Tristan Matthews | 0a329cc | 2013-07-17 13:20:14 -0400 | [diff] [blame] | 1 | /* |
| 2 | * This source code is a product of Sun Microsystems, Inc. and is provided |
| 3 | * for unrestricted use. Users may copy or modify this source code without |
| 4 | * charge. |
| 5 | * |
| 6 | * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING |
| 7 | * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR |
| 8 | * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. |
| 9 | * |
| 10 | * Sun source code is provided with no support and without any obligation on |
| 11 | * the part of Sun Microsystems, Inc. to assist in its use, correction, |
| 12 | * modification or enhancement. |
| 13 | * |
| 14 | * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE |
| 15 | * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE |
| 16 | * OR ANY PART THEREOF. |
| 17 | * |
| 18 | * In no event will Sun Microsystems, Inc. be liable for any lost revenue |
| 19 | * or profits or other special, indirect and consequential damages, even if |
| 20 | * Sun has been advised of the possibility of such damages. |
| 21 | * |
| 22 | * Sun Microsystems, Inc. |
| 23 | * 2550 Garcia Avenue |
| 24 | * Mountain View, California 94043 |
| 25 | */ |
| 26 | #include <pjmedia/alaw_ulaw.h> |
| 27 | |
| 28 | #if !defined(PJMEDIA_HAS_ALAW_ULAW_TABLE) || PJMEDIA_HAS_ALAW_ULAW_TABLE==0 |
| 29 | |
| 30 | #ifdef _MSC_VER |
| 31 | # pragma warning ( disable: 4244 ) /* Conversion from int to char etc */ |
| 32 | #endif |
| 33 | |
| 34 | /* |
| 35 | * g711.c |
| 36 | * |
| 37 | * u-law, A-law and linear PCM conversions. |
| 38 | */ |
| 39 | #define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */ |
| 40 | #define QUANT_MASK (0xf) /* Quantization field mask. */ |
| 41 | #define NSEGS (8) /* Number of A-law segments. */ |
| 42 | #define SEG_SHIFT (4) /* Left shift for segment number. */ |
| 43 | #define SEG_MASK (0x70) /* Segment field mask. */ |
| 44 | |
| 45 | static short seg_end[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF, |
| 46 | 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF}; |
| 47 | |
| 48 | /* copy from CCITT G.711 specifications */ |
| 49 | static unsigned char _u2a[128] = { /* u- to A-law conversions */ |
| 50 | 1, 1, 2, 2, 3, 3, 4, 4, |
| 51 | 5, 5, 6, 6, 7, 7, 8, 8, |
| 52 | 9, 10, 11, 12, 13, 14, 15, 16, |
| 53 | 17, 18, 19, 20, 21, 22, 23, 24, |
| 54 | 25, 27, 29, 31, 33, 34, 35, 36, |
| 55 | 37, 38, 39, 40, 41, 42, 43, 44, |
| 56 | 46, 48, 49, 50, 51, 52, 53, 54, |
| 57 | 55, 56, 57, 58, 59, 60, 61, 62, |
| 58 | 64, 65, 66, 67, 68, 69, 70, 71, |
| 59 | 72, 73, 74, 75, 76, 77, 78, 79, |
| 60 | 81, 82, 83, 84, 85, 86, 87, 88, |
| 61 | 89, 90, 91, 92, 93, 94, 95, 96, |
| 62 | 97, 98, 99, 100, 101, 102, 103, 104, |
| 63 | 105, 106, 107, 108, 109, 110, 111, 112, |
| 64 | 113, 114, 115, 116, 117, 118, 119, 120, |
| 65 | 121, 122, 123, 124, 125, 126, 127, 128}; |
| 66 | |
| 67 | static unsigned char _a2u[128] = { /* A- to u-law conversions */ |
| 68 | 1, 3, 5, 7, 9, 11, 13, 15, |
| 69 | 16, 17, 18, 19, 20, 21, 22, 23, |
| 70 | 24, 25, 26, 27, 28, 29, 30, 31, |
| 71 | 32, 32, 33, 33, 34, 34, 35, 35, |
| 72 | 36, 37, 38, 39, 40, 41, 42, 43, |
| 73 | 44, 45, 46, 47, 48, 48, 49, 49, |
| 74 | 50, 51, 52, 53, 54, 55, 56, 57, |
| 75 | 58, 59, 60, 61, 62, 63, 64, 64, |
| 76 | 65, 66, 67, 68, 69, 70, 71, 72, |
| 77 | 73, 74, 75, 76, 77, 78, 79, 79, |
| 78 | 80, 81, 82, 83, 84, 85, 86, 87, |
| 79 | 88, 89, 90, 91, 92, 93, 94, 95, |
| 80 | 96, 97, 98, 99, 100, 101, 102, 103, |
| 81 | 104, 105, 106, 107, 108, 109, 110, 111, |
