contrib/src/mmedia/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 }