PureVideo HD: Now Really in Hardware!
PureVideo technology was first time introduced by Nvidia within NV40 graphics processor that was the heart of the high-performance GeForce 6800 family. This unit was disabled in the very first GPU batches because of some hardware defect it had, but even when this problem was solved it turned out that it was the first-generation video processor that cannot work with HD-content. Fully-fledged version of PureVideo appeared only in the less high-performance but more mainstream NV43 GPU, which was the basis for the GeForce 6600 family. After that this technology continued to exist without any significant hardware enhancements up until GeForce 8800 arrived.
This introduction will help you to better understand what has really happened this time. History has the tendency to repeat itself and looks like the story of GeForce 6800 and 6600 is about to be repeated on the level of GeForce 8800 and 8600. The thing is that despite all claimed enhancements of the PureVideo technology and the addition of the “HD” abbreviation to the name that stands for high-definition video support, all these enhancements remained purely software. PureVideo could perform motion compensation and post-processing on the hardware level, but that was about it: all advanced encoding methods were still the prerogative of the central processing unit.
Namely, it is true for MPEG-4 AVC format also known as H.264 that uses Context-Adaptive Variable Length Coding (CAVLC) and Context-Adaptive Binary Arithmetic Coding (CABAC) entropic encoding algorithms. Advanced H.264 encoding techniques provide extremely high image quality at a good compression level, however, they require huge computational capacity from the decoder, which falls onto the CPU’s shoulders even with the GeForce 8800 installed into the system.
Only the new Nvidia GPU family knows to perform real hardware H.264 decoding thanks to the corresponding unit. Moreover, the decoding process is now being performed completely on the hardware level thanks to the additional AES128 unit responsible for decoding protected video content.
Since GeForce 8600 is a mainstream GPU the situation is very similar to what we have just described above. This is the second case when it is not the flagship Nvidia product that received advanced video decoding capabilities, but the mainstream one, with lower performance in gaming applications.
According to Nvidia, the new PureVideo HD version can decrease the CPU workload much greater than all technologies existing in the market before the GeForce 8600. Practice will show if this is true or not. As for the image quality, nothing new has been introduced here: it is promised to be the same as by GeForce 8800.