X-bit labs

NVIDIA GeForce 7800 GTX: New Architecture Exposed (page 4)

Category: Video

by Alexey Stepin

[ 06/22/2005 | 12:52 PM ]

New FSAA Modes

When developing the new processor, NVIDIA didn’t just increase the performance but also paid much attention to improving the image quality. So, the GeForce 7800 GTX has acquired new full-screen antialiasing modes. As you know, ordinary FSAA methods (super-sampling or multi-sampling) do not work on such objects as a wire fence or foliage on trees and those annoying jaggies remain on them, spoiling the whole picture.

From the technological point of view, the above-mentioned objects are usually very simple models consisting of several or even a single polygon; the pattern of leaves or wire is created with an appropriate texture. Since pixels inside a polygon are not smoothed out, full-screen antialiasing can’t help here. But the new antialiasing mode introduced by NVIDIA in the GeForce 7800 GTX can. This mode allows performing blending operations on transparent pixels, so the image quality in such spots is greatly improved. The information about the areas of the texture to be blended is taken from the texture’s alpha-channel.

The new FSAA method exists in two versions: Transparency Adaptive Supersampling and Transparency Adaptive Multisampling. The latter has a lower quality since it uses one texel sample instead of four to calculate a sub-pixel value, but it works faster. Combined with the higher performance of the GeForce 7800 GTX, the new antialiasing methods deliver an almost ideal image quality to the minutest detail.

PureVideo

One of the most interesting features of the GeForce 6 architecture was the special programmable video-processor called PureVideo which was to unload the system’s CPU in operations on video streams. The first version of this processor, available in the NV40, was originally disabled, probably due to some problems with the tech process. When they later turned this processor on, it transpired that the GeForce 6800 was equipped with the first version of PureVideo, without WMV HD acceleration, while the more advanced second version was available in the GeForce 6600. The second-generation PureVideo processor has the following features:

• High-definition MPEG-2 hardware acceleration. A dedicated 16-way vector processor enables smooth playback of HD video with minimal CPU usage.
• High-definition WMV hardware acceleration. Programmable support of the newest format enabled by Microsoft Windows Media Player and Windows XP Media Center Edition 2005 for fluid playback of WMV and WMV HD content.
• High-quality real-time video recording. An advanced motion-estimation engine makes it possible to record in real-time without a loss in quality.
• Spatial/temporal adaptive de-interlacing. Reproduces interlaced content from satellite, cable, and DVD feeds in full detail and without jagged edges or artifacts.
• 3:2 pull-down correction and “bad edit” correction (only on GeForce 6800 and GeForce 6600 GPUs). Restores video to its original 24fps film format.
• Flicker-free multi-stream scaling. High-quality 4-tap by 5-tap scaling maintains image detail, even when scaling a small video to a large area of the screen.
• Display gamma correction. Automatic format detection adjusts the color quality of video playback so that it is not too dark, overly bright or washed out, regardless of the display.

Only S3 Graphics can currently offer something like that, but its DeltaChrome and GammaChrome chips are rather slow in 3D. Of course, NVIDIA’s second-generation PureVideo processor was implemented in the G70, acquiring a few new interesting features by the way, so we’ve got a third generation of programmable video-processors from NVIDIA. Besides the above-enumerated functions, the PureVideo processor now supports the following:

• High-definition spatial-temporal de-interlacing
• Inverse 2:2 pull-down correction
• Seamless playback of high-definition ATSC and DVB MPEG-2 transport streams

These innovations refer to processing of HDTV content which becomes the more popular nowadays. By the way, you need Patch No.888656 from Microsoft in order to enable the acceleration of WMV HD decoding. You can download it here.