Use CodecCounters consistently in all renderers.

- Increment skippedBufferCount for VPX and ADTR.
- Set maxConsecutiveDroppedOutputBufferCount count for VPX.
  Tweak its meaning to ignore skipped frames.
- Remove outputFormat/outputBuffer changed counts. These add
  limited value. Also, MediaCodec is moving toward a model where
  you don't see the output buffers changing because you dequeue
  them one at a time (like how our extension decoders work).
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=122258530

extensions/vp9/src/main/java/com/google/android/exoplayer/ext/vp9/LibvpxVideoTrackRenderer.java

@@ -79,8 +79,9 @@ public final class LibvpxVideoTrackRenderer extends TrackRenderer {
   private int previousWidth;
   private int previousHeight;
 
-  private int droppedFrameCount;
   private long droppedFrameAccumulationStartTimeMs;
+  private int droppedFrameCount;
+  private int consecutiveDroppedFrameCount;
 
   /**
    * @param scaleToFit Boolean that indicates if video frames should be scaled to fit when
@@ -183,6 +184,7 @@ public final class LibvpxVideoTrackRenderer extends TrackRenderer {
       if (outputBuffer == null) {
         return false;
       }
+      codecCounters.skippedOutputBufferCount += outputBuffer.skippedOutputBufferCount;
     }
 
     if (nextOutputBuffer == null) {
@@ -202,6 +204,9 @@ public final class LibvpxVideoTrackRenderer extends TrackRenderer {
       // Drop frame if we are too late.
       codecCounters.droppedOutputBufferCount++;
       droppedFrameCount++;
+      consecutiveDroppedFrameCount++;
+      codecCounters.maxConsecutiveDroppedOutputBufferCount = Math.max(consecutiveDroppedFrameCount,
+          codecCounters.maxConsecutiveDroppedOutputBufferCount);
       if (droppedFrameCount == maxDroppedFrameCountToNotify) {
         notifyAndResetDroppedFrameCount();
       }
@@ -227,6 +232,7 @@ public final class LibvpxVideoTrackRenderer extends TrackRenderer {
 
   private void renderBuffer() {
     codecCounters.renderedOutputBufferCount++;
+    consecutiveDroppedFrameCount = 0;
     notifyIfVideoSizeChanged(outputBuffer.width, outputBuffer.height);
     if (outputBuffer.mode == VpxDecoder.OUTPUT_MODE_RGB && surface != null) {
       renderRgbFrame(outputBuffer, scaleToFit);
@@ -320,6 +326,7 @@ public final class LibvpxVideoTrackRenderer extends TrackRenderer {
     inputStreamEnded = false;
     outputStreamEnded = false;
     renderedFirstFrame = false;
+    consecutiveDroppedFrameCount = 0;
     if (decoder != null) {
       flushDecoder();
     }

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

@@ -24,14 +24,40 @@ package com.google.android.exoplayer;
  */
 public final class CodecCounters {
 
+  /**
+   * The number of times the codec has been initialized.
+   */
   public int codecInitCount;
+  /**
+   * The number of times the codec has been released.
+   */
   public int codecReleaseCount;
+  /**
+   * The number of queued input buffers.
+   */
   public int inputBufferCount;
-  public int outputFormatChangedCount;
-  public int outputBuffersChangedCount;
+  /**
+   * The number of rendered output buffers.
+   */
   public int renderedOutputBufferCount;
+  /**
+   * The number of skipped output buffers.
+   * <p>
+   * A skipped output buffer is an output buffer that was deliberately not rendered.
+   */
   public int skippedOutputBufferCount;
+  /**
+   * The number of dropped output buffers.
+   * <p>
+   * A dropped output buffer is an output buffer that was supposed to be rendered, but was instead
+   * dropped because it could not be rendered in time.
+   */
   public int droppedOutputBufferCount;
+  /**
+   * The maximum number of dropped output buffers without an interleaving rendered output buffer.
+   * <p>
+   * Skipped output buffers are ignored for the purposes of calculating this value.
+   */
   public int maxConsecutiveDroppedOutputBufferCount;
 
   /**
@@ -46,15 +72,13 @@ public final class CodecCounters {
 
   public String getDebugString() {
     ensureUpdated();
-    return "cic:" + codecInitCount
-        + " crc:" + codecReleaseCount
-        + " ibc:" + inputBufferCount
-        + " ofc:" + outputFormatChangedCount
-        + " obc:" + outputBuffersChangedCount
-        + " ren:" + renderedOutputBufferCount
-        + " sob:" + skippedOutputBufferCount
-        + " dob:" + droppedOutputBufferCount
-        + " mcdob:" + maxConsecutiveDroppedOutputBufferCount;
+    return "ic:" + codecInitCount
+        + " rc:" + codecReleaseCount
+        + " ib:" + inputBufferCount
+        + " rb:" + renderedOutputBufferCount
+        + " sb:" + skippedOutputBufferCount
+        + " db:" + droppedOutputBufferCount
+        + " mcdb:" + maxConsecutiveDroppedOutputBufferCount;
   }
 
 }

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

@@ -827,7 +827,6 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
       format.setInteger(android.media.MediaFormat.KEY_CHANNEL_COUNT, 1);
     }
     onOutputFormatChanged(codec, format);
-    codecCounters.outputFormatChangedCount++;
   }
 
   /**
@@ -836,7 +835,6 @@ public abstract class MediaCodecTrackRenderer extends TrackRenderer {
   @SuppressWarnings("deprecation")
   private void processOutputBuffersChanged() {
     outputBuffers = codec.getOutputBuffers();
-    codecCounters.outputBuffersChangedCount++;
   }
 
