Fast snapshot with new GL preview. Take snapshots while taking video

MIGRATION.md

@@ -32,7 +32,7 @@
 - VideoSizeSelector: added. It is needed to choose the capture size in VIDEO mode.
   Defaults to SizeSelectors.biggest(), but you can choose by aspect ratio or whatever.
 - isTakingPicture(): added on top of isTakingVideo().
-- takeVideoSnapshot(): new api. Requires the experimental flag, API 18 or it will throw.
+- takeVideoSnapshot(): new api. API 18 and the Gl preview, or it will throw.
   Respects orientation, videocodec and max duration limit.
   Automatically rotates the data. Automatically crops the video.
   NO audio support.
@@ -41,10 +41,11 @@
   The default is GlSurfaceView and it is highly recommended that you do not change this.
 - New pictureRecorder interface for picture capturing.
 - Created FullPictureRecorder and SnapshotPictureRecorder for capturing HQ pictures and snapshots.
+- When preview is GlSurface, the SnapshotPictureRecorder will use the gl texture and draw it into JPEG.
+  This is really fast and allows us to avoid RotationHelper, creating bitmap copies, OOMs, EXIF stuff.
+- When preview is GlSurface, you can take snapshots while recording video (or video snapshots!).
+  TODO: document this
+- TODO: cameraPreview documentation    
+- TODO: takeVideoSnapshot documentation
 
-TODO: cameraPreview documentation    
+TODO: add audio to the video snapshots
-TODO: takeVideoSnapshot documentation
-
-TODO: add audio to the video snapshots
-TODO: improve SnapshotPictureRecorder so that, if preview is GL, we catch the preview through GLES drawing
-      this would finally remove the RotationHelper and OOMs!

cameraview/src/main/gles/com/otaliastudios/cameraview/EglBaseSurface.java

@@ -25,6 +25,7 @@ import android.support.annotation.RequiresApi;
 import android.util.Log;
 
 import java.io.BufferedOutputStream;
+import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
@@ -157,7 +158,7 @@ class EglBaseSurface extends EglElement {
      * <p>
      * Expects that this object's EGL surface is current.
      */
-    public void saveFrame(File file) throws IOException {
+    public void saveFrameToFile(File file) throws IOException {
         if (!mEglCore.isCurrent(mEGLSurface)) {
             throw new RuntimeException("Expected EGL context/surface is not current");
         }
@@ -196,4 +197,42 @@ class EglBaseSurface extends EglElement {
             if (bos != null) bos.close();
         }
     }
+
+    /**
+     * Saves the EGL surface to jpeg.
+     * <p>
+     * Expects that this object's EGL surface is current.
+     */
+    public byte[] saveFrameToJpeg() {
+        if (!mEglCore.isCurrent(mEGLSurface)) {
+            throw new RuntimeException("Expected EGL context/surface is not current");
+        }
+
+        // glReadPixels fills in a "direct" ByteBuffer with what is essentially big-endian RGBA
+        // data (i.e. a byte of red, followed by a byte of green...).  While the Bitmap
+        // constructor that takes an int[] wants little-endian ARGB (blue/red swapped), the
+        // Bitmap "copy pixels" method wants the same format GL provides.
+        //
+        // Ideally we'd have some way to re-use the ByteBuffer, especially if we're calling
+        // here often.
+        //
+        // Making this even more interesting is the upside-down nature of GL, which means
+        // our output will look upside down relative to what appears on screen if the
+        // typical GL conventions are used.
+
+        int width = getWidth();
+        int height = getHeight();
+        ByteBuffer buf = ByteBuffer.allocateDirect(width * height * 4);
+        buf.order(ByteOrder.LITTLE_ENDIAN);
+        GLES20.glReadPixels(0, 0, width, height, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, buf);
+        check("glReadPixels");
+        buf.rewind();
+
+        ByteArrayOutputStream bos = new ByteArrayOutputStream(buf.array().length);
+        Bitmap bmp = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+        bmp.copyPixelsFromBuffer(buf);
+        bmp.compress(Bitmap.CompressFormat.JPEG, 90, bos);
+        bmp.recycle();
+        return bos.toByteArray();
+    }
 }

cameraview/src/main/gles/com/otaliastudios/cameraview/EglCore.java

@@ -28,6 +28,8 @@ import android.support.annotation.RequiresApi;
 import android.util.Log;
 import android.view.Surface;
 
+import javax.microedition.khronos.egl.EGL10;
+
 /**
  * -- from grafika --
  *

cameraview/src/main/gles/com/otaliastudios/cameraview/EglViewport.java

@@ -56,20 +56,21 @@ class EglViewport extends EglElement {
     };
 
