$('iframe.wrapAspect').mediaWrapper();
<header>Katy Perry</header>
<img style="width:100%; height:auto;" src="css/images/Katy Perry.jpg" />
<header style="padding-top:20px;">YouTube</header>
<iframe class="wrapAspect" src="https://www.youtube.com/embed/tWbLkXhGEmo" width="640" height="360" frameborder="0" allowfullscreen></iframe>
<header style="padding-top:20px;">Vimeo</header>
<iframe class="wrapAspect" src="https://player.vimeo.com/video/13031989" width="640" height="360" frameborder="0" sallowfullscreen"></iframe>