Shocking discovery - Only ~85% of the actual view area is seen when watching DVD/VCD!

Discussion in 'Displays' started by WaterEC, Sep 14, 2005.

  1. WaterEC

    WaterEC Agent

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    My jaws dropped when I found this out accidentally. I just couldn't believe my eyes. I have been watching VCD/DVD for years, only to realize now that every time when I watch a VCD/DVD, I only see about 85% of the actual area! I'm reasonably knowledgeable with home theater system, but this completely knock me out.

    I have a 4:3 CRT TV, 27 inch Sony Wega to be exact. Last week I played a DVD video source with 4:3 aspect ratio on my computer, then play it on TV again from DVD player. All of a sudden I noticed that I can see more from computer than from TV. Basically, on every side (top, bottom, left, right), the computer shows about 4% more than the TV, which is a quite big margin. In other words, the width on TV is trimmed by 2 times the 4%, or roughly 8%, the height is also trimmed by roughly 8%. The total visible area on TV is only 92% x 92% = 85% of the actual area, compared to what you can see from computer! (I'm talking about the relative area here, not the absolute area. Of course the TV screen is much larger than computer screen).

    At first I thought it might be related to TV/DVD settings, but no matter what kind of display settings I use, I got the same thing. I have two DVD players, and they do the same thing. I asked some of my friends to compare this difference between computer and TV, and they found the same thing too.

    It's best to see this phenomenon with a video source of 4:3 aspect ratio, either VCD or DVD will do. You may also see this with Letterbox DVD, but it may be less obvious. I saw this phenomenon on 4:3 aspect ratio TV, but I'm not sure about HDTV, maybe HDTV won't have this kind of thing.

    Please try this and see if you see the same thing as my friends and I do. Any computer software will do, such as Windows Media Player, or Cyberlink PowerDVD. Please shed some light if you know anything about this. I'm really confused. Thanks!
     
  2. WaterEC

    WaterEC Agent

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    Forgot to mention that if your DVD player has a "Zoom" function. You can zoom out and in again and see this too. When you zoom out to, say, 50% or whatever percentage, you will find that you can see more relative area of the Video than the normal 100%. Again, please note that it's relative area I'm talking about, not absolute area.
     
  3. Philip Hamm

    Philip Hamm Lead Actor

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    It's called "overscan".

    Link.

    Link.

    Google "overscan" for more insight. If you get a professional in there to calibrate your TV or do it yourself using the service menu (again, use google), you can minimize it.
     
  4. rob-h

    rob-h Second Unit

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    You have to be careful trying to minimize overscan on a TV. You end up with what some people call "static" on the top lines.
     
  5. Kevin C Brown

    Kevin C Brown Producer

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    Yes, you need to adjust the overscan on your set. Mine is down to 3%, and I'm a happy camper.
     
  6. WaterEC

    WaterEC Agent

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    Thanks a lot guys for the information. Just wondering how do you find out about this? Do you know it as knowledge or do you find it out accidentally just like I do? I just read some links that Philip listed and I feel like novice to home theater again[​IMG]
     
  7. rob-h

    rob-h Second Unit

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    Its common knowledge. This is also the area that CC and other info is carried. This is what I meant by waht some people call "static". They put it there because with CRT's it was hidden anyway.
     
  8. Holadem

    Holadem Lead Actor

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    Classic [​IMG].

    --
    H - Sorry WaterEC, that was funny.
     
  9. WaterEC

    WaterEC Agent

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    Kevin, how did you adjust your overscan? I just downloaded a service menu of SONY, but didn't see overscan anywhere on the menu?
     
  10. ChrisWiggles

    ChrisWiggles Producer

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    It won't be labeled "overscan" it's just vertical and horizontal size. (and perhaps also position or phase if the raster is not centered).

    Overscan occurs when you set these options to obscure some percentage of the active picture areas to hide that noise and such that may appear on some material. Some overscan is usually fine, but you don't want too much. To determine this and adjust, use a geometry test pattern from Avia or DVE, there are even overscan test patterns that show how much % you are going over, including some that go right out to the edges if, for instance you are using a projector, that allow you to see if you are clipping or overscanning the image even by one pixel.
     
  11. WaterEC

    WaterEC Agent

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    Thanks Chris for the loads of information. This forum is awesome, with so many experts out there and willing to help, I'm thankful to all of you!
     
  12. Kevin C Brown

    Kevin C Brown Producer

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    What Chris said. [​IMG] I used Avia.

    One interesting thing I also found, overscan for my player and TV combo was *different* depending on if I used the component inputs or the S-video input. So make sure you adjust for what input you think is most important.

    I think it's really ironic too, they give us that control on a computer monitor, but noooooo, not on a TV display.

    Some professional/commercial monitors do give the user control over this.
     
  13. Rolando

    Rolando Screenwriter

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    I guess I will say it for anyone reading this thread who might be tempted to just go into the service menu after discovering they have overscan.

    DO NOT GO INTO THE SERVICE MENU.

    Ok now that I have scared the un-initiated what I really want to say is go in at your own risk. Do not make changes unless you feel comfortable tweaking around in there. remember there is a reason why these settings are not accessible to users. You could really mess things up.

    If you must go in write down ALL the original values. Better yet as someone suggested once, take a digital pic first.
     
  14. Jack Briggs

    Jack Briggs Executive Producer

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    Rolando posts excellent advice to a novice. Unless one is absolutely familiar with service-menu options, it is best advised to let a professional go into it to adjust the set's overscan.
     
  15. PerryD

    PerryD Supporting Actor

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    My Toshiba rear projection HD set also hides this in the service menu. I don't see how this could be that dangerous, especially if the manufacturers would give the user a way to make changes within a safely defined range in some sort of advanced menu rather than having it hidden away and called HSIZ/VSIZ or HPOS/VPOS, etc. The service menu on the Toshiba also gave you access to 56 point convergence, which again is vital to having a good image that the 9 point convergence in the regular menu lacked. I guess the danger would be if you messed up some of the other obscure settings.
     
  16. ChrisWiggles

    ChrisWiggles Producer

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    Because you can crank the size and push the image out beyond the tubeface overheat the glass and crack a tube. This is quite an expensive thing to fix, especially in those cases where an imploding tube sends shrapnel all over, perhaps at neighboring tubes or nearby electronics.

    I do recommend you use a pro to do this, or know well what it is you are doing in the service menu.

    A lot of professional displays have these and many other adjustments easily accessible because the folks using these displays presumably know what they're doing. Even still, there are unrelated things that can happen with size controls on different displays, you can overheat circuits etc etc.
     
  17. Rolando

    Rolando Screenwriter

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    Yes those are many good reasons not to. Yes many here have gone in without any trouble but once in a while I have seen threads with people literaly pulling their hair out trying to figure out how to "fix" a horrible mistake.

    The thing is there there is no "reset" function that will put it back the way it was and there are no 2 TVs (especially CRT) with the same settings accross the board.
     
  18. Jason Sweet

    Jason Sweet Stunt Coordinator

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    Is there a way to totally reset the set (service menu settings and everything) back to factory defaults?

    I was trying to fix a overscan problem on my Toshiba 36HF71 and my Xbox 360 and I may have bumped a color setting accidently. The picture looks darker and less vibrant.

    Is there a link to find out the original settings for this model?

    edit: I think Rolando just answerd my question. Is there no way to go back to defaults?
     
  19. John S

    John S Producer

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    Generally no way to go back to defaults.

    Wrtiing down or taking a digital pic is or should be mandatory. I'm a competent tech, and I do not go into the service menu. I can accept around a 5% overscan which is considered spec in all honesty. [​IMG]
     

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