Encapsulate attributes and uniforms within Program

Document that apps should retain `GlUtil.Program` while the program is in use,
and keep a reference to attributes/uniforms within the program to make sure
they don't get GC'd causing any allocated buffers passed to GL to become
invalid.

Tested manually by running gldemo and transformer.

PiperOrigin-RevId: 411516894

demos/gl/src/main/java/androidx/media3/demo/gl/BitmapOverlayVideoProcessor.java

@@ -26,7 +26,6 @@ import android.graphics.Paint;
 import android.graphics.drawable.BitmapDrawable;
 import android.opengl.GLES20;
 import android.opengl.GLUtils;
-import androidx.annotation.Nullable;
 import androidx.media3.common.C;
 import androidx.media3.common.util.GlUtil;
 import java.io.IOException;
@@ -52,8 +51,6 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   private final Canvas overlayCanvas;
 
   private GlUtil.@MonotonicNonNull Program program;
-  @Nullable private GlUtil.Attribute[] attributes;
-  @Nullable private GlUtil.Uniform[] uniforms;
 
   private float bitmapScaleX;
   private float bitmapScaleY;
@@ -88,31 +85,24 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     } catch (IOException e) {
       throw new IllegalStateException(e);
     }
-    program.use();
+    program.setBufferAttribute(
-    GlUtil.Attribute[] attributes = program.getAttributes();
+        "a_position",
-    for (GlUtil.Attribute attribute : attributes) {
+        new float[] {
-      if (attribute.name.equals("a_position")) {
+          -1, -1, 0, 1,
-        attribute.setBuffer(
+          1, -1, 0, 1,
-            new float[] {
+          -1, 1, 0, 1,
-              -1, -1, 0, 1,
+          1, 1, 0, 1
-              1, -1, 0, 1,
+        },
-              -1, 1, 0, 1,
+        4);
-              1, 1, 0, 1
+    program.setBufferAttribute(
-            },
+        "a_texcoord",
-            4);
+        new float[] {
-      } else if (attribute.name.equals("a_texcoord")) {
+          0, 0, 0, 1,
-        attribute.setBuffer(
+          1, 0, 0, 1,
-            new float[] {
+          0, 1, 0, 1,
-              0, 0, 0, 1,
+          1, 1, 0, 1
-              1, 0, 0, 1,
+        },
-              0, 1, 0, 1,
+        4);
-              1, 1, 0, 1
-            },
-            4);
-      }
-    }
-    this.attributes = attributes;
-    this.uniforms = program.getUniforms();
     GLES20.glGenTextures(1, textures, 0);
     GLES20.glBindTexture(GL10.GL_TEXTURE_2D, textures[0]);
     GLES20.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST);
@@ -141,36 +131,22 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     GlUtil.checkGlError();
 
     // Run the shader program.
-    GlUtil.Uniform[] uniforms = checkNotNull(this.uniforms);
+    GlUtil.Program program = checkNotNull(this.program);
-    GlUtil.Attribute[] attributes = checkNotNull(this.attributes);
+    program.setSamplerTexIdUniform("tex_sampler_0", frameTexture, /* unit= */ 0);
-    for (GlUtil.Uniform uniform : uniforms) {
+    program.setSamplerTexIdUniform("tex_sampler_1", textures[0], /* unit= */ 1);
-      switch (uniform.name) {
+    program.setFloatUniform("scaleX", bitmapScaleX);
-        case "tex_sampler_0":
+    program.setFloatUniform("scaleY", bitmapScaleY);
-          uniform.setSamplerTexId(frameTexture, /* unit= */ 0);
+    program.setFloatsUniform("tex_transform", transformMatrix);
-          break;
+    program.bindAttributesAndUniforms();
-        case "tex_sampler_1":
-          uniform.setSamplerTexId(textures[0], /* unit= */ 1);
-          break;
-        case "scaleX":
-          uniform.setFloat(bitmapScaleX);
-          break;
-        case "scaleY":
-          uniform.setFloat(bitmapScaleY);
-          break;
-        case "tex_transform":
-          uniform.setFloats(transformMatrix);
-          break;
-        default: // fall out
-      }
-    }
-    for (GlUtil.Attribute copyExternalAttribute : attributes) {
-      copyExternalAttribute.bind();
-    }
-    for (GlUtil.Uniform copyExternalUniform : uniforms) {
-      copyExternalUniform.bind();
-    }
     GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
     GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, /* first= */ 0, /* count= */ 4);
     GlUtil.checkGlError();
   }
+
+  @Override
+  public void release() {
+    if (program != null) {
+      program.delete();
+    }
+  }
 }

