Re: In search of videocard with variable screen resolution to 480i TV Output

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Tim Schoenfelder wrote:

Hi,

A friend (Its never the person writing the email right ;) ) is looking for a videocard that will display at variable screen resolutions ( 640x480, 800x600, 1040x780 etc) to regular NTSC TV Out (480i S-Video preferred interconnection) in such a way that would allow readable text on the TV. For instance, his ATI Radeon 9700 while displaying to TV output would not render readable text on his TV and it would not allow him to adjust the screen resolution. You can barely read it (Please correct this statement if he was using the card incorrectly..he was using the S-Video Output on it). You know that its there, you know where you're going so-to-speak but you can't see "squat". The reason for the text is to not have to have a monitor on top of the TV cluttering up the living room.

Any ideas as to what types of card(s) if any would solve this problem? (Links are welcome)

BTW, this card would be a solution to displaying Divx, Xvid type movies as played on a PC onto his TV as well as to eventually migrate the PC into a PVR system down the road ( eventually upgrading to HD ). Hopefully not too tall of an order...

Sincerely,
Tim Schoenfelder

Hello Tim,

I'm afraid that there's only a limited room for improvement on this unless your friend has a HDTV, which I doubt. The fundamental problem here is that a TV has a fixed frequency and resolution and regardless of what resolution the VGA card might be running, the resulting signal *must* adhere to this standard, and so gets converted on the way. For NTSC televisions, this locked in stone resolution is 480 rasterlines with 640 square pixels in each, updating at 2x30 Hz, or 640x480@60. It's not coincidental that this is the same as the "VGA" resolution which was standard for several years back in the early 90ies - it was based on the TV resolution. If you wish to display content on a TV, this is the resolution you should be using, as there's no resizing involved and so no loss of information. It is indeed possible to run both 800x600 and 1024x768, but all you achieve is that the signal is being sampled down on the way to the TV, and all text will look blurred since the resolutions aren't divisible by each other (1024/640 is not an integer number).

Of course, the explanation above does not account for overscan - other people can explain this better than me, suffice it to say that when you count all the lines that are outside of the visible screen as well you get 512 lines (I believe) and this corresponds to 'broadcast' resolution, where the picture has to be guaranteed to cover the entire screen.

So in conclusion, there really is nothing to do about the TV resolution except either buy an HDTV or a projector.

Cheers,

Ole




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