| /* |
| * Copyright (c) 2017 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/congestion_controller/goog_cc/bitrate_estimator.h" |
| |
| #include <stdio.h> |
| #include <algorithm> |
| #include <cmath> |
| #include <string> |
| |
| #include "api/units/data_rate.h" |
| #include "modules/remote_bitrate_estimator/test/bwe_test_logging.h" |
| #include "rtc_base/logging.h" |
| |
| namespace webrtc { |
| |
| namespace { |
| constexpr int kInitialRateWindowMs = 500; |
| constexpr int kRateWindowMs = 150; |
| constexpr int kMinRateWindowMs = 150; |
| constexpr int kMaxRateWindowMs = 1000; |
| |
| const char kBweThroughputWindowConfig[] = "WebRTC-BweThroughputWindowConfig"; |
| |
| } // namespace |
| |
| BitrateEstimator::BitrateEstimator(const WebRtcKeyValueConfig* key_value_config) |
| : sum_(0), |
| initial_window_ms_("initial_window_ms", |
| kInitialRateWindowMs, |
| kMinRateWindowMs, |
| kMaxRateWindowMs), |
| noninitial_window_ms_("window_ms", |
| kRateWindowMs, |
| kMinRateWindowMs, |
| kMaxRateWindowMs), |
| uncertainty_scale_("scale", 10.0), |
| uncertainty_scale_in_alr_("scale_alr", 10.0), |
| uncertainty_symmetry_cap_("symmetry_cap", DataRate::Zero()), |
| estimate_floor_("floor", DataRate::Zero()), |
| current_window_ms_(0), |
| prev_time_ms_(-1), |
| bitrate_estimate_kbps_(-1.0f), |
| bitrate_estimate_var_(50.0f) { |
| // E.g WebRTC-BweThroughputWindowConfig/initial_window_ms:350,window_ms:250/ |
| ParseFieldTrial({&initial_window_ms_, &noninitial_window_ms_, |
| &uncertainty_scale_, &uncertainty_scale_in_alr_, |
| &uncertainty_symmetry_cap_, &estimate_floor_}, |
| key_value_config->Lookup(kBweThroughputWindowConfig)); |
| } |
| |
| BitrateEstimator::~BitrateEstimator() = default; |
| |
| void BitrateEstimator::Update(Timestamp at_time, DataSize amount, bool in_alr) { |
| int rate_window_ms = noninitial_window_ms_.Get(); |
| // We use a larger window at the beginning to get a more stable sample that |
| // we can use to initialize the estimate. |
| if (bitrate_estimate_kbps_ < 0.f) |
| rate_window_ms = initial_window_ms_.Get(); |
| float bitrate_sample_kbps = |
| UpdateWindow(at_time.ms(), amount.bytes(), rate_window_ms); |
| if (bitrate_sample_kbps < 0.0f) |
| return; |
| if (bitrate_estimate_kbps_ < 0.0f) { |
| // This is the very first sample we get. Use it to initialize the estimate. |
| bitrate_estimate_kbps_ = bitrate_sample_kbps; |
| return; |
| } |
| // Define the sample uncertainty as a function of how far away it is from the |
| // current estimate. With low values of uncertainty_symmetry_cap_ we add more |
| // uncertainty to increases than to decreases. For higher values we approach |
| // symmetry. |
| float scale = uncertainty_scale_; |
| if (in_alr && bitrate_sample_kbps < bitrate_estimate_kbps_) { |
| // Optionally use higher uncertainty for samples obtained during ALR. |
| scale = uncertainty_scale_in_alr_; |
| } |
| float sample_uncertainty = |
| scale * std::abs(bitrate_estimate_kbps_ - bitrate_sample_kbps) / |
| (bitrate_estimate_kbps_ + |
| std::min(bitrate_sample_kbps, |
| uncertainty_symmetry_cap_.Get().kbps<float>())); |
| |
| float sample_var = sample_uncertainty * sample_uncertainty; |
| // Update a bayesian estimate of the rate, weighting it lower if the sample |
| // uncertainty is large. |
| // The bitrate estimate uncertainty is increased with each update to model |
| // that the bitrate changes over time. |
| float pred_bitrate_estimate_var = bitrate_estimate_var_ + 5.f; |
| bitrate_estimate_kbps_ = (sample_var * bitrate_estimate_kbps_ + |
| pred_bitrate_estimate_var * bitrate_sample_kbps) / |
| (sample_var + pred_bitrate_estimate_var); |
| bitrate_estimate_kbps_ = |
| std::max(bitrate_estimate_kbps_, estimate_floor_.Get().kbps<float>()); |
| bitrate_estimate_var_ = sample_var * pred_bitrate_estimate_var / |
| (sample_var + pred_bitrate_estimate_var); |
| BWE_TEST_LOGGING_PLOT(1, "acknowledged_bitrate", at_time.ms(), |
| bitrate_estimate_kbps_ * 1000); |
| } |
| |
| float BitrateEstimator::UpdateWindow(int64_t now_ms, |
| int bytes, |
| int rate_window_ms) { |
| // Reset if time moves backwards. |
| if (now_ms < prev_time_ms_) { |
| prev_time_ms_ = -1; |
| sum_ = 0; |
| current_window_ms_ = 0; |
| } |
| if (prev_time_ms_ >= 0) { |
| current_window_ms_ += now_ms - prev_time_ms_; |
| // Reset if nothing has been received for more than a full window. |
| if (now_ms - prev_time_ms_ > rate_window_ms) { |
| sum_ = 0; |
| current_window_ms_ %= rate_window_ms; |
| } |
| } |
| prev_time_ms_ = now_ms; |
| float bitrate_sample = -1.0f; |
| if (current_window_ms_ >= rate_window_ms) { |
| bitrate_sample = 8.0f * sum_ / static_cast<float>(rate_window_ms); |
| current_window_ms_ -= rate_window_ms; |
| sum_ = 0; |
| } |
| sum_ += bytes; |
| return bitrate_sample; |
| } |
| |
| absl::optional<DataRate> BitrateEstimator::bitrate() const { |
| if (bitrate_estimate_kbps_ < 0.f) |
| return absl::nullopt; |
| return DataRate::kbps(bitrate_estimate_kbps_); |
| } |
| |
| absl::optional<DataRate> BitrateEstimator::PeekRate() const { |
| if (current_window_ms_ > 0) |
| return DataSize::bytes(sum_) / TimeDelta::ms(current_window_ms_); |
| return absl::nullopt; |
| } |
| |
| void BitrateEstimator::ExpectFastRateChange() { |
| // By setting the bitrate-estimate variance to a higher value we allow the |
| // bitrate to change fast for the next few samples. |
| bitrate_estimate_var_ += 200; |
| } |
| |
| } // namespace webrtc |