demos/gl/src/main/java/androidx/media3/demo/gl/VideoProcessingGLSurfaceView.java

@@ -64,6 +64,9 @@ public final class VideoProcessingGLSurfaceView extends GLSurfaceView {
      * @param transformMatrix The 4 * 4 transform matrix to be applied to the texture.
      */
     void draw(int frameTexture, long frameTimestampUs, float[] transformMatrix);
+
+    /** Releases any resources associated with this {@link VideoProcessor}. */
+    void release();
   }
 
   private static final int EGL_PROTECTED_CONTENT_EXT = 0x32C0;

libraries/common/src/main/java/androidx/media3/common/util/GlUtil.java

@@ -16,6 +16,7 @@
 package androidx.media3.common.util;
 
 import static android.opengl.GLU.gluErrorString;
+import static androidx.media3.common.util.Assertions.checkNotNull;
 
 import android.content.Context;
 import android.content.pm.PackageManager;
@@ -37,6 +38,8 @@ import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.FloatBuffer;
 import java.nio.IntBuffer;
+import java.util.HashMap;
+import java.util.Map;
 import javax.microedition.khronos.egl.EGL10;
 
 /** GL utilities. */
@@ -54,25 +57,20 @@ public final class GlUtil {
   /** Thrown when the required EGL version is not supported by the device. */
   public static final class UnsupportedEglVersionException extends Exception {}
 
-  /** GL program. */
+  /**
+   * Represents a GLSL shader program.
+   *
+   * <p>After constructing a program, keep a reference for its lifetime and call {@link #delete()}
+   * (or release the current GL context) when it's no longer needed.
+   */
   public static final class Program {
     /** The identifier of a compiled and linked GLSL shader program. */
     private final int programId;
 
-    /**
+    private final Attribute[] attributes;
-     * Compiles a GL shader program from vertex and fragment shader GLSL GLES20 code.
+    private final Uniform[] uniforms;
-     *
+    private final Map<String, Attribute> attributeByName;
-     * @param vertexShaderGlsl The vertex shader program.
+    private final Map<String, Uniform> uniformByName;
-     * @param fragmentShaderGlsl The fragment shader program.
-     */
-    public Program(String vertexShaderGlsl, String fragmentShaderGlsl) {
-      programId = GLES20.glCreateProgram();
-      checkGlError();
-
-      // Add the vertex and fragment shaders.
-      addShader(GLES20.GL_VERTEX_SHADER, vertexShaderGlsl);
-      addShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderGlsl);
-    }
 
     /**
      * Compiles a GL shader program from vertex and fragment shader GLSL GLES20 code.
@@ -87,9 +85,21 @@ public final class GlUtil {
       this(loadAsset(context, vertexShaderFilePath), loadAsset(context, fragmentShaderFilePath));
     }
 
-    /** Uses the program. */
+    /**
-    public void use() {
+     * Compiles a GL shader program from vertex and fragment shader GLSL GLES20 code.
-      // Link and check for errors.
+     *
+     * @param vertexShaderGlsl The vertex shader program.
+     * @param fragmentShaderGlsl The fragment shader program.
+     */
+    public Program(String vertexShaderGlsl, String fragmentShaderGlsl) {
+      programId = GLES20.glCreateProgram();
+      checkGlError();
+
+      // Add the vertex and fragment shaders.
+      addShader(programId, GLES20.GL_VERTEX_SHADER, vertexShaderGlsl);
+      addShader(programId, GLES20.GL_FRAGMENT_SHADER, fragmentShaderGlsl);
+
+      // Link and use the program, and enumerate attributes/uniforms.
       GLES20.glLinkProgram(programId);
       int[] linkStatus = new int[] {GLES20.GL_FALSE};
       GLES20.glGetProgramiv(programId, GLES20.GL_LINK_STATUS, linkStatus, 0);
@@ -97,14 +107,38 @@ public final class GlUtil {
         throwGlException(
             "Unable to link shader program: \n" + GLES20.glGetProgramInfoLog(programId));
       }
-      checkGlError();
-
       GLES20.glUseProgram(programId);
+      attributeByName = new HashMap<>();
+      int[] attributeCount = new int[1];
+      GLES20.glGetProgramiv(programId, GLES20.GL_ACTIVE_ATTRIBUTES, attributeCount, 0);
+      attributes = new Attribute[attributeCount[0]];
+      for (int i = 0; i < attributeCount[0]; i++) {
+        Attribute attribute = Attribute.create(programId, i);
+        attributes[i] = attribute;
+        attributeByName.put(attribute.name, attribute);
+      }
+      uniformByName = new HashMap<>();
+      int[] uniformCount = new int[1];
+      GLES20.glGetProgramiv(programId, GLES20.GL_ACTIVE_UNIFORMS, uniformCount, 0);
+      uniforms = new Uniform[uniformCount[0]];
+      for (int i = 0; i < uniformCount[0]; i++) {
+        Uniform uniform = Uniform.create(programId, i);
+        uniforms[i] = uniform;
+        uniformByName.put(uniform.name, uniform);
+      }
+      checkGlError();
+    }
+
+    /** Uses the program. */
+    public void use() {
+      GLES20.glUseProgram(programId);
+      checkGlError();
     }
 
