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/*
* Copyright (c) 2012 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 "webrtc/modules/audio_coding/neteq/delay_peak_detector.h"
#include <algorithm> // max
namespace webrtc {
// The DelayPeakDetector keeps track of severe inter-arrival times, called
// delay peaks. When a peak is observed, the "height" (the time elapsed since
// the previous packet arrival) and the peak "period" (the time since the last
// observed peak) is recorded in a vector. When enough peaks have been observed,
// peak-mode is engaged and the DelayManager asks the DelayPeakDetector for
// the worst peak height.
DelayPeakDetector::DelayPeakDetector()
: peak_found_(false),
peak_detection_threshold_(0),
peak_period_counter_ms_(-1) {
}
void DelayPeakDetector::Reset() {
peak_period_counter_ms_ = -1; // Indicate that next peak is the first.
peak_found_ = false;
peak_history_.clear();
}
// Calculates the threshold in number of packets.
void DelayPeakDetector::SetPacketAudioLength(int length_ms) {
if (length_ms > 0) {
peak_detection_threshold_ = kPeakHeightMs / length_ms;
}
}
int DelayPeakDetector::MaxPeakHeight() const {
int max_height = -1; // Returns -1 for an empty history.
std::list<Peak>::const_iterator it;
for (it = peak_history_.begin(); it != peak_history_.end(); ++it) {
max_height = std::max(max_height, it->peak_height_packets);
}
return max_height;
}
int DelayPeakDetector::MaxPeakPeriod() const {
int max_period = -1; // Returns -1 for an empty history.
std::list<Peak>::const_iterator it;
for (it = peak_history_.begin(); it != peak_history_.end(); ++it) {
max_period = std::max(max_period, it->period_ms);
}
return max_period;
}
bool DelayPeakDetector::Update(int inter_arrival_time, int target_level) {
if (inter_arrival_time > target_level + peak_detection_threshold_ ||
inter_arrival_time > 2 * target_level) {
// A delay peak is observed.
if (peak_period_counter_ms_ == -1) {
// This is the first peak. Reset the period counter.
peak_period_counter_ms_ = 0;
} else if (peak_period_counter_ms_ <= kMaxPeakPeriodMs) {
// This is not the first peak, and the period is valid.
// Store peak data in the vector.
Peak peak_data;
peak_data.period_ms = peak_period_counter_ms_;
peak_data.peak_height_packets = inter_arrival_time;
peak_history_.push_back(peak_data);
while (peak_history_.size() > kMaxNumPeaks) {
// Delete the oldest data point.
peak_history_.pop_front();
}
peak_period_counter_ms_ = 0;
} else if (peak_period_counter_ms_ <= 2 * kMaxPeakPeriodMs) {
// Invalid peak due to too long period. Reset period counter and start
// looking for next peak.
peak_period_counter_ms_ = 0;
} else {
// More than 2 times the maximum period has elapsed since the last peak
// was registered. It seams that the network conditions have changed.
// Reset the peak statistics.
Reset();
}
}
return CheckPeakConditions();
}
void DelayPeakDetector::IncrementCounter(int inc_ms) {
if (peak_period_counter_ms_ >= 0) {
peak_period_counter_ms_ += inc_ms;
}
}
bool DelayPeakDetector::CheckPeakConditions() {
size_t s = peak_history_.size();
if (s >= kMinPeaksToTrigger &&
peak_period_counter_ms_ <= 2 * MaxPeakPeriod()) {
peak_found_ = true;
} else {
peak_found_ = false;
}
return peak_found_;
}
} // namespace webrtc
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