#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/AudioPlaybackDeviceManager.java

@@ -0,0 +1,130 @@
+/*
+ * *****************************************************************************
+ * 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 java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import javax.sound.sampled.AudioFormat;
+import javax.sound.sampled.AudioSystem;
+import javax.sound.sampled.DataLine;
+import javax.sound.sampled.Line;
+import javax.sound.sampled.Mixer;
+
+/**
+ * Audio playback device manager.
+ */
+public class AudioPlaybackDeviceManager
+{
+    /**
+     * Always returns the first available device in the system.
+     */
+    public static AudioPlaybackDeviceDescriptor getDefaultAudioPLaybackDevice()
+    {
+        List<AudioPlaybackDeviceDescriptor> devices = getAudioPlaybackDevices();
+
+        if(!devices.isEmpty())
+        {
+            return devices.getFirst();
+        }
+
+        return null;
+    }
+
+    /**
+     * Finds the matching audio playback device
+     * @param name of the device
+     * @param channels count
+     * @return matching entry or the default playback device.
+     */
+    public static AudioPlaybackDeviceDescriptor getAudioPlaybackDevice(String name, int channels)
+    {
+        for(AudioPlaybackDeviceDescriptor device: getAudioPlaybackDevices())
+        {
+            if(device.getMixerInfo().getName().equals(name) && device.getAudioFormat().getChannels() == channels)
+            {
+                return device;
+            }
+        }
+
+        return getDefaultAudioPLaybackDevice();
+    }
+
+    public static List<AudioPlaybackDeviceDescriptor> getAudioPlaybackDevices()
+    {
+        List<AudioPlaybackDeviceDescriptor> devices = new ArrayList<>();
+
+        Mixer.Info[] mixerInfos = AudioSystem.getMixerInfo();
+
+        for(Mixer.Info mixerInfo : mixerInfos)
+        {
+            Mixer mixer = AudioSystem.getMixer(mixerInfo);
+
+            if(mixer != null)
+            {
+                List<AudioFormat> discoveredFormats = new ArrayList<>();
+
+                for(Line.Info sourceLineInfo : mixer.getSourceLineInfo())
+                {
+                    if(sourceLineInfo instanceof DataLine.Info dataLineInfo)
+                    {
+                        for(AudioFormat audioFormat : dataLineInfo.getFormats())
+                        {
+                            if(!audioFormat.isBigEndian() &&
+                                audioFormat.getSampleSizeInBits() == 16 &&
+                               !discoveredFormats.contains(audioFormat) &&
+                                audioFormat.getChannels() <= 2) //TODO: remove the 2 channels max restriction once supported
+                            {
+                                if(audioFormat.getSampleRate() == AudioSystem.NOT_SPECIFIED)
+                                {
+                                    discoveredFormats.add(audioFormat);
+                                    //Modify the format for 8 kHz sample rate
+                                    AudioFormat updatedFormat = new AudioFormat(AudioFormat.Encoding.PCM_SIGNED,
+                                8000, 16, audioFormat.getChannels(), audioFormat.getFrameSize(),
+                                            8000, false);
+                                    devices.add(new AudioPlaybackDeviceDescriptor(mixerInfo, updatedFormat));
+                                }
+                                else if(audioFormat.getSampleRate() == 8000)
+                                {
+                                    discoveredFormats.add(audioFormat);
+                                    devices.add(new AudioPlaybackDeviceDescriptor(mixerInfo, audioFormat));
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        Collections.sort(devices);
+        return devices;
+    }
+
+
+    static void main()
+    {
+        List<AudioPlaybackDeviceDescriptor> devices = getAudioPlaybackDevices();
+        for(AudioPlaybackDeviceDescriptor device : devices)
+        {
+            System.out.println(device);
+        }
+    }
+}