Separate matrix effect specification and implementation.

This change splits AdvancedFrameProcessor into 4 files:
- MatrixTransformationFrameProcessor for the GlFrameProcessor
  implementation
- MatrixTransformation and GlMatrixTransformation for the GlEffect
  specification
- MatrixUtils for the static matrix helpers

PiperOrigin-RevId: 446236384

demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/AdvancedFrameProcessorFactory.java → demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/MatrixTransformationFactory.java

@@ -17,40 +17,39 @@ package com.google.android.exoplayer2.transformerdemo;
 
 import android.graphics.Matrix;
 import com.google.android.exoplayer2.C;
-import com.google.android.exoplayer2.transformer.AdvancedFrameProcessor;
-import com.google.android.exoplayer2.transformer.GlFrameProcessor;
+import com.google.android.exoplayer2.transformer.GlMatrixTransformation;
+import com.google.android.exoplayer2.transformer.MatrixTransformation;
 import com.google.android.exoplayer2.util.Util;
 
 /**
- * Factory for {@link GlFrameProcessor GlFrameProcessors} that create video effects by applying
- * transformation matrices to the individual video frames using {@link AdvancedFrameProcessor}.
+ * Factory for {@link GlMatrixTransformation GlMatrixTransformations} and {@link
+ * MatrixTransformation MatrixTransformations} that create video effects by applying transformation
+ * matrices to the individual video frames.
  */
-/* package */ final class AdvancedFrameProcessorFactory {
+/* package */ final class MatrixTransformationFactory {
   /**
-   * Returns a {@link GlFrameProcessor} that rescales the frames over the first {@value
+   * Returns a {@link MatrixTransformation} that rescales the frames over the first {@value
    * #ZOOM_DURATION_SECONDS} seconds, such that the rectangle filled with the input frame increases
    * linearly in size from a single point to filling the full output frame.
    */
-  public static GlFrameProcessor createZoomInTransitionFrameProcessor() {
-    return new AdvancedFrameProcessor(
-        /* matrixProvider= */ AdvancedFrameProcessorFactory::calculateZoomInTransitionMatrix);
+  public static MatrixTransformation createZoomInTransition() {
+    return MatrixTransformationFactory::calculateZoomInTransitionMatrix;
   }
 
   /**
-   * Returns a {@link GlFrameProcessor} that crops frames to a rectangle that moves on an ellipse.
+   * Returns a {@link MatrixTransformation} that crops frames to a rectangle that moves on an
+   * ellipse.
    */
-  public static GlFrameProcessor createDizzyCropFrameProcessor() {
-    return new AdvancedFrameProcessor(
-        /* matrixProvider= */ AdvancedFrameProcessorFactory::calculateDizzyCropMatrix);
+  public static MatrixTransformation createDizzyCropEffect() {
+    return MatrixTransformationFactory::calculateDizzyCropMatrix;
   }
 
   /**
-   * Returns a {@link GlFrameProcessor} that rotates a frame in 3D around the y-axis and applies
-   * perspective projection to 2D.
+   * Returns a {@link GlMatrixTransformation} that rotates a frame in 3D around the y-axis and
+   * applies perspective projection to 2D.
    */
-  public static GlFrameProcessor createSpin3dFrameProcessor() {
-    return new AdvancedFrameProcessor(
-        /* matrixProvider= */ AdvancedFrameProcessorFactory::calculate3dSpinMatrix);
+  public static GlMatrixTransformation createSpin3dEffect() {
+    return MatrixTransformationFactory::calculate3dSpinMatrix;
   }
 
   private static final float ZOOM_DURATION_SECONDS = 2f;

demos/transformer/src/main/java/com/google/android/exoplayer2/transformerdemo/TransformerActivity.java

@@ -246,7 +246,7 @@ public final class TransformerActivity extends AppCompatActivity {
           bundle.getBooleanArray(ConfigurationActivity.DEMO_EFFECTS_SELECTIONS);
       if (selectedEffects != null) {
         if (selectedEffects[0]) {
-          effects.add(AdvancedFrameProcessorFactory::createDizzyCropFrameProcessor);
+          effects.add(MatrixTransformationFactory.createDizzyCropEffect());
         }
         if (selectedEffects[1]) {
           effects.add(
@@ -261,13 +261,13 @@ public final class TransformerActivity extends AppCompatActivity {
                       bundle.getFloat(ConfigurationActivity.PERIODIC_VIGNETTE_OUTER_RADIUS)));
         }
         if (selectedEffects[2]) {
-          effects.add(AdvancedFrameProcessorFactory::createSpin3dFrameProcessor);
+          effects.add(MatrixTransformationFactory.createSpin3dEffect());
         }
         if (selectedEffects[3]) {
           effects.add(BitmapOverlayFrameProcessor::new);
         }
         if (selectedEffects[4]) {
-          effects.add(AdvancedFrameProcessorFactory::createZoomInTransitionFrameProcessor);
+          effects.add(MatrixTransformationFactory.createZoomInTransition());
         }
         transformerBuilder.setVideoFrameEffects(effects.build());
       }

library/transformer/src/androidTest/java/com/google/android/exoplayer2/transformer/FrameProcessorChainPixelTest.java

