add moving average to NFM squelch

5 files changed, 63 insertions, 1 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 941082a..209504e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,6 +39,7 @@ set(sdrbase_SOURCES
 	sdrbase/dsp/interpolator.cpp
 	sdrbase/dsp/inthalfbandfilter.cpp
 	sdrbase/dsp/lowpass.cpp
+	sdrbase/dsp/movingaverage.cpp
 	sdrbase/dsp/nco.cpp
 	sdrbase/dsp/pidcontroller.cpp
 	sdrbase/dsp/samplefifo.cpp
@@ -97,6 +98,7 @@ set(sdrbase_HEADERS
 	include-gpl/dsp/interpolator.h
 	include-gpl/dsp/inthalfbandfilter.h
 	include-gpl/dsp/lowpass.h
+	include-gpl/dsp/movingaverage.h
 	include-gpl/dsp/nco.h
 	sdrbase/dsp/pidcontroller.h
 	include/dsp/samplefifo.h
diff --git a/include-gpl/dsp/movingaverage.h b/include-gpl/dsp/movingaverage.h
new file mode 100644
index 0000000..c08058b
--- /dev/null
+++ b/include-gpl/dsp/movingaverage.h
@@ -0,0 +1,53 @@
+#ifndef INCLUDE_MOVINGAVERAGE_H
+#define INCLUDE_MOVINGAVERAGE_H
+
+#include <vector>
+#include "dsp/dsptypes.h"
+
+class MovingAverage {
+public:
+	MovingAverage() :
+		m_history(),
+		m_sum(0),
+		m_ptr(0)
+	{
+	}
+
+	MovingAverage(int historySize, Real initial) :
+		m_history(historySize, initial),
+		m_sum(historySize * initial),
+		m_ptr(0)
+	{
+	}
+
+	void resize(int historySize, Real initial)
+	{
+		m_history.resize(historySize);
+		for(size_t i = 0; i < m_history.size(); i++)
+			m_history[i] = initial;
+		m_sum = m_history.size() * initial;
+		m_ptr = 0;
+	}
+
+	void feed(Real value)
+	{
+		m_sum -= m_history[m_ptr];
+		m_history[m_ptr] = value;
+		m_sum += value;
+		m_ptr++;
+		if(m_ptr >= m_history.size())
+			m_ptr = 0;
+	}
+
+	Real average() const
+	{
+		return m_sum / (Real)m_history.size();
+	}
+
+protected:
+	std::vector<Real> m_history;
+	Real m_sum;
+	int m_ptr;
+};
+
+#endif // INCLUDE_MOVINGAVERAGE_H
diff --git a/plugins/demod/nfm/nfmdemod.cpp b/plugins/demod/nfm/nfmdemod.cpp
index 7324852..c6179ab 100644
--- a/plugins/demod/nfm/nfmdemod.cpp
+++ b/plugins/demod/nfm/nfmdemod.cpp
@@ -42,6 +42,8 @@ NFMDemod::NFMDemod(AudioFifo* audioFifo, SampleSink* sampleSink) :
 
 	m_audioBuffer.resize(256);
 	m_audioBufferFill = 0;
+
+	m_movingAverage.resize(16, 0);
 }
 
 NFMDemod::~NFMDemod()
@@ -69,7 +71,9 @@ void NFMDemod::feed(SampleVector::const_iterator begin, SampleVector::const_iter
 		if(m_interpolator.interpolate(&m_sampleDistanceRemain, c, &consumed, &ci)) {
 			m_sampleBuffer.push_back(Sample(ci.real() * 32768.0, ci.imag() * 32768.0));
 
-			if((ci.real() * ci.real() + ci.imag() * ci.imag()) >= m_squelchLevel)
+			m_movingAverage.feed(ci.real() * ci.real() + ci.imag() * ci.imag());
+
+			if(m_movingAverage.average() >= m_squelchLevel)
 				m_squelchState = m_sampleRate / 100;
 
 			if(m_squelchState > 0) {
diff --git a/plugins/demod/nfm/nfmdemod.h b/plugins/demod/nfm/nfmdemod.h
index c3e1e6e..4826f33 100644
--- a/plugins/demod/nfm/nfmdemod.h
+++ b/plugins/demod/nfm/nfmdemod.h
@@ -23,6 +23,7 @@
 #include "dsp/nco.h"
 #include "dsp/interpolator.h"
 #include "dsp/lowpass.h"
+#include "dsp/movingaverage.h"
 #include "audio/audiofifo.h"
 #include "util/message.h"
 
@@ -90,6 +91,7 @@ private:
 	int m_squelchState;
 
 	Complex m_lastSample;
+	MovingAverage m_movingAverage;
 
 	AudioVector m_audioBuffer;
 	uint m_audioBufferFill;
diff --git a/sdrbase/dsp/movingaverage.cpp b/sdrbase/dsp/movingaverage.cpp
new file mode 100644
index 0000000..dcf8d55
--- /dev/null
+++ b/sdrbase/dsp/movingaverage.cpp
@@ -0,0 +1 @@
+#include "dsp/movingaverage.h"