vgmstream/src/coding/g721_decoder.c

/* G.721 decoder, from Sun's public domain CCITT-ADPCM sources,
 * retrieved from ftp://ftp.cwi.nl/pub/audio/ccitt-adpcm.tar.gz
 *
 * For reference, here's the original license:
 *
 * 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 "g721_decoder.h"
#include "../util.h"

static short power2[15] = {1, 2, 4, 8, 0x10, 0x20, 0x40, 0x80,
                0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000};

/*
 * quan()
 *
 * quantizes the input val against the table of size short integers.
 * It returns i if table[i - 1] <= val < table[i].
 *
 * Using linear search for simple coding.
 */
static int
quan(
    int     val,
    short   *table,
    int     size)
{
    int     i;

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

/*
 * fmult()
 *
 * returns the integer product of the 14-bit integer "an" and
 * "floating point" representation (4-bit exponent, 6-bit mantessa) "srn".
 */
static int
fmult(
	int		an,
	int		srn)
{
	short		anmag, anexp, anmant;
	short		wanexp, wanmant;
	short		retval;

	anmag = (an > 0) ? an : ((-an) & 0x1FFF);
	anexp = quan(anmag, power2, 15) - 6;
	anmant = (anmag == 0) ? 32 :
	    (anexp >= 0) ? anmag >> anexp : anmag << -anexp;
	wanexp = anexp + ((srn >> 6) & 0xF) - 13;

	wanmant = (anmant * (srn & 077) + 0x30) >> 4;
	retval = (wanexp >= 0) ? ((wanmant << wanexp) & 0x7FFF) :
	    (wanmant >> -wanexp);

	return (((an ^ srn) < 0) ? -retval : retval);
}

/*
 * g72x_init_state()
 *
 * This routine initializes and/or resets the g72x_state structure
 * pointed to by 'state_ptr'.
 * All the initial state values are specified in the CCITT G.721 document.
 */
void
g72x_init_state(
	struct g72x_state *state_ptr)
{
	int		cnta;

	state_ptr->yl = 34816;
	state_ptr->yu = 544;
	state_ptr->dms = 0;
	state_ptr->dml = 0;
	state_ptr->ap = 0;
	for (cnta = 0; cnta < 2; cnta++) {
		state_ptr->a[cnta] = 0;
		state_ptr->pk[cnta] = 0;
		state_ptr->sr[cnta] = 32;
	}
	for (cnta = 0; cnta < 6; cnta++) {
		state_ptr->b[cnta] = 0;
		state_ptr->dq[cnta] = 32;
	}
	state_ptr->td = 0;
}

/*
 * predictor_zero()
 *
 * computes the estimated signal from 6-zero predictor.
 *
 */
int
predictor_zero(
	struct g72x_state *state_ptr)
{
	int		i;
	int		sezi;

	sezi = fmult(state_ptr->b[0] >> 2, state_ptr->dq[0]);
	for (i = 1; i < 6; i++)			/* ACCUM */
		sezi += fmult(state_ptr->b[i] >> 2, state_ptr->dq[i]);
	return (sezi);
}
/*
 * predictor_pole()
 *
 * computes the estimated signal from 2-pole predictor.
 *
 */
int
predictor_pole(
	struct g72x_state *state_ptr)
{
	return (fmult(state_ptr->a[1] >> 2, state_ptr->sr[1]) +
	    fmult(state_ptr->a[0] >> 2, state_ptr->sr[0]));
}
/*
 * step_size()
 *
 * computes the quantization step size of the adaptive quantizer.
 *
 */
int
step_size(
	struct g72x_state *state_ptr)
{
	int		y;
	int		dif;
	int		al;

	if (state_ptr->ap >= 256)
		return (state_ptr->yu);
	else {
		y = state_ptr->yl >> 6;
		dif = state_ptr->yu - y;
		al = state_ptr->ap >> 2;
		if (dif > 0)
			y += (dif * al) >> 6;
		else if (dif < 0)
			y += (dif * al + 0x3F) >> 6;
		return (y);
	}
}