     /** Deletes the program. Deleted programs cannot be used again. */
     public void delete() {
       GLES20.glDeleteProgram(programId);
+      checkGlError();
     }
 
     /**
@@ -120,234 +154,45 @@ public final class GlUtil {
 
     /** Returns the location of an {@link Attribute}. */
     private int getAttributeLocation(String attributeName) {
-      return GLES20.glGetAttribLocation(programId, attributeName);
+      return GlUtil.getAttributeLocation(programId, attributeName);
     }
 
     /** Returns the location of a {@link Uniform}. */
     public int getUniformLocation(String uniformName) {
-      return GLES20.glGetUniformLocation(programId, uniformName);
+      return GlUtil.getUniformLocation(programId, uniformName);
     }
 
-    /** Returns the program's {@link Attribute}s. */
+    /** Sets a float buffer type attribute. */
-    public Attribute[] getAttributes() {
+    public void setBufferAttribute(String name, float[] values, int size) {
-      int[] attributeCount = new int[1];
+      checkNotNull(attributeByName.get(name)).setBuffer(values, size);
-      GLES20.glGetProgramiv(programId, GLES20.GL_ACTIVE_ATTRIBUTES, attributeCount, 0);
+    }
-      if (attributeCount[0] != 2) {
+
-        throw new IllegalStateException("Expected two attributes but found " + attributeCount[0]);
+    /** Sets a texture sampler type uniform. */
+    public void setSamplerTexIdUniform(String name, int texId, int unit) {
+      checkNotNull(uniformByName.get(name)).setSamplerTexId(texId, unit);
+    }
+
+    /** Sets a float type uniform. */
+    public void setFloatUniform(String name, float value) {
+      checkNotNull(uniformByName.get(name)).setFloat(value);
+    }
+
+    /** Sets a float array type uniform. */
+    public void setFloatsUniform(String name, float[] value) {
+      checkNotNull(uniformByName.get(name)).setFloats(value);
+    }
+
+    /** Binds all attributes and uniforms in the program. */
+    public void bindAttributesAndUniforms() {
+      for (Attribute attribute : attributes) {
+        attribute.bind();
       }
-
+      for (Uniform uniform : uniforms) {
-      Attribute[] attributes = new Attribute[attributeCount[0]];
+        uniform.bind();
-      for (int i = 0; i < attributeCount[0]; i++) {
-        attributes[i] = createAttribute(i);
       }
-      return attributes;
-    }
-
-    /** Returns the program's {@link Uniform}s. */
-    public Uniform[] getUniforms() {
-      int[] uniformCount = new int[1];
-      GLES20.glGetProgramiv(programId, GLES20.GL_ACTIVE_UNIFORMS, uniformCount, 0);
-
-      Uniform[] uniforms = new Uniform[uniformCount[0]];
-      for (int i = 0; i < uniformCount[0]; i++) {
-        uniforms[i] = createUniform(i);
-      }
-
-      return uniforms;
-    }
-
-    private Attribute createAttribute(int index) {
-      int[] length = new int[1];
-      GLES20.glGetProgramiv(programId, GLES20.GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, length, 0);
-
-      int[] type = new int[1];
-      int[] size = new int[1];
-      byte[] nameBytes = new byte[length[0]];
-      int[] ignore = new int[1];
-
-      GLES20.glGetActiveAttrib(
-          programId, index, length[0], ignore, 0, size, 0, type, 0, nameBytes, 0);
-      String name = new String(nameBytes, 0, strlen(nameBytes));
-      int location = getAttributeLocation(name);
-
-      return new Attribute(name, index, location);
-    }
-
-    private Uniform createUniform(int index) {
-      int[] length = new int[1];
-      GLES20.glGetProgramiv(programId, GLES20.GL_ACTIVE_UNIFORM_MAX_LENGTH, length, 0);
-
-      int[] type = new int[1];
-      int[] size = new int[1];
-      byte[] nameBytes = new byte[length[0]];
-      int[] ignore = new int[1];
-
-      GLES20.glGetActiveUniform(
-          programId, index, length[0], ignore, 0, size, 0, type, 0, nameBytes, 0);
-      String name = new String(nameBytes, 0, strlen(nameBytes));
-      int location = getUniformLocation(name);
-
-      return new Uniform(name, location, type[0]);
-    }
-
-    private void addShader(int type, String glsl) {
-      int shader = GLES20.glCreateShader(type);
-      GLES20.glShaderSource(shader, glsl);
-      GLES20.glCompileShader(shader);
-
-      int[] result = new int[] {GLES20.GL_FALSE};
-      GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS, result, 0);
-      if (result[0] != GLES20.GL_TRUE) {
-        throwGlException(GLES20.glGetShaderInfoLog(shader) + ", source: " + glsl);
-      }
-
-      GLES20.glAttachShader(programId, shader);
-      GLES20.glDeleteShader(shader);
-      checkGlError();
     }
   }
 
