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| 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 | |
| 27 | /*
|
| 28 | * g711.c |
| 29 | * |
| 30 | * u-law, A-law and linear PCM conversions. |
| 31 | */ |
| 32 | #define SIGN_BIT (0x80) /* Sign bit for a A-law byte. */ |
| 33 | #define QUANT_MASK (0xf) /* Quantization field mask. */ |
| 34 | #define NSEGS (8) /* Number of A-law segments. */ |
| 35 | #define SEG_SHIFT (4) /* Left shift for segment number. */ |
| 36 | #define SEG_MASK (0x70) /* Segment field mask. */ |
| 37 | |
| 38 | static short seg_end[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF, |
| 39 | 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF}; |
| 40 | |
| 41 | /* copy from CCITT G.711 specifications */
|
| 42 | unsigned char _u2a[128] = { /* u- to A-law conversions */ |
| 43 | 1, 1, 2, 2, 3, 3, 4, 4, |
| 44 | 5, 5, 6, 6, 7, 7, 8, 8, |
| 45 | 9, 10, 11, 12, 13, 14, 15, 16, |
| 46 | 17, 18, 19, 20, 21, 22, 23, 24, |
| 47 | 25, 27, 29, 31, 33, 34, 35, 36, |
| 48 | 37, 38, 39, 40, 41, 42, 43, 44, |
| 49 | 46, 48, 49, 50, 51, 52, 53, 54, |
| 50 | 55, 56, 57, 58, 59, 60, 61, 62, |
| 51 | 64, 65, 66, 67, 68, 69, 70, 71, |
| 52 | 72, 73, 74, 75, 76, 77, 78, 79, |
| 53 | 81, 82, 83, 84, 85, 86, 87, 88, |
| 54 | 89, 90, 91, 92, 93, 94, 95, 96, |
| 55 | 97, 98, 99, 100, 101, 102, 103, 104, |
| 56 | 105, 106, 107, 108, 109, 110, 111, 112, |
| 57 | 113, 114, 115, 116, 117, 118, 119, 120, |
| 58 | 121, 122, 123, 124, 125, 126, 127, 128}; |
| 59 | |
| 60 | unsigned char _a2u[128] = { /* A- to u-law conversions */ |
| 61 | 1, 3, 5, 7, 9, 11, 13, 15, |
| 62 | 16, 17, 18, 19, 20, 21, 22, 23, |
| 63 | 24, 25, 26, 27, 28, 29, 30, 31, |
| 64 | 32, 32, 33, 33, 34, 34, 35, 35, |
| 65 | 36, 37, 38, 39, 40, 41, 42, 43, |
| 66 | 44, 45, 46, 47, 48, 48, 49, 49, |
| 67 | 50, 51, 52, 53, 54, 55, 56, 57, |
| 68 | 58, 59, 60, 61, 62, 63, 64, 64, |
| 69 | 65, 66, 67, 68, 69, 70, 71, 72, |
| 70 | 73, 74, 75, 76, 77, 78, 79, 79, |
| 71 | 80, 81, 82, 83, 84, 85, 86, 87, |
| 72 | 88, 89, 90, 91, 92, 93, 94, 95, |
| 73 | 96, 97, 98, 99, 100, 101, 102, 103, |
| 74 | 104, 105, 106, 107, 108, 109, 110, 111, |
| 75 | 112, 113, 114, 115, 116, 117, 118, 119, |
| 76 | 120, 121, 122, 123, 124, 125, 126, 127}; |
| 77 | |
| 78 | static int |
| 79 | search( |
| 80 | int val,
|
| 81 | short *table,
|
| 82 | int size)
|
| 83 | {
|
| 84 | int i;
|
| 85 | |
| 86 | for (i = 0; i < size; i++) { |
| 87 | if (val <= *table++)
|
| 88 | return (i);
|
| 89 | } |
| 90 | return (size);
|
| 91 | } |
| 92 | |
| 93 | /*
|
| 94 | * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law |
| 95 | * |
| 96 | * linear2alaw() accepts an 16-bit integer and encodes it as A-law data. |
| 97 | * |
| 98 | * Linear Input Code Compressed Code |
| 99 | * ------------------------ --------------- |
| 100 | * 0000000wxyza 000wxyz |
| 101 | * 0000001wxyza 001wxyz |
| 102 | * 000001wxyzab 010wxyz |
| 103 | * 00001wxyzabc 011wxyz |
