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 most of the cards, but we were surprised to discover something about our GeForce 8500 GT and 8600 GT cards from MSI and XFX: none of them support HDCP at all, even over a single DVI link, let alone dual. As a result, we had to test those cards at 1920x1440 resolution—still no scaling required—over an analog connection to a CRT monitor. The GeForce 8600 GTS and all of the Radeon HD cards worked perfectly with HDCP over a dual-link DVI connection to our Dell 30" LCD.

Both the UVD logic in the Radeon HD 2400/2600 cards and the VP2 video processor in the GeForce 8500/8600 cards can accelerate H.264 decoding quite fully. We've also included a couple of high-end GPUs that lack UVD and VP2, to see how they compare.

All of the low-end and mid-range cards achieve substantially lower CPU utilization thanks to their H.264 decode capabilities. The high-end cards' much higher scores drive that point home. The Radeon HD 2400 and 2600 cards do seem to consume a few more CPU cycles than their GeForce counterparts, though.

The story on power consumption is similar. The systems sporting GeForce 8500 and 8600 cards draw around 10 watts less than their Radeon HD competitors, but both GPU brands look to be very efficient overall.

As a side note, the absence of UVD on the Radeon HD 2900 XT pretty much means what we expected: this GPU performs no better in HD video playback than its GeForce 8800 competition. In fact, the GeForce 8800 GTX consumes fewer CPU cycles while drawing the same amount of power.