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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_AutoCorrToReflCoef().
* The description header can be found in signal_processing_library.h
*
*/
#include "signal_processing_library.h"
void WebRtcSpl_AutoCorrToReflCoef(G_CONST WebRtc_Word32 *R, int use_order, WebRtc_Word16 *K)
{
int i, n;
WebRtc_Word16 tmp;
G_CONST WebRtc_Word32 *rptr;
WebRtc_Word32 L_num, L_den;
WebRtc_Word16 *acfptr, *pptr, *wptr, *p1ptr, *w1ptr, ACF[WEBRTC_SPL_MAX_LPC_ORDER],
P[WEBRTC_SPL_MAX_LPC_ORDER], W[WEBRTC_SPL_MAX_LPC_ORDER];
// Initialize loop and pointers.
acfptr = ACF;
rptr = R;
pptr = P;
p1ptr = &P[1];
w1ptr = &W[1];
wptr = w1ptr;
// First loop; n=0. Determine shifting.
tmp = WebRtcSpl_NormW32(*R);
*acfptr = (WebRtc_Word16)((*rptr++ << tmp) >> 16);
*pptr++ = *acfptr++;
// Initialize ACF, P and W.
for (i = 1; i <= use_order; i++)
{
*acfptr = (WebRtc_Word16)((*rptr++ << tmp) >> 16);
*wptr++ = *acfptr;
*pptr++ = *acfptr++;
}
// Compute reflection coefficients.
for (n = 1; n <= use_order; n++, K++)
{
tmp = WEBRTC_SPL_ABS_W16(*p1ptr);
if (*P < tmp)
{
for (i = n; i <= use_order; i++)
*K++ = 0;
return;
}
// Division: WebRtcSpl_div(tmp, *P)
*K = 0;
if (tmp != 0)
{
L_num = tmp;
L_den = *P;
i = 15;
while (i--)
{
(*K) <<= 1;
L_num <<= 1;
if (L_num >= L_den)
{
L_num -= L_den;
(*K)++;
}
}
if (*p1ptr > 0)
*K = -*K;
}
// Last iteration; don't do Schur recursion.
if (n == use_order)
return;
// Schur recursion.
pptr = P;
wptr = w1ptr;
tmp = (WebRtc_Word16)(((WebRtc_Word32)*p1ptr * (WebRtc_Word32)*K + 16384) >> 15);
*pptr = WEBRTC_SPL_ADD_SAT_W16( *pptr, tmp );
pptr++;
for (i = 1; i <= use_order - n; i++)
{
tmp = (WebRtc_Word16)(((WebRtc_Word32)*wptr * (WebRtc_Word32)*K + 16384) >> 15);
*pptr = WEBRTC_SPL_ADD_SAT_W16( *(pptr+1), tmp );
pptr++;
tmp = (WebRtc_Word16)(((WebRtc_Word32)*pptr * (WebRtc_Word32)*K + 16384) >> 15);
*wptr = WEBRTC_SPL_ADD_SAT_W16( *wptr, tmp );
wptr++;
}
}
}
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