Fullscreen doesn’t preserve original aspect ratio

[DrWhat]

When clicking the fullscreen button for videos on YouTube, the video will stretch to fill the entire screen disregarding the original aspect ratio of the video.

A possible workaround can be found inside this extension:

http://www.cyberhq.nl/2010/06/08/restore-full-screen-playback-in-youtubes-html5-player.html

[ghost]

I've noticed this as well—it's a lot more apparent on older 4x3 YouTube videos like this one:

http://www.youtube.com/watch?v=bNF_P281Uu4

[DrWhat]

Indeed, it is.

This is how the author of FullScreenYouTube deals with it:

function goToFullScreen(){
var video = document.getElementsByClassName("video-stream")[0];

// Set the width of the video /element/ to the width of the actual video to
// prevent stretching a 4:3 video onto a 16:9 screen
// Note: this currently breaks the 'change size' function because the size sticks and
// we can't detect exiting full-screen to reset it.
var w = (video.clientHeight * video.videoWidth) / video.videoHeight;

video.style.width = Math.ceil(w) + "px";
video.style.height = video.clientHeight + "px";

video.webkitEnterFullScreen();

}

Pretty neat and it does the job well.