Karsten Keil | 3712b42 | 2008-07-27 02:02:10 +0200 | [diff] [blame] | 1 | /* |
| 2 | |
| 3 | * l1oip_codec.c generic codec using lookup table |
| 4 | * -> conversion from a-Law to u-Law |
| 5 | * -> conversion from u-Law to a-Law |
| 6 | * -> compression by reducing the number of sample resolution to 4 |
| 7 | * |
| 8 | * NOTE: It is not compatible with any standard codec like ADPCM. |
| 9 | * |
| 10 | * Author Andreas Eversberg (jolly@eversberg.eu) |
| 11 | * |
| 12 | * This program is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU General Public License as published by |
| 14 | * the Free Software Foundation; either version 2, or (at your option) |
| 15 | * any later version. |
| 16 | * |
| 17 | * This program is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License |
| 23 | * along with this program; if not, write to the Free Software |
| 24 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
| 25 | |
| 26 | */ |
| 27 | |
| 28 | /* |
| 29 | |
| 30 | How the codec works: |
| 31 | -------------------- |
| 32 | |
| 33 | The volume is increased to increase the dynamic range of the audio signal. |
| 34 | Each sample is converted to a-LAW with only 16 steps of level resolution. |
| 35 | A pair of two samples are stored in one byte. |
| 36 | |
| 37 | The first byte is stored in the upper bits, the second byte is stored in the |
| 38 | lower bits. |
| 39 | |
| 40 | To speed up compression and decompression, two lookup tables are formed: |
| 41 | |
| 42 | - 16 bits index for two samples (law encoded) with 8 bit compressed result. |
| 43 | - 8 bits index for one compressed data with 16 bits decompressed result. |
| 44 | |
| 45 | NOTE: The bytes are handled as they are law-encoded. |
| 46 | |
| 47 | */ |
| 48 | |
| 49 | #include <linux/vmalloc.h> |
| 50 | #include <linux/mISDNif.h> |
Andreas Eversberg | a5355c2 | 2009-05-22 11:04:45 +0000 | [diff] [blame] | 51 | #include <linux/in.h> |
Karsten Keil | 3712b42 | 2008-07-27 02:02:10 +0200 | [diff] [blame] | 52 | #include "core.h" |
Hannes Eder | 5b83435 | 2008-12-12 21:15:17 -0800 | [diff] [blame] | 53 | #include "l1oip.h" |
Karsten Keil | 3712b42 | 2008-07-27 02:02:10 +0200 | [diff] [blame] | 54 | |
| 55 | /* definitions of codec. don't use calculations, code may run slower. */ |
| 56 | |
| 57 | static u8 *table_com; |
| 58 | static u16 *table_dec; |
| 59 | |
| 60 | |
| 61 | /* alaw -> ulaw */ |
| 62 | static u8 alaw_to_ulaw[256] = |
| 63 | { |
| 64 | 0xab, 0x2b, 0xe3, 0x63, 0x8b, 0x0b, 0xc9, 0x49, |
| 65 | 0xba, 0x3a, 0xf6, 0x76, 0x9b, 0x1b, 0xd7, 0x57, |
| 66 | 0xa3, 0x23, 0xdd, 0x5d, 0x83, 0x03, 0xc1, 0x41, |
| 67 | 0xb2, 0x32, 0xeb, 0x6b, 0x93, 0x13, 0xcf, 0x4f, |
| 68 | 0xaf, 0x2f, 0xe7, 0x67, 0x8f, 0x0f, 0xcd, 0x4d, |
| 69 | 0xbe, 0x3e, 0xfe, 0x7e, 0x9f, 0x1f, 0xdb, 0x5b, |
| 70 | 0xa7, 0x27, 0xdf, 0x5f, 0x87, 0x07, 0xc5, 0x45, |
| 71 | 0xb6, 0x36, 0xef, 0x6f, 0x97, 0x17, 0xd3, 0x53, |
| 72 | 0xa9, 0x29, 0xe1, 0x61, 0x89, 0x09, 0xc7, 0x47, |
