Allow to adjust playback-speed of the TarsosDSPPlayer

TarsosDSP actually supports this by adjusting parameters
of the wsola implementation.

This way we can avoid stopping/restarting the audio-player
and can simply adjust playback speed at runtime.

src/main/java/org/dstadler/audio/example/AudioWriter.java

@@ -31,6 +31,8 @@ class AudioWriter implements Runnable {
     private ClearablePipedInputStream in;
     private PlayerThread player;
 
+    private String options = "";
+
     public AudioWriter(SeekableRingBuffer<Chunk> buffer, Runnable stopper, BooleanSupplier shouldStop) throws IOException {
         this.buffer = buffer;
         this.stopper = stopper;
@@ -48,9 +50,9 @@ private synchronized void createPipe() throws IOException {
     @Override
     public void run() {
         try {
-            //player.setOptions("");
-
             player = new PlayerThread(in, stopper);
+            player.setOptions(options);
+
             Thread playerThread = new Thread(player, "Player thread");
             playerThread.setDaemon(true);
             playerThread.start();
@@ -92,6 +94,15 @@ private long writeLoop() throws IOException {
         return chunks;
     }
 
+    /**
+     * Allows to empty out current buffers.
+     *
+     * This is usually used to remove chunks in the queue so a shutdown
+     * is performed quickly.
+     *
+     * @throws IOException If clearing buffers or re-creating internal
+     * data-structures fails
+     */
     public void clearBuffer() throws IOException {
         in.clearBuffer();
 
@@ -105,4 +116,26 @@ public void clearBuffer() throws IOException {
             player.triggerRestart(in);
         }
     }
+
+    /**
+     * Allow to set speed of audio playback for the current
+     * implementation of the audio player.
+     *
+     * If the player is already running, the
+     * changed speed is passed to the
+     * current instance.
+     *
+     * If the used implementation of the audio player does not
+     * support tempo-adjustment, nothing happens.
+     *
+     * @param tempo The adjusted tempo in terms of multiplay of real-time playback,
+     *              1.0f for real-time playback, e.g. 1.5f for fairly fast playback
+     */
+    public void setTempo(float tempo) {
+        if (player != null) {
+            player.setOptions(Float.toString(tempo));
+        }
+
+        options = Float.toString(tempo);
+    }
 }

src/main/java/org/dstadler/audio/example/ExamplePlayer.java

@@ -19,6 +19,10 @@
 public class ExamplePlayer {
     private final static Logger log = LoggerFactory.make();
 
+    // test-options, set to true to enable some features below
+    private final static boolean SEEK = false;
+    private final static boolean TEMPO_ADJUST = false;
+
     private static volatile boolean shouldStop = false;
 
     @SuppressForbidden(reason = "Uses System.exit()")
@@ -47,7 +51,8 @@ private static void run(String url) throws IOException, InterruptedException {
         Thread writer = new Thread(audioWriter, "Writer thread");
         writer.start();
 
-        //int seeked = -1;
+        int seeked = -1;
+        int count = 0;
 
         // then read and populate the buffer until we have read everything
         while (!buffer.empty() && !shouldStop) {
@@ -62,13 +67,23 @@ private static void run(String url) throws IOException, InterruptedException {
 
                 Thread.sleep(1000);
 
-                /* just for testing seeking
-                if (seeked == -1) {
+                // just for testing seeking
+                if (SEEK && seeked == -1) {
                     seeked = seek(buffer, audioWriter, 0.95);
-                }*/
+                }
+
+                // for testing adjust tempo on the fly
+                if (TEMPO_ADJUST && count % 5 == 0) {
+                    // for testing use tempo between 0.6 and 1.5
+                    float tempo = 0.6f + ((count % 4) * 0.3f);
+                    log.info("Adjusting tempo to " + tempo);
+                    audioWriter.setTempo(tempo);
+                }
             } catch (/*IOException |*/ InterruptedException e) {
                 log.log(Level.WARNING, "Caught unexpected exception", e);
             }
+
+            count++;
         }
 
         // indicate that no more data is read and thus playing should stop

src/main/java/org/dstadler/audio/example/PlayerThread.java

@@ -27,6 +27,7 @@ public class PlayerThread implements Runnable {
     private final Runnable stopper;
     private volatile boolean restart = true;
     private AudioPlayer player;
+    private String options = "";
 
     public PlayerThread(PipedInputStream in, Runnable stopper) {
         // some Audio classes try to use mark()/reset(), thus we use a wrapping BufferedInputStream()
@@ -43,6 +44,7 @@ public void run() {
                 restart = false;
 
                 player = createPlayer(inputStream);
+                player.setOptions(options);
 
                 //player.setOptions("");
 
