[mythtv-users] (Non-interlaced) VGA to TV?

Stephen Williams stephen.gw at gmail.com
Wed Apr 12 22:58:42 UTC 2006


On 4/12/06, Malcolm Rowe <malcolm-mythtv-users at farside.org.uk> wrote:
> Hello all,
>
> This MythTV thing sure looks like fun - so I've spent the last few days
> trying to figure out how to build 'my first Mythbox' - a twin DVB-T
> tuner combined frontend/backend machine (I'm in the UK, hence the DVB-T).
>
> I've just about worked out what I need to do, with one exception:
> I can't work out how to get the video signal to the TV.
>
> On paper, the best choice for the graphics card appears to be a
> motherboard with an onboard Unichrome/Unichrome Pro chipset - they have
> decent open-source drivers (which in itself is fairly high on my list
> of priorities), and these drivers support Xv, XvMC (or enough of it),
> and OpenGL too.
>
> From what I can tell, the 'best' way to get the signal to the video card
> should be to run the video signal out the VGA port at 720x576i and into
> the RGB SCART connection on my TV.  That would require a little wiring,
> but would otherwise work great... except that the Unichrome chipset
> doesn't appear to be able to produce an interlaced output on the VGA port
> (I've not checked whether they can do the low refresh rate either).
>
> So the alternative is to run the signal out an S-Video port and simply
> connect that directly to the other (S-Video) SCART input on my TV.
> Also fine, except that the only Unichrome-based motherboards with
> S-Video output appear to be in Shuttle-style form factors, or laptops.
> I don't think I'm going to be able to stick two DVB-T tuners and a SATA
> drive (or two) into one of those cases, at least not without a serious
> cooling problem.
>
> So, my question is: assuming that I'd only have access to a VGA output
> (albeit at the right resolution - and possibly the right frequency -
> for PAL, apart from being progressive rather than interlaced), what's
> the best way to turn the signal into something that my TV can use,
> short of spending a ridiculous amount of money on a video 'processor'?
>
> Regards,
> Malcolm

If you're in the UK and want to use DVB-T (like me) then there's no
need to go for a Unichrome based motherboard. Everything you'll be
doing is SD, there's not going to be any HD over DVB-T in the
foreseeable future in the UK. You don't need anything more than very
basic onboard video, i'm using the MX440 built into an nForce2 based
motherboard.

I'm also using a home wired VGA to SCART converter, once you get it
working the results are as good as you can get without going to DVI or
component, certainly more than good enough for SD content.

As you've spotted, you need a driver that supports interlaced modes.
As look would have it the latest driver release from nvidia seems to
have fixed the outstanding issues with interlaced VGA output.

Stephen


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