| 82 | 112, 113, 114, 115, 116, 117, 118, 119, |
| 83 | 120, 121, 122, 123, 124, 125, 126, 127}; |
| 84 | |
| 85 | static int |
| 86 | search( |
| 87 | int val, |
| 88 | short *table, |
| 89 | int size) |
| 90 | { |
| 91 | int i; |
| 92 | |
| 93 | for (i = 0; i < size; i++) { |
| 94 | if (val <= *table++) |
| 95 | return (i); |
| 96 | } |
| 97 | return (size); |
| 98 | } |
| 99 | |
| 100 | /* |
| 101 | * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law |
| 102 | * |
| 103 | * linear2alaw() accepts an 16-bit integer and encodes it as A-law data. |
| 104 | * |
| 105 | * Linear Input Code Compressed Code |
| 106 | * ------------------------ --------------- |
| 107 | * 0000000wxyza 000wxyz |
| 108 | * 0000001wxyza 001wxyz |
| 109 | * 000001wxyzab 010wxyz |
| 110 | * 00001wxyzabc 011wxyz |
| 111 | * 0001wxyzabcd 100wxyz |
| 112 | * 001wxyzabcde 101wxyz |
| 113 | * 01wxyzabcdef 110wxyz |
| 114 | * 1wxyzabcdefg 111wxyz |
| 115 | * |
| 116 | * For further information see John C. Bellamy's Digital Telephony, 1982, |
| 117 | * John Wiley & Sons, pps 98-111 and 472-476. |
| 118 | */ |
| 119 | PJ_DEF(pj_uint8_t) pjmedia_linear2alaw( |
| 120 | int pcm_val) /* 2's complement (16-bit range) */ |
| 121 | { |
| 122 | int mask; |
| 123 | int seg; |
| 124 | unsigned char aval; |
| 125 | |
| 126 | if (pcm_val >= 0) { |
| 127 | mask = 0xD5; /* sign (7th) bit = 1 */ |
| 128 | } else { |
| 129 | mask = 0x55; /* sign bit = 0 */ |
| 130 | pcm_val = -pcm_val - 8; |
| 131 | |
| 132 | /* https://trac.pjsip.org/repos/ticket/1301 |
| 133 | * Thank you K Johnson - Zetron - 27 May 2011 |
| 134 | */ |
| 135 | if (pcm_val < 0) |
| 136 | pcm_val = 0; |
| 137 | } |
| 138 | |
| 139 | /* Convert the scaled magnitude to segment number. */ |
| 140 | seg = search(pcm_val, seg_end, 8); |
| 141 | |
| 142 | /* Combine the sign, segment, and quantization bits. */ |
| 143 | |
| 144 | if (seg >= 8) /* out of range, return maximum value. */ |
| 145 | return (0x7F ^ mask); |
| 146 | else { |
| 147 | aval = seg << SEG_SHIFT; |
| 148 | if (seg < 2) |
| 149 | aval |= (pcm_val >> 4) & QUANT_MASK; |
| 150 | else |
| 151 | aval |= (pcm_val >> (seg + 3)) & QUANT_MASK; |
| 152 | return (aval ^ mask); |
| 153 | } |
| 154 | } |
| 155 | |
| 156 | /* |
| 157 | * alaw2linear() - Convert an A-law value to 16-bit linear PCM |
| 158 | * |
| 159 | */ |
| 160 | PJ_DEF(int) pjmedia_alaw2linear( |
| 161 | unsigned a_val) |
| 162 | { |
| 163 | int t; |
| 164 | int seg; |
| 165 | |
| 166 | a_val ^= 0x55; |
| 167 | |
| 168 | t = (a_val & QUANT_MASK) << 4; |
| 169 | seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT; |
| 170 | switch (seg) { |
| 171 | case 0: |
| 172 | t += 8; |
| 173 | break; |
| 174 | case 1: |
| 175 | t += 0x108; |
| 176 | break; |
| 177 | default: |
| 178 | t += 0x108; |
| 179 | t <<= seg - 1; |
| 180 | } |
| 181 | return ((a_val & SIGN_BIT) ? t : -t); |
| 182 | } |
| 183 | |
| 184 | #define BIAS (0x84) /* Bias for linear code. */ |
| 185 | |
| 186 | /* |
| 187 | * linear2ulaw() - Convert a linear PCM value to u-law |
| 188 | * |
| 189 | * In order to simplify the encoding process, the original linear magnitude |
| 190 | * is biased by adding 33 which shifts the encoding range from (0 - 8158) to |
| 191 | * (33 - 8191). The result can be seen in the following encoding table: |
| 192 | * |
| 193 | * Biased Linear Input Code Compressed Code |
| 194 | * ------------------------ --------------- |
| 195 | * 00000001wxyza 000wxyz |
| 196 | * 0000001wxyzab 001wxyz |
| 197 | * 000001wxyzabc 010wxyz |
| 198 | * 00001wxyzabcd 011wxyz |
| 199 | * 0001wxyzabcde 100wxyz |
