This is the CPU usage when decoding VC1 content.
NVIDIA has shown off H.264 video decoding using its GeForce cards for the first time, today.
We were able to watch a GeForce 7800 use its GPU processing power to decode 20mbit, 1080p high definition content encoded with the H.264 standard. With the GeForce running at full throttle, CPU usage was throttled back to below 50%.
NVIDIA took some time out to explain their strategy for high-definition decoding - a strategy which will click into place in just a couple of months, with the release of ForceWare version 85.
H.264 is the codec used by both Blu-Ray and HD-DVD, and at a high bitrate such as 20mbit, most CPUs struggle to decode at full speed.
The GeForce video engine
GeForce 6 and 7 GPUs all have a video engine built into them. The engine, powered by the PureVideo software, will get an upgrade in ForceWare 85 that will enable the H.264 decoding. Most GPUs from the 6600GT and upwards will be able to handle full bitrate, 1080p content, according to NVIDIA.
The quality of the acceleration depends directly on the speed of the GPU. At 300MHz, the acceleration is going to be minimal. As you scale on up towards 500MHz GPU clock speed, acceleration gets to the point where less than 50% CPU is being used to deliver full speed playback.
This is different from ATI's Avivo technology, which decodes H.264 video on Radeon X1000 series cards. Avivo uses pixel shaders to decode the video, and this places a limitation on what cards can handle what resolutions. The X1300 can handle 480p H.264 video, the X1600 can handle 720p and the X1800 can handle 1080p.
In contrast, the integrated graphics chipset GeForce 6150 can handle 720p, whilst 6600GT, 6800, 7600 and 7800 cards can all do 1080p.
Because the PureVideo update in ForceWare 85 is backwards compatible, it means that existing users will be able to upgrade to this functionality. Since the video codec is being used in HD-DVD, NVIDIA were able to demonstrate a notebook using GPU acceleration to deliver HD-DVD, which we've shown you below.
The new version of PureVideo will also hardware accelerate VC1, the codec powering Microsoft's WMV HD.
We can't wait to get our hands on ForceWare 85 and start doing some direct comparisons between the new PureVideo and Avivo. Until we do, why not let us know what you think of this news over in the discussion forum?
Left: A Toshiba Quosimo laptop with a 7800, decoding HD-DVD. Right: a 1080p H.264 stream being accelerated by a 6800GT.