This is not a trick question, but more of a pushback on the recent FUD that various people have been spreading. Quotes such as 'HTML5 video uses 10% CPU while Flash uses 100%' were both unprofessional and not backed up by any actual data. The short answer to the above question could in fact be yes - if I wanted to spin these results, but the more correct way of putting things would actually be: 'It depends'.

My co-author Jan has gone through some lengths to come up with the most thorough like-for-like comparison of HTML5 versus Flash video decoding requirements as far as CPU usage is concerned. His conclusions follow below, and I recommend you head over to his blog for the full story.

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Overall Conclusions
When it comes to efficient video playback, the ability to access hardware acceleration is the single most important factor in the overall CPU load. On Windows, where Flash can access hardware acceleration, the CPU requirements drop to negligible levels. It seems reasonable to assume that if the Flash Player could access GPU-based hardware acceleration on the Mac (or iPod/iPhone/iPad), the difference between the CPU required for HTML5 playback and Flash playback would be very much narrowed, if not eliminated.

I don't follow the politics of the situation, but after noting significant playback efficiencies in Flash Player 10.1 on the Mac, respected technologist and AnandTech founder Anand Lai Shimpi commented "with actual GPU-accelerated H.264 decoding I'm guessing those CPU utilization numbers could drop to a remotely reasonable value. But it's up to Apple to expose the appropriate hooks to allow Adobe to (eventually) enable that functionality." So it looks like the ball is in Apple's court.

Overall, it's inaccurate to conclude that Flash is inherently inefficient. Rather, Flash is efficient on platforms where it can access hardware acceleration and less efficient where it can't. With Flash Player 10.1, Flash has the opportunity for a true leap in video playback performance on all platforms that enable hardware acceleration.

Turning full circle, if Anand is right, and I don't doubt that he is, Apple complaining about Flash being a CPU Hog while not exposing "the appropriate hooks" to enable Adobe to access hardware acceleration seems disingenuous at best. To be fair to Apple, though, the iPad related timing was unfortunate, with the bulk of the development work done under the shadow of Flash Player 10.0, which didn't offer hardware acceleration other than full screen on any platform and was clearly less efficient than the HTML5-based approach Apple adopted. Now that Adobe has proven the concept on Windows, perhaps Apple will cooperate with Adobe to make hardware acceleration on the Mac, iPad and future devices happen. If they choose not to, however, they should quit pointing fingers at Flash.

What else? We also learned that not all HTML5 browsers/H.264 decoders are created equal. Significantly, with Flash 10.1 deployed, Google's HTML5 implementation required the most CPU horsepower of all playback scenarios -- by far -- on the Windows platform. On the Mac, Firefox and Safari with Flash required less CPU horsepower than Chrome's HTML5 implementation.

At least from a CPU utilization perspective, Flash isn't BAD and HTML5 isn't GOOD. It all depends upon the platform and implementation.
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For the full test procedure and detailed results head over to Jan's blog.