Corrected Highpass and Bandpass filters normalization. Implements #642

plugins/channelrx/demodam/amdemodsink.cpp

@@ -189,7 +189,6 @@ void AMDemodSink::processOneSample(Complex &ci)
         if (m_settings.m_bandpassEnable)
         {
             demod = m_bandpass.filter(demod);
-            demod /= 301.0f;
         }
         else
         {

plugins/channelrx/demodnfm/nfmdemodsink.cpp

@@ -121,7 +121,7 @@ void NFMDemodSink::processOneSample(Complex &ci)
 
     if (m_settings.m_deltaSquelch)
     {
-        if (m_afSquelch.analyze(demod * m_discriCompensation))
+        if (m_afSquelch.analyze(demod))
         {
             m_afSquelchOpen = m_afSquelch.evaluate(); // ? m_squelchGate + m_squelchDecay : 0;
 
@@ -132,7 +132,7 @@ void NFMDemodSink::processOneSample(Complex &ci)
 
         if (m_afSquelchOpen)
         {
-            m_squelchDelayLine.write(demod * m_discriCompensation);
+            m_squelchDelayLine.write(demod);
 
             if (m_squelchCount < 2*m_squelchGate) {
                 m_squelchCount++;
@@ -159,7 +159,7 @@ void NFMDemodSink::processOneSample(Complex &ci)
         }
         else
         {
-            m_squelchDelayLine.write(demod * m_discriCompensation);
+            m_squelchDelayLine.write(demod);
 
             if (m_squelchCount < 2*m_squelchGate) {
                 m_squelchCount++;
@@ -179,7 +179,7 @@ void NFMDemodSink::processOneSample(Complex &ci)
         {
             if (m_settings.m_ctcssOn)
             {
-                Real ctcss_sample = m_ctcssLowpass.filter(demod * m_discriCompensation);
+                Real ctcss_sample = m_ctcssLowpass.filter(demod);
 
                 if ((m_sampleCount & 7) == 7) // decimate 48k -> 6k
                 {
@@ -224,7 +224,7 @@ void NFMDemodSink::processOneSample(Complex &ci)
             else
             {
                 if (m_settings.m_highPass) {
-                    sample = m_bandpass.filter(m_squelchDelayLine.readBack(m_squelchGate)) * m_settings.m_volume;
+                    sample = m_bandpass.filter(m_squelchDelayLine.readBack(m_squelchGate)) * m_settings.m_volume * 301.0f;
                 } else {
                     sample = m_lowpass.filter(m_squelchDelayLine.readBack(m_squelchGate)) * m_settings.m_volume * 301.0f;
                 }
@@ -375,17 +375,13 @@ void NFMDemodSink::applyAudioSampleRate(unsigned int sampleRate)
 
     if (sampleRate < 16000) {
         m_afSquelch.setCoefficients(sampleRate/2000, 600, sampleRate, 200, 0, afSqTones_lowrate); // 0.5ms test period, 300ms average span, audio SR, 100ms attack, no decay
-
     } else {
         m_afSquelch.setCoefficients(sampleRate/2000, 600, sampleRate, 200, 0, afSqTones); // 0.5ms test period, 300ms average span, audio SR, 100ms attack, no decay
     }
 
-    m_discriCompensation = (sampleRate/48000.0f);
-    m_discriCompensation *= sqrt(m_discriCompensation);
-
     m_phaseDiscri.setFMScaling((8.0f*sampleRate) / static_cast<float>(m_settings.m_fmDeviation)); // integrate 4x factor
     m_audioFifo.setSize(sampleRate);
     m_squelchDelayLine.resize(sampleRate/2);
 
     m_audioSampleRate = sampleRate;
-}
+}

plugins/channelrx/demodnfm/nfmdemodsink.h

@@ -104,8 +104,6 @@ private:
     uint m_audioBufferFill;
     AudioFifo m_audioFifo;
 
