/* * 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. *//* * December 30, 1994: * Functions linear2alaw, linear2ulaw have been updated to correctly * convert unquantized 16 bit values. * Tables for direct u- to A-law and A- to u-law conversions have been * corrected. * Borge Lindberg, Center for PersonKommunikation, Aalborg University. * bli@cpk.auc.dk * */ #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_aend[8] = {0x1F, 0x3F, 0x7F, 0xFF,			    0x1FF, 0x3FF, 0x7FF, 0xFFF};static short seg_uend[8] = {0x3F, 0x7F, 0xFF, 0x1FF,			    0x3FF, 0x7FF, 0xFFF, 0x1FFF};/* 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,/* corrected:	81,	82,	83,	84,	85,	86,	87,	88,    should be: */	80,	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,/* corrected:	73,	74,	75,	76,	77,	78,	79,	79,   should be: */	73,	74,	75,	76,	77,	78,	79,	80,	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 shortsearch(	short		val,	short		*table,	short		size){	short		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 charlinear2alaw(	short		pcm_val)	/* 2's complement (16-bit range) */{	short		mask;	short		seg;	unsigned char	aval;	pcm_val = pcm_val >> 3;	if (pcm_val >= 0) {		mask = 0xD5;		/* sign (7th) bit = 1 */	} else {		mask = 0x55;		/* sign bit = 0 */		pcm_val = -pcm_val - 1;	}	/* Convert the scaled magnitude to segment number. */	seg = search(pcm_val, seg_aend, 8);	/* Combine the sign, segment, and quantization bits. */	if (seg >= 8)		/* out of range, return maximum value. */		return (unsigned char) (0x7F ^ mask);	else {		aval = (unsigned char) seg << SEG_SHIFT;		if (seg < 2)			aval |= (pcm_val >> 1) & QUANT_MASK;		else			aval |= (pcm_val >> seg) & QUANT_MASK;		return (aval ^ mask);	}}/* * alaw2linear() - Convert an A-law value to 16-bit linear PCM * */shortalaw2linear(	unsigned char	a_val){	short		t;	short		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. */#define CLIP            8159/* * 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 charlinear2ulaw(	short		pcm_val)	/* 2's complement (16-bit range) */{	short		mask;	short		seg;	unsigned char	uval;	/* Get the sign and the magnitude of the value. */	pcm_val = pcm_val >> 2;	if (pcm_val < 0) {		pcm_val = -pcm_val;		mask = 0x7F;	} else {		mask = 0xFF;	}        if ( pcm_val > CLIP ) pcm_val = CLIP;		/* clip the magnitude */	pcm_val += (BIAS >> 2);	/* Convert the scaled magnitude to segment number. */	seg = search(pcm_val, seg_uend, 8);	/*	 * Combine the sign, segment, quantization bits;	 * and complement the code word.	 */	if (seg >= 8)		/* out of range, return maximum value. */		return (unsigned char) (0x7F ^ mask);	else {		uval = (unsigned char) (seg << 4) | ((pcm_val >> (seg + 1)) & 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. */shortulaw2linear(	unsigned char	u_val){	short		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 charalaw2ulaw(	unsigned char	aval){	aval &= 0xff;	return (unsigned char) ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :	    (0x7F ^ _a2u[aval ^ 0x55]));}/* u-law to A-law conversion */unsigned charulaw2alaw(	unsigned char	uval){	uval &= 0xff;	return (unsigned char) ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :	    (unsigned char) (0x55 ^ (_u2a[0x7F ^ uval] - 1)));}