Pull the Voice Activity Detector out from the AGC

webrtc/modules/audio_processing/agc/pole_zero_filter.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/pole_zero_filter.h"
-
-#include <stdlib.h>
-#include <string.h>
-#include <algorithm>
-
-namespace webrtc {
-
-PoleZeroFilter* PoleZeroFilter::Create(const float* numerator_coefficients,
-                                       int order_numerator,
-                                       const float* denominator_coefficients,
-                                       int order_denominator) {
-  if (order_numerator < 0 ||
-      order_denominator < 0 ||
-      order_numerator > kMaxFilterOrder ||
-      order_denominator > kMaxFilterOrder ||
-      denominator_coefficients[0] == 0 ||
-      numerator_coefficients == NULL ||
-      denominator_coefficients == NULL)
-    return NULL;
-  return new PoleZeroFilter(numerator_coefficients, order_numerator,
-                            denominator_coefficients, order_denominator);
-}
-
-PoleZeroFilter::PoleZeroFilter(const float* numerator_coefficients,
-                               int order_numerator,
-                               const float* denominator_coefficients,
-                               int order_denominator)
-    : past_input_(),
-      past_output_(),
-      numerator_coefficients_(),
-      denominator_coefficients_(),
-      order_numerator_(order_numerator),
-      order_denominator_(order_denominator),
-      highest_order_(std::max(order_denominator, order_numerator)) {
-  memcpy(numerator_coefficients_, numerator_coefficients,
-         sizeof(numerator_coefficients_[0]) * (order_numerator_ + 1));
-  memcpy(denominator_coefficients_, denominator_coefficients,
-         sizeof(denominator_coefficients_[0]) * (order_denominator_ + 1));
-
-  if (denominator_coefficients_[0] != 1) {
-    for (int n = 0; n <= order_numerator_; n++)
-      numerator_coefficients_[n] /= denominator_coefficients_[0];
-    for (int n = 0; n <= order_denominator_; n++)
-      denominator_coefficients_[n] /= denominator_coefficients_[0];
-  }
-}
-
-template <typename T>
-static float FilterArPast(const T* past, int order,
-                          const float* coefficients) {
-  float sum = 0.0f;
-  int past_index = order - 1;
-  for (int k = 1; k <= order; k++, past_index--)
-    sum += coefficients[k] * past[past_index];
-  return sum;
-}
-
-int PoleZeroFilter::Filter(const int16_t* in,
-                           int num_input_samples,
-                           float* output) {
-  if (in == NULL || num_input_samples < 0 || output == NULL)
-    return -1;
-  // This is the typical case, just a memcpy.
-  const int k = std::min(num_input_samples, highest_order_);
-  int n;
-  for (n = 0; n < k; n++) {
-    output[n] = in[n] * numerator_coefficients_[0];
-    output[n] += FilterArPast(&past_input_[n], order_numerator_,
-                              numerator_coefficients_);
-    output[n] -= FilterArPast(&past_output_[n], order_denominator_,
-                              denominator_coefficients_);
-
-    past_input_[n + order_numerator_] = in[n];
-    past_output_[n + order_denominator_] = output[n];
-  }
-  if (highest_order_ < num_input_samples) {
-    for (int m = 0; n < num_input_samples; n++, m++) {
-      output[n] = in[n] * numerator_coefficients_[0];
-      output[n] += FilterArPast(&in[m], order_numerator_,
-                                numerator_coefficients_);
-      output[n] -= FilterArPast(&output[m], order_denominator_,
-                                denominator_coefficients_);
-    }
-    // Record into the past signal.
-    memcpy(past_input_, &in[num_input_samples - order_numerator_],
-           sizeof(in[0]) * order_numerator_);
-    memcpy(past_output_, &output[num_input_samples - order_denominator_],
-           sizeof(output[0]) * order_denominator_);
-  } else {
-    // Odd case that the length of the input is shorter that filter order.
-    memmove(past_input_, &past_input_[num_input_samples], order_numerator_ *
-            sizeof(past_input_[0]));
-    memmove(past_output_, &past_output_[num_input_samples], order_denominator_ *
-            sizeof(past_output_[0]));
-  }
-  return 0;
-}
-
-}  // namespace webrtc
-