Update: Jonathan Moore points out that Vimeo has had HD video playback for ages and their content does not suffer the low framerate playback issue that YouTube demonstrates. However, the Flash playback there does still max out this Core 2 Duo CPU, rather than the 20% usage required by Quicktime.

It’s basically accepted at this point that Adobe Flash is a poorly written, total piece of shit. Now YouTube has exposed how bad things have gotten with a new demo for their 1080p HD video feature (via Scott Schiller.) Hit playback, and observe the video stutter and your machine grind to a halt.

The core of the issue is lack of H264 hardware acceleration in Flash, but it manifests as completely unwatchable, stuttering, 2fps video playback, using all available CPU resources on a brand new MacBook Pro. But, if you use Click To Flash in Safari (and you should; browsing the internet much faster), you get an option to instead load YouTube videos natively in the browser, using the HTML5 <video> element. This uses Quicktime for playback. Here, the playback is smooth, and CPU usage is only 20%.

The benefits of hardware accelerated H264 decoding is an easy troll on Flash, but it’s still a massive usability issue for YouTube. It’s not just that watching videos will send you laptop fans into overdrive (as it does already), it’s that the new video is unwatchable. If they intend to launch 1080p as a feature, they’re going to need to use HTML5 native video by default, with Flash relegated to the fallback. That’s a consequentially huge boost for the Open Web technology. Larger deployment and exposure is good, but what’s especially striking is that HTML5 comes into play not just for ‘being open’ and standardised, but because the implementations are superior.