Line data    Source code

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