e75d96b5bd
Reason for revert:
Resetting the estimate means that we need to start gathering data from scratch again. The combination of
1) DelayBasedEstimator not reacting to overuse unless there is a valid estimate of the acknowledged bitrate, and
2) AcknowledgedBitrateEstimator needing a significant amount of time/data to obtain an provide an estimate
causes poor performance in simulations/tests. It is not clear whether this will affect real networks negatively, but I suggest reverting this to be on the safe side.
See also https://bugs.chromium.org/p/webrtc/issues/detail?id=7884
Original issue's description:
> Test and fix for huge bwe drop after alr state.
>
> BUG=webrtc:7746
>
> Review-Url: https://codereview.webrtc.org/2931873002
> Cr-Commit-Position: refs/heads/master@{#18692}
> Committed: 37aa8ba616
TBR=solenberg@webrtc.org,kwiberg@webrtc.org,minyue@webrtc.org,holmer@chromium.org,philipel@webrtc.org,oprypin@webrtc.org,holmer@google.com,stefan@webrtc.org,tschumim@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:7746
Review-Url: https://codereview.webrtc.org/2964213002
Cr-Commit-Position: refs/heads/master@{#18866}
116 lines
4.1 KiB
C++
116 lines
4.1 KiB
C++
/*
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* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "webrtc/modules/congestion_controller/acknowledge_bitrate_estimator.h"
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#include <cmath>
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#include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_logging.h"
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#include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
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namespace webrtc {
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namespace {
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constexpr int kInitialRateWindowMs = 500;
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constexpr int kRateWindowMs = 150;
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bool IsInSendTimeHistory(const PacketFeedback& packet) {
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return packet.send_time_ms >= 0;
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}
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} // namespace
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AcknowledgedBitrateEstimator::AcknowledgedBitrateEstimator()
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: sum_(0),
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current_win_ms_(0),
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prev_time_ms_(-1),
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bitrate_estimate_(-1.0f),
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bitrate_estimate_var_(50.0f) {}
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void AcknowledgedBitrateEstimator::IncomingPacketFeedbackVector(
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const std::vector<PacketFeedback>& packet_feedback_vector) {
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RTC_DCHECK(std::is_sorted(packet_feedback_vector.begin(),
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packet_feedback_vector.end(),
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PacketFeedbackComparator()));
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for (const auto& packet : packet_feedback_vector) {
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if (IsInSendTimeHistory(packet))
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Update(packet.arrival_time_ms, packet.payload_size);
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}
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}
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void AcknowledgedBitrateEstimator::Update(int64_t now_ms, int bytes) {
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int rate_window_ms = kRateWindowMs;
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// We use a larger window at the beginning to get a more stable sample that
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// we can use to initialize the estimate.
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if (bitrate_estimate_ < 0.f)
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rate_window_ms = kInitialRateWindowMs;
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float bitrate_sample = UpdateWindow(now_ms, bytes, rate_window_ms);
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if (bitrate_sample < 0.0f)
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return;
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if (bitrate_estimate_ < 0.0f) {
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// This is the very first sample we get. Use it to initialize the estimate.
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bitrate_estimate_ = bitrate_sample;
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return;
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}
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// Define the sample uncertainty as a function of how far away it is from the
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// current estimate.
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float sample_uncertainty =
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10.0f * std::abs(bitrate_estimate_ - bitrate_sample) / bitrate_estimate_;
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float sample_var = sample_uncertainty * sample_uncertainty;
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// Update a bayesian estimate of the rate, weighting it lower if the sample
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// uncertainty is large.
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// The bitrate estimate uncertainty is increased with each update to model
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// that the bitrate changes over time.
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float pred_bitrate_estimate_var = bitrate_estimate_var_ + 5.f;
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bitrate_estimate_ = (sample_var * bitrate_estimate_ +
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pred_bitrate_estimate_var * bitrate_sample) /
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(sample_var + pred_bitrate_estimate_var);
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bitrate_estimate_var_ = sample_var * pred_bitrate_estimate_var /
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(sample_var + pred_bitrate_estimate_var);
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BWE_TEST_LOGGING_PLOT(1, "acknowledged_bitrate", now_ms,
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bitrate_estimate_ * 1000);
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}
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float AcknowledgedBitrateEstimator::UpdateWindow(int64_t now_ms,
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int bytes,
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int rate_window_ms) {
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// Reset if time moves backwards.
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if (now_ms < prev_time_ms_) {
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prev_time_ms_ = -1;
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sum_ = 0;
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current_win_ms_ = 0;
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}
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if (prev_time_ms_ >= 0) {
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current_win_ms_ += now_ms - prev_time_ms_;
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// Reset if nothing has been received for more than a full window.
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if (now_ms - prev_time_ms_ > rate_window_ms) {
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sum_ = 0;
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current_win_ms_ %= rate_window_ms;
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}
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}
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prev_time_ms_ = now_ms;
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float bitrate_sample = -1.0f;
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if (current_win_ms_ >= rate_window_ms) {
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bitrate_sample = 8.0f * sum_ / static_cast<float>(rate_window_ms);
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current_win_ms_ -= rate_window_ms;
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sum_ = 0;
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}
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sum_ += bytes;
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return bitrate_sample;
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}
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rtc::Optional<uint32_t> AcknowledgedBitrateEstimator::bitrate_bps() const {
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if (bitrate_estimate_ < 0.f)
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return rtc::Optional<uint32_t>();
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return rtc::Optional<uint32_t>(bitrate_estimate_ * 1000);
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}
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} // namespace webrtc
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