-  /**
-   * GL attribute, which can be attached to a buffer with {@link Attribute#setBuffer(float[], int)}.
-   */
-  public static final class Attribute {
-
-    /** The name of the attribute in the GLSL sources. */
-    public final String name;
-
-    private final int index;
-    private final int location;
-
-    @Nullable private Buffer buffer;
-    private int size;
-
-    /* Creates a new Attribute. */
-    public Attribute(String name, int index, int location) {
-      this.name = name;
-      this.index = index;
-      this.location = location;
-    }
-
-    /**
-     * Configures {@link #bind()} to attach vertices in {@code buffer} (each of size {@code size}
-     * elements) to this {@link Attribute}.
-     *
-     * @param buffer Buffer to bind to this attribute.
-     * @param size Number of elements per vertex.
-     */
-    public void setBuffer(float[] buffer, int size) {
-      this.buffer = createBuffer(buffer);
-      this.size = size;
-    }
-
-    /**
-     * Sets the vertex attribute to whatever was attached via {@link #setBuffer(float[], int)}.
-     *
-     * <p>Should be called before each drawing call.
-     */
-    public void bind() {
-      Buffer buffer = Assertions.checkNotNull(this.buffer, "call setBuffer before bind");
-      GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);
-      GLES20.glVertexAttribPointer(
-          location,
-          size, // count
-          GLES20.GL_FLOAT, // type
-          false, // normalize
-          0, // stride
-          buffer);
-      GLES20.glEnableVertexAttribArray(index);
-      checkGlError();
-    }
-  }
-
-  /**
-   * GL uniform, which can be attached to a sampler using {@link Uniform#setSamplerTexId(int, int)}.
-   */
-  public static final class Uniform {
-
-    /** The name of the uniform in the GLSL sources. */
-    public final String name;
-
-    private final int location;
-    private final int type;
-    private final float[] value;
-
-    private int texId;
-    private int unit;
-
-    /** Creates a new uniform. */
-    public Uniform(String name, int location, int type) {
-      this.name = name;
-      this.location = location;
-      this.type = type;
-      this.value = new float[16];
-    }
-
-    /**
-     * Configures {@link #bind()} to use the specified {@code texId} for this sampler uniform.
-     *
-     * @param texId The GL texture identifier from which to sample.
-     * @param unit The GL texture unit index.
-     */
-    public void setSamplerTexId(int texId, int unit) {
-      this.texId = texId;
-      this.unit = unit;
-    }
-
-    /** Configures {@link #bind()} to use the specified float {@code value} for this uniform. */
-    public void setFloat(float value) {
-      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)}, {@link
-     * #setFloat(float)} or {@link #setFloats(float[])}.
-     *
-     * <p>Should be called before each drawing call.
-     */
-    public void bind() {
-      if (type == GLES20.GL_FLOAT) {
-        GLES20.glUniform1fv(location, 1, value, 0);
-        checkGlError();
-        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.");
-      }
-      GLES20.glActiveTexture(GLES20.GL_TEXTURE0 + unit);
-      if (type == GLES11Ext.GL_SAMPLER_EXTERNAL_OES) {
-        GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texId);
-      } else if (type == GLES20.GL_SAMPLER_2D) {
-        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texId);
-      } else {
-        throw new IllegalStateException("Unexpected uniform type: " + type);
-      }
-      GLES20.glUniform1i(location, unit);
-      GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);
-      GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR);
-      GLES20.glTexParameteri(
-          GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE);
-      GLES20.glTexParameteri(
-          GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE);
-      checkGlError();
-    }
-  }
-
-  /** Represents an unset texture ID. */
-  public static final int TEXTURE_ID_UNSET = -1;
-
   /** Whether to throw a {@link GlException} in case of an OpenGL error. */
   public static boolean glAssertionsEnabled = false;
 
