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guns1inger
So Very Tired
Joined: 01 Apr 2004
Location: Miskatonic U
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look it up in the glossary
_________________
The views expressed in this post are mine alone, unless plagiarised from others
Read my obscure DVD reviews here and my general blah here
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jagabo
Member
Joined: 09 Dec 2005
Location: none
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jman98
Member
Joined: 08 Oct 2004
Location: Freedonia
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| Beautiful Alone wrote: |
| Quote: |
| It's fully intentional. |
W.T.F? |
You may not like it, but jagabo is right. TV manufacturers do this DELIBERATELY. If they didn't, idiot customers would flip out when they saw the garbage that can appear at the outer edges of TV broadcasts and even some DVDs and complain that their TV was "broken" when in fact it was correctly displaying the video signal it got.
Note that some very good HDTVs do not have any kind of fix for overscan at all. I have a Samsung and it cannot be turned off. I did some research and found out that there is a firmware update for my TV that removes overscan ONLY on HDMI connections. If you apply this update, it actually increases the amount of overscan on all other connections. That's a losing proposition for me. I also found out that some people bricked their TVs when they tried to update the firmware, so I'll just live with overscan, thank you.
Some years ago, a few DVD players allowed you to actually choose underscan for the video output they sent to the TV and on those you would always get a full picture, but I don't know of any currently made DVD player that has such an option. I mentioned that once here and some guy responded that he thought that some player (I don't remember which) still allowed it, but he seemed to not really understand what we were talking about. I stand by my statement that to best of my knowledge no currently manufactured DVD player allows you to underscan the video.
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jagabo
Member
Joined: 09 Dec 2005
Location: none
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Some historical context:
Early CRT televisions could not keep the picture the same size, centered, and linear (barrel, pincushion, trapezoidal, and blooming distortions). As the TV heated up, as it aged, even as the picture content changed all these parameters varied. The solution was to mask the edges of the tube with a slightly rounded bezel. The outer 5 percent of so of the screen was covered up. If the picture slid a little to the side, shrank or grew a bit, or was slightly distorted you wouldn't notice because you didn't see all the way to the edge of the picture and there were no straight edges to hilite the non-linearity.
Broadcasters know that you won't see all the way to the edge of the frame so they don't put important information out there. This leads to the definition of the "action safe" and "title safe" areas. The title safe area should be visible on just about every TV, even those that are significantly out of adjustment. An advertizer would be very unhappy if their address or phone number wasn't visible to a large portion of thier viewers. The action safe area defines a larger area where you want to keep the main action. Some TVs may miss part of this but the information isn't critical.
Since broadasters know you won't see the outer few percent (on each side) of the frame they don't worry about noise or other garbage appearing there, or whether the picture data fills the entire frame. Closed caption data is transmitted at the very top of the frame. VHS and other flying head recording technologies have head swithing noise at the bottom of the frame.
Without overscan all these defects are visible. So even though modern technology has the ability to show every pixel of a broadcast, especially digital broadcasts and DVD, TV manufacturers continue to overscan.
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Beautiful Alone
Member
Joined: 07 Jul 2002
Location: United States
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This overscan thing just doesn't make any sense, video images doesnt have to be overscan inorder to be center and max out the tv, all it needs is the video content that is similar to the tv's aspect ratio and it would have a prefect match without having to see unwanted edges.
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jagabo
Member
Joined: 09 Dec 2005
Location: none
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| Beautiful Alone wrote: |
| This overscan thing just doesn't make any sense, video images doesnt have to be overscan inorder to be center and max out the tv, all it needs is the video content that is similar to the tv's aspect ratio and it would have a prefect match without having to see unwanted edges. |
If only you had been around in the 1940's to explain that to the TV engineers.
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Beautiful Alone
Member
Joined: 07 Jul 2002
Location: United States
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Well.. the 4:3 content we have been receiving over the air all these years matches our 4:3 tube TV's, what's the point of over scanning it?
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jagabo
Member
Joined: 09 Dec 2005
Location: none
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Read what I wrote.
It's a Catch-22 now. TVs overscan because there's crap at the edges of the frame. There's crap at the edges of the frame because TVs overscan.
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