Let’s say our browser window W currently scrolled to y-position scrollTop and scrollBottom
Our video will NOT be played when its position is at V1 or V2 as below snapshot.
        $(document).ready(function() {
            // Get media - with autoplay disabled (audio or video)
            var media = $('video').not("[autoplay='autoplay']");
            var tolerancePixel = 40;
            function checkMedia(){
                // Get current browser top and bottom
                var scrollTop = $(window).scrollTop() + tolerancePixel;
                var scrollBottom = $(window).scrollTop() + $(window).height() - tolerancePixel;
                media.each(function(index, el) {
                    var yTopMedia = $(this).offset().top;
                    var yBottomMedia = $(this).height() + yTopMedia;
                    if(scrollTop < yBottomMedia && scrollBottom > yTopMedia){ //view explaination in `In brief` section above
                        $(this).get(0).play();
                    } else {
                        $(this).get(0).pause();
                    }
                });
                //}
            }
            $(document).on('scroll', checkMedia);
        });
#JS-Fiddle
