Adds airspy USB tuner support and updates the spectral display

component.

-Airspy supported with 10 and 2.5 MSps sample rates.  Additional
decimation may be added later.

-Spectral display updated to include smoothing and filtering options.

Note: the decimated output of a tuner channel from the airspy is
48,076.9 samples per second, versus the normal 48 kHz decimated rate.
This is 1.0015 times the normal rate and doesn't appear to impact the
decoders or audio processing.  Therefore, no fractional resampling has
been added.

src/spectrum/SpectrumPanel.java

@@ -36,8 +36,13 @@ import settings.ColorSetting;
 import settings.ColorSetting.ColorSettingName;
 import settings.Setting;
 import settings.SettingChangeListener;
-import buffer.FloatArrayCircularAveragingBuffer;
 import controller.ResourceManager;
+import dsp.filter.smoothing.GaussianSmoothingFilter;
+import dsp.filter.smoothing.NoSmoothingFilter;
+import dsp.filter.smoothing.RectangularSmoothingFilter;
+import dsp.filter.smoothing.SmoothingFilter;
+import dsp.filter.smoothing.SmoothingFilter.SmoothingType;
+import dsp.filter.smoothing.TriangularSmoothingFilter;
 
 public class SpectrumPanel extends JPanel
 							implements DFTResultsListener,
@@ -51,9 +56,9 @@ public class SpectrumPanel extends JPanel
 	/* Set display bins size to 1, so that we're guaranteed a reset to the 
 	 * correct width once the first sample set arrives */
 	private float[] mDisplayFFTBins = new float[ 1 ];
-	private FloatArrayCircularAveragingBuffer mFFTAveragingBuffer;
 	private int mAveraging = 4;
-	private int mDBScale = -100; //dBm
+	
+	private float mDBScale; 
 
 	/**
 	 * Spectral Display Color Settings
@@ -65,6 +70,11 @@ public class SpectrumPanel extends JPanel
 	private static final String SPECTRUM_AVERAGING_SIZE = "spectrum_averaging_size";
 	private static final int SPECTRUM_TRANSLUCENCY = 128;
 	
+	private static final RenderingHints RENDERING_HINTS = 
+    		new RenderingHints( RenderingHints.KEY_ANTIALIASING, 
+    							RenderingHints.VALUE_ANTIALIAS_ON );
+
+
 
 	private Color mColorSpectrumBackground;
 	private Color mColorSpectrumGradientTop;
@@ -73,11 +83,20 @@ public class SpectrumPanel extends JPanel
 
 	private float mSpectrumInset = 20.0f;
 	
+	private SmoothingFilter mSmoothingFilter = new GaussianSmoothingFilter();
+	
 	private ResourceManager mResourceManager;
 	
 	public SpectrumPanel( ResourceManager resourceManager )
     {
 		mResourceManager = resourceManager;
+		
+		RENDERING_HINTS.put( RenderingHints.KEY_RENDERING, 
+							 RenderingHints.VALUE_RENDER_QUALITY );
+		
+		setSampleSize( 16.0 );
+		
+		mSmoothingFilter.setPointSize( SmoothingFilter.SMOOTHING_DEFAULT );
 
 		getSettings();
 
@@ -89,12 +108,16 @@ public class SpectrumPanel extends JPanel
 		mResourceManager = null;
 	}
 	
+	public void setSampleSize( double sampleSize )
+	{
+		assert( 2.0 <= sampleSize && sampleSize <= 32.0 );
+		
+		mDBScale = -(float)( 20.0 * Math.log10( Math.pow( 2.0, sampleSize ) ) );
+	}
+	
 	public void setAveraging( int size )
 	{
 		mAveraging = size;
-		
-		mFFTAveragingBuffer = 
-				new FloatArrayCircularAveragingBuffer( mAveraging );		
 	}
 	
 	public int getAveraging()
@@ -102,19 +125,6 @@ public class SpectrumPanel extends JPanel
 		return mAveraging;
 	}
 	
-	/**
-	 * Sets the lowest decibel scale value to show on the display
-	 */
-	public void setDBScale( int dbScale )
-	{
-		mDBScale = dbScale;
-	}
-	
-	public int getDBScale()
-	{
-		return mDBScale;
-	}
-	
 	public void clearSpectrum()
 	{
 		mDisplayFFTBins = null;
@@ -180,18 +190,36 @@ public class SpectrumPanel extends JPanel
      */
     public void receive( float[] currentFFTBins )
     {
+    	if( Float.isInfinite( currentFFTBins[ 0 ] ) || Float.isNaN( currentFFTBins[ 0 ] ) )
+		{
+			currentFFTBins = new float[ currentFFTBins.length ];
+		}
+
     	//Construct and/or resize our fft results variables
     	if( mDisplayFFTBins == null || 
     		mDisplayFFTBins.length != currentFFTBins.length )
     	{
-    		mDisplayFFTBins = new float[ currentFFTBins.length ];
+    		mDisplayFFTBins = currentFFTBins;
     	}
 
