1/*
2 *  Copyright (c) 2011 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// Gaussian probability calculations internally used in vad_core.c.
12
13#ifndef WEBRTC_COMMON_AUDIO_VAD_VAD_GMM_H_
14#define WEBRTC_COMMON_AUDIO_VAD_VAD_GMM_H_
15
16#include "typedefs.h"
17
18// Calculates the probability for |input|, given that |input| comes from a
19// normal distribution with mean and standard deviation (|mean|, |std|).
20//
21// Inputs:
22//      - input         : input sample in Q4.
23//      - mean          : mean input in the statistical model, Q7.
24//      - std           : standard deviation, Q7.
25//
26// Output:
27//
28//      - delta         : input used when updating the model, Q11.
29//                        |delta| = (|input| - |mean|) / |std|^2.
30//
31// Return:
32//   (probability for |input|) =
33//    1 / |std| * exp(-(|input| - |mean|)^2 / (2 * |std|^2));
34int32_t WebRtcVad_GaussianProbability(int16_t input,
35                                      int16_t mean,
36                                      int16_t std,
37                                      int16_t* delta);
38
39#endif  // WEBRTC_COMMON_AUDIO_VAD_VAD_GMM_H_
40