TTL RGB ==> PC

John C. Ellingboe john at guntersville.net
Mon Nov 5 19:04:34 CST 2007


Jules Richardson wrote:
> Hiya,
> 
>> First, have you tried Linux with tvtime and a boring old analogue BT878
>> capture card? 
> 
> 
> I think I've tried three different BT878-based TV cards in Linux - I've 
> only ever got one of them to semi-work (despite them working in Windows 
> - albeit at awful quality and in a tiny little window on the desktop 
> that makes them next to useless anyway). That's against a TV signal too 
> - I've heard from several sources that TV cards have a real problem with 
> the modulators used in typical 8-bit micros (UM1233 etc.)
> 
> The Linux code for TV cards seems to be something on an undocumented 
> mess :-(
> 
> It seems like a lot of unnecessary complexity to go TTL->composite->RF 
> and then back to digital again, too.
> 
>> Also does it have to be attached to a PC? You could try adapting the RGB
>> output to a PC VGA monitor directly.
> 
> 
> No, I don't need a PC. I just need *something* in the US that can cope 
> with typical UK-style picture formats (typically 'home' micros in the UK 
> will be designed around PAL signals at 625 lines interlaced I expect, 
> whereas I expect US micros of the 80s were geared more toward NTSC 
> displays of 525 lines)
> 
> I'm not sure if VGA will cope either - I don't think a typical VGA 
> monitor will sync down to the frequencies involved (i.e. converting TTL 
> to the necessary 'analogue' RGB of VGA is the easy bit :-)
> 
> Oh, sync lines on the machines I've got are typically composite, so some 
> sort of sync separator would be needed too...
> 
> This just strikes me as the sort of project that people will have done 
> before, because monitors take up lots of space and because there's not a 
> lot of sense in going from a digital source to analogue and then back to 
> digital again.
> 
> cheers
> 
> Jules
> 
> .
> 

What would happen if you used one of the video cards that has 
the video in/out jacks and setup to input PAL video?  Most of 
those cards have quite a few options as to how they treat the 
video.  I haven't tried it but I would expect it to receive PAL 
format video input and display a usable picture on the PC  screen.


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