1 /* 2 * Copyright (c) 2016 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 "modules/audio_processing/level_controller/noise_level_estimator.h" 12 13 #include <algorithm> 14 15 #include "modules/audio_processing/audio_buffer.h" 16 #include "modules/audio_processing/logging/apm_data_dumper.h" 17 18 namespace webrtc { 19 NoiseLevelEstimator()20NoiseLevelEstimator::NoiseLevelEstimator() { 21 Initialize(AudioProcessing::kSampleRate48kHz); 22 } 23 ~NoiseLevelEstimator()24NoiseLevelEstimator::~NoiseLevelEstimator() {} 25 Initialize(int sample_rate_hz)26void NoiseLevelEstimator::Initialize(int sample_rate_hz) { 27 noise_energy_ = 1.f; 28 first_update_ = true; 29 min_noise_energy_ = sample_rate_hz * 2.f * 2.f / 100.f; 30 noise_energy_hold_counter_ = 0; 31 } 32 Analyze(SignalClassifier::SignalType signal_type,float frame_energy)33float NoiseLevelEstimator::Analyze(SignalClassifier::SignalType signal_type, 34 float frame_energy) { 35 if (frame_energy <= 0.f) { 36 return noise_energy_; 37 } 38 39 if (first_update_) { 40 // Initialize the noise energy to the frame energy. 41 first_update_ = false; 42 return noise_energy_ = std::max(frame_energy, min_noise_energy_); 43 } 44 45 // Update the noise estimate in a minimum statistics-type manner. 46 if (signal_type == SignalClassifier::SignalType::kStationary) { 47 if (frame_energy > noise_energy_) { 48 // Leak the estimate upwards towards the frame energy if no recent 49 // downward update. 50 noise_energy_hold_counter_ = std::max(noise_energy_hold_counter_ - 1, 0); 51 52 if (noise_energy_hold_counter_ == 0) { 53 noise_energy_ = std::min(noise_energy_ * 1.01f, frame_energy); 54 } 55 } else { 56 // Update smoothly downwards with a limited maximum update magnitude. 57 noise_energy_ = 58 std::max(noise_energy_ * 0.9f, 59 noise_energy_ + 0.05f * (frame_energy - noise_energy_)); 60 noise_energy_hold_counter_ = 1000; 61 } 62 } else { 63 // For a non-stationary signal, leak the estimate downwards in order to 64 // avoid estimate locking due to incorrect signal classification. 65 noise_energy_ = noise_energy_ * 0.99f; 66 } 67 68 // Ensure a minimum of the estimate. 69 return noise_energy_ = std::max(noise_energy_, min_noise_energy_); 70 } 71 72 } // namespace webrtc 73