Make repetitive decode/draw.

tl;dr:
In the previous transformer, the transcoding flow is

- If a the GL's input surface (from decoder) does not have data, wait 10ms
 (DO_SOME_WORK)
- Else, make the decoder render **ONE** frame to the GL's input surface
  - Wait at least 10ms, until the frame's texture is available
  - Then process the texture

The process is quite slow, so in the new version, we do:
- If a the GL's input surface (from decoder) does not have data, wait 10ms
 (DO_SOME_WORK) **same**
- Else, make the decoder render **as many frames** to the GL's input surface
  - Process **as many** available textures in this DO_SOME_WORK cycle

PiperOrigin-RevId: 415474722

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/FrameEditor.java

@@ -32,6 +32,7 @@ import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.util.GlUtil;
 import java.io.IOException;
+import java.util.concurrent.atomic.AtomicInteger;
 
 /** FrameEditor applies changes to individual video frames. */
 /* package */ final class FrameEditor {
@@ -178,6 +179,7 @@ import java.io.IOException;
   private final EGLContext eglContext;
   private final EGLSurface eglSurface;
   private final int textureId;
+  private final AtomicInteger pendingInputFrameCount;
   private final SurfaceTexture inputSurfaceTexture;
   private final Surface inputSurface;
   private final GlUtil.Program glProgram;
@@ -187,8 +189,6 @@ import java.io.IOException;
   private final int debugPreviewWidth;
   private final int debugPreviewHeight;
 
-  private volatile boolean hasInputData;
-
   private FrameEditor(
       EGLDisplay eglDisplay,
       EGLContext eglContext,
@@ -205,6 +205,7 @@ import java.io.IOException;
     this.eglSurface = eglSurface;
     this.textureId = textureId;
     this.glProgram = glProgram;
+    this.pendingInputFrameCount = new AtomicInteger();
     this.outputWidth = outputWidth;
     this.outputHeight = outputHeight;
     this.debugPreviewEglSurface = debugPreviewEglSurface;
@@ -212,7 +213,8 @@ import java.io.IOException;
     this.debugPreviewHeight = debugPreviewHeight;
     textureTransformMatrix = new float[16];
     inputSurfaceTexture = new SurfaceTexture(textureId);
-    inputSurfaceTexture.setOnFrameAvailableListener(surfaceTexture -> hasInputData = true);
+    inputSurfaceTexture.setOnFrameAvailableListener(
+        surfaceTexture -> pendingInputFrameCount.incrementAndGet());
     inputSurface = new Surface(inputSurfaceTexture);
   }
 
@@ -226,7 +228,7 @@ import java.io.IOException;
    * #processData()}.
    */
   public boolean hasInputData() {
-    return hasInputData;
+    return pendingInputFrameCount.get() > 0;
   }
 
   /** Processes pending input frame. */
@@ -240,13 +242,12 @@ import java.io.IOException;
     long surfaceTextureTimestampNs = inputSurfaceTexture.getTimestamp();
     EGLExt.eglPresentationTimeANDROID(eglDisplay, eglSurface, surfaceTextureTimestampNs);
     EGL14.eglSwapBuffers(eglDisplay, eglSurface);
+    pendingInputFrameCount.decrementAndGet();
 
     if (debugPreviewEglSurface != null) {
       focusAndDrawQuad(debugPreviewEglSurface, debugPreviewWidth, debugPreviewHeight);
       EGL14.eglSwapBuffers(eglDisplay, debugPreviewEglSurface);
     }
-
-    hasInputData = false;
   }
 
   /** Releases all resources. */

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/MediaCodecAdapterWrapper.java

@@ -19,6 +19,7 @@ package com.google.android.exoplayer2.transformer;
 import static com.google.android.exoplayer2.util.Assertions.checkArgument;
 import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
 import static com.google.android.exoplayer2.util.Assertions.checkState;
+import static com.google.android.exoplayer2.util.Util.SDK_INT;
 
 import android.annotation.SuppressLint;
 import android.media.MediaCodec;
@@ -147,6 +148,13 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
       MediaFormatUtil.maybeSetInteger(
           mediaFormat, MediaFormat.KEY_MAX_INPUT_SIZE, format.maxInputSize);
       MediaFormatUtil.setCsdBuffers(mediaFormat, format.initializationData);
+
+      if (SDK_INT >= 29) {
+        // On API levels over 29, Transformer decodes as many frames as possible in one render
+        // cycle. This key ensures no frame dropping when the decoder's output surface is full.
+        mediaFormat.setInteger(MediaFormat.KEY_ALLOW_FRAME_DROP, 0);
+      }
+
       adapter =
           new Factory()
               .createAdapter(

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/VideoSamplePipeline.java

@@ -17,10 +17,13 @@
 package com.google.android.exoplayer2.transformer;
 
 import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
+import static com.google.android.exoplayer2.util.Util.SDK_INT;
 
 import android.content.Context;
 import android.media.MediaCodec;
+import android.media.MediaFormat;
 import androidx.annotation.Nullable;
+import androidx.annotation.RequiresApi;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ExoPlaybackException;
 import com.google.android.exoplayer2.Format;
@@ -145,6 +148,52 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
       return false;
     }
 
+    if (SDK_INT >= 29) {
+      return processDataV29();
+    } else {
+      return processDataDefault();
+    }
+  }
+
+  /**
+   * Processes input data from API 29.
+   *
+   * <p>In this method the decoder could decode multiple frames in one invocation; as compared to
+   * {@link #processDataDefault()}, in which one frame is decoded in each invocation. Consequently,
+   * if {@link FrameEditor} processes frames slower than the decoder, decoded frames are queued up
+   * in the decoder's output surface.
+   *
+   * <p>Prior to API 29, decoders may drop frames to keep their output surface from growing out of
+   * bound; while after API 29, the {@link MediaFormat#KEY_ALLOW_FRAME_DROP} key prevents frame
+   * dropping even when the surface is full. As dropping random frames is not acceptable in {@code
+   * Transformer}, using this method requires API level 29 or higher.
+   */
+  @RequiresApi(29)
+  private boolean processDataV29() {
+    if (frameEditor != null) {
+      while (frameEditor.hasInputData()) {
+        // Processes as much frames in one invocation: FrameEditor's output surface will block
+        // FrameEditor when it's full. There will be no frame drop, or FrameEditor's output surface
+        // growing out of bound.
+        frameEditor.processData();
+      }
+    }
+
+    while (decoder.getOutputBufferInfo() != null) {
+      decoder.releaseOutputBuffer(/* render= */ true);
+    }
+
+    if (decoder.isEnded()) {
+      // TODO(internal b/208986865): Handle possible last frame drop.
+      encoder.signalEndOfInputStream();
+      return false;
+    }
+
+    return frameEditor != null && frameEditor.hasInputData();
+  }
+
+  /** Processes input data. */
+  private boolean processDataDefault() {
     if (frameEditor != null) {
       if (frameEditor.hasInputData()) {
         waitingForFrameEditorInput = false;