Add waveshaper effect

effect_waveshaper.cpp

@@ -0,0 +1,71 @@
+/*
+ * Waveshaper for Teensy 3.X audio
+ *
+ * Copyright (c) 2017 Damien Clarke, http://damienclarke.me
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "effect_waveshaper.h"
+
+void AudioEffectWaveshaper::shape(int16_t* waveshape, int length)
+{
+  // length must be bigger than 1 and equal to a power of two + 1
+  // anything else means we don't continue
+  if(!waveshape || length < 2 || length > 32769 || ((length - 1) & (length - 2))) return;
+
+  this->waveshape = waveshape;
+
+  // set lerpshift to the number of bits to shift while interpolating
+  // to cover the entire waveshape over a uint16_t input range
+  int index = length - 1;
+  lerpshift = 16;
+  while (index >>= 1) --lerpshift;
+}
+
+void AudioEffectWaveshaper::update(void)
+{
+  if(!waveshape) return;
+
+  audio_block_t *block;
+  block = receiveWritable();
+  if (!block) return;
+
+  // performance testing...
+  // unsigned long mcs = micros();
+
+  uint16_t x, xa;
+  int16_t i, ya, yb;
+  for (i = 0; i < AUDIO_BLOCK_SAMPLES; i++) {
+    // bring int16_t data into uint16_t range
+    x = block->data[i] + 32768;
+    // lerp waveshape (from http://coranac.com/tonc/text/fixed.htm)
+    xa = x >> lerpshift;
+    ya = waveshape[xa];
+    yb = waveshape[xa + 1];
+    block->data[i] = ya + ((yb - ya) * (x - (xa << lerpshift)) >> lerpshift);
+  }
+
+  // log performance test without compensating for rollover...
+  // Serial.print("(micros)");
+  // Serial.println(micros() - mcs);
+
+  transmit(block);
+  release(block);
+}

effect_waveshaper.h

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+/*
+ * Waveshaper for Teensy 3.X audio
+ *
+ * Copyright (c) 2017 Damien Clarke, http://damienclarke.me
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef effect_waveshaper_h_
+#define effect_waveshaper_h_
+
+#include "Arduino.h"
+#include "AudioStream.h"
+
+class AudioEffectWaveshaper : public AudioStream
+{
+  public:
+    AudioEffectWaveshaper(void): AudioStream(1, inputQueueArray) {}
+    virtual void update(void);
+    void shape(int16_t* waveshape, int length);
+  private:
+    audio_block_t *inputQueueArray[1];
+    int16_t* waveshape;
+    int16_t lerpshift;
+};
+
+#endif