@@ -124,13 +124,14 @@ public final class FrameProcessorChainPixelTest {
   }
 
   @Test
-  public void processData_withAdvancedFrameProcessor_translateRight_producesExpectedOutput()
+  public void processData_withMatrixTransformation_translateRight_producesExpectedOutput()
       throws Exception {
-    String testId = "processData_withAdvancedFrameProcessor_translateRight";
+    String testId = "processData_withMatrixTransformation_translateRight";
     Matrix translateRightMatrix = new Matrix();
     translateRightMatrix.postTranslate(/* dx= */ 1, /* dy= */ 0);
-    GlFrameProcessor glFrameProcessor = new AdvancedFrameProcessor(translateRightMatrix);
-    setUpAndPrepareFirstFrame(DEFAULT_PIXEL_WIDTH_HEIGHT_RATIO, () -> glFrameProcessor);
+    setUpAndPrepareFirstFrame(
+        DEFAULT_PIXEL_WIDTH_HEIGHT_RATIO,
+        (MatrixTransformation) (long presentationTimeNs) -> translateRightMatrix);
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(TRANSLATE_RIGHT_PNG_ASSET_PATH);
 
     Bitmap actualBitmap = processFirstFrameAndEnd();
@@ -145,19 +146,15 @@ public final class FrameProcessorChainPixelTest {
   }
 
   @Test
-  public void processData_withAdvancedAndScaleToFitFrameProcessors_producesExpectedOutput()
+  public void processData_withMatrixAndScaleToFitTransformation_producesExpectedOutput()
       throws Exception {
-    String testId = "processData_withAdvancedAndScaleToFitFrameProcessors";
+    String testId = "processData_withMatrixAndScaleToFitTransformation";
     Matrix translateRightMatrix = new Matrix();
     translateRightMatrix.postTranslate(/* dx= */ 1, /* dy= */ 0);
-    GlFrameProcessor translateRightFrameProcessor =
-        new AdvancedFrameProcessor(translateRightMatrix);
-    GlFrameProcessor rotate45FrameProcessor =
-        new ScaleToFitFrameProcessor.Builder().setRotationDegrees(45).build();
     setUpAndPrepareFirstFrame(
         DEFAULT_PIXEL_WIDTH_HEIGHT_RATIO,
-        () -> translateRightFrameProcessor,
-        () -> rotate45FrameProcessor);
+        (MatrixTransformation) (long presentationTimeUs) -> translateRightMatrix,
+        () -> new ScaleToFitFrameProcessor.Builder().setRotationDegrees(45).build());
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(TRANSLATE_THEN_ROTATE_PNG_ASSET_PATH);
 
     Bitmap actualBitmap = processFirstFrameAndEnd();
@@ -172,19 +169,15 @@ public final class FrameProcessorChainPixelTest {
   }
 
   @Test
-  public void processData_withScaleToFitAndAdvancedFrameProcessors_producesExpectedOutput()
+  public void processData_withScaleToFitAndMatrixTransformation_producesExpectedOutput()
       throws Exception {
-    String testId = "processData_withScaleToFitAndAdvancedFrameProcessors";
-    GlFrameProcessor rotate45FrameProcessor =
-        new ScaleToFitFrameProcessor.Builder().setRotationDegrees(45).build();
+    String testId = "processData_withScaleToFitAndMatrixTransformation";
     Matrix translateRightMatrix = new Matrix();
     translateRightMatrix.postTranslate(/* dx= */ 1, /* dy= */ 0);
-    GlFrameProcessor translateRightFrameProcessor =
-        new AdvancedFrameProcessor(translateRightMatrix);
     setUpAndPrepareFirstFrame(
         DEFAULT_PIXEL_WIDTH_HEIGHT_RATIO,
-        () -> rotate45FrameProcessor,
-        () -> translateRightFrameProcessor);
+        () -> new ScaleToFitFrameProcessor.Builder().setRotationDegrees(45).build(),
+        (MatrixTransformation) (long presentationTimeUs) -> translateRightMatrix);
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(ROTATE_THEN_TRANSLATE_PNG_ASSET_PATH);
 
     Bitmap actualBitmap = processFirstFrameAndEnd();
@@ -199,12 +192,11 @@ public final class FrameProcessorChainPixelTest {
   }
 
