Both the ATI and Nvidia mainstream cards include a piece of silicon on die that handles video decoding. The first image shows what happens when the CPU does all of the decoding. The first core is over 60% utilized while the second is at 30-40% making the total utilization between 50 and 60%.
When the HD DVD decoding is done on the by ATI's Universal Video Decoder, the CPU utilization drops to a total of 10-15% with the second core doing almost nothing. This shows just how much work can be offloaded to the GPU for the decoding process.
Nvidia didn't do as well as the ATI UVD acceleration using the InterVideo software with the hardware acceleration options enabled: it is still lower than CPU only option. We are going to revisit this with the next AVIVO vs. Pure Video update that Don Woligroski is currently working on. We wanted to demonstrate that these functions were operational on both companies' hardware.