     // Stuff from Drawable2d.FULL_RECTANGLE
-    private FloatBuffer mVertexArray = floatBuffer(FULL_RECTANGLE_COORDS);
+    private FloatBuffer mVertexCoordinatesArray = floatBuffer(FULL_RECTANGLE_COORDS);
-    private FloatBuffer mTexCoordArray = floatBuffer(FULL_RECTANGLE_TEX_COORDS);
+    private FloatBuffer mTextureCoordinatesArray = floatBuffer(FULL_RECTANGLE_TEX_COORDS);
     private int mVertexCount = FULL_RECTANGLE_COORDS.length / 2;
-    private final int mCoordsPerVertex = 2;
+    private final int mCoordinatesPerVertex = 2;
     private final int mVertexStride = 8;
-    private final int mTexCoordStride = 8;
+    private final int mTextureStride = 8;
 
     // Stuff from Texture2dProgram
     private int mProgramHandle;
     private int mTextureTarget;
-    private int muMVPMatrixLoc;
+    // Program attributes
-    private int muTexMatrixLoc;
+    private int muMVPMatrixLocation;
-    private int maPositionLoc;
+    private int muTexMatrixLocation;
-    private int maTextureCoordLoc;
+    private int maPositionLocation;
+    private int maTextureCoordLocation;
 
     // private int muKernelLoc; // Used for filtering
     // private int muTexOffsetLoc; // Used for filtering
@@ -78,14 +79,14 @@ class EglViewport extends EglElement {
     EglViewport() {
         mTextureTarget = GLES11Ext.GL_TEXTURE_EXTERNAL_OES;
         mProgramHandle = createProgram(SIMPLE_VERTEX_SHADER, SIMPLE_FRAGMENT_SHADER);
-        maPositionLoc = GLES20.glGetAttribLocation(mProgramHandle, "aPosition");
+        maPositionLocation = GLES20.glGetAttribLocation(mProgramHandle, "aPosition");
-        checkLocation(maPositionLoc, "aPosition");
+        checkLocation(maPositionLocation, "aPosition");
-        maTextureCoordLoc = GLES20.glGetAttribLocation(mProgramHandle, "aTextureCoord");
+        maTextureCoordLocation = GLES20.glGetAttribLocation(mProgramHandle, "aTextureCoord");
-        checkLocation(maTextureCoordLoc, "aTextureCoord");
+        checkLocation(maTextureCoordLocation, "aTextureCoord");
-        muMVPMatrixLoc = GLES20.glGetUniformLocation(mProgramHandle, "uMVPMatrix");
+        muMVPMatrixLocation = GLES20.glGetUniformLocation(mProgramHandle, "uMVPMatrix");
-        checkLocation(muMVPMatrixLoc, "uMVPMatrix");
+        checkLocation(muMVPMatrixLocation, "uMVPMatrix");
-        muTexMatrixLoc = GLES20.glGetUniformLocation(mProgramHandle, "uTexMatrix");
+        muTexMatrixLocation = GLES20.glGetUniformLocation(mProgramHandle, "uTexMatrix");
-        checkLocation(muTexMatrixLoc, "uTexMatrix");
+        checkLocation(muTexMatrixLocation, "uTexMatrix");
 
         // Stuff from Drawable2d.FULL_RECTANGLE
 
@@ -122,15 +123,15 @@ class EglViewport extends EglElement {
         return texId;
     }
 
-    void drawFrame(int textureId, float[] texMatrix) {
+    void drawFrame(int textureId, float[] textureMatrix) {
-        drawFrame(textureId, texMatrix,
+        drawFrame(textureId, textureMatrix,
-                IDENTITY_MATRIX, mVertexArray, 0,
+                IDENTITY_MATRIX, mVertexCoordinatesArray, 0,
-                mVertexCount, mCoordsPerVertex,
+                mVertexCount, mCoordinatesPerVertex,
-                mVertexStride, mTexCoordArray,
+                mVertexStride, mTextureCoordinatesArray,
-                mTexCoordStride);
+                mTextureStride);
     }
 
-    private void drawFrame(int textureId, float[] texMatrix,
+    private void drawFrame(int textureId, float[] textureMatrix,
                           float[] mvpMatrix, FloatBuffer vertexBuffer, int firstVertex,
                           int vertexCount, int coordsPerVertex, int vertexStride,
                           FloatBuffer texBuffer, int texStride) {
@@ -145,28 +146,28 @@ class EglViewport extends EglElement {
         GLES20.glBindTexture(mTextureTarget, textureId);
 
