62 lines
2.0 KiB
C++
62 lines
2.0 KiB
C++
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/*
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* Copyright (c) 2018 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 "modules/audio_processing/aec3/clockdrift_detector.h"
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namespace webrtc {
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ClockdriftDetector::ClockdriftDetector()
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: level_(Level::kNone), stability_counter_(0) {
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delay_history_.fill(0);
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}
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ClockdriftDetector::~ClockdriftDetector() = default;
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void ClockdriftDetector::Update(int delay_estimate) {
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if (delay_estimate == delay_history_[0]) {
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// Reset clockdrift level if delay estimate is stable for 7500 blocks (30
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// seconds).
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if (++stability_counter_ > 7500)
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level_ = Level::kNone;
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return;
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}
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stability_counter_ = 0;
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const int d1 = delay_history_[0] - delay_estimate;
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const int d2 = delay_history_[1] - delay_estimate;
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const int d3 = delay_history_[2] - delay_estimate;
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// Patterns recognized as positive clockdrift:
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// [x-3], x-2, x-1, x.
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// [x-3], x-1, x-2, x.
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const bool probable_drift_up =
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(d1 == -1 && d2 == -2) || (d1 == -2 && d2 == -1);
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const bool drift_up = probable_drift_up && d3 == -3;
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// Patterns recognized as negative clockdrift:
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// [x+3], x+2, x+1, x.
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// [x+3], x+1, x+2, x.
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const bool probable_drift_down = (d1 == 1 && d2 == 2) || (d1 == 2 && d2 == 1);
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const bool drift_down = probable_drift_down && d3 == 3;
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// Set clockdrift level.
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if (drift_up || drift_down) {
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level_ = Level::kVerified;
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} else if ((probable_drift_up || probable_drift_down) &&
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level_ == Level::kNone) {
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level_ = Level::kProbable;
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}
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// Shift delay history one step.
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delay_history_[2] = delay_history_[1];
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delay_history_[1] = delay_history_[0];
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delay_history_[0] = delay_estimate;
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}
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} // namespace webrtc
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