   /**

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

@@ -392,7 +392,6 @@ public class MediaCodecVideoTrackRenderer extends MediaCodecTrackRenderer {
       boolean shouldSkip) {
     if (shouldSkip) {
       skipOutputBuffer(codec, bufferIndex);
-      consecutiveDroppedFrameCount = 0;
       return true;
     }
 
@@ -402,7 +401,6 @@ public class MediaCodecVideoTrackRenderer extends MediaCodecTrackRenderer {
       } else {
         renderOutputBuffer(codec, bufferIndex);
       }
-      consecutiveDroppedFrameCount = 0;
       return true;
     }
 
@@ -433,7 +431,6 @@ public class MediaCodecVideoTrackRenderer extends MediaCodecTrackRenderer {
       // Let the underlying framework time the release.
       if (earlyUs < 50000) {
         renderOutputBufferV21(codec, bufferIndex, adjustedReleaseTimeNs);
-        consecutiveDroppedFrameCount = 0;
         return true;
       }
     } else {
@@ -450,7 +447,6 @@ public class MediaCodecVideoTrackRenderer extends MediaCodecTrackRenderer {
           }
         }
         renderOutputBuffer(codec, bufferIndex);
-        consecutiveDroppedFrameCount = 0;
         return true;
       }
     }
@@ -486,6 +482,7 @@ public class MediaCodecVideoTrackRenderer extends MediaCodecTrackRenderer {
     codec.releaseOutputBuffer(bufferIndex, true);
     TraceUtil.endSection();
     codecCounters.renderedOutputBufferCount++;
+    consecutiveDroppedFrameCount = 0;
     renderedFirstFrame = true;
     maybeNotifyDrawnToSurface();
   }
@@ -497,6 +494,7 @@ public class MediaCodecVideoTrackRenderer extends MediaCodecTrackRenderer {
     codec.releaseOutputBuffer(bufferIndex, releaseTimeNs);
     TraceUtil.endSection();
     codecCounters.renderedOutputBufferCount++;
+    consecutiveDroppedFrameCount = 0;
     renderedFirstFrame = true;
     maybeNotifyDrawnToSurface();
   }

library/src/main/java/com/google/android/exoplayer/extensions/AudioDecoderTrackRenderer.java

@@ -164,6 +164,7 @@ public abstract class AudioDecoderTrackRenderer extends TrackRenderer implements
       if (outputBuffer == null) {
         return false;
       }
+      codecCounters.skippedOutputBufferCount += outputBuffer.skippedOutputBufferCount;
     }
 
     if (outputBuffer.isEndOfStream()) {

library/src/main/java/com/google/android/exoplayer/extensions/OutputBuffer.java

@@ -28,6 +28,11 @@ public abstract class OutputBuffer extends Buffer {
   public long timestampUs;
 
   /**
+   * The number of buffers immediately prior to this one that were skipped in the {@link Decoder}.
+   */
+  public int skippedOutputBufferCount;
+
+  /**
    * Releases the output buffer for reuse. Must be called when the buffer is no longer needed.
    */
   public abstract void release();

library/src/main/java/com/google/android/exoplayer/extensions/SimpleDecoder.java

@@ -56,6 +56,7 @@ public abstract class SimpleDecoder<I extends DecoderInputBuffer, O extends Outp
   private E exception;
   private boolean flushed;
   private boolean released;
+  private int skippedOutputBufferCount;
 
   /**
    * @param inputBuffers An array of nulls that will be used to store references to input buffers.
@@ -148,6 +149,7 @@ public abstract class SimpleDecoder<I extends DecoderInputBuffer, O extends Outp
   public final void flush() {
     synchronized (lock) {
       flushed = true;
+      skippedOutputBufferCount = 0;
       if (dequeuedInputBuffer != null) {
         releaseInputBufferInternal(dequeuedInputBuffer);
         dequeuedInputBuffer = null;
@@ -242,12 +244,14 @@ public abstract class SimpleDecoder<I extends DecoderInputBuffer, O extends Outp
     }
 
     synchronized (lock) {
-      if (flushed || outputBuffer.isDecodeOnly()) {
-        // If a flush occurred while decoding or the buffer was only for decoding (not presentation)
-        // then make the output buffer available again rather than queueing it to be consumed.
+      if (flushed) {
+        releaseOutputBufferInternal(outputBuffer);
+      } else if (outputBuffer.isDecodeOnly()) {
+        skippedOutputBufferCount++;
         releaseOutputBufferInternal(outputBuffer);
       } else {
-        // Queue the decoded output buffer to be consumed.
+        outputBuffer.skippedOutputBufferCount = skippedOutputBufferCount;
+        skippedOutputBufferCount = 0;
         queuedOutputBuffers.addLast(outputBuffer);
       }
       // Make the input buffer available again.
@@ -287,8 +291,9 @@ public abstract class SimpleDecoder<I extends DecoderInputBuffer, O extends Outp
    * @param inputBuffer The buffer to decode.
    * @param outputBuffer The output buffer to store decoded data. The flag
    *     {@link C#BUFFER_FLAG_DECODE_ONLY} will be set if the same flag is set on
-   *     {@code inputBuffer}, but the decoder may set/unset the flag if required. If the flag is set
-   *     after this method returns, any output will not be presented.
+   *     {@code inputBuffer}, but may be set/unset as required. If the flag is set when the call
+   *     returns then the output buffer will not be made available to dequeue. The output buffer
+   *     may not have been populated in this case.
    * @param reset True if the decoder must be reset before decoding.
    * @return A decoder exception if an error occurred, or null if decoding was successful.
    */