-	float m_discriCompensation; //!< compensation factor that depends on audio rate (1 for 48 kS/s)
-
 	NCO m_nco;
 	Interpolator m_interpolator;
 	Real m_interpolatorDistance;

plugins/channelrx/udpsink/udpsinksink.cpp

@@ -256,7 +256,6 @@ void UDPSinkSink::feed(const SampleVector::const_iterator& begin, const SampleVe
                 {
                     double demodf = sqrt(inMagSq);
                     demodf = m_bandpass.filter(demodf);
-                    demodf /= 301.0;
                     Real amplitude = demodf * agcFactor * m_settings.m_gain;
                     FixReal demod = (FixReal) amplitude;
                     udpWriteMono(demod);

plugins/channeltx/modnfm/nfmmodsource.cpp

@@ -134,14 +134,11 @@ void NFMModSource::modulateSample()
     calculateLevel(t);
     m_audioBufferFill++;
 
-    if (m_settings.m_ctcssOn)
+    // 0.625 = 1/1.25 (heuristic)
-    {
+    if (m_settings.m_ctcssOn) {
-        m_modPhasor += (m_settings.m_fmDeviation / (float) m_audioSampleRate) * (0.85f * m_bandpass.filter(t) + 0.15f * 189.0f * m_ctcssNco.next()) * (M_PI / 189.0f);
+        m_modPhasor += (m_settings.m_fmDeviation / (float) m_audioSampleRate) * (0.85f * m_bandpass.filter(t) + 0.15f * 0.625f * m_ctcssNco.next()) * (M_PI / 0.625f);
-    }
+    } else {
-    else
+        m_modPhasor += (m_settings.m_fmDeviation / (float) m_audioSampleRate) * m_bandpass.filter(t) * (M_PI / 0.625f);
-    {
-        // 378 = 302 * 1.25; 302 = number of filter taps (established experimentally) and 189 = 378/2 for 2*PI
-        m_modPhasor += (m_settings.m_fmDeviation / (float) m_audioSampleRate) * m_bandpass.filter(t) * (M_PI / 189.0f);
     }
 
     // limit phasor range to ]-pi,pi]
@@ -368,4 +365,4 @@ void NFMModSource::applyChannelSettings(int channelSampleRate, int channelFreque
 
     m_channelSampleRate = channelSampleRate;
     m_channelFrequencyOffset = channelFrequencyOffset;
-}
+}

sdrbase/dsp/bandpass.h

@@ -23,27 +23,34 @@ public:
 		int i;
 
 		// check constraints
-		if(!(nTaps & 1)) {
+		if (!(nTaps & 1))
+		{
 			qDebug("Bandpass filter has to have an odd number of taps");
 			nTaps++;
 		}
 
 		// make room
 		m_samples.resize(nTaps);
-		for(int i = 0; i < nTaps; i++)
+
+		for (int i = 0; i < nTaps; i++) {
 			m_samples[i] = 0;
+		}
+
 		m_ptr = 0;
 		m_taps.resize(nTaps / 2 + 1);
 		taps_lp.resize(nTaps / 2 + 1);
 		taps_hp.resize(nTaps / 2 + 1);
 
 		// generate Sinc filter core
-		for(i = 0; i < nTaps / 2 + 1; i++) {
+		for (i = 0; i < nTaps / 2 + 1; i++)
-			if(i == (nTaps - 1) / 2) {
+		{
+			if (i == (nTaps - 1) / 2)
+			{
 				taps_lp[i] = Wch / M_PI;
 				taps_hp[i] = -(Wcl / M_PI);
 			}
-			else {
+			else
+			{
 				taps_lp[i] = sin(((double)i - ((double)nTaps - 1.0) / 2.0) * Wch) / (((double)i - ((double)nTaps - 1.0) / 2.0) * M_PI);
 				taps_hp[i] = -sin(((double)i - ((double)nTaps - 1.0) / 2.0) * Wcl) / (((double)i - ((double)nTaps - 1.0) / 2.0) * M_PI);
 			}
@@ -52,7 +59,8 @@ public:
 		taps_hp[(nTaps - 1) / 2] += 1;
 
