Optimize some CodecCounter inefficiency.

1. Use ints rather than longs.
2. Remove some counters that dont seem hugely useful.
3. Replace use of volatile with explicit method calls that
   cause a memory barrier. This is a lot more efficient than
   using volatile because it can be invoked only once per
   doSomeWork.

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

@@ -17,54 +17,41 @@ package com.google.android.exoplayer;
 
 /**
  * Maintains codec event counts, for debugging purposes only.
+ * <p>
+ * Counters should be written from the playback thread only. Counters may be read from any thread.
+ * To ensure that the counter values are correctly reflected between threads, users of this class
+ * should invoke {@link #ensureUpdated()} prior to reading and after writing.
  */
 public final class CodecCounters {
 
-  public volatile long codecInitCount;
-  public volatile long codecReleaseCount;
-  public volatile long outputFormatChangedCount;
-  public volatile long outputBuffersChangedCount;
-  public volatile long queuedInputBufferCount;
-  public volatile long inputBufferWaitingForSampleCount;
-  public volatile long keyframeCount;
-  public volatile long queuedEndOfStreamCount;
-  public volatile long renderedOutputBufferCount;
-  public volatile long skippedOutputBufferCount;
-  public volatile long droppedOutputBufferCount;
-  public volatile long discardedSamplesCount;
+  public int codecInitCount;
+  public int codecReleaseCount;
+  public int outputFormatChangedCount;
+  public int outputBuffersChangedCount;
+  public int renderedOutputBufferCount;
+  public int skippedOutputBufferCount;
+  public int droppedOutputBufferCount;
 
   /**
-   * Resets all counts to zero.
+   * Should be invoked from the playback thread after the counters have been updated. Should also
+   * be invoked from any other thread that wishes to read the counters, before reading. These calls
+   * ensure that counter updates are made visible to the reading threads.
    */
-  public void zeroAllCounts() {
-    codecInitCount = 0;
-    codecReleaseCount = 0;
-    outputFormatChangedCount = 0;
-    outputBuffersChangedCount = 0;
-    queuedInputBufferCount = 0;
-    inputBufferWaitingForSampleCount = 0;
-    keyframeCount = 0;
-    queuedEndOfStreamCount = 0;
-    renderedOutputBufferCount = 0;
-    skippedOutputBufferCount = 0;
-    droppedOutputBufferCount = 0;
-    discardedSamplesCount = 0;
+  public synchronized void ensureUpdated() {
+    // Do nothing. The use of synchronized ensures a memory barrier should another thread also
+    // call this method.
   }
 
   public String getDebugString() {
+    ensureUpdated();
     StringBuilder builder = new StringBuilder();
     builder.append("cic(").append(codecInitCount).append(")");
     builder.append("crc(").append(codecReleaseCount).append(")");
     builder.append("ofc(").append(outputFormatChangedCount).append(")");
     builder.append("obc(").append(outputBuffersChangedCount).append(")");
-    builder.append("qib(").append(queuedInputBufferCount).append(")");
-    builder.append("wib(").append(inputBufferWaitingForSampleCount).append(")");
-    builder.append("kfc(").append(keyframeCount).append(")");
-    builder.append("qes(").append(queuedEndOfStreamCount).append(")");
     builder.append("ren(").append(renderedOutputBufferCount).append(")");
     builder.append("sob(").append(skippedOutputBufferCount).append(")");
     builder.append("dob(").append(droppedOutputBufferCount).append(")");
-    builder.append("dsc(").append(discardedSamplesCount).append(")");
     return builder.toString();
   }
 

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

@@ -60,7 +60,7 @@ import java.util.List;
   private static final int IDLE_INTERVAL_MS = 1000;
 
   private final Handler handler;
-  private final HandlerThread internalPlayerThread;
+  private final HandlerThread internalPlaybackThread;
   private final Handler eventHandler;
   private final MediaClock mediaClock;
   private final boolean[] rendererEnabledFlags;
@@ -100,7 +100,7 @@ import java.util.List;
 
     mediaClock = new MediaClock();
     enabledRenderers = new ArrayList<TrackRenderer>(rendererEnabledFlags.length);
-    internalPlayerThread = new HandlerThread(getClass().getSimpleName() + ":Handler") {
+    internalPlaybackThread = new HandlerThread(getClass().getSimpleName() + ":Handler") {
       @Override
       public void run() {
         // Note: The documentation for Process.THREAD_PRIORITY_AUDIO that states "Applications can
@@ -109,12 +109,12 @@ import java.util.List;
         super.run();
       }
     };
-    internalPlayerThread.start();
-    handler = new Handler(internalPlayerThread.getLooper(), this);
+    internalPlaybackThread.start();
+    handler = new Handler(internalPlaybackThread.getLooper(), this);
   }
 
   public Looper getPlaybackLooper() {
-    return internalPlayerThread.getLooper();
+    return internalPlaybackThread.getLooper();
   }
 
   public int getCurrentPosition() {
@@ -179,7 +179,7 @@ import java.util.List;
           Thread.currentThread().interrupt();
         }
       }
-      internalPlayerThread.quit();
+      internalPlaybackThread.quit();
     }
   }
 

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

@@ -382,6 +382,7 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
           while (feedInputBuffer()) {}
         }
       }
+      codecCounters.ensureUpdated();
     } catch (IOException e) {
       throw new ExoPlaybackException(e);
     }
@@ -403,7 +404,6 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
         if (!sampleHolder.decodeOnly) {
           currentPositionUs = sampleHolder.timeUs;
         }
-        codecCounters.discardedSamplesCount++;
       } else if (result == SampleSource.FORMAT_READ) {
         onInputFormatChanged(formatHolder);
       }
@@ -476,7 +476,6 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
     }
 
     if (result == SampleSource.NOTHING_READ) {
-      codecCounters.inputBufferWaitingForSampleCount++;
       return false;
     }
     if (result == SampleSource.DISCONTINUITY_READ) {
@@ -505,7 +504,6 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
       try {
         codec.queueInputBuffer(inputIndex, 0, 0, 0, MediaCodec.BUFFER_FLAG_END_OF_STREAM);
         inputIndex = -1;
-        codecCounters.queuedEndOfStreamCount++;
       } catch (CryptoException e) {
         notifyCryptoError(e);
         throw new ExoPlaybackException(e);
@@ -545,10 +543,6 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
       } else {
         codec.queueInputBuffer(inputIndex, 0 , bufferSize, presentationTimeUs, 0);
       }
-      codecCounters.queuedInputBufferCount++;
-      if ((sampleHolder.flags & MediaExtractor.SAMPLE_FLAG_SYNC) != 0) {
-        codecCounters.keyframeCount++;
-      }
       inputIndex = -1;
       codecReconfigurationState = RECONFIGURATION_STATE_NONE;
     } catch (CryptoException e) {