| 73 | 0xb8, 0x38, 0xf2, 0x72, 0x99, 0x19, 0xd5, 0x55, |
| 74 | 0xa1, 0x21, 0xdc, 0x5c, 0x81, 0x01, 0xbf, 0x3f, |
| 75 | 0xb0, 0x30, 0xe9, 0x69, 0x91, 0x11, 0xce, 0x4e, |
| 76 | 0xad, 0x2d, 0xe5, 0x65, 0x8d, 0x0d, 0xcb, 0x4b, |
| 77 | 0xbc, 0x3c, 0xfa, 0x7a, 0x9d, 0x1d, 0xd9, 0x59, |
| 78 | 0xa5, 0x25, 0xde, 0x5e, 0x85, 0x05, 0xc3, 0x43, |
| 79 | 0xb4, 0x34, 0xed, 0x6d, 0x95, 0x15, 0xd1, 0x51, |
| 80 | 0xac, 0x2c, 0xe4, 0x64, 0x8c, 0x0c, 0xca, 0x4a, |
| 81 | 0xbb, 0x3b, 0xf8, 0x78, 0x9c, 0x1c, 0xd8, 0x58, |
| 82 | 0xa4, 0x24, 0xde, 0x5e, 0x84, 0x04, 0xc2, 0x42, |
| 83 | 0xb3, 0x33, 0xec, 0x6c, 0x94, 0x14, 0xd0, 0x50, |
| 84 | 0xb0, 0x30, 0xe8, 0x68, 0x90, 0x10, 0xce, 0x4e, |
| 85 | 0xbf, 0x3f, 0xfe, 0x7e, 0xa0, 0x20, 0xdc, 0x5c, |
| 86 | 0xa8, 0x28, 0xe0, 0x60, 0x88, 0x08, 0xc6, 0x46, |
| 87 | 0xb7, 0x37, 0xf0, 0x70, 0x98, 0x18, 0xd4, 0x54, |
| 88 | 0xaa, 0x2a, 0xe2, 0x62, 0x8a, 0x0a, 0xc8, 0x48, |
| 89 | 0xb9, 0x39, 0xf4, 0x74, 0x9a, 0x1a, 0xd6, 0x56, |
| 90 | 0xa2, 0x22, 0xdd, 0x5d, 0x82, 0x02, 0xc0, 0x40, |
| 91 | 0xb1, 0x31, 0xea, 0x6a, 0x92, 0x12, 0xcf, 0x4f, |
| 92 | 0xae, 0x2e, 0xe6, 0x66, 0x8e, 0x0e, 0xcc, 0x4c, |
| 93 | 0xbd, 0x3d, 0xfc, 0x7c, 0x9e, 0x1e, 0xda, 0x5a, |
| 94 | 0xa6, 0x26, 0xdf, 0x5f, 0x86, 0x06, 0xc4, 0x44, |
| 95 | 0xb5, 0x35, 0xee, 0x6e, 0x96, 0x16, 0xd2, 0x52 |
| 96 | }; |
| 97 | |
| 98 | /* ulaw -> alaw */ |
| 99 | static u8 ulaw_to_alaw[256] = |
| 100 | { |
| 101 | 0xab, 0x55, 0xd5, 0x15, 0x95, 0x75, 0xf5, 0x35, |
| 102 | 0xb5, 0x45, 0xc5, 0x05, 0x85, 0x65, 0xe5, 0x25, |
| 103 | 0xa5, 0x5d, 0xdd, 0x1d, 0x9d, 0x7d, 0xfd, 0x3d, |
| 104 | 0xbd, 0x4d, 0xcd, 0x0d, 0x8d, 0x6d, 0xed, 0x2d, |
| 105 | 0xad, 0x51, 0xd1, 0x11, 0x91, 0x71, 0xf1, 0x31, |
| 106 | 0xb1, 0x41, 0xc1, 0x01, 0x81, 0x61, 0xe1, 0x21, |
| 107 | 0x59, 0xd9, 0x19, 0x99, 0x79, 0xf9, 0x39, 0xb9, |
| 108 | 0x49, 0xc9, 0x09, 0x89, 0x69, 0xe9, 0x29, 0xa9, |
| 109 | 0xd7, 0x17, 0x97, 0x77, 0xf7, 0x37, 0xb7, 0x47, |
| 110 | 0xc7, 0x07, 0x87, 0x67, 0xe7, 0x27, 0xa7, 0xdf, |
| 111 | 0x9f, 0x7f, 0xff, 0x3f, 0xbf, 0x4f, 0xcf, 0x0f, |
| 112 | 0x8f, 0x6f, 0xef, 0x2f, 0x53, 0x13, 0x73, 0x33, |
| 113 | 0xb3, 0x43, 0xc3, 0x03, 0x83, 0x63, 0xe3, 0x23, |
| 114 | 0xa3, 0x5b, 0xdb, 0x1b, 0x9b, 0x7b, 0xfb, 0x3b, |
| 115 | 0xbb, 0xbb, 0x4b, 0x4b, 0xcb, 0xcb, 0x0b, 0x0b, |
| 116 | 0x8b, 0x8b, 0x6b, 0x6b, 0xeb, 0xeb, 0x2b, 0x2b, |
| 117 | 0xab, 0x54, 0xd4, 0x14, 0x94, 0x74, 0xf4, 0x34, |
| 118 | 0xb4, 0x44, 0xc4, 0x04, 0x84, 0x64, 0xe4, 0x24, |
| 119 | 0xa4, 0x5c, 0xdc, 0x1c, 0x9c, 0x7c, 0xfc, 0x3c, |
| 120 | 0xbc, 0x4c, 0xcc, 0x0c, 0x8c, 0x6c, 0xec, 0x2c, |
| 121 | 0xac, 0x50, 0xd0, 0x10, 0x90, 0x70, 0xf0, 0x30, |
| 122 | 0xb0, 0x40, 0xc0, 0x00, 0x80, 0x60, 0xe0, 0x20, |
| 123 | 0x58, 0xd8, 0x18, 0x98, 0x78, 0xf8, 0x38, 0xb8, |
| 124 | 0x48, 0xc8, 0x08, 0x88, 0x68, 0xe8, 0x28, 0xa8, |
| 125 | 0xd6, 0x16, 0x96, 0x76, 0xf6, 0x36, 0xb6, 0x46, |
| 126 | 0xc6, 0x06, 0x86, 0x66, 0xe6, 0x26, 0xa6, 0xde, |
| 127 | 0x9e, 0x7e, 0xfe, 0x3e, 0xbe, 0x4e, 0xce, 0x0e, |
