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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 6th Oct 2006, 6:12 pm   #1
Kat Manton
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Default FotH TV System - X Modelines

Hi,

I've spent some time studying the open-source version of the nVidia driver to find out how the pixel clock frequency is derived from the 27MHz reference oscillator.

What I've come up with is a little program which simulates this, so allowing me to find pixel clock rates which are possible. This, in conjunction with a spreadsheet bordering on the incomprehensible means a lot of the guesswork's taken out. Modelines I've calculated work as expected.

I've also been playing with the vertical sync timing and found that specifying an odd number of lines gives a something-and-a-half line long sync pulse which seems to keep the timebase of the sets here happier, and I get interlace for once without having built the PLL SPG.

So, here's two modelines for those experimenting with this to play with:

First, a new 405-line one:
Code:
Modeline "664x377i" 8.10  664 680 752 800  377 378 385 405 -hsync -vsync interlace
And, for good measure, the 819-line one I was using with the Sondyna the other day:
Code:
Modeline "1152x738i" 29.3203  1152 1168 1240 1432  738 744 745 819  -hsync -vsync interlace
I'm still playing around with these; among other things I've yet to make my mind up whether I prefer an odd number of active lines or do as is done with 625-line and round it up to an even number (576).

I'll tidy up the /etc/X11/XF86Config-4 file with these and others in and upload it somewhere; that means all you need to do is get KnoppMyth installed and running on a suitable PC, build an RGB combiner, download that X config file and uncomment one line at the top of the file for the standard you want and you're in business.

Regards, Kat
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Old 6th Oct 2006, 7:22 pm   #2
Sean Williams
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Default Re: FotH TV System - X Modelines

Hi Kat,

Erm, Thicko here still is unsure how to put these instructions into the system - No real rush, as have yet to test the RGB combiner - Might get it finished this week.....

Cheers
Sean
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Old 6th Oct 2006, 7:36 pm   #3
Kat Manton
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Default Re: FotH TV System - X Modelines

Hi Sean,
Quote:
Originally Posted by m1ecy View Post
Erm, Thicko here still is unsure how to put these instructions into the system
All will become clear, presently

Once I've tidied up the file the modelines live in, I'll upload it; then all you need to do is download it, shove it in the right place and uncomment one line in the file to select which TV standard you want.

I'm also going to download the latest KnoppMyth release and perform a 'from scratch' installation, writing up instructions as I go. I'll post this as a "HOWTO" in here.

I might even explain how modelines work as well; it's pretty simple when you know. Working out ones which produced correct timings was a real pain in the proverbial until I found out how the pixel clock is generated.

Regards, Kat
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Old 6th Oct 2006, 8:30 pm   #4
Sean Williams
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Default Re: FotH TV System - X Modelines

Cool!

Finish RGB combiner = Metalbashing time!

Cheers
Sean
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Old 6th Oct 2006, 9:55 pm   #5
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Default Re: FotH TV System - X Modelines

Kat,

have you tried a "dual head" system yet with the GeForce? for example, 625 on the S-Video port and 405 on the VGA. I'm thinking of a pair of Sony 9-90's, side by side........

Jim.
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Old 12th Oct 2006, 1:35 pm   #6
Kat Manton
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Default Re: FotH TV System - X Modelines

Hi,
Quote:
Originally Posted by jim_beacon View Post
have you tried a "dual head" system yet with the GeForce? for example, 625 on the S-Video port and 405 on the VGA.
Not yet... I haven't got a plug for the S-Video socket...

Further updates to my progress...

I now have a modeline for 441/30; based on the information kindly posted in this thread. Switched to 525-line the Pye monitor locked to it after tweaking the horizontal hold. Playing back a Region 2 PAL DVD gave watchable pictures with some juddering when the camera panned or something moved across the frame; but it's still watchable. This is why I tried a 60Hz standard - I wanted to see how the system coped with frame-rate conversion. It does quite well, really.

This raises an interesting point - if you play back NTSC DVDs then the 60Hz standards should work well, with no juddering; likewise the 50Hz standards with PAL DVDs. So theoretically, wherever you are, by buying DVDs in an appropriate standard you can watch rather good pictures on old sets. I still need to confirm this, I've not got any Region 1 DVDs at the moment.

Anyway, once I've worked out a lot more modelines I'll pass the X configuration file on to Jim so there's somewhere to download it from.

Some of them involve a bit of guesswork on my part due to lack of information; I can get the line and frame rates very close; sync timings might be off a bit but those are easy enough to tweak - the hard part is getting the basic timing right. As more information becomes available I can revise the file and release a new version.

If anyone has any more detailed timing information for any standards I'd appreciate it, please add it to Obsolete Standard Details Wanted or PM me for an email address to send large pdfs etc. to. If it's not covered here or in that thread, assume I've not got details.

Cheers, Kat
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