File: synthesis_filter.h

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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