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speech_probability_buffer.cc (3241B)

      1 /*
      2 *  Copyright (c) 2022 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/agc2/speech_probability_buffer.h"
     12 
     13 #include "rtc_base/checks.h"
     14 
     15 namespace webrtc {
     16 namespace {
     17 
     18 constexpr float kActivityThreshold = 0.9f;
     19 constexpr int kNumAnalysisFrames = 100;
     20 // We use 12 in AGC2 adaptive digital, but with a slightly different logic.
     21 constexpr int kTransientWidthThreshold = 7;
     22 
     23 }  // namespace
     24 
     25 SpeechProbabilityBuffer::SpeechProbabilityBuffer(
     26    float low_probability_threshold)
     27    : low_probability_threshold_(low_probability_threshold),
     28      probabilities_(kNumAnalysisFrames) {
     29  RTC_DCHECK_GE(low_probability_threshold, 0.0f);
     30  RTC_DCHECK_LE(low_probability_threshold, 1.0f);
     31  RTC_DCHECK(!probabilities_.empty());
     32 }
     33 
     34 void SpeechProbabilityBuffer::Update(float probability) {
     35  // Remove the oldest entry if the circular buffer is full.
     36  if (buffer_is_full_) {
     37    const float oldest_probability = probabilities_[buffer_index_];
     38    sum_probabilities_ -= oldest_probability;
     39  }
     40 
     41  // Check for transients.
     42  if (probability <= low_probability_threshold_) {
     43    // Set a probability lower than the threshold to zero.
     44    probability = 0.0f;
     45 
     46    // Check if this has been a transient.
     47    if (num_high_probability_observations_ <= kTransientWidthThreshold) {
     48      RemoveTransient();
     49    }
     50    num_high_probability_observations_ = 0;
     51  } else if (num_high_probability_observations_ <= kTransientWidthThreshold) {
     52    ++num_high_probability_observations_;
     53  }
     54 
     55  // Update the circular buffer and the current sum.
     56  probabilities_[buffer_index_] = probability;
     57  sum_probabilities_ += probability;
     58 
     59  // Increment the buffer index and check for wrap-around.
     60  if (++buffer_index_ >= kNumAnalysisFrames) {
     61    buffer_index_ = 0;
     62    buffer_is_full_ = true;
     63  }
     64 }
     65 
     66 void SpeechProbabilityBuffer::RemoveTransient() {
     67  // Don't expect to be here if high-activity region is longer than
     68  // `kTransientWidthThreshold` or there has not been any transient.
     69  RTC_DCHECK_LE(num_high_probability_observations_, kTransientWidthThreshold);
     70 
     71  // Replace previously added probabilities with zero.
     72  int index =
     73      (buffer_index_ > 0) ? (buffer_index_ - 1) : (kNumAnalysisFrames - 1);
     74 
     75  while (num_high_probability_observations_-- > 0) {
     76    sum_probabilities_ -= probabilities_[index];
     77    probabilities_[index] = 0.0f;
     78 
     79    // Update the circular buffer index.
     80    index = (index > 0) ? (index - 1) : (kNumAnalysisFrames - 1);
     81  }
     82 }
     83 
     84 bool SpeechProbabilityBuffer::IsActiveSegment() const {
     85  if (!buffer_is_full_) {
     86    return false;
     87  }
     88  if (sum_probabilities_ < kActivityThreshold * kNumAnalysisFrames) {
     89    return false;
     90  }
     91  return true;
     92 }
     93 
     94 void SpeechProbabilityBuffer::Reset() {
     95  sum_probabilities_ = 0.0f;
     96 
     97  // Empty the circular buffer.
     98  buffer_index_ = 0;
     99  buffer_is_full_ = false;
    100  num_high_probability_observations_ = 0;
    101 }
    102 
    103 }  // namespace webrtc