@@ -532,6 +377,30 @@ public final class GlUtil {
     return texId[0];
   }
 
+  private static void addShader(int programId, int type, String glsl) {
+    int shader = GLES20.glCreateShader(type);
+    GLES20.glShaderSource(shader, glsl);
+    GLES20.glCompileShader(shader);
+
+    int[] result = new int[] {GLES20.GL_FALSE};
+    GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS, result, 0);
+    if (result[0] != GLES20.GL_TRUE) {
+      throwGlException(GLES20.glGetShaderInfoLog(shader) + ", source: " + glsl);
+    }
+
+    GLES20.glAttachShader(programId, shader);
+    GLES20.glDeleteShader(shader);
+    checkGlError();
+  }
+
+  private static int getAttributeLocation(int programId, String attributeName) {
+    return GLES20.glGetAttribLocation(programId, attributeName);
+  }
+
+  private static int getUniformLocation(int programId, String uniformName) {
+    return GLES20.glGetUniformLocation(programId, uniformName);
+  }
+
   private static void throwGlException(String errorMsg) {
     Log.e(TAG, errorMsg);
     if (glAssertionsEnabled) {
@@ -555,6 +424,178 @@ public final class GlUtil {
     return strVal.length;
   }
 
+  /**
+   * GL attribute, which can be attached to a buffer with {@link Attribute#setBuffer(float[], int)}.
+   */
+  private static final class Attribute {
+
+    /* Returns the attribute at the given index in the program. */
+    public static Attribute create(int programId, int index) {
+      int[] length = new int[1];
+      GLES20.glGetProgramiv(programId, GLES20.GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, length, 0);
+
+      int[] type = new int[1];
+      int[] size = new int[1];
+      byte[] nameBytes = new byte[length[0]];
+      int[] ignore = new int[1];
+
+      GLES20.glGetActiveAttrib(
+          programId, index, length[0], ignore, 0, size, 0, type, 0, nameBytes, 0);
+      String name = new String(nameBytes, 0, strlen(nameBytes));
+      int location = getAttributeLocation(programId, name);
+
+      return new Attribute(name, index, location);
+    }
+
+    /** The name of the attribute in the GLSL sources. */
+    public final String name;
+
+    private final int index;
+    private final int location;
+
+    @Nullable private Buffer buffer;
+    private int size;
+
+    private Attribute(String name, int index, int location) {
+      this.name = name;
+      this.index = index;
+      this.location = location;
+    }
+
+    /**
+     * Configures {@link #bind()} to attach vertices in {@code buffer} (each of size {@code size}
+     * elements) to this {@link Attribute}.
+     *
+     * @param buffer Buffer to bind to this attribute.
+     * @param size Number of elements per vertex.
+     */
+    public void setBuffer(float[] buffer, int size) {
+      this.buffer = createBuffer(buffer);
+      this.size = size;
+    }
+
+    /**
+     * Sets the vertex attribute to whatever was attached via {@link #setBuffer(float[], int)}.
+     *
+     * <p>Should be called before each drawing call.
+     */
+    public void bind() {
+      Buffer buffer = checkNotNull(this.buffer, "call setBuffer before bind");
+      GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0);
+      GLES20.glVertexAttribPointer(
+          location,
+          size, // count
+          GLES20.GL_FLOAT, // type
+          false, // normalize
+          0, // stride
+          buffer);
+      GLES20.glEnableVertexAttribArray(index);
+      checkGlError();
+    }
+  }
+
+  /**
+   * GL uniform, which can be attached to a sampler using {@link Uniform#setSamplerTexId(int, int)}.
+   */
+  private static final class Uniform {
+
+    /** Returns the uniform at the given index in the program. */
+    public static Uniform create(int programId, int index) {
+      int[] length = new int[1];
+      GLES20.glGetProgramiv(programId, GLES20.GL_ACTIVE_UNIFORM_MAX_LENGTH, length, 0);
+
+      int[] type = new int[1];
+      int[] size = new int[1];
