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/*
* @(#) synthesis_filter.h 1.8, last edit: 15 Jun 1994 16:52:00
* @(#) Copyright (C) 1993, 1994 Tobias Bading (bading@cs.tu-berlin.de)
* @(#) Berlin University of Technology
*
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef SYNTHESIS_FILTER_H
#define SYNTHESIS_FILTER_H
#include <iostream.h>
#include "all.h"
#include "obuffer.h"
// A class for the synthesis filter bank:
// This class does a fast downsampling from 32, 44.1 or 48 kHz to 8 kHz, if ULAW is defined.
// Frequencies above 4 kHz are removed by ignoring higher subbands.
class SynthesisFilter
{
static const real d[512];
real v1[512], v2[512];
real *actual_v; // v1 or v2
uint32 actual_write_pos; // 0-15
#ifdef ULAW
uint32 offset1, offset2; // number of samples to skip
uint32 remaining_offset; // number of samples still to skip when entering
// compute_pcm_samples() next time
uint32 highest_subband; // highest subband to use, e.g. 7 for 32 kHz to 8 kHz conversion
#endif
real samples[32]; // 32 new subband samples
uint32 channel;
real scalefactor;
uint32 range_violations;
real max_violation;
uint32 written_samples;
void compute_new_v (void);
void compute_pcm_samples (Obuffer *);
public:
#ifdef ULAW
SynthesisFilter (uint32 channelnumber, e_sample_frequency frequency,
real scalefactor = 32768.0);
// frequency specifies the sample rate of the stream.
#else
SynthesisFilter (uint32 channelnumber, real scalefactor = 32768.0);
#endif
// the scalefactor scales the calculated float pcm samples to short values
// (raw pcm samples are in [-1.0, 1.0], if no violations occur)
void input_sample (real sample, uint32 subbandnumber)
{
#ifdef DEBUG
if (subbandnumber > 31)
{
cerr << "SynthesisFilter::input_sample(): illegal subbandnumber!\n";
exit (1);
}
#endif
#ifdef ULAW
if (subbandnumber <= highest_subband)
samples[subbandnumber] = sample;
#else
samples[subbandnumber] = sample;
#endif
};
void calculate_pcm_samples (Obuffer *);
// calculate 32 PCM samples and put the into the Obuffer-object
uint32 violations (void) { return range_violations; }
real hardest_violation (void) { return max_violation; }
uint32 recommended_scalefactor (void) { return (uint32)(32768.0 / max_violation); }
real seconds_played (uint32 frequency)
{
return (real)written_samples / (real)frequency;
}
};
#endif
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