   @Test
-  public void processData_withPresentationFrameProcessor_setResolution_producesExpectedOutput()
-      throws Exception {
-    String testId = "processData_withPresentationFrameProcessor_setResolution";
-    GlFrameProcessor glFrameProcessor =
-        new PresentationFrameProcessor.Builder().setResolution(480).build();
-    setUpAndPrepareFirstFrame(DEFAULT_PIXEL_WIDTH_HEIGHT_RATIO, () -> glFrameProcessor);
+  public void processData_withPresentation_setResolution_producesExpectedOutput() throws Exception {
+    String testId = "processData_withPresentation_setResolution";
+    setUpAndPrepareFirstFrame(
+        DEFAULT_PIXEL_WIDTH_HEIGHT_RATIO,
+        () -> new PresentationFrameProcessor.Builder().setResolution(480).build());
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(REQUEST_OUTPUT_HEIGHT_PNG_ASSET_PATH);
 
     Bitmap actualBitmap = processFirstFrameAndEnd();
@@ -219,12 +211,12 @@ public final class FrameProcessorChainPixelTest {
   }
 
   @Test
-  public void processData_withScaleToFitFrameProcessor_rotate45_producesExpectedOutput()
+  public void processData_withScaleToFitTransformation_rotate45_producesExpectedOutput()
       throws Exception {
-    String testId = "processData_withScaleToFitFrameProcessor_rotate45";
-    GlFrameProcessor glFrameProcessor =
-        new ScaleToFitFrameProcessor.Builder().setRotationDegrees(45).build();
-    setUpAndPrepareFirstFrame(DEFAULT_PIXEL_WIDTH_HEIGHT_RATIO, () -> glFrameProcessor);
+    String testId = "processData_withScaleToFitTransformation_rotate45";
+    setUpAndPrepareFirstFrame(
+        DEFAULT_PIXEL_WIDTH_HEIGHT_RATIO,
+        () -> new ScaleToFitFrameProcessor.Builder().setRotationDegrees(45).build());
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(ROTATE45_SCALE_TO_FIT_PNG_ASSET_PATH);
 
     Bitmap actualBitmap = processFirstFrameAndEnd();

library/transformer/src/androidTest/java/com/google/android/exoplayer2/transformer/AdvancedFrameProcessorPixelTest.java → library/transformer/src/androidTest/java/com/google/android/exoplayer2/transformer/MatrixTransformationFrameProcessorPixelTest.java

@@ -34,7 +34,7 @@ import org.junit.Test;
 import org.junit.runner.RunWith;
 
 /**
- * Pixel test for frame processing via {@link AdvancedFrameProcessor}.
+ * Pixel test for frame processing via {@link MatrixTransformationFrameProcessor}.
  *
  * <p>Expected images are taken from an emulator, so tests on different emulators or physical
  * devices may fail. To test on other devices, please increase the {@link
@@ -42,7 +42,7 @@ import org.junit.runner.RunWith;
  * as recommended in {@link FrameProcessorChainPixelTest}.
  */
 @RunWith(AndroidJUnit4.class)
-public final class AdvancedFrameProcessorPixelTest {
+public final class MatrixTransformationFrameProcessorPixelTest {
   public static final String ORIGINAL_PNG_ASSET_PATH =
       "media/bitmap/sample_mp4_first_frame/original.png";
   public static final String TRANSLATE_RIGHT_PNG_ASSET_PATH =
@@ -58,7 +58,7 @@ public final class AdvancedFrameProcessorPixelTest {
 
   private final EGLDisplay eglDisplay = GlUtil.createEglDisplay();
   private final EGLContext eglContext = GlUtil.createEglContext(eglDisplay);
-  private @MonotonicNonNull GlFrameProcessor advancedFrameProcessor;
+  private @MonotonicNonNull GlFrameProcessor matrixTransformationFrameProcessor;
   private int inputTexId;
   private int outputTexId;
   private int width;
@@ -80,8 +80,8 @@ public final class AdvancedFrameProcessorPixelTest {
 
   @After
   public void release() {
-    if (advancedFrameProcessor != null) {
-      advancedFrameProcessor.release();
+    if (matrixTransformationFrameProcessor != null) {
+      matrixTransformationFrameProcessor.release();
     }
     GlUtil.destroyEglContext(eglDisplay, eglContext);
   }
@@ -90,11 +90,13 @@ public final class AdvancedFrameProcessorPixelTest {
   public void drawFrame_noEdits_producesExpectedOutput() throws Exception {
     String testId = "drawFrame_noEdits";
     Matrix identityMatrix = new Matrix();
-    advancedFrameProcessor = new AdvancedFrameProcessor(identityMatrix);
-    advancedFrameProcessor.initialize(getApplicationContext(), inputTexId, width, height);
+    matrixTransformationFrameProcessor =
+        new MatrixTransformationFrameProcessor((long presentationTimeUs) -> identityMatrix);
+    matrixTransformationFrameProcessor.initialize(
+        getApplicationContext(), inputTexId, width, height);
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(ORIGINAL_PNG_ASSET_PATH);
 