/*
 * reconstruct()
 *
 * Returns reconstructed difference signal 'dq' obtained from
 * codeword 'i' and quantization step size scale factor 'y'.
 * Multiplication is performed in log base 2 domain as addition.
 */
int
reconstruct(
	int		sign,	/* 0 for non-negative value */
	int		dqln,	/* G.72x codeword */
	int		y)	/* Step size multiplier */
{
	short		dql;	/* Log of 'dq' magnitude */
	short		dex;	/* Integer part of log */
	short		dqt;
	short		dq;	/* Reconstructed difference signal sample */

	dql = dqln + (y >> 2);	/* ADDA */

	if (dql < 0) {
		return ((sign) ? -0x8000 : 0);
	} else {		/* ANTILOG */
		dex = (dql >> 7) & 15;
		dqt = 128 + (dql & 127);
		dq = (dqt << 7) >> (14 - dex);
		return ((sign) ? (dq - 0x8000) : dq);
	}
}


/*
 * update()
 *
 * updates the state variables for each output code
 */
void
update(
	/*int		code_size,*/	/* distinguish 723_40 with others */
	int		y,		/* quantizer step size */
	int		wi,		/* scale factor multiplier */
	int		fi,		/* for long/short term energies */
	int		dq,		/* quantized prediction difference */
	int		sr,		/* reconstructed signal */
	int		dqsez,		/* difference from 2-pole predictor */
	struct g72x_state *state_ptr)	/* coder state pointer */
{
	int		cnt;
	short		mag, exp;	/* Adaptive predictor, FLOAT A */
	short		a2p;		/* LIMC */
	short		a1ul;		/* UPA1 */
	short		pks1;	/* UPA2 */
	short		fa1;
	char		tr;		/* tone/transition detector */
	short		ylint, thr2, dqthr;
	short  		ylfrac, thr1;
	short		pk0;

	pk0 = (dqsez < 0) ? 1 : 0;	/* needed in updating predictor poles */

	mag = dq & 0x7FFF;		/* prediction difference magnitude */
	/* TRANS */
	ylint = state_ptr->yl >> 15;	/* exponent part of yl */
	ylfrac = (state_ptr->yl >> 10) & 0x1F;	/* fractional part of yl */
	thr1 = (32 + ylfrac) << ylint;		/* threshold */
	thr2 = (ylint > 9) ? 31 << 10 : thr1;	/* limit thr2 to 31 << 10 */
	dqthr = (thr2 + (thr2 >> 1)) >> 1;	/* dqthr = 0.75 * thr2 */
	if (state_ptr->td == 0)		/* signal supposed voice */
		tr = 0;
	else if (mag <= dqthr)		/* supposed data, but small mag */
		tr = 0;			/* treated as voice */
	else				/* signal is data (modem) */
		tr = 1;

	/*
	 * Quantizer scale factor adaptation.
	 */

	/* FUNCTW & FILTD & DELAY */
	/* update non-steady state step size multiplier */
	state_ptr->yu = y + ((wi - y) >> 5);

	/* LIMB */
	if (state_ptr->yu < 544)	/* 544 <= yu <= 5120 */
		state_ptr->yu = 544;
	else if (state_ptr->yu > 5120)
		state_ptr->yu = 5120;

	/* FILTE & DELAY */
	/* update steady state step size multiplier */
	state_ptr->yl += state_ptr->yu + ((-state_ptr->yl) >> 6);

	/*
	 * Adaptive predictor coefficients.
	 */
	if (tr == 1) {			/* reset a's and b's for modem signal */
		state_ptr->a[0] = 0;
		state_ptr->a[1] = 0;
		state_ptr->b[0] = 0;
		state_ptr->b[1] = 0;
		state_ptr->b[2] = 0;
		state_ptr->b[3] = 0;
		state_ptr->b[4] = 0;
		state_ptr->b[5] = 0;
        a2p=0;          /* won't be used, clear warning */
	} else {			/* update a's and b's */
		pks1 = pk0 ^ state_ptr->pk[0];		/* UPA2 */

		/* update predictor pole a[1] */
		a2p = state_ptr->a[1] - (state_ptr->a[1] >> 7);
		if (dqsez != 0) {
			fa1 = (pks1) ? state_ptr->a[0] : -state_ptr->a[0];
			if (fa1 < -8191)	/* a2p = function of fa1 */
				a2p -= 0x100;
			else if (fa1 > 8191)
				a2p += 0xFF;
			else
				a2p += fa1 >> 5;

			if (pk0 ^ state_ptr->pk[1])
				/* LIMC */
				if (a2p <= -12160)
					a2p = -12288;
				else if (a2p >= 12416)
					a2p = 12288;
				else
					a2p -= 0x80;
			else if (a2p <= -12416)
				a2p = -12288;
			else if (a2p >= 12160)
				a2p = 12288;
			else
				a2p += 0x80;
		}

