rtc_base/experiments/rate_control_settings.cc

/*
 *  Copyright (c) 2019 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 "rtc_base/experiments/rate_control_settings.h"

#include <inttypes.h>
#include <stdio.h>

#include <string>

#include "api/transport/field_trial_based_config.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_conversions.h"

namespace webrtc {

namespace {

const char* kCongestionWindowFieldTrialName = "WebRTC-CwndExperiment";
const int kDefaultAcceptedQueueMs = 250;

const char* kCongestionWindowPushbackFieldTrialName =
    "WebRTC-CongestionWindowPushback";
const int kDefaultMinPushbackTargetBitrateBps = 30000;

absl::optional<int> MaybeReadCwndExperimentParameter(
    const WebRtcKeyValueConfig* const key_value_config) {
  int64_t accepted_queue_ms;
  std::string experiment_string =
      key_value_config->Lookup(kCongestionWindowFieldTrialName);
  int parsed_values =
      sscanf(experiment_string.c_str(), "Enabled-%" PRId64, &accepted_queue_ms);
  if (parsed_values == 1) {
    RTC_CHECK_GE(accepted_queue_ms, 0)
        << "Accepted must be greater than or equal to 0.";
    return rtc::checked_cast<int>(accepted_queue_ms);
  } else if (experiment_string.find("Enabled") == 0) {
    return kDefaultAcceptedQueueMs;
  }
  return absl::nullopt;
}

absl::optional<int> MaybeReadCongestionWindowPushbackExperimentParameter(
    const WebRtcKeyValueConfig* const key_value_config) {
  uint32_t min_pushback_target_bitrate_bps;
  std::string experiment_string =
      key_value_config->Lookup(kCongestionWindowPushbackFieldTrialName);
  int parsed_values = sscanf(experiment_string.c_str(), "Enabled-%" PRIu32,
                             &min_pushback_target_bitrate_bps);
  if (parsed_values == 1) {
    RTC_CHECK_GE(min_pushback_target_bitrate_bps, 0)
        << "Min pushback target bitrate must be greater than or equal to 0.";
    return rtc::checked_cast<int>(min_pushback_target_bitrate_bps);
  } else if (experiment_string.find("Enabled") == 0) {
    return kDefaultMinPushbackTargetBitrateBps;
  }
  return absl::nullopt;
}

}  // namespace

RateControlSettings::RateControlSettings(
    const WebRtcKeyValueConfig* const key_value_config)
    : congestion_window_("cwnd",
                         MaybeReadCwndExperimentParameter(key_value_config)),
      congestion_window_pushback_(
          "cwnd_pushback",
          MaybeReadCongestionWindowPushbackExperimentParameter(
              key_value_config)) {
  ParseFieldTrial({&congestion_window_, &congestion_window_pushback_},
                  key_value_config->Lookup("WebRTC-VideoRateControl"));
}

RateControlSettings::~RateControlSettings() = default;
RateControlSettings::RateControlSettings(RateControlSettings&&) = default;

RateControlSettings RateControlSettings::ParseFromFieldTrials() {
  FieldTrialBasedConfig field_trial_config;
  return RateControlSettings(&field_trial_config);
}

RateControlSettings RateControlSettings::ParseFromKeyValueConfig(
    const WebRtcKeyValueConfig* const key_value_config) {
  FieldTrialBasedConfig field_trial_config;
  return RateControlSettings(key_value_config ? key_value_config
                                              : &field_trial_config);
}

bool RateControlSettings::UseCongestionWindow() const {
  return congestion_window_;
}

int64_t RateControlSettings::GetCongestionWindowAdditionalTimeMs() const {
  return congestion_window_.GetOptional().value_or(kDefaultAcceptedQueueMs);
}

bool RateControlSettings::UseCongestionWindowPushback() const {
  return congestion_window_ && congestion_window_pushback_;
}

uint32_t RateControlSettings::CongestionWindowMinPushbackTargetBitrateBps()
    const {
  return congestion_window_pushback_.GetOptional().value_or(
      kDefaultMinPushbackTargetBitrateBps);
}

}  // namespace webrtc