| 104 | * 0001wxyzabcd 100wxyz |
| 105 | * 001wxyzabcde 101wxyz |
| 106 | * 01wxyzabcdef 110wxyz |
| 107 | * 1wxyzabcdefg 111wxyz |
| 108 | * |
| 109 | * For further information see John C. Bellamy's Digital Telephony, 1982, |
| 110 | * John Wiley & Sons, pps 98-111 and 472-476. |
| 111 | */ |
| 112 | unsigned char |
| 113 | linear2alaw( |
| 114 | int pcm_val) /* 2's complement (16-bit range) */ |
| 115 | {
|
| 116 | int mask;
|
| 117 | int seg;
|
| 118 | unsigned char aval; |
| 119 | |
| 120 | if (pcm_val >= 0) { |
| 121 | mask = 0xD5; /* sign (7th) bit = 1 */ |
| 122 | } else {
|
| 123 | mask = 0x55; /* sign bit = 0 */ |
| 124 | pcm_val = -pcm_val - 8;
|
| 125 | } |
| 126 | |
| 127 | /* Convert the scaled magnitude to segment number. */
|
| 128 | seg = search(pcm_val, seg_end, 8);
|
| 129 | |
| 130 | /* Combine the sign, segment, and quantization bits. */
|
| 131 | |
| 132 | if (seg >= 8) /* out of range, return maximum value. */ |
| 133 | return (0x7F ^ mask); |
| 134 | else {
|
| 135 | aval = seg << SEG_SHIFT; |
| 136 | if (seg < 2) |
| 137 | aval |= (pcm_val >> 4) & QUANT_MASK;
|
| 138 | else
|
| 139 | aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
|
| 140 | return (aval ^ mask);
|
| 141 | } |
| 142 | } |
| 143 | |
| 144 | /*
|
| 145 | * alaw2linear() - Convert an A-law value to 16-bit linear PCM |
| 146 | * |
| 147 | */ |
| 148 | int
|
| 149 | alaw2linear( |
| 150 | unsigned char a_val) |
| 151 | {
|
| 152 | int t;
|
| 153 | int seg;
|
| 154 | |
| 155 | a_val ^= 0x55;
|
| 156 | |
| 157 | t = (a_val & QUANT_MASK) << 4;
|
| 158 | seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
|
| 159 | switch (seg) {
|
| 160 | case 0: |
| 161 | t += 8;
|
| 162 | break;
|
| 163 | case 1: |
| 164 | t += 0x108;
|
| 165 | break;
|
| 166 | default:
|
| 167 | t += 0x108;
|
| 168 | t <<= seg - 1;
|
| 169 | } |
| 170 | return ((a_val & SIGN_BIT) ? t : -t);
|
| 171 | } |
| 172 | |
| 173 | #define BIAS (0x84) /* Bias for linear code. */ |
| 174 | |
| 175 | /*
|
| 176 | * linear2ulaw() - Convert a linear PCM value to u-law |
| 177 | * |
| 178 | * In order to simplify the encoding process, the original linear magnitude |
| 179 | * is biased by adding 33 which shifts the encoding range from (0 - 8158) to |
| 180 | * (33 - 8191). The result can be seen in the following encoding table: |
| 181 | * |
| 182 | * Biased Linear Input Code Compressed Code |
| 183 | * ------------------------ --------------- |
| 184 | * 00000001wxyza 000wxyz |
| 185 | * 0000001wxyzab 001wxyz |
| 186 | * 000001wxyzabc 010wxyz |
| 187 | * 00001wxyzabcd 011wxyz |
| 188 | * 0001wxyzabcde 100wxyz |
| 189 | * 001wxyzabcdef 101wxyz |
| 190 | * 01wxyzabcdefg 110wxyz |
| 191 | * 1wxyzabcdefgh 111wxyz |
| 192 | * |
| 193 | * Each biased linear code has a leading 1 which identifies the segment |
| 194 | * number. The value of the segment number is equal to 7 minus the number |
| 195 | * of leading 0's. The quantization interval is directly available as the |
