HD video playback - H.264
Next up, we have some high-definition video playback tests. We've measured both CPU utilization and system-wide power consumption during playback using a couple of HD DVD movies with different encoding types. The first of those is Babel, a title encoded at a relatively high ~25 Mbps with H.264/AVC. We tested playback during a 100-second portion of Chapter 3 of this disc and captured CPU utilization with Windows' perfmon tool. System power consumption was logged using an Extech 380803 power meter.
We conducted these tests at 1920x1080 resolution on the Radeon HD cards and at 1280x800 on the GeForce 8800 cards, since they don't support HDCP with dual-link DVI and thus can't play HD DVD movies at higher resolutions on our Dell 3007WFP display. (We should note that this limitation shouldn't apply to single-link DVI connections, even at 1920x1200 resolution.) To confirm that scaling the movie down to lower resolutions wouldn't put the GeForce cards at a disadvantage, I also did some testing with the Radeon HD 2900 XT at 1280x800 resolution and found that playing movies at the lower resolution didn't have a significant impact on power use or CPU utilization.
Also, I disabled noise reduction on the GeForce 8800 cards for our HD DVD playback tests. Nvidia's post-processing results in a net loss of image quality, so leaving it on didn't make any sense. ATI's noise reduction looks better, which is good, because it can't be disabled via Catalyst Control Center. I did try the GeForce 8800 Ultra with noise reduction enabled, and the feature had only a minimal impact on power consumption and and CPU use.
Among the high-end cards, the GeForce 8800s use slightly less CPU time to play the movie. The 2900 XT cards draw less power during playback, though, and the 1GB GDDR4 version averages about 6 watts less than its GDDR3 counterpart.