 		// apply Hamming window and combine lowpass and highpass
-		for(i = 0; i < nTaps / 2 + 1; i++) {
+		for (i = 0; i < nTaps / 2 + 1; i++)
+		{
 			taps_lp[i] *= 0.54 + 0.46 * cos((2.0 * M_PI * ((double)i - ((double)nTaps - 1.0) / 2.0)) / (double)nTaps);
 			taps_hp[i] *= 0.54 + 0.46 * cos((2.0 * M_PI * ((double)i - ((double)nTaps - 1.0) / 2.0)) / (double)nTaps);
 			m_taps[i] = -(taps_lp[i]+taps_hp[i]);
@@ -63,13 +71,13 @@ public:
 		// normalize
 		Real sum = 0;
 
-		for(i = 0; i < (int)m_taps.size() - 1; i++) {
+		for (i = 0; i < (int)m_taps.size() - 1; i++) {
 			sum += m_taps[i] * 2;
 		}
 
-		sum += m_taps[i];
+		sum += m_taps[i] - 1;
 
-		for(i = 0; i < (int)m_taps.size(); i++) {
+		for (i = 0; i < (int)m_taps.size(); i++) {
 			m_taps[i] /= sum;
 		}
 	}
@@ -84,8 +92,7 @@ public:
 		m_samples[m_ptr] = sample;
 		size = m_samples.size(); // Valgrind optim (2)
 
-		while(b < 0)
+		while (b < 0) {
-		{
 			b += size;
 		}
 
@@ -96,15 +103,13 @@ public:
 			acc += (m_samples[a] + m_samples[b]) * m_taps[i];
 			a++;
 
-			while (a >= size)
+			while (a >= size) {
-			{
 				a -= size;
 			}
 
 			b--;
 
-			while(b < 0)
+			while(b < 0) {
-			{
 				b += size;
 			}
 		}
@@ -113,8 +118,7 @@ public:
 
 		m_ptr++;
 
-		while (m_ptr >= size)
+		while (m_ptr >= size) {
-		{
 			m_ptr -= size;
 		}
 

sdrbase/dsp/highpass.h

@@ -16,39 +16,51 @@ public:
 		int i;
 
 		// check constraints
-		if(!(nTaps & 1)) {
+		if (!(nTaps & 1))
+		{
 			qDebug("Highpass filter has to have an odd number of taps");
 			nTaps++;
 		}
 
 		// make room
 		m_samples.resize(nTaps);
-		for(int i = 0; i < nTaps; i++)
+
+		for (int i = 0; i < nTaps; i++) {
 			m_samples[i] = 0;
+		}
+
 		m_ptr = 0;
 		m_taps.resize(nTaps / 2 + 1);
 
 		// generate Sinc filter core for lowpass but inverting every other tap for highpass keeping center tap
-		for(i = 0; i < nTaps / 2 + 1; i++) {
+		for (i = 0; i < nTaps / 2 + 1; i++)
-			if(i == (nTaps - 1) / 2)
+		{
+			if (i == (nTaps - 1) / 2) {
 				m_taps[i] = -(Wc / M_PI);
-			else
+			} else {
 				m_taps[i] = -sin(((double)i - ((double)nTaps - 1.0) / 2.0) * Wc) / (((double)i - ((double)nTaps - 1.0) / 2.0) * M_PI);
+			}
 		}
 
 		m_taps[(nTaps - 1) / 2] += 1;
 
 		// apply Hamming window
-		for(i = 0; i < nTaps / 2 + 1; i++)
+		for (i = 0; i < nTaps / 2 + 1; i++) {
 			m_taps[i] *= 0.54 + 0.46 * cos((2.0 * M_PI * ((double)i - ((double)nTaps - 1.0) / 2.0)) / (double)nTaps);
+		}
 
 		// normalize
 		Real sum = 0;
-		for(i = 0; i < (int)m_taps.size() - 1; i++)
+
+		for (i = 0; i < (int)m_taps.size() - 1; i++) {
 			sum += m_taps[i] * 2;
-		sum += m_taps[i];
+		}
-		for(i = 0; i < (int)m_taps.size(); i++)
+
+		sum += m_taps[i] - 1;
+
+		for (i = 0; i < (int)m_taps.size(); i++) {
 			m_taps[i] /= sum;
+		}
 	}
 
