What Is GPU Scaling For?

By John Lister

Higher resolutions, increased contrast and smoother playback mean computer graphics are getting ever more vivid and realistic. Most of the time, that is. If you're watching a basketball game and the point guards look more like defensive tackles on the football field, chances are the picture has been stretched and is in the wrong aspect ratio. GPU scaling is one way of avoiding this problem.

GPU Scaling Basics

GPU scaling is an option available in the configuration menus of many graphical processor units. A GPU is a computer processor dedicated specifically to generating on-screen images, which is particularly helpful when playing videos and games. GPU scaling rectifies a disparity in aspect ratio -- an image's width relative to its height -- between the image created by computer software such as a software application or game and the screen's resolution. GPU scaling is commonly used to take the output of an older video game designed for an era when most computer displays used a 4:3 aspect ratio and convert it so it fits nicely on a 16:9 screen without stretching the picture, often by displaying black bars.

Common Options

While precise options vary from GPU to GPU, the three scaling methods available on many AMD GPUs are good examples of common solutions. "Maintain Aspect Ratio" adds black bars either above and below or to the left and right of the picture, thus filling the screen without stretching the image. "Scale Image to Full Panel Size" stretches the picture to fill the screen completely, which means no space is wasted but the picture may look odd. "Use Centered Timings" is suitable when you have an image that's smaller than the resolution of the screen; this option doesn't scale the image at all, but places it in the center of the screen and surrounds it with black bars on all sides.

Underscan/Overscan

Depending on your screen, video source and GPU, you may sometimes see either black bars surrounding the image on all sides when you weren't expecting it or an image that is cut off because it extends beyond the edges of the screen. This occurs due to a mismatch somewhere in the process of your GPU analyzing and scaling the image. Most GPUs have a quick-fix setting in the configuration menu called "Underscan/Overscan" or something similar. Using this setting carries out the scaling as usual and then shrinks or enlarges the image just enough to get the desired fit.

Input Lag

Using GPU scaling requires more processing than simply displaying an image "as is" and therefore takes longer to process. Often the extra time amounts to just a fraction of a second and there isn't a noticeable difference when playing videos. If you are playing games, however, you may find the delay is noticeable and creates input lag, a situation where the delay between pressing a button and the resulting on-screen action disrupts your ability to act quickly within the game. In this case, weigh the effects of input lag against the effects of not scaling the image.