Despite modest technical characteristics of mainstream graphics cards, it is only the GeForce 7900 GS and GeForce 7600 GT that produce different results when playing MPEG-2 1080i. The former graphics card has a low core frequency while the latter is probably limited by its 128-bit memory bus.
When playing DivX SD on the GeForce 7900 GS, the peak CPU load is abnormally high, but it is rather the consequence of our not-very-accurate measuring method because we don’t see anything like that while playing DivX HD. The CPU load is 34-36% on average then.
The Radeon X1600 Pro has the worst result, most likely due to an imperfect implementation of H.264 decoding in the driver because this card is only 2% behind the Radeon X1900 XT at the 1080p resolution.
The memory bus is not an important factor here: the GeForce 7600 GT offloads the CPU better than the GeForce 7900 GS that has a 256-bit memory bus and 20 pixel processors. A direct relation between performance of the PureVideo HD engine and the GPU frequency is obvious.
The decoding of VC-1 in 720p@60fps format produces about the same results as with the graphics cards from the higher class, except that the peak CPU load has become 1-2% higher with Nvidia’s solutions.
The GeForce 7600 GT is in the lead again when processing WMV HD as well as H.264 content. We don’t see the mainstream graphics cards from AMD and Nvidia being much weaker than the more advanced products.
Thus, modern graphics cards from the mainstream category are capable of playing video of any existing format, including full-HD formats, no worse than more advanced and expensive solutions from higher product categories. And now let’s see how the cheapest products behave.