 	Type filter(Type sample)
@@ -61,8 +73,7 @@ public:
 		m_samples[m_ptr] = sample;
 		size = m_samples.size(); // Valgrind optim (2)
 
-		while(b < 0)
+		while (b < 0) {
-		{
 			b += size;
 		}
 
@@ -73,15 +84,13 @@ public:
 			acc +=  (m_samples[a] + m_samples[b]) * m_taps[i];
 			a++;
 
-			while (a >= size)
+			while (a >= size) {
-			{
 				a -= size;
 			}
 
 			b--;
 
-			while (b < 0)
+			while (b < 0) {
-			{
 				b += size;
 			}
 		}
@@ -89,8 +98,7 @@ public:
 		acc += m_samples[a] * m_taps[i];
 		m_ptr++;
 
-		while (m_ptr >= size)
+		while (m_ptr >= size) {
-		{
 			m_ptr -= size;
 		}
 

sdrbase/dsp/lowpass.h

@@ -16,37 +16,49 @@ public:
 		int i;
 
 		// check constraints
-		if(!(nTaps & 1)) {
+		if (!(nTaps & 1))
+		{
 			qDebug("Lowpass filter has to have an odd number of taps");
 			nTaps++;
 		}
 
 		// make room
 		m_samples.resize(nTaps);
-		for(int i = 0; i < nTaps; i++)
+
+		for (int i = 0; i < nTaps; i++) {
 			m_samples[i] = 0;
+		}
+
 		m_ptr = 0;
 		m_taps.resize(nTaps / 2 + 1);
 
 		// generate Sinc filter core
-		for(i = 0; i < nTaps / 2 + 1; i++) {
+		for (i = 0; i < nTaps / 2 + 1; i++)
-			if(i == (nTaps - 1) / 2)
+		{
+			if(i == (nTaps - 1) / 2) {
 				m_taps[i] = Wc / M_PI;
-			else
+			} else {
 				m_taps[i] = sin(((double)i - ((double)nTaps - 1.0) / 2.0) * Wc) / (((double)i - ((double)nTaps - 1.0) / 2.0) * M_PI);
+			}
 		}
 
 		// apply Hamming window
-		for(i = 0; i < nTaps / 2 + 1; i++)
+		for (i = 0; i < nTaps / 2 + 1; i++) {
 			m_taps[i] *= 0.54 + 0.46 * cos((2.0 * M_PI * ((double)i - ((double)nTaps - 1.0) / 2.0)) / (double)nTaps);
+		}
 
 		// normalize
 		Real sum = 0;
-		for(i = 0; i < (int)m_taps.size() - 1; i++)
+
+		for (i = 0; i < (int)m_taps.size() - 1; i++) {
 			sum += m_taps[i] * 2;
+		}
+
 		sum += m_taps[i];
-		for(i = 0; i < (int)m_taps.size(); i++)
+
+		for (i = 0; i < (int)m_taps.size(); i++) {
 			m_taps[i] /= sum;
+		}
 	}
 
 	Type filter(Type sample)
@@ -59,8 +71,7 @@ public:
 		m_samples[m_ptr] = sample;
 		size = m_samples.size(); // Valgrind optim (2)
 
-		while (b < 0)
+		while (b < 0) {
-		{
 			b += size;
 		}
 
@@ -71,15 +82,13 @@ public:
 			acc += (m_samples[a] + m_samples[b]) * m_taps[i];
 			a++;
 
-			while (a >= size)
+			while (a >= size) {
-			{
 				a -= size;
 			}
 
 			b--;
 
-			while(b < 0)
+			while(b < 0) {
-			{
 				b += size;
 			}
 		}
@@ -87,8 +96,7 @@ public:
 		acc += m_samples[a] * m_taps[i];
 		m_ptr++;
 
-		while(m_ptr >= size)
+		while(m_ptr >= size) {
-		{
 			m_ptr -= size;
 		}