sine.h

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 */
 
#ifndef AUDIO_SINE_H
#define AUDIO_SINE_H
 
#include "audio/audiostream.h"
#include "common/util.h"
 
namespace Audio {
 
class SineStream : public AudioStream {
public:
    SineStream(int freq, int rate = 44100) {
        _rate = rate;
        _oscLength = rate / freq;
        _oscSamples = 0;
        _volume = 20; // The maximum volume is 255
    }
 
 
    int readBuffer(int16 *buffer, const int numSamples) override {
        for (int i = 0; i < numSamples; i++) {
            buffer[i] = generateSine(_oscSamples, _oscLength) * _volume;
            if (_oscSamples++ >= _oscLength)
                _oscSamples = 0;
        }
 
        return numSamples;
    }
 
    bool isStereo() const override { return false; }
    bool endOfData() const override { return false; }
    bool endOfStream() const override { return false; }
    int getRate() const override { return _rate; }
 
protected:
    int _rate;
    uint32 _oscLength;
    uint32 _oscSamples;
    byte _volume;
 
    int8 generateSine(uint32 x, uint32 oscLength) const {
        if (oscLength == 0)
            return 0;
 
        // TODO: Maybe using a look-up-table would be better?
        return CLIP<int16>((int16) (128 * sin(2.0 * M_PI * x / oscLength)), -128, 127);
    }
};
 
}
 
#endif