Hi there Tron,
I am not 100% sure of your requirement, but this example might be close to it...
If that is something that you might like to mess around with then check out the attachment.
video-frame-capture.zip (1.0 MB)
This will work OK locally with Firefox, but other browsers require it to be uploaded to a server.
YouTube has these versions which will save downloading:
Sorry John, but to which download are you actually referring?
The link referenced in your post shows a video which I assumed to be the video to be downloaded.
I am tapping on my tablet at the moment and unable to try your supplied source code.
The video in question is on my server and coded into the "HTML5 video element".
Youtube videos, I believe, are coded into an "iframe element".
If you are speaking on terms about gifs, then there's actually an easier way of extracting an exact image out of gifs. You just download the gif file and open it up in an image editing software such as PhotoShop or FireWorks and in the States option, you can actually see each picture frame-by-frame. gifs are basically images that are animated at a set speed. I could basically create a gif file from 5 jpg files if I really wanted to using PhotoShop or FireWorks.