shithub: aacdec

ref: bca4f2b1da059fbf49a117f447b16b244fa7329a
dir: /libfaad/drc.c/

/*
** FAAD - Freeware Advanced Audio Decoder
** Copyright (C) 2002 M. Bakker
**  
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
** 
** 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 General Public License for more details.
** 
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software 
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
**
** $Id: drc.c,v 1.1 2002/01/14 19:15:55 menno Exp $
**/

#ifdef __ICL
#include <mathf.h>
#else
#include <math.h>
#endif
#include <memory.h>
#include "syntax.h"
#include "drc.h"

void init_drc(drc_info *drc, float cut, float boost)
{
    memset(drc, 0, sizeof(drc_info));

    drc->ctrl1 = cut;
    drc->ctrl2 = boost;

    drc->num_bands = 1;
    drc->band_top[0] = 1024/4 - 1;
    drc->dyn_rng_sgn[0] = 1;
    drc->dyn_rng_ctl[0] = 0;
}

void drc_decode(drc_info *drc, float *spec)
{
    int i, bd, top;
    float factor;
    int bottom = 0;

    if (drc->num_bands == 1)
        drc->band_top[0] = 1024/4 - 1;

    for (bd = 0; bd < drc->num_bands; bd++)
    {
        top = 4 * (drc->band_top[bd] + 1);

        /* Decode DRC gain factor */
        if (drc->dyn_rng_sgn[bd])  /* compress */
#ifdef __ICL
            factor = powf(2.0f, (-drc->ctrl1 * drc->dyn_rng_ctl[bd]/24.0f));
#else
            factor = (float)pow(2.0, (-drc->ctrl1 * drc->dyn_rng_ctl[bd]/24.0));
#endif
        else /* boost */
#ifdef __ICL
            factor = powf(2.0f, ( drc->ctrl2 * drc->dyn_rng_ctl[bd]/24.0f));
#else
            factor = (float)pow(2.0, ( drc->ctrl2 * drc->dyn_rng_ctl[bd]/24.0));
#endif

        /* Level alignment between different programs (if desired) */
        /* If program reference normalization is done in the digital domain,
           modify factor to perform normalization.
           prog_ref_level can alternatively be passed to the system for
           modification of the level in the analog domain. Analog level
           modification avoids problems with reduced DAC SNR (if signal is
           attenuated) or clipping (if signal is boosted)
         */
#ifdef __ICL
        factor *= powf(0.5f, ((DRC_REF_LEVEL - drc->prog_ref_level)/24.0f));
#else
        factor *= (float)pow(0.5, ((DRC_REF_LEVEL - drc->prog_ref_level)/24.0));
#endif

        /* Apply gain factor */
        for (i = bottom; i<top; i++)
            spec[i] *= factor;

        bottom = top;
    }
}