Don't re-buffer when AudioTrack underruns occur.

demo/src/main/java/com/google/android/exoplayer/demo/EventLogger.java

@@ -159,6 +159,12 @@ public class EventLogger implements DemoPlayer.Listener, DemoPlayer.InfoListener
     printInternalError("audioTrackWriteError", e);
   }
 
+  @Override
+  public void onAudioTrackUnderrun(long audioTrackBufferSizeMs, long elapsedSinceLastFeedMs) {
+    printInternalError("audioTrackUnderrun [" + audioTrackBufferSizeMs + ", "
+        + elapsedSinceLastFeedMs + "]", null);
+  }
+
   @Override
   public void onCryptoError(CryptoException e) {
     printInternalError("cryptoError", e);

demo/src/main/java/com/google/android/exoplayer/demo/player/DemoPlayer.java

@@ -105,6 +105,7 @@ public class DemoPlayer implements ExoPlayer.Listener, ChunkSampleSource.EventLi
     void onRendererInitializationError(Exception e);
     void onAudioTrackInitializationError(AudioTrack.InitializationException e);
     void onAudioTrackWriteError(AudioTrack.WriteException e);
+    void onAudioTrackUnderrun(long audioTrackBufferSizeMs, long elapsedSinceLastFeedMs);
     void onDecoderInitializationError(DecoderInitializationException e);
     void onCryptoError(CryptoException e);
     void onLoadError(int sourceId, IOException e);
@@ -481,6 +482,13 @@ public class DemoPlayer implements ExoPlayer.Listener, ChunkSampleSource.EventLi
     }
   }
 
+  @Override
+  public void onAudioTrackUnderrun(long audioTrackBufferSizeMs, long elapsedSinceLastFeedMs) {
+    if (internalErrorListener != null) {
+      internalErrorListener.onAudioTrackUnderrun(audioTrackBufferSizeMs, elapsedSinceLastFeedMs);
+    }
+  }
+
   @Override
   public void onCryptoError(CryptoException e) {
     if (internalErrorListener != null) {

library/src/main/java/com/google/android/exoplayer/MediaCodecAudioTrackRenderer.java

@@ -26,6 +26,7 @@ import android.media.AudioManager;
 import android.media.MediaCodec;
 import android.media.audiofx.Virtualizer;
 import android.os.Handler;
+import android.os.SystemClock;
 
 import java.nio.ByteBuffer;
 
@@ -55,6 +56,14 @@ public class MediaCodecAudioTrackRenderer extends MediaCodecTrackRenderer implem
      */
     void onAudioTrackWriteError(AudioTrack.WriteException e);
 
+    /**
+     * Invoked when an {@link AudioTrack} underrun occurs.
+     *
+     * @param audioTrackBufferSizeMs The size of the {@link AudioTrack}'s buffer, in milliseconds.
+     * @param elapsedSinceLastFeedMs The time since the {@link AudioTrack} was last fed data.
+     */
+    void onAudioTrackUnderrun(long audioTrackBufferSizeMs, long elapsedSinceLastFeedMs);
+
   }
 
   /**
@@ -77,6 +86,9 @@ public class MediaCodecAudioTrackRenderer extends MediaCodecTrackRenderer implem
   private long currentPositionUs;
   private boolean allowPositionDiscontinuity;
 
+  private boolean audioTrackHasData;
+  private long lastFeedElapsedRealtimeMs;
+
   /**
    * @param source The upstream source from which the renderer obtains samples.
    */
@@ -272,8 +284,7 @@ public class MediaCodecAudioTrackRenderer extends MediaCodecTrackRenderer implem
 
   @Override
   protected boolean isReady() {
-    return audioTrack.hasPendingData()
-        || (super.isReady() && getSourceState() == SOURCE_STATE_READY_READ_MAY_FAIL);
+    return audioTrack.hasPendingData() || super.isReady();
   }
 
   @Override
@@ -321,8 +332,8 @@ public class MediaCodecAudioTrackRenderer extends MediaCodecTrackRenderer implem
       return true;
     }
 
-    // Initialize and start the audio track now.
     if (!audioTrack.isInitialized()) {
+      // Initialize the AudioTrack now.
       try {
         if (audioSessionId != AudioTrack.SESSION_ID_NOT_SET) {
           audioTrack.initialize(audioSessionId);
@@ -330,20 +341,29 @@ public class MediaCodecAudioTrackRenderer extends MediaCodecTrackRenderer implem
           audioSessionId = audioTrack.initialize();
           onAudioSessionId(audioSessionId);
         }
+        audioTrackHasData = false;
       } catch (AudioTrack.InitializationException e) {
         notifyAudioTrackInitializationError(e);
         throw new ExoPlaybackException(e);
       }
-
       if (getState() == TrackRenderer.STATE_STARTED) {
         audioTrack.play();
       }
+    } else {
+      // Check for AudioTrack underrun.
+      boolean audioTrackHadData = audioTrackHasData;
+      audioTrackHasData = audioTrack.hasPendingData();
+      if (audioTrackHadData && !audioTrackHasData && getState() == TrackRenderer.STATE_STARTED) {
+        long elapsedSinceLastFeedMs = SystemClock.elapsedRealtime() - lastFeedElapsedRealtimeMs;
+        notifyAudioTrackUnderrun(audioTrack.getBufferSizeUs() / 1000, elapsedSinceLastFeedMs);
+      }
     }
 
     int handleBufferResult;
     try {
       handleBufferResult = audioTrack.handleBuffer(
           buffer, bufferInfo.offset, bufferInfo.size, bufferInfo.presentationTimeUs);
+      lastFeedElapsedRealtimeMs = SystemClock.elapsedRealtime();
     } catch (AudioTrack.WriteException e) {
       notifyAudioTrackWriteError(e);
       throw new ExoPlaybackException(e);
@@ -405,4 +425,16 @@ public class MediaCodecAudioTrackRenderer extends MediaCodecTrackRenderer implem
     }
   }
 
