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 implementations of the divisions
14 * WebRtcSpl_DivU32U16()
15 * WebRtcSpl_DivW32W16()
16 * WebRtcSpl_DivW32W16ResW16()
17 * WebRtcSpl_DivResultInQ31()
18 * WebRtcSpl_DivW32HiLow()
19 *
20 * The description header can be found in signal_processing_library.h
21 *
22 */
23
24 #include "signal_processing_library.h"
25
WebRtcSpl_DivU32U16(WebRtc_UWord32 num,WebRtc_UWord16 den)26 WebRtc_UWord32 WebRtcSpl_DivU32U16(WebRtc_UWord32 num, WebRtc_UWord16 den)
27 {
28 // Guard against division with 0
29 if (den != 0)
30 {
31 return (WebRtc_UWord32)(num / den);
32 } else
33 {
34 return (WebRtc_UWord32)0xFFFFFFFF;
35 }
36 }
37
WebRtcSpl_DivW32W16(WebRtc_Word32 num,WebRtc_Word16 den)38 WebRtc_Word32 WebRtcSpl_DivW32W16(WebRtc_Word32 num, WebRtc_Word16 den)
39 {
40 // Guard against division with 0
41 if (den != 0)
42 {
43 return (WebRtc_Word32)(num / den);
44 } else
45 {
46 return (WebRtc_Word32)0x7FFFFFFF;
47 }
48 }
49
WebRtcSpl_DivW32W16ResW16(WebRtc_Word32 num,WebRtc_Word16 den)50 WebRtc_Word16 WebRtcSpl_DivW32W16ResW16(WebRtc_Word32 num, WebRtc_Word16 den)
51 {
52 // Guard against division with 0
53 if (den != 0)
54 {
55 return (WebRtc_Word16)(num / den);
56 } else
57 {
58 return (WebRtc_Word16)0x7FFF;
59 }
60 }
61
WebRtcSpl_DivResultInQ31(WebRtc_Word32 num,WebRtc_Word32 den)62 WebRtc_Word32 WebRtcSpl_DivResultInQ31(WebRtc_Word32 num, WebRtc_Word32 den)
63 {
64 WebRtc_Word32 L_num = num;
65 WebRtc_Word32 L_den = den;
66 WebRtc_Word32 div = 0;
67 int k = 31;
68 int change_sign = 0;
69
70 if (num == 0)
71 return 0;
72
73 if (num < 0)
74 {
75 change_sign++;
76 L_num = -num;
77 }
78 if (den < 0)
79 {
80 change_sign++;
81 L_den = -den;
82 }
83 while (k--)
84 {
85 div <<= 1;
86 L_num <<= 1;
87 if (L_num >= L_den)
88 {
89 L_num -= L_den;
90 div++;
91 }
92 }
93 if (change_sign == 1)
94 {
95 div = -div;
96 }
97 return div;
98 }
99
WebRtcSpl_DivW32HiLow(WebRtc_Word32 num,WebRtc_Word16 den_hi,WebRtc_Word16 den_low)100 WebRtc_Word32 WebRtcSpl_DivW32HiLow(WebRtc_Word32 num, WebRtc_Word16 den_hi,
101 WebRtc_Word16 den_low)
102 {
103 WebRtc_Word16 approx, tmp_hi, tmp_low, num_hi, num_low;
104 WebRtc_Word32 tmpW32;
105
106 approx = (WebRtc_Word16)WebRtcSpl_DivW32W16((WebRtc_Word32)0x1FFFFFFF, den_hi);
107 // result in Q14 (Note: 3FFFFFFF = 0.5 in Q30)
108
109 // tmpW32 = 1/den = approx * (2.0 - den * approx) (in Q30)
110 tmpW32 = (WEBRTC_SPL_MUL_16_16(den_hi, approx) << 1)
111 + ((WEBRTC_SPL_MUL_16_16(den_low, approx) >> 15) << 1);
112 // tmpW32 = den * approx
113
114 tmpW32 = (WebRtc_Word32)0x7fffffffL - tmpW32; // result in Q30 (tmpW32 = 2.0-(den*approx))
115
116 // Store tmpW32 in hi and low format
117 tmp_hi = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32(tmpW32, 16);
118 tmp_low = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32((tmpW32
119 - WEBRTC_SPL_LSHIFT_W32((WebRtc_Word32)tmp_hi, 16)), 1);
120
121 // tmpW32 = 1/den in Q29
122 tmpW32 = ((WEBRTC_SPL_MUL_16_16(tmp_hi, approx) + (WEBRTC_SPL_MUL_16_16(tmp_low, approx)
123 >> 15)) << 1);
124
125 // 1/den in hi and low format
126 tmp_hi = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32(tmpW32, 16);
127 tmp_low = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32((tmpW32
128 - WEBRTC_SPL_LSHIFT_W32((WebRtc_Word32)tmp_hi, 16)), 1);
129
130 // Store num in hi and low format
131 num_hi = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32(num, 16);
132 num_low = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32((num
133 - WEBRTC_SPL_LSHIFT_W32((WebRtc_Word32)num_hi, 16)), 1);
134
135 // num * (1/den) by 32 bit multiplication (result in Q28)
136
137 tmpW32 = (WEBRTC_SPL_MUL_16_16(num_hi, tmp_hi) + (WEBRTC_SPL_MUL_16_16(num_hi, tmp_low)
138 >> 15) + (WEBRTC_SPL_MUL_16_16(num_low, tmp_hi) >> 15));
139
140 // Put result in Q31 (convert from Q28)
141 tmpW32 = WEBRTC_SPL_LSHIFT_W32(tmpW32, 3);
142
143 return tmpW32;
144 }
145