minor bug fix at the computation of the target frequency

providing the actual anti-aliasing attenuation and resampling filter length

Resampler.cpp

@@ -129,6 +129,12 @@ void Resampler::setFilter(int32_t halfFiltLength,int32_t overSampling, float cut
 double Resampler::getStep() const {
     return  _stepAdapted;
 }
+double Resampler::getAttenuation() const {
+    return  _attenuation;
+}
+int32_t Resampler::getHalfFilterLength() const{
+	return  _halfFilterLength;
+}
 void Resampler::reset(){
     _initialized=false;
 }
@@ -136,6 +142,7 @@ void Resampler::configure(float fs, float newFs, float attenuation, int32_t minH
     // Serial.print("configure, fs: ");
     // Serial.println(fs);
     if (fs<=0. || newFs <=0.){
+		_attenuation=0;
         _initialized=false;
         return;
     }
@@ -152,9 +159,10 @@ void Resampler::configure(float fs, float newFs, float attenuation, int32_t minH
     float cutOffFrequ, kaiserBeta;
     _overSamplingFactor=1024;
     if (fs <= newFs){
+		_attenuation=0;
         cutOffFrequ=1.;
         kaiserBeta=10;
-        _halfFilterLength=minHalfFilterLength;
+        _halfFilterLength=min(minHalfFilterLength,MAX_HALF_FILTER_LENGTH);
     }
     else{
         cutOffFrequ=newFs/fs;
@@ -204,6 +212,7 @@ void Resampler::configure(float fs, float newFs, float attenuation, int32_t minH
             int32_t f = (noSamples-1)/(MAX_FILTER_SAMPLES-1)+1;
             _overSamplingFactor/=f;
         }
+		_attenuation=attenuation;
     }
 
 #ifdef DEBUG_RESAMPLER

Resampler.h

@@ -69,6 +69,8 @@ class Resampler {
         void addToPos(double val);
         void fixStep();
         bool initialized() const;
+		double getAttenuation() const;
+		int32_t getHalfFilterLength() const;
         
         //resampling NOCHANNELS channels. Performance is increased a lot if the number of channels is known at compile time -> the number of channels is a template argument
         template <uint8_t NOCHANNELS>
@@ -206,7 +208,7 @@ class Resampler {
         float* _endOfBuffer[MAX_NO_CHANNELS];
 
         int32_t _overSamplingFactor;
-        int32_t _halfFilterLength;
+        int32_t _halfFilterLength=0;
         int32_t _filterLength;     
         bool _initialized=false;  
         
@@ -218,6 +220,8 @@ class Resampler {
         double _cPos;
         double _sum;
         double _oldDiffs[2]; 
+		
+		double _attenuation=0;
 };
 
 #endif

async_input_spdif3.cpp

@@ -36,6 +36,7 @@ namespace {
 	#define SPDIF_RX_BUFFER_LENGTH AUDIO_BLOCK_SAMPLES
 	const int32_t bufferLength=8*AUDIO_BLOCK_SAMPLES;
 	const uint16_t noSamplerPerIsr=SPDIF_RX_BUFFER_LENGTH/4;
+	const float toFloatAudio= 1.f/pow(2., 23.);
 }
 volatile bool AsyncAudioInputSPDIF3::resetResampler=true;
 
@@ -199,14 +200,13 @@ void AsyncAudioInputSPDIF3::isr(void)
 		#endif
 		float *destR = &(bufferR[buffer_offset]);
 		float *destL = &(bufferL[buffer_offset]);
-		const float factor= pow(2., 23.)+1;
 		do {			
 			int32_t n=(*src) & 0x800000 ? (*src)|0xFF800000  : (*src) & 0xFFFFFF;
-			*destL++ = (float)(n)/factor;
+			*destL++ = (float)(n)*toFloatAudio;
 			++src;
 
 			n=(*src) & 0x800000 ? (*src)|0xFF800000  : (*src) & 0xFFFFFF;
-			*destR++ = (float)(n)/factor;
+			*destR++ = (float)(n)*toFloatAudio;
 			++src;
 		} while (src < end);
 		buffer_offset=(buffer_offset+SPDIF_RX_BUFFER_LENGTH/4)%bufferLength;
@@ -280,8 +280,9 @@ void AsyncAudioInputSPDIF3::configure(){
 			if (abs(frequDiff) > 0.01 || !_resampler.initialized()){
 				//the new sample frequency differs from the last one -> configure the _resampler again
 				_inputFrequency=inputF;		
-				const int32_t targetLatency=round(_targetLatencyS*inputF);
 				_targetLatencyS=max(0.001,(noSamplerPerIsr*3./2./_inputFrequency));
+				_maxLatency=max(2.*_blockDuration, 2*noSamplerPerIsr/_inputFrequency);
+				const int32_t targetLatency=round(_targetLatencyS*inputF);
 				__disable_irq();
 				resample_offset =  targetLatency <= buffer_offset ? buffer_offset - targetLatency : bufferLength -(targetLatency-buffer_offset);
 				__enable_irq();
@@ -402,8 +403,9 @@ void AsyncAudioInputSPDIF3::update(void)
 double AsyncAudioInputSPDIF3::getInputFrequency() const{
 	__disable_irq();
 	double f=_lastValidInputFrequ;
+	bool l=locked;
 	__enable_irq();
-	return f;
+	return l ? f : 0.;
 }
 double AsyncAudioInputSPDIF3::getTargetLantency() const {
 	__disable_irq();
@@ -411,6 +413,12 @@ double AsyncAudioInputSPDIF3::getTargetLantency() const {
 	__enable_irq();
 	return l ;
 }
+double AsyncAudioInputSPDIF3::getAttenuation() const{
+	return _resampler.getAttenuation();
+}
+int32_t AsyncAudioInputSPDIF3::getHalfFilterLength() const{
+	return _resampler.getHalfFilterLength();
+}
 void AsyncAudioInputSPDIF3::config_spdifIn(){
 	//CCM Clock Gating Register 5, imxrt1060_rev1.pdf page 1145
 	CCM_CCGR5 |=CCM_CCGR5_SPDIF(CCM_CCGR_ON); //turn spdif clock on - necessary for receiver!

async_input_spdif3.h

@@ -51,6 +51,8 @@ public:
 	double getInputFrequency() const;
 	bool isLocked() const;
 	double getTargetLantency() const;
+	double getAttenuation() const;
+	int32_t getHalfFilterLength() const;
 protected:	
 	static DMAChannel dma;
 	static void isr(void);
@@ -84,10 +86,10 @@ private:
 	
 	volatile double _bufferedTime;
 	volatile double _lastValidInputFrequ;
-	double _inputFrequency;
+	double _inputFrequency=0.;
 	double _targetLatencyS;	//target latency [seconds]
-	const double _blockDuration=AUDIO_BLOCK_SAMPLES/AUDIO_SAMPLE_RATE; //[seconds] 
-	const double _maxLatency=2.*_blockDuration;
+	const double _blockDuration=AUDIO_BLOCK_SAMPLES/AUDIO_SAMPLE_RATE_EXACT; //[seconds] 
+	double _maxLatency=2.*_blockDuration;
 
 #ifdef DEBUG_SPDIF_IN
 	static volatile bool bufferOverflow;