+      byte[] nameBytes = new byte[length[0]];
+      int[] ignore = new int[1];
+
+      GLES20.glGetActiveUniform(
+          programId, index, length[0], ignore, 0, size, 0, type, 0, nameBytes, 0);
+      String name = new String(nameBytes, 0, strlen(nameBytes));
+      int location = getUniformLocation(programId, name);
+
+      return new Uniform(name, location, type[0]);
+    }
+
+    /** The name of the uniform in the GLSL sources. */
+    public final String name;
+
+    private final int location;
+    private final int type;
+    private final float[] value;
+
+    private int texId;
+    private int unit;
+
+    private Uniform(String name, int location, int type) {
+      this.name = name;
+      this.location = location;
+      this.type = type;
+      this.value = new float[16];
+    }
+
+    /**
+     * Configures {@link #bind()} to use the specified {@code texId} for this sampler uniform.
+     *
+     * @param texId The GL texture identifier from which to sample.
+     * @param unit The GL texture unit index.
+     */
+    public void setSamplerTexId(int texId, int unit) {
+      this.texId = texId;
+      this.unit = unit;
+    }
+
+    /** Configures {@link #bind()} to use the specified float {@code value} for this uniform. */
+    public void setFloat(float value) {
+      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)}, {@link
+     * #setFloat(float)} or {@link #setFloats(float[])}.
+     *
+     * <p>Should be called before each drawing call.
+     */
+    public void bind() {
+      if (type == GLES20.GL_FLOAT) {
+        GLES20.glUniform1fv(location, 1, value, 0);
+        checkGlError();
+        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.");
+      }
+      GLES20.glActiveTexture(GLES20.GL_TEXTURE0 + unit);
+      if (type == GLES11Ext.GL_SAMPLER_EXTERNAL_OES) {
+        GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texId);
+      } else if (type == GLES20.GL_SAMPLER_2D) {
+        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texId);
+      } else {
+        throw new IllegalStateException("Unexpected uniform type: " + type);
+      }
+      GLES20.glUniform1i(location, unit);
+      GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);
+      GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR);
+      GLES20.glTexParameteri(
+          GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE);
+      GLES20.glTexParameteri(
+          GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE);
+      checkGlError();
+    }
+  }
+
   @RequiresApi(17)
   private static final class Api17 {
     private Api17() {}

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/video/spherical/ProjectionRenderer.java

@@ -114,7 +114,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   }
 
   /** Initializes of the GL components. */
-  /* package */ void init() {
+  public void init() {
     program = new GlUtil.Program(VERTEX_SHADER, FRAGMENT_SHADER);
     mvpMatrixHandle = program.getUniformLocation("uMvpMatrix");
     uTexMatrixHandle = program.getUniformLocation("uTexMatrix");
@@ -132,7 +132,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
    * @param rightEye Whether the right eye view should be drawn. If {@code false}, the left eye view
    *     is drawn.
    */
-  /* package */ void draw(int textureId, float[] mvpMatrix, boolean rightEye) {
+  public void draw(int textureId, float[] mvpMatrix, boolean rightEye) {
     MeshData meshData = rightEye ? rightMeshData : leftMeshData;
     if (meshData == null) {
       return;
@@ -188,7 +188,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   }
 
   /** Cleans up GL resources. */
-  /* package */ void shutdown() {
+  public void shutdown() {
     if (program != null) {
       program.delete();
     }

libraries/transformer/src/main/java/androidx/media3/transformer/OpenGlFrameEditor.java

@@ -13,12 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package androidx.media3.transformer;
 