| 128 | 0x8e, 0x6e, 0xee, 0x2e, 0x52, 0x12, 0x72, 0x32, |
| 129 | 0xb2, 0x42, 0xc2, 0x02, 0x82, 0x62, 0xe2, 0x22, |
| 130 | 0xa2, 0x5a, 0xda, 0x1a, 0x9a, 0x7a, 0xfa, 0x3a, |
| 131 | 0xba, 0xba, 0x4a, 0x4a, 0xca, 0xca, 0x0a, 0x0a, |
| 132 | 0x8a, 0x8a, 0x6a, 0x6a, 0xea, 0xea, 0x2a, 0x2a |
| 133 | }; |
| 134 | |
| 135 | /* alaw -> 4bit compression */ |
| 136 | static u8 alaw_to_4bit[256] = { |
| 137 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 138 | 0x0d, 0x02, 0x08, 0x07, 0x0f, 0x00, 0x0b, 0x04, |
| 139 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 140 | 0x0d, 0x02, 0x09, 0x06, 0x0f, 0x00, 0x0b, 0x04, |
| 141 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 142 | 0x0d, 0x02, 0x08, 0x07, 0x0f, 0x00, 0x0b, 0x04, |
| 143 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 144 | 0x0d, 0x02, 0x09, 0x06, 0x0f, 0x00, 0x0b, 0x04, |
| 145 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 146 | 0x0d, 0x02, 0x08, 0x07, 0x0f, 0x00, 0x0b, 0x04, |
| 147 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0d, 0x02, |
| 148 | 0x0e, 0x02, 0x09, 0x06, 0x0f, 0x00, 0x0b, 0x04, |
| 149 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 150 | 0x0d, 0x02, 0x08, 0x07, 0x0f, 0x00, 0x0b, 0x04, |
| 151 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 152 | 0x0d, 0x02, 0x09, 0x06, 0x0f, 0x00, 0x0b, 0x04, |
| 153 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 154 | 0x0d, 0x02, 0x08, 0x07, 0x0f, 0x00, 0x0b, 0x04, |
| 155 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 156 | 0x0d, 0x02, 0x09, 0x06, 0x0f, 0x00, 0x0b, 0x04, |
| 157 | 0x0e, 0x02, 0x09, 0x06, 0x0f, 0x00, 0x0b, 0x04, |
| 158 | 0x0d, 0x02, 0x08, 0x07, 0x0f, 0x01, 0x0a, 0x05, |
| 159 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 160 | 0x0d, 0x02, 0x09, 0x07, 0x0f, 0x00, 0x0b, 0x04, |
| 161 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 162 | 0x0d, 0x02, 0x08, 0x07, 0x0f, 0x00, 0x0b, 0x04, |
| 163 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 164 | 0x0d, 0x02, 0x09, 0x06, 0x0f, 0x00, 0x0b, 0x04, |
| 165 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 166 | 0x0d, 0x02, 0x08, 0x07, 0x0f, 0x00, 0x0b, 0x04, |
| 167 | 0x0e, 0x01, 0x0a, 0x05, 0x0f, 0x00, 0x0c, 0x03, |
| 168 | 0x0d, 0x02, 0x09, 0x06, 0x0f, 0x00, 0x0b, 0x04, |
| 169 | }; |
| 170 | |
| 171 | /* 4bit -> alaw decompression */ |
| 172 | static u8 _4bit_to_alaw[16] = { |
| 173 | 0x5d, 0x51, 0xd9, 0xd7, 0x5f, 0x53, 0xa3, 0x4b, |
| 174 | 0x2a, 0x3a, 0x22, 0x2e, 0x26, 0x56, 0x20, 0x2c, |
| 175 | }; |
| 176 | |
| 177 | /* ulaw -> 4bit compression */ |
| 178 | static u8 ulaw_to_4bit[256] = { |
| 179 | 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, |
| 180 | 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, |
| 181 | 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, |
| 182 | 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, |
| 183 | 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, |
| 184 | 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, |
