Logo Search packages:      
Sourcecode: scummvm version File versions

emumidi.h

/* ScummVM - Scumm Interpreter
 * Copyright (C) 2001-2004 The ScummVM project
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * $Header: /cvsroot/scummvm/scummvm/backends/midi/Attic/emumidi.h,v 1.7 2004/11/27 13:54:08 fingolfin Exp $
 */

#include "stdafx.h"
#include "sound/audiostream.h"
#include "sound/mididrv.h"
#include "sound/mixer.h"

#define FIXP_SHIFT 16

class MidiDriver_Emulated : public AudioStream, public MidiDriver {
protected:
      bool _isOpen;
      SoundMixer *_mixer;

private:
      Timer::TimerProc _timerProc;
      void *_timerParam;

      int _nextTick;
      int _samplesPerTick;

protected:
      virtual void generateSamples(int16 *buf, int len) = 0;
      virtual void onTimer() {}

      int _baseFreq;

public:
      MidiDriver_Emulated(SoundMixer *mixer) : _mixer(mixer) {
            _isOpen = false;
      
            _timerProc = 0;
            _timerParam = 0;
      
            _nextTick = 0;
            _samplesPerTick = 0;

            _baseFreq = 250;
      }

      int open() {
            _isOpen = true;

            int d = getRate() / _baseFreq;
            int r = getRate() % _baseFreq;

            // This is equivalent to (getRate() << FIXP_SHIFT) / BASE_FREQ
            // but less prone to arithmetic overflow.

            _samplesPerTick = (d << FIXP_SHIFT) + (r << FIXP_SHIFT) / _baseFreq;
            return 0;
      }

      void setTimerCallback(void *timer_param, Timer::TimerProc timer_proc) {
            _timerProc = timer_proc;
            _timerParam = timer_param;
      }

      uint32 getBaseTempo() { return 1000000 / _baseFreq; }


      // AudioStream API
      int readBuffer(int16 *data, const int numSamples) {
            const int stereoFactor = isStereo() ? 2 : 1;
            int len = numSamples / stereoFactor;
            int step;

            do {
                  step = len;
                  if (step > (_nextTick >> FIXP_SHIFT))
                        step = (_nextTick >> FIXP_SHIFT);

                  generateSamples(data, step);
      
                  _nextTick -= step << FIXP_SHIFT;
                  if (!(_nextTick >> FIXP_SHIFT)) {
                        if (_timerProc)
                              (*_timerProc)(_timerParam);
                        onTimer();
                        _nextTick += _samplesPerTick;
                  }
                  data += step * stereoFactor;
                  len -= step;
            } while (len);

            return numSamples;
      }
      bool endOfData() const { return false; }
};

Generated by  Doxygen 1.6.0   Back to index