@@ -73,4 +75,23 @@ private AudioPlayer createPlayer(InputStream inputStream) {
 //            return new AudioSPIPlayer(inputStream);
 //            return new JLayerPlayer(inputStream);
     }
+
+    /**
+     * Allow to set custom options for the current
+     * implementation of the audio player.
+     *
+     * If the player is already running, the
+     * changed options are passed to the
+     * current instance.
+     *
+     * @param options The options to set, possible values
+     *                depend on the used player implementation
+     */
+    public void setOptions(String options) {
+        if (player != null) {
+            player.setOptions(options);
+        }
+
+        this.options = options;
+    }
 }

src/main/java/org/dstadler/audio/player/AudioPlayer.java

@@ -8,12 +8,26 @@
  * of audio playback functionality.
  *
  * The implementations will usually receive a link to the
- * audio-data as part construction, the methods in this
+ * audio-data during construction, the methods in this
  * interface are just used to start and stop playing
- * via play() and close()
+ * via play() and close().
+ *
+ * Some implementations may support setting options,
+ * both initially and at runtime to adjust audio playback
  */
 public interface AudioPlayer extends AutoCloseable {
-
+    /**
+     * Allows to set options which are usually
+     * specific for the current implementation.
+     *
+     * Some implementations also allow to adjust
+     * options at runtime by calling this method
+     * with changed options while the player keeps
+     * playing audio.
+     *
+     * @param options A string with options specific
+     *                for the current implementation
+     */
     void setOptions(String options);
 
     /**

src/main/java/org/dstadler/audio/player/TarsosDSPPlayer.java

@@ -26,6 +26,9 @@ public class TarsosDSPPlayer implements AudioPlayer {
     private AudioDispatcher dispatcher;
     private float tempo = 1.0f;
 
+    private WaveformSimilarityBasedOverlapAdd wsola;
+    private float sampleRate;
+
     public TarsosDSPPlayer(InputStream stream) {
         this.stream = stream;
     }
@@ -37,6 +40,12 @@ public void setOptions(String options) {
             Preconditions.checkState(tempo > 0,
                     "Cannot play at speed zero or less, but had: %s",
                     tempo);
+
+            // if already playing, pass on the new parameters to allow to change tempo at runtime
+            if (wsola != null) {
+                wsola.setDispatcher(dispatcher);
+                wsola.setParameters(WaveformSimilarityBasedOverlapAdd.Parameters.musicDefaults(tempo, sampleRate));
+            }
         }
     }
 
@@ -52,25 +61,22 @@ public void play() throws IOException, UnsupportedAudioFileException {
             // transform the stream to mono as TarsosDSP can only process Mono currently
             AudioInputStream monoStream = AudioUtils.convertToMono(ain);
 
-            // if we should speed up or slow down audio playback, add the WSOLA time stretcher
-            if(tempo != 1.0f) {
-                AudioFormat monoFormat = monoStream.getFormat();
+            TarsosDSPAudioInputStream audioStream = new JVMAudioInputStream(monoStream);
 
-                // then define the time stretching step
-                WaveformSimilarityBasedOverlapAdd wsola = new WaveformSimilarityBasedOverlapAdd(
-                        WaveformSimilarityBasedOverlapAdd.Parameters.musicDefaults(tempo, monoFormat.getSampleRate()));
+            // in order to be able to speed up or slow down audio playback, add the WSOLA time stretcher
+            AudioFormat monoFormat = monoStream.getFormat();
 
-                // then start up the TarsosDSP audio system
-                TarsosDSPAudioInputStream audioStream = new JVMAudioInputStream(monoStream);
-                dispatcher = new AudioDispatcher(audioStream,
-                        wsola.getInputBufferSize() * monoFormat.getChannels(),
-                        wsola.getOverlap() * monoFormat.getChannels());
+            // then define the time stretching step
+            sampleRate = monoFormat.getSampleRate();
+            wsola = new WaveformSimilarityBasedOverlapAdd(
+                    WaveformSimilarityBasedOverlapAdd.Parameters.musicDefaults(tempo, sampleRate));
 
-                dispatcher.addAudioProcessor(wsola);
-            } else {
-                TarsosDSPAudioInputStream audioStream = new JVMAudioInputStream(monoStream);
-                dispatcher = new AudioDispatcher(audioStream, 1024, 512);
-            }
+            // then start up the TarsosDSP audio system
+            dispatcher = new AudioDispatcher(audioStream,
+                    wsola.getInputBufferSize() * monoFormat.getChannels(),
+                    wsola.getOverlap() * monoFormat.getChannels());
+
+            dispatcher.addAudioProcessor(wsola);
 
             //  the audio-output processor provides the actual audio playback in the pipeline
             dispatcher.addAudioProcessor(new be.tarsos.dsp.io.jvm.AudioPlayer(dispatcher.getFormat()));
@@ -98,5 +104,7 @@ public void close() throws IOException {
         if(stream != null) {
             stream.close();
         }
+
+        wsola = null;
     }
 }