clockdrift_detector.cc (2023B)
1 /* 2 * Copyright (c) 2018 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 #include "modules/audio_processing/aec3/clockdrift_detector.h" 11 12 namespace webrtc { 13 14 ClockdriftDetector::ClockdriftDetector() 15 : level_(Level::kNone), stability_counter_(0) { 16 delay_history_.fill(0); 17 } 18 19 ClockdriftDetector::~ClockdriftDetector() = default; 20 21 void ClockdriftDetector::Update(int delay_estimate) { 22 if (delay_estimate == delay_history_[0]) { 23 // Reset clockdrift level if delay estimate is stable for 7500 blocks (30 24 // seconds). 25 if (++stability_counter_ > 7500) 26 level_ = Level::kNone; 27 return; 28 } 29 30 stability_counter_ = 0; 31 const int d1 = delay_history_[0] - delay_estimate; 32 const int d2 = delay_history_[1] - delay_estimate; 33 const int d3 = delay_history_[2] - delay_estimate; 34 35 // Patterns recognized as positive clockdrift: 36 // [x-3], x-2, x-1, x. 37 // [x-3], x-1, x-2, x. 38 const bool probable_drift_up = 39 (d1 == -1 && d2 == -2) || (d1 == -2 && d2 == -1); 40 const bool drift_up = probable_drift_up && d3 == -3; 41 42 // Patterns recognized as negative clockdrift: 43 // [x+3], x+2, x+1, x. 44 // [x+3], x+1, x+2, x. 45 const bool probable_drift_down = (d1 == 1 && d2 == 2) || (d1 == 2 && d2 == 1); 46 const bool drift_down = probable_drift_down && d3 == 3; 47 48 // Set clockdrift level. 49 if (drift_up || drift_down) { 50 level_ = Level::kVerified; 51 } else if ((probable_drift_up || probable_drift_down) && 52 level_ == Level::kNone) { 53 level_ = Level::kProbable; 54 } 55 56 // Shift delay history one step. 57 delay_history_[2] = delay_history_[1]; 58 delay_history_[1] = delay_history_[0]; 59 delay_history_[0] = delay_estimate; 60 } 61 } // namespace webrtc