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/common_audio/vad/vad_sp.h" 12 13 #include <assert.h> 14 15 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h" 16 #include "webrtc/common_audio/vad/vad_core.h" 17 #include "webrtc/typedefs.h" 18 19 // Allpass filter coefficients, upper and lower, in Q13. 20 // Upper: 0.64, Lower: 0.17. 21 static const int16_t kAllPassCoefsQ13[2] = { 5243, 1392 }; // Q13. 22 static const int16_t kSmoothingDown = 6553; // 0.2 in Q15. 23 static const int16_t kSmoothingUp = 32439; // 0.99 in Q15. 24 25 // TODO(bjornv): Move this function to vad_filterbank.c. 26 // Downsampling filter based on splitting filter and allpass functions. 27 void WebRtcVad_Downsampling(const int16_t* signal_in, 28 int16_t* signal_out, 29 int32_t* filter_state, 30 int in_length) { 31 int16_t tmp16_1 = 0, tmp16_2 = 0; 32 int32_t tmp32_1 = filter_state[0]; 33 int32_t tmp32_2 = filter_state[1]; 34 int n = 0; 35 int half_length = (in_length >> 1); // Downsampling by 2 gives half length. 36 37 // Filter coefficients in Q13, filter state in Q0. 38 for (n = 0; n < half_length; n++) { 39 // All-pass filtering upper branch. 40 tmp16_1 = (int16_t) ((tmp32_1 >> 1) + 41 WEBRTC_SPL_MUL_16_16_RSFT(kAllPassCoefsQ13[0], *signal_in, 14)); 42 *signal_out = tmp16_1; 43 tmp32_1 = (int32_t) (*signal_in++) - 44 WEBRTC_SPL_MUL_16_16_RSFT(kAllPassCoefsQ13[0], tmp16_1, 12); 45 46 // All-pass filtering lower branch. 47 tmp16_2 = (int16_t) ((tmp32_2 >> 1) + 48 WEBRTC_SPL_MUL_16_16_RSFT(kAllPassCoefsQ13[1], *signal_in, 14)); 49 *signal_out++ += tmp16_2; 50 tmp32_2 = (int32_t) (*signal_in++) - 51 WEBRTC_SPL_MUL_16_16_RSFT(kAllPassCoefsQ13[1], tmp16_2, 12); 52 } 53 // Store the filter states. 54 filter_state[0] = tmp32_1; 55 filter_state[1] = tmp32_2; 56 } 57 58 // Inserts |feature_value| into |low_value_vector|, if it is one of the 16 59 // smallest values the last 100 frames. Then calculates and returns the median 60 // of the five smallest values. 61 int16_t WebRtcVad_FindMinimum(VadInstT* self, 62 int16_t feature_value, 63 int channel) { 64 int i = 0, j = 0; 65 int position = -1; 66 // Offset to beginning of the 16 minimum values in memory. 67 const int offset = (channel << 4); 68 int16_t current_median = 1600; 69 int16_t alpha = 0; 70 int32_t tmp32 = 0; 71 // Pointer to memory for the 16 minimum values and the age of each value of 72 // the |channel|. 73 int16_t* age = &self->index_vector[offset]; 74 int16_t* smallest_values = &self->low_value_vector[offset]; 75 76 assert(channel < kNumChannels); 77 78 // Each value in |smallest_values| is getting 1 loop older. Update |age|, and 79 // remove old values. 80 for (i = 0; i < 16; i++) { 81 if (age[i] != 100) { 82 age[i]++; 83 } else { 84 // Too old value. Remove from memory and shift larger values downwards. 85 for (j = i; j < 16; j++) { 86 smallest_values[j] = smallest_values[j + 1]; 87 age[j] = age[j + 1]; 88 } 89 age[15] = 101; 90 smallest_values[15] = 10000; 91 } 92 } 93 94 // Check if |feature_value| is smaller than any of the values in 95 // |smallest_values|. If so, find the |position| where to insert the new value 96 // (|feature_value|). 97 if (feature_value < smallest_values[7]) { 98 if (feature_value < smallest_values[3]) { 99 if (feature_value < smallest_values[1]) { 100 if (feature_value < smallest_values[0]) { 101 position = 0; 102 } else { 103 position = 1; 104 } 105 } else if (feature_value < smallest_values[2]) { 106 position = 2; 107 } else { 108 position = 3; 109 } 110 } else if (feature_value < smallest_values[5]) { 111 if (feature_value < smallest_values[4]) { 112 position = 4; 113 } else { 114 position = 5; 115 } 116 } else if (feature_value < smallest_values[6]) { 117 position = 6; 118 } else { 119 position = 7; 120 } 121 } else if (feature_value < smallest_values[15]) { 122 if (feature_value < smallest_values[11]) { 123 if (feature_value < smallest_values[9]) { 124 if (feature_value < smallest_values[8]) { 125 position = 8; 126 } else { 127 position = 9; 128 } 129 } else if (feature_value < smallest_values[10]) { 130 position = 10; 131 } else { 132 position = 11; 133 } 134 } else if (feature_value < smallest_values[13]) { 135 if (feature_value < smallest_values[12]) { 136 position = 12; 137 } else { 138 position = 13; 139 } 140 } else if (feature_value < smallest_values[14]) { 141 position = 14; 142 } else { 143 position = 15; 144 } 145 } 146 147 // If we have detected a new small value, insert it at the correct position 148 // and shift larger values up. 149 if (position > -1) { 150 for (i = 15; i > position; i--) { 151 smallest_values[i] = smallest_values[i - 1]; 152 age[i] = age[i - 1]; 153 } 154 smallest_values[position] = feature_value; 155 age[position] = 1; 156 } 157 158 // Get |current_median|. 159 if (self->frame_counter > 2) { 160 current_median = smallest_values[2]; 161 } else if (self->frame_counter > 0) { 162 current_median = smallest_values[0]; 163 } 164 165 // Smooth the median value. 166 if (self->frame_counter > 0) { 167 if (current_median < self->mean_value[channel]) { 168 alpha = kSmoothingDown; // 0.2 in Q15. 169 } else { 170 alpha = kSmoothingUp; // 0.99 in Q15. 171 } 172 } 173 tmp32 = WEBRTC_SPL_MUL_16_16(alpha + 1, self->mean_value[channel]); 174 tmp32 += WEBRTC_SPL_MUL_16_16(WEBRTC_SPL_WORD16_MAX - alpha, current_median); 175 tmp32 += 16384; 176 self->mean_value[channel] = (int16_t) (tmp32 >> 15); 177 178 return self->mean_value[channel]; 179 } 180
