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1 /*
2  *  Copyright (c) 2012 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 #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_VAD_GMM_H_
12 #define WEBRTC_MODULES_AUDIO_PROCESSING_VAD_GMM_H_
13 
14 namespace webrtc {
15 
16 // A structure that specifies a GMM.
17 // A GMM is formulated as
18 //  f(x) = w[0] * mixture[0] + w[1] * mixture[1] + ... +
19 //         w[num_mixtures - 1] * mixture[num_mixtures - 1];
20 // Where a 'mixture' is a Gaussian density.
21 
22 struct GmmParameters {
23   // weight[n] = log(w[n]) - |dimension|/2 * log(2*pi) - 1/2 * log(det(cov[n]));
24   // where cov[n] is the covariance matrix of mixture n;
25   const double* weight;
26   // pointer to the first element of a |num_mixtures|x|dimension| matrix
27   // where kth row is the mean of the kth mixture.
28   const double* mean;
29   // pointer to the first element of a |num_mixtures|x|dimension|x|dimension|
30   // 3D-matrix, where the kth 2D-matrix is the inverse of the covariance
31   // matrix of the kth mixture.
32   const double* covar_inverse;
33   // Dimensionality of the mixtures.
34   int dimension;
35   // number of the mixtures.
36   int num_mixtures;
37 };
38 
39 // Evaluate the given GMM, according to |gmm_parameters|, at the given point
40 // |x|. If the dimensionality of the given GMM is larger that the maximum
41 // acceptable dimension by the following function -1 is returned.
42 double EvaluateGmm(const double* x, const GmmParameters& gmm_parameters);
43 
44 }  // namespace webrtc
45 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_VAD_GMM_H_
46