Seeing Pixels? Video Resolution and Scaling Explained

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All monitors, TVs, and other video displays are physically built with a set number of pixels. Screen resolutions are the number of pixels in a display. For example, common widescreen computer monitors have a resolution of 1680x1050 and common HDTVs have a resolution of 1920x1080. The first number is the number of columns of pixels and the second number is the number of rows.

Here are some common video resolutions:

Standard definition video:
640x480 or 720x480

High definition video:
1280x720
1920x1080

Scaling is what is done when your video source resolution doesn't match your display's native or physical resolution. If you have a video running in standard definition, something like 640x480 and you want to display it on a screen that is a higher resolution like 1920x1080 the image needs to be scaled to fit the display. The image is taken from having 480 rows of pixels and making it have 1080 rows of pixels and the number of columns is adjusted proportionately.

If scaling wasn't done the video would only fill up a small portion of the larger screen. It would still only take up 480 out of the 1080 rows of pixels. Scaling is done all the time without us even thinking about it. Computer monitors and HDTVs have built in scalers to scale any signal that isn't sent at the display's native (generally maximum) resolution. If they didn't we'd run into a lot of problems like the one i just mentioned.

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For example, say you are viewing a regular DVD or a standard definition TV signal on an HDTV. Both the DVD and the standard definition TV signal are going to be a 480 signal (640x480 or 720x480 for a widescreen DVD). If your TV didn't have a scaler, the video signal wouldn't fill up your nice big HDTV. What your TV does is take that lower resolution signal and it scales it, effectively stretching it to the 1920x1080 resolution (or whatever resolution your TV runs) so that it can fill the entire screen.

If you've ever changed the resolution on your computer to a lower resolution, your computer monitor will do the same thing. It will scale it to fill the entire monitor.

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This has to be done because there are a set physical number of pixels in the display and the image must be scaled to that resolution to be displayed properly.

Scalers can be very helpful if you have several video sources and you want to run them all through a single connection on a display. Also, they are often used when your source signal resolution doesn't match a resolution supported by your display.

A scaler by itself does only this. It is not designed to improve the picture quality of a lower resolution image or enhance it in any other way. When a lot of people talk about a scaler they are referring to a device that will scale the resolution as we've just discussed and also has an image processor in it to try and clean up the image.

The first thing to be aware of is if you are starting with a low resolution image you can never make it look as nice as an image that started at a high resolution. You cannot make your standard TV channels come through as sharp and with as much detail as an HD channel.

A video processor will run the video signal through often many complex algorithms that adjust the video signal to clean up bad noise and to try and sharpen the image. This will often help with the quality of the picture, but it will never be a substitute for true HD sources. Many HDTVs these days have some form of image processor in them to perform these functions. The same standard definition TV signal may look better on one TV than another because of the type of image processing that is done within the TV.

If you want to squeeze the best quality you can out of your standard definition sources you would want to use a nice video processor and scaler that can clean up the image before sending it to your TV.