/*
 * 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
 */

/*
 * g721.c
 *
 * Description:
 *
 * g721_encoder(), g721_decoder()
 *
 * These routines comprise an implementation of the CCITT G.721 ADPCM
 * coding algorithm.  Essentially, this implementation is identical to
 * the bit level description except for a few deviations which
 * take advantage of work station attributes, such as hardware 2's
 * complement arithmetic and large memory.  Specifically, certain time
 * consuming operations such as multiplications are replaced
 * with lookup tables and software 2's complement operations are
 * replaced with hardware 2's complement.
 *
 * The deviation from the bit level specification (lookup tables)
 * preserves the bit level performance specifications.
 *
 * As outlined in the G.721 Recommendation, the algorithm is broken
 * down into modules.  Each section of code below is preceded by
 * the name of the module which it is implementing.
 *
 */
#include "g72x.h"

static short qtab_721[7] = { -124, 80, 178, 246, 300, 349, 400};
/*
 * Maps G.721 code word to reconstructed scale factor normalized log
 * magnitude values.
 */
static short	_dqlntab[16] = { -2048, 4, 135, 213, 273, 323, 373, 425,
                              425, 373, 323, 273, 213, 135, 4, -2048};

/* Maps G.721 code word to log of scale factor multiplier. */
static short	_witab[16] = { -12, 18, 41, 64, 112, 198, 355, 1122,
                            1122, 355, 198, 112, 64, 41, 18, -12};
/*
 * Maps G.721 code words to a set of values whose long and short
 * term averages are computed and then compared to give an indication
 * how stationary (steady state) the signal is.
 */
static short	_fitab[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
                           0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};

/*
 * g721_encoder()
 *
 * Encodes the input vale of linear PCM, A-law or u-law data sl and returns
 * the resulting code. -1 is returned for unknown input coding value.
 */
int
g721_encoder(
    int	sl,
    int	in_coding,
    struct g72x_state *state_ptr)
{
    short	sezi, se, sez; 		/* ACCUM */
    short	d; 			/* SUBTA */
    short	sr; 			/* ADDB */
    short	y; 			/* MIX */
    short	dqsez; 			/* ADDC */
    short	dq, i;

    switch (in_coding)
    {	/* linearize input sample to 14-bit PCM */
        case AUDIO_ENCODING_ALAW:
        sl = alaw2linear(sl) >> 2;
        break;
        case AUDIO_ENCODING_ULAW:
        sl = ulaw2linear(sl) >> 2;
        break;
        case AUDIO_ENCODING_LINEAR:
        sl >>= 2; 			/* 14-bit dynamic range */
        break;
        default:
        return ( -1);
    }

    sezi = predictor_zero(state_ptr);
    sez = sezi >> 1;
    se = (sezi + predictor_pole(state_ptr)) >> 1; 	/* estimated signal */

    d = sl - se; 				/* estimation difference */

    /* quantize the prediction difference */
    y = step_size(state_ptr); 		/* quantizer step size */
    i = quantize(d, y, qtab_721, 7); 	/* i = ADPCM code */

    dq = reconstruct(i & 8, _dqlntab[i], y); 	/* quantized est diff */

    sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; 	/* reconst. signal */

    dqsez = sr + sez - se; 			/* pole prediction diff. */

    update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);

    return (i);
}

/*
 * g721_decoder()
 *
 * Description:
 *
 * Decodes a 4-bit code of G.721 encoded data of i and
 * returns the resulting linear PCM, A-law or u-law value.
 * return -1 for unknown out_coding value.
 */
int
g721_decoder(
    int	i,
    int	out_coding,
    struct g72x_state *state_ptr)
{
    short	sezi, sei, sez, se; 	/* ACCUM */
    short	y; 			/* MIX */
    short	sr; 			/* ADDB */
    short	dq;
    short	dqsez;

    i &= 0x0f; 			/* mask to get proper bits */
    sezi = predictor_zero(state_ptr);
    sez = sezi >> 1;
    sei = sezi + predictor_pole(state_ptr);
    se = sei >> 1; 			/* se = estimated signal */

    y = step_size(state_ptr); 	/* dynamic quantizer step size */

    dq = reconstruct(i & 0x08, _dqlntab[i], y);  /* quantized diff. */

    sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq; 	/* reconst. signal */

    dqsez = sr - se + sez; 			/* pole prediction diff. */

    update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);

    switch (out_coding)
    {
        case AUDIO_ENCODING_ALAW:
        return (tandem_adjust_alaw(sr, se, y, i, 8, qtab_721));
        case AUDIO_ENCODING_ULAW:
        return (tandem_adjust_ulaw(sr, se, y, i, 8, qtab_721));
        case AUDIO_ENCODING_LINEAR:
        return (sr << 2); 	/* sr was 14-bit dynamic range */
        default:
        return ( -1);
    }
}