javasoundgaincontrol.java

FMJ（freedom media for java)是java视频开发的新选择

package net.sf.fmj.media.renderer.audio;

import java.awt.Component;
import java.util.ArrayList;
import java.util.List;


import javax.media.GainChangeEvent;
import javax.media.GainChangeListener;
import javax.media.GainControl;
import javax.sound.sampled.BooleanControl;
import javax.sound.sampled.FloatControl;

/**
 * See Sun's javadoc for GainControl.
 * TODO: need to make sure we meet the requirements in the javadoc under the section "Decibel and Level Interactions".
 * @author Ken Larson
 *
 */
public class JavaSoundGainControl implements GainControl
{

	private final FloatControl masterGainControl;
	private final BooleanControl muteControl;
	private final float max; // max gain
	private final float min; // min gain
	private final float range; // max - min;
	private final boolean gainUnitsDb; // whether the underlying masterGainControl uses db for units.
	
	public JavaSoundGainControl(final FloatControl masterGainControl, final BooleanControl muteControl)
	{
		super();
		this.masterGainControl = masterGainControl;
		this.muteControl = muteControl;
		
		if (masterGainControl != null)
		{
			min = masterGainControl.getMinimum();
			max = masterGainControl.getMaximum();
			gainUnitsDb = masterGainControl.getUnits().equals("dB");	// a bit of a hack since we are effectively string-scraping here.
		}
		else
		{	min = max = 0.f;
			gainUnitsDb = false;
		}
		range = max - min;
	}

	// TODO: need a visual component.
//	private StandardGainControl standardGainControl;
	public Component getControlComponent()
	{
		return null;
//		if (standardGainControl == null)
//		{
//			standardGainControl = new StandardGainControl();
//			// TODO
//		}
//		
//		return standardGainControl.getControlComponent();
	}
	
	private final List listeners = new ArrayList();	// of GainChangeListener

	public void addGainChangeListener(GainChangeListener listener)
	{
		synchronized (listeners)
		{
			listeners.add(listener);
		}
	}

	public float getDB()
	{
		if (masterGainControl == null)
			return 0.f;

		if (gainUnitsDb)
			return masterGainControl.getValue();
		else
			return levelToDb(getLevel());

	}
	
	private static float levelToDb(float level)
	{
		return (float) (Math.log10(level) * 20.0);	// opposite of dBToLevel. 
	}
	
	private static float dBToLevel(float db)
	{
		return (float) Math.pow(10.0, db/20.0);	// from GainControl javadoc
	}

	/** Level is between 0 and 1 */
	public float getLevel()
	{
		if (masterGainControl == null)
			return 0.f;

		if (gainUnitsDb)
		{	return dBToLevel(masterGainControl.getValue());
		}
		else
		{
			float value = masterGainControl.getValue();
			return (value - min) / range;
		}
	}

	public boolean getMute()
	{
		if (muteControl == null)
			return false;
		return muteControl.getValue();
	}

	public void removeGainChangeListener(GainChangeListener listener)
	{
		synchronized (listeners)
		{
			listeners.remove(listener);
		}
		
	}
	
	private void notifyListenersGainChangeEvent()
	{
		final GainChangeEvent event = new GainChangeEvent(this, getMute(), getDB(), getLevel());
		notifyListenersGainChangeEvent(event);
	}
	
	private void notifyListenersGainChangeEvent(GainChangeEvent event)
	{
		final List listenersCopy = new ArrayList(); // of GainChangeListener
		
		synchronized (listeners)
		{
			listenersCopy.addAll(listeners);
		}
		
		for (int i = 0; i < listenersCopy.size(); ++i)
		{	final GainChangeListener listener = (GainChangeListener) listenersCopy.get(i);
			listener.gainChange(event);
		}
	}

	public float setDB(float gain)
	{
		if (masterGainControl == null)
			return 0.f;
		
		if (gainUnitsDb)
			masterGainControl.setValue(gain);
		else
			setLevel(dBToLevel(gain));	
		
		final float result = getDB();
		
		notifyListenersGainChangeEvent(); // TODO: don't notify if no change
		
		return result;
	}

	public float setLevel(float level)
	{
		if (masterGainControl == null)
			return 0.f;
		
		if (gainUnitsDb)
		{	masterGainControl.setValue(levelToDb(level));
		}
		else
		{
			level = min + level * range;
			masterGainControl.setValue(level);
		}
		
		float result = getLevel();
		
		notifyListenersGainChangeEvent(); // TODO: don't notify if no change

		return result;
	}

	public void setMute(boolean mute)
	{
		if (muteControl == null)
			return;
		
		muteControl.setValue(mute);
		
		notifyListenersGainChangeEvent(); // TODO: don't notify if no change

		
	}

}