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  1. Member
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    I was thinking the answer might be self-explanatory, since the overscan area is supposed to be the part of 525i that was not visible on a correctly set television, hence 480 instead of 525 visible lines going vertically...but then as I understand it, the vertical thin black bars at the edges of the video are the "outermost part" of the overscan?
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  2. Digitizing will capture the entire picture portion of the signal. It will exclude horizontal and vertical blanking. This has nothing to do with overscan.

    Overscan is a traditional way of displaying the picture that hides the edges behind the plastic bezel of your tv or monitor. This was to avoid showing the junk at the edge of an analog signal (active picture junk -- not blanking junk.) Sometimes the outer 3-10% of the active picture is referred to as the overscan area. Which means important action or titles should not be that close to the edge.
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    So then you are seeing the outer edge of the picture you wouldn't have seen on TV when you view it, say, with a default video player on a computer?
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  4. Originally Posted by 90sTV View Post
    So then you are seeing the outer edge of the picture you wouldn't have seen on TV when you view it, say, with a default video player on a computer?
    Generally, yes.
    Last edited by smrpix; 22nd Jul 2015 at 07:27.
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  5. The active picture in an analog broadcast is 485 scan lines (the top and bottom scan lines are half lines). So a 480 line capture is missing a few lines at the top and/or bottom (there used to be some capture devices that capture 486 lines). The rec.601 standard for digitizing analog video captures the active picture in 704 columns. Most capture devices capture a little extra on the left and right in case the broadcast or the capture device is a little off center.

    CRT TVs could not keep the picture centered and the right size. They also suffered from linearity problems. And these problems varied with temperature and age of the TV -- especially old tube based TVs. They were made less obvious by overscanning -- if you can't see the edges of the picture you are less likely to notice them. Of the 704x485 active picture area only the inner ~630x435 was visible on the screen of a typcial CRT TV. And visible portion was not always the exact center portion of the active picture. So the rule was to keep critical information within the inner 80 percent of the active picture area (the center 560x390 pixels). An advertiser would be upset if their phone number wasn't visible to half the viewing audience because it was too low in the frame.
    Last edited by jagabo; 22nd Jul 2015 at 09:59.
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    You know, they say there's "junk" in the overscan area and you probably wouldn't usually want to see it, but in looking at all kinds of transfers from the analog era, 90s and early 00s, I don't really see any junk in the perimeter. Maybe a very slight band of junk pixels, but it doesn't seem worth it to me to cut off so much of the image just to make sure that's not displayed on a CRT. For sports, TV shows, cartoons, etc. it seems it would only cut off actual surroundings. And for news broadcasts, the graphics are stretched a little, I guess to accommodate anyone who could see beyond the "safe" area. But nothing that would ever bother me as a viewer if I saw it. Just seems like such a waste to me for TVs to cut off such extreme amounts to prevent the possibility of seeing such little actual junk.
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    Originally Posted by 90sTV View Post
    You know, they say there's "junk" in the overscan area and you probably wouldn't usually want to see it, but in looking at all kinds of transfers from the analog era, 90s and early 00s, I don't really see any junk in the perimeter. Maybe a very slight band of junk pixels, but it doesn't seem worth it to me to cut off so much of the image just to make sure that's not displayed on a CRT. For sports, TV shows, cartoons, etc. it seems it would only cut off actual surroundings. And for news broadcasts, the graphics are stretched a little, I guess to accommodate anyone who could see beyond the "safe" area. But nothing that would ever bother me as a viewer if I saw it. Just seems like such a waste to me for TVs to cut off such extreme amounts to prevent the possibility of seeing such little actual junk.
    I know common sense right?

    Good luck in trying to convince stuffy old broadcast engineers of that!

    Folks, f.y.i. some people here talk about overscan as something from the past but unfortunately it is still prevalent and defended with verve by the die-hards.

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  8. Originally Posted by 90sTV View Post
    Just seems like such a waste to me for TVs to cut off such extreme amounts to prevent the possibility of seeing such little actual junk.
    Did you not read and/or understand jagabo's second paragraph above? It's not just the possibility of seeing some crap at the edges but (even more importantly, I would guess) the fact that the CRT televisions couldn't display the outer parts properly. I once got hold of a service manual for a CRT TV of mine years ago and managed to rid myself of the overscan. But the outer parts of the picture were 'warped'. That's the 'linearity' problem he mentioned. So I put the overscan back.

    Your captures or other videos originally from analog sources might look okay to you, but that's not how they would look on a CRT television without overscan.
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    Yeah, the "junk" explanation is usually given for why flat-panel display manufacturers continue to include overscan modes and turn them on by default, but that wasn't the reason overscan was originally used with CRTs. The junk in question generally being the white closed-captioning pulses that some broadcasters neglectfully include in their upscales of SD material.
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    I know the overscan settings depend on the TV, but does anyone know of which brands or sizes of CRT TVs tended to have more overscan? Less?
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    Generally, very old sets with very curved edges have more overscan than more modern (1990's and newer) sets but it is not related to brand or size of the screen. With old TVs the picture nowadays is often a bit shifted to one side and and needs re-adjustment.
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  12. My guess is most manufactures shot for 5 percent overscan at each edge, at room temperature, with the set warmed up, and displaying an average picture brightness. Then as the temperature changed, the components aged, and the picture brightness varied, the picture would change size and move left/right/up/down.
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    Seems Headline News only kept the bottom ticker within the "action safe" area as opposed to the "text safe" area?

    https://www.youtube.com/watch?v=N4FBnYMFloU

    If the bottom edge were set to 10%, the bottom team would be about entirely cut off.
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  14. Only critical information needs to be in the text safe area. The ticker isn't critical. Most TVs will display most of the action safe area. Only a few will be so badly configured as to cut off a large part of it at one or more sides.
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