| 185 | 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, |
| 186 | 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, |
| 187 | 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, |
| 188 | 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x04, 0x04, |
| 189 | 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, |
| 190 | 0x04, 0x04, 0x04, 0x04, 0x05, 0x05, 0x05, 0x05, |
| 191 | 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, |
| 192 | 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, |
| 193 | 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, |
| 194 | 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x08, |
| 195 | 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, |
| 196 | 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, |
| 197 | 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, |
| 198 | 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, 0x0f, |
| 199 | 0x0f, 0x0e, 0x0e, 0x0e, 0x0e, 0x0e, 0x0e, 0x0e, |
| 200 | 0x0e, 0x0e, 0x0e, 0x0e, 0x0e, 0x0e, 0x0e, 0x0e, |
| 201 | 0x0e, 0x0d, 0x0d, 0x0d, 0x0d, 0x0d, 0x0d, 0x0d, |
| 202 | 0x0d, 0x0d, 0x0d, 0x0d, 0x0d, 0x0d, 0x0d, 0x0d, |
| 203 | 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, |
| 204 | 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0c, 0x0b, 0x0b, |
| 205 | 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, |
| 206 | 0x0b, 0x0b, 0x0b, 0x0b, 0x0a, 0x0a, 0x0a, 0x0a, |
| 207 | 0x0a, 0x0a, 0x0a, 0x0a, 0x0a, 0x0a, 0x0a, 0x0a, |
| 208 | 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, |
| 209 | 0x09, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, |
| 210 | 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, |
| 211 | }; |
| 212 | |
| 213 | /* 4bit -> ulaw decompression */ |
| 214 | static u8 _4bit_to_ulaw[16] = { |
| 215 | 0x11, 0x21, 0x31, 0x40, 0x4e, 0x5c, 0x68, 0x71, |
| 216 | 0xfe, 0xef, 0xe7, 0xdb, 0xcd, 0xbf, 0xaf, 0x9f, |
| 217 | }; |
| 218 | |
| 219 | |
| 220 | /* |
| 221 | * Compresses data to the result buffer |
| 222 | * The result size must be at least half of the input buffer. |
| 223 | * The number of samples also must be even! |
| 224 | */ |
| 225 | int |
| 226 | l1oip_law_to_4bit(u8 *data, int len, u8 *result, u32 *state) |
| 227 | { |
| 228 | int ii, i = 0, o = 0; |
| 229 | |
| 230 | if (!len) |
| 231 | return 0; |
| 232 | |
| 233 | /* send saved byte and first input byte */ |
| 234 | if (*state) { |
| 235 | *result++ = table_com[(((*state)<<8)&0xff00) | (*data++)]; |
| 236 | len--; |
| 237 | o++; |
| 238 | } |
| 239 | |
| 240 | ii = len >> 1; |
| 241 | |
| 242 | while (i < ii) { |
| 243 | *result++ = table_com[(data[0]<<8) | (data[1])]; |
| 244 | data += 2; |
| 245 | i++; |
| 246 | o++; |
| 247 | } |
| 248 | |
| 249 | /* if len has an odd number, we save byte for next call */ |
| 250 | if (len & 1) |
| 251 | *state = 0x100 + *data; |
| 252 | else |
| 253 | *state = 0; |
| 254 | |
| 255 | return o; |
| 256 | } |
| 257 | |
| 258 | /* Decompress data to the result buffer |