+  private void notifyAudioTrackUnderrun(final long audioTrackBufferSizeMs,
+      final long elapsedSinceLastFeedMs) {
+    if (eventHandler != null && eventListener != null) {
+      eventHandler.post(new Runnable()  {
+        @Override
+        public void run() {
+          eventListener.onAudioTrackUnderrun(audioTrackBufferSizeMs, elapsedSinceLastFeedMs);
+        }
+      });
+    }
+  }
+
 }

library/src/main/java/com/google/android/exoplayer/audio/AudioTrack.java

@@ -181,6 +181,7 @@ public final class AudioTrack {
   private int frameSize;
   private int minBufferSize;
   private int bufferSize;
+  private long bufferSizeUs;
 
   private int nextPlayheadOffsetIndex;
   private int playheadOffsetCount;
@@ -433,9 +434,25 @@ public final class AudioTrack {
           : multipliedBufferSize > maxAppBufferSize ? maxAppBufferSize
           : multipliedBufferSize;
     }
+    bufferSizeUs = framesToDurationUs(bytesToFrames(bufferSize));
   }
 
-  /** Starts/resumes playing audio if the audio track has been initialized. */
+  /**
+   * Returns the size of this {@link AudioTrack}'s buffer in microseconds, given its current
+   * configuration.
+   * <p>
+   * The duration returned from this method may change as a result of calling one of the
+   * {@link #reconfigure} methods.
+   *
+   * @return The size of the buffer in microseconds.
+   */
+  public long getBufferSizeUs() {
+    return bufferSizeUs;
+  }
+
+  /**
+   * Starts or resumes playing audio if the audio track has been initialized.
+   */
   public void play() {
     if (isInitialized()) {
       resumeSystemTimeUs = System.nanoTime() / 1000;
@@ -443,7 +460,9 @@ public final class AudioTrack {
     }
   }
 
-  /** Signals to the audio track that the next buffer is discontinuous with the previous buffer. */
+  /**
+   * Signals to the audio track that the next buffer is discontinuous with the previous buffer.
+   */
   public void handleDiscontinuity() {
     // Force resynchronization after a skipped buffer.
     if (startMediaTimeState == START_IN_SYNC) {
@@ -584,14 +603,18 @@ public final class AudioTrack {
     return audioTrack.write(buffer, size, android.media.AudioTrack.WRITE_NON_BLOCKING);
   }
 
-  /** Returns whether the audio track has more data pending that will be played back. */
+  /**
+   * Returns whether the audio track has more data pending that will be played back.
+   */
   public boolean hasPendingData() {
     return isInitialized()
         && (bytesToFrames(submittedBytes) > audioTrackUtil.getPlaybackHeadPosition()
             || overrideHasPendingData());
   }
 
-  /** Sets the playback volume. */
+  /**
+   * Sets the playback volume.
+   */
   public void setVolume(float volume) {
     if (this.volume != volume) {
       this.volume = volume;
@@ -619,7 +642,9 @@ public final class AudioTrack {
     audioTrack.setStereoVolume(volume, volume);
   }
 
-  /** Pauses playback. */
+  /**
+   * Pauses playback.
+   */
   public void pause() {
     if (isInitialized()) {
       resetSyncParams();
@@ -662,13 +687,17 @@ public final class AudioTrack {
     }
   }
 
-  /** Releases all resources associated with this instance. */
+  /**
+   * Releases all resources associated with this instance.
+   */
   public void release() {
     reset();
     releaseKeepSessionIdAudioTrack();
   }
 
-  /** Releases {@link #keepSessionIdAudioTrack} asynchronously, if it is non-{@code null}. */
+  /**
+   * Releases {@link #keepSessionIdAudioTrack} asynchronously, if it is non-{@code null}.
+   */
   private void releaseKeepSessionIdAudioTrack() {
     if (keepSessionIdAudioTrack == null) {
       return;
@@ -685,7 +714,9 @@ public final class AudioTrack {
     }.start();
   }
 
-  /** Returns whether {@link #getCurrentPositionUs} can return the current playback position. */
+  /**
+   * Returns whether {@link #getCurrentPositionUs} can return the current playback position.
+   */
   private boolean hasCurrentPositionUs() {
     return isInitialized() && startMediaTimeState != START_NOT_SET;
   }
@@ -757,7 +788,7 @@ public final class AudioTrack {
           // Compute the audio track latency, excluding the latency due to the buffer (leaving
           // latency due to the mixer and audio hardware driver).
           latencyUs = (Integer) getLatencyMethod.invoke(audioTrack, (Object[]) null) * 1000L
-              - framesToDurationUs(bytesToFrames(bufferSize));
+              - bufferSizeUs;
           // Sanity check that the latency is non-negative.
           latencyUs = Math.max(latencyUs, 0);
           // Sanity check that the latency isn't too large.

playbacktests/src/main/java/com/google/android/exoplayer/playbacktests/util/LogcatLogger.java

@@ -104,6 +104,12 @@ public final class LogcatLogger implements ExoPlayer.Listener,
     Log.e(tag, "Audio track write error", e);
   }
 
+  @Override
+  public void onAudioTrackUnderrun(long audioTrackBufferSizeMs, long elapsedSinceLastFeedMs) {
+    Log.e(tag, "Audio track underrun (" + audioTrackBufferSizeMs + ", " + elapsedSinceLastFeedMs
+        + ")");
+  }
+
   @Override
   public void onDroppedFrames(int count, long elapsed) {
     Log.w(tag, "Dropped frames (" + count + ")");