-import static androidx.media3.common.util.Assertions.checkNotNull;
-import static androidx.media3.common.util.Assertions.checkState;
-
 import android.content.Context;
 import android.graphics.SurfaceTexture;
 import android.opengl.EGL14;
@@ -31,7 +27,6 @@ import android.view.Surface;
 import androidx.annotation.RequiresApi;
 import androidx.media3.common.util.GlUtil;
 import java.io.IOException;
-import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 /**
  * OpenGlFrameEditor applies changes to individual video frames using OpenGL. Changes include just
@@ -67,73 +62,38 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     int textureId = GlUtil.createExternalTexture();
     GlUtil.Program copyProgram;
     try {
+      // TODO(internal b/205002913): check the loaded program is consistent with the attributes
+      // and uniforms expected in the code.
       copyProgram = new GlUtil.Program(context, VERTEX_SHADER_FILE_PATH, FRAGMENT_SHADER_FILE_PATH);
     } catch (IOException e) {
       throw new IllegalStateException(e);
     }
-
+    copyProgram.setBufferAttribute(
-    copyProgram.use();
+        "a_position",
-    GlUtil.Attribute[] copyAttributes = copyProgram.getAttributes();
+        new float[] {
-    checkState(
+          -1.0f, -1.0f, 0.0f, 1.0f,
-        copyAttributes.length == EXPECTED_NUMBER_OF_ATTRIBUTES,
+          1.0f, -1.0f, 0.0f, 1.0f,
-        "Expected program to have " + EXPECTED_NUMBER_OF_ATTRIBUTES + " vertex attributes.");
+          -1.0f, 1.0f, 0.0f, 1.0f,
-    for (GlUtil.Attribute copyAttribute : copyAttributes) {
+          1.0f, 1.0f, 0.0f, 1.0f,
-      if (copyAttribute.name.equals("a_position")) {
+        },
-        copyAttribute.setBuffer(
+        /* size= */ 4);
-            new float[] {
+    copyProgram.setBufferAttribute(
-              -1.0f, -1.0f, 0.0f, 1.0f,
+        "a_texcoord",
-              1.0f, -1.0f, 0.0f, 1.0f,
+        new float[] {
-              -1.0f, 1.0f, 0.0f, 1.0f,
+          0.0f, 0.0f, 0.0f, 1.0f,
-              1.0f, 1.0f, 0.0f, 1.0f,
+          1.0f, 0.0f, 0.0f, 1.0f,
-            },
+          0.0f, 1.0f, 0.0f, 1.0f,
-            /* size= */ 4);
+          1.0f, 1.0f, 0.0f, 1.0f,
-      } else if (copyAttribute.name.equals("a_texcoord")) {
+        },
-        copyAttribute.setBuffer(
+        /* size= */ 4);
-            new float[] {
+    copyProgram.setSamplerTexIdUniform("tex_sampler", textureId, /* unit= */ 0);
-              0.0f, 0.0f, 0.0f, 1.0f,
+    return new OpenGlFrameEditor(eglDisplay, eglContext, eglSurface, textureId, copyProgram);
-              1.0f, 0.0f, 0.0f, 1.0f,
-              0.0f, 1.0f, 0.0f, 1.0f,
-              1.0f, 1.0f, 0.0f, 1.0f,
-            },
-            /* size= */ 4);
-      } else {
-        throw new IllegalStateException("Unexpected attribute name.");
-      }
-      copyAttribute.bind();
-    }
-    GlUtil.Uniform[] copyUniforms = copyProgram.getUniforms();
-    checkState(
-        copyUniforms.length == EXPECTED_NUMBER_OF_UNIFORMS,
-        "Expected program to have " + EXPECTED_NUMBER_OF_UNIFORMS + " uniforms.");
-    GlUtil.@MonotonicNonNull Uniform textureTransformUniform = null;
-    for (GlUtil.Uniform copyUniform : copyUniforms) {
-      if (copyUniform.name.equals("tex_sampler")) {
-        copyUniform.setSamplerTexId(textureId, 0);
-        copyUniform.bind();
-      } else if (copyUniform.name.equals("tex_transform")) {
-        textureTransformUniform = copyUniform;
-      } else {
-        throw new IllegalStateException("Unexpected uniform name.");
-      }
-    }
-
-    return new OpenGlFrameEditor(
-        eglDisplay,
-        eglContext,
-        eglSurface,
-        textureId,
-        checkNotNull(textureTransformUniform),
-        copyProgram,
-        copyAttributes,
-        copyUniforms);
   }
 