| 196 | * four bits wxyz. * The trailing bits (a - h) are ignored. |
| 197 | * |
| 198 | * Ordinarily the complement of the resulting code word is used for |
| 199 | * transmission, and so the code word is complemented before it is returned. |
| 200 | * |
| 201 | * For further information see John C. Bellamy's Digital Telephony, 1982, |
| 202 | * John Wiley & Sons, pps 98-111 and 472-476. |
| 203 | */ |
| 204 | unsigned char |
| 205 | linear2ulaw( |
| 206 | int pcm_val) /* 2's complement (16-bit range) */ |
| 207 | {
|
| 208 | int mask;
|
| 209 | int seg;
|
| 210 | unsigned char uval; |
| 211 | |
| 212 | /* Get the sign and the magnitude of the value. */
|
| 213 | if (pcm_val < 0) { |
| 214 | pcm_val = BIAS - pcm_val; |
| 215 | mask = 0x7F;
|
| 216 | } else {
|
| 217 | pcm_val += BIAS; |
| 218 | mask = 0xFF;
|
| 219 | } |
| 220 | |
| 221 | /* Convert the scaled magnitude to segment number. */
|
| 222 | seg = search(pcm_val, seg_end, 8);
|
| 223 | |
| 224 | /*
|
| 225 | * Combine the sign, segment, quantization bits; |
| 226 | * and complement the code word. |
| 227 | */ |
| 228 | if (seg >= 8) /* out of range, return maximum value. */ |
| 229 | return (0x7F ^ mask); |
| 230 | else {
|
| 231 | uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF); |
| 232 | return (uval ^ mask);
|
| 233 | } |
| 234 | |
| 235 | } |
| 236 | |
| 237 | /*
|
| 238 | * ulaw2linear() - Convert a u-law value to 16-bit linear PCM |
| 239 | * |
| 240 | * First, a biased linear code is derived from the code word. An unbiased |
| 241 | * output can then be obtained by subtracting 33 from the biased code. |
| 242 | * |
| 243 | * Note that this function expects to be passed the complement of the |
| 244 | * original code word. This is in keeping with ISDN conventions. |
| 245 | */ |
| 246 | int
|
| 247 | ulaw2linear( |
| 248 | unsigned char u_val) |
| 249 | {
|
| 250 | int t;
|
| 251 | |
| 252 | /* Complement to obtain normal u-law value. */
|
| 253 | u_val = ~u_val; |
| 254 | |
| 255 | /*
|
| 256 | * Extract and bias the quantization bits. Then |
| 257 | * shift up by the segment number and subtract out the bias. |
| 258 | */ |
| 259 | t = ((u_val & QUANT_MASK) << 3) + BIAS;
|
| 260 | t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
|
| 261 | |
| 262 | return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
|
| 263 | } |
| 264 | |
| 265 | /* A-law to u-law conversion */
|
| 266 | unsigned char |
| 267 | alaw2ulaw( |
| 268 | unsigned char aval) |
| 269 | {
|
| 270 | aval &= 0xff;
|
| 271 | return ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) : |
| 272 | (0x7F ^ _a2u[aval ^ 0x55])); |
| 273 | } |
| 274 | |
| 275 | /* u-law to A-law conversion */
|
| 276 | unsigned char |
| 277 | ulaw2alaw( |
| 278 | unsigned char uval) |
| 279 | {
|
| 280 | uval &= 0xff;
|
| 281 | return ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) : |
| 282 | (0x55 ^ (_u2a[0x7F ^ uval] - 1))); |
| 283 | } |