Add AudioEffectMidSide (thanks Hedde Bosman)

effect_midside.cpp

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2015, Hedde Bosman
+ *
+ * Development of this audio library was funded by PJRC.COM, LLC by sales of
+ * Teensy and Audio Adaptor boards.  Please support PJRC's efforts to develop
+ * open source software by purchasing Teensy or other PJRC products.
+ *
+ * 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, development funding 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_midside.h"
+
+void AudioEffectMidSide::update(void)
+{
+	audio_block_t *blocka, *blockb;
+
+	uint32_t *pa, *pb, *end;
+	uint32_t a12, a34; //, a56, a78;
+	uint32_t b12, b34; //, b56, b78;
+
+	blocka = receiveWritable(0); // left (encoding) or  mid (decoding)
+	blockb = receiveWritable(1); // right (encoding) or side (decoding)
+	if (!blocka || !blockb) {
+		if (blocka) release(blocka); // maybe an extra if statement here but if one
+		if (blockb) release(blockb); // of the blocks is NULL then it's trouble anyway
+		return;
+	}
+
+	pa = (uint32_t *)(blocka->data);
+	pb = (uint32_t *)(blockb->data);
+	end = pa + AUDIO_BLOCK_SAMPLES/2;
+
+	if (encoding) {
+		while (pa < end) {
+			// mid[i] =  (blocka[i] + blockb[i])/2; // div2 to prevent overflows
+			// side[i] = (blocka[i] - blockb[i])/2; // div2 to prevent overflows
+			// L[i] = (mid[i] + side[i])/2;
+			// R[i] = (mid[i] - side[i])/2;
+			a12 = signed_halving_add_16_and_16(*pa, *pb); // mid12
+			a34 = signed_halving_add_16_and_16(*(pa+1), *(pb+1)); //mid34
+			b12 = signed_halving_subtract_16_and_16(*pa, *pb); // side12
+			b34 = signed_halving_subtract_16_and_16(*(pa+1), *(pb+1)); // side34
+			*pa++ = a12;
+			*pa++ = a34;
+			*pb++ = b12;
+			*pb++ = b34;
+		}
+	} else {
+		while (pa < end) {
+			// L[i] = mid[i] + side[i]);
+			// R[i] = mid[i] - side[i]);
+			// Because the /2 has already been applied in the encoding,
+			// we shouldn't have to add it here.
+			// However... because of the posibility that the user has
+			// modified mid or side such that
+			// it could overflow, we have to:
+			// a) preventively do a (x/2+y/2)*2 again, causing bit reduction
+			// or b) perform saturation or something.
+			// While (b) could produce artifacts if saturated, I'll go for
+			// that option to preserve precision
+			// QADD16 and QSUB16 perform saturating add/sub
+			a12 = signed_add_16_and_16(*pa, *pb); // left12
+			a34 = signed_add_16_and_16(*(pa+1), *(pb+1)); // left34
+			b12 = signed_subtract_16_and_16(*pa, *pb); // right12
+			b34 = signed_subtract_16_and_16(*(pa+1), *(pb+1)); // right34
+			*pa++ = a12;
+			*pa++ = a34;
+			*pb++ = b12;
+			*pb++ = b34;
+		}
+	}
+	transmit(blocka, 0); // mid (encoding) or  left (decoding)
+	transmit(blockb, 1); // side (encoding) or right (decoding)
+	release(blocka);
+	release(blockb);
+}

effect_midside.h

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2015, Hedde Bosman
+ *
+ * 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_midside_decode_h_
+#define effect_midside_decode_h_
+
+#include "AudioStream.h"
+
+#include "utility/dspinst.h"
+
+
+/**
+ * This object performs the decoding of mid/side signals into a stereo signal.
+ * That is, left = (mid+side), right = (mid-side)
+ * After encoding and processing, this object decodes the mid/side components 
+ * back into enjoyable stereo audio.
+ * Caution: processed mid/side signals may cause digital saturation (clipping).
+ ***************************************************************/
+class AudioEffectMidSide : public AudioStream
+{
+public:
+	AudioEffectMidSide(void): AudioStream(2,inputQueueArray), encoding(true) { }
+	void encode() { encoding = true; }
+	void decode() { encoding = false; }
+	virtual void update(void);
+private:
+	bool encoding;
+	audio_block_t *inputQueueArray[2];
+};
+
+#endif
+

keywords.txt

 AudioEffectDelay	KEYWORD2
 AudioEffectDelayExternal	KEYWORD2
 AudioEffectBitcrusher	KEYWORD2
+AudioEffectMidSide	KEYWORD2
 AudioFilterBiquad	KEYWORD2
 AudioFilterFIR	KEYWORD2
 AudioFilterStateVariable	KEYWORD2
 phase	KEYWORD2
 amplitude	KEYWORD2
 offset	KEYWORD2
+readPeakToPeak	KEYWORD2
 pulseWidth	KEYWORD2
 resonance	KEYWORD2
 octaveControl	KEYWORD2
 bits	KEYWORD2
 mute_PCM	KEYWORD2
 probability	KEYWORD2
+encode	KEYWORD2
+decode	KEYWORD2
 
 AudioMemoryUsage	KEYWORD2
 AudioMemoryUsageMax	KEYWORD2