DSP Engine from Ethereal Dialpad

Dac.java

package as.adamsmith.etherealdialpad.dsp;

import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;


public class Dac extends UGen {
	private final float[] localBuffer;
	private boolean isClean;
	private final AudioTrack track;
	private final short [] target = new short[UGen.CHUNK_SIZE];
	private final short [] silentTarget = new short[UGen.CHUNK_SIZE];
	
	public Dac() {
		localBuffer = new float[CHUNK_SIZE];
		
		int minSize = AudioTrack.getMinBufferSize(
				UGen.SAMPLE_RATE,
				AudioFormat.CHANNEL_CONFIGURATION_MONO,
        		AudioFormat.ENCODING_PCM_16BIT);
		
		track = new AudioTrack(
        		AudioManager.STREAM_MUSIC,
        		UGen.SAMPLE_RATE,
        		AudioFormat.CHANNEL_CONFIGURATION_MONO,
        		AudioFormat.ENCODING_PCM_16BIT,
        		Math.max(UGen.CHUNK_SIZE*4, minSize),
        		AudioTrack.MODE_STREAM);
	}
	
	public boolean render(final float[] _buffer) {
		if(!isClean) {
			zeroBuffer(localBuffer);

			isClean = true;
		}
		// localBuffer is always clean right here, does it stay that way?
		isClean = !renderKids(localBuffer);
		return !isClean; // we did some work if the buffer isn't clean
	}
	
	public void open() {
		track.play();
	}
	
	public void tick() {
		
		render(localBuffer);
		
		if(isClean) {
			// sleeping is messy, so lets just queue this silent buffer
			track.write(silentTarget, 0, silentTarget.length);
		} else {
			for(int i = 0; i < CHUNK_SIZE; i++) {
				target[i] = (short)(32768.0f*localBuffer[i]);
			}
			
			track.write(target, 0, target.length);
		}
	}
	
	public void close() {
		track.stop();
        track.release();
	}
}

Delay.java

package as.adamsmith.etherealdialpad.dsp;

public class Delay extends UGen {
	final float[] line;
	int pointer;
	
	public Delay(int length) {
		super();
		line = new float[length];
	}
	
	public boolean render(final float[] buffer) {
		renderKids(buffer);
		
		final float[] localLine = line;
		final int lineLength = line.length;
		for(int i = 0; i < CHUNK_SIZE; i++) {
			buffer[i] = buffer[i] - 0.5f*localLine[pointer];
			localLine[pointer] = buffer[i];
			pointer = (pointer+1)%lineLength;
		}
		
		// ugh, looks like we can never be sure it's silent
		// without checking every sample because of the feedback
		return true; 
	}
}

ExpEnv.java

package as.adamsmith.etherealdialpad.dsp;

public class ExpEnv extends UGen {
	
	public static float hardFactor = 0.005f;
	public static float softFactor = 0.00005f;
	
	boolean state;
	float attenuation;
	float factor = softFactor;
	final float idealMarker = 0.25f;
	float marker = idealMarker;
	
	public synchronized void setActive(boolean nextState) {
		state = nextState;
	}
	
	public synchronized void setFactor(float nextFactor) {
		factor = nextFactor;
	}
	
	public synchronized void setGain(float gain) {
		marker = gain * idealMarker;
	}
	 
	public synchronized boolean render(final float[] buffer) {
		if(!state && attenuation < 0.0001f) return false;
		if(!renderKids(buffer)) return false;
		
		for(int i = 0; i < CHUNK_SIZE; i++) {
			buffer[i] *= attenuation;
			if(!state) {
				attenuation += (0-attenuation)*factor;
			} else {
				attenuation += (marker-attenuation)*factor;
			}
		}
		return true;
	}
}

UGen.java

package as.adamsmith.etherealdialpad.dsp;

import java.util.ArrayList;

public abstract class UGen {
	public static final int CHUNK_SIZE = 256;
	public static final int SAMPLE_RATE = 22050;
	
	
	ArrayList<UGen> kids = new ArrayList<UGen>(0);
	
