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));
34 int32_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