-    	/**
-    	 * Store the new FFT bins in the buffer and get the average of the FFT
-    	 * bin buffer contents into the display fft bins variable
-    	 */
-    	mDisplayFFTBins = mFFTAveragingBuffer.get( currentFFTBins );
+    	//Smooth across the bins
+    	float[] smoothedBins = mSmoothingFilter.filter( currentFFTBins );
+
+    	//Average bins over multiple frames
+    	if( mAveraging > 1 )
+    	{
+    		float gain = 1.0f / (float)mAveraging;
+    		
+    		for( int x = 0; x < mDisplayFFTBins.length; x++ )
+    		{
+    			mDisplayFFTBins[ x ] += ( smoothedBins[ x ] - mDisplayFFTBins[ x ] ) * gain;
+    		}
+    	}
+    	else
+    	{
+    		mDisplayFFTBins = smoothedBins;
+    	}
+    	
     	
 		repaint();
     }
@@ -204,14 +232,8 @@ public class SpectrumPanel extends JPanel
     	Graphics2D graphics = (Graphics2D) g;
     	graphics.setBackground( mColorSpectrumBackground );
 
-        RenderingHints renderHints = 
-        		new RenderingHints( RenderingHints.KEY_ANTIALIASING, 
-        							RenderingHints.VALUE_ANTIALIAS_ON );
 
-        renderHints.put( RenderingHints.KEY_RENDERING, 
-        				 RenderingHints.VALUE_RENDER_QUALITY );
-
-        graphics.setRenderingHints( renderHints );
+        graphics.setRenderingHints( RENDERING_HINTS );
         
     	drawSpectrum( graphics );
     }
@@ -231,7 +253,7 @@ public class SpectrumPanel extends JPanel
 
     	//Define the gradient
     	GradientPaint gradient = new GradientPaint( 0, 
-    												0, 
+    												getSize().height / 4, 
     												mColorSpectrumGradientTop,
     												0,
     												getSize().height, 
@@ -253,7 +275,7 @@ public class SpectrumPanel extends JPanel
     	{
     		float insideHeight = size.height - mSpectrumInset;
 
-    		float scalor = insideHeight / ( -mDBScale );
+    		float scalor = insideHeight / mDBScale;
 			
     		float insideWidth = size.width;
 
@@ -271,7 +293,7 @@ public class SpectrumPanel extends JPanel
     			}
     			else
     			{
-    				height = (float)( Math.abs( mDisplayFFTBins[ x ] ) * scalor );
+    				height = mDisplayFFTBins[ x ] * scalor;
     				
         			if( height > insideHeight )
         			{
@@ -316,5 +338,54 @@ public class SpectrumPanel extends JPanel
     }
 
 	@Override
-    public void settingDeleted( Setting setting ) {}
+    public void settingDeleted( Setting setting ) {  /* not implemented */ }
+
+	@Override
+	public int getSmoothing()
+	{
+		return mSmoothingFilter.getPointSize();
+	}
+
+	@Override
+	public void setSmoothing( int smoothing )
+	{
+		mSmoothingFilter.setPointSize( smoothing );
+	}
+
+	@Override
+	public SmoothingType getSmoothingType()
+	{
+		return mSmoothingFilter.getSmoothingType();
+	}
+
+	@Override
+	public void setSmoothingType( SmoothingType type )
+	{
+		if( mSmoothingFilter.getSmoothingType() != type )
+		{
+			int pointSize = getSmoothing();
+
+			synchronized ( mSmoothingFilter )
+			{
+				switch( type )
+				{
+					case GAUSSIAN:
+						mSmoothingFilter = new GaussianSmoothingFilter();
+						break;
+					case RECTANGLE:
+						mSmoothingFilter = new RectangularSmoothingFilter();
+						break;
+					case TRIANGLE:
+						mSmoothingFilter = new TriangularSmoothingFilter();
+						break;
+					case NONE:
+					default:
+						mSmoothingFilter = new NoSmoothingFilter();
+						break;
+				}
+			}
+			
+			setSmoothing( pointSize );
+		}
+	}
 }