Fix so video renderer correctly reports ready in tunneling mode.

In tunneled playback mode the video renderer is potentially 'ready' with output at anytime there are buffers queued to the codec.   This fix add the more specific boolean `hasOuputReady()` and uses this in the `isReady()` check.

This changes fixes issue #6366

The call to dequeueOutputBuffer() simply returns TRY_AGAIN always in tunneled mode (this comment is correct: #1688 (comment) so the super.hasOutputReady() is always false in tunneling mode, even though the codec may have output ready.

Author: stevemayhew

library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecRenderer.java

@@ -34,6 +34,7 @@
 import com.google.android.exoplayer2.ExoPlaybackException;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.FormatHolder;
+import com.google.android.exoplayer2.Renderer;
 import com.google.android.exoplayer2.decoder.CryptoInfo;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
@@ -1144,6 +1145,19 @@ private boolean hasOutputBuffer() {
     return outputIndex >= 0;
   }
 
+  /**
+   * Check if the renderer has one or more output frames queued to render.  For non-tunneled
+   * mode MediaCodecRenderer's this is true if the codec has returned a frame ready to render
+   * (that is {@see #hasOutputBuffer() is true}.
+   *
+   * This factors into the ready {@link Renderer#isReady()} decision
+   *
+   * @return
+   */
+  protected boolean hasOutputReady() {
+    return hasOutputBuffer();
+  }
+
   private void resetInputBuffer() {
     inputIndex = C.INDEX_UNSET;
     buffer.data = null;
@@ -1528,7 +1542,7 @@ public boolean isReady() {
     return inputFormat != null
         && !waitingForKeys
         && (isSourceReady()
-            || hasOutputBuffer()
+            || hasOutputReady()
             || (codecHotswapDeadlineMs != C.TIME_UNSET
                 && SystemClock.elapsedRealtime() < codecHotswapDeadlineMs));
   }

library/core/src/main/java/com/google/android/exoplayer2/video/MediaCodecVideoRenderer.java

@@ -400,6 +400,18 @@ public boolean isReady() {
     }
   }
 
+  /**
+   * Override, to handle tunneling.  In the tunneled case we must assume there is
+   * output ready to render whenever we have queued any sample buffers to the codec that
+   * it has not reported as rendered.
+   *
+   * @return
+   */
+  @Override
+  protected boolean hasOutputReady() {
+    return tunneling && buffersInCodecCount > 0 || super.hasOutputReady();
+  }
+
   @Override
   protected void onStarted() {
     super.onStarted();