         // Copy the model / view / projection matrix over.
-        GLES20.glUniformMatrix4fv(muMVPMatrixLoc, 1, false, mvpMatrix, 0);
+        GLES20.glUniformMatrix4fv(muMVPMatrixLocation, 1, false, mvpMatrix, 0);
         check("glUniformMatrix4fv");
 
         // Copy the texture transformation matrix over.
-        GLES20.glUniformMatrix4fv(muTexMatrixLoc, 1, false, texMatrix, 0);
+        GLES20.glUniformMatrix4fv(muTexMatrixLocation, 1, false, textureMatrix, 0);
         check("glUniformMatrix4fv");
 
         // Enable the "aPosition" vertex attribute.
-        GLES20.glEnableVertexAttribArray(maPositionLoc);
+        GLES20.glEnableVertexAttribArray(maPositionLocation);
         check("glEnableVertexAttribArray");
 
         // Connect vertexBuffer to "aPosition".
-        GLES20.glVertexAttribPointer(maPositionLoc, coordsPerVertex,
+        GLES20.glVertexAttribPointer(maPositionLocation, coordsPerVertex,
                 GLES20.GL_FLOAT, false, vertexStride, vertexBuffer);
         check("glVertexAttribPointer");
 
         // Enable the "aTextureCoord" vertex attribute.
-        GLES20.glEnableVertexAttribArray(maTextureCoordLoc);
+        GLES20.glEnableVertexAttribArray(maTextureCoordLocation);
         check("glEnableVertexAttribArray");
 
         // Connect texBuffer to "aTextureCoord".
-        GLES20.glVertexAttribPointer(maTextureCoordLoc, 2,
+        GLES20.glVertexAttribPointer(maTextureCoordLocation, 2,
                 GLES20.GL_FLOAT, false, texStride, texBuffer);
         check("glVertexAttribPointer");
 
@@ -175,8 +176,8 @@ class EglViewport extends EglElement {
         check("glDrawArrays");
 
         // Done -- disable vertex array, texture, and program.
-        GLES20.glDisableVertexAttribArray(maPositionLoc);
+        GLES20.glDisableVertexAttribArray(maPositionLocation);
-        GLES20.glDisableVertexAttribArray(maTextureCoordLoc);
+        GLES20.glDisableVertexAttribArray(maTextureCoordLocation);
         GLES20.glBindTexture(mTextureTarget, 0);
         GLES20.glUseProgram(0);
     }

cameraview/src/main/gles/com/otaliastudios/cameraview/EglWindowSurface.java

@@ -54,6 +54,14 @@ class EglWindowSurface extends EglBaseSurface {
         createWindowSurface(surfaceTexture);
     }
 
+    /**
+     * Associates an EGL surface with the Surface.
+     */
+    public EglWindowSurface(EglCore eglCore, Surface surface) {
+        super(eglCore);
+        createWindowSurface(surface);
+    }
+
     /**
      * Releases any resources associated with the EGL surface (and, if configured to do so,
      * with the Surface as well).

cameraview/src/main/gles/com/otaliastudios/cameraview/VideoTextureEncoder.java

@@ -157,7 +157,7 @@ class VideoTextureEncoder implements Runnable {
             mInputWindowSurface = null;
         }
         if (mFullScreen != null) {
-            mFullScreen.release(false);
+            mFullScreen.release(true);
             mFullScreen = null;
         }
         if (mEglCore != null) {

cameraview/src/main/java/com/otaliastudios/cameraview/Camera1.java

@@ -527,6 +527,8 @@ class Camera1 extends CameraController implements Camera.PreviewCallback, Camera
             @Override
             public void run() {
                 if (mMode == Mode.VIDEO) {
+                    // Could redirect to takePictureSnapshot, but it's better if people know
+                    // what they are doing.
                     throw new IllegalStateException("Can't take hq pictures while in VIDEO mode");
                 }
 
@@ -550,11 +552,6 @@ class Camera1 extends CameraController implements Camera.PreviewCallback, Camera
         schedule(null, true, new Runnable() {
             @Override
             public void run() {
-                if (isTakingVideo()) {
-                    // TODO v2: what to do here?
-                    return;
-                }
-
                 LOG.v("takePictureSnapshot: performing.", isTakingPicture());
                 if (isTakingPicture()) return;
 

cameraview/src/main/java/com/otaliastudios/cameraview/SnapshotPictureRecorder.java

