Return output immediately if available from AudioProcessingPipeline.

If there is output data available (outputBuffer.hasRemaining()), then
there is no need to move other data between the underlying processors.
It will not change the buffer being returned by that call to getOutput.

If there is no output data readily available, it's necessary to go to
the AudioProcessors and pass buffers between them, as this may produce
data for output.

PiperOrigin-RevId: 490482653

library/common/src/main/java/com/google/android/exoplayer2/audio/AudioProcessingPipeline.java

@@ -210,8 +210,11 @@ public final class AudioProcessingPipeline {
     if (!isOperational()) {
     if (!isOperational()) {
       return EMPTY_BUFFER;
       return EMPTY_BUFFER;
     }
     }
-    processData(EMPTY_BUFFER);
-    return outputBuffers[getFinalOutputBufferIndex()];
+    ByteBuffer outputBuffer = outputBuffers[getFinalOutputBufferIndex()];
+    if (!outputBuffer.hasRemaining()) {
+      processData(EMPTY_BUFFER);
+    }
+    return outputBuffer;
   }
   }
 
 
   /**
   /**