Benchmarks - Video Decoding CPU Utilisation

The video decoding capabilities of the graphics processor should offload more video operations from the CPU to be processed directly on the video core. Here we'll take a look at the CPU utilisation under three decoding operations, DVD MPEG-2, High Definition (1080i) WMV9 and DiVX in order to see which board provides the lowest CPU utilisations under each of the formats, using the current WHQL certified 66.93 drivers. In each case we used the same Terminator 2 trailer clip found at Microsoft's High Definition Video site, converted it into the other two formats and played each one back through Windows Media Player 10, monitoring the CPU utilisation via the Performance Monitor in the Microsoft Management Console.

Note: Normally in these tests we'd only look at performances from boards that are on the same system platforms as the CPU utilisation can differ dependant on the rest of the platform. However, one of the biggest influencers of video processing at the system level is the CPU itself, especially between Intel and AMD platforms. In this case, as we are able to use the same CPU, and memory subsystem thanks to AMD's integrated memory controller, many of the largest influencing factors should be negated so we'll leave in the results for the 5200 Ultra AGP board.

The GeForce 6 series houses a new programmable video processor, which has now been re-branded as "PureVideo", which NVIDIA tells us is unit dedicated to video processing and can clock independently of the main 3D core clock speed. In this instance, with straight MPEG2 DVD quality playback the 6600 GT appears to have a slightly higher CPU overhead than the 6200 does, for some reason. On the other hand, the CPU utilisation of MPEG2 playback on the 5200 Ultra is lower than both the GeForce 6 boards.

With DiVX playback this time we see that the 6200 now has the highest CPU utilisation whilst the 6600 GT has a little less, and the 5200 Ultra even less still - nearly half the utilisation than the 6200 in fact.

With high resolution WMV9 playback we see a similar trend as with DiVX playback with the 6200 having the highest CPU utilisation, the 6600 GT next and then the 5200 Ultra actually having the lowest, although not by as great a margin in these cases.

Given the fact the the 6200 and 6600 GT are actually using the same core the performance differences between the two we see here tend to indicate that, at least in these drivers, either the video engine is running at different speeds on the two boards and / or some Pixel Shading processing capabilities are being utilised to assist video decoding.