Add AudioFilterStateVariable (work in progress....)

Audio.h

 #include "effect_delay.h"
 #include "filter_biquad.h"
 #include "filter_fir.h"
+#include "filter_variable.h"
 #include "input_adc.h"
 #include "input_i2s.h"
 #include "mixer.h"

filter_variable.cpp

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2014, Paul Stoffregen, paul@pjrc.com
+ *
+ * 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 "filter_variable.h"
+#include "utility/dspinst.h"
+
+
+// State Variable Filter (Chamberlin) with 2X oversampling
+// http://www.musicdsp.org/showArchiveComment.php?ArchiveID=92
+
+//#define MULT(a, b) (int32_t)(((int64_t)(a) * (b)) >> 30)
+#define MULT(a, b) (multiply_32x32_rshift32_rounded(a, b) << 2)
+
+static bool first = true;
+
+void AudioFilterStateVariable::update_fixed(const int16_t *in,
+	int16_t *lp, int16_t *bp, int16_t *hp)
+{
+	const int16_t *end = in + AUDIO_BLOCK_SAMPLES;
+	int32_t input, inputprev;
+	int32_t lowpass, bandpass, highpass;
+	int32_t lowpasstmp, bandpasstmp, highpasstmp;
+	int32_t fmult, damp;
+
+	fmult = setting_fmult;
+	damp = setting_damp;
+	inputprev = state_inputprev;
+	lowpass = state_lowpass;
+	bandpass = state_bandpass;
+
+	do {
+		input = (*in++) << 12;
+		lowpass = lowpass + MULT(fmult, bandpass);
+		highpass = ((input + inputprev)>>1) - lowpass - MULT(damp, bandpass);
+		inputprev = input;
+		bandpass = bandpass + MULT(fmult, highpass);
+		lowpasstmp = lowpass;
+		bandpasstmp = bandpass;
+		highpasstmp = highpass;
+		lowpass = lowpass + MULT(fmult, bandpass);
+		highpass = input - lowpass - MULT(damp, bandpass);
+		bandpass = bandpass + MULT(fmult, highpass);
+		lowpasstmp = signed_saturate_rshift(lowpass+lowpasstmp, 16, 13);
+		bandpasstmp = signed_saturate_rshift(bandpass+bandpasstmp, 16, 13);
+		highpasstmp = signed_saturate_rshift(highpass+highpasstmp, 16, 13);
+		*lp++ = lowpasstmp;
+		*bp++ = bandpasstmp;
+		*hp++ = highpasstmp;
+#if 0
+		if (first) {
+			Serial.print(input >> 12);
+			Serial.print(", ");
+			Serial.print(lowpasstmp);
+			Serial.print(", ");
+			Serial.print(bandpasstmp);
+			Serial.print(", ");
+			Serial.print(highpasstmp);
+			Serial.println();
+		}
+#endif
+	} while (in < end);
+
+	state_inputprev = inputprev;
+	state_lowpass = lowpass;
+	state_bandpass = bandpass;
+	first = false;
+}
+
+void AudioFilterStateVariable::update_variable(const int16_t *in,
+	const int16_t *ctl, int16_t *lp, int16_t *bp, int16_t *hp)
+{
+	// TODO: implement control signal modulation of corner frequency
+	update_fixed(in, lp, bp, hp);
+}
+
+void AudioFilterStateVariable::update(void)
+{
+	audio_block_t *input_block=NULL, *control_block=NULL;
+	audio_block_t *lowpass_block=NULL, *bandpass_block=NULL, *highpass_block=NULL;
+
+	input_block = receiveReadOnly(0);
+	control_block = receiveReadOnly(1);
+	if (!input_block) {
+		if (control_block) release(control_block);
+		return;
+	}
+	lowpass_block = allocate();
+	if (!lowpass_block) {
+		release(input_block);
+		if (control_block) release(control_block);
+		return;
+	}
+	bandpass_block = allocate();
+	if (!bandpass_block) {
+		release(input_block);
+		release(lowpass_block);
+		if (control_block) release(control_block);
+		return;
+	}
+	highpass_block = allocate();
+	if (!highpass_block) {
+		release(input_block);
+		release(lowpass_block);
+		release(bandpass_block);
+		if (control_block) release(control_block);
+		return;
+	}
+
+	if (control_block) {
+		update_variable(input_block->data,
+			 control_block->data,
+			 lowpass_block->data,
+			 bandpass_block->data,
+			 highpass_block->data);
+		release(control_block);
+	} else {
+		update_fixed(input_block->data,
+			 lowpass_block->data,
+			 bandpass_block->data,
+			 highpass_block->data);
+	}
+	release(input_block);
+	transmit(lowpass_block, 0);
+	release(lowpass_block);
+	transmit(bandpass_block, 1);
+	release(bandpass_block);
+	transmit(highpass_block, 2);
+	release(highpass_block);
+	return;
+}
+

filter_variable.h

+/* Audio Library for Teensy 3.X
+ * Copyright (c) 2014, Paul Stoffregen, paul@pjrc.com
+ *
+ * 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.
+ */
+
+#ifndef filter_variable_h_
+#define filter_variable_h_
+
+#include "AudioStream.h"
+
+class AudioFilterStateVariable: public AudioStream
+{
+public:
+	AudioFilterStateVariable() : AudioStream(2, inputQueueArray) {
+		frequency(1000);
+		resonance(0.707);
+		state_inputprev = 0;
+		state_lowpass = 0;
+		state_bandpass = 0;
+	}
+	void frequency(float freq) {
+		if (freq < 20.0) freq = 20.0;
+		else if (freq > AUDIO_SAMPLE_RATE_EXACT/2.5) freq = AUDIO_SAMPLE_RATE_EXACT/2.5;
+		setting_fmult = sinf(freq * (3.141592654/(AUDIO_SAMPLE_RATE_EXACT*2.0)))
+			* 2147483647.0;
+	}
+	void resonance(float q) {
+		if (q < 0.7) q = 0.7;
+		else if (q > 5.0) q = 5.0;
+		// TODO: allow lower Q when frequency is lower
+		setting_damp = (1.0 / q) * 1073741824.0;
+	}
+	virtual void update(void);
+private:
+	void update_fixed(const int16_t *in,
+		int16_t *lp, int16_t *bp, int16_t *hp);
+	void update_variable(const int16_t *in, const int16_t *ctl,
+		int16_t *lp, int16_t *bp, int16_t *hp);
+	int32_t setting_fmult;
+	int32_t setting_damp;
+	int32_t state_inputprev;
+	int32_t state_lowpass;
+	int32_t state_bandpass;
+	audio_block_t *inputQueueArray[2];
+};
+
+#endif

keywords.txt

 AudioEffectDelay	KEYWORD2
 AudioFilterBiquad	KEYWORD2
 AudioFilterFIR	KEYWORD2
+AudioFilterStateVariable	KEYWORD2
 AudioInputAnalog	KEYWORD2
 AudioMixer4	KEYWORD2
 AudioOutputAnalog	KEYWORD2
 updateCoefs	KEYWORD2
 frequency	KEYWORD2
 amplitude	KEYWORD2
+resonance	KEYWORD2
 modify	KEYWORD2
 output	KEYWORD2
 trigger	KEYWORD2