@@ -1,12 +1,27 @@
 package com.otaliastudios.cameraview;
 
+import android.annotation.SuppressLint;
+import android.graphics.Bitmap;
 import android.graphics.ImageFormat;
 import android.graphics.Rect;
+import android.graphics.SurfaceTexture;
 import android.graphics.YuvImage;
 import android.hardware.Camera;
+import android.opengl.EGL14;
+import android.opengl.EGLContext;
+import android.opengl.EGLDisplay;
+import android.opengl.EGLSurface;
+import android.opengl.GLES11Ext;
+import android.opengl.GLES20;
 import android.opengl.GLSurfaceView;
+import android.opengl.Matrix;
+import android.view.Surface;
+import android.view.SurfaceHolder;
+import android.view.SurfaceView;
 
 import java.io.ByteArrayOutputStream;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 
 /**
  * A {@link PictureResult} that uses standard APIs.
@@ -23,12 +38,12 @@ class SnapshotPictureRecorder extends PictureRecorder {
     private Size mSensorPreviewSize;
     private int mFormat;
 
-    SnapshotPictureRecorder(PictureResult stub, Camera1 controller, Camera camera, AspectRatio viewRatio) {
+    SnapshotPictureRecorder(PictureResult stub, Camera1 controller, Camera camera, AspectRatio outputRatio) {
         super(stub, controller);
         mController = controller;
         mPreview = controller.mPreview;
         mCamera = camera;
-        mOutputRatio = viewRatio;
+        mOutputRatio = outputRatio;
         mFormat = mController.mPreviewFormat;
         mSensorPreviewSize = mController.mPreviewSize;
     }
@@ -42,11 +57,94 @@ class SnapshotPictureRecorder extends PictureRecorder {
         }
     }
 
-    private void takeGl(GLCameraPreview preview) {
+    @SuppressLint("NewApi")
-        // TODO implement.
+    private void takeGl(final GLCameraPreview preview) {
-        takeLegacy();
+        preview.addRendererFrameCallback(new GLCameraPreview.RendererFrameCallback() {
+
+            int mTextureId;
+            SurfaceTexture mSurfaceTexture;
+            float[] mTransform;
+
+            public void onRendererTextureCreated(int textureId) {
+                mTextureId = textureId;
+                mSurfaceTexture = new SurfaceTexture(mTextureId, true);
+                // Need to crop the size.
+                Rect crop = CropHelper.computeCrop(mResult.size, mOutputRatio);
+                mResult.size = new Size(crop.width(), crop.height());
+                mSurfaceTexture.setDefaultBufferSize(mResult.size.getWidth(), mResult.size.getHeight());
+                mTransform = new float[16];
+            }
+
+            @Override
+            public void onRendererFrame(SurfaceTexture surfaceTexture, final float scaleX, final float scaleY) {
+                preview.removeRendererFrameCallback(this);
+
+                // This kinda work but has drawbacks:
+                // - output is upside down due to coordinates in GL: need to flip the byte[] someway
+                // - output is not rotated as we would like to: need to create a bitmap copy...
+                // - works only in the renderer thread, where it allocates the buffer and reads pixels. Bad!
+                /*
+                ByteBuffer buffer = ByteBuffer.allocateDirect(width * height * 4);
+                buffer.order(ByteOrder.LITTLE_ENDIAN);
+                GLES20.glReadPixels(0, 0, width, height, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, buffer);
+                buffer.rewind();
+                ByteArrayOutputStream bos = new ByteArrayOutputStream(buffer.array().length);
+                Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
+                bitmap.copyPixelsFromBuffer(buffer);
+                bitmap.compress(Bitmap.CompressFormat.JPEG, 90, bos);
+                bitmap.recycle(); */
+
+                // For this reason it is better to create a new surface,
+                // and draw the last frame again there.
+                final EGLContext eglContext = EGL14.eglGetCurrentContext();
+                final EglCore core = new EglCore(eglContext, EglCore.FLAG_RECORDABLE);
+                // final EGLSurface oldSurface = EGL14.eglGetCurrentSurface(EGL14.EGL_DRAW);
+                // final EGLDisplay oldDisplay = EGL14.eglGetCurrentDisplay();
+                WorkerHandler.run(new Runnable() {
+                    @Override
+                    public void run() {
+                        EglWindowSurface surface = new EglWindowSurface(core, mSurfaceTexture);
+                        surface.makeCurrent();
+                        EglViewport viewport = new EglViewport();
+                        mSurfaceTexture.updateTexImage();
+                        mSurfaceTexture.getTransformMatrix(mTransform);
+
+                        // Apply scale and crop:
+                        // NOTE: scaleX and scaleY are in REF_VIEW, while our input appears to be in REF_SENSOR.
+                        boolean flip = mController.flip(CameraController.REF_VIEW, CameraController.REF_SENSOR);
+                        float realScaleX = flip ? scaleY : scaleX;
+                        float realScaleY = flip ? scaleX : scaleY;
+                        float scaleTranslX = (1F - realScaleX) / 2F;
+                        float scaleTranslY = (1F - realScaleY) / 2F;
+                        Matrix.translateM(mTransform, 0, scaleTranslX, scaleTranslY, 0);
+                        Matrix.scaleM(mTransform, 0, realScaleX, realScaleY, 1);
+
+                        // Apply rotation:
+                        // Not sure why we need the minus here... It makes no sense.
+                        int rotation = -mResult.rotation;
+                        mResult.rotation = 0;
+                        Matrix.translateM(mTransform, 0, 0.5F, 0.5F, 0);
+                        Matrix.rotateM(mTransform, 0, rotation, 0, 0, 1);
+                        Matrix.translateM(mTransform, 0, -0.5F, -0.5F, 0);
+
+                        viewport.drawFrame(mTextureId, mTransform);
+                        // don't - surface.swapBuffers();
+                        mResult.jpeg = surface.saveFrameToJpeg();
+                        mSurfaceTexture.releaseTexImage();
+
+                        // EGL14.eglMakeCurrent(oldDisplay, oldSurface, oldSurface, eglContext);
+                        surface.release();
+                        viewport.release();
+                        mSurfaceTexture.release();
+                        core.release();
+                        dispatchResult();
+                    }
+                });
+            }
+        });
     }
 
