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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 23rd Oct 2016, 1:14 pm   #1
rambo1152
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Default Generating 405 line video using a Windows PC

I’ve started a thread in the appropriate part of the forum about the restoration of this Cossor 918

This thread is about how I generate the 405 line programmes you see displayed on it.
https://youtu.be/T2oNculjoQc

Kat Manton did some work about 10 years ago with selected nVidia graphics cards under Linux, Jim Beacon was involved with testing and demonstrating the result, the project, known as FOTH tv, certainly worked, but a decade has gone by and most enthusiasts still prefer to convert from one obsolete television standard to our even more obsolete (but well loved) standard.

Now I am not criticising the system converters such as the excellent Aurora (desperately trying not to step on anyone’s toes here), what I am saying is that having the ability to output any stored still or moving image or indeed live webcam, from a PC at 405 (or indeed any other standard) is no small thing.

Anyhow, I chanced on a comment here discussing the FOTHtv project
http://forum.radios-tv.co.uk/viewtop...t=1973&start=0

near the bottom of that page Michael Watterson says,
“Allegedly there is a Windows driver!” and a link to:
http://www.geocities.ws/podernixie/h...deline-en.html


Allegedly? I needed to know one way or the other!

I had lying around a Dell Optiplex 780 with Windows XP Pro and an empty PCI Express slot.
I also had, from another machine, a dual-head nVidia Quadro NVS 285 graphics adapter.
So I put the card in, and installed the latest XP driver from the nVidia website.

I am thinking, if this works, I can have my primary monitor on 1280x1024 or whatever I choose, and an “extended desktop” on the 405 line set!

So I made a VGA to composite converter by cutting a VGA cable in half and splicing in three resistors and a capacitor:
http://www.geocities.ws/podernixie/htpc/vga2video.gif
If your source material is in monochrome you can omit the 100R, 150R, 390R & 20R resistors. To be honest you can’t tell much difference even with colour sources, but purists will want the correct RGB matrixing.

So, with some trepidation, I pasted Kat Manton’s 405 “modeline” into the WinModelines window.


Modeline "405i50" 8.10 664 680 752 800 377 378 385 405 -hsync -vsync interlace


and connected my crude adapter output directly to the grid of the video output valve of my newly restored Cossor 916 (I have yet to build a VHF modulator)

THE SET WAS OF COURSE POWERED VIA AN ISOLATION TRANSFORMER AND THE CHASSIS EARTHED.

I selected my secondary display in WinModelines and, with a little trepidation, clicked the little arrow...

Well, knock me over with a feather, it worked immediately, after twiddling the Horizontal and Vertical holds I had the Windows desktop wallpaper 405 line High Definition (if not HD).

But it gets even better.
If you’ve watched my Youtube presentation it is clear there is something else going on,
And it’s this, Combitech VidBlasterX Trial
http://www.vidblasterx.com/ It’s a full featured TV studio and runs on my normal monitor and outputs to the secondary 405 monitor.

It must be pointed out that VidBlasterX Trial is free-trial software, not free software. The licence terms are here
http://videoblaster.com/vidblasterhe...Licensing.html

The free trial period appears to be defined by this sentence only:
“It is therefore essential to take advantage of the Trial edition (equivalent to the Studio edition with all its features fully functional) so as to ensure that VidBlaster is suitable for your particular application before purchasing.”


OK, I may well have had a little luck on my side, especially having a spare PC, and what turned out to be a suitable graphics card, but this project was easy, bordering on the trivial, and I am left wondering why something like this is not being more widely used to serve pictures to vintage TV sets, especially museum exhibits.

Work to do.
On the computer that I am typing this I have a similar dual-head card, an nVidia Quadro NVS 290.
No doubt that will work in the XP machine, but WinModelines will not work on this Windows 10 machine, nor could I make it work with Windows 7 pro 64 bit.

I need to have a VGA monitor connected to both outputs when the PC boots, in order that both ports are enabled. This is a bit inconvenient, so I need to somehow fool card that two vga monitors are connected at bootup when there is only one real monitor. I tried by connecting the DCC data and clock pins 12><12 and 15><15 together on the 15 pin VGA interfaces. It looked like it worked as two monitors were showing in the nVidia control panel, but closer examination showed that the phantom monitor was detected as DVI not VGA. I’m probably going about this the wrong way. Any ideas?


