This actually continued into the digital era, where early HD broadcasts especially live ones would show things in frame that shouldn't be mic stands, black bars on the edges of footage, etc. The problem is, there's very little reason you should have overscan enabled on your TV today, especially if, now that you've read this article, you're aware that very, very infrequently, you might see something on the edge of the screen that shouldn't be there.
So if your TV takes that image, and zooms in on it, it has to readjust every pixel to fit. It has to "scale" the image. Even if it does a good job at this, it can't be as good as just leaving the signal be. No matter what, an overscanned image will be softer and potentially noisier than a non-overscanned image.
Overscan actually loses you some of the resolution you paid for. Each TV company has a different place and name for overscan. I can't list them all, but I hope I can give you a few examples so you can find it on your TV. The most common setting name is called something similar to "Size. Annoyingly, once you find the control, the options aren't always labeled well. What you're looking for is 1x1 pixel mapping, which, as it sounds, maps each pixel in the source to each pixel on your TV.
Others TVs, like Panasonic and Sony, have an additional setting you must enable to get 1x1. On many Panasonic TVs, once you've enabled "Full" you also have to select "Size 2" in the settings menu to eliminate overscan. Is overscan a huge deal? For most people, no. This pushed the ugliness off the actual viewable part of the screen, giving a full picture and nice crisp edges. This process is shown in the two Norman Gunston frames on this page.
The first was taken directly from a DVD, but which actually originated as an analogue TV picture in the s. You will see that there are black bars to the left and right and a narrower one at the top. In addition, at the picture reaches all the way to the bottom on the left hand side, falls one scan line short in the middle area, and two scan lines short at the right side.
Clean edges were the result, at the cost of the loss of generally unimportant stuff at the edges. Instead of transmitting a wavering continuous analogue line representing a sequence of analogue scan lines, TV transmissions and DVD and Blu-ray video are handled as a series of frames constituted by a bitmap of pixels. These are encoded by a compression algorithm — then in the case of digital TV, sent over that wavering broadcast signal — but then reconstituted into their original picture frame format.
There are no scan lines as such any more. If the TV station or movie maker wants crisp clean edges to the picture then all they have to do is make sure that the picture entirely fills the frame. But in the world of consumer TVs, the practice of overscanning continues. Even many of the nicest, most modern 65 inch plasma, full high definition, 3D TVs have overscanning switched on by default - even for HD digital TV.
Why is overscan often on by default? Well, because a lot of content is made on the assumption that it will be shown on a TV that overscans, and so has been created with black borders to make sure that most of the picture ends up in the visible part of the screen.
This often happens on DVD movies, for example. In these cases, you can see that there are vertical black bars to the left and right of the picture. These account for about 2. On the Blu-ray versions, the picture stretches from the very left hand pixel to the very right hand one, edge to edge.
If you see an option to change the screen resolution, you can choose the one that matches the dimensions of your TV or projector. If necessary, check your TV or projector's manual to find the display resolution.
Some TVs and projectors let you adjust overscan or underscan from a settings menu or button on your remote. Look for a Zoom button or check your TV or projector for a menu called Aspect Ratio, presentation mode, computer mode, or a similar setting.
About overscan and underscan on your Mac, Apple TV, or other display Find out why content doesn't fit on your TV or projector and how to change overscan or underscan settings. Overscan Overscan refers to a cropped image on your TV screen.
Here are some examples: A setting on your TV zooms in on movie content, so that you can't see the outermost edges of the film.
Your TV's plastic border blocks some of the TV screen, so that you can't see the edges of the content.
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