104 lines
2.8 KiB
C
104 lines
2.8 KiB
C
/*
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* Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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/*
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* This file contains the function WebRtcSpl_AutoCorrToReflCoef().
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* The description header can be found in signal_processing_library.h
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*
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*/
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#include "common_audio/signal_processing/include/signal_processing_library.h"
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void WebRtcSpl_AutoCorrToReflCoef(const int32_t *R, int use_order, int16_t *K)
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{
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int i, n;
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int16_t tmp;
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const int32_t *rptr;
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int32_t L_num, L_den;
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int16_t *acfptr, *pptr, *wptr, *p1ptr, *w1ptr, ACF[WEBRTC_SPL_MAX_LPC_ORDER],
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P[WEBRTC_SPL_MAX_LPC_ORDER], W[WEBRTC_SPL_MAX_LPC_ORDER];
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// Initialize loop and pointers.
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acfptr = ACF;
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rptr = R;
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pptr = P;
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p1ptr = &P[1];
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w1ptr = &W[1];
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wptr = w1ptr;
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// First loop; n=0. Determine shifting.
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tmp = WebRtcSpl_NormW32(*R);
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*acfptr = (int16_t)((*rptr++ << tmp) >> 16);
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*pptr++ = *acfptr++;
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// Initialize ACF, P and W.
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for (i = 1; i <= use_order; i++)
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{
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*acfptr = (int16_t)((*rptr++ << tmp) >> 16);
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*wptr++ = *acfptr;
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*pptr++ = *acfptr++;
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}
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// Compute reflection coefficients.
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for (n = 1; n <= use_order; n++, K++)
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{
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tmp = WEBRTC_SPL_ABS_W16(*p1ptr);
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if (*P < tmp)
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{
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for (i = n; i <= use_order; i++)
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*K++ = 0;
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return;
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}
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// Division: WebRtcSpl_div(tmp, *P)
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*K = 0;
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if (tmp != 0)
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{
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L_num = tmp;
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L_den = *P;
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i = 15;
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while (i--)
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{
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(*K) <<= 1;
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L_num <<= 1;
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if (L_num >= L_den)
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{
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L_num -= L_den;
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(*K)++;
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}
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}
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if (*p1ptr > 0)
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*K = -*K;
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}
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// Last iteration; don't do Schur recursion.
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if (n == use_order)
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return;
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// Schur recursion.
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pptr = P;
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wptr = w1ptr;
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tmp = (int16_t)(((int32_t)*p1ptr * (int32_t)*K + 16384) >> 15);
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*pptr = WebRtcSpl_AddSatW16(*pptr, tmp);
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pptr++;
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for (i = 1; i <= use_order - n; i++)
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{
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tmp = (int16_t)(((int32_t)*wptr * (int32_t)*K + 16384) >> 15);
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*pptr = WebRtcSpl_AddSatW16(*(pptr + 1), tmp);
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pptr++;
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tmp = (int16_t)(((int32_t)*pptr * (int32_t)*K + 16384) >> 15);
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*wptr = WebRtcSpl_AddSatW16(*wptr, tmp);
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wptr++;
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}
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}
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}
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