wsutil/g711.c

   1 /*
   2  * $Id$
   3  *
   4  * This source code is a product of Sun Microsystems, Inc. and is provided
   5  * for unrestricted use.  Users may copy or modify this source code without
   6  * charge.
   7  *
   8  * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
   9  * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
  10  * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
  11  *
  12  * Sun source code is provided with no support and without any obligation on
  13  * the part of Sun Microsystems, Inc. to assist in its use, correction,
  14  * modification or enhancement.
  15  *
  16  * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
  17  * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
  18  * OR ANY PART THEREOF.
  19  *
  20  * In no event will Sun Microsystems, Inc. be liable for any lost revenue
  21  * or profits or other special, indirect and consequential damages, even if
  22  * Sun has been advised of the possibility of such damages.
  23  *
  24  * Sun Microsystems, Inc.
  25  * 2550 Garcia Avenue
  26  * Mountain View, California  94043
  27  */
  28
  29 #include "g711.h"
  30
  31 /*
  32  * g711.c
  33  *
  34  * u-law, A-law and linear PCM conversions.
  35  */
  36 #define SIGN_BIT        (0x80)          /* Sign bit for a A-law byte. */
  37 #define QUANT_MASK      (0xf)           /* Quantization field mask. */
  38 #define NSEGS           (8)             /* Number of A-law segments. */
  39 #define SEG_SHIFT       (4)             /* Left shift for segment number. */
  40 #define SEG_MASK        (0x70)          /* Segment field mask. */
  41
  42 static short seg_end[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF,
  43                             0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};
  44
  45 /* copy from CCITT G.711 specifications */
  46 unsigned char _u2a[128] = {                     /* u- to A-law conversions */
  47         1,      1,      2,      2,      3,      3,      4,      4,
  48         5,      5,      6,      6,      7,      7,      8,      8,
  49         9,      10,     11,     12,     13,     14,     15,     16,
  50         17,     18,     19,     20,     21,     22,     23,     24,
  51         25,     27,     29,     31,     33,     34,     35,     36,
  52         37,     38,     39,     40,     41,     42,     43,     44,
  53         46,     48,     49,     50,     51,     52,     53,     54,
  54         55,     56,     57,     58,     59,     60,     61,     62,
  55         64,     65,     66,     67,     68,     69,     70,     71,
  56         72,     73,     74,     75,     76,     77,     78,     79,
  57         81,     82,     83,     84,     85,     86,     87,     88,
  58         89,     90,     91,     92,     93,     94,     95,     96,
  59         97,     98,     99,     100,    101,    102,    103,    104,
  60         105,    106,    107,    108,    109,    110,    111,    112,
  61         113,    114,    115,    116,    117,    118,    119,    120,
  62         121,    122,    123,    124,    125,    126,    127,    128};
  63
  64 unsigned char _a2u[128] = {                     /* A- to u-law conversions */
  65         1,      3,      5,      7,      9,      11,     13,     15,
  66         16,     17,     18,     19,     20,     21,     22,     23,
  67         24,     25,     26,     27,     28,     29,     30,     31,
  68         32,     32,     33,     33,     34,     34,     35,     35,
  69         36,     37,     38,     39,     40,     41,     42,     43,
  70         44,     45,     46,     47,     48,     48,     49,     49,
  71         50,     51,     52,     53,     54,     55,     56,     57,
  72         58,     59,     60,     61,     62,     63,     64,     64,
  73         65,     66,     67,     68,     69,     70,     71,     72,
  74         73,     74,     75,     76,     77,     78,     79,     79,
  75         80,     81,     82,     83,     84,     85,     86,     87,
  76         88,     89,     90,     91,     92,     93,     94,     95,
  77         96,     97,     98,     99,     100,    101,    102,    103,
  78         104,    105,    106,    107,    108,    109,    110,    111,
  79         112,    113,    114,    115,    116,    117,    118,    119,
  80         120,    121,    122,    123,    124,    125,    126,    127};
  81
  82 static int
  83 search(
  84         int             val,
  85         short           *table,
  86         int             size)
  87 {
  88         int             i;
  89
  90         for (i = 0; i < size; i++) {
  91                 if (val <= *table++)
  92                         return (i);
  93         }
  94         return (size);
  95 }
  96
  97 /*
  98  * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
  99  *
 100  * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
 101  *
 102  *              Linear Input Code       Compressed Code
 103  *      ------------------------        ---------------
 104  *      0000000wxyza                    000wxyz
 105  *      0000001wxyza                    001wxyz
 106  *      000001wxyzab                    010wxyz
 107  *      00001wxyzabc                    011wxyz
 108  *      0001wxyzabcd                    100wxyz
 109  *      001wxyzabcde                    101wxyz
 110  *      01wxyzabcdef                    110wxyz
 111  *      1wxyzabcdefg                    111wxyz
 112  *
 113  * For further information see John C. Bellamy's Digital Telephony, 1982,
 114  * John Wiley & Sons, pps 98-111 and 472-476.