+
     private void takeLegacy() {
         mCamera.setOneShotPreviewCallback(new Camera.PreviewCallback() {
             @Override

cameraview/src/main/java/com/otaliastudios/cameraview/SnapshotVideoRecorder.java

@@ -33,7 +33,7 @@ class SnapshotVideoRecorder extends VideoRecorder implements GLCameraPreview.Ren
         super(stub, listener);
         mEncoder = new VideoTextureEncoder();
         mPreview = preview;
-        mPreview.setRendererFrameCallback(this);
+        mPreview.addRendererFrameCallback(this);
     }
 
     @Override
@@ -109,7 +109,7 @@ class SnapshotVideoRecorder extends VideoRecorder implements GLCameraPreview.Ren
             mCurrentState = STATE_NOT_RECORDING;
 
             mEncoder = null;
-            mPreview.setRendererFrameCallback(null);
+            mPreview.removeRendererFrameCallback(SnapshotVideoRecorder.this);
             mPreview = null;
         }
 

cameraview/src/main/options/com/otaliastudios/cameraview/Preview.java

@@ -16,13 +16,15 @@ public enum Preview implements Control {
 
     /**
      * Preview engine based on {@link android.view.TextureView}.
-     * Stable, but does not support all features (like video snapshots).
+     * Stable, but does not support all features (like video snapshots,
+     * or picture snapshot while taking videos).
      */
     TEXTURE(1),
 
     /**
      * Preview engine based on {@link android.opengl.GLSurfaceView}.
-     * This is the best engine available.
+     * This is the best engine available. Supports video snapshots,
+     * and picture snapshots while taking videos.
      */
     GL_SURFACE(2);
 

cameraview/src/main/views/com/otaliastudios/cameraview/GLCameraPreview.java

@@ -11,7 +11,14 @@ import android.view.SurfaceHolder;
 import android.view.View;
 import android.view.ViewGroup;
 
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+
+import javax.microedition.khronos.egl.EGL10;
 import javax.microedition.khronos.egl.EGLConfig;
+import javax.microedition.khronos.egl.EGLDisplay;
+import javax.microedition.khronos.egl.EGLSurface;
 import javax.microedition.khronos.opengles.GL10;
 
