/*
 * broadvoice - a library for the BroadVoice 16 and 32 codecs
 *
 * bv16gainquan.c - Gain quantization based on inter-subframe
 *                  moving-average prediction of logarithmic gain.
 *
 * Adapted by Steve Underwood <steveu@coppice.org> from code which is
 * Copyright 2000-2009 Broadcom Corporation
 *
 * All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 2.1,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id: bv16gainquan.c,v 1.1.1.1 2009/11/19 12:10:48 steveu Exp $
 */

/*! \file */

#if defined(HAVE_CONFIG_H)
#include "config.h"
#endif

#include <math.h>
#include "typedef.h"
#include "bv16externs.h"

int gainquan(Float *gainq,
             Float lg,
             Float *lgpm,
             Float *prevlg,        /* previous log gains (last two frames) */
             Float level)
{
    Float elg;
    Float lgpe;
    Float limit;
    Float dmin;
    Float d;
    int i;
    int n;
    int gidx = 0;
    const int *p_gidx;

    /* Calculate estimated log-gain */
    elg = bv16_lgmean;
    for (i = 0;  i < LGPORDER;  i++)
        elg += bv16_lgp[i]*lgpm[i];

    /* subtract log-gain mean & estimated log-gain to get prediction error */
    lgpe = lg - elg;

    /* scalar quantization of log-gain prediction error */
    dmin = 1e30;
    p_gidx = bv16_idxord;
    for (i = 0; i < LGPECBSZ; i++)
    {
        d = lgpe - bv16_lgpecb[*p_gidx++];
        if (d < 0.0F)
            d = -d;
        if (d < dmin)
        {
            dmin = d;
            gidx = i;
        }
    }

    /* calculate quantized log-gain */
    *gainq = bv16_lgpecb[bv16_idxord[gidx]] + elg;

    /* look up from lgclimit() table the maximum log gain change allowed */
    i = (int) ((prevlg[0] - level - LGLB)*0.5F); /* get column index */
    if (i >= NGB)
    {
        i = NGB - 1;
    }
    else if (i < 0)
    {
        i = 0;
    }
    n = (int) ((prevlg[0] - prevlg[1] - LGCLB) * 0.5F);  /* get row index */
    if (n >= NGCB)
    {
        n = NGCB - 1;
    }
    else if (n < 0)
    {
        n = 0;
    }
    i = i * NGCB + n;

    /* check whether quantized log-gain cause a gain change > lgclimit */
    limit = prevlg[0] + bv16_lgclimit[i];/* limit that log-gain shouldn't exceed */
    while ((*gainq > limit)  &&  (gidx > 0))   /* if q log-gain exceeds limit */
    {
        gidx -= 1;     /* decrement gain quantizer index by 1 */
        *gainq = bv16_lgpecb[bv16_idxord[gidx]] + elg; /* use next quantizer output*/
    }

    /* Get true codebook index */
    gidx = bv16_idxord[gidx];

    /* update log-gain predictor memory */
    prevlg[1] = prevlg[0];
    prevlg[0] = *gainq;
    for (i = LGPORDER - 1;  i > 0;  i--)
        lgpm[i] = lgpm[i - 1];
    lgpm[0] = bv16_lgpecb[gidx];

    /* convert quantized log-gain to linear domain */
    *gainq = pow(2.0F, 0.5F * *gainq);

    return gidx;
}