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Newbie - Panel resolution & Scaling

Discussion in 'LCD & LED LCD TVs' started by SeeNoWeevil, Aug 26, 2005.

  1. SeeNoWeevil

    SeeNoWeevil
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    Hi there,

    Relatively new to the world of flat panel displays and have a few questions for you :lesson:

    Obviously an lcd screen has a fixed number of pixels, take for example a 1366 * 768 panel. If an image of different dimensions is to be displayed on this panel it needs to be scaled to fit the native resolution i.e 768 lines.

    So if fed a 1280*720 (720p) signal this would have to 'resized' i.e pixels added to make it fit the screen, correct?

    First question, what is the purpose of upscaling dvd players, if I feed a panel with 576i surely this would be de-interlaced and scaled to the correct size anyway. Wouldn't the upscaling player go 576i > 720p > 768p? Or am I getting confused?

    LCD's only show progressively right? i.e everything interlaced is de-interlaced?
    Does de-interlacing mainting the frame rate, i.e 1080i and 50 fileds per second that doesn't become 25 progressive frames per second does it?

    Also could someone explain overscan and the need for scaling with this to me? Is overscan a tv only thing i.e not dvd?

    Many thanks

    Dom
     
  2. Shakey_Jake33

    Shakey_Jake33
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    This is a difficult one, as you will get conflicting opinions as to whether it's worth it.

    Basically, it's very likely your upscaling DVD Player, assuming it's not a cheap one, will do a better job of processing the image and upscaling it.
    When your TV is then fed a 720p upscaled source, it's really a piece of cake for the set to upscale this to 768. Some people prefer to buy 1280x720 sets for that purpose, but it doesn't really make a difference.

    I can certainly say that picture quality is improved when I tell my Oppo DVD Player to upscale the image before sending it to the TV.
     
  3. SeeNoWeevil

    SeeNoWeevil
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    Thanks for that, kind of what I thought.

    So if I did get a panel, swapping my (expensive ish)576i player for a cheap upscaling player would not be massively worthwhile?

    Thanks again.
     
  4. pjskel

    pjskel
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    If you expensiveish player has component, then 576p is available to you. It all depends on the TV - some will have better scalers than other, or rather better written algorithms for scaling.
    The best thing you can do, is take your DVD player with you to a specialist store (maybe Currys/Comet might entertain you) and run the component into the TV you fancy. If they have an upscaling DVD player (Samsung 850/950 springs to mind) then try that, but remember you'll also be comparing analog YUV connection with HDMI digital, as that's the only upscale output (or DVI if not HDMI).
    By doing so, you'll be able to see which methodology provides the best looking images to your eyes - which will then determine if the current DVD player stays or goes.

    Also, some panels will allow for a 1:1 map of the input, but this will mean bars left/right/top/bottom and when scaled to fit 1366x768, you might notice no difference or even prefer the scaled result. It's a case of suck it and see!
     
  5. SeeNoWeevil

    SeeNoWeevil
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    Thanks!

    The player is RGB scart only so it will only output 576i. So I presume the tv will de-interlace and scale this to it's native resolution of 768 correct? LCD's can't show interlaced images can they?

    So the difference between feeding a panel a 576i input or a 720p will all display the same but picture quality will be determined by the how the scaling was done.
     
  6. pjskel

    pjskel
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    Pretty much spot on.
    LCD panels are digital, with each pixel having a corresponding address based on it's location. This is why DVI on you PC monitor looks crisper - 2 conversions from D-A-D being removed from the path.
    So, HDMI/DVI-HDCP should give you the same benefit, although since 720 is being remapped over 768, unless you can turn that function off in the menu, the difference won't be quite as noticable, I believe.
    With the a DVD doing the de-interlacing, then all the scaler needs to do is scaling.

    Seeing as current upscaling DVD players won't be able to replay HD discs, I'd have rathered they upscaled to the native resolution of the panel. Scaling an already scaled output can't be that great an idea - so I'd be more inclined (if the player provides it) to output 576p over HDMI and let the TV one do it's job solo.
     

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