g72x.cpp

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/*
 * 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
 */

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

#include "wx/wxprec.h"
#include <stdlib.h>
#include "wx/mmedia/internal/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 int
quan(
    int           val,
    short        *table,
    int           size)
{
    int i;

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

static char quan2_tab[65536];
static short base2_tab[65536];
static int init_tabs_done = 0;

inline char quan2 (unsigned short val)
{
    return quan2_tab[val];
}

inline short base2 (unsigned short val)
{
    return base2_tab[val];
}

static void init_quan2_tab (void)
{
    long i;

    for (i = 0; i < 65536; i++) {
        quan2_tab[i] = quan (i, power2, 15);
    };
}

static void init_base2_tab (void)
{
    long i;
    short exp;

    for (i = 0; i < 65536; i++) {
        exp = quan2 (short (i));
        base2_tab[i] = short ((exp << 6) + ((i << 6) >> exp));
    };
}

static void init_tabs (void)
{
    if (init_tabs_done) return;

    init_quan2_tab();
    init_base2_tab();

    init_tabs_done = 1;
}

/*
 * 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 = quan2(anmag) - 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;

    init_tabs ();

    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);
    }
}

/*
 * 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.
 */
int
quantize(
    int        d,        /* Raw difference signal sample */
    int        y,        /* Step size multiplier */
    short     *table,    /* quantization table */
    int        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 = quan2(dqm >> 1);
    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.
 */
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);
    }
}