Video converters, at their most basic, convert and reformat signals from one video interface to another type of video interface, such as ones that enable you to display VGA computer video on an NTSC or PAL TV. Basic video converters are neither scalers nor scan converters. This means that the resolution of the video signal at output is the same as the input signal, which can be a problem if you’re trying to send PC video to an HDMI enabled display. Therefore, if you set your PC at a resolution of 1024 x 768 (XGA), your display may not show the HDMI image. In this case, you have to set your PC’s resolution to either 640 x 480 at 60 Hz (VGA interpreted as 480p), 800 x 600 at 50 Hz (SVGA interpreted as 576p), 1280 x 720 at 60 Hz (WXGA interpreted as 720p), or 1920 x 1080 (1080p).
A scaler is a device that samples an input signal and scales it up or down to a resolution and timing suitable for the display. A scaler may optionally also convert the signal to a different format. A scaler that downscales video is sometimes called a scan converter.
Scalers are particularly useful when you want to connect different analog and digital equipment for output on a common display, such as in a presentation environment where you don’t want to fiddle with controls to get the picture right. All you do is set the output resolution to match the native resolution of the connected display.
Scalers that support switching take this concept further, enabling you to electronically switch video inputs and letting the box automatically make the necessary adjustments.
Usually, the scaling involves “upconverting” the signal. This is a process where the number of display pixels is mapped and adjusted to accurately match the resolution of the newer display. Deinterlacing technology with advanced motion compensation intelligently scales the source signal to the desired resolution with virtually no artifacts or distortion. In addition, scalers often perform frame rate adjustments so the proportion of the image isn’t resized incorrectly.
There are other products that scale images for larger displays and enable you to manipulate and rotate images on multiscreen video walls.
EDID Ghosts and Emulators
Ghosts can be handy tools to solve problems with certain combinations of video sources, distribution equipment, and displays. Display Data Channel Extended Display Identification Data (DDC EDID) is the data that tells your computer’s graphics card what characteristics your monitor/display has, such as resolution, color depth, digital pixel mapping, and more. The monitor automatically sends the DDC EDID straight through to the computer. But, sometimes, when you put a device, such as a KVM switch, between your monitor and computer, the data is not passed through. The result can be blank screens, boot problems, as well as resolution and color issues. In these cases, use a ghost. A ghost will store the data from the display and pass it on to the graphics card.