Improved ruggedness of dynamics against startup problems. Prevented DIVby0. 8-channel mixer is working with gate, EQ and compression.

Author: Dr. Christian Nöding

dsp/dsp1/src/audio.c

@@ -107,6 +107,7 @@ void audioProcessData(void) {
 	// 30 FLOP per channel * 40 channels = 1,200 FLOP in total
 
 	float audioProcessedSample;
+	float mainDebug;
 	float mainLeft;
 	float mainRight;
 	float mainSub;
@@ -118,14 +119,15 @@ void audioProcessData(void) {
 	// now iterate through all channels and all samples
 	// 24 channels are the hard limit at the moment - on some occasions it will not be able to process all data until next buffer
 	// so stay at 8 channels for now
-	//for (int i_tdm = 0; i_tdm < TDM_INPUTS; i_tdm++) {
 	for (int s = 0; s < SAMPLES_IN_BUFFER; s++) {
 		bufferSampleIndex = (BUFFER_SIZE * audioBufferCounter) + (CHANNELS_PER_TDM * s); // (select correct buffer 0 or 1) + (sample-offset)
 
 		mainLeft = 0.0f;
 		mainRight = 0.0f;
 		mainSub = 0.0f;
+		mainDebug = 0.0f;
 
+		//for (int i_tdm = 0; i_tdm < TDM_INPUTS; i_tdm++) {
 		for (int i_tdm = 0; i_tdm < 1; i_tdm++) {
 			bufferTdmIndex = bufferSampleIndex + (BUFFER_COUNT * BUFFER_SIZE * i_tdm);
 
@@ -140,6 +142,7 @@ void audioProcessData(void) {
 				// input -> Noisegate -> EQ1 -> EQ2 -> EQ3 -> EQ4 -> EQ5 -> Compressor -> output
 
 				audioProcessedSample = audioRxBuf[bufferReadIndex];
+				mainDebug += (audioRxBuf[bufferReadIndex]); // direct-through signal on output 1
 
 				// process noisegate
 				audioProcessedSample = fxProcessGate(audioProcessedSample, &dsp.dspChannel[dspCh].gate);
@@ -186,12 +189,14 @@ void audioProcessData(void) {
 		// Ch25-32: UltraNet 9-16
 		// Ch33-40: AUX 1-6 / MonitorL/R
 
-		// copy masterLeft to TDM0, ch0
-		// copy masterRight to TDM0, ch1
-		// copy masterSub to TDM0, ch2
-		audioTxBuf[bufferSampleIndex] = mainLeft;
-		audioTxBuf[bufferSampleIndex + 1] = mainRight;
-		audioTxBuf[bufferSampleIndex + 2] = mainSub;
+		// copy mainDebug to TDM0, ch0 for direct passthrough-test
+		// copy mainLeft to TDM0, ch1
+		// copy mainRight to TDM0, ch2
+		// copy mainSub to TDM0, ch3
+		audioTxBuf[bufferSampleIndex] = mainDebug;
+		audioTxBuf[bufferSampleIndex + 1] = mainLeft;
+		audioTxBuf[bufferSampleIndex + 2] = mainRight;
+		audioTxBuf[bufferSampleIndex + 3] = mainSub;
 	}
 
 	// increment buffer-counter for next call

dsp/dsp1/src/dsp1.c

@@ -76,6 +76,18 @@ void delay(int i) {
     }
 }
 
+void openx32Init(void) {
+	// initialize the default samplerate with 48kHz
+	// other samplerates up to 192kHz are possible with AD and DA converters
+	dsp.samplerate = 48000;
+
+	// initialize states of dynamics
+	for (int ch = 0; ch < MAX_CHAN; ch++) {
+		dsp.dspChannel[ch].gate.state = GATE_CLOSED;
+		dsp.dspChannel[ch].compressor.state = COMPRESSOR_IDLE;
+	}
+}
+
 void openx32Command(unsigned short classId, unsigned short channel, unsigned short index, unsigned short valueCount, void* values) {
 	/*
 	  SPI ClassIds:
@@ -165,7 +177,7 @@ int main() {
 	systemExternalMemoryInit();
 	systemSruInit();
 
