Switch from AudioFormat.ENCODING_DEFAULT to .ENCODING_PCM_16BIT.

AudioTrack.getMinBufferSize does not handle ENCODING_DEFAULT so
switch back to ENCODING_PCM_16BIT.

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

@@ -299,7 +299,7 @@ public class DashRendererBuilder implements RendererBuilder,
       boolean useAc3Passthrough = haveAc3Tracks && audioCapabilities != null
           && (audioCapabilities.supportsAc3() || audioCapabilities.supportsEAc3());
       audioRenderer = new MediaCodecAudioTrackRenderer(audioSampleSource, drmSessionManager, true,
-          mainHandler, player, useAc3Passthrough ? C.ENCODING_AC3 : AudioFormat.ENCODING_DEFAULT);
+          mainHandler, player, useAc3Passthrough ? C.ENCODING_AC3 : AudioFormat.ENCODING_PCM_16BIT);
     }
 
     // Build the text chunk sources.

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

@@ -125,7 +125,7 @@ public class MediaCodecAudioTrackRenderer extends MediaCodecTrackRenderer {
   public MediaCodecAudioTrackRenderer(SampleSource source, DrmSessionManager drmSessionManager,
       boolean playClearSamplesWithoutKeys, Handler eventHandler, EventListener eventListener) {
     this(source, drmSessionManager, playClearSamplesWithoutKeys, eventHandler, eventListener,
-        AudioFormat.ENCODING_DEFAULT);
+        AudioFormat.ENCODING_PCM_16BIT);
   }
 
   /**

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

@@ -313,10 +313,10 @@ public final class AudioTrack {
 
   /**
    * Reconfigures the audio track to play back media in {@code format}. The encoding is assumed to
-   * be {@link AudioFormat#ENCODING_DEFAULT}.
+   * be {@link AudioFormat#ENCODING_PCM_16BIT}.
    */
   public void reconfigure(MediaFormat format) {
-    reconfigure(format, AudioFormat.ENCODING_DEFAULT, 0);
+    reconfigure(format, AudioFormat.ENCODING_PCM_16BIT, 0);
   }
 
   /**