Added low pass filters in the delay path

src/AudioEffectAnalogDelay.cpp

@@ -13,17 +13,28 @@ constexpr int MIDI_NUM_PARAMS = 4;
 constexpr int MIDI_CHANNEL = 0;
 constexpr int MIDI_CONTROL = 1;
 
-constexpr int MIDI_ENABLE = 0;
+constexpr int MIDI_BYPASS = 0;
 constexpr int MIDI_DELAY = 1;
 constexpr int MIDI_FEEDBACK = 2;
 constexpr int MIDI_MIX = 3;
 
+// BOSS DM-3 Filters
+constexpr unsigned NUM_IIR_STAGES = 4;
+constexpr unsigned IIR_COEFF_SHIFT = 2;
+constexpr int32_t DEFAULT_COEFFS[5*NUM_IIR_STAGES] = {
+		536870912,            988616936,            455608573,            834606945,           -482959709,
+		536870912,           1031466345,            498793368,            965834205,           -467402235,
+		536870912,           1105821939,            573646688,            928470657,           -448083489,
+    2339,                 5093,                 2776,            302068995,              4412722
+};
+
 
 AudioEffectAnalogDelay::AudioEffectAnalogDelay(float maxDelay)
 : AudioStream(1, m_inputQueueArray)
 {
 	m_memory = new AudioDelay(maxDelay);
 	m_maxDelaySamples = calcAudioSamples(maxDelay);
+	m_iir  = new IirBiQuadFilterHQ(NUM_IIR_STAGES, reinterpret_cast<const int32_t *>(&DEFAULT_COEFFS), IIR_COEFF_SHIFT);
 }
 
 AudioEffectAnalogDelay::AudioEffectAnalogDelay(size_t numSamples)
@@ -31,6 +42,7 @@ AudioEffectAnalogDelay::AudioEffectAnalogDelay(size_t numSamples)
 {
 	m_memory = new AudioDelay(numSamples);
 	m_maxDelaySamples = numSamples;
+	m_iir = new IirBiQuadFilterHQ(NUM_IIR_STAGES, reinterpret_cast<const int32_t *>(&DEFAULT_COEFFS), IIR_COEFF_SHIFT);
 }
 
 // requires preallocated memory large enough
@@ -40,68 +52,64 @@ AudioEffectAnalogDelay::AudioEffectAnalogDelay(ExtMemSlot *slot)
 	m_memory = new AudioDelay(slot);
 	m_maxDelaySamples = slot->size();
 	m_externalMemory = true;
+	m_iir = new IirBiQuadFilterHQ(NUM_IIR_STAGES, reinterpret_cast<const int32_t *>(&DEFAULT_COEFFS), IIR_COEFF_SHIFT);
 }
 
 AudioEffectAnalogDelay::~AudioEffectAnalogDelay()
 {
 	if (m_memory) delete m_memory;
+	if (m_iir) delete m_iir;
 }
 
 void AudioEffectAnalogDelay::update(void)
 {
 	audio_block_t *inputAudioBlock = receiveReadOnly(); // get the next block of input samples
 
-	if (!inputAudioBlock) {
+	// Check is block is disabled
-		// create silence
-		inputAudioBlock = allocate();
-		if (!inputAudioBlock) { return; } // failed to allocate
-		else {
-			clearAudioBlock(inputAudioBlock);
-		}
-	}
-
 	if (m_enable == false) {
-		// release all held memory resources
+		// do not transmit or process any audio, return as quickly as possible.
-		transmit(inputAudioBlock);
+		if (inputAudioBlock) release(inputAudioBlock);
-		release(inputAudioBlock); inputAudioBlock = nullptr;
 
+		// release all held memory resources
 		if (m_previousBlock) {
 			release(m_previousBlock); m_previousBlock = nullptr;
 		}
 		if (!m_externalMemory) {
+			// when using internal memory we have to release all references in the ring buffer
 			while (m_memory->getRingBuffer()->size() > 0) {
 				audio_block_t *releaseBlock = m_memory->getRingBuffer()->front();
 				m_memory->getRingBuffer()->pop_front();
 				if (releaseBlock) release(releaseBlock);
 			}
 		}
+		return;
 	}
 
