96 lines
2.7 KiB
C
96 lines
2.7 KiB
C
/*
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* FAAC - Freeware Advanced Audio Coder
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* Copyright (C) 2001 Menno Bakker
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* $Id: util.c,v 1.10 2005/02/02 07:56:33 sur Exp $
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*/
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#include <math.h>
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#include "util.h"
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#include "coder.h" // FRAME_LEN
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/* Returns the sample rate index */
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int GetSRIndex(unsigned int sampleRate)
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{
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if (92017 <= sampleRate) return 0;
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if (75132 <= sampleRate) return 1;
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if (55426 <= sampleRate) return 2;
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if (46009 <= sampleRate) return 3;
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if (37566 <= sampleRate) return 4;
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if (27713 <= sampleRate) return 5;
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if (23004 <= sampleRate) return 6;
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if (18783 <= sampleRate) return 7;
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if (13856 <= sampleRate) return 8;
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if (11502 <= sampleRate) return 9;
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if (9391 <= sampleRate) return 10;
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return 11;
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}
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/* Returns the maximum bitrate per channel for that sampling frequency */
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unsigned int MaxBitrate(unsigned long sampleRate)
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{
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/*
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* Maximum of 6144 bit for a channel
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*/
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return (unsigned int)(6144.0 * (double)sampleRate/(double)FRAME_LEN + .5);
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}
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/* Returns the minimum bitrate per channel for that sampling frequency */
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unsigned int MinBitrate()
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{
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return 8000;
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}
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/* Max prediction band for backward predictionas function of fs index */
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const int MaxPredSfb[] = { 33, 33, 38, 40, 40, 40, 41, 41, 37, 37, 37, 34, 0 };
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int GetMaxPredSfb(int samplingRateIdx)
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{
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return MaxPredSfb[samplingRateIdx];
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}
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/* Calculate bit_allocation based on PE */
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unsigned int BitAllocation(double pe, int short_block)
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{
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double pew1;
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double pew2;
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double bit_allocation;
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if (short_block) {
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pew1 = 0.6;
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pew2 = 24.0;
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} else {
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pew1 = 0.3;
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pew2 = 6.0;
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}
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bit_allocation = pew1 * pe + pew2 * sqrt(pe);
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bit_allocation = min(max(0.0, bit_allocation), 6144.0);
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return (unsigned int)(bit_allocation+0.5);
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}
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/* Returns the maximum bit reservoir size */
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unsigned int MaxBitresSize(unsigned long bitRate, unsigned long sampleRate)
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{
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return 6144 - (unsigned int)((double)bitRate/(double)sampleRate*(double)FRAME_LEN);
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}
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