In the last few years both Nvidia and ATI have proposed a video decompressing engine on their products. Thus were born Avivo and Purevideo, though they have gone through multiple evolutions since their first versions. We actually tested them in July 2005 and March 2006 Back then they had very limited capabilities, even bugged on some cards, but they come back today in “HD” version. Both claim to be capable of taking charge of HD videos on their own, even the more power hungry in 1080p, without shadow of a doubt. AvivoHD The Avivo HD engine of ATI is still very new. Contrary to previous models, the Avivo HD wears its name well as it undertakes all the decoding operations of all the HD H.264, VC-1 and MPEG2 HD formats. ATI assures that it holds up speeds of 40 Mbps which is the maximum authorised by the Blu-ray discs format. It’s based on two basic distinct components. The Unified Video Decoder (UVD) and the Advanced Video Processor (AVP). The first is in charge of the decoding steps while the other is dedicated to optimisation and post treatments.

These two components are completely dissociated from the 3D heart of the GPU. Their performance does not depend of the normal power level of the GPU, which is the polar opposite of the previous Avivo which took parts from the GPU’s shaders.

This doesn’t mean that the performance between a HD 2400 Pro and a 2600 XT will be identical. Other elements play a part, notably memory itself, which is of course used by AVIVO engines. There also seems to be other differences in the complexity of the post-treatment operations carried out, as ATI recognises itself that a Radeon HD 2400 XT would not offer the same image quality as a HD 2600.

We also observed that ATI’s GPU RV610 and RV 630 integrate all of the components necessary for the encryption of HDCP and of the HDMI (1.2 only) interface, via a provided DVI/HDMI. So they’re compatible with HD discs and displays, even those which require a DVI dual-link interface.

ATI has even pushed so far as integrating a HD chip in the core of the GPU. This isn’t of much interest to us users, as all motherboards already have such a chip, but it allows manufacturers to put the Vista Premium logo on their machine for peanuts.

The Avivo HD is only present in the Radeon HD 2400 and HD 2600. The HD 2900 didn’t get the same treatment, and must be content with the (thankfully debugged) Avivo first generation. The HD 2900 then accelerates the DCT movement compensation calculations but not the entropic encoding. Its Avivo also carries out all the post treatment operations. Purevideo For its Purevideo HD, Nvidia has chosen an approach similar to ATI’s. PureVideo HD is based on dedicated components which are distinct from the graphic core. This was actually the case for the PureVideo non-HD of the Geforce 6 and 7. In comparison to its ancestors, the newcomer is made of two additional components: the BSP, or bit stream processor, and the AES engine, AES encryption motor. Also, the Video Processor was remodelled and moved on to version 2.

These improvements brought optimisations to the management of the inverse discrete cosines transformer, of the movement compensation and of the antiblock filtration. This concerns the MPEG 2 (DVD) as well as the VC-1 and the H.264 (up to 40 Mb/s). Another addition is, the handling of Picture in Picture, this possibility is used by certain HD DVD or Blu-ray bonus features displaying a second video (usually SD) on top of the second one (HD).

The bit stream processor can accelerate the first and only step of the video decoding that takes the VP@ in charge: the entropic decoding. However, be warned, this is limited to the H.264. According to Nvidia, current CPUs are actually powerful enough to carry out the entropic decoding of VC-1’s VLC. This confirms the results of our tests. However, the ATI Solution is still advantageous for those of us with slower PCs and for anyone looking to minimise their power consumption. The AES 128 bits decryptor chip is necessary for the AACS standard of HDCP decryption. The basic idea was to render the data unreadable every time a protected video flux must pass by a bus accessible to the user (like the PCI Express). This chip did not accompany the PureVideo until now, which meant that only a small minority of NVidia cards today display the HDCP certification, the chip needing to be added to the PCB of the graphic card.

Cards containing PureVideo 2 HD are the middle and low range Geforce 8: 8600, 8500 and 8400. However Nvidia recognise that the 64 bit memory bus of the 8400 should have rendered those incapable of reading 1080p flux in a fluid manner. On top of this, the Geforce 8500’s VP2 performs less well than those of the GeForce 8600.

Here again we see that its very useful video functions are not implemented in the brand’s high range GPUs Geforce 8800 GTX and GTS. As with ATI, these are as limited as the Purevideo of the Geforce 7. They handle the calculations linked to the decoding and the post treatment of the flux videos MPEG2, H.264 and VC-1, except the operations of entropic decoding and the DCT. We’ll see to to what degree they’re hobbled in our tests.

A quick glance towards laptop cards: the Geforce 8600M GT, GTS and 8700M GT are the only ones to possess PureVideos 2 HD full options, the Geforce 8600M GS and 8400M GT and GS seem to be lacking on the side of post treatment of MPEG2 flux. On the other hand they are thankfully equivalent for reading MPEG4 flux.