A Quick Look at HDTV Overscan Compensation

“It has been a while since ATI released their HDTV dongles, which provided HDTV output support for most of their Radeon line. In fact, we probably first experimented with their HDTV dongle back in July or August of 2002. Back then, HDTV output support was plagued by the overscan issue.

And for those of you unfamiliar with “overscan”, it is simply the part of the picture that is cropped. Depending on whom you ask, others also describe it as the space that bleeds or “scans” beyond the edges of the visible area of the screen. Typical televisions can have a loss of up to 20% of the image due to cropping. This portion of lost image is what is commonly known as overscan. Technically speaking, the information of the “lost picture” is not actually lost, but it is outside the range of the visible area of your TV screen. A similar situation on the computer end is when you view a picture in 100% scaling on a monitor with a lower set resolution than the picture, i.e. a 1600 x 1200 picture in a 1280 x 1024 desktop environment. The difference is that on a computer, you can move the picture around to see portions cut off by the visible area of the monitor.”

Read the full article at Anandtech