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/*
* 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 "common_audio/vad/vad_sp.h"
#include "rtc_base/checks.h"
#include "common_audio/signal_processing/include/signal_processing_library.h"
#include "common_audio/vad/vad_core.h"
// Allpass filter coefficients, upper and lower, in Q13.
// Upper: 0.64, Lower: 0.17.
static const int16_t kAllPassCoefsQ13[2] = { 5243, 1392 }; // Q13.
static const int16_t kSmoothingDown = 6553; // 0.2 in Q15.
static const int16_t kSmoothingUp = 32439; // 0.99 in Q15.
// TODO(bjornv): Move this function to vad_filterbank.c.
// Downsampling filter based on splitting filter and allpass functions.
void WebRtcVad_Downsampling(const int16_t* signal_in,
int16_t* signal_out,
int32_t* filter_state,
size_t in_length) {
int16_t tmp16_1 = 0, tmp16_2 = 0;
int32_t tmp32_1 = filter_state[0];
int32_t tmp32_2 = filter_state[1];
size_t n = 0;
// Downsampling by 2 gives half length.
size_t half_length = (in_length >> 1);
// Filter coefficients in Q13, filter state in Q0.
for (n = 0; n < half_length; n++) {
// All-pass filtering upper branch.
tmp16_1 = (int16_t) ((tmp32_1 >> 1) +
((kAllPassCoefsQ13[0] * *signal_in) >> 14));
*signal_out = tmp16_1;
tmp32_1 = (int32_t)(*signal_in++) - ((kAllPassCoefsQ13[0] * tmp16_1) >> 12);
// All-pass filtering lower branch.
tmp16_2 = (int16_t) ((tmp32_2 >> 1) +
((kAllPassCoefsQ13[1] * *signal_in) >> 14));
*signal_out++ += tmp16_2;
tmp32_2 = (int32_t)(*signal_in++) - ((kAllPassCoefsQ13[1] * tmp16_2) >> 12);
}
// Store the filter states.
filter_state[0] = tmp32_1;
filter_state[1] = tmp32_2;
}
// Inserts `feature_value` into `low_value_vector`, if it is one of the 16
// smallest values the last 100 frames. Then calculates and returns the median
// of the five smallest values.
int16_t WebRtcVad_FindMinimum(VadInstT* self,
int16_t feature_value,
int channel) {
int i = 0, j = 0;
int position = -1;
// Offset to beginning of the 16 minimum values in memory.
const int offset = (channel << 4);
int16_t current_median = 1600;
int16_t alpha = 0;
int32_t tmp32 = 0;
// Pointer to memory for the 16 minimum values and the age of each value of
// the `channel`.
int16_t* age = &self->index_vector[offset];
int16_t* smallest_values = &self->low_value_vector[offset];
RTC_DCHECK_LT(channel, kNumChannels);
// Each value in `smallest_values` is getting 1 loop older. Update `age`, and
// remove old values.
for (i = 0; i < 16; i++) {
if (age[i] != 100) {
age[i]++;
} else {
// Too old value. Remove from memory and shift larger values downwards.
for (j = i; j < 15; j++) {
smallest_values[j] = smallest_values[j + 1];
age[j] = age[j + 1];
}
age[15] = 101;
smallest_values[15] = 10000;
}
}
// Check if `feature_value` is smaller than any of the values in
// `smallest_values`. If so, find the `position` where to insert the new value
// (`feature_value`).
if (feature_value < smallest_values[7]) {
if (feature_value < smallest_values[3]) {
if (feature_value < smallest_values[1]) {
if (feature_value < smallest_values[0]) {
position = 0;
} else {
position = 1;
}
} else if (feature_value < smallest_values[2]) {
position = 2;
} else {
position = 3;
}
} else if (feature_value < smallest_values[5]) {
if (feature_value < smallest_values[4]) {
position = 4;
} else {
position = 5;
}
} else if (feature_value < smallest_values[6]) {
position = 6;
} else {
position = 7;
}
} else if (feature_value < smallest_values[15]) {
if (feature_value < smallest_values[11]) {
if (feature_value < smallest_values[9]) {
if (feature_value < smallest_values[8]) {
position = 8;
} else {
position = 9;
}
} else if (feature_value < smallest_values[10]) {
position = 10;
} else {
position = 11;
}
} else if (feature_value < smallest_values[13]) {
if (feature_value < smallest_values[12]) {
position = 12;
} else {
position = 13;
}
} else if (feature_value < smallest_values[14]) {
position = 14;
} else {
position = 15;
}
}
// If we have detected a new small value, insert it at the correct position
// and shift larger values up.
if (position > -1) {
for (i = 15; i > position; i--) {
smallest_values[i] = smallest_values[i - 1];
age[i] = age[i - 1];
}
smallest_values[position] = feature_value;
age[position] = 1;
}
// Get `current_median`.
if (self->frame_counter > 2) {
current_median = smallest_values[2];
} else if (self->frame_counter > 0) {
current_median = smallest_values[0];
}
// Smooth the median value.
if (self->frame_counter > 0) {
if (current_median < self->mean_value[channel]) {
alpha = kSmoothingDown; // 0.2 in Q15.
} else {
alpha = kSmoothingUp; // 0.99 in Q15.
}
}
tmp32 = (alpha + 1) * self->mean_value[channel];
tmp32 += (WEBRTC_SPL_WORD16_MAX - alpha) * current_median;
tmp32 += 16384;
self->mean_value[channel] = (int16_t) (tmp32 >> 15);
return self->mean_value[channel];
}