HD DVD and Blu-ray both support content encoded in one of three formats â€“ MPEG2 â€“ the format that is used on DVD - though obviously at much higher resolution, MPEG4 AVC, also known as H.264 â€“ a highly processor intensive codec, and VC1, the industry name for Microsoftâ€™s Windows Media Video 9.
H.264 HD content has been available for some time at the Apple web site in the form of movie trailers encoded in H.264. Without hardware acceleration itâ€™s been impossible to play the 1,920 x 1,080p resolution trailers without dropping frames even on systems fitted with top-end CPUs. Since release 80 of nVidiaâ€™s ForceWare drivers however, nVidia has been able to offload a huge amount of the processing off the CPU and on to the GPU. The result is completely smooth playback of the 1080p trailers without dropped frames, which is very impressive to see.
However, playing back content from HD DVD is more demanding, even with the less intensive MPEG2 and VC1 formats. This is because the content is encrypted using AACS (Advanced Access Content System), which thanks to a 120-bit key is designed to be harder to crack than the DCSS key used on DVD that fell relatively easily. Time will tell if thatâ€™s the case but at the moment if adds a lot of work for the CPU. If the CPU also has to spend cycles processing the picture itself and handling the software player then the result is dropped frames.
When nVidia announced that it could hardware accelerate H.264 decoding on its GPUs it claimed that even a 6600 GT could handle 1080p H.264 content. This contrasted well with ATIâ€™s Avivo, which specified at least an X1800 to do the same, as ATI used its pixel shaders to do the processing. However, when the AACS encryption is taken into account this minimum requirement goes up to a GeForce 7300 running at at least 500Mhz. A 7600 GT is preferred and you can get these passively cooled â€“ perfect for a media PC. In any case, there wonâ€™t be any 6xxx series cards with HDCP support so the point is moot.
The test system that nVidiaâ€™s Scott Vouri put together was powered by a compact Shuttle PC powered by a Pentium D 820 with the graphics card provided by a MSI 7600 GT featuring HDCP, which should be available in the UK soon. Other brands will undoubtedly follow soon and weâ€™ll be getting one from Asus in next week.
The first nVidia graphics card featuring HDCP was a GeForce 7950 GX2, which would be prohibitively expensive for many and overkill for a media PC so itâ€™s good to see it coming down to a more mid-range product. Scott stated that most board manufacturers would offer a single HDCP variant of each of their range rather than make it standard on all cards. This is because it would be a cost option, as to have an HDCP chip on the board adds to cost and nVidia has to pay a licence to use it â€“ a cost thatâ€™s then passed on to the board manufacturers and then consumers. (Thanks Hollywood).