-    advancedFrameProcessor.drawFrame(/* presentationTimeUs= */ 0);
+    matrixTransformationFrameProcessor.drawFrame(/* presentationTimeUs= */ 0);
     Bitmap actualBitmap =
         BitmapTestUtil.createArgb8888BitmapFromCurrentGlFramebuffer(width, height);
 
@@ -112,11 +114,13 @@ public final class AdvancedFrameProcessorPixelTest {
     String testId = "drawFrame_translateRight";
     Matrix translateRightMatrix = new Matrix();
     translateRightMatrix.postTranslate(/* dx= */ 1, /* dy= */ 0);
-    advancedFrameProcessor = new AdvancedFrameProcessor(translateRightMatrix);
-    advancedFrameProcessor.initialize(getApplicationContext(), inputTexId, width, height);
+    matrixTransformationFrameProcessor =
+        new MatrixTransformationFrameProcessor((long presentationTimeUs) -> translateRightMatrix);
+    matrixTransformationFrameProcessor.initialize(
+        getApplicationContext(), inputTexId, width, height);
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(TRANSLATE_RIGHT_PNG_ASSET_PATH);
 
-    advancedFrameProcessor.drawFrame(/* presentationTimeUs= */ 0);
+    matrixTransformationFrameProcessor.drawFrame(/* presentationTimeUs= */ 0);
     Bitmap actualBitmap =
         BitmapTestUtil.createArgb8888BitmapFromCurrentGlFramebuffer(width, height);
 
@@ -134,11 +138,13 @@ public final class AdvancedFrameProcessorPixelTest {
     String testId = "drawFrame_scaleNarrow";
     Matrix scaleNarrowMatrix = new Matrix();
     scaleNarrowMatrix.postScale(.5f, 1.2f);
-    advancedFrameProcessor = new AdvancedFrameProcessor(scaleNarrowMatrix);
-    advancedFrameProcessor.initialize(getApplicationContext(), inputTexId, width, height);
+    matrixTransformationFrameProcessor =
+        new MatrixTransformationFrameProcessor((long presentationTimeUs) -> scaleNarrowMatrix);
+    matrixTransformationFrameProcessor.initialize(
+        getApplicationContext(), inputTexId, width, height);
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(SCALE_NARROW_PNG_ASSET_PATH);
 
-    advancedFrameProcessor.drawFrame(/* presentationTimeUs= */ 0);
+    matrixTransformationFrameProcessor.drawFrame(/* presentationTimeUs= */ 0);
     Bitmap actualBitmap =
         BitmapTestUtil.createArgb8888BitmapFromCurrentGlFramebuffer(width, height);
 
@@ -156,11 +162,13 @@ public final class AdvancedFrameProcessorPixelTest {
     String testId = "drawFrame_rotate90";
     Matrix rotate90Matrix = new Matrix();
     rotate90Matrix.postRotate(/* degrees= */ 90);
-    advancedFrameProcessor = new AdvancedFrameProcessor(rotate90Matrix);
-    advancedFrameProcessor.initialize(getApplicationContext(), inputTexId, width, height);
+    matrixTransformationFrameProcessor =
+        new MatrixTransformationFrameProcessor((long presentationTimeUs) -> rotate90Matrix);
+    matrixTransformationFrameProcessor.initialize(
+        getApplicationContext(), inputTexId, width, height);
     Bitmap expectedBitmap = BitmapTestUtil.readBitmap(ROTATE_90_PNG_ASSET_PATH);
 
-    advancedFrameProcessor.drawFrame(/* presentationTimeUs= */ 0);
+    matrixTransformationFrameProcessor.drawFrame(/* presentationTimeUs= */ 0);
     Bitmap actualBitmap =
         BitmapTestUtil.createArgb8888BitmapFromCurrentGlFramebuffer(width, height);
 

