1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 #define LOG_TAG "EFFECTSMATH"
17 //#define LOG_NDEBUG 0
18 #include <cutils/log.h>
19 #include <assert.h>
20
21 #include "EffectsMath.h"
22
23 // gLogTab contains pre-calculated values of log2(1 + ai5*2^-1 + ai4*2^-2 + ai3*2^-3 + ai2*2^-4 + ai1*2^-5 + ai0*2^-6)
24 // for integers in the range 0 to 63 (i = ai5*2^5 + ai4*2^4 + ai3*2^3 + ai2*2^2 + ai1*2^1 + ai0*2^0)
25 // It is used for a better than piece wise approximation of lin to log2 conversion
26
27 static const uint16_t gLogTab[] =
28 {
29 0, 733, 1455, 2166,
30 2866, 3556, 4236, 4907,
31 5568, 6220, 6863, 7498,
32 8124, 8742, 9352, 9954,
33 10549, 11136, 11716, 12289,
34 12855, 13415, 13968, 14514,
35 15055, 15589, 16117, 16639,
36 17156, 17667, 18173, 18673,
37 19168, 19658, 20143, 20623,
38 21098, 21568, 22034, 22495,
39 22952, 23404, 23852, 24296,
40 24736, 25172, 25604, 26031,
41 26455, 26876, 27292, 27705,
42 28114, 28520, 28922, 29321,
43 29717, 30109, 30498, 30884,
44 31267, 31647, 32024, 32397,
45 32768
46 };
47
Effects_log2(uint32_t x)48 int32_t Effects_log2(uint32_t x) {
49 int32_t exp = 31 - __builtin_clz(x);
50 uint32_t segStart = x >> (exp - 6);
51 uint32_t i = segStart & 0x3F;
52 int32_t log = (int32_t)gLogTab[i];
53 int32_t logEnd = (int32_t)gLogTab[i+1];
54 segStart <<= exp - 6;
55
56 return (exp << 15) + log + (((x - segStart) * (logEnd - log)) >> (exp - 6));
57 }
58
59 // gExpTab[i] = (2^(i>>6)) << 22
60 static const uint32_t gExpTab[] = {
61 4194304, 4239977, 4286147, 4332820,
62 4380002, 4427697, 4475911, 4524651,
63 4573921, 4623728, 4674077, 4724974,
64 4776426, 4828438, 4881016, 4934167,
65 4987896, 5042211, 5097117, 5152621,
66 5208729, 5265449, 5322786, 5380747,
67 5439339, 5498570, 5558445, 5618973,
68 5680159, 5742012, 5804539, 5867746,
69 5931642, 5996233, 6061528, 6127533,
70 6194258, 6261709, 6329894, 6398822,
71 6468501, 6538938, 6610143, 6682122,
72 6754886, 6828442, 6902799, 6977965,
73 7053950, 7130763, 7208412, 7286906,
74 7366255, 7446469, 7527555, 7609525,
75 7692387, 7776152, 7860829, 7946428,
76 8032959, 8120432, 8208857, 8298246,
77 8388608
78 };
79
80
Effects_exp2(int32_t x)81 uint32_t Effects_exp2(int32_t x) {
82 int32_t i = x >> 15;
83 assert(i < 32);
84 x &= (1 << 15) - 1;
85 int32_t j = x >> 9;
86 x &= (1 << 9) - 1;
87 uint32_t exp = gExpTab[j];
88 uint32_t expEnd = gExpTab[j+1];
89
90 return ((exp << 9) + (expEnd - exp) * x) >> (31 - i);
91 }
92
93
Effects_MillibelsToLinear16(int32_t nGain)94 int16_t Effects_MillibelsToLinear16 (int32_t nGain)
95 {
96 nGain = ((nGain + MB_TO_LIN_K1) << 15 ) / MB_TO_LIN_K2;
97 uint32_t exp2 = Effects_exp2(nGain);
98
99 if (exp2 > 32767) exp2 = 32767;
100
101 return (int16_t)exp2;
102 }
103
104
Effects_Linear16ToMillibels(int32_t nGain)105 int16_t Effects_Linear16ToMillibels (int32_t nGain)
106 {
107 return (int16_t)(((MB_TO_LIN_K2*Effects_log2(nGain))>>15)-MB_TO_LIN_K1);
108 }
109
110
Effects_Sqrt(int32_t in)111 int32_t Effects_Sqrt(int32_t in)
112 {
113 int32_t tmp;
114 int32_t out = 0;
115 int32_t i;
116 int32_t j;
117
118
119 if (in == 0) return 0;
120
121 if (in >= 0x10000000)
122 {
123 out = 0x4000;
124 in -= 0x10000000;
125 }
126
127 j = 32 - __builtin_clz(in);
128
129 if (j & 1) j++;
130 j >>= 1;
131
132 for (i = j; i > 0; i--) {
133 tmp = (out << i) + (1 << ((i - 1)*2));
134 if (in >= tmp)
135 {
136 out += 1 << (i-1);
137 in -= tmp;
138 }
139 }
140
141 return out;
142 }
143
144