   // Predefined shader values.
   private static final String VERTEX_SHADER_FILE_PATH = "shaders/blit_vertex_shader.glsl";
   private static final String FRAGMENT_SHADER_FILE_PATH =
       "shaders/copy_external_fragment_shader.glsl";
-  private static final int EXPECTED_NUMBER_OF_ATTRIBUTES = 2;
-  private static final int EXPECTED_NUMBER_OF_UNIFORMS = 2;
 
   private final float[] textureTransformMatrix;
   private final EGLDisplay eglDisplay;
@@ -142,19 +102,9 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   private final int textureId;
   private final SurfaceTexture inputSurfaceTexture;
   private final Surface inputSurface;
-  private final GlUtil.Uniform textureTransformUniform;
 
-  // TODO(internal: b/206631334): These fields ensure buffers passed to GL are not GC'ed. Implement
-  // a better way of doing this so they aren't just unused fields.
-  @SuppressWarnings("unused")
   private final GlUtil.Program copyProgram;
 
-  @SuppressWarnings("unused")
-  private final GlUtil.Attribute[] copyAttributes;
-
-  @SuppressWarnings("unused")
-  private final GlUtil.Uniform[] copyUniforms;
-
   private volatile boolean hasInputData;
 
   private OpenGlFrameEditor(
@@ -162,38 +112,37 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
       EGLContext eglContext,
       EGLSurface eglSurface,
       int textureId,
-      GlUtil.Uniform textureTransformUniform,
+      GlUtil.Program copyProgram) {
-      GlUtil.Program copyProgram,
-      GlUtil.Attribute[] copyAttributes,
-      GlUtil.Uniform[] copyUniforms) {
     this.eglDisplay = eglDisplay;
     this.eglContext = eglContext;
     this.eglSurface = eglSurface;
     this.textureId = textureId;
-    this.textureTransformUniform = textureTransformUniform;
     this.copyProgram = copyProgram;
-    this.copyAttributes = copyAttributes;
-    this.copyUniforms = copyUniforms;
     textureTransformMatrix = new float[16];
     inputSurfaceTexture = new SurfaceTexture(textureId);
     inputSurfaceTexture.setOnFrameAvailableListener(surfaceTexture -> hasInputData = true);
     inputSurface = new Surface(inputSurfaceTexture);
   }
 
-  /** Releases all resources. */
+  /** Returns the input {@link Surface}. */
-  public void release() {
+  public Surface getInputSurface() {
-    GlUtil.destroyEglContext(eglDisplay, eglContext);
+    return inputSurface;
-    GlUtil.deleteTexture(textureId);
-    inputSurfaceTexture.release();
-    inputSurface.release();
   }
 
-  /** Informs the editor that there is new input data available for it to process asynchronously. */
+  /**
+   * Returns whether there is pending input data that can be processed by calling {@link
+   * #processData()}.
+   */
+  public boolean hasInputData() {
+    return hasInputData;
+  }
+
+  /** Processes pending input data. */
   public void processData() {
     inputSurfaceTexture.updateTexImage();
     inputSurfaceTexture.getTransformMatrix(textureTransformMatrix);
-    textureTransformUniform.setFloats(textureTransformMatrix);
+    copyProgram.setFloatsUniform("tex_transform", textureTransformMatrix);
-    textureTransformUniform.bind();
+    copyProgram.bindAttributesAndUniforms();
     GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);
     long surfaceTextureTimestampNs = inputSurfaceTexture.getTimestamp();
     EGLExt.eglPresentationTimeANDROID(eglDisplay, eglSurface, surfaceTextureTimestampNs);
@@ -201,15 +150,12 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     hasInputData = false;
   }
 
-  /**
+  /** Releases all resources. */
-   * Returns the input {@link Surface} after configuring the editor if it has not previously been
+  public void release() {
-   * configured.
+    copyProgram.delete();
-   */
+    GlUtil.deleteTexture(textureId);
-  public Surface getInputSurface() {
+    GlUtil.destroyEglContext(eglDisplay, eglContext);
-    return inputSurface;
+    inputSurfaceTexture.release();
-  }
+    inputSurface.release();
-
-  public boolean hasInputData() {
-    return hasInputData;
   }
 }