Fix `SonicAudioProcessor` end of stream behavior

The `AudioProcessor` interface requires that no more input is queued after
queueing end of stream, but `DefaultAudioSink` did queue more input and the
implementation of `SonicAudioProcessor` actually relied on this to drain output
at the end of the stream.

Fix this behavior by getting `Sonic` output in `getOutput` and having
`DefaultAudioSink` only queue input to processors that are not draining.

Also add TODOs to clean up audio processor implementations where the code
handles interaction that doesn't conform to the interface.

PiperOrigin-RevId: 345406478

extensions/gvr/src/main/java/com/google/android/exoplayer2/ext/gvr/GvrAudioProcessor.java

@@ -135,6 +135,7 @@ public class GvrAudioProcessor implements AudioProcessor {
 
   @Override
   public void queueEndOfStream() {
+    // TODO(internal b/174554082): assert gvrAudioSurround is non-null here and in getOutput.
     if (gvrAudioSurround != null) {
       gvrAudioSurround.triggerProcessing();
     }

library/core/src/main/java/com/google/android/exoplayer2/audio/DefaultAudioSink.java

@@ -885,7 +885,9 @@ public final class DefaultAudioSink implements AudioSink {
         writeBuffer(input, avSyncPresentationTimeUs);
       } else {
         AudioProcessor audioProcessor = activeAudioProcessors[index];
+        if (index > drainingAudioProcessorIndex) {
           audioProcessor.queueInput(input);
+        }
         ByteBuffer output = audioProcessor.getOutput();
         outputBuffers[index] = output;
         if (output.hasRemaining()) {

library/core/src/main/java/com/google/android/exoplayer2/audio/SonicAudioProcessor.java

@@ -165,14 +165,30 @@ public final class SonicAudioProcessor implements AudioProcessor {
 
   @Override
   public void queueInput(ByteBuffer inputBuffer) {
+    if (!inputBuffer.hasRemaining()) {
+      return;
+    }
     Sonic sonic = checkNotNull(this.sonic);
-    if (inputBuffer.hasRemaining()) {
     ShortBuffer shortBuffer = inputBuffer.asShortBuffer();
     int inputSize = inputBuffer.remaining();
     inputBytes += inputSize;
     sonic.queueInput(shortBuffer);
     inputBuffer.position(inputBuffer.position() + inputSize);
   }
+
+  @Override
+  public void queueEndOfStream() {
+    // TODO(internal b/174554082): assert sonic is non-null here and in getOutput.
+    if (sonic != null) {
+      sonic.queueEndOfStream();
+    }
+    inputEnded = true;
+  }
+
+  @Override
+  public ByteBuffer getOutput() {
+    @Nullable Sonic sonic = this.sonic;
+    if (sonic != null) {
       int outputSize = sonic.getOutputSize();
       if (outputSize > 0) {
         if (buffer.capacity() < outputSize) {
@@ -188,17 +204,6 @@ public final class SonicAudioProcessor implements AudioProcessor {
         outputBuffer = buffer;
       }
     }
-
-  @Override
-  public void queueEndOfStream() {
-    if (sonic != null) {
-      sonic.queueEndOfStream();
-    }
-    inputEnded = true;
-  }
-
-  @Override
-  public ByteBuffer getOutput() {
     ByteBuffer outputBuffer = this.outputBuffer;
     this.outputBuffer = EMPTY_BUFFER;
     return outputBuffer;