Pull the Voice Activity Detector out from the AGC

webrtc/modules/audio_processing/agc/gmm.cc

-/*
- *  Copyright (c) 2012 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 "webrtc/modules/audio_processing/agc/gmm.h"
-
-#include <math.h>
-#include <stdlib.h>
-
-#include "webrtc/typedefs.h"
-
-namespace webrtc {
-
-static const int kMaxDimension = 10;
-
-static void RemoveMean(const double* in, const double* mean_vec,
-                       int dimension, double* out) {
-  for (int n = 0; n < dimension; ++n)
-    out[n] = in[n] - mean_vec[n];
-}
-
-static double ComputeExponent(const double* in, const double* covar_inv,
-                              int dimension) {
-  double q = 0;
-  for (int i = 0; i < dimension; ++i) {
-    double v = 0;
-    for (int j = 0; j < dimension; j++)
-      v += (*covar_inv++) * in[j];
-    q += v * in[i];
-  }
-  q *= -0.5;
-  return q;
-}
-
-double EvaluateGmm(const double* x, const GmmParameters& gmm_parameters) {
-  if (gmm_parameters.dimension > kMaxDimension) {
-    return -1;  // This is invalid pdf so the caller can check this.
-  }
-  double f = 0;
-  double v[kMaxDimension];
-  const double* mean_vec = gmm_parameters.mean;
-  const double* covar_inv = gmm_parameters.covar_inverse;
-
-  for (int n = 0; n < gmm_parameters.num_mixtures; n++) {
-    RemoveMean(x, mean_vec, gmm_parameters.dimension, v);
-    double q = ComputeExponent(v, covar_inv, gmm_parameters.dimension) +
-        gmm_parameters.weight[n];
-    f += exp(q);
-    mean_vec += gmm_parameters.dimension;
-    covar_inv += gmm_parameters.dimension * gmm_parameters.dimension;
-  }
-  return f;
-}
-
-}  // namespace webrtc