-	dsp.samplerate = 48000; // other samplerates up to 192kHz are possible with AD and DA converters
+	openx32Init();
 	spiInit();
 	audioInit();
 	systemSportInit();

dsp/dsp1/src/fx.c

@@ -6,6 +6,7 @@ float fxProcessGate(float input, sGate* gate) {
 	// calculate the gate-logic and online-parameters
 	switch (gate->state) {
 		case GATE_CLOSED:
+			gate->gainSet = gate->value_gainmin;
 			// check if we have to open the gate
 			if (!gate->closed) {
 				gate->state = GATE_ATTACK;
@@ -39,6 +40,9 @@ float fxProcessGate(float input, sGate* gate) {
 			gate->coeff = gate->value_coeff_release;
 			gate->state = GATE_CLOSED;
 			break;
+		default:
+			gate->state = GATE_CLOSED;
+			break;
 	}
 
 	// gainCurrent = (gainCurrent * coeff) + (gainSet - gainSet * coeff);
@@ -61,28 +65,39 @@ float fxProcessEq(float input, sPEQ* peq) {
 }
 
 float fxProcessCompressor(float input, sCompressor* compressor) {
-	compressor->active = (abs(input) > compressor->value_threshold);
+	float input_abs = abs(input);
+
+	compressor->active = (input_abs > compressor->value_threshold);
 
 	// calculate the gate-logic and online-parameters
 	switch (compressor->state) {
 		case COMPRESSOR_IDLE:
+			compressor->gainSet = 1.0f;
 			// check if we have to open the gate
 			if (compressor->active) {
 				compressor->state = COMPRESSOR_ATTACK;
 			}
 			break;
 		case COMPRESSOR_ATTACK:
-			compressor->gainSet = (((abs(input) - compressor->value_threshold) / compressor->value_ratio) + compressor->value_threshold) / input;
+			// overshoot = abs(sample) - threshold
+			// output = (overshoot / ratio) + threshold
+			// gainSet = output / abs(input)
+			if ((input_abs > 0) && (compressor->value_ratio != 0)) {
+				compressor->gainSet = (((input_abs - compressor->value_threshold) / compressor->value_ratio) + compressor->value_threshold) / input_abs;
+			}
 			compressor->coeff = compressor->value_coeff_attack;
 			compressor->state = COMPRESSOR_ACTIVE;
 			break;
 		case COMPRESSOR_ACTIVE:
 			if (compressor->active) {
 				// check if we have to compress even more
-				float newValue = (((abs(input) - compressor->value_threshold) / compressor->value_ratio) + compressor->value_threshold) / input;
-				if (newValue < compressor->gainSet) {
-					// compress even more
-					compressor->gainSet = newValue;
+				float newValue;
+				if ((input_abs > 0) && (compressor->value_ratio != 0)) {
+					newValue = (((input_abs - compressor->value_threshold) / compressor->value_ratio) + compressor->value_threshold) / input_abs;
+					if (newValue < compressor->gainSet) {
+						// compress even more
+						compressor->gainSet = newValue;
+					}
 				}
 			}else{
 				compressor->holdCounter = compressor->value_hold_ticks;
@@ -107,10 +122,13 @@ float fxProcessCompressor(float input, sCompressor* compressor) {
 			compressor->coeff = compressor->value_coeff_release;
 			compressor->state = COMPRESSOR_IDLE;
 			break;
+		default:
+			compressor->state = COMPRESSOR_IDLE;
+			break;
 	}
 
 	// gainCurrent = (gainCurrent * coeff) + gainSet - (gainSet * coeff);
 	compressor->gainCurrent = (compressor->gainCurrent * compressor->coeff) + compressor->gainSet - (compressor->gainSet * compressor->coeff);
 
-	return (input * compressor->gainCurrent) * compressor->value_makeup;
+	return input * compressor->gainCurrent * compressor->value_makeup;
 }