ref: 296859b23f5e255ab60ea60f59dac5860d2f7c04
dir: /libfaac/util.c/
/*
* 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);
}