| /* |
| * 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++; |
| } |
| } |
| } |