[mythtv-users] TV Output

Stephen Williams stephen.gw at gmail.com
Fri Dec 17 09:31:15 UTC 2004


I have a very similar setup, DVB-T to a widescreen TV via a Geforce
MX. I agree, the native TV out of the vid card is a little
disappointing. Instead, quite a few people on this list (me included)
are using home-built VGA -> SCART converters. Don't bother trying to
buy one of these since they will all of the retail versions use scan
conversion which really lowers the quality.

Take a look at the following sites for details:

http://www.hut.fi/Misc/Electronics/circuits/vga2tv/
http://www.nexusuk.org/projects/vga2scart/index.php
http://www.sput.nl/hardware/tv-x.html  

Personally I went for the last site listed. This will give you RGB
output to the TV, you can just output the raw interlaced DVB-T signal
(no de-interlacing required) and each horizontal line of pixels
generated by your vid card will map natively to a scan line on the TV.

The image quality is fantastic, noticeably crisper than my Sony
set-top-box using RGB output. You might be able to tweak the S-video
output a little but it'll never come close.

Steve


On Fri, 17 Dec 2004 00:21:47 GMT, Tom Hughes <tom at compton.nu> wrote:
> My newly built Myth box is outputting DVB-T recordings to a
> widescreen TV over S-Video from a GeForce 4 MX card but the
> output quality seems to be somewhat lacking.
> 
> I using this modeline at the moment, which I found on the mailing
> list:
> 
>   ModeLine "720x576x50" 27.1 720 736 880 896 576 578 579 606
> 
> The 720x576 resolution matches most UK DVB transmissions, although
> some are 704x576 instead. I also have these options set:
> 
>   Option "TVOverScan" "1.0"
>   Option "TVStandard" "PAL-I"
>   Option "ConnectedMonitor" "TV"
>   Option "TVOutFormat" "SVIDEO"
>   Option "NoLogo" "true"
> 
> Note that overscan is turned up to the maximum value. I'm using
> the ATrpms 0.16 build of Myth and the 6629 NVidia drivers.
> 
> The first problem is that although the image reaches the right
> side of the screen it doesn't quite meat the left edge, and there
> are large gaps at the top and bottom.
> 
> The second problem is that the picture just isn't as crisp and
> clear as the output from my set top box. That is using RGB so
> will be a little better, but my DVD player uses S-Video and does
> better than the Myth box.
> 
> Finally there are strange motion artefacts, with are particularly
> noticeable on credits, especially horizontally scrolling ones but
> vertically scrolling ones also show it. Is this perhaps a frame
> sync issue? Do the ATrpms builds have OpenGL sync support turned
> on or not?
> 
> Thanks for any help people can offer,
> 
> Tom
> 
> --
> Tom Hughes (tom at compton.nu)
> http://www.compton.nu/
> 
> 
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