| 259 | * The result size must be the number of sample in packet. (2 * input data) |
| 260 | * The number of samples in the result are even! |
| 261 | */ |
| 262 | int |
| 263 | l1oip_4bit_to_law(u8 *data, int len, u8 *result) |
| 264 | { |
| 265 | int i = 0; |
| 266 | u16 r; |
| 267 | |
| 268 | while (i < len) { |
| 269 | r = table_dec[*data++]; |
| 270 | *result++ = r>>8; |
| 271 | *result++ = r; |
| 272 | i++; |
| 273 | } |
| 274 | |
| 275 | return len << 1; |
| 276 | } |
| 277 | |
| 278 | |
| 279 | /* |
| 280 | * law conversion |
| 281 | */ |
| 282 | int |
| 283 | l1oip_alaw_to_ulaw(u8 *data, int len, u8 *result) |
| 284 | { |
| 285 | int i = 0; |
| 286 | |
| 287 | while (i < len) { |
| 288 | *result++ = alaw_to_ulaw[*data++]; |
| 289 | i++; |
| 290 | } |
| 291 | |
| 292 | return len; |
| 293 | } |
| 294 | |
| 295 | int |
| 296 | l1oip_ulaw_to_alaw(u8 *data, int len, u8 *result) |
| 297 | { |
| 298 | int i = 0; |
| 299 | |
| 300 | while (i < len) { |
| 301 | *result++ = ulaw_to_alaw[*data++]; |
| 302 | i++; |
| 303 | } |
| 304 | |
| 305 | return len; |
| 306 | } |
| 307 | |
| 308 | |
| 309 | /* |
| 310 | * generate/free compression and decompression table |
| 311 | */ |
| 312 | void |
| 313 | l1oip_4bit_free(void) |
| 314 | { |
| 315 | if (table_dec) |
| 316 | vfree(table_dec); |
| 317 | if (table_com) |
| 318 | vfree(table_com); |
| 319 | table_com = NULL; |
| 320 | table_dec = NULL; |
| 321 | } |
| 322 | |
| 323 | int |
| 324 | l1oip_4bit_alloc(int ulaw) |
| 325 | { |
| 326 | int i1, i2, c, sample; |
| 327 | |
| 328 | /* in case, it is called again */ |
| 329 | if (table_dec) |
| 330 | return 0; |
| 331 | |
| 332 | /* alloc conversion tables */ |
Joe Perches | 1ac4594 | 2011-05-28 10:36:26 -0700 | [diff] [blame] | 333 | table_com = vzalloc(65536); |
| 334 | table_dec = vzalloc(512); |
Alexey Zaytsev | 24ec68f | 2009-01-10 02:48:05 +0300 | [diff] [blame] | 335 | if (!table_com || !table_dec) { |
Karsten Keil | 3712b42 | 2008-07-27 02:02:10 +0200 | [diff] [blame] | 336 | l1oip_4bit_free(); |
| 337 | return -ENOMEM; |
| 338 | } |
Karsten Keil | 3712b42 | 2008-07-27 02:02:10 +0200 | [diff] [blame] | 339 | /* generate compression table */ |
| 340 | i1 = 0; |
| 341 | while (i1 < 256) { |
| 342 | if (ulaw) |
| 343 | c = ulaw_to_4bit[i1]; |
| 344 | else |
| 345 | c = alaw_to_4bit[i1]; |
| 346 | i2 = 0; |
| 347 | while (i2 < 256) { |
| 348 | table_com[(i1<<8) | i2] |= (c<<4); |
| 349 | table_com[(i2<<8) | i1] |= c; |
| 350 | i2++; |
| 351 | } |
| 352 | i1++; |
| 353 | } |
| 354 | |
| 355 | /* generate decompression table */ |
| 356 | i1 = 0; |
| 357 | while (i1 < 16) { |
| 358 | if (ulaw) |
| 359 | sample = _4bit_to_ulaw[i1]; |
| 360 | else |
| 361 | sample = _4bit_to_alaw[i1]; |
| 362 | i2 = 0; |
| 363 | while (i2 < 16) { |
| 364 | table_dec[(i1<<4) | i2] |= (sample<<8); |
| 365 | table_dec[(i2<<4) | i1] |= sample; |
| 366 | i2++; |
| 367 | } |
| 368 | i1++; |
| 369 | } |
| 370 | |
| 371 | return 0; |
| 372 | } |
| 373 | |
| 374 | |