Has anyone else huge problems with YouTube’s HTML5 player on the desktop? You can test it out if you activate it at http://youtube.com/html5. Be sure to watch a video without ads, only those will use the HTML5 player.

I’m running OS X Lion and Safari and I get stuttering video and awful performance. This doesn’t happen to me with any other HTML5 video player.

Do you have Perian installed? Does http://www.youtube.com/html5 report that Safari supports WebM? If so, then what you’re seeing is YouTube preferring WebM over h.264, even though h.264 decoding is hardware accelerated rather than the software decoding that Perian’s WebM support provides. You can try temporarily disabling Perian, relaunching Safari, and then watching a video again to see whether the performance is more in line with your expectations.

Oh dear, that is what it is? That's why HTML5 videos have become all but unusable on Youtube as of late and I have to fallback to Flash, of all things?

Yup. It’s really unfortunate.

I prefer to opt out of YouTube’s HTML5 mode and use the YouTube5 extension to achieve a similar effect. It also has the added benefit of avoiding the Flash player on videos where YouTube chooses not to use the HTML5 player.

Thanks! That seems to be the problem. Perian is so useful, I don’t want to disable it just to use YouTube’s HTML5 player. I guess I will have to stick to Flash. (Or try again with ClickToFlash or something.)

Try the YouTube5 extension for a happy medium between ClickToFlash and Flash.

I think they are focusing more on WebM than h.264, so check it out with Chrome. They are probably fading out support for h.264.

I don’t think so. I have no problem playing YouTube videos on (Apple’s) mobile devices. The experience there is smooth and they use h.264.

Is that on the web or through the native Youtube player that usually opens up when there's a youtube video?

That’s both inside the YouTube app and on the mobile YouTube website.

Not just yet, I would think; no current mobile device has hardware WebM decoding.

"Be sure to watch a video without ads" - well I'd love to but I did not find the "watch without ads" button in the Youtube UI.

As long as all the videos I come across still ask me to install Flash although I have activated the html5 thing, I fail to see the point...

Ads on YouTube are enabled on a per-account or per-video basis. Many videos have no ads.

Does anyone have any links to 1080p videos that work with the HTML 5 player.

Here's one that only seems to work with the flash player http://www.youtube.com/watch?v=qb7zjKkLCoQ (Glee - Rumour Has It)

This is the second article I see with these information. The 1080p playback is in for many months, though. Captions and annotations are newer, but also available for at least some weeks now.

So the only added feature is that it is in 1080p WebM / HTML5 combination? (Since H264/HTML5 1080p was already available)