Besides, the MP4 version has stereo sounds unlike the HQ FLV.

(not to mention the MP4 version has a smaller file size, which is great for those of us with non-uber connection speeds)

Do you think you could make the video automatically pause when you click the "watch this video in HD" button? On slower PCs, loading another page while the video is still playing takes a while (the CPU is being taken up by the video leaving barely any for page loading). Yes you could just hit the pause button, but my not-as-tech-savvy dad won't know that (whom which I hooked up this script with).

I've found something interesting... it seems that the built-in "watch in high quality" videos on youtube are encoded in mono audio (which are encoded in FLV), while the MP4 versions are in stereo.

Also, the FLV HQ versions are actually larger in file size than the MP4 versions. Makes you wonder why YouTube insists on sticking with FLV...

Here's a good example of this:
http://www.youtube.com/watch?v=ALJmg1UBgGI

Oh no, not the spammers...

anyway, some videos do not have MP4 versions available, and therefore do not load with this script.

Now if there's no MP4 video and you're only using the "&fmt=18" trick, it just plays the lower quality version. Is there any way to make this happen with the script as well?

Example video with no MP4 version:
http://youtube.com/watch?v=Hfahp4J_-_o

alright, cool. Though, take note, my name is actually "Nintendo Maniac 64" bit it's too long and gets cut off XD (hence the ... at the end)

I've noticed that when you click the "original" link, then reload the page, the high-quality video won't play (it tries to load endlessly)

I think what happens it that clicking the "original" link adds a # to the end of the URL, and when you reload, the # is still in the url, and this script can't locate the HQ video then.

Is there any way that the script could ignore the # when it's at the end of the URL?

Umm, youtube just changed their site around and now this script no longer works. (even though adding &fmt=18 to the end of the url still works)