_DCHECK(!current_bitrate_.IsZero());
  const TimeDelta kFrameInterval = TimeDelta::Seconds(1) / 30;
  DataSize frame_size = current_bitrate_ * kFrameInterval;
  const DataSize kPacketSize = DataSize::Bytes(1200);
  double packets_per_frame = std::ceil(frame_size / kPacketSize);
  DataSize avg_packet_size = frame_size / packets_per_frame;

// Approximate the over-use estimator delay to 100 ms.
  TimeDelta response_time = rtt_ + TimeDelta::Millis(100);
  if (in_experiment_)
    response_time = response_time * 2;
  double increase_rate_bps_per_second =
      (avg_packet_size / response_time).bps<double>();
  double kMinIncreaseRateBpsPerSecond = 4000;
  return std::max(kMinIncreaseRateBpsPerSecond, increase_rate_bps_per_second);
}

TimeDelta AimdRateControl::GetExpectedBandwidthPeriod() const {
  const TimeDelta kMinPeriod = TimeDelta::Seconds(2);
  const TimeDelta kDefaultPeriod = TimeDelta::Seconds(3);
  const TimeDelta kMaxPeriod = TimeDelta::Seconds(50);

double increase_rate_bps_per_second = GetNearMaxIncreaseRateBpsPerSecond();
  if (!last_decrease_)
    return kDefaultPeriod;
  double time_to_recover_decrease_seconds =
      last_decrease_->bps() / increase_rate_bps_per_second;
  TimeDelta period = TimeDelta::Seconds(time_to_recover_decrease_seconds);
  return period.Clamped(kMinPeriod, kMaxPeriod);
}

void AimdRateControl::ChangeBitrate(const RateControlInput& input,
                                    Timestamp at_time) {
  absl::optional<DataRate> new_bitrate;
  DataRate estimated_throughput =
      input.estimated_throughput.value_or(latest_estimated_throughput_);
  if (input.estimated_throughput)
    latest_estimated_throughput_ = *input.estimated_throughput;

ChangeState(input, at_time);

// We limit the new bitrate based on the troughput to avoid unlimited bitrate
  // increases. We allow a bit more lag at very low rates to not too easily get
  // stuck if the encoder produces uneven outputs.
  const DataRate troughput_based_limit =
      1.5 * estimated_throughput + DataRate::KilobitsPerSec(10);

switch (rate_control_state_) {
    case kRcHold:
      break;

case kRcIncrease:
      if (estimated_throughput > link_capacity_.UpperBound())
        link_capacity_.Reset();

// Do not increase the delay based estimate in alr since the estimator
      // will not be able to get transport feedback necessary to detect if
      // the new estimate is correct.
      // If we have previously increased above the limit (for instance due to
      // probing), we don't allow further changes.
      if (current_bitrate_ < troughput_based_limit &&
          !(send_side_ && in_alr_ && no_bitrate_increase_in_alr_)) {
        DataRate increased_bitrate = DataRate::MinusInfinity();
        if (link_capacity_.has_estimate()) {
          // The link_capacity estimate is reset if the measured throughput
          // is too far from the estimate. We can therefore assume that our
          // target rate is reasonably close to link capacity and use additive
          // increase.
          DataRate additive_increase =
              AdditiveRateIncrease(at_time, time_last_bitrate_change_);
          increased_bitrate = current_bitrate_ + additive_increase;
        } else {
          // If we don't have an estimate of the link capacity, use faster ramp
          // up to discover the capacity.
          DataRate multiplicative_increase = MultiplicativeRateIncrease(
              at_time, time_last_bitrate_change_, current_bitrate_);
          increased_bitrate = current_bitrate_ + multiplicative_increase;
        }
        new_bitrate = std::min(increased_bitrate, troughput_based_limit);
      }

time_last_bitrate_change_ = at_time;
      break;

case kRcDecrease: {
      DataRate decreased_bitrate = DataRate::PlusInfinity();

// Set bit rate to something slightly lower than the measured throughput
      // to get rid of any self-induced delay.
      decreased_bitrate = estimated_throughput * beta_;
      if (decreased_bitrate > current_bitrate_ && !link_capacity_fix_) {
        // TODO(terelius): The link_capacity estimate may be based on old
        // throughput measurements. Relying on them may lead to unnecessary
        // BWE drops.
        if (link_capacity_.has_estimate()) {
          decreased_bitrate = beta_ * link_capacity_.estimate();
        }
      }
      if (estimate_bounded_backoff_ && network_estimate_) {
        decreased_bitrate = std::max(
            decreased_bitrate, network_estimate_->link_capacity_lower * beta_);
      }

// Avoid increasing the rate when over-using.
      if (decreased_bitrate < current_bitrate_) {
        new_bitrate = decreased_bitrate;
      }

if (bitrate_is_initialized_ && estimated_throughput < current_bitrate_) {
        if (!new_bitrate.has_value()) {
          last_decrease_ = DataRate::Zero();
        } else {
          last_decrease_ = current_bitrate_ - *new_bitrate;
        }
      }
      if (estimated_throughput < link_capacity_.LowerBound()) {
        // The current throughput is far from the estimated link capacity. Clear
        // the estimate to allow an immediate update in OnOveruseDetected.
        link_capacity_.Reset();
      }

current_bitrate_ = ClampBitrate(new_bitrate.value_or(current_bitrate_));
}

DataRate AimdRateControl::ClampBitrate(DataRate new_bitrate) const {
  if (estimate_bounded_increase_ && network_estimate_) {
    DataRate upper_bound = network_estimate_->link_capacity_upper;
    new_bitrate = std::min(new_bitrate, upper_bound);
  }
  new_bitrate = std::max(new_bitrate, min_configured_bitrate_);
  return new_bitrate;
}

}  // namespace webrtc