if(bi==null)return ret;
Profile.begin();
//create current frame image and scale it
IImage2d inputNow=new ImageRGBA();
inputNow.create(bi);
sfNow.init(inputNow.getWidth(), inputNow.getHeight(), 16, 2);
sfNow.filter(inputNow);
Profile.out();
if(inputPrev!=null){