How can I get the parallax to be smooth?

Like this:

https://www.spotify.com/us/

I tried to add: data-stellar-ratio="2"

Into page--front.tpl.php but it didn't appear to change anything.

Is it related to this instead?
function parallaxInit() {
$('#one-parallax').parallax("50%", .5);
$('#two-parallax').parallax("50%", .5);
$('#three-parallax').parallax("50%", .5);
$('#four-parallax').parallax("50%", .5);
$('#five-parallax').parallax("50%", .5);
$('#six-parallax').parallax("50%", .5);
$('#seven-parallax').parallax("50%", .5);