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/*
* Copyright (c) 2011 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.
*/
/*
* This file contains the function WebRtcSpl_FilterAR().
* The description header can be found in signal_processing_library.h
*
*/
#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
size_t WebRtcSpl_FilterAR(const int16_t* a,
size_t a_length,
const int16_t* x,
size_t x_length,
int16_t* state,
size_t state_length,
int16_t* state_low,
size_t state_low_length,
int16_t* filtered,
int16_t* filtered_low,
size_t filtered_low_length)
{
int32_t o;
int32_t oLOW;
size_t i, j, stop;
const int16_t* x_ptr = &x[0];
int16_t* filteredFINAL_ptr = filtered;
int16_t* filteredFINAL_LOW_ptr = filtered_low;
for (i = 0; i < x_length; i++)
{
// Calculate filtered[i] and filtered_low[i]
const int16_t* a_ptr = &a[1];
int16_t* filtered_ptr = &filtered[i - 1];
int16_t* filtered_low_ptr = &filtered_low[i - 1];
int16_t* state_ptr = &state[state_length - 1];
int16_t* state_low_ptr = &state_low[state_length - 1];
o = (int32_t)(*x_ptr++) << 12;
oLOW = (int32_t)0;
stop = (i < a_length) ? i + 1 : a_length;
for (j = 1; j < stop; j++)
{
o -= *a_ptr * *filtered_ptr--;
oLOW -= *a_ptr++ * *filtered_low_ptr--;
}
for (j = i + 1; j < a_length; j++)
{
o -= *a_ptr * *state_ptr--;
oLOW -= *a_ptr++ * *state_low_ptr--;
}
o += (oLOW >> 12);
*filteredFINAL_ptr = (int16_t)((o + (int32_t)2048) >> 12);
*filteredFINAL_LOW_ptr++ = (int16_t)(o - ((int32_t)(*filteredFINAL_ptr++)
<< 12));
}
// Save the filter state
if (x_length >= state_length)
{
WebRtcSpl_CopyFromEndW16(filtered, x_length, a_length - 1, state);
WebRtcSpl_CopyFromEndW16(filtered_low, x_length, a_length - 1, state_low);
} else
{
for (i = 0; i < state_length - x_length; i++)
{
state[i] = state[i + x_length];
state_low[i] = state_low[i + x_length];
}
for (i = 0; i < x_length; i++)
{
state[state_length - x_length + i] = filtered[i];
state[state_length - x_length + i] = filtered_low[i];
}
}
return x_length;
}
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