 /**
@@ -19,42 +26,43 @@ import javax.microedition.khronos.opengles.GL10;
  *
  * - in the SurfaceTexture constructor we pass the GL texture handle that we have created.
  *
- * - The SurfaceTexture is linked to the Camera1 object. It will pass down buffers of data with
+ * - The SurfaceTexture is linked to the Camera1 object. The camera will pass down buffers of data with
- *   a specified size (that is, the Camera1 preview size).
+ *   a specified size (that is, the Camera1 preview size). For this reason we don't have to specify
- *
+ *   surfaceTexture.setDefaultBufferSize() (like we do, for example, in SnapshotPictureRecorder).
- * - When SurfaceTexture.updateTexImage() is called, it will take the latest image from the camera stream
- *   and update it into the GL texture that was passed.
  *
- * - Now we have a GL texture referencing data. It must be drawn.
+ * - When SurfaceTexture.updateTexImage() is called, it will fetch the latest texture image from the
- *  [Note: it must be drawn using a transformation matrix taken from SurfaceTexture]
+ *   camera stream and assign it to the GL texture that was passed.
+ *   Now the GL texture must be drawn using draw* APIs. The SurfaceTexture will also give us
+ *   the transformation matrix to be applied.
  *
  * - The easy way to render an OpenGL texture is using the {@link GLSurfaceView} class.
- *   It manages the gl context, hosts a surface and runs a separated rendering thread that will perform
+ *   It manages the GL context, hosts a surface and runs a separated rendering thread that will perform
  *   the rendering.
  *
  * - As per docs, we ask the GLSurfaceView to delegate rendering to us, using
  *   {@link GLSurfaceView#setRenderer(GLSurfaceView.Renderer)}. We request a render on the SurfaceView
  *   anytime the SurfaceTexture notifies that it has new data available (see OnFrameAvailableListener below).
  *
- * - Everything is linked:
+ * - So in short:
  *   - The SurfaceTexture has buffers of data of mInputStreamSize
- *   - The SurfaceView hosts a view (and surface) of size mOutputSurfaceSize
+ *   - The SurfaceView hosts a view (and a surface) of size mOutputSurfaceSize.
+ *     These are determined by the CameraView.onMeasure method.
  *   - We have a GL rich texture to be drawn (in the given method & thread).
  *
- * TODO
+ * This class will provide rendering callbacks to anyone who registers a {@link RendererFrameCallback}.
- * CROPPING: Managed to do this using Matrix transformation.
+ * Callbacks are guaranteed to be called on the renderer thread, which means that we can fetch
- * UPDATING: Managed to work using view.onPause and onResume.
+ * the GL context that was created and is managed by the {@link GLSurfaceView}.
- * TAKING PICTURES: Sometime the snapshot takes ages... Can't reproduce anymore. Cool.
- * TAKING VIDEOS: Still have not tried...
  */
 class GLCameraPreview extends CameraPreview<GLSurfaceView, SurfaceTexture> implements GLSurfaceView.Renderer {
 
     private boolean mDispatched;
     private final float[] mTransformMatrix = new float[16];
-    private int mOutputTextureId = -1;
+    private int mOutputTextureId = 0;
     private SurfaceTexture mInputSurfaceTexture;
     private EglViewport mOutputViewport;
-    private RendererFrameCallback mRendererFrameCallback;
+    private Set<RendererFrameCallback> mRendererFrameCallbacks = Collections.synchronizedSet(new HashSet<RendererFrameCallback>());
+    /* for tests */ float mScaleX = 1F;
+    /* for tests */ float mScaleY = 1F;
 
     GLCameraPreview(Context context, ViewGroup parent, SurfaceCallback callback) {
         super(context, parent, callback);
@@ -97,10 +105,8 @@ class GLCameraPreview extends CameraPreview<GLSurfaceView, SurfaceTexture> imple
     @Override
     void onDestroy() {
         super.onDestroy();
-        releaseInputSurfaceTexture();
+        // View is gone, so EGL context is gone: callbacks make no sense anymore.
-    }
+        mRendererFrameCallbacks.clear();
-
-    private void releaseInputSurfaceTexture() {
         if (mInputSurfaceTexture != null) {
             mInputSurfaceTexture.setOnFrameAvailableListener(null);
             mInputSurfaceTexture.release();
@@ -113,28 +119,31 @@ class GLCameraPreview extends CameraPreview<GLSurfaceView, SurfaceTexture> imple
         }
     }
 
-    private void createInputSurfaceTexture() {
+    // Renderer thread
+    @Override
+    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
         mOutputViewport = new EglViewport();
         mOutputTextureId = mOutputViewport.createTexture();
         mInputSurfaceTexture = new SurfaceTexture(mOutputTextureId);
+        getView().queueEvent(new Runnable() {
+            @Override
+            public void run() {
+                for (RendererFrameCallback callback : mRendererFrameCallbacks) {
+                    callback.onRendererTextureCreated(mOutputTextureId);
+                }
+            }
+        });
 
