1 /*
2 * Copyright (c) 2012 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
11 #include "webrtc/modules/audio_coding/neteq/delay_peak_detector.h"
12
13 #include <algorithm> // max
14
15 namespace webrtc {
16
17 // The DelayPeakDetector keeps track of severe inter-arrival times, called
18 // delay peaks. When a peak is observed, the "height" (the time elapsed since
19 // the previous packet arrival) and the peak "period" (the time since the last
20 // observed peak) is recorded in a vector. When enough peaks have been observed,
21 // peak-mode is engaged and the DelayManager asks the DelayPeakDetector for
22 // the worst peak height.
23
DelayPeakDetector()24 DelayPeakDetector::DelayPeakDetector()
25 : peak_found_(false),
26 peak_detection_threshold_(0),
27 peak_period_counter_ms_(-1) {
28 }
29
Reset()30 void DelayPeakDetector::Reset() {
31 peak_period_counter_ms_ = -1; // Indicate that next peak is the first.
32 peak_found_ = false;
33 peak_history_.clear();
34 }
35
36 // Calculates the threshold in number of packets.
SetPacketAudioLength(int length_ms)37 void DelayPeakDetector::SetPacketAudioLength(int length_ms) {
38 if (length_ms > 0) {
39 peak_detection_threshold_ = kPeakHeightMs / length_ms;
40 }
41 }
42
MaxPeakHeight() const43 int DelayPeakDetector::MaxPeakHeight() const {
44 int max_height = -1; // Returns -1 for an empty history.
45 std::list<Peak>::const_iterator it;
46 for (it = peak_history_.begin(); it != peak_history_.end(); ++it) {
47 max_height = std::max(max_height, it->peak_height_packets);
48 }
49 return max_height;
50 }
51
MaxPeakPeriod() const52 int DelayPeakDetector::MaxPeakPeriod() const {
53 int max_period = -1; // Returns -1 for an empty history.
54 std::list<Peak>::const_iterator it;
55 for (it = peak_history_.begin(); it != peak_history_.end(); ++it) {
56 max_period = std::max(max_period, it->period_ms);
57 }
58 return max_period;
59 }
60
Update(int inter_arrival_time,int target_level)61 bool DelayPeakDetector::Update(int inter_arrival_time, int target_level) {
62 if (inter_arrival_time > target_level + peak_detection_threshold_ ||
63 inter_arrival_time > 2 * target_level) {
64 // A delay peak is observed.
65 if (peak_period_counter_ms_ == -1) {
66 // This is the first peak. Reset the period counter.
67 peak_period_counter_ms_ = 0;
68 } else if (peak_period_counter_ms_ <= kMaxPeakPeriodMs) {
69 // This is not the first peak, and the period is valid.
70 // Store peak data in the vector.
71 Peak peak_data;
72 peak_data.period_ms = peak_period_counter_ms_;
73 peak_data.peak_height_packets = inter_arrival_time;
74 peak_history_.push_back(peak_data);
75 while (peak_history_.size() > kMaxNumPeaks) {
76 // Delete the oldest data point.
77 peak_history_.pop_front();
78 }
79 peak_period_counter_ms_ = 0;
80 } else if (peak_period_counter_ms_ <= 2 * kMaxPeakPeriodMs) {
81 // Invalid peak due to too long period. Reset period counter and start
82 // looking for next peak.
83 peak_period_counter_ms_ = 0;
84 } else {
85 // More than 2 times the maximum period has elapsed since the last peak
86 // was registered. It seams that the network conditions have changed.
87 // Reset the peak statistics.
88 Reset();
89 }
90 }
91 return CheckPeakConditions();
92 }
93
IncrementCounter(int inc_ms)94 void DelayPeakDetector::IncrementCounter(int inc_ms) {
95 if (peak_period_counter_ms_ >= 0) {
96 peak_period_counter_ms_ += inc_ms;
97 }
98 }
99
CheckPeakConditions()100 bool DelayPeakDetector::CheckPeakConditions() {
101 size_t s = peak_history_.size();
102 if (s >= kMinPeaksToTrigger &&
103 peak_period_counter_ms_ <= 2 * MaxPeakPeriod()) {
104 peak_found_ = true;
105 } else {
106 peak_found_ = false;
107 }
108 return peak_found_;
109 }
110 } // namespace webrtc
111