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