 115  */
 116 unsigned char
 117 linear2alaw(
 118         int             pcm_val)        /* 2's complement (16-bit range) */
 119 {
 120         int             mask;
 121         int             seg;
 122         unsigned char   aval;
 123         if (pcm_val >= 0) {
 124                 mask = 0xD5;            /* sign (7th) bit = 1 */
 125         } else {
 126                 mask = 0x55;            /* sign bit = 0 */
 127                 pcm_val = -pcm_val - 8;
 128         }
 129
 130         /* Convert the scaled magnitude to segment number. */
 131         seg = search(pcm_val, seg_end, 8);
 132
 133         /* Combine the sign, segment, and quantization bits. */
 134
 135         if (seg >= 8)           /* out of range, return maximum value. */
 136                 return (0x7F ^ mask);
 137         else {
 138                 aval = seg << SEG_SHIFT;
 139                 if (seg < 2)
 140                         aval |= (pcm_val >> 4) & QUANT_MASK;
 141                 else
 142                         aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
 143                 return (aval ^ mask);
 144         }
 145 }
 146
 147 /*
 148  * alaw2linear() - Convert an A-law value to 16-bit linear PCM
 149  *
 150  */
 151 int
 152 alaw2linear(
 153         unsigned char   a_val)
 154 {
 155         int             t;
 156         int             seg;
 157         /*printf(" vrednost a_val %X ", a_val);*/
 158         a_val ^= 0x55;
 159
 160         t = (a_val & QUANT_MASK) << 4;
 161         seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
 162         switch (seg) {
 163         case 0:
 164                 t += 8;
 165                 break;
 166         case 1:
 167                 t += 0x108;
 168                 break;
 169         default:
 170                 t += 0x108;
 171                 t <<= seg - 1;
 172         }
 173         /*printf("izracunan int %d in njegov hex %X \n", t,t);*/
 174         return ((a_val & SIGN_BIT) ? t : -t);
 175 }
 176
 177 #define BIAS            (0x84)          /* Bias for linear code. */
 178
 179 /*
 180  * linear2ulaw() - Convert a linear PCM value to u-law
 181  *
 182  * In order to simplify the encoding process, the original linear magnitude
 183  * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
 184  * (33 - 8191). The result can be seen in the following encoding table:
 185  *
 186  *      Biased Linear Input Code        Compressed Code
 187  *      ------------------------        ---------------
 188  *      00000001wxyza                   000wxyz
 189  *      0000001wxyzab                   001wxyz
 190  *      000001wxyzabc                   010wxyz
 191  *      00001wxyzabcd                   011wxyz
 192  *      0001wxyzabcde                   100wxyz
 193  *      001wxyzabcdef                   101wxyz
 194  *      01wxyzabcdefg                   110wxyz
 195  *      1wxyzabcdefgh                   111wxyz
 196  *
 197  * Each biased linear code has a leading 1 which identifies the segment
 198  * number. The value of the segment number is equal to 7 minus the number
 199  * of leading 0's. The quantization interval is directly available as the
 200  * four bits wxyz.  * The trailing bits (a - h) are ignored.
 201  *
 202  * Ordinarily the complement of the resulting code word is used for
 203  * transmission, and so the code word is complemented before it is returned.
 204  *
 205  * For further information see John C. Bellamy's Digital Telephony, 1982,
 206  * John Wiley & Sons, pps 98-111 and 472-476.
 207  */
 208 unsigned char
 209 linear2ulaw(
 210         int             pcm_val)        /* 2's complement (16-bit range) */
 211 {
 212         int             mask;
 213         int             seg;
 214         unsigned char   uval;
 215
 216         /* Get the sign and the magnitude of the value. */
 217         if (pcm_val < 0) {
 218                 pcm_val = BIAS - pcm_val;
 219                 mask = 0x7F;
 220         } else {
 221                 pcm_val += BIAS;
 222                 mask = 0xFF;
 223         }
 224
 225         /* Convert the scaled magnitude to segment number. */
 226         seg = search(pcm_val, seg_end, 8);
 227
 228         /*
 229          * Combine the sign, segment, quantization bits;
 230          * and complement the code word.
 231          */
 232         if (seg >= 8)           /* out of range, return maximum value. */
 233                 return (0x7F ^ mask);
 234         else {
 235                 uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
 236                 return (uval ^ mask);
 237         }
 238
 239 }
 240
 241 /*
 242  * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
 243  *
 244  * First, a biased linear code is derived from the code word. An unbiased
 245  * output can then be obtained by subtracting 33 from the biased code.
 246  *
 247  * Note that this function expects to be passed the complement of the
 248  * original code word. This is in keeping with ISDN conventions.
 249  */
 250 int
 251 ulaw2linear(
 252         unsigned char   u_val)
 253 {
 254         int             t;
 255
 256         /* Complement to obtain normal u-law value. */
 257         u_val = ~u_val;
 258
 259         /*
 260          * Extract and bias the quantization bits. Then
 261          * shift up by the segment number and subtract out the bias.
 262          */
 263         t = ((u_val & QUANT_MASK) << 3) + BIAS;
 264         t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
 265
 266         return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
 267 }
 268
 269 /* A-law to u-law conversion */
 270 /* unsigned char
 271  * alaw2ulaw(
 272  *      unsigned char   aval)
 273  * {
 274  *      aval &= 0xff;
 275  *      return ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :
 276  *          (0x7F ^ _a2u[aval ^ 0x55]));
 277  * }
 278  */
 279
 280 /* u-law to A-law conversion */
 281 /* unsigned char
 282  * ulaw2alaw(
 283  *      unsigned char   uval)
 284  * {
 285  *      uval &= 0xff;
 286  *      return ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :
 287  *          (0x55 ^ (_u2a[0x7F ^ uval] - 1)));
 288  * }
 289  */