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VGA, RGB, and all the rest

Discussion in 'Plasma TVs' started by jpd2, Mar 26, 2004.

  1. jpd2

    jpd2
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    Hi all

    Getting closer to parting with my hard earned cash on an Hitachi pd5000, but am concerned and confussed over all i have read on this excelent forum about different connections etc.

    I am going to connect up to a Telewest cable box and Aiwa home cinema with a S-Video output. We will use this to replace our TV.

    Where I am confussed and would appreciate some laymans explanation on is all the talk of connecting up by RGB, converters, VGA etc etc etc and how and why this would be better.

    whilst 2.5K represents good value from RS for this panel, I can't afford an endless amounts of upgrades just to get a decent picture, but whant to understand how I can connect up for the best PQ and useability

    Thanks
     
  2. salacious

    salacious
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    Sky and DVD signals are encoded using a MPEG-2 bitstream which is digital component video. When it is displayed on your screen it is in RGB format and a conversion needs to take place between these signals. It would be best if this is done with the minimum of loss. S-Video combines the U and V of the component signal (also called Pb and Pr) together and composite combines all three (YUV/YPbPr). Obviously if you combine signals together and try and seperate them afterwards you wont get the best quality signal that you could get if the conversions never took place.

    From the above you can see that RGB and component should be the best quality signals, followed by S-Video and lastly composite. Some screens can accept interlaced RGB (from SCART) signals into the VGA socket (the horizontal frequency is 15.5kHz) with some processing of the syncs so that the screen can lock to it. If your screen doesn't accept this type of signal then you are best to go down the component path.

    Brian
     
  3. jpd2

    jpd2
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    Brian, thanks for the reply. As a total newby I am still confussed by this section of your reply, any chance you could explain further.

    many thanks for your patience

    John
     
  4. salacious

    salacious
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    Standard computer output is sometimes called RGBHV where you have seperate horizontal and vertical syncs and are 5V signals. SCART uses RGBs where the horizontal and vertical syncs are combined together and are only 1V. What most of the convertors do which plug into the VGA port is to split the sync and produce a compatible computer signal.

    The problem that you can still have with the screen is that the horizontal frequency of TV is 15.5kHz where most computer modes start at 30kHz. Not all screens can lock to this type of signal e.g. Panasonic, Pioneers, Toshiba, Fujitsu, Sony do work but NEC, Daewoo, Philips, Hitachi and LG have problems.

    Component video has always been designed for this use and doesn't have the above problem. Although you can get other problems with progressive scan especially with PAL but you hadn't asked about that ;)

    Brian
     
  5. symanski

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    There's a guide to connecting up plasma screens on my website, it should help! Just look in the Technical section.

    I don't think the Telewest box outputs S-Video, only RGB via SCART. Not sure if your screen has SCART inputs, if not the best alternative would be Component (YUV / YPbPr) video. Again, have a lookg at my guide and you'll see how this gets hooked up.

    All the best,

    Dr John Sim.
     

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