blob: 3ab75b1ce67e4f15da118147e9883f7d9e44f37e [file] [log] [blame]
/*
* Copyright (c) 2016 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/level_controller/gain_selector.h"
#include <math.h>
#include <algorithm>
#include "modules/audio_processing/include/audio_processing.h"
#include "modules/audio_processing/level_controller/level_controller_constants.h"
#include "rtc_base/checks.h"
namespace webrtc {
GainSelector::GainSelector() {
Initialize(AudioProcessing::kSampleRate48kHz);
}
void GainSelector::Initialize(int sample_rate_hz) {
gain_ = 1.f;
frame_length_ = rtc::CheckedDivExact(sample_rate_hz, 100);
highly_nonstationary_signal_hold_counter_ = 0;
}
// Chooses the gain to apply by the level controller such that
// 1) The level of the stationary noise does not exceed
// a predefined threshold.
// 2) The gain does not exceed the gain that has been found
// to saturate the signal.
// 3) The peak level achieves the target peak level.
// 4) The gain is not below 1.
// 4) The gain is 1 if the signal has been classified as stationary
// for a long time.
// 5) The gain is not above the maximum gain.
float GainSelector::GetNewGain(float peak_level,
float noise_energy,
float saturating_gain,
bool gain_jumpstart,
SignalClassifier::SignalType signal_type) {
RTC_DCHECK_LT(0.f, peak_level);
if (signal_type == SignalClassifier::SignalType::kHighlyNonStationary ||
gain_jumpstart) {
highly_nonstationary_signal_hold_counter_ = 100;
} else {
highly_nonstationary_signal_hold_counter_ =
std::max(0, highly_nonstationary_signal_hold_counter_ - 1);
}
float desired_gain;
if (highly_nonstationary_signal_hold_counter_ > 0) {
// Compute a desired gain that ensures that the peak level is amplified to
// the target level.
desired_gain = kTargetLcPeakLevel / peak_level;
// Limit the desired gain so that it does not amplify the noise too much.
float max_noise_energy = kMaxLcNoisePower * frame_length_;
if (noise_energy * desired_gain * desired_gain > max_noise_energy) {
RTC_DCHECK_LE(0.f, noise_energy);
desired_gain = sqrtf(max_noise_energy / noise_energy);
}
} else {
// If the signal has been stationary for a long while, apply a gain of 1 to
// avoid amplifying pure noise.
desired_gain = 1.0f;
}
// Smootly update the gain towards the desired gain.
gain_ += 0.2f * (desired_gain - gain_);
// Limit the gain to not exceed the maximum and the saturating gains, and to
// ensure that the lowest possible gain is 1.
gain_ = std::min(gain_, saturating_gain);
gain_ = std::min(gain_, kMaxLcGain);
gain_ = std::max(gain_, 1.f);
return gain_;
}
} // namespace webrtc