Fix texture transformation in gldemo

`SurfaceTexture` provides a transform matrix with each buffer. Previously
gldemo ignored this but it is important to apply it to have the video render
properly.

The transformation matrix from the surface texture includes flipping so this
change removes the hard-coded flipping from `a_texcoord`.

Issue: #8992

#minor-release

PiperOrigin-RevId: 377271389

RELEASENOTES.md

@@ -90,6 +90,9 @@
         ([#8985](https://github.com/google/ExoPlayer/issues/8985)).
 *   RTSP:
     *   Add support for RTSP basic and digest authentication.
+*   GL demo app:
+    *   Fix texture transformation to avoid green bars shown on some videos
+        ([#8992](https://github.com/google/ExoPlayer/issues/8992)).
 
 ### 2.14.0 (2021-05-13)
 

demos/gl/src/main/assets/bitmap_overlay_video_processor_vertex.glsl

@@ -11,10 +11,11 @@
 // 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.
-attribute vec2 a_position;
-attribute vec2 a_texcoord;
+attribute vec4 a_position;
+attribute vec4 a_texcoord;
+uniform mat4 tex_transform;
 varying vec2 v_texcoord;
 void main() {
- gl_Position = vec4(a_position.x, a_position.y, 0, 1);
- v_texcoord = a_texcoord;
+ gl_Position = a_position;
+ v_texcoord = (tex_transform * a_texcoord).xy;
 }

demos/gl/src/main/java/com/google/android/exoplayer2/gldemo/BitmapOverlayVideoProcessor.java

@@ -88,9 +88,9 @@ import javax.microedition.khronos.opengles.GL10;
     GlUtil.Uniform[] uniforms = GlUtil.getUniforms(program);
     for (GlUtil.Attribute attribute : attributes) {
       if (attribute.name.equals("a_position")) {
-        attribute.setBuffer(new float[] {-1, -1, 1, -1, -1, 1, 1, 1}, 2);
+        attribute.setBuffer(new float[] {-1, -1, 0, 1, 1, -1, 0, 1, -1, 1, 0, 1, 1, 1, 0, 1}, 4);
       } else if (attribute.name.equals("a_texcoord")) {
-        attribute.setBuffer(new float[] {0, 1, 1, 1, 0, 0, 1, 0}, 2);
+        attribute.setBuffer(new float[] {0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1}, 4);
       }
     }
     this.attributes = attributes;
@@ -111,7 +111,7 @@ import javax.microedition.khronos.opengles.GL10;
   }
 
   @Override
-  public void draw(int frameTexture, long frameTimestampUs) {
+  public void draw(int frameTexture, long frameTimestampUs, float[] transformMatrix) {
     // Draw to the canvas and store it in a texture.
     String text = String.format(Locale.US, "%.02f", frameTimestampUs / (float) C.MICROS_PER_SECOND);
     overlayBitmap.eraseColor(Color.TRANSPARENT);
@@ -140,6 +140,9 @@ import javax.microedition.khronos.opengles.GL10;
         case "scaleY":
           uniform.setFloat(bitmapScaleY);
           break;
+        case "tex_transform":
+          uniform.setFloats(transformMatrix);
+          break;
         default: // fall out
       }
     }

demos/gl/src/main/java/com/google/android/exoplayer2/gldemo/VideoProcessingGLSurfaceView.java

@@ -25,6 +25,7 @@ import android.os.Handler;
 import android.view.Surface;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ExoPlayer;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.util.Assertions;
@@ -61,8 +62,9 @@ public final class VideoProcessingGLSurfaceView extends GLSurfaceView {
      *
      * @param frameTexture The ID of a GL texture containing a video frame.
      * @param frameTimestampUs The presentation timestamp of the frame, in microseconds.
+     * @param transformMatrix The 4 * 4 transform matrix to be applied to the texture.
      */
-    void draw(int frameTexture, long frameTimestampUs);
+    void draw(int frameTexture, long frameTimestampUs, float[] transformMatrix);
   }
 
   private static final int EGL_PROTECTED_CONTENT_EXT = 0x32C0;
@@ -214,6 +216,7 @@ public final class VideoProcessingGLSurfaceView extends GLSurfaceView {
     private final VideoProcessor videoProcessor;
     private final AtomicBoolean frameAvailable;
     private final TimedValueQueue<Long> sampleTimestampQueue;
+    private final float[] transformMatrix;
 
     private int texture;
     @Nullable private SurfaceTexture surfaceTexture;
@@ -229,6 +232,8 @@ public final class VideoProcessingGLSurfaceView extends GLSurfaceView {
       sampleTimestampQueue = new TimedValueQueue<>();
       width = -1;
       height = -1;
+      frameTimestampUs = C.TIME_UNSET;
+      transformMatrix = new float[16];
     }
 
     @Override
@@ -271,13 +276,14 @@ public final class VideoProcessingGLSurfaceView extends GLSurfaceView {
         SurfaceTexture surfaceTexture = Assertions.checkNotNull(this.surfaceTexture);
         surfaceTexture.updateTexImage();
         long lastFrameTimestampNs = surfaceTexture.getTimestamp();
-        Long frameTimestampUs = sampleTimestampQueue.poll(lastFrameTimestampNs);
+        @Nullable Long frameTimestampUs = sampleTimestampQueue.poll(lastFrameTimestampNs);
         if (frameTimestampUs != null) {
           this.frameTimestampUs = frameTimestampUs;
         }
+        surfaceTexture.getTransformMatrix(transformMatrix);
       }
 
-      videoProcessor.draw(texture, frameTimestampUs);
+      videoProcessor.draw(texture, frameTimestampUs, transformMatrix);
     }
 
     @Override

library/common/src/main/java/com/google/android/exoplayer2/util/GlUtil.java

@@ -141,7 +141,7 @@ public final class GlUtil {
       location = GLES20.glGetUniformLocation(program, this.name);
       this.type = type[0];
 
-      value = new float[1];
+      value = new float[16];
     }
 
     /**
@@ -160,9 +160,14 @@ public final class GlUtil {
       this.value[0] = value;
     }
 
+    /** Configures {@link #bind()} to use the specified float[] {@code value} for this uniform. */
+    public void setFloats(float[] value) {
+      System.arraycopy(value, 0, this.value, 0, value.length);
+    }
+
     /**
-     * Sets the uniform to whatever value was passed via {@link #setSamplerTexId(int, int)} or
-     * {@link #setFloat(float)}.
+     * Sets the uniform to whatever value was passed via {@link #setSamplerTexId(int, int)}, {@link
+     * #setFloat(float)} or {@link #setFloats(float[])}.
      *
      * <p>Should be called before each drawing call.
      */
@@ -173,6 +178,12 @@ public final class GlUtil {
         return;
       }
 
+      if (type == GLES20.GL_FLOAT_MAT4) {
+        GLES20.glUniformMatrix4fv(location, 1, false, value, 0);
+        checkGlError();
+        return;
+      }
+
       if (texId == 0) {
         throw new IllegalStateException("call setSamplerTexId before bind");
       }