Add WaveFolder unit generator.

Fold waveforms using sin(a*x).

2 files changed, 87 insertions, 5 deletions

diff --git a/src/main/java/com/jsyn/unitgen/SchmidtTrigger.java b/src/main/java/com/jsyn/unitgen/SchmidtTrigger.java
index 64129ff..c421d5d 100644
--- a/src/main/java/com/jsyn/unitgen/SchmidtTrigger.java
+++ b/src/main/java/com/jsyn/unitgen/SchmidtTrigger.java
@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *     http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -27,7 +27,7 @@ import com.jsyn.ports.UnitOutputPort;
  * signal. The default values for setLevel and resetLevel are both 0.0. Setting setLevel to 0.1 and
  * resetLevel to -0.1 will give some hysteresis. The outputPulse is a single sample wide pulse set
  * when the output transitions from low to high.
- * 
+ *
  * <PRE>
  * if (output == 0.0)
  *     output = (input &gt; setLevel) ? 1.0 : 0.0;
@@ -36,7 +36,7 @@ import com.jsyn.ports.UnitOutputPort;
  * else
  *     output = previous_output;
  * </PRE>
- * 
+ *
  * @author Phil Burk (C) 2009 Mobileer Inc
  * @see Compare
  */
@@ -49,7 +49,6 @@ public class SchmidtTrigger extends UnitFilter {
     public SchmidtTrigger() {
         addPort(setLevel = new UnitInputPort("SetLevel"));
         addPort(resetLevel = new UnitInputPort("ResetLevel"));
-        addPort(input = new UnitInputPort("Input"));
         addPort(outputPulse = new UnitOutputPort("OutputPulse"));
     }
 
diff --git a/src/main/java/com/jsyn/unitgen/WaveFolder.java b/src/main/java/com/jsyn/unitgen/WaveFolder.java
new file mode 100644
index 0000000..ed9ead7
--- /dev/null
+++ b/src/main/java/com/jsyn/unitgen/WaveFolder.java
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2009 Phil Burk, Mobileer Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.jsyn.unitgen;
+
+import com.jsyn.ports.UnitInputPort;
+
+/**
+ * Wave Folder
+ *
+ * Fold the input waveform by passing it through a sine function
+ * and output the results in the range of -1.0 to 1.0.
+ *
+ * This works best if the amplitude of the input waveform is close to 1.0.
+ *
+ * @author Phil Burk (C) 2020 Mobileer Inc
+ */
+public class WaveFolder extends UnitFilter
+{
+	/**
+	 * The depth of the wave-folding effect.
+	 * At zero there should be no audible effect.
+	 */
+    public UnitInputPort amount;
+    private static final double MAX_SCALE = 8.0;
+
+    /* Define Unit Ports used by connect() and set(). */
+    public WaveFolder() {
+        addPort(amount = new UnitInputPort("Amount"));
+        amount.setup(0.0, 0.0, MAX_SCALE);
+    }
+
+	@Override
+	public void generate( int start, int limit )
+	{
+        double[] inputs = input.getValues();
+        double[] scales = amount.getValues();
+        double[] outputs = output.getValues();
+
+        for (int i = start; i < limit; i++) {
+        	double inputValue = inputs[i];
+        	double scaleValue = scales[i];
+
+        	// Prevent blowup near zero.
+        	scaleValue = Math.max(scaleValue, 0.00001);
+        	double phase = inputValue * scaleValue;
+
+        	double folded;
+//        	if (true) {
+	        	// Clip to -1/+1 range for fastSin even for extreme ranges.
+	    		phase = (phase + 256.0 + 1.0) * 0.5;
+	    		phase -= Math.floor(phase);
+	    		phase = (phase * 2.0) - 1.0;
+
+	        	// Fold using a sine function that ranges -1 to +1.
+	        	folded = SineOscillator.fastSin(phase);
+//        	} else {
+//        		folded = Math.sin(phase * Math.PI); // slow
+//        	}
+
+        	// Try to maintain constant amplitude at small scale value.
+        	// Based on sin(x) ~= x for low values of x.
+        	if (scaleValue < 1.0) {
+	        	folded /= scaleValue * (((1 - Math.PI) * scaleValue) + Math.PI);
+        	}
+            outputs[i] = folded;
+        }
+	}
+
+}