Dave Sparks | 56c99cd | 2009-08-24 17:35:45 -0700 | [diff] [blame] | 1 | /*---------------------------------------------------------------------------- |
| 2 | * |
| 3 | * File: |
| 4 | * eas_math.c |
| 5 | * |
| 6 | * Contents and purpose: |
| 7 | * Contains common math routines for the various audio engines. |
| 8 | * |
| 9 | * |
| 10 | * Copyright Sonic Network Inc. 2005 |
The Android Open Source Project | 7df3010 | 2009-03-03 19:30:38 -0800 | [diff] [blame] | 11 | |
| 12 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 13 | * you may not use this file except in compliance with the License. |
| 14 | * You may obtain a copy of the License at |
| 15 | * |
| 16 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 17 | * |
| 18 | * Unless required by applicable law or agreed to in writing, software |
| 19 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 20 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 21 | * See the License for the specific language governing permissions and |
| 22 | * limitations under the License. |
Dave Sparks | 56c99cd | 2009-08-24 17:35:45 -0700 | [diff] [blame] | 23 | * |
| 24 | *---------------------------------------------------------------------------- |
| 25 | * Revision Control: |
| 26 | * $Revision: 586 $ |
| 27 | * $Date: 2007-03-08 20:33:04 -0800 (Thu, 08 Mar 2007) $ |
| 28 | *---------------------------------------------------------------------------- |
| 29 | */ |
| 30 | |
| 31 | #include "eas.h" |
| 32 | #include "eas_math.h" |
| 33 | |
| 34 | /* anything less than this converts to a fraction too small to represent in 32-bits */ |
| 35 | #define MIN_CENTS -18000 |
Marco Nelissen | 699753c | 2020-04-30 19:54:37 -0700 | [diff] [blame] | 36 | /* anything greater than this converts to a fraction too large to represent in 32-bits */ |
| 37 | #define MAX_CENTS 19200 |
Dave Sparks | 56c99cd | 2009-08-24 17:35:45 -0700 | [diff] [blame] | 38 | |
| 39 | /*---------------------------------------------------------------------------- |
| 40 | * EAS_Calculate2toX() |
| 41 | *---------------------------------------------------------------------------- |
| 42 | * Purpose: |
| 43 | * Calculate 2^x |
| 44 | * |
| 45 | * Inputs: |
| 46 | * nCents - measured in cents |
| 47 | * psEASData - pointer to overall EAS data structure |
| 48 | * |
| 49 | * Outputs: |
| 50 | * nResult - int.frac result (where frac has NUM_DENTS_FRAC_BITS) |
| 51 | * |
| 52 | * Side Effects: |
| 53 | * |
| 54 | *---------------------------------------------------------------------------- |
| 55 | */ |
Marco Nelissen | 699753c | 2020-04-30 19:54:37 -0700 | [diff] [blame] | 56 | |
Dave Sparks | 56c99cd | 2009-08-24 17:35:45 -0700 | [diff] [blame] | 57 | EAS_I32 EAS_Calculate2toX (EAS_I32 nCents) |
| 58 | { |
| 59 | EAS_I32 nDents; |
| 60 | EAS_I32 nExponentInt, nExponentFrac; |
| 61 | EAS_I32 nTemp1, nTemp2; |
| 62 | EAS_I32 nResult; |
| 63 | |
| 64 | /* check for minimum value */ |
| 65 | if (nCents < MIN_CENTS) |
| 66 | return 0; |
| 67 | |
Marco Nelissen | 699753c | 2020-04-30 19:54:37 -0700 | [diff] [blame] | 68 | if (nCents > MAX_CENTS) { |
| 69 | nCents = MAX_CENTS; |
| 70 | } |
| 71 | |
Dave Sparks | 56c99cd | 2009-08-24 17:35:45 -0700 | [diff] [blame] | 72 | /* for the time being, convert cents to dents */ |
| 73 | nDents = FMUL_15x15(nCents, CENTS_TO_DENTS); |
| 74 | |
| 75 | nExponentInt = GET_DENTS_INT_PART(nDents); |
| 76 | nExponentFrac = GET_DENTS_FRAC_PART(nDents); |
