#2356 Audio playback redesign. Resolves audio playback issue on some (e.g. Kubuntu) systems. For stereo playback, (#2359)

consolidates left and right channels into a single playback channel.  Implements continuous audio streaming using
silence to fill the gaps to avoid mixer source data line start/stop issues.  Code structure is ready to layer on
multi-channel (ie 5.1 or 7.1) audio playback devices, but that hasn't been tested.

Co-authored-by: denny <dennis.sheirer@gmail.com>

src/main/java/io/github/dsheirer/audio/playback/AudioProviderMultiChannel.java

@@ -0,0 +1,123 @@
+/*
+ * *****************************************************************************
+ * Copyright (C) 2014-2026 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.playback;
+
+import io.github.dsheirer.preference.UserPreferences;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.ShortBuffer;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import javax.sound.sampled.AudioFormat;
+
+/**
+ * Multi-Channel audio provider implementation.  Provides an interleaved stream of audio from multiple channels.
+ *
+ * Note: this implementation has not been tested for use.
+ */
+public class AudioProviderMultiChannel extends AudioProvider
+{
+    private static ByteBuffer SILENCE;
+    private final List<AudioChannel> mAudioChannels = new ArrayList<>();
+    private final AudioFormat mAudioFormat;
+
+    /**
+     * Constructs a multi-channel audio provider
+     * @param userPreferences for this provider
+     * @param audioFormat for this provider
+     */
+    public AudioProviderMultiChannel(UserPreferences userPreferences, AudioFormat audioFormat)
+    {
+        SILENCE = ByteBuffer.allocate(AudioChannel.SAMPLES_PER_INTERVAL * audioFormat.getChannels());
+
+        for(int channel = 0; channel < audioFormat.getChannels(); channel++)
+        {
+            mAudioChannels.add(new AudioChannel(userPreferences, String.valueOf(channel)));
+        }
+
+        mAudioFormat = audioFormat;
+    }
+
+    @Override
+    public AudioFormat getAudioFormat()
+    {
+        return mAudioFormat;
+    }
+
+    /**
+     * Access the next buffer of audio.
+     * @return next buffer or null if there is no audio available
+     */
+    @Override
+    public ByteBuffer getAudio()
+    {
+        float[][] samples = new float[mAudioChannels.size()][];
+        boolean hasAudio = false;
+
+        AudioChannel channel = null;
+
+        for(int x = 0; x < mAudioChannels.size(); x++)
+        {
+            channel = mAudioChannels.get(x);
+            samples[x] = channel.getAudio();
+
+            if(samples[x] == null)
+            {
+                if(!channel.hasAudioSegment())
+                {
+                    channel.clearMetadata();
+                }
+
+                samples[x] = new float[AudioChannel.SAMPLES_PER_INTERVAL];
+            }
+            else
+            {
+                hasAudio = true;
+            }
+        }
+
+        if(!hasAudio)
+        {
+            return SILENCE;
+        }
+
+        ByteBuffer buffer = ByteBuffer.allocate(AudioChannel.SAMPLES_PER_INTERVAL * 2 *
+                mAudioChannels.size()).order(ByteOrder.LITTLE_ENDIAN);
+        ShortBuffer shortBuffer = buffer.asShortBuffer();
+
+        for(int sampleCounter = 0; sampleCounter < AudioChannel.SAMPLES_PER_INTERVAL; sampleCounter++)
+        {
+            for(int channelNumber = 0; channelNumber < mAudioChannels.size(); channelNumber++)
+            {
+                shortBuffer.put((short)(samples[channelNumber][sampleCounter] * Short.MAX_VALUE));
+            }
+        }
+
+        return buffer;
+    }
+
+    @Override
+    public List<AudioChannel> getAudioChannels()
+    {
+        return Collections.unmodifiableList(mAudioChannels);
+    }
+}