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 19#include <assert.h> 20 21#include <android/log.h> 22 23#include "EffectsMath.h" 24 25// 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) 26// 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) 27// It is used for a better than piece wise approximation of lin to log2 conversion 28 29static const uint16_t gLogTab[] = 30{ 31 0, 733, 1455, 2166, 32 2866, 3556, 4236, 4907, 33 5568, 6220, 6863, 7498, 34 8124, 8742, 9352, 9954, 35 10549, 11136, 11716, 12289, 36 12855, 13415, 13968, 14514, 37 15055, 15589, 16117, 16639, 38 17156, 17667, 18173, 18673, 39 19168, 19658, 20143, 20623, 40 21098, 21568, 22034, 22495, 41 22952, 23404, 23852, 24296, 42 24736, 25172, 25604, 26031, 43 26455, 26876, 27292, 27705, 44 28114, 28520, 28922, 29321, 45 29717, 30109, 30498, 30884, 46 31267, 31647, 32024, 32397, 47 32768 48}; 49 50int32_t Effects_log2(uint32_t x) { 51 int32_t exp = 31 - __builtin_clz(x); 52 uint32_t segStart = x >> (exp - 6); 53 uint32_t i = segStart & 0x3F; 54 int32_t log = (int32_t)gLogTab[i]; 55 int32_t logEnd = (int32_t)gLogTab[i+1]; 56 segStart <<= exp - 6; 57 58 return (exp << 15) + log + (((x - segStart) * (logEnd - log)) >> (exp - 6)); 59} 60 61// gExpTab[i] = (2^(i>>6)) << 22 62static const uint32_t gExpTab[] = { 63 4194304, 4239977, 4286147, 4332820, 64 4380002, 4427697, 4475911, 4524651, 65 4573921, 4623728, 4674077, 4724974, 66 4776426, 4828438, 4881016, 4934167, 67 4987896, 5042211, 5097117, 5152621, 68 5208729, 5265449, 5322786, 5380747, 69 5439339, 5498570, 5558445, 5618973, 70 5680159, 5742012, 5804539, 5867746, 71 5931642, 5996233, 6061528, 6127533, 72 6194258, 6261709, 6329894, 6398822, 73 6468501, 6538938, 6610143, 6682122, 74 6754886, 6828442, 6902799, 6977965, 75 7053950, 7130763, 7208412, 7286906, 76 7366255, 7446469, 7527555, 7609525, 77 7692387, 7776152, 7860829, 7946428, 78 8032959, 8120432, 8208857, 8298246, 79 8388608 80}; 81 82 83uint32_t Effects_exp2(int32_t x) { 84 int32_t i = x >> 15; 85 assert(i < 32); 86 x &= (1 << 15) - 1; 87 int32_t j = x >> 9; 88 x &= (1 << 9) - 1; 89 uint32_t exp = gExpTab[j]; 90 uint32_t expEnd = gExpTab[j+1]; 91 92 return ((exp << 9) + (expEnd - exp) * x) >> (31 - i); 93} 94 95 96int16_t Effects_MillibelsToLinear16 (int32_t nGain) 97{ 98 nGain = ((nGain + MB_TO_LIN_K1) << 15 ) / MB_TO_LIN_K2; 99 uint32_t exp2 = Effects_exp2(nGain); 100 101 if (exp2 > 32767) exp2 = 32767; 102 103 return (int16_t)exp2; 104} 105 106 107int16_t Effects_Linear16ToMillibels (int32_t nGain) 108{ 109 return (int16_t)(((MB_TO_LIN_K2*Effects_log2(nGain))>>15)-MB_TO_LIN_K1); 110} 111 112 113int32_t Effects_Sqrt(int32_t in) 114{ 115 int32_t tmp; 116 int32_t out = 0; 117 int32_t i; 118 int32_t j; 119 120 121 if (in == 0) return 0; 122 123 if (in >= 0x10000000) 124 { 125 out = 0x4000; 126 in -= 0x10000000; 127 } 128 129 j = 32 - __builtin_clz(in); 130 131 if (j & 1) j++; 132 j >>= 1; 133 134 for (i = j; i > 0; i--) { 135 tmp = (out << i) + (1 << ((i - 1)*2)); 136 if (in >= tmp) 137 { 138 out += 1 << (i-1); 139 in -= tmp; 140 } 141 } 142 143 return out; 144} 145 146