Originally Posted by MacRulez
That's mixing up a lot of variables and attributing them all to Flash. Look at the web page: there are many things going on there, including dynamic ad overlays. Not all of that is Flash playback, but a mix of extra Flash movie overlays and and to some degree even Safari itself.
OK, that's a fair point. So let's investigate. A reminder that all CPU usage numbers are for a MacBook Pro with a 2.4 GHz Core 2 Duo CPU.
On a newly-launched instance of safari, with a blank main window, and the activity and downloads windows also open, CPU usage is as one would hope: 0 %.
Now, navigating to http://www.youtube.com/watch?v=GFSDi...FY4e4Qodty-DZA
with ClickToFlash installed so the video part of the page doesn't do anything, and waiting until the page is fully loaded before measuring CPU usage, and you still have very low CPU usage: 0.4 %.
Now, clicking on the flash, waiting until it has fully downloaded the clip, and stopping the clip from playing, then measuring CPU usage and you get: 12 % CPU!
Yes, that's right. Flash uses 12 % CPU to do absolutely nothing
. That's already pretty damning.
Now play the clip and you get 100 - 110 % CPU.
Now, if you want to say "well, maybe Flash would only use 40 % CPU if the only thing it was doing was decoding the video data", that means you're attributing 60 - 70 % CPU usage to processing the single pop-up advert, even before and after the advert appears! Does this sound realistic?
The answer is clear: Flash on OS X is incompetently engineered and uses three times as much CPU time to decode video compared to an open-source video player. Said open-source video player does not use hardware acceleration on OS X. This proves that Adobe could cut Flash CPU usage for video decode by up to two-thirds without using any hardware acceleration