utils/wxMMedia2/lib/g711.cpp

   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 }