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_AutoCorrelation().
14 * The description header can be found in signal_processing_library.h
15 *
16 */
17
18 #include "signal_processing_library.h"
19
WebRtcSpl_AutoCorrelation(G_CONST WebRtc_Word16 * in_vector,int in_vector_length,int order,WebRtc_Word32 * result,int * scale)20 int WebRtcSpl_AutoCorrelation(G_CONST WebRtc_Word16* in_vector,
21 int in_vector_length,
22 int order,
23 WebRtc_Word32* result,
24 int* scale)
25 {
26 WebRtc_Word32 sum;
27 int i, j;
28 WebRtc_Word16 smax; // Sample max
29 G_CONST WebRtc_Word16* xptr1;
30 G_CONST WebRtc_Word16* xptr2;
31 WebRtc_Word32* resultptr;
32 int scaling = 0;
33
34 #ifdef _ARM_OPT_
35 #pragma message("NOTE: _ARM_OPT_ optimizations are used")
36 WebRtc_Word16 loops4;
37 #endif
38
39 if (order < 0)
40 order = in_vector_length;
41
42 // Find the max. sample
43 smax = WebRtcSpl_MaxAbsValueW16(in_vector, in_vector_length);
44
45 // In order to avoid overflow when computing the sum we should scale the samples so that
46 // (in_vector_length * smax * smax) will not overflow.
47
48 if (smax == 0)
49 {
50 scaling = 0;
51 } else
52 {
53 int nbits = WebRtcSpl_GetSizeInBits(in_vector_length); // # of bits in the sum loop
54 int t = WebRtcSpl_NormW32(WEBRTC_SPL_MUL(smax, smax)); // # of bits to normalize smax
55
56 if (t > nbits)
57 {
58 scaling = 0;
59 } else
60 {
61 scaling = nbits - t;
62 }
63
64 }
65
66 resultptr = result;
67
68 // Perform the actual correlation calculation
69 for (i = 0; i < order + 1; i++)
70 {
71 int loops = (in_vector_length - i);
72 sum = 0;
73 xptr1 = in_vector;
74 xptr2 = &in_vector[i];
75 #ifndef _ARM_OPT_
76 for (j = loops; j > 0; j--)
77 {
78 sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1++, *xptr2++, scaling);
79 }
80 #else
81 loops4 = (loops >> 2) << 2;
82
83 if (scaling == 0)
84 {
85 for (j = 0; j < loops4; j = j + 4)
86 {
87 sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
88 xptr1++;
89 xptr2++;
90 sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
91 xptr1++;
92 xptr2++;
93 sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
94 xptr1++;
95 xptr2++;
96 sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
97 xptr1++;
98 xptr2++;
99 }
100
101 for (j = loops4; j < loops; j++)
102 {
103 sum += WEBRTC_SPL_MUL_16_16(*xptr1, *xptr2);
104 xptr1++;
105 xptr2++;
106 }
107 }
108 else
109 {
110 for (j = 0; j < loops4; j = j + 4)
111 {
112 sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
113 xptr1++;
114 xptr2++;
115 sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
116 xptr1++;
117 xptr2++;
118 sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
119 xptr1++;
120 xptr2++;
121 sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
122 xptr1++;
123 xptr2++;
124 }
125
126 for (j = loops4; j < loops; j++)
127 {
128 sum += WEBRTC_SPL_MUL_16_16_RSFT(*xptr1, *xptr2, scaling);
129 xptr1++;
130 xptr2++;
131 }
132 }
133
134 #endif
135 *resultptr++ = sum;
136 }
137
138 *scale = scaling;
139
140 return order + 1;
141 }
142