Here again, if you're using a third-party video player, such as CyberLink's PowerDVD, you may want to use the applications' controls to manage video hardware. Most users, however, don't use sophisticated tools for viewing online or downloaded videos, so being aware of how the GPU control panels handle video is useful.
Both AMD and Nvidia offer controls for tweaking video playback color. Nvidia spreads its video color controls over three tabs: one for basic color, one for gamma, and one for advanced color.
If you aren't sure about what you're doing, proceed with care; Nvidia's control panels are sparse, and don't provide much guidance. Make changes in small increments, and be especially cautious about changing gamma settings. (Gamma alters the color tonality based on differences between video signals and human perception of color in a well-lit room.)
AMD's video color controls offer even more-granular control, though they replicate the controls you might see on an HDTV display. For example, presets labeled 'vivid', 'theater', and the like are available. Again, tweak on the basis of what looks pleasing to your eye, and avoid large scale-changes where possible.
Video quality settings let you deal with problems such as noisy video shot in low light. Both AMD and Nvidia offer tweaks for edge enhancement.
Nvidia's video quality settings are quite basic. You can set edge enhancement, noise reduction, and inverse telecine. Inverse telecine takes care of de-interlacing video; you may see this called "3:2 pulldown," which refers to converting film shot at 24 fps into 30-fps video--an operation that involves inserting extra frames into the video stream to maintain smooth video playback and maintain audio sync. Because video plays at various different standard rates in different places around the world, your GPU has to be able to handle a range of frame-rate conversions.
Nvidia's control panel gives you just the basics: de-interlacing, edge enhancement, and noise reduction. If your video player doesn't have direct hardware controls, you should enable noise reduction and inverse telecine. For most video, keeping noise reduction at around 25 to 30 percent is good enough.
In general, it's a good idea to avoid edge enhancement, as that option tends to introduce other artifacts, such as bright white edges around objects in the video. If you must use it for blurry video, then keep edge enhancement to a minimum.
As with color, AMD offers a much wider range of video quality controls, all built into a single, scrolling control panel.