AppleIIGo/Source/AppleSpeaker.java

/**
 * AppleIIGo
 * Speaker processing
 * (C) 2006 by Marc S. Ressl(ressl@lonetree.com)
 * Released under the GPL
 */

import javax.sound.sampled.*;

public class AppleSpeaker implements Runnable {
	// Instances of other classes
    private EmAppleII apple;

	// Refresh
	private int refreshRate;
	private long refreshInterval;

	// Sound stuff
	private static final int SPEAKER_BITS = 16;
	private static final int SPEAKER_SAMPLERATE = 44100;
	private static final int SPEAKER_CHANNELS = 1;
	private static final int SPEAKER_SAMPLESIZE = (SPEAKER_BITS * SPEAKER_CHANNELS / 8);
	private static final boolean SPEAKER_SIGNED = true;
	private static final boolean SPEAKER_BIGENDIAN = false;
	
	private int clock, clockNextFlip, clockEnd;
	private boolean isFlipsBufferEmpty = true;

	private SourceDataLine line;

	private int bufferSamples;
	private int bufferSize;
	private byte[] buffer;
	
	private int speakerVolume;
	private int speakerFlipsPointer;
	private int speakerFlipState;

	private int[] speakerFlipStateToVolume = new int[2];
	private int speakerClocksPerSample;

	// Thread stuff
	private boolean isPaused = true;
	private Thread thread;
	private String threadError = null;


	
    public AppleSpeaker(EmAppleII apple) {
		this.apple = apple;

		setVolume(4);
	}

	/**
	 * Set refresh rate
	 *
	 * @param	value	Speaker refresh rate in mHz
	 */
	private void setRefreshRate(int value) {
		if (value <= 0.0f)
			return;
			
		this.refreshRate = value;
		refreshInterval = (int) (1000.0 / value);

		speakerClocksPerSample = (int) (apple.getCpuSpeed() * 1000.0f / SPEAKER_SAMPLERATE);
    }
	
	/**
	 * Get refresh rate
	 */
	private int getRefreshRate() {
		return refreshRate;
    }
	
	/**
	 * Set speaker volume
	 */
	public void setVolume(int value) {
		if ((value < 0) || (value > 7))
			return;
		
		speakerVolume = value;

		int absVolume = 1 << (value + 8);
		speakerFlipStateToVolume[0] = -absVolume;
		speakerFlipStateToVolume[1] = absVolume;
	}
	
	/**
	 * Get speaker volume
	 */
	public int getVolume() {
		return speakerVolume;
    }
	
	/**
	 * Set pause state
	 */
	public void setPaused(boolean value) {
		if (isPaused == value)
			return;

		isPaused = value;
		if (isPaused) {
			try {
				thread.join(1000);
			} catch (InterruptedException e) {
			}
			if (line != null) {
				line.stop();
				line.close();				
			}
		} else {
			setRefreshRate(apple.getRefreshRate());
			
			AudioFormat	audioFormat = new AudioFormat(
				SPEAKER_SAMPLERATE,
				SPEAKER_BITS,
				SPEAKER_CHANNELS,
				SPEAKER_SIGNED,
				SPEAKER_BIGENDIAN);

			DataLine.Info info = new DataLine.Info(
				DataLine.class,
				audioFormat);

			try {
				line = (SourceDataLine) AudioSystem.getLine(info);
				bufferSize = line.getBufferSize();
				bufferSamples = bufferSize / SPEAKER_SAMPLESIZE;

				buffer = new byte[bufferSize];

				line.open(audioFormat);
				line.start();
			} catch (LineUnavailableException e) {
			}

			thread = new Thread(this);
			thread.start();
		}
	}

	/**
	 * Speaker refresh thread
	 */
    public void run() {
		try {
			while (!isPaused) {
				long refreshStart = System.currentTimeMillis();
				long refreshDelay;

				refreshSpeaker();

				refreshDelay = System.currentTimeMillis() - refreshStart;

				if (refreshDelay < refreshInterval)
					Thread.sleep(refreshInterval - refreshDelay);
			}
		} catch (InterruptedException e) {
		};
	}



	/**
	 * Speaker refresh
	 */
    private void refreshSpeaker() {
		clockEnd = apple.clock;
		int bytes;
	
		if (line == null)
			return;

		while ((bytes = fillBuffer()) > 0) {
			line.write(buffer, 0, bytes);
		}
	}

	/**
	 * Fill buffer
	 */
    private int fillBuffer() {
		int value = speakerFlipStateToVolume[speakerFlipState];
		int clockEndSample = clockEnd - speakerClocksPerSample;
		int bufferPointer = 0;

		initNextFlip();
		while (bufferPointer < bufferSize) {
			if (clockEndSample == clock)
				break;

			if (((clockEndSample - clock) & 0x7fffffff) > 0x3fffffff)
				break;

			// Find all flips on current sample
			while (((clockNextFlip - clock) & 0x7fffffff) < speakerClocksPerSample) {
				getNextFlip();
				speakerFlipState = (speakerFlipState ^ 1);
				value = speakerFlipStateToVolume[speakerFlipState];
			}

			// Write sample
			buffer[bufferPointer] = (byte) (value & 0xff);
			buffer[bufferPointer + 1] = (byte) (value >> 8);
			bufferPointer += SPEAKER_SAMPLESIZE;
			
			clock += speakerClocksPerSample;
		}

		return bufferPointer;
	}

	/**
	 * Reset next flip
	 */
	private void initNextFlip() {
		if (isFlipsBufferEmpty) {
			isFlipsBufferEmpty = false;
			getNextFlip();
		}
	}

	/**
	 * Gets next flip
	 */
	private void getNextFlip() {
		if (speakerFlipsPointer == apple.speakerFlipsPointer) {
			clockNextFlip = clock + 0x3fffffff;
			isFlipsBufferEmpty = true;
		} else {
			clockNextFlip = apple.speakerFlips[speakerFlipsPointer];
			speakerFlipsPointer = (speakerFlipsPointer + 1) & apple.SPEAKER_FLIPS_MASK;
		}
	}
}