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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 #include "webrtc/modules/audio_processing/vad/pole_zero_filter.h" | |
12 | |
13 #include <stdlib.h> | |
14 #include <string.h> | |
15 #include <algorithm> | |
16 | |
17 namespace webrtc { | |
18 | |
19 PoleZeroFilter* PoleZeroFilter::Create(const float* numerator_coefficients, | |
20 int order_numerator, | |
21 const float* denominator_coefficients, | |
22 int order_denominator) { | |
23 if (order_numerator < 0 || order_denominator < 0 || | |
24 order_numerator > kMaxFilterOrder || | |
25 order_denominator > kMaxFilterOrder || denominator_coefficients[0] == 0 || | |
26 numerator_coefficients == NULL || denominator_coefficients == NULL) | |
27 return NULL; | |
28 return new PoleZeroFilter(numerator_coefficients, order_numerator, | |
29 denominator_coefficients, order_denominator); | |
30 } | |
31 | |
32 PoleZeroFilter::PoleZeroFilter(const float* numerator_coefficients, | |
33 int order_numerator, | |
34 const float* denominator_coefficients, | |
35 int order_denominator) | |
36 : past_input_(), | |
37 past_output_(), | |
38 numerator_coefficients_(), | |
39 denominator_coefficients_(), | |
40 order_numerator_(order_numerator), | |
41 order_denominator_(order_denominator), | |
42 highest_order_(std::max(order_denominator, order_numerator)) { | |
43 memcpy(numerator_coefficients_, numerator_coefficients, | |
44 sizeof(numerator_coefficients_[0]) * (order_numerator_ + 1)); | |
45 memcpy(denominator_coefficients_, denominator_coefficients, | |
46 sizeof(denominator_coefficients_[0]) * (order_denominator_ + 1)); | |
47 | |
48 if (denominator_coefficients_[0] != 1) { | |
49 for (int n = 0; n <= order_numerator_; n++) | |
50 numerator_coefficients_[n] /= denominator_coefficients_[0]; | |
51 for (int n = 0; n <= order_denominator_; n++) | |
52 denominator_coefficients_[n] /= denominator_coefficients_[0]; | |
53 } | |
54 } | |
55 | |
56 template <typename T> | |
57 static float FilterArPast(const T* past, int order, const float* coefficients) { | |
58 float sum = 0.0f; | |
59 int past_index = order - 1; | |
60 for (int k = 1; k <= order; k++, past_index--) | |
61 sum += coefficients[k] * past[past_index]; | |
62 return sum; | |
63 } | |
64 | |
65 int PoleZeroFilter::Filter(const int16_t* in, | |
66 int num_input_samples, | |
67 float* output) { | |
68 if (in == NULL || num_input_samples < 0 || output == NULL) | |
69 return -1; | |
70 // This is the typical case, just a memcpy. | |
71 const int k = std::min(num_input_samples, highest_order_); | |
72 int n; | |
73 for (n = 0; n < k; n++) { | |
74 output[n] = in[n] * numerator_coefficients_[0]; | |
75 output[n] += FilterArPast(&past_input_[n], order_numerator_, | |
76 numerator_coefficients_); | |
77 output[n] -= FilterArPast(&past_output_[n], order_denominator_, | |
78 denominator_coefficients_); | |
79 | |
80 past_input_[n + order_numerator_] = in[n]; | |
81 past_output_[n + order_denominator_] = output[n]; | |
82 } | |
83 if (highest_order_ < num_input_samples) { | |
84 for (int m = 0; n < num_input_samples; n++, m++) { | |
85 output[n] = in[n] * numerator_coefficients_[0]; | |
86 output[n] += | |
87 FilterArPast(&in[m], order_numerator_, numerator_coefficients_); | |
88 output[n] -= FilterArPast(&output[m], order_denominator_, | |
89 denominator_coefficients_); | |
90 } | |
91 // Record into the past signal. | |
92 memcpy(past_input_, &in[num_input_samples - order_numerator_], | |
93 sizeof(in[0]) * order_numerator_); | |
94 memcpy(past_output_, &output[num_input_samples - order_denominator_], | |
95 sizeof(output[0]) * order_denominator_); | |
96 } else { | |
97 // Odd case that the length of the input is shorter that filter order. | |
98 memmove(past_input_, &past_input_[num_input_samples], | |
99 order_numerator_ * sizeof(past_input_[0])); | |
100 memmove(past_output_, &past_output_[num_input_samples], | |
101 order_denominator_ * sizeof(past_output_[0])); | |
102 } | |
103 return 0; | |
104 } | |
105 | |
106 } // namespace webrtc | |
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