Jquery if condition then change video width

Jquery if condition then change video width

I'm new to jquery and I'm having issues with this code. I am trying to set
a condition for the #content_container width, and if true, then find all
.m4v videos and change their width and height.
Can someone please help me?
Thank you!
$(function() {
if ((#content_container).width == '600px')
$('media[src$=".m4v"]').width(400).height(200);
});