-	if (m_callCount < 1024) {
+	// Check is block is bypassed, if so either transmit input directly or create silence
-		if (inputAudioBlock) {
+	if (m_bypass == true) {
+		// transmit the input directly
+		if (!inputAudioBlock) {
+			// create silence
+			inputAudioBlock = allocate();
+			if (!inputAudioBlock) { return; } // failed to allocate
+			else {
+				clearAudioBlock(inputAudioBlock);
+			}
+		}
 		transmit(inputAudioBlock, 0);
 		release(inputAudioBlock);
-		}
+		return;
-		m_callCount++; return;
 	}
 
-
+	// Otherwise perform normal processing
-	m_callCount++;
-	//Serial.println(String("AudioEffectAnalgDelay::update: ") + m_callCount);
-
 	// Preprocessing
 	audio_block_t *preProcessed = allocate();
+	// mix the input with the feedback path in the pre-processing stage
 	m_preProcessing(preProcessed, inputAudioBlock, m_previousBlock);
 
 	audio_block_t *blockToRelease = m_memory->addBlock(preProcessed);
 	if (blockToRelease) release(blockToRelease);
 
-//	if (inputAudioBlock) {
-//		transmit(inputAudioBlock, 0);
-//		release(inputAudioBlock);
-//	}
-//	return;
-
 	// OUTPUT PROCESSING
 	audio_block_t *blockToOutput = nullptr;
 	blockToOutput = allocate();
@@ -110,7 +118,7 @@ void AudioEffectAnalogDelay::update(void)
 	if (!blockToOutput) return; // skip this time due to failure
 	// copy over data
 	m_memory->getSamples(blockToOutput, m_delaySamples);
-	// perform the mix
+	// perform the wet/dry mix mix
 	m_postProcessing(blockToOutput, inputAudioBlock, blockToOutput);
 	transmit(blockToOutput);
 
@@ -177,11 +185,11 @@ void AudioEffectAnalogDelay::processMidi(int channel, int control, int value)
 		return;
 	}
 
-	if ((m_midiConfig[MIDI_ENABLE][MIDI_CHANNEL] == channel) &&
+	if ((m_midiConfig[MIDI_BYPASS][MIDI_CHANNEL] == channel) &&
-        (m_midiConfig[MIDI_ENABLE][MIDI_CONTROL] == control)) {
+        (m_midiConfig[MIDI_BYPASS][MIDI_CONTROL] == control)) {
-		// Enable
+		// Bypass
-		if (value >= 65) { enable(); Serial.println(String("AudioEffectAnalogDelay::enable: ON") + value); }
+		if (value >= 65) { bypass(false); Serial.println(String("AudioEffectAnalogDelay::not bypassed -> ON") + value); }
-		else { disable(); Serial.println(String("AudioEffectAnalogDelay::enable: OFF") + value); }
+		else { bypass(true); Serial.println(String("AudioEffectAnalogDelay::bypassed -> OFF") + value); }
 		return;
 	}
 
@@ -208,10 +216,10 @@ void AudioEffectAnalogDelay::mapMidiDelay(int control, int channel)
 	m_midiConfig[MIDI_DELAY][MIDI_CONTROL] = control;
 }
 
-void AudioEffectAnalogDelay::mapMidiEnable(int control, int channel)
+void AudioEffectAnalogDelay::mapMidiBypass(int control, int channel)
 {
-	m_midiConfig[MIDI_ENABLE][MIDI_CHANNEL] = channel;
+	m_midiConfig[MIDI_BYPASS][MIDI_CHANNEL] = channel;
-	m_midiConfig[MIDI_ENABLE][MIDI_CONTROL] = control;
+	m_midiConfig[MIDI_BYPASS][MIDI_CONTROL] = control;
 }
 
