Updates pull request from Roman Tsypuk to convert the build system from

ant to gradle.  Removes linux and windows application launch scripts and
produces an executable jar with all resources included.

src/main/java/io/github/dsheirer/audio/invert/AudioInverter.java

@@ -0,0 +1,85 @@
+/*******************************************************************************
+ *     SDR Trunk 
+ *     Copyright (C) 2014 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/>
+ ******************************************************************************/
+package io.github.dsheirer.audio.invert;
+
+import io.github.dsheirer.audio.InversionFrequency;
+import io.github.dsheirer.sample.real.RealSampleListener;
+import io.github.dsheirer.dsp.filter.Filters;
+import io.github.dsheirer.dsp.filter.FloatFIRFilter;
+import io.github.dsheirer.dsp.mixer.Oscillator;
+
+/**
+ * Applies audio inversion (or un-inversion) to a broadcast of float audio samples
+ * by multiplying each successive sample by either a 1 or a -1 value.
+ */
+public class AudioInverter implements RealSampleListener
+{
+	private Oscillator mSineWaveGenerator;
+	private FloatFIRFilter mPostInversionLowPassFilter;
+	private RealSampleListener mListener;
+	
+	public AudioInverter( int inversionFrequency, int sampleRate )
+	{
+		mSineWaveGenerator = new Oscillator( inversionFrequency, sampleRate );
+		
+		mPostInversionLowPassFilter = new FloatFIRFilter( 
+				Filters.FIRLP_55TAP_48000FS_3000FC.getCoefficients(), 1.04f );
+
+		mPostInversionLowPassFilter.setListener( new FilteredSampleProcessor() );
+	}
+	
+	public AudioInverter( InversionFrequency frequency, int sampleRate )
+	{
+		this( frequency.getFrequency(), sampleRate );
+	}
+	
+    public void setListener( RealSampleListener listener )
+    {
+	    mListener = listener;
+    }
+
+	@Override
+    public void receive( float sample )
+    {
+		//Multiply the sample by the folding frequency and then send it to
+		//the low pass filter
+		if( mPostInversionLowPassFilter != null )
+		{
+			mPostInversionLowPassFilter.receive( 
+					sample * mSineWaveGenerator.getFloat() );
+			
+			mSineWaveGenerator.rotate();
+		}
+    }
+	
+	/**
+	 * Simple class to receive the output of the FIR low pass filter and then
+	 * send it to the registered listener(s)
+	 */
+	class FilteredSampleProcessor implements RealSampleListener
+	{
+		@Override
+        public void receive( float sample )
+        {
+			if( mListener != null )
+			{
+				mListener.receive( sample );
+			}
+        }
+	}
+}