1 /*
2 * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11
12 /*
13 * This file contains the function WebRtcSpl_AutoCorrToReflCoef().
14 * The description header can be found in signal_processing_library.h
15 *
16 */
17
18 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
19
WebRtcSpl_AutoCorrToReflCoef(const int32_t * R,int use_order,int16_t * K)20 void WebRtcSpl_AutoCorrToReflCoef(const int32_t *R, int use_order, int16_t *K)
21 {
22 int i, n;
23 int16_t tmp;
24 const int32_t *rptr;
25 int32_t L_num, L_den;
26 int16_t *acfptr, *pptr, *wptr, *p1ptr, *w1ptr, ACF[WEBRTC_SPL_MAX_LPC_ORDER],
27 P[WEBRTC_SPL_MAX_LPC_ORDER], W[WEBRTC_SPL_MAX_LPC_ORDER];
28
29 // Initialize loop and pointers.
30 acfptr = ACF;
31 rptr = R;
32 pptr = P;
33 p1ptr = &P[1];
34 w1ptr = &W[1];
35 wptr = w1ptr;
36
37 // First loop; n=0. Determine shifting.
38 tmp = WebRtcSpl_NormW32(*R);
39 *acfptr = (int16_t)((*rptr++ << tmp) >> 16);
40 *pptr++ = *acfptr++;
41
42 // Initialize ACF, P and W.
43 for (i = 1; i <= use_order; i++)
44 {
45 *acfptr = (int16_t)((*rptr++ << tmp) >> 16);
46 *wptr++ = *acfptr;
47 *pptr++ = *acfptr++;
48 }
49
50 // Compute reflection coefficients.
51 for (n = 1; n <= use_order; n++, K++)
52 {
53 tmp = WEBRTC_SPL_ABS_W16(*p1ptr);
54 if (*P < tmp)
55 {
56 for (i = n; i <= use_order; i++)
57 *K++ = 0;
58
59 return;
60 }
61
62 // Division: WebRtcSpl_div(tmp, *P)
63 *K = 0;
64 if (tmp != 0)
65 {
66 L_num = tmp;
67 L_den = *P;
68 i = 15;
69 while (i--)
70 {
71 (*K) <<= 1;
72 L_num <<= 1;
73 if (L_num >= L_den)
74 {
75 L_num -= L_den;
76 (*K)++;
77 }
78 }
79 if (*p1ptr > 0)
80 *K = -*K;
81 }
82
83 // Last iteration; don't do Schur recursion.
84 if (n == use_order)
85 return;
86
87 // Schur recursion.
88 pptr = P;
89 wptr = w1ptr;
90 tmp = (int16_t)(((int32_t)*p1ptr * (int32_t)*K + 16384) >> 15);
91 *pptr = WebRtcSpl_AddSatW16(*pptr, tmp);
92 pptr++;
93 for (i = 1; i <= use_order - n; i++)
94 {
95 tmp = (int16_t)(((int32_t)*wptr * (int32_t)*K + 16384) >> 15);
96 *pptr = WebRtcSpl_AddSatW16(*(pptr + 1), tmp);
97 pptr++;
98 tmp = (int16_t)(((int32_t)*pptr * (int32_t)*K + 16384) >> 15);
99 *wptr = WebRtcSpl_AddSatW16(*wptr, tmp);
100 wptr++;
101 }
102 }
103 }
104