chromium/third_party/webrtc/common_audio/vad/vad_gmm.c

/*
 *  Copyright (c) 2011 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 "common_audio/vad/vad_gmm.h"

#include "common_audio/signal_processing/include/signal_processing_library.h"

static const int32_t kCompVar = …;
static const int16_t kLog2Exp = …;  // log2(exp(1)) in Q12.

// For a normal distribution, the probability of `input` is calculated and
// returned (in Q20). The formula for normal distributed probability is
//
// 1 / s * exp(-(x - m)^2 / (2 * s^2))
//
// where the parameters are given in the following Q domains:
// m = `mean` (Q7)
// s = `std` (Q7)
// x = `input` (Q4)
// in addition to the probability we output `delta` (in Q11) used when updating
// the noise/speech model.
int32_t WebRtcVad_GaussianProbability(int16_t input,
                                      int16_t mean,
                                      int16_t std,
                                      int16_t* delta) { … }