Flush: VideoFrameProcessor texture output

PiperOrigin-RevId: 576928149

libraries/effect/src/main/java/androidx/media3/effect/DefaultVideoFrameProcessor.java

@@ -547,6 +547,16 @@ public final class DefaultVideoFrameProcessor implements VideoFrameProcessor {
     inputSwitcher.signalEndOfInputStream();
   }
 
+  /**
+   * {@inheritDoc}
+   *
+   * <p>The downstream frame consumer must be flushed before this instance is flushed, and stop
+   * accepting input until this DefaultVideoFrameProcessor instance finishes flushing.
+   *
+   * <p>After this method is called, any object consuming {@linkplain
+   * Factory.Builder#setTextureOutput texture output} must not access any output textures that were
+   * {@link GlTextureProducer.Listener#onTextureRendered rendered} before calling this method.
+   */
   @Override
   public void flush() {
     if (!inputSwitcher.hasActiveInput()) {

libraries/effect/src/main/java/androidx/media3/effect/FinalShaderProgramWrapper.java

@@ -155,11 +155,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   @Override
   public void setInputListener(InputListener inputListener) {
     this.inputListener = inputListener;
-    int inputCapacity =
-        textureOutputListener == null
-            ? SURFACE_INPUT_CAPACITY
-            : outputTexturePool.freeTextureCount();
-    for (int i = 0; i < inputCapacity; i++) {
+    for (int i = 0; i < getInputCapacity(); i++) {
       inputListener.onReadyToAcceptInputFrame();
     }
   }
@@ -254,20 +250,35 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
   @Override
   public void flush() {
+    // The downstream consumer must already have been flushed, so the textureOutputListener
+    // implementation does not access its previously output textures, per its contract. However, the
+    // downstream consumer may not have called releaseOutputTexture on all these textures. Release
+    // all output textures that aren't already released.
+    if (textureOutputListener != null) {
+      outputTexturePool.freeAllTextures();
+      outputTextureTimestamps.clear();
+      syncObjects.clear();
+    }
+
     // Drops all frames that aren't rendered yet.
     availableFrames.clear();
     if (defaultShaderProgram != null) {
       defaultShaderProgram.flush();
     }
+
+    // Signal flush upstream.
     inputListener.onFlush();
-    if (textureOutputListener == null) {
-      // TODO: b/293572152 - Add texture output flush() support, propagating the flush() signal to
-      // downstream components so that they can release TexturePool resources and FinalWrapper can
-      // call onReadyToAcceptInputFrame().
+    for (int i = 0; i < getInputCapacity(); i++) {
       inputListener.onReadyToAcceptInputFrame();
     }
   }
 
+  private int getInputCapacity() {
+    return textureOutputListener == null
+        ? SURFACE_INPUT_CAPACITY
+        : outputTexturePool.freeTextureCount();
+  }
+
   @Override
   public synchronized void release() throws VideoFrameProcessingException {
     if (defaultShaderProgram != null) {

libraries/transformer/src/androidTest/java/androidx/media3/transformer/mh/DefaultVideoFrameProcessorMultipleTextureOutputPixelTest.java

@@ -119,6 +119,32 @@ public class DefaultVideoFrameProcessorMultipleTextureOutputPixelTest {
         .isAtMost(MAXIMUM_AVERAGE_PIXEL_ABSOLUTE_DIFFERENCE_DIFFERENT_DEVICE);
   }
 
+  // This tests a condition that is difficult to synchronize, and is subject to a race
+  // condition. It may flake/fail if any queued frames are processed in the VideoFrameProcessor
+  // thread, before flush begins and cancels these pending frames. However, this is better than not
+  // testing this behavior at all, and in practice has succeeded every time on a 1000-time run.
+  // TODO: b/302695659 - Make this test more deterministic.
+  @Test
+  public void textureOutput_queueFiveBitmapsAndFlush_outputsOnlyAfterFlush() throws Exception {
+    String testId = "textureOutput_queueFiveBitmapsAndFlush_outputsOnlyAfterFlush";
+    videoFrameProcessorTestRunner = getFrameProcessorTestRunnerBuilder(testId).build();
+    ImmutableList<Long> inputTimestamps1 = ImmutableList.of(1_000_000L, 2_000_000L, 3_000_000L);
+    ImmutableList<Long> inputTimestamps2 = ImmutableList.of(4_000_000L, 5_000_000L, 6_000_000L);
+
+    queueBitmaps(videoFrameProcessorTestRunner, ORIGINAL_PNG_ASSET_PATH, inputTimestamps1);
+    videoFrameProcessorTestRunner.flush();
+    queueBitmaps(videoFrameProcessorTestRunner, MEDIA3_TEST_PNG_ASSET_PATH, inputTimestamps2);
+    videoFrameProcessorTestRunner.endFrameProcessing();
+
+    TextureBitmapReader textureBitmapReader = checkNotNull(this.textureBitmapReader);
+    Set<Long> actualOutputTimestamps = textureBitmapReader.getOutputTimestamps();
+    assertThat(actualOutputTimestamps).containsAtLeastElementsIn(inputTimestamps2).inOrder();
+    // This assertion is subject to flaking, per test comments. If it flakes, consider increasing
+    // the number of elements in inputTimestamps2.
+    assertThat(actualOutputTimestamps.size())
+        .isLessThan(inputTimestamps1.size() + inputTimestamps2.size());
+  }
+
   private void queueBitmaps(
       VideoFrameProcessorTestRunner videoFrameProcessorTestRunner,
       String bitmapAssetPath,