Fix AC3Passthrough

- Handle read returning NOTHING_READ for AC-3 streams.
- Remove extra checks for the audio track being initialized.
- Call isInitialized() instead of checking audioTrack != null.

library/src/main/java/com/google/android/exoplayer/Ac3PassthroughAudioTrackRenderer.java

@@ -199,11 +199,9 @@ public final class Ac3PassthroughAudioTrackRenderer extends TrackRenderer {
 
       int result =
           source.readData(trackIndex, currentPositionUs, formatHolder, sampleHolder, false);
-      sampleHolder.data.flip();
-      shouldReadInputBuffer = false;
-
       if (result == SampleSource.FORMAT_READ) {
         format = formatHolder.format;
+        audioTrack.reconfigure(format.getFrameworkMediaFormatV16(), AudioFormat.ENCODING_AC3, 0);
       }
       if (result == SampleSource.END_OF_STREAM) {
         inputStreamEnded = true;
@@ -211,6 +209,7 @@ public final class Ac3PassthroughAudioTrackRenderer extends TrackRenderer {
       if (result != SampleSource.SAMPLE_READ) {
         return;
       }
+      shouldReadInputBuffer = false;
     }
 
     int handleBufferResult =
@@ -227,16 +226,12 @@ public final class Ac3PassthroughAudioTrackRenderer extends TrackRenderer {
 
   @Override
   protected void onStarted() {
-    if (audioTrack.isInitialized()) {
-      audioTrack.play();
-    }
+    audioTrack.play();
   }
 
   @Override
   protected void onStopped() {
-    if (audioTrack.isInitialized()) {
-      audioTrack.pause();
-    }
+    audioTrack.pause();
   }
 
   @Override

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

@@ -310,8 +310,8 @@ public final class AudioTrack {
 
     // TODO: Does channelConfig determine channelCount?
     boolean isAc3 = encoding == AudioFormat.ENCODING_AC3 || encoding == AudioFormat.ENCODING_E_AC3;
-    if (audioTrack != null && this.sampleRate == sampleRate
-        && this.channelConfig == channelConfig && !this.isAc3 && !isAc3) {
+    if (isInitialized() && this.sampleRate == sampleRate && this.channelConfig == channelConfig
+        && !this.isAc3 && !isAc3) {
       // We already have an existing audio track with the correct sample rate and channel config.
       return;
     }
@@ -450,7 +450,7 @@ public final class AudioTrack {
 
   /** Returns whether the audio track has more data pending that will be played back. */
   public boolean hasPendingData() {
-    return audioTrack != null && bytesToFrames(submittedBytes) > getPlaybackPositionFrames();
+    return isInitialized() && bytesToFrames(submittedBytes) > getPlaybackPositionFrames();
   }
 
   /** Returns whether enough data has been supplied via {@link #handleBuffer} to begin playback. */
@@ -461,7 +461,7 @@ public final class AudioTrack {
   /** Sets the playback volume. */
   public void setVolume(float volume) {
     this.volume = volume;
-    if (audioTrack != null) {
+    if (isInitialized()) {
       if (Util.SDK_INT >= 21) {
         setVolumeV21(audioTrack, volume);
       } else {
@@ -482,7 +482,7 @@ public final class AudioTrack {
 
   /** Pauses playback. */
   public void pause() {
-    if (audioTrack != null) {
+    if (isInitialized()) {
       resetSyncParams();
       audioTrack.pause();
     }
@@ -494,7 +494,7 @@ public final class AudioTrack {
    * after resetting.
    */
   public void reset() {
-    if (audioTrack != null) {
+    if (isInitialized()) {
       submittedBytes = 0;
       temporaryBufferSize = 0;
       lastRawPlaybackHeadPosition = 0;