         // Since we are using GLSurfaceView.RENDERMODE_WHEN_DIRTY, we must notify the SurfaceView
         // of dirtyness, so that it draws again. This is how it's done.
         mInputSurfaceTexture.setOnFrameAvailableListener(new SurfaceTexture.OnFrameAvailableListener() {
             @Override
             public void onFrameAvailable(SurfaceTexture surfaceTexture) {
-                // requestRender is thread-safe.
+                getView().requestRender(); // requestRender is thread-safe.
-                getView().requestRender();
             }
         });
     }
 
-    // Renderer thread
-    @Override
-    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
-        createInputSurfaceTexture();
-    }
-
     // Renderer thread
     @SuppressWarnings("StatementWithEmptyBody")
     @Override
@@ -143,27 +152,27 @@ class GLCameraPreview extends CameraPreview<GLSurfaceView, SurfaceTexture> imple
             dispatchOnOutputSurfaceAvailable(width, height);
             mDispatched = true;
         } else if (mOutputSurfaceWidth == width && mOutputSurfaceHeight == height) {
-                // This change can be triggered by ourselves (see below). Ignore.
+            // I was experimenting and this was happening.
+            // Not sure if it is stil needed now.
         } else {
             // With other CameraPreview implementation we could just dispatch the 'size changed' event
-            // to the controller and everything would go straight. In case of GL, apparently we have to:
+            // to the controller and everything would go straight. In case of GL, apparently we have to
-            // - create a new texture (release the old)
+            // force recreate the EGLContext by calling onPause and onResume in the UI thread.
-            // - unbind camera and surface
+            dispatchOnOutputSurfaceDestroyed();
-            // - stop camera preview
+            getView().post(new Runnable() {
-            // - recreate the GL context using view.onPause() and onResume()
+                @Override
-            // ...
+                public void run() {
-            onSizeChangeImplementation4(width, height);
+                    getView().onPause();
+                    getView().onResume();
+                    dispatchOnOutputSurfaceAvailable(width, height);
+                }
+            });
         }
     }
 
-
+    // Renderer thread
     @Override
     public void onDrawFrame(GL10 gl) {
-        // This are only needed with some implementations,
-        // and implementation4 seems to work well without them.
-        // if (mInputSurfaceTexture == null) return;
-        // if (mOutputViewport == null) return;
-
         // Latch the latest frame.  If there isn't anything new,
         // we'll just re-use whatever was there before.
         mInputSurfaceTexture.updateTexImage();
@@ -172,24 +181,21 @@ class GLCameraPreview extends CameraPreview<GLSurfaceView, SurfaceTexture> imple
             return;
         }
 
-        if (mRendererFrameCallback != null) {
-            mRendererFrameCallback.onRendererFrame(mInputSurfaceTexture, mScaleX, mScaleY);
-        }
-
-        // Draw the video frame.
         mInputSurfaceTexture.getTransformMatrix(mTransformMatrix);
         if (isCropping()) {
+            // Scaling is easy. However:
             // If the view is 10x1000 (very tall), it will show only the left strip of the preview (not the center one).
             // If the view is 1000x10 (very large), it will show only the bottom strip of the preview (not the center one).
-            // We must use Matrix.translateM, and it must happen before the crop.
+            // So we must use Matrix.translateM, and it must happen before the crop.
             float translX = (1F - mScaleX) / 2F;
             float translY = (1F - mScaleY) / 2F;
             Matrix.translateM(mTransformMatrix, 0, translX, translY, 0);
-
-            // Crop. Works, but without translation, it is not centered.
             Matrix.scaleM(mTransformMatrix, 0, mScaleX, mScaleY, 1);
         }
         mOutputViewport.drawFrame(mOutputTextureId, mTransformMatrix);
+        for (RendererFrameCallback callback : mRendererFrameCallbacks) {
+            callback.onRendererFrame(mInputSurfaceTexture, mScaleX, mScaleY);
+        }
     }
 
     @Override
@@ -207,9 +213,6 @@ class GLCameraPreview extends CameraPreview<GLSurfaceView, SurfaceTexture> imple
         return true;
     }
 
-    /* for tests */ float mScaleX = 1F;
-    /* for tests */ float mScaleY = 1F;
-
     /**
      * To crop in GL, we could actually use view.setScaleX and setScaleY, but only from Android N onward.
      * See documentation: https://developer.android.com/reference/android/view/SurfaceView
@@ -244,114 +247,39 @@ class GLCameraPreview extends CameraPreview<GLSurfaceView, SurfaceTexture> imple
         mCropTask.end(null);
     }
 
