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/*
* Copyright (c) 2019 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 "modules/audio_processing/aec3/dominant_nearend_detector.h"
#include <numeric>
namespace webrtc {
DominantNearendDetector::DominantNearendDetector(
const EchoCanceller3Config::Suppressor::DominantNearendDetection& config,
size_t num_capture_channels)
: enr_threshold_(config.enr_threshold),
enr_exit_threshold_(config.enr_exit_threshold),
snr_threshold_(config.snr_threshold),
hold_duration_(config.hold_duration),
trigger_threshold_(config.trigger_threshold),
use_during_initial_phase_(config.use_during_initial_phase),
num_capture_channels_(num_capture_channels),
trigger_counters_(num_capture_channels_),
hold_counters_(num_capture_channels_) {}
void DominantNearendDetector::Update(
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
nearend_spectrum,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
residual_echo_spectrum,
rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>>
comfort_noise_spectrum,
bool initial_state) {
nearend_state_ = false;
auto low_frequency_energy = [](rtc::ArrayView<const float> spectrum) {
RTC_DCHECK_LE(16, spectrum.size());
return std::accumulate(spectrum.begin() + 1, spectrum.begin() + 16, 0.f);
};
for (size_t ch = 0; ch < num_capture_channels_; ++ch) {
const float ne_sum = low_frequency_energy(nearend_spectrum[ch]);
const float echo_sum = low_frequency_energy(residual_echo_spectrum[ch]);
const float noise_sum = low_frequency_energy(comfort_noise_spectrum[ch]);
// Detect strong active nearend if the nearend is sufficiently stronger than
// the echo and the nearend noise.
if ((!initial_state || use_during_initial_phase_) &&
echo_sum < enr_threshold_ * ne_sum &&
ne_sum > snr_threshold_ * noise_sum) {
if (++trigger_counters_[ch] >= trigger_threshold_) {
// After a period of strong active nearend activity, flag nearend mode.
hold_counters_[ch] = hold_duration_;
trigger_counters_[ch] = trigger_threshold_;
}
} else {
// Forget previously detected strong active nearend activity.
trigger_counters_[ch] = std::max(0, trigger_counters_[ch] - 1);
}
// Exit nearend-state early at strong echo.
if (echo_sum > enr_exit_threshold_ * ne_sum &&
echo_sum > snr_threshold_ * noise_sum) {
hold_counters_[ch] = 0;
}
// Remain in any nearend mode for a certain duration.
hold_counters_[ch] = std::max(0, hold_counters_[ch] - 1);
nearend_state_ = nearend_state_ || hold_counters_[ch] > 0;
}
}
} // namespace webrtc
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