| 77 | |
| 78 | /* |
| 79 | implement 2^(fracPart) as a power series |
| 80 | */ |
| 81 | nTemp1 = GN2_TO_X2 + MULT_DENTS_COEF(nExponentFrac, GN2_TO_X3); |
| 82 | nTemp2 = GN2_TO_X1 + MULT_DENTS_COEF(nExponentFrac, nTemp1); |
| 83 | nTemp1 = GN2_TO_X0 + MULT_DENTS_COEF(nExponentFrac, nTemp2); |
| 84 | |
| 85 | /* |
| 86 | implement 2^(intPart) as |
| 87 | a left shift for intPart >= 0 or |
| 88 | a left shift for intPart < 0 |
| 89 | */ |
| 90 | if (nExponentInt >= 0) |
| 91 | { |
| 92 | /* left shift for positive exponents */ |
| 93 | /*lint -e{703} <avoid multiply for performance>*/ |
| 94 | nResult = nTemp1 << nExponentInt; |
| 95 | } |
| 96 | else |
| 97 | { |
| 98 | /* right shift for negative exponents */ |
| 99 | nExponentInt = -nExponentInt; |
| 100 | nResult = nTemp1 >> nExponentInt; |
| 101 | } |
| 102 | |
| 103 | return nResult; |
| 104 | } |
| 105 | |
| 106 | /*---------------------------------------------------------------------------- |
| 107 | * EAS_LogToLinear16() |
| 108 | *---------------------------------------------------------------------------- |
| 109 | * Purpose: |
| 110 | * Transform log value to linear gain multiplier using piece-wise linear |
| 111 | * approximation |
| 112 | * |
| 113 | * Inputs: |
| 114 | * nGain - log scale value in 20.10 format. Even though gain is normally |
| 115 | * stored in 6.10 (16-bit) format we use 32-bit numbers here to eliminate |
| 116 | * the need for saturation checking when combining gain values. |
| 117 | * |
| 118 | * Outputs: |
| 119 | * Returns a 16-bit linear value approximately equal to 2^(nGain/1024) |
| 120 | * |
| 121 | * Side Effects: |
| 122 | * |
| 123 | *---------------------------------------------------------------------------- |
| 124 | */ |
| 125 | EAS_U16 EAS_LogToLinear16 (EAS_I32 nGain) |
| 126 | { |
| 127 | EAS_INT nExp; |
| 128 | EAS_U16 nTemp; |
| 129 | |
| 130 | /* bias to positive */ |
| 131 | nGain += 32767; |
| 132 | |
| 133 | /* check for infinite attenuation */ |
| 134 | if (nGain < 0) |
| 135 | return 0; |
| 136 | |
| 137 | /* extract the exponent */ |
| 138 | nExp = 31 - (nGain >> 10); |
| 139 | |
| 140 | /* check for maximum output */ |
| 141 | if (nExp < 0) |
| 142 | return 0x7fff; |
| 143 | |
| 144 | /* extract mantissa and restore implied 1 bit */ |
| 145 | nTemp = (EAS_U16)((((nGain & 0x3ff) << 4) | 0x4000) >> nExp); |
| 146 | |
| 147 | /* use shift to approximate power-of-2 operation */ |
| 148 | return nTemp; |
| 149 | } |
| 150 | |
| 151 | /*---------------------------------------------------------------------------- |
| 152 | * EAS_VolumeToGain() |
| 153 | *---------------------------------------------------------------------------- |
| 154 | * Purpose: |
| 155 | * Transform volume control in 1dB increments to gain multiplier |
| 156 | * |
| 157 | * Inputs: |
| 158 | * volume - 100 = 0dB, 99 = -1dB, 0 = -inf |
| 159 | * |
| 160 | * Outputs: |
| 161 | * Returns a 16-bit linear value |
| 162 | *---------------------------------------------------------------------------- |
| 163 | */ |
| 164 | EAS_I16 EAS_VolumeToGain (EAS_INT volume) |
| 165 | { |
| 166 | /* check for limits */ |
| 167 | if (volume <= 0) |
| 168 | return 0; |
| 169 | if (volume >= 100) |
| 170 | return 0x7fff; |
| 171 | |
| 172 | /*lint -e{702} use shift instead of division */ |
| 173 | return (EAS_I16) EAS_Calculate2toX((((volume - EAS_MAX_VOLUME) * 204099) >> 10) - 1); |
| 174 | } |
| 175 | |