| 200 | * 001wxyzabcdef 101wxyz |
| 201 | * 01wxyzabcdefg 110wxyz |
| 202 | * 1wxyzabcdefgh 111wxyz |
| 203 | * |
| 204 | * Each biased linear code has a leading 1 which identifies the segment |
| 205 | * number. The value of the segment number is equal to 7 minus the number |
| 206 | * of leading 0's. The quantization interval is directly available as the |
| 207 | * four bits wxyz. * The trailing bits (a - h) are ignored. |
| 208 | * |
| 209 | * Ordinarily the complement of the resulting code word is used for |
| 210 | * transmission, and so the code word is complemented before it is returned. |
| 211 | * |
| 212 | * For further information see John C. Bellamy's Digital Telephony, 1982, |
| 213 | * John Wiley & Sons, pps 98-111 and 472-476. |
| 214 | */ |
| 215 | PJ_DEF(unsigned char) pjmedia_linear2ulaw( |
| 216 | int pcm_val) /* 2's complement (16-bit range) */ |
| 217 | { |
| 218 | int mask; |
| 219 | int seg; |
| 220 | unsigned char uval; |
| 221 | |
| 222 | /* Get the sign and the magnitude of the value. */ |
| 223 | if (pcm_val < 0) { |
| 224 | pcm_val = BIAS - pcm_val; |
| 225 | mask = 0x7F; |
| 226 | } else { |
| 227 | pcm_val += BIAS; |
| 228 | mask = 0xFF; |
| 229 | } |
| 230 | |
| 231 | /* Convert the scaled magnitude to segment number. */ |
| 232 | seg = search(pcm_val, seg_end, 8); |
| 233 | |
| 234 | /* |
| 235 | * Combine the sign, segment, quantization bits; |
| 236 | * and complement the code word. |
| 237 | */ |
| 238 | if (seg >= 8) /* out of range, return maximum value. */ |
| 239 | return (0x7F ^ mask); |
| 240 | else { |
| 241 | uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF); |
| 242 | return (uval ^ mask); |
| 243 | } |
| 244 | |
| 245 | } |
| 246 | |
| 247 | /* |
| 248 | * ulaw2linear() - Convert a u-law value to 16-bit linear PCM |
| 249 | * |
| 250 | * First, a biased linear code is derived from the code word. An unbiased |
| 251 | * output can then be obtained by subtracting 33 from the biased code. |
| 252 | * |
| 253 | * Note that this function expects to be passed the complement of the |
| 254 | * original code word. This is in keeping with ISDN conventions. |
| 255 | */ |
| 256 | PJ_DEF(int) pjmedia_ulaw2linear( |
| 257 | unsigned char u_val) |
| 258 | { |
| 259 | int t; |
| 260 | |
| 261 | /* Shortcut: when input is zero, output is zero |
| 262 | * This will also make the VAD works harder. |
| 263 | * -bennylp |
| 264 | */ |
| 265 | if (u_val == 0) return 0; |
| 266 | |
| 267 | /* Complement to obtain normal u-law value. */ |
| 268 | u_val = ~u_val; |
| 269 | |
| 270 | /* |
| 271 | * Extract and bias the quantization bits. Then |
| 272 | * shift up by the segment number and subtract out the bias. |
| 273 | */ |
| 274 | t = ((u_val & QUANT_MASK) << 3) + BIAS; |
| 275 | t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT; |
| 276 | |
| 277 | return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS)); |
| 278 | } |
| 279 | |
| 280 | /* A-law to u-law conversion */ |
| 281 | PJ_DEF(unsigned char) pjmedia_alaw2ulaw( |
| 282 | unsigned char aval) |
| 283 | { |
| 284 | aval &= 0xff; |
| 285 | return ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) : |
| 286 | (0x7F ^ _a2u[aval ^ 0x55])); |
| 287 | } |
| 288 | |
| 289 | /* u-law to A-law conversion */ |
| 290 | PJ_DEF(unsigned char) pjmedia_ulaw2alaw( |
| 291 | unsigned char uval) |
| 292 | { |
| 293 | uval &= 0xff; |
| 294 | return ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) : |
| 295 | (0x55 ^ (_u2a[0x7F ^ uval] - 1))); |
| 296 | } |
| 297 | |
| 298 | |
| 299 | #endif /* PJMEDIA_HAS_ALAW_ULAW_TABLE */ |
| 300 | |