Recording Live OpenCV Processing on Android

Question

My goal is to do a couple things:

1. Use OpenCV and the JavaCameraView to process frames from the phone\'s camera feed
2. Enable recording of that processed

Answer 1

I've solved a similar problem by creating a MediaRecorder and passing it to a OpenCV CameraBridgeViewBase, which I've modified as follows.

protected MediaRecorder mRecorder;
protected Surface mSurface = null;

public void setRecorder(MediaRecorder rec) {
    mRecorder = rec;
    if (mRecorder != null) {
        mSurface = mRecorder.getSurface();
    }

and

protected void deliverAndDrawFrame(CvCameraViewFrame frame) {
    Mat modified;

    if (mListener != null) {
        modified = mListener.onCameraFrame(frame);
    } else {
        modified = frame.rgba();
    }

    boolean bmpValid = true;
    if (modified != null) {
        try {
            Utils.matToBitmap(modified, mCacheBitmap);
        } catch(Exception e) {
            Log.e(TAG, "Mat type: " + modified);
            Log.e(TAG, "Bitmap type: " + mCacheBitmap.getWidth() + "*" + mCacheBitmap.getHeight());
            Log.e(TAG, "Utils.matToBitmap() throws an exception: " + e.getMessage());
            bmpValid = false;
        }
    }

    if (bmpValid && mCacheBitmap != null) {
        Canvas canvas;

        if (mRecorder != null) {
            canvas = mSurface.lockCanvas(null);

            canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
            Log.d(TAG, "mStretch value: " + mScale);

            if (mScale != 0) {
                canvas.drawBitmap(mCacheBitmap, new Rect(0,0,mCacheBitmap.getWidth(), mCacheBitmap.getHeight()),
                     new Rect((int)((canvas.getWidth() - mScale*mCacheBitmap.getWidth()) / 2),
                     (int)((canvas.getHeight() - mScale*mCacheBitmap.getHeight()) / 2),
                     (int)((canvas.getWidth() - mScale*mCacheBitmap.getWidth()) / 2 + mScale*mCacheBitmap.getWidth()),
                     (int)((canvas.getHeight() - mScale*mCacheBitmap.getHeight()) / 2 + mScale*mCacheBitmap.getHeight())), null);
            } else {
                 canvas.drawBitmap(mCacheBitmap, new Rect(0,0,mCacheBitmap.getWidth(), mCacheBitmap.getHeight()),
                     new Rect((canvas.getWidth() - mCacheBitmap.getWidth()) / 2,
                     (canvas.getHeight() - mCacheBitmap.getHeight()) / 2,
                     (canvas.getWidth() - mCacheBitmap.getWidth()) / 2 + mCacheBitmap.getWidth(),
                     (canvas.getHeight() - mCacheBitmap.getHeight()) / 2 + mCacheBitmap.getHeight()), null);
            }

            if (mFpsMeter != null) {
                mFpsMeter.measure();
                mFpsMeter.draw(canvas, 20, 30);
            }
            mSurface.unlockCanvasAndPost(canvas);
        } 

    }

    ...

}

I've left the original part of deliverAndDrawFrame as is, so that it keeps displaying the output to the original surface. This way I can process images from a camera by implementing onCameraFrame in MainActivity and save the resulting images to a video, without the need for ffmpeg.

EDIT I've set up the MediaRecorder as follows

recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
recorder.setVideoSource(MediaRecorder.VideoSource.SURFACE);

CamcorderProfile cpHigh = CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH);
recorder.setProfile(cpHigh);
recorder.setOutputFile("out.mp4");
recorder.setVideoSize(mOpenCvCameraView.mFrameWidth, mOpenCvCameraView.mFrameHeight);

recorder.setOnInfoListener(this);
recorder.setOnErrorListener(this);
recorder.prepare();

register it with the OpenCvCameraView

mOpenCvCameraView.setRecorder(recorder);

and start recording

recorder.start();