X-bit labs

Ready to HD: Performance of Contemporary Graphics Accelerators during Video Playback (page 11)

Category: Video

by Alexey Stepin , Yaroslav Lyssenko, Anton Shilov

[ 02/26/2007 | 05:24 PM ]

Conclusion

Our tests show that almost each of today’s graphics cards has everything necessary to play high-definition video formats, let alone the traditional DVD and DivX. We mean both hardware and software: the tests suggest that the graphics card drivers have been polished off so that even 1920x1080 video is decoded and played without any performance or quality related problems.

The CPU is loaded quite heavily at that, especially when it comes to the current version of ATI Avivo and H.264, but that’s not a serious problem considering how much computing power modern dual-core CPUs provide. Still, we can’t explain why Avivo is very fast at decoding H.264 and WMV HD video with a resolution of 1280x720 pixels, but slows down when the resolution is increased to 1920x1080. It may be a hardware problem (some bottleneck in the Avivo architecture that shows up at high bit-rates and resolutions) or a software one (related to the noise reduction and detail enhancement algorithms that can’t be disabled).

Both technologies offload the CPU to an acceptable level, but Avivo provides a somewhat sharper and less noisy picture than PureVideo HD at the default settings. The latter, however, makes up for that by providing more flexible options to reduce noise and improve detailedness.

Video playback performance of graphics cards from different price categories varies in a rather small range, yet we can make some points here. First, this performance depends on the graphics core frequency, specifically on the frequency of the pixel shader processors. This explains the record-breaking results of the GeForce 8800 series whose shader processors are clocked at frequencies above 1GHz. It is also clear that a rather small number of shader processors are actually employed – just compare the results of the Radeon X1950 XTX against the Radeon X1650 Pro or the GeForce 7900 GS against the GeForce 7600 GT. Such parameters as the amount and frequency of graphics memory or the width of the graphics memory bus do not influence performance of the hardware video processor much.

The entry-level solutions are different. Such graphics cards either have slow memory with a narrow memory bus like the GeForce 7300 GS or have few pixel processors on board like the Radeon X1300 Pro. Their video processors are thus greatly constrained and do not suit well for playing HD formats with a high bit-rate or resolution, especially if you’ve got a single-core CPU. The rest of today’s graphics cards, from the modest Radeon X1600 Pro and GeForce 7600 GT to the ragingly fast Radeon X1950 XTX and GeForce 8800 GTX, do their job well.

So, the choice of the graphics card for a multimedia center is in fact determined by such factors as noise and your desire to play games. If you don’t want to build a gaming station, you can do quite well without a GeForce 8800-class graphics card.