	// fill CHUNK_SIZE samples
	// and return true if you actually did any work
	abstract public boolean render(final float[] buffer);

	final public synchronized UGen chuck(UGen that) {
		if(!that.kids.contains(this)) that.kids.add(this);
		return that; // returns RHS
	}
	
	final public synchronized UGen unchuck(UGen that) {		
		if(that.kids.contains(this)) that.kids.remove(this);
		return that; // returns RHS
	}
	
	protected void zeroBuffer(final float[] buffer) {
		for(int i = 0; i < CHUNK_SIZE; i++) {
			buffer[i] = 0;
		}
	}
	
	protected boolean renderKids(final float[] buffer) {
		boolean didSomeRealWork = false;
		for(int k = 0; k < kids.size(); k++) {
			didSomeRealWork |= kids.get(k).render(buffer);
		}
		return didSomeRealWork;
	}
}

usage.java

init {
	WtOsc ugOscA1 = new WtOsc();
	WtOsc ugOscA2 = new WtOsc();
	ExpEnv ugEnvA = new ExpEnv();
	
	ugOscA1.fillWithHardSin(7.0f);
	ugOscA2.fillWithHardSin(2.0f);
	
	Dac ugDac = new Dac();

	Delay ugDelay = new Delay(UGen.SAMPLE_RATE/2);
	
	ugEnvA.chuck(ugDelay);
	ugDelay.chuck(ugDac);
	
	ugOscA1.chuck(ugEnvA);
	ugOscA2.chuck(ugEnvA);
	
	ugEnvA.setFactor(ExpEnv.hardFactor);
}				

touch {
	ugOscA1.setFreq(buildFrequency(scale, octaves, x));
	ugOscA2.setFreq(buildFrequency(scale, octaves, y));
}

run {
	ugDac.open();
	while(!isInterrupted()) {
		ugDac.tick();
	}
	ugDac.close();
}

WtOsc.java

package as.adamsmith.etherealdialpad.dsp;

import android.util.FloatMath;

public class WtOsc extends UGen {
	public static final int BITS = 8;
	public static final int ENTRIES = 1<<(BITS-1);
	public static final int MASK = ENTRIES-1;
	
	private float phase;
	private float cyclesPerSample;
	
	final float[] table;
	
	public WtOsc () {
		table = new float[ENTRIES];
	}
	
	public synchronized void setFreq(float freq) {
		cyclesPerSample = freq/SAMPLE_RATE;
	} 
	
	public synchronized boolean render(final float[] buffer) { // assume t is in 0.0 to 1.0
		for(int i = 0; i < CHUNK_SIZE; i++) {
			float scaled = phase*ENTRIES;
			final float fraction = scaled-(int)scaled;
			final int index = (int)scaled;
			buffer[i] += (1.0f-fraction)*table[index&MASK]+fraction*table[(index+1)&MASK];
			phase = (phase+cyclesPerSample) - (int)phase; 
		}
		
		return true;
	}
	
	public WtOsc fillWithSin() {
		final float dt = (float)(2.0*Math.PI/ENTRIES);
		for(int i = 0; i < ENTRIES; i++) {
			table[i] = FloatMath.sin(i*dt);
		}
		return this;
	}
	
	public WtOsc fillWithHardSin(final float exp) {
		final float dt = (float)(2.0*Math.PI/ENTRIES);
		for(int i = 0; i < ENTRIES; i++) {
			table[i] = (float) Math.pow(FloatMath.sin(i*dt),exp);
		}
		return this;
	}
	
	public WtOsc fillWithZero() {
		for(int i = 0; i < ENTRIES; i++) {
			table[i] = 0;
		}
		return this;
	}
	
	public WtOsc fillWithSqr() {
		for(int i = 0; i < ENTRIES; i++) {
			table[i] = i<ENTRIES/2?1f:-1f;
		}
		return this;
	}
	
	public WtOsc fillWithSqrDuty(float fraction) {
		for(int i = 0; i < ENTRIES; i++) {
			table[i] = (float)i/ENTRIES<fraction?1f:-1f;
		}
		return this;
	}
	
	public WtOsc fillWithSaw() {
		float dt = (float)(2.0/ENTRIES);
		for(int i = 0; i < ENTRIES; i++) {
			table[i] = 1.0f-i*dt;
		}
		return this;
	}
}