/*
 * FAAC - Freeware Advanced Audio Coder
 * Copyright (C) 2001 Menno Bakker
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id: util.c,v 1.9 2001/06/08 18:01:09 menno Exp $
 */

#include <math.h>

#include "util.h"

/* Returns the sample rate index */
int GetSRIndex(unsigned int sampleRate)
{
    if (92017 <= sampleRate) return 0;
    if (75132 <= sampleRate) return 1;
    if (55426 <= sampleRate) return 2;
    if (46009 <= sampleRate) return 3;
    if (37566 <= sampleRate) return 4;
    if (27713 <= sampleRate) return 5;
    if (23004 <= sampleRate) return 6;
    if (18783 <= sampleRate) return 7;
    if (13856 <= sampleRate) return 8;
    if (11502 <= sampleRate) return 9;
    if (9391 <= sampleRate) return 10;

    return 11;
}

/* Returns the maximum bitrate per channel for that sampling frequency */
unsigned int MaxBitrate(unsigned long sampleRate)
{
    /*
     *  Maximum of 6144 bit for a channel
     */
    return (unsigned int)(6144.0 * (double)sampleRate/1024.0 + .5);
}

/* Returns the minimum bitrate per channel for that sampling frequency */
unsigned int MinBitrate()
{
    return 8000;
}


/* Max prediction band for backward predictionas function of fs index */
const int MaxPredSfb[] = { 33, 33, 38, 40, 40, 40, 41, 41, 37, 37, 37, 34, 0 };

int GetMaxPredSfb(int samplingRateIdx)
{
    return MaxPredSfb[samplingRateIdx];
}



/* Calculate bit_allocation based on PE */
unsigned int BitAllocation(double pe, int short_block)
{
    double pew1;
    double pew2;
    double bit_allocation;

    if (short_block) {
        pew1 = 0.6;
        pew2 = 24.0;
    } else {
        pew1 = 0.3;
        pew2 = 6.0;
    }
    bit_allocation = pew1 * pe + pew2 * sqrt(pe);
    bit_allocation = min(max(0.0, bit_allocation), 6144.0);

    return (unsigned int)(bit_allocation+0.5);
}

/* Returns the maximum bit reservoir size */
unsigned int MaxBitresSize(unsigned long bitRate, unsigned long sampleRate)
{
    return 6144 - (unsigned int)((double)bitRate/(double)sampleRate*1024.0);
}