+    interface RendererFrameCallback {
 
-    // This does work but looks like a lot of stuff.
+        /**
-    private void onSizeChangeImplementation1(final int width, final int height) {
+         * Called on the renderer thread, hopefully only once, to notify that
-        releaseInputSurfaceTexture();
+         * the texture was created (or to inform a new callback of the old texture).
-        dispatchOnOutputSurfaceDestroyed();
+         *
-        getView().post(new Runnable() {
+         * @param textureId the GL texture linked to the image stream
-            @Override
+         */
-            public void run() {
+        void onRendererTextureCreated(int textureId);
-                getView().onPause();
-                getView().onResume();
-                getView().queueEvent(new Runnable() {
-                    @Override
-                    public void run() {
-                        createInputSurfaceTexture();
-                        dispatchOnOutputSurfaceAvailable(width, height);
-                    }
-                });
-            }
-        });
-    }
-
-    // This does not work. We get: startPreview failed.
-    private void onSizeChangeImplementation2(final int width, final int height) {
-        releaseInputSurfaceTexture();
-        getView().post(new Runnable() {
-            @Override
-            public void run() {
-                getView().onPause();
-                getView().onResume();
-                getView().queueEvent(new Runnable() {
-                    @Override
-                    public void run() {
-                        createInputSurfaceTexture();
-                        dispatchOnOutputSurfaceSizeChanged(width, height);
-                    }
-                });
-            }
-        });
-    }
-
-    // Works! So we don't need to recreate the GL texture.
-    private void onSizeChangeImplementation3(final int width, final int height) {
-        dispatchOnOutputSurfaceDestroyed();
-        getView().post(new Runnable() {
-            @Override
-            public void run() {
-                getView().onPause();
-                getView().onResume();
-                getView().queueEvent(new Runnable() {
-                    @Override
-                    public void run() {
-                        dispatchOnOutputSurfaceAvailable(width, height);
-                    }
-                });
-            }
-        });
-    }
-
-    // Works! This is getting easy.
-    private void onSizeChangeImplementation4(final int width, final int height) {
-        dispatchOnOutputSurfaceDestroyed();
-        getView().post(new Runnable() {
-            @Override
-            public void run() {
-                getView().onPause();
-                getView().onResume();
-                dispatchOnOutputSurfaceAvailable(width, height);
-            }
-        });
-    }
 
-    // Does not work. onPause and onResume must be called on the UI thread.
+        /**
-    // This make sense.
+         * Called on the renderer thread after each frame was drawn.
-    private void onSizeChangeImplementation5(final int width, final int height) {
+         * You are not supposed to hold for too long onto this thread, because
-        dispatchOnOutputSurfaceDestroyed();
+         * well, it is the rendering thread.
-        getView().onPause();
+         *
-        getView().onResume();
+         * @param surfaceTexture the texture to get transformation
-        dispatchOnOutputSurfaceAvailable(width, height);
+         * @param scaleX the scaleX (in REF_VIEW) value
+         * @param scaleY the scaleY (in REF_VIEW) value
+         */
+        void onRendererFrame(SurfaceTexture surfaceTexture, float scaleX, float scaleY);
     }
 
-    // Does NOT work. The EGL context must be recreated
+    void addRendererFrameCallback(@NonNull final RendererFrameCallback callback) {
-    // for this to work out.
+        getView().queueEvent(new Runnable() {
-    private void onSizeChangeImplementation6(final int width, final int height) {
-        dispatchOnOutputSurfaceDestroyed();
-        getView().post(new Runnable() {
             @Override
             public void run() {
-                getView().setPreserveEGLContextOnPause(true);
+                mRendererFrameCallbacks.add(callback);
-                getView().onPause();
+                if (mOutputTextureId != 0) callback.onRendererTextureCreated(mOutputTextureId);
-                getView().onResume();
-                getView().setPreserveEGLContextOnPause(false);
-                dispatchOnOutputSurfaceAvailable(width, height);
             }
         });
     }
 
-    interface RendererFrameCallback {
+    void removeRendererFrameCallback(@NonNull final RendererFrameCallback callback) {
-        // Renderer thread.
+        mRendererFrameCallbacks.remove(callback);
-        void onRendererTextureCreated(int textureId);
-
-        // Renderer thread.
-        void onRendererFrame(SurfaceTexture surfaceTexture, float scaleX, float scaleY);
-    }
-
-    void setRendererFrameCallback(@Nullable RendererFrameCallback callback) {
-        mRendererFrameCallback = callback;
-        if (mRendererFrameCallback != null && mOutputTextureId != 0) {
-            mRendererFrameCallback.onRendererTextureCreated(mOutputTextureId);
-        }
     }
 }