g711.c 7.57 KB
Newer Older
Mati's avatar
Mati committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289
/*
 * $Id: g711.c 15355 2005-08-14 23:25:20Z jmayer $
 *
 * This source code is a product of Sun Microsystems, Inc. and is provided
 * for unrestricted use.  Users may copy or modify this source code without
 * charge.
 *
 * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
 * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
 *
 * Sun source code is provided with no support and without any obligation on
 * the part of Sun Microsystems, Inc. to assist in its use, correction,
 * modification or enhancement.
 *
 * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
 * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
 * OR ANY PART THEREOF.
 *
 * In no event will Sun Microsystems, Inc. be liable for any lost revenue
 * or profits or other special, indirect and consequential damages, even if
 * Sun has been advised of the possibility of such damages.
 *
 * Sun Microsystems, Inc.
 * 2550 Garcia Avenue
 * Mountain View, California  94043
 */

#include "g711.h"

/*
 * g711.c
 *
 * u-law, A-law and linear PCM conversions.
 */
#define	SIGN_BIT	(0x80)		/* Sign bit for a A-law byte. */
#define	QUANT_MASK	(0xf)		/* Quantization field mask. */
#define	NSEGS		(8)		/* Number of A-law segments. */
#define	SEG_SHIFT	(4)		/* Left shift for segment number. */
#define	SEG_MASK	(0x70)		/* Segment field mask. */

static short seg_end[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF,
			    0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};

/* copy from CCITT G.711 specifications */
unsigned char _u2a[128] = {			/* u- to A-law conversions */
	1,	1,	2,	2,	3,	3,	4,	4,
	5,	5,	6,	6,	7,	7,	8,	8,
	9,	10,	11,	12,	13,	14,	15,	16,
	17,	18,	19,	20,	21,	22,	23,	24,
	25,	27,	29,	31,	33,	34,	35,	36,
	37,	38,	39,	40,	41,	42,	43,	44,
	46,	48,	49,	50,	51,	52,	53,	54,
	55,	56,	57,	58,	59,	60,	61,	62,
	64,	65,	66,	67,	68,	69,	70,	71,
	72,	73,	74,	75,	76,	77,	78,	79,
	81,	82,	83,	84,	85,	86,	87,	88,
	89,	90,	91,	92,	93,	94,	95,	96,
	97,	98,	99,	100,	101,	102,	103,	104,
	105,	106,	107,	108,	109,	110,	111,	112,
	113,	114,	115,	116,	117,	118,	119,	120,
	121,	122,	123,	124,	125,	126,	127,	128};

unsigned char _a2u[128] = {			/* A- to u-law conversions */
	1,	3,	5,	7,	9,	11,	13,	15,
	16,	17,	18,	19,	20,	21,	22,	23,
	24,	25,	26,	27,	28,	29,	30,	31,
	32,	32,	33,	33,	34,	34,	35,	35,
	36,	37,	38,	39,	40,	41,	42,	43,
	44,	45,	46,	47,	48,	48,	49,	49,
	50,	51,	52,	53,	54,	55,	56,	57,
	58,	59,	60,	61,	62,	63,	64,	64,
	65,	66,	67,	68,	69,	70,	71,	72,
	73,	74,	75,	76,	77,	78,	79,	79,
	80,	81,	82,	83,	84,	85,	86,	87,
	88,	89,	90,	91,	92,	93,	94,	95,
	96,	97,	98,	99,	100,	101,	102,	103,
	104,	105,	106,	107,	108,	109,	110,	111,
	112,	113,	114,	115,	116,	117,	118,	119,
	120,	121,	122,	123,	124,	125,	126,	127};

static int
search(
	int		val,
	short		*table,
	int		size)
{
	int		i;

	for (i = 0; i < size; i++) {
		if (val <= *table++)
			return (i);
	}
	return (size);
}

/*
 * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
 *
 * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
 *
 *		Linear Input Code	Compressed Code
 *	------------------------	---------------
 *	0000000wxyza			000wxyz
 *	0000001wxyza			001wxyz
 *	000001wxyzab			010wxyz
 *	00001wxyzabc			011wxyz
 *	0001wxyzabcd			100wxyz
 *	001wxyzabcde			101wxyz
 *	01wxyzabcdef			110wxyz
 *	1wxyzabcdefg			111wxyz
 *
 * For further information see John C. Bellamy's Digital Telephony, 1982,
 * John Wiley & Sons, pps 98-111 and 472-476.
 */
unsigned char
linear2alaw(
	int		pcm_val)	/* 2's complement (16-bit range) */
{
	int		mask;
	int		seg;
	unsigned char	aval;
	if (pcm_val >= 0) {
		mask = 0xD5;		/* sign (7th) bit = 1 */
	} else {
		mask = 0x55;		/* sign bit = 0 */
		pcm_val = -pcm_val - 8;
	}

