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    Help with Standard definition quality from newbie

    This is a discussion on Help with Standard definition quality from newbie within the Sky+ HD Supertelly forums, part of the Other Sky help and support category; Originally Posted by Old_nick The refresh rate of a pixel can be as fast as the manufacturer wants to make ...

    1. #11
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      Re: Help with Standard definition quality from newbie

      Quote Originally Posted by Old_nick View Post
      The refresh rate of a pixel can be as fast as the manufacturer wants to make it, but of course on an interlaced panel the picture information displayed by that pixel will only be refreshed with new pixel data 25 times a second. Don't confuse the difference between a pixel being refreshed and it being lit - it is only the information carried by that pixel which is refreshed. On the old scanning system using CRT's each picture element was scanned by a moving line which lit each pixel for an instant, and the system relied on the "lag" of the phosphors used in the display and the persistance of vision to avoid flicker effects. Modern displays have pixels which are almost permanently lit, (on plasmas they are switched on and off thousands of times a second, to give the pixel the correct brightness value). The refresh process is usually defined by the manufacturer, and is not usually adjustable.
      Thanks for the reply but still unclear about the process.
      You say each pixel is refreshed with new pixel data 25 times a second.
      Do you mean accurate pixel data (ie it waits for a full accurate full frame) or is each pixel refreshed with alternate accurate and guessed data 50 times a second.


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      Re: Help with Standard definition quality from newbie

      When the pixel data is sitting in a memory store, this can be read from as many times as the manufacturer wishes. So this data will be accurate for the frame being displayed. Obviously the store would need to be read faster than the refresh rate, otherwise it would lead to some very strange effects.

      Although interleaving was first used to combat the imperfections in the display electronics of the day when the electronic system was being developed, it is kept on today because it virtually halves the data that needs to be transmitted to give a satistfsactory picture, but in fast-moving scenes it can give the "feathered vertical" look, because a fast-moving object can move quite a long way in 1/25 of a second.

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      Re: Help with Standard definition quality from newbie

      Quote Originally Posted by sky-cards View Post
      Removed spam link - Newreader
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      Last edited by NewsreadeR; 07-10-09 at 07:57 PM.

     

     
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