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	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	/*
	28	* g723_24.c
	29	*
	30	* Description:
	31	*
	32	* g723_24_encoder(), g723_24_decoder()
	33	*
	34	* These routines comprise an implementation of the CCITT G.723 24 Kbps
	35	* ADPCM coding algorithm. Essentially, this implementation is identical to
	36	* the bit level description except for a few deviations which take advantage
	37	* of workstation attributes, such as hardware 2's complement arithmetic.
	38	*
	39	*/
	40	#include <wx/wxprec.h>
	41	#include "g72x.h"
	42
	43	/*
	44	* Maps G.723_24 code word to reconstructed scale factor normalized log
	45	* magnitude values.
	46	*/
	47	static short _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048};
	48
	49	/* Maps G.723_24 code word to log of scale factor multiplier. */
	50	static short _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128};
	51
	52	/*
	53	* Maps G.723_24 code words to a set of values whose long and short
	54	* term averages are computed and then compared to give an indication
	55	* how stationary (steady state) the signal is.
	56	*/
	57	static short _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0};
	58
	59	static short qtab_723_24[3] = {8, 218, 331};
	60
	61	/*
	62	* g723_24_encoder()
	63	*
	64	* Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
	65	* Returns -1 if invalid input coding value.
	66	*/
	67	int
	68	g723_24_encoder(
	69	int sl,
	70	int in_coding,
	71	struct g72x_state *state_ptr)
	72	{
	73	short sei, sezi, se, sez; /* ACCUM */
	74	short d; /* SUBTA */
	75	short y; /* MIX */
	76	short sr; /* ADDB */
	77	short dqsez; /* ADDC */
	78	short dq, i;
	79
	80	switch (in_coding) { /* linearize input sample to 14-bit PCM */
	81	case AUDIO_ENCODING_ALAW:
	82	sl = alaw2linear(sl) >> 2;
	83	break;
	84	case AUDIO_ENCODING_ULAW:
	85	sl = ulaw2linear(sl) >> 2;
	86	break;
	87	case AUDIO_ENCODING_LINEAR:
	88	sl = ((short)sl) >> 2; /* sl of 14-bit dynamic range */
	89	break;
	90	default:
	91	return (-1);
	92	}
	93
	94	sezi = predictor_zero(state_ptr);
	95	sez = sezi >> 1;
	96	sei = sezi + predictor_pole(state_ptr);
	97	se = sei >> 1; /* se = estimated signal */
	98
	99	d = sl - se; /* d = estimation diff. */
	100
	101	/* quantize prediction difference d */
	102	y = step_size(state_ptr); /* quantizer step size */
	103	i = quantize(d, y, qtab_723_24, 3); /* i = ADPCM code */
	104	dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */
	105
	106	sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
	107
	108	dqsez = sr + sez - se; /* pole prediction diff. */
	109
	110	update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
	111
	112	return (i);
	113	}
	114
	115	/*
	116	* g723_24_decoder()
	117	*
	118	* Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
	119	* the resulting 16-bit linear PCM, A-law or u-law sample value.
	120	* -1 is returned if the output coding is unknown.
	121	*/
	122	int
	123	g723_24_decoder(
	124	int i,
	125	int out_coding,
	126	struct g72x_state *state_ptr)
	127	{
	128	short sezi, sei, sez, se; /* ACCUM */
	129	short y; /* MIX */
	130	short sr; /* ADDB */
	131	short dq;
	132	short dqsez;
	133
	134	i &= 0x07; /* mask to get proper bits */
	135	sezi = predictor_zero(state_ptr);
	136	sez = sezi >> 1;
	137	sei = sezi + predictor_pole(state_ptr);
	138	se = sei >> 1; /* se = estimated signal */
	139
	140	y = step_size(state_ptr); /* adaptive quantizer step size */
	141	dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
	142
	143	sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
	144
	145	dqsez = sr - se + sez; /* pole prediction diff. */
	146
	147	update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
	148
	149	switch (out_coding) {
	150	case AUDIO_ENCODING_ALAW:
	151	return (tandem_adjust_alaw(sr, se, y, i, 4, qtab_723_24));
	152	case AUDIO_ENCODING_ULAW:
	153	return (tandem_adjust_ulaw(sr, se, y, i, 4, qtab_723_24));
	154	case AUDIO_ENCODING_LINEAR:
	155	return (sr << 2); /* sr was of 14-bit dynamic range */
	156	default:
	157	return (-1);
	158	}
	159	}