		/* TRIGB & DELAY */
		state_ptr->a[1] = a2p;

		/* UPA1 */
		/* update predictor pole a[0] */
		state_ptr->a[0] -= state_ptr->a[0] >> 8;
		if (dqsez != 0) {
			if (pks1 == 0)
				state_ptr->a[0] += 192;
			else
				state_ptr->a[0] -= 192;
        }

		/* LIMD */
		a1ul = 15360 - a2p;
		if (state_ptr->a[0] < -a1ul)
			state_ptr->a[0] = -a1ul;
		else if (state_ptr->a[0] > a1ul)
			state_ptr->a[0] = a1ul;

		/* UPB : update predictor zeros b[6] */
		for (cnt = 0; cnt < 6; cnt++) {
			/*if (code_size == 5)*/		/* for 40Kbps G.723 */
			/*	state_ptr->b[cnt] -= state_ptr->b[cnt] >> 9;*/
			/*else*/			/* for G.721 and 24Kbps G.723 */
				state_ptr->b[cnt] -= state_ptr->b[cnt] >> 8;
			if (dq & 0x7FFF) {			/* XOR */
				if ((dq ^ state_ptr->dq[cnt]) >= 0)
					state_ptr->b[cnt] += 128;
				else
					state_ptr->b[cnt] -= 128;
			}
		}
	}

	for (cnt = 5; cnt > 0; cnt--)
		state_ptr->dq[cnt] = state_ptr->dq[cnt-1];
	/* FLOAT A : convert dq[0] to 4-bit exp, 6-bit mantissa f.p. */
	if (mag == 0) {
		state_ptr->dq[0] = (dq >= 0) ? 0x20 : 0xFC20;
	} else {
		exp = quan(mag, power2, 15);
		state_ptr->dq[0] = (dq >= 0) ?
		    (exp << 6) + ((mag << 6) >> exp) :
		    (exp << 6) + ((mag << 6) >> exp) - 0x400;
	}

	state_ptr->sr[1] = state_ptr->sr[0];
	/* FLOAT B : convert sr to 4-bit exp., 6-bit mantissa f.p. */
	if (sr == 0) {
		state_ptr->sr[0] = 0x20;
	} else if (sr > 0) {
		exp = quan(sr, power2, 15);
		state_ptr->sr[0] = (exp << 6) + ((sr << 6) >> exp);
	} else if (sr > -32768) {
		mag = -sr;
		exp = quan(mag, power2, 15);
		state_ptr->sr[0] =  (exp << 6) + ((mag << 6) >> exp) - 0x400;
	} else
		state_ptr->sr[0] = 0xFC20;

	/* DELAY A */
	state_ptr->pk[1] = state_ptr->pk[0];
	state_ptr->pk[0] = pk0;

	/* TONE */
	if (tr == 1)		/* this sample has been treated as data */
		state_ptr->td = 0;	/* next one will be treated as voice */
	else if (a2p < -11776)	/* small sample-to-sample correlation */
		state_ptr->td = 1;	/* signal may be data */
	else				/* signal is voice */
		state_ptr->td = 0;

	/*
	 * Adaptation speed control.
	 */
	state_ptr->dms += (fi - state_ptr->dms) >> 5;		/* FILTA */
	state_ptr->dml += (((fi << 2) - state_ptr->dml) >> 7);	/* FILTB */

	if (tr == 1)
		state_ptr->ap = 256;
	else if (y < 1536)					/* SUBTC */
		state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
	else if (state_ptr->td == 1)
		state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
	else if (abs((state_ptr->dms << 2) - state_ptr->dml) >=
	    (state_ptr->dml >> 3))
		state_ptr->ap += (0x200 - state_ptr->ap) >> 4;
	else
		state_ptr->ap += (-state_ptr->ap) >> 4;
}

/*
 * 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_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,
	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(y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);

	return (sr << 2);	/* sr was 14-bit dynamic range */
}

void decode_g721(VGMSTREAMCHANNEL * stream, sample * outbuf, int channelspacing, int32_t first_sample, int32_t samples_to_do) {
    int i;
    int32_t sample_count;

    for (i=first_sample,sample_count=0; i<first_sample+samples_to_do; i++,sample_count+=channelspacing) {
        outbuf[sample_count]=
            g721_decoder(
            read_8bit(stream->offset+i/2,stream->streamfile)>>(i&1?4:0),
            &(stream->g72x_state)
            );
    }
}