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

+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.transformer;
+
+import android.opengl.Matrix;
+import android.util.Size;
+
+/**
+ * Specifies a 4x4 transformation {@link Matrix} to apply in the vertex shader for each frame.
+ *
+ * <p>The matrix is applied to points given in normalized device coordinates (-1 to 1 on x, y, and z
+ * axes). Transformed pixels that are moved outside of the normal device coordinate range are
+ * clipped.
+ *
+ * <p>Output frame pixels outside of the transformed input frame will be black.
+ */
+public interface GlMatrixTransformation extends GlEffect {
+  /**
+   * Configures the input and output dimensions.
+   *
+   * <p>Must be called before {@link #getGlMatrixArray(long)}.
+   *
+   * @param inputWidth The input frame width, in pixels.
+   * @param inputHeight The input frame height, in pixels.
+   * @return The output frame {@link Size}, in pixels.
+   */
+  default Size configure(int inputWidth, int inputHeight) {
+    return new Size(inputWidth, inputHeight);
+  }
+
+  /**
+   * Returns the 4x4 transformation {@link Matrix} to apply to the frame with the given timestamp.
+   */
+  float[] getGlMatrixArray(long presentationTimeUs);
+
+  @Override
+  default GlFrameProcessor toGlFrameProcessor() {
+    return new MatrixTransformationFrameProcessor(this);
+  }
+}

library/transformer/src/test/java/com/google/android/exoplayer2/transformer/AdvancedFrameProcessorTest.java → library/transformer/src/main/java/com/google/android/exoplayer2/transformer/MatrixTransformation.java

@@ -15,30 +15,25 @@
  */
 package com.google.android.exoplayer2.transformer;
 
-import static org.junit.Assert.assertThrows;
-
-import androidx.test.ext.junit.runners.AndroidJUnit4;
-import org.junit.Test;
-import org.junit.runner.RunWith;
+import android.graphics.Matrix;
 
 /**
- * Unit tests for {@link AdvancedFrameProcessor}.
+ * Specifies a 3x3 transformation {@link Matrix} to apply in the vertex shader for each frame.
+ *
+ * <p>The matrix is applied to points given in normalized device coordinates (-1 to 1 on x and y
+ * axes). Transformed pixels that are moved outside of the normal device coordinate range are
+ * clipped.
  *
- * <p>See {@code AdvancedFrameProcessorPixelTest} for pixel tests testing {@link
- * AdvancedFrameProcessor} given a transformation matrix.
+ * <p>Output frame pixels outside of the transformed input frame will be black.
  */
-@RunWith(AndroidJUnit4.class)
-public final class AdvancedFrameProcessorTest {
-
-  @Test
-  public void construct_withInvalidMatrixSize_throwsException() {
-    assertThrows(
-        IllegalArgumentException.class,
-        () -> new AdvancedFrameProcessor(/* transformationMatrix= */ new float[4]));
-  }
+public interface MatrixTransformation extends GlMatrixTransformation {
+  /**
+   * Returns the 3x3 transformation {@link Matrix} to apply to the frame with the given timestamp.
+   */
+  Matrix getMatrix(long presentationTimeUs);
 
-  @Test
-  public void construct_withValidMatrixSize_completesSuccessfully() {
-    new AdvancedFrameProcessor(/* transformationMatrix= */ new float[16]);
+  @Override
+  default float[] getGlMatrixArray(long presentationTimeUs) {
+    return MatrixUtils.getGlMatrixArray(getMatrix(presentationTimeUs));
   }
 }

library/transformer/src/main/java/com/google/android/exoplayer2/transformer/AdvancedFrameProcessor.java → library/transformer/src/main/java/com/google/android/exoplayer2/transformer/MatrixTransformationFrameProcessor.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.transformer;
 
 import static com.google.android.exoplayer2.util.Assertions.checkArgument;
+import static com.google.android.exoplayer2.util.Assertions.checkState;
 import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull;
 
 import android.content.Context;
@@ -32,133 +33,45 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
  *
  * <p>Operations are done on normalized device coordinates (-1 to 1 on x and y axes). No automatic
  * adjustments (like done in {@link ScaleToFitFrameProcessor}) are applied on the transformation.
- * Width and height are not modified.
  *
  * <p>The background color of the output frame will be black.
  */
+// TODO(b/227625423): Compose multiple transformation matrices in a single shader with clipping
+//  after each matrix.
 @SuppressWarnings("FunctionalInterfaceClash") // b/228192298
-public final class AdvancedFrameProcessor implements GlFrameProcessor {
+public final class MatrixTransformationFrameProcessor implements GlFrameProcessor {
 
   static {
     GlUtil.glAssertionsEnabled = true;
   }
 
-  /** Updates the transformation {@link android.opengl.Matrix} for each frame. */
-  public interface GlMatrixProvider {
-    /**
-     * Updates the transformation {@link android.opengl.Matrix} to apply to the frame with the given
-     * timestamp in place.
-     */
-    float[] getGlMatrixArray(long presentationTimeUs);
-  }
-
-  /** Provides a {@link android.graphics.Matrix} for each frame. */
-  public interface MatrixProvider extends GlMatrixProvider {
-    /**
-     * Returns the transformation {@link android.graphics.Matrix} to apply to the frame with the
-     * given timestamp.
-     */
-    android.graphics.Matrix getMatrix(long presentationTimeUs);
-
-    @Override
-    default float[] getGlMatrixArray(long presentationTimeUs) {
-      return AdvancedFrameProcessor.getGlMatrixArray(getMatrix(presentationTimeUs));
-    }
-  }
-
   private static final String VERTEX_SHADER_TRANSFORMATION_PATH =
       "shaders/vertex_shader_transformation_es2.glsl";
   private static final String FRAGMENT_SHADER_PATH = "shaders/fragment_shader_copy_es2.glsl";
 