Graham.
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Old 23rd Oct 2016, 9:29 pm   #2
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Default Re: Generating 405 line video using a Windows PC

Very useful stuff to know, thanks for posting. I too have always been surprised that the home PC hasn't played a larger role in standards conversion- they do everything else for us these days.
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Old 24th Oct 2016, 1:23 am   #3
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Default Re: Generating 405 line video using a Windows PC

Well quite, especially when you consider that the graphics card I am using is a few years old now, and can be had on Ebay for as little as £5.

There is nothing to stop you using the PC that you use for other "stuff" for this project, it doesn't have to be dedicated to it.

I wonder why I couldn't get WinModelines to work under Windows 7? the developer says it should work. I will email him and tell him what I'm doing with his software.
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Old 27th Oct 2016, 4:47 am   #4
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Default Re: Generating 405 line video using a Windows PC

Can also be done in Windows with PowerStrip and certain video cards I believe? Only with the paid version of PowerStrip though, not the trial version.
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Old 27th Oct 2016, 1:16 pm   #5
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Default Re: Generating 405 line video using a Windows PC

Interesting you say only the paid version. I was trying a few years back with the demo version without much success.
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Old 27th Oct 2016, 5:43 pm   #6
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Default Re: Generating 405 line video using a Windows PC

A bit of an aside as I am not immediately contemplating getting involved in this, although have given generation and conversion of TV waveforms some thought, but has anyone considered and have an opinion on using something like a Raspberry Pi for a dedicated system?
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Old 27th Oct 2016, 5:54 pm   #7
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Default Re: Generating 405 line video using a Windows PC

The Raspberry Pi isn't easy to create custom modelines for, unfortunately. The GPU is not thoroughly documented for mere mortals
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Old 28th Oct 2016, 8:51 am   #8
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Default Re: Generating 405 line video using a Windows PC

Thank you Julie

I have recently been getting back into this kind of thing (micros plus programming), but on comparing, although there seems to be plenty of processing power there, I sidelined the Raspberry Pi in favour of the Arduino. Far less power but more readily programmable for easier tasks.

I see a PC, as they would have it these days, not readily accessible as operating environments are generally designed to protect the unwary from screwing the system. There is also the issue of multitasking which does not help critically timed processes. That is why I mentioned it as it would be easier to use a dedicated device (at least in theory) Still I am probably preaching to the converted here.
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Old 29th Oct 2016, 1:23 pm   #9
dave walsh
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Default Re: Generating 405 line video using a Windows PC

I enjoyed the You Tube video Graham and reading about your innovative approach to Standards Conversion-"Cheap and Cheefull" perhaps?
I particularly liked the way you inserted yourself into a demonstration video, making it into a min program in effect! You told the story re discovering the Cossor and negotiating it's purchase, illustrated the restoration process and then set up a related thread re the convertor-all in one package really. Excellent

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Old 29th Oct 2016, 11:07 pm   #10
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Default Re: Generating 405 line video using a Windows PC

Bless your heart for saying that Dave, one only tries to do ones best.

As I mentioned, I was cheating because I hadn't built a modulator and I was just feeding the video directly onto the grid of the video output valve.
I have now completed a modulator, well the vision half anyway. Initially the set would not respond to it at all. The RF unit seemed to work OK when I first got the set going as it was picking up interference on vision and sound when I connected an aerial, but not now. The mixer/local oscillator stage was not oscillating and no prizes for guessing the culprit was brown Hunts 100pf
I've now got a bright picture from the modulator but with severe smearing and cogging. I don't have a scope or another 405 line set to see how much is due to the modulator, but for now I'm assuming all the similar condensers have given up the ghost and I am waiting for some replacements I've ordered.

Cheap & cheerful? Well perhaps. Cheap certainly, but cheerful implies a qualitative compromise has been made, and the jury is still out as to how the picture quality compares to (say) an Aurora. I don't see any reason why it should't compare favourably, although I have to say that I don't think I noticed any proper interlacing on my tests. It's something I will look at after I fix the outstanding issues.

Last edited by rambo1152; 29th Oct 2016 at 11:12 pm. Reason: grammar correction
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Old 31st Oct 2016, 5:24 pm   #11
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Default Re: Generating 405 line video using a Windows PC

I seem to recall getting a Philips N series and an old VHS VCR to play on a 405 line TV (they had switchable to VHF, tuners IIRC) ..not sure now what was going on in the modulator or if it had to be modified?
...but I might be rambling?
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Old 1st Nov 2016, 9:04 am   #12
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Default Re: Generating 405 line video using a Windows PC

Thats a great yoochoob video. Its rather spooky seeing an old telly showing modern images! Something downright Dr Who-esque about it.
You've done a good job technically though, well done.

D
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