Using the onFrameAvailable() to save or record the images on the tango tablet

Question

I am new to google-project-tango, and I want to record the images from Tango's color camera image buffer rather than fisheye camera. I saw henderso's sharing -- reading of the GL buffer to save the image, and modified his code to record the images-- keep saving every image when we get any onFrameAvailable() callback. I also try to lock the buffer or use semaphore, when i got the onframeavailable callback. But the results look like this one--is it the synchronization problem of GL buffer?.

The MainActivity implements TangoCameraScreengrabCallback:

        public void onFrameAvailable(int arg0) {                
            if (mIsRecording){
                tangoCameraPreview.takeSnapShot();
                try {
                    mutex_on_mIsRecording.acquire();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                tangoCameraPreview.onFrameAvailable();
                mutex_on_mIsRecording.release();

            }
        }

And tangoCameraPreview.onFrameAvailable() will do as follows:

    public void onFrameAvailable() {
        super.onFrameAvailable();
        if(recording) {
            synchronized (intBuffer){
                screenGrabRenderer.grabNextScreen(SCREEN_GRAB_X, SCREEN_GRAB_Y, SCREEN_GRAB_W, SCREEN_GRAB_H, intBuffer);
            }
        }
    }