-  /**
-   * Returns a 4x4, column-major {@link android.opengl.Matrix} float array, from an input {@link
-   * android.graphics.Matrix}.
-   *
-   * <p>This is useful for converting to the 4x4 column-major format commonly used in OpenGL.
-   */
-  private static float[] getGlMatrixArray(android.graphics.Matrix matrix) {
-    float[] matrix3x3Array = new float[9];
-    matrix.getValues(matrix3x3Array);
-    float[] matrix4x4Array = getMatrix4x4Array(matrix3x3Array);
-
-    // Transpose from row-major to column-major representations.
-    float[] transposedMatrix4x4Array = new float[16];
-    android.opengl.Matrix.transposeM(
-        transposedMatrix4x4Array, /* mTransOffset= */ 0, matrix4x4Array, /* mOffset= */ 0);
-
-    return transposedMatrix4x4Array;
-  }
+  private final GlMatrixTransformation matrixTransformation;
 
-  /**
-   * Returns a 4x4 matrix array containing the 3x3 matrix array's contents.
-   *
-   * <p>The 3x3 matrix array is expected to be in 2 dimensions, and the 4x4 matrix array is expected
-   * to be in 3 dimensions. The output will have the third row/column's values be an identity
-   * matrix's values, so that vertex transformations using this matrix will not affect the z axis.
-   * <br>
-   * Input format: [a, b, c, d, e, f, g, h, i] <br>
-   * Output format: [a, b, 0, c, d, e, 0, f, 0, 0, 1, 0, g, h, 0, i]
-   */
-  private static float[] getMatrix4x4Array(float[] matrix3x3Array) {
-    float[] matrix4x4Array = new float[16];
-    matrix4x4Array[10] = 1;
-    for (int inputRow = 0; inputRow < 3; inputRow++) {
-      for (int inputColumn = 0; inputColumn < 3; inputColumn++) {
-        int outputRow = (inputRow == 2) ? 3 : inputRow;
-        int outputColumn = (inputColumn == 2) ? 3 : inputColumn;
-        matrix4x4Array[outputRow * 4 + outputColumn] = matrix3x3Array[inputRow * 3 + inputColumn];
-      }
-    }
-    return matrix4x4Array;
-  }
-
-  private final GlMatrixProvider matrixProvider;
-
-  private @MonotonicNonNull Size size;
+  private @MonotonicNonNull Size outputSize;
   private @MonotonicNonNull GlProgram glProgram;
 
   /**
    * Creates a new instance.
    *
-   * @param transformationMatrix The transformation {@link android.graphics.Matrix} to apply to each
-   *     frame. Operations are done on normalized device coordinates (-1 to 1 on x and y), and no
-   *     automatic adjustments are applied on the transformation matrix.
-   */
-  public AdvancedFrameProcessor(android.graphics.Matrix transformationMatrix) {
-    this(getGlMatrixArray(transformationMatrix));
-  }
-
-  /**
-   * Creates a new instance.
-   *
-   * @param matrixProvider A {@link MatrixProvider} that provides the transformation matrix to apply
-   *     to each frame.
-   */
-  public AdvancedFrameProcessor(MatrixProvider matrixProvider) {
-    this.matrixProvider = matrixProvider;
-  }
-
-  /**
-   * Creates a new instance.
-   *
-   * @param transformationMatrix The 4x4 transformation {@link android.opengl.Matrix} to apply to
-   *     each frame. Operations are done on normalized device coordinates (-1 to 1 on x and y), and
-   *     no automatic adjustments are applied on the transformation matrix.
+   * @param matrixTransformation A {@link MatrixTransformation} that specifies the transformation
+   *     matrix to use for each frame.
    */
-  public AdvancedFrameProcessor(float[] transformationMatrix) {
-    this(/* matrixProvider= */ (long presentationTimeUs) -> transformationMatrix.clone());
-    checkArgument(
-        transformationMatrix.length == 16, "A 4x4 transformation matrix must have 16 elements.");
+  public MatrixTransformationFrameProcessor(MatrixTransformation matrixTransformation) {
+    this.matrixTransformation = matrixTransformation;
   }
 
