soundchip.java

一个用java写成的gb模拟器的源代码。

/*

JavaBoy
                                  
COPYRIGHT (C) 2001 Neil Millstone and The Victoria University of Manchester
                                                                         ;;;
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.

*/

import javax.sound.sampled.AudioFormat;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.SourceDataLine;

/** This is the central controlling class for the sound.
 *  It interfaces with the Java Sound API, and handles the
 *  classes for each sound channel.
 */
class SoundChip {
	/** The DataLine for outputting the sound */
	SourceDataLine soundLine;

	SquareWaveGenerator channel1;
	SquareWaveGenerator channel2;
	VoluntaryWaveGenerator channel3;
	NoiseGenerator channel4;
	boolean soundEnabled = false;

	/** If true, channel is enabled */
	boolean channel1Enable = true,
		channel2Enable = true,
		channel3Enable = true,
		channel4Enable = true;

	/** Current sampling rate that sound is output at */
	int sampleRate = 44100;

	/** Amount of sound data to buffer before playback */
	int bufferLengthMsec = 200;

	/** Initialize sound emulation, and allocate sound hardware */
	public SoundChip() {
		soundLine = initSoundHardware();
		channel1 = new SquareWaveGenerator(sampleRate);
		channel2 = new SquareWaveGenerator(sampleRate);
		channel3 = new VoluntaryWaveGenerator(sampleRate);
		channel4 = new NoiseGenerator(sampleRate);
	}

	/** Initialize sound hardware if available */
	public SourceDataLine initSoundHardware() {

		try {
			AudioFormat format =
				new AudioFormat(
					AudioFormat.Encoding.PCM_SIGNED,
					sampleRate,
					8,
					2,
					2,
					sampleRate,
					true);
			DataLine.Info lineInfo =
				new DataLine.Info(SourceDataLine.class, format);

			if (!AudioSystem.isLineSupported(lineInfo)) {
				System.out.println("Error: Can't find audio output system!");
				soundEnabled = false;
			} else {
				SourceDataLine line =
					(SourceDataLine) AudioSystem.getLine(lineInfo);

				int bufferLength = (sampleRate / 1000) * bufferLengthMsec;
				line.open(format, bufferLength);
				line.start();
				//    System.out.println("Initialized audio successfully.");
				soundEnabled = true;
				return line;
			}
		} catch (Exception e) {
			System.out.println("Error: Audio system busy!");
			soundEnabled = false;
		}

		return null;
	}

	/** Change the sample rate of the playback */
	public void setSampleRate(int sr) {
		sampleRate = sr;

		soundLine.flush();
		soundLine.close();

		soundLine = initSoundHardware();

		channel1.setSampleRate(sr);
		channel2.setSampleRate(sr);
		channel3.setSampleRate(sr);
		channel4.setSampleRate(sr);
	}

	/** Change the sound buffer length */
	public void setBufferLength(int time) {
		bufferLengthMsec = time;

		soundLine.flush();
		soundLine.close();

		soundLine = initSoundHardware();
	}

	/** Adds a single frame of sound data to the buffer */
	public void outputSound() {
		if (soundEnabled) {
			int numSamples;

			if (sampleRate / 28 >= soundLine.available() * 2) {
				numSamples = soundLine.available() * 2;
			} else {
				numSamples = (sampleRate / 28) & 0xFFFE;
			}

			byte[] b = new byte[numSamples];
			if (channel1Enable)
				channel1.play(b, numSamples / 2, 0);
			if (channel2Enable)
				channel2.play(b, numSamples / 2, 0);
			if (channel3Enable)
				channel3.play(b, numSamples / 2, 0);
			if (channel4Enable)
				channel4.play(b, numSamples / 2, 0);
			soundLine.write(b, 0, numSamples);
		}
	}

}