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/convert/MP3AudioConverter.java

@@ -0,0 +1,96 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2016 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.convert;
+
+import io.github.dsheirer.audio.AudioFormats;
+import io.github.dsheirer.audio.AudioPacket;
+import io.github.dsheirer.audio.AudioUtils;
+import net.sourceforge.lame.lowlevel.LameEncoder;
+import net.sourceforge.lame.mp3.Lame;
+import net.sourceforge.lame.mp3.MPEGMode;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.ByteArrayOutputStream;
+import java.util.Arrays;
+import java.util.List;
+
+public class MP3AudioConverter implements IAudioConverter
+{
+    private final static Logger mLog = LoggerFactory.getLogger( MP3AudioConverter.class );
+    public static final int AUDIO_QUALITY = Lame.QUALITY_LOW;
+    private LameEncoder mEncoder;
+    private ByteArrayOutputStream mMP3Stream = new ByteArrayOutputStream();
+    private byte[] mMP3Buffer;
+
+    /**
+     * Converts PCM 8kHz 16-bit Little Endian audio packets to Mono, Low Quality MP3 compressed audio.
+     *
+     * @param bitRate for converted MP3 audio
+     * @param variableBitRate (VBR) true or false for constant bit rate (CBR)
+     */
+    public MP3AudioConverter(int bitRate, boolean variableBitRate)
+    {
+        mEncoder = new LameEncoder(AudioFormats.PCM_SIGNED_8KHZ_16BITS_MONO,
+                bitRate, MPEGMode.MONO, AUDIO_QUALITY, variableBitRate);
+
+        mMP3Buffer = new byte[mEncoder.getPCMBufferSize()];
+    }
+
+    @Override
+    public byte[] convert(List<AudioPacket> audioPackets)
+    {
+        mMP3Stream.reset();
+
+        byte[] pcmBytes = AudioUtils.convertTo16BitSamples(audioPackets);
+
+        int pcmBufferSize = Math.min(mMP3Buffer.length, pcmBytes.length);
+
+        int mp3BufferSize = 0;
+
+        int pcmBytesPosition = 0;
+
+        try
+        {
+            while (0 < (mp3BufferSize = mEncoder.encodeBuffer(pcmBytes, pcmBytesPosition, pcmBufferSize, mMP3Buffer)))
+            {
+                pcmBytesPosition += pcmBufferSize;
+                pcmBufferSize = Math.min(mMP3Buffer.length, pcmBytes.length - pcmBytesPosition);
+                mMP3Stream.write(mMP3Buffer, 0, mp3BufferSize);
+            }
+
+            return mMP3Stream.toByteArray();
+        }
+        catch(Exception e)
+        {
+            mLog.error("There was an error converting audio to MP3: " + e.getMessage());
+            return new byte[0];
+        }
+    }
+
+    @Override
+    public byte[] flush()
+    {
+        byte[] lastPartialFrame = new byte[mEncoder.getMP3BufferSize()];
+
+        int length = mEncoder.encodeFinish(lastPartialFrame);
+
+        return Arrays.copyOf(lastPartialFrame, length);
+    }
+}