   /**
    * Creates a new instance.
    *
-   * @param matrixProvider A {@link GlMatrixProvider} that updates the transformation matrix for
-   *     each frame.
+   * @param matrixTransformation A {@link GlMatrixTransformation} that specifies the transformation
+   *     matrix to use for each frame.
    */
-  public AdvancedFrameProcessor(GlMatrixProvider matrixProvider) {
-    this.matrixProvider = matrixProvider;
+  public MatrixTransformationFrameProcessor(GlMatrixTransformation matrixTransformation) {
+    this.matrixTransformation = matrixTransformation;
   }
 
   @Override
@@ -167,7 +80,7 @@ public final class AdvancedFrameProcessor implements GlFrameProcessor {
     checkArgument(inputWidth > 0, "inputWidth must be positive");
     checkArgument(inputHeight > 0, "inputHeight must be positive");
 
-    size = new Size(inputWidth, inputHeight);
+    outputSize = matrixTransformation.configure(inputWidth, inputHeight);
     // TODO(b/205002913): check the loaded program is consistent with the attributes and uniforms
     //  expected in the code.
     glProgram = new GlProgram(context, VERTEX_SHADER_TRANSFORMATION_PATH, FRAGMENT_SHADER_PATH);
@@ -181,14 +94,16 @@ public final class AdvancedFrameProcessor implements GlFrameProcessor {
 
   @Override
   public Size getOutputSize() {
-    return checkStateNotNull(size);
+    return checkStateNotNull(outputSize);
   }
 
   @Override
   public void drawFrame(long presentationTimeUs) {
     checkStateNotNull(glProgram).use();
-    glProgram.setFloatsUniform(
-        "uTransformationMatrix", matrixProvider.getGlMatrixArray(presentationTimeUs));
+    float[] transformationMatrix = matrixTransformation.getGlMatrixArray(presentationTimeUs);
+    checkState(
+        transformationMatrix.length == 16, "A 4x4 transformation matrix must have 16 elements");
+    glProgram.setFloatsUniform("uTransformationMatrix", transformationMatrix);
     glProgram.bindAttributesAndUniforms();
     // The four-vertex triangle strip forms a quad.
     GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, /* first= */ 0, /* count= */ 4);

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

+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.transformer;
+
+/** Utility functions for working with matrices. */
+/* package */ class MatrixUtils {
+  /**
+   * Returns a 4x4, column-major {@link android.opengl.Matrix} float array, from an input {@link
+   * android.graphics.Matrix}.
+   *
+   * <p>This is useful for converting to the 4x4 column-major format commonly used in OpenGL.
+   */
+  public static float[] getGlMatrixArray(android.graphics.Matrix matrix) {
+    float[] matrix3x3Array = new float[9];
+    matrix.getValues(matrix3x3Array);
+    float[] matrix4x4Array = getMatrix4x4Array(matrix3x3Array);
+
+    // Transpose from row-major to column-major representations.
+    float[] transposedMatrix4x4Array = new float[16];
+    android.opengl.Matrix.transposeM(
+        transposedMatrix4x4Array, /* mTransOffset= */ 0, matrix4x4Array, /* mOffset= */ 0);
+
+    return transposedMatrix4x4Array;
+  }
+
+  /**
+   * Returns a 4x4 matrix array containing the 3x3 matrix array's contents.
+   *
+   * <p>The 3x3 matrix array is expected to be in 2 dimensions, and the 4x4 matrix array is expected
+   * to be in 3 dimensions. The output will have the third row/column's values be an identity
+   * matrix's values, so that vertex transformations using this matrix will not affect the z axis.
+   * <br>
+   * Input format: [a, b, c, d, e, f, g, h, i] <br>
+   * Output format: [a, b, 0, c, d, e, 0, f, 0, 0, 1, 0, g, h, 0, i]
+   */
+  private static float[] getMatrix4x4Array(float[] matrix3x3Array) {
+    float[] matrix4x4Array = new float[16];
+    matrix4x4Array[10] = 1;
+    for (int inputRow = 0; inputRow < 3; inputRow++) {
+      for (int inputColumn = 0; inputColumn < 3; inputColumn++) {
+        int outputRow = (inputRow == 2) ? 3 : inputRow;
+        int outputColumn = (inputColumn == 2) ? 3 : inputColumn;
+        matrix4x4Array[outputRow * 4 + outputColumn] = matrix3x3Array[inputRow * 3 + inputColumn];
+      }
+    }
+    return matrix4x4Array;
+  }
+
+  /** Class only contains static methods. */
+  private MatrixUtils() {}
+}

