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/audio/AudioChannelPanel.java

@@ -20,7 +20,6 @@ import settings.Setting;
 import settings.SettingChangeListener;
 import settings.SettingsManager;
 import alias.Alias;
-import audio.AudioEvent.Type;
 import audio.metadata.AudioMetadata;
 import audio.metadata.Metadata;
 import audio.metadata.MetadataType;

src/audio/AudioManager.java

@@ -1,6 +1,25 @@
 package audio;
 
+/*******************************************************************************
+ *     SDR Trunk 
+ *     Copyright (C) 2014,2015 Dennis Sheirer
+ * 
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ * 
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ * 
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ ******************************************************************************/
+
 import java.util.ArrayList;
+
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;

src/audio/AudioModule.java

@@ -18,7 +18,6 @@ import audio.squelch.SquelchState;
 import controller.channel.ChannelEvent;
 import controller.channel.IChannelEventListener;
 import dsp.filter.Filters;
-import dsp.filter.dc.AveragingDCRemovalFilter_RB;
 import dsp.filter.dc.DCRemovalFilter_RB;
 import dsp.filter.fir.real.RealFIRFilter_R_R;
 
@@ -73,7 +72,7 @@ public class AudioModule extends Module implements IAudioPacketProvider,
 		
 		if( mRemoveDC )
 		{
-			mDCRemovalFilter = new AveragingDCRemovalFilter_RB( DC_REMOVAL_RATIO );
+			mDCRemovalFilter = new DCRemovalFilter_RB( DC_REMOVAL_RATIO );
 			mDCRemovalFilter.setListener( this );
 		}
 	}

src/audio/inverted/AudioAdapter.java

@@ -17,10 +17,10 @@
  ******************************************************************************/
 package audio.inverted;
 
-import util.Oscillator;
 import dsp.filter.FilterFactory;
 import dsp.filter.FloatFIRFilter;
 import dsp.filter.Window.WindowType;
+import dsp.mixer.Oscillator;
 
 /**
  * Based on the AudioType applied, produces normal, muted, or audio inverted

src/audio/inverted/AudioInverter.java

@@ -19,9 +19,9 @@ package audio.inverted;
 
 import audio.InversionFrequency;
 import sample.real.RealSampleListener;
-import util.Oscillator;
 import dsp.filter.Filters;
 import dsp.filter.FloatFIRFilter;
+import dsp.mixer.Oscillator;
 
 /**
  * Applies audio inversion (or un-inversion) to a stream of float audio samples

src/audio/output/AudioOutput.java

@@ -4,7 +4,6 @@ import java.util.concurrent.LinkedTransferQueue;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.atomic.AtomicBoolean;
 
-import javax.sound.sampled.BooleanControl;
 import javax.sound.sampled.FloatControl;
 
 import org.slf4j.Logger;

src/audio/output/StereoAudioOutput.java

@@ -10,7 +10,6 @@ import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import javax.sound.sampled.BooleanControl;
-import javax.sound.sampled.Control;
 import javax.sound.sampled.FloatControl;
 import javax.sound.sampled.LineUnavailableException;
 import javax.sound.sampled.Mixer;