Prevent page from jumping while changing position

问题:

I have a video on my site and a window scroll function. When somebody scrolls under the video and is at level of a fake div element, the video is changing position from relative to fixed and then comes back on scrolling to the top. The problem is that the page jumps whenever I do it (because the element is removed and placed somewhere else). I tried to use animate and fadeOut functions but these didn't seem to help.

Check out this fiddle for what I mean:

https://jsfiddle.net/xwgza7qf/2/

var h = $('#fake-element').position().top;
console.log(h);
            $(window).scroll(function(){
                var y = $(window).scrollTop();
                if( y > h){
                    $('#video').css({
                        'position' : 'fixed',
                        'display' : 'block',
                        'left' : '50px',
                        'width' : '50px',
                        'top' : '45px'
                    });
                } else {
                    $('#video').css({
                        'position' : 'relative',
                        'display' : 'block',
                        'left' : '0px',
                        'width' : 'auto',
                        'top' : '0px'
                    });
                }
            });

When you scroll to the moment (fake div) where #video goes to fix position, the page jumps, the scrolling is not smooth. How can I achieve the effect of smooth scrolling in this case. I want to do something like on this site:

http://www.cnn.com/2016/02/01/politics/iowa-caucuses-2016-highlights/index.html

but have no idea how they achieved this (video goes to fixed to the right sidebar on scrolling and scrolling is still smooth, works perfect on Firefox).