 void AudioEffectAnalogDelay::mapMidiFeedback(int control, int channel)
@@ -239,6 +247,8 @@ void AudioEffectAnalogDelay::m_preProcessing(audio_block_t *out, audio_block_t *
 void AudioEffectAnalogDelay::m_postProcessing(audio_block_t *out, audio_block_t *dry, audio_block_t *wet)
 {
 	if ( out && dry && wet) {
+		// Simulate the LPF IIR nature of the analog systems
+		m_iir->process(wet->data, wet->data, AUDIO_BLOCK_SAMPLES);
 		alphaBlend(out, dry, wet, m_mix);
 	} else if (dry) {
 		memcpy(out->data, dry->data, sizeof(int16_t) * AUDIO_BLOCK_SAMPLES);

src/AudioEffectAnalogDelay.h

@@ -8,8 +8,6 @@
 #ifndef SRC_AUDIOEFFECTANALOGDELAY_H_
 #define SRC_AUDIOEFFECTANALOGDELAY_H_
 
-//#include <vector>
-
 #include <Audio.h>
 #include "LibBasicFunctions.h"
 
@@ -17,8 +15,6 @@ namespace BAGuitar {
 
 class AudioEffectAnalogDelay : public AudioStream {
 public:
-	static constexpr int MAX_DELAY_CHANNELS = 8;
-
 	AudioEffectAnalogDelay() = delete;
 	AudioEffectAnalogDelay(float maxDelay);
 	AudioEffectAnalogDelay(size_t numSamples);
@@ -28,35 +24,35 @@ public:
 	virtual void update(void);
 	void delay(float milliseconds);
 	void delay(size_t delaySamples);
+
+	void bypass(bool byp) { m_bypass = byp; }
 	void feedback(float feedback) { m_feedback = feedback; }
 	void mix(float mix) { m_mix = mix; }
 	void enable() { m_enable = true; }
 	void disable() { m_enable = false; }
 
 	void processMidi(int channel, int control, int value);
-	void mapMidiEnable(int control, int channel = 0);
+	void mapMidiBypass(int control, int channel = 0);
 	void mapMidiDelay(int control, int channel = 0);
 	void mapMidiFeedback(int control, int channel = 0);
 	void mapMidiMix(int control, int channel = 0);
 
 private:
 	audio_block_t *m_inputQueueArray[1];
+	bool m_bypass = true;
 	bool m_enable = false;
 	bool m_externalMemory = false;
 	AudioDelay *m_memory = nullptr;
 	size_t m_maxDelaySamples = 0;
+	audio_block_t *m_previousBlock = nullptr;
+	IirBiQuadFilterHQ *m_iir = nullptr;
 
 	// Controls
 	int m_midiConfig[4][2];
-	//int m_midiEnable[2] = {0,16};
 	size_t m_delaySamples = 0;
-	//int m_midiDelay[2] = {0,20};
 	float m_feedback = 0.0f;
-	//int m_midiFeedback[2] = {0,21};
 	float m_mix = 0.0f;
-	//int m_midiMix[2] = {0,22};
 
-	audio_block_t *m_previousBlock = nullptr;
 	void m_preProcessing(audio_block_t *out, audio_block_t *dry, audio_block_t *wet);
 	void m_postProcessing(audio_block_t *out, audio_block_t *dry, audio_block_t *wet);
 

src/LibBasicFunctions.cpp

@@ -34,9 +34,21 @@ size_t calcOffset(QueuePosition position)
 
 void alphaBlend(audio_block_t *out, audio_block_t *dry, audio_block_t* wet, float mix)
 {
-	for (int i=0; i< AUDIO_BLOCK_SAMPLES; i++) {
+	 //Non-optimized version for illustrative purposes
-		out->data[i] = (dry->data[i] * (1 - mix)) + (wet->data[i] * mix);
+//		for (int i=0; i< AUDIO_BLOCK_SAMPLES; i++) {
-	}
+//			out->data[i] = (dry->data[i] * (1 - mix)) + (wet->data[i] * mix);
+//		}
+//		return;
+
+	// ARM DSP optimized
+	int16_t wetBuffer[AUDIO_BLOCK_SAMPLES];
+	int16_t dryBuffer[AUDIO_BLOCK_SAMPLES];
+	int16_t scaleFractWet = (int16_t)(mix * 32767.0f);
+	int16_t scaleFractDry = 32767-scaleFractWet;
+
+	arm_scale_q15(dry->data, scaleFractDry, 0, dryBuffer, AUDIO_BLOCK_SAMPLES);
+	arm_scale_q15(wet->data, scaleFractWet, 0, wetBuffer, AUDIO_BLOCK_SAMPLES);
+	arm_add_q15(wetBuffer, dryBuffer, out->data, AUDIO_BLOCK_SAMPLES);
 }
 
