g72x.c

dm642上的h264源码

/*
 * g72x.c
 *
 * Common routines for G.721 and G.723 conversions.
 */

#include "g72x.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 short
quan(
	short		val,
	short		*table,
	short		size)
{
	short		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 short
fmult(
	short		an,
	short		srn)
{
	short		anmag, anexp, anmant;
	short		wanexp,  wanmant;//wanmag,
	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->yu = 544;

	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;
	}

}

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

/*
 * quantize()
 *
 * Given a raw sample, 'd', of the difference signal and a
 * quantization step size scale factor, 'y', this routine returns the
 * ADPCM codeword to which that sample gets quantized.  The step
 * size scale factor division operation is done in the log base 2 domain
 * as a subtraction.
 */
short
quantize(
	short		d,	/* Raw difference signal sample */
	short		y,	/* Step size multiplier */
	short		*table,	/* quantization table */
	short		size)	/* table size of short integers */
{
	short		dqm;	/* Magnitude of 'd' */
	short		exp;	/* Integer part of base 2 log of 'd' */
	short		mant;	/* Fractional part of base 2 log */
	short		dl;	/* Log of magnitude of 'd' */
	short		dln;	/* Step size scale factor normalized log */
	int		i;

	/*
	 * LOG
	 *
	 * Compute base 2 log of 'd', and store in 'dl'.
	 */
	dqm = abs(d);
	exp = quan(dqm >> 1, power2, 15);
	mant = ((dqm << 7) >> exp) & 0x7F;	/* Fractional portion. */
	dl = (exp << 7) + mant;

	/*
	 * SUBTB
	 *
	 * "Divide" by step size multiplier.
	 */
	dln = dl - (y >> 2);

	/*
	 * QUAN
	 *
	 * Obtain codword i for 'd'.
	 */
	i = quan(dln, table, size);
	if (d < 0)			/* take 1's complement of i */
		return ((size << 1) + 1 - i);
	else if (i == 0)		/* take 1's complement of 0 */
		return ((size << 1) + 1); /* new in 1988 */
	else
		return (i);
}
/*
 * 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.
 */
short
reconstruct(
	short		sign,	/* 0 for non-negative value */
	short		dqln,	/* G.72x codeword */
	short		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(
	short		y,		/* quantizer step size */
	short		wi,		/* scale factor multiplier */
	short		dq,		/* quantized prediction difference */
	short		sr,		/* reconstructed signal */
	short		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;
	short		pk0;

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

	mag = dq & 0x7FFF;		/* prediction difference magnitude */


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

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


	/*
	 * Adaptive predictor coefficients.
	 */
	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++) {
		/* 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;

}