g711.c

g729 coding ipaddressing

/*
 * 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
 */

/*
 * 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. */

#ifdef NEEDED

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};
#endif

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};

#ifdef NEEDED
static int
search(val, table, size)
		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(pcm_val)
        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(a_val)
		unsigned char	a_val;
{
		int 			t;
		int 			seg;

		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;
		}
		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(pcm_val)
        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(u_val)
		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;
ed s
		return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
}
#endif

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

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