There are obviously a number of codecs for HD video. The first is H.264, which is used by Apple for its high definition downloads, and by some upcoming HD-DVD and Blu Ray discs. The second is VC-1, which is the codec used by WMV-HD, used by Microsoft for HD content and by some HD-DVD discs. Both ATI and NVIDIA claim to accelerate both. Lastly, any existing codec can be utilised in a HD resolution - it's perfectly possible to have WMV or MPEG 2 encoded at at HD resolution.
H.264 is a pretty intensive codec. Because of the massive amount of compression it uses, whilst retaining fantastic image quality, it requires a lot of CPU speed to decode. The bigger the picture, the more speed. Content encoded at 1280x720 (720p) will require a fair amount of CPU time. Going further, content encoded at 1920x1080 (1080p) will require more CPU time than any processor available today is capable of giving it. Even on an AMD Athlon FX-62, you will see tearing and dropped frames when decoding 1080p content.
However, with GPU acceleration, the goal is to have spot-on H.264 playback with no dropped frames at any resolution, all whilst keeping the CPU load down to a minimum.
We tried some test files to find out what would happen. Due to the lack of HD content available at the moment, we had to use one of the only sources of content out there - film trailers.
is one of the 720p trailers available on the Windows Media Content Showcase
. Encoded in WMV HD, MSI's card was able to decode this without dropping a frame, with an average of 16% CPU utilisation, using Windows Media Player 10. The Sapphire card performed ever so slightly better, at 15%.
As an experiment, we tried the the WMV trailer for Miami Vice, the film of the 80s show coming out this summer. We ran this in Windows Media Player 10. It is encoded in standard WMV (rather than WMV HD), but has a 720p resolution and a high 8Mbit bitrate. Both cards were able to handle this without dropping a frame, with an average CPU utilisation of 14% on the ATI card and 17% on the NVIDIA card - plenty of headroom left for other tasks.
Our next test was a H.264 preview of rotoscoped stunner A Scanner Darkly
. This is the new film adapted from the Phillip K Dick novel - the chap that wrote the book that became Blade Runner
. It was downloaded from the Nero website
, and is 720p. We played this back in Cyberlink PowerDVD itself, and found that it was played perfectly with 5% CPU use on ATI and 4% CPU use on NVIDIA.
Finally, we pulled out the big one - a 1080p version of the sublime Serenity
, the Firefly
spinoff from Joss Whedon. This was the content we were unable to play smoothly on our FX-62. Downloaded from Apple's trailers site
and using Apple's QuickTime player, both cards were able to decode the video without dropping a frame - a rather amazing feat. Here, the NVIDIA card was clearly more capable, with 15% average CPU utilisation versus 25% on the ATI card. However, both these numbers are well within acceptable limits, especially given the non-playability without GPU acceleration. (Quick note: to get GPU acceleration working with Apple files, you need to rename them .mp4
rather than the Apple .mov
. Apple plays fast and loose with HD standards.)