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

@@ -46,6 +46,8 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
  *
  * <p>The background color of the output frame will be black.
  */
+// TODO(b/227625423): Implement MatrixTransformation instead of wrapping
+//  MatrixTransformationFrameProcessor.
 public final class PresentationFrameProcessor implements GlFrameProcessor {
   /**
    * Strategies controlling the layout of input pixels in the output frame.
@@ -235,7 +237,7 @@ public final class PresentationFrameProcessor implements GlFrameProcessor {
   private float outputHeight;
   private @MonotonicNonNull Size outputSize;
   private @MonotonicNonNull Matrix transformationMatrix;
-  private @MonotonicNonNull AdvancedFrameProcessor advancedFrameProcessor;
+  private @MonotonicNonNull MatrixTransformationFrameProcessor matrixTransformationFrameProcessor;
 
   /** Creates a new instance. */
   private PresentationFrameProcessor(
@@ -263,8 +265,11 @@ public final class PresentationFrameProcessor implements GlFrameProcessor {
   public void initialize(Context context, int inputTexId, int inputWidth, int inputHeight)
       throws IOException {
     configureOutputSizeAndTransformationMatrix(inputWidth, inputHeight);
-    advancedFrameProcessor = new AdvancedFrameProcessor(transformationMatrix);
-    advancedFrameProcessor.initialize(context, inputTexId, inputWidth, inputHeight);
+    matrixTransformationFrameProcessor =
+        new MatrixTransformationFrameProcessor(
+            /* matrixTransformation= */ (long presentationTimeUs) ->
+                checkStateNotNull(transformationMatrix));
+    matrixTransformationFrameProcessor.initialize(context, inputTexId, inputWidth, inputHeight);
   }
 
   @Override
@@ -277,13 +282,13 @@ public final class PresentationFrameProcessor implements GlFrameProcessor {
 
   @Override
   public void drawFrame(long presentationTimeUs) {
-    checkStateNotNull(advancedFrameProcessor).drawFrame(presentationTimeUs);
+    checkStateNotNull(matrixTransformationFrameProcessor).drawFrame(presentationTimeUs);
   }
 
   @Override
   public void release() {
-    if (advancedFrameProcessor != null) {
-      advancedFrameProcessor.release();
+    if (matrixTransformationFrameProcessor != null) {
+      matrixTransformationFrameProcessor.release();
     }
   }
 

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

@@ -37,6 +37,8 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
  *
  * <p>The background color of the output frame will be black.
  */
+// TODO(b/227625423): Implement MatrixTransformation instead of wrapping
+//  MatrixTransformationFrameProcessor.
 public final class ScaleToFitFrameProcessor implements GlFrameProcessor {
 
   /** A builder for {@link ScaleToFitFrameProcessor} instances. */
@@ -93,7 +95,7 @@ public final class ScaleToFitFrameProcessor implements GlFrameProcessor {
 
   private final Matrix transformationMatrix;
 
-  private @MonotonicNonNull AdvancedFrameProcessor advancedFrameProcessor;
+  private @MonotonicNonNull MatrixTransformationFrameProcessor matrixTransformationFrameProcessor;
   private @MonotonicNonNull Size outputSize;
   private @MonotonicNonNull Matrix adjustedTransformationMatrix;
 
@@ -114,8 +116,11 @@ public final class ScaleToFitFrameProcessor implements GlFrameProcessor {
   public void initialize(Context context, int inputTexId, int inputWidth, int inputHeight)
       throws IOException {
     configureOutputSizeAndTransformationMatrix(inputWidth, inputHeight);
-    advancedFrameProcessor = new AdvancedFrameProcessor(adjustedTransformationMatrix);
-    advancedFrameProcessor.initialize(context, inputTexId, inputWidth, inputHeight);
+    matrixTransformationFrameProcessor =
+        new MatrixTransformationFrameProcessor(
+            /* matrixTransformation= */ (long presentationTimeUs) ->
+                checkStateNotNull(adjustedTransformationMatrix));
+    matrixTransformationFrameProcessor.initialize(context, inputTexId, inputWidth, inputHeight);
   }
 
   @Override
@@ -125,13 +130,13 @@ public final class ScaleToFitFrameProcessor implements GlFrameProcessor {
 
   @Override
   public void drawFrame(long presentationTimeUs) {
-    checkStateNotNull(advancedFrameProcessor).drawFrame(presentationTimeUs);
+    checkStateNotNull(matrixTransformationFrameProcessor).drawFrame(presentationTimeUs);
   }
 
   @Override
   public void release() {
-    if (advancedFrameProcessor != null) {
-      advancedFrameProcessor.release();
+    if (matrixTransformationFrameProcessor != null) {
+      matrixTransformationFrameProcessor.release();
     }
   }