(1) A circuit that converts the resolution of a video signal to a resolution that is higher or lower. For example, an HDTV set can increase (scale up/upconvert) the standard 480-line resolution from a DVD or TV channel to a 720 or 1080-line resolution by filling in the missing lines via software. Although this may enhance the image, it is not turning it into true high-definition content, which must have a minimum of 720 lines to begin with.

Conversely, the image scaler in an HDTV set that displays only 720 lines of resolution (720p) can reduce (scale down/downconvert) a 1080-line HD signal to fit the screen's native 720 lines. See HDTV.

(2) The circuit that translates the image resolution coming from the display adapter (video card) into the maximum resolution of the display screen or flat panel. This is how different resolutions (640x480, 800x600, etc.) fill up the entire width and height of the screen. See LVDS.