 void clearAudioBlock(audio_block_t *block)
@@ -45,6 +57,9 @@ void clearAudioBlock(audio_block_t *block)
 }
 
 
+////////////////////////////////////////////////////
+// AudioDelay
+////////////////////////////////////////////////////
 AudioDelay::AudioDelay(size_t maxSamples)
 : m_slot(nullptr)
 {
@@ -210,5 +225,123 @@ bool AudioDelay::getSamples(audio_block_t *dest, size_t offset, size_t numSample
 
 }
 
+////////////////////////////////////////////////////
+// IirBiQuadFilter
+////////////////////////////////////////////////////
+IirBiQuadFilter::IirBiQuadFilter(unsigned numStages, const int32_t *coeffs, int coeffShift)
+: NUM_STAGES(numStages)
+{
+	m_coeffs = new int32_t[5*numStages];
+	memcpy(m_coeffs, coeffs, 5*numStages * sizeof(int32_t));
+
+	m_state  = new int32_t[4*numStages];
+	arm_biquad_cascade_df1_init_q31(&m_iirCfg, numStages, m_coeffs, m_state, coeffShift);
+}
+
+IirBiQuadFilter::~IirBiQuadFilter()
+{
+	if (m_coeffs) delete [] m_coeffs;
+	if (m_state)  delete [] m_state;
+}
+
+
+bool IirBiQuadFilter::process(int16_t *output, int16_t *input, size_t numSamples)
+{
+	if (!output) return false;
+	if (!input) {
+		// send zeros
+		memset(output, 0, numSamples * sizeof(int16_t));
+	} else {
+
+		// create convertion buffers on teh stack
+		int32_t input32[numSamples];
+		int32_t output32[numSamples];
+		for (int i=0; i<numSamples; i++) {
+			input32[i] = (int32_t)(input[i]);
+		}
+
+		arm_biquad_cascade_df1_fast_q31(&m_iirCfg, input32, output32, numSamples);
+
+		for (int i=0; i<numSamples; i++) {
+			output[i] = (int16_t)(output32[i] & 0xffff);
+		}
+	}
+	return true;
+}
+
+// HIGH QUALITY
+IirBiQuadFilterHQ::IirBiQuadFilterHQ(unsigned numStages, const int32_t *coeffs, int coeffShift)
+: NUM_STAGES(numStages)
+{
+	m_coeffs = new int32_t[5*numStages];
+	memcpy(m_coeffs, coeffs, 5*numStages * sizeof(int32_t));
+
+	m_state = new int64_t[4*numStages];;
+	arm_biquad_cas_df1_32x64_init_q31(&m_iirCfg, numStages, m_coeffs, m_state, coeffShift);
+}
+
+IirBiQuadFilterHQ::~IirBiQuadFilterHQ()
+{
+	if (m_coeffs) delete [] m_coeffs;
+	if (m_state)  delete [] m_state;
+}
+
+
+bool IirBiQuadFilterHQ::process(int16_t *output, int16_t *input, size_t numSamples)
+{
+	if (!output) return false;
+	if (!input) {
+		// send zeros
+		memset(output, 0, numSamples * sizeof(int16_t));
+	} else {
+
+		// create convertion buffers on teh stack
+		int32_t input32[numSamples];
+		int32_t output32[numSamples];
+		for (int i=0; i<numSamples; i++) {
+			input32[i] = (int32_t)(input[i]);
+		}
+
+		arm_biquad_cas_df1_32x64_q31(&m_iirCfg, input32, output32, numSamples);
+
+		for (int i=0; i<numSamples; i++) {
+			output[i] = (int16_t)(output32[i] & 0xffff);
+		}
+	}
+	return true;
+}
+
+// FLOAT
+IirBiQuadFilterFloat::IirBiQuadFilterFloat(unsigned numStages, const float *coeffs)
+: NUM_STAGES(numStages)
+{
+	m_coeffs = new float[5*numStages];
+	memcpy(m_coeffs, coeffs, 5*numStages * sizeof(float));
+
+	m_state = new float[4*numStages];;
+	arm_biquad_cascade_df2T_init_f32(&m_iirCfg, numStages, m_coeffs, m_state);
+}
+
+IirBiQuadFilterFloat::~IirBiQuadFilterFloat()
+{
+	if (m_coeffs) delete [] m_coeffs;
+	if (m_state)  delete [] m_state;
+}
+
+
+bool IirBiQuadFilterFloat::process(float *output, float *input, size_t numSamples)
+{
+	if (!output) return false;
+	if (!input) {
+		// send zeros
+		memset(output, 0, numSamples * sizeof(float));
+	} else {
+
+		arm_biquad_cascade_df2T_f32(&m_iirCfg, input, output, numSamples);
+
+	}
+	return true;
+}
+
 }
 

