LowPassComb.java

package jass.patches;
import jass.engine.*;
import jass.generators.*;

/** Delay line with a one pole low-pass. Used in Moorers reverb. See e.g.
    @book{Steiglitz96,
	title		= {A Digital Signal Processing Primer with
                          Applications to Digital Audio and Computer Music},
	author          =  {Ken Steiglitz},
	publisher	= {Addison-Wesley},
	address		= {New York},
	year		= {1996},
    pages = {290--295}}
    BUGS: Does not support removal of source.
    @author Kees van den Doel (kvdoel@cs.ubc.ca)
*/
public class LowPassComb extends InOut {

    protected float srate;
    protected float R=0; // feedback parameter
    protected float g=0; // low-pass parameter
    protected float del=0; // delay in seconds
    protected Mixer mixer;
    protected Delay delay;
    protected OnePoleLowPass lowpass;

    /** Create. For derived classes.
        @param bufferSize Buffer size used for real-time rendering.
     */
    public LowPassComb(int bufferSize) {
        super(bufferSize);
    }

    /** Create. For derived classes.
        @param bufferSize Buffer size used for real-time rendering.
        @param srate sampling rate in Hz
     */
    public LowPassComb(int bufferSize,float srate) {
        super(bufferSize);
        this.srate = srate;
        init();
    }

    /** Init and allocate.
     */
    protected void init() {
        mixer = new Mixer(bufferSize,2);
        delay = new Delay(bufferSize,srate);
        lowpass = new OnePoleLowPass(bufferSize);
        try {
            mixer.addSource(lowpass);
            lowpass.addSource(delay);
            delay.addSource(mixer);
        } catch(SinkIsFullException e) {
            System.out.println(this+" "+e);
        }
        long t = getTime();
        mixer.setTime(t);
        delay.setTime(t);
        lowpass.setTime(t);
    }
    
    /** Add source to Sink. Override to allow one input only and add to mixer
        @param s Source to add.
        @return object representing Source in Sink (may be null).
    */
    public Object addSource(Source s) throws SinkIsFullException {
        if(getSources().length > 0) {
            throw new SinkIsFullException();
        } else {
            mixer.addSource(s);
            mixer.setGain(1,1f);
            // add to Vector so that other  stuff like getSources will work
            // maybe not necessary??
            return super.addSource(s); 
        }
    }

    /** Set delay del. (=L/srate)
        @param del delay in seconds
     */
    public void setL(float del) throws IllegalArgumentException {
        this.del = del;
        delay.setRecursiveDelay(del);
    }
    
    /** Set feedback R.
        @param R feedback
     */
    public void setR(float R) {
        this.R = R;
        mixer.setGain(0,R); // 0 is the feedback input to the mixer
    }

    /** Set low-pass parameter g.
        @param g low-pass parameter g.
     */
    public void setG(float g) {
        this.g = g;
        lowpass.setG(g);
    }

    /** Compute the next buffer and store in member float[] buf.
     */
    protected void computeBuffer() {
        // Time has now been incremented and external Sources
        // have been called, but there are none since this has been
        // routed through the subpatch
        // Call getBuffer on the
        // contained subpatch. It will call getBuffer() on
        // atached Sources, but they are already at this time so will
        // just return their cached buffer. We are wasting only an extra method call.        
        try {
            buf = mixer.getBuffer(getTime());
        } catch(BufferNotAvailableException e) {
            System.out.println(this+" "+e);            
        }
    }

}