	/* Convert the scaled magnitude to segment number. */
	seg = search(pcm_val, seg_end, 8);

	/* Combine the sign, segment, and quantization bits. */

	if (seg >= 8)		/* out of range, return maximum value. */
		return (0x7F ^ mask);
	else {
		aval = seg << SEG_SHIFT;
		if (seg < 2)
			aval |= (pcm_val >> 4) & QUANT_MASK;
		else
			aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
		return (aval ^ mask);
	}
}

/*
 * alaw2linear() - Convert an A-law value to 16-bit linear PCM
 *
 */
int
alaw2linear(
	unsigned char	a_val)
{
	int		t;
	int		seg;
	/*printf(" vrednost a_val %X ", a_val);*/
	a_val ^= 0x55;

	t = (a_val & QUANT_MASK) << 4;
	seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
	switch (seg) {
	case 0:
		t += 8;
		break;
	case 1:
		t += 0x108;
		break;
	default:
		t += 0x108;
		t <<= seg - 1;
	}
	/*printf("izracunan int %d in njegov hex %X \n", t,t);*/
	return ((a_val & SIGN_BIT) ? t : -t);
}

#define	BIAS		(0x84)		/* Bias for linear code. */

/*
 * linear2ulaw() - Convert a linear PCM value to u-law
 *
 * In order to simplify the encoding process, the original linear magnitude
 * is biased by adding 33 which shifts the encoding range from (0 - 8158) to
 * (33 - 8191). The result can be seen in the following encoding table:
 *
 *	Biased Linear Input Code	Compressed Code
 *	------------------------	---------------
 *	00000001wxyza			000wxyz
 *	0000001wxyzab			001wxyz
 *	000001wxyzabc			010wxyz
 *	00001wxyzabcd			011wxyz
 *	0001wxyzabcde			100wxyz
 *	001wxyzabcdef			101wxyz
 *	01wxyzabcdefg			110wxyz
 *	1wxyzabcdefgh			111wxyz
 *
 * Each biased linear code has a leading 1 which identifies the segment
 * number. The value of the segment number is equal to 7 minus the number
 * of leading 0's. The quantization interval is directly available as the
 * four bits wxyz.  * The trailing bits (a - h) are ignored.
 *
 * Ordinarily the complement of the resulting code word is used for
 * transmission, and so the code word is complemented before it is returned.
 *
 * For further information see John C. Bellamy's Digital Telephony, 1982,
 * John Wiley & Sons, pps 98-111 and 472-476.
 */
unsigned char
linear2ulaw(
	int		pcm_val)	/* 2's complement (16-bit range) */
{
	int		mask;
	int		seg;
	unsigned char	uval;

	/* Get the sign and the magnitude of the value. */
	if (pcm_val < 0) {
		pcm_val = BIAS - pcm_val;
		mask = 0x7F;
	} else {
		pcm_val += BIAS;
		mask = 0xFF;
	}

	/* Convert the scaled magnitude to segment number. */
	seg = search(pcm_val, seg_end, 8);

	/*
	 * Combine the sign, segment, quantization bits;
	 * and complement the code word.
	 */
	if (seg >= 8)		/* out of range, return maximum value. */
		return (0x7F ^ mask);
	else {
		uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);
		return (uval ^ mask);
	}

}

/*
 * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
 *
 * First, a biased linear code is derived from the code word. An unbiased
 * output can then be obtained by subtracting 33 from the biased code.
 *
 * Note that this function expects to be passed the complement of the
 * original code word. This is in keeping with ISDN conventions.
 */
int
ulaw2linear(
	unsigned char	u_val)
{
	int		t;

	/* Complement to obtain normal u-law value. */
	u_val = ~u_val;

	/*
	 * Extract and bias the quantization bits. Then
	 * shift up by the segment number and subtract out the bias.
	 */
	t = ((u_val & QUANT_MASK) << 3) + BIAS;
	t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;

	return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
}

/* A-law to u-law conversion */
/* unsigned char
 * alaw2ulaw(
 * 	unsigned char	aval)
 * {
 * 	aval &= 0xff;
 * 	return ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :
 * 	    (0x7F ^ _a2u[aval ^ 0x55]));
 * }
 */

/* u-law to A-law conversion */
/* unsigned char
 * ulaw2alaw(
 * 	unsigned char	uval)
 * {
 * 	uval &= 0xff;
 * 	return ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :
 * 	    (0x55 ^ (_u2a[0x7F ^ uval] - 1)));
 * }
 */