src/LibBasicFunctions.h

@@ -23,6 +23,7 @@
 #include <cstddef>
 #include <new>
 
+#include <arm_math.h>
 #include "Arduino.h"
 #include "Audio.h"
 
@@ -153,6 +154,65 @@ private:
     ExtMemSlot *m_slot = nullptr;                        ///< When using EXTERNAL memory, an ExtMemSlot must be provided.
 };
 
+/**************************************************************************//**
+ * IIR BiQuad Filter - Direct Form I <br>
+ * y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]<br>
+ * Some design tools (like Matlab assume the feedback coefficients 'a' are negated. You
+ * may have to negate your 'a' coefficients.
+ * @details Note that the ARM CMSIS-DSP library requires an extra zero between first
+ * and second 'b' coefficients. E.g. <br>
+ * {b10, 0, b11, b12, a11, a12, b20, 0, b21, b22, a21, a22, ...}
+ *****************************************************************************/
+class IirBiQuadFilter {
+public:
+	IirBiQuadFilter() = delete;
+	IirBiQuadFilter(unsigned numStages, const int32_t *coeffs, int coeffShift = 0);
+	virtual ~IirBiQuadFilter();
+	bool process(int16_t *output, int16_t *input, size_t numSamples);
+private:
+	const unsigned NUM_STAGES;
+	int32_t *m_coeffs = nullptr;
+
+	// ARM DSP Math library filter instance
+	arm_biquad_casd_df1_inst_q31 m_iirCfg;
+	int32_t *m_state = nullptr;
+};
+
+
+class IirBiQuadFilterHQ {
+public:
+	IirBiQuadFilterHQ() = delete;
+	IirBiQuadFilterHQ(unsigned numStages, const int32_t *coeffs, int coeffShift = 0);
+	virtual ~IirBiQuadFilterHQ();
+	bool process(int16_t *output, int16_t *input, size_t numSamples);
+private:
+
+
+	const unsigned NUM_STAGES;
+	int32_t *m_coeffs = nullptr;
+
+	// ARM DSP Math library filter instance
+	arm_biquad_cas_df1_32x64_ins_q31 m_iirCfg;
+	int64_t *m_state = nullptr;
+
+};
+
+class IirBiQuadFilterFloat {
+public:
+	IirBiQuadFilterFloat() = delete;
+	IirBiQuadFilterFloat(unsigned numStages, const float *coeffs);
+	virtual ~IirBiQuadFilterFloat();
+	bool process(float *output, float *input, size_t numSamples);
+private:
+	const unsigned NUM_STAGES;
+	float *m_coeffs = nullptr;
+
+	// ARM DSP Math library filter instance
+	arm_biquad_cascade_df2T_instance_f32 m_iirCfg;
+	float *m_state = nullptr;
+
+};
+
 /**************************************************************************//**
  * Customer RingBuffer with random access
  *****************************************************************************/