Amiga.org
Amiga computer related discussion => Amiga community support ideas => Topic started by: on March 02, 2007, 05:41:29 AM
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Maybe this one should be in the hardware section... you tell me.
After looking into the technical information available on wikipedia about the nature of electric signals of the Amiga's RGB analog output (the totally non-standard DB-23 connector)and the technical information available about newer DVD's component output (known also as Y-Pb-Pr), it seems to me that it should be perfectly feasible and even easy to make a device that converts Amiga's RGB into a signal for component compatible TV sets.
Now, of course, that signal will certainly not be progressive (maybe, perhaps on AGA Amigas) but at least, you could get a very nice full color image without the need for some sort of flickerfixer or expensive dedicated Picasso-like card.
From what I understand, the only difference between the AMiga's RGB analog signals and the component signals is that the component signals convey the same information but using a differential scheme. The conversion should be easy to do using high speed differential video op-amps.
Is there such a device out there and if not, does anyone here have enough understanding of electronics to imagine how it could be done ?
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Use directly the VGA entrance on the new LCD/PLASMA TV it works 9 times on 10.
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by CLS2086 on 2007/3/2 12:38:57
Use directly the VGA entrance on the new LCD/PLASMA TV it works 9 times on 10
So what you are saying is..
You should be able to hook an Amiga directly to a modern LCD HDTV with a 15 pin VGA port? For some reason I assumed that a VGA connector would require a 31kHz signal, but maybe not.
Get a 23pin to 15pin adapter and connect that to a 15 pin to 15 pin VGA video cable. Then connect the cable to the TV and it should work? Anyone been able to verify this?
My 42" plasma doesn't have a VGA connector. It has S-Video, composite and DVI/Component inputs. But I wouldn't have an amiga laying around in the living room anyways. 20" LCD TV's are pretty cheap here in the US. I'd rather spend $300 on an LCD TV than $200 for a flicker fixer.
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You would need this (http://www.js-technology.com/product_info.php?products_id=36) (rather pricey) device to do the conversion.
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humppa wrote:
You would need this (http://www.js-technology.com/product_info.php?products_id=36) (rather pricey) device to do the conversion.
I don't understand why it has to be so expensive to do such a simple task. Perhaps this device is expensive because it is also compatible with progressive modes (31kHz).
However, in the technical information for this device is an information that could be used to create a much less expensive version.
Quote:
YUV is derived from RGB by the following equations:
Y = 0.3 R + 0.59 G + 0.11 B
U = 0.49 ( B - Y )
V = 0.87 ( R - Y )
End of quote:
Add the sync signals at the right place and that should be enough.
I took the monochrome composite outpout from my good old Amiga 2000 and plugged it in the Y channel of my Y-Pb-Pr TV input and sure enough I obtained an incredibly sharp monochrome display. Far better than if I had plugged it the composite input of the TV.
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hmmmmmm
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guru-666 wrote:
hmmmmmm
I don't agree at all.
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There are schematics on the net for folks who want to "roll their own"
This one for example (http://www.keohi.com/keohihdtv/interfaces/diytranscoder.html)
Just google for "RGB to component schematic" and you'll find several to look at. I've not built one myself, but have been considering it.
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humppa wrote:
You would need this (http://www.js-technology.com/product_info.php?products_id=36) (rather pricey) device to do the conversion.
Or this slightly less pricey version (http://www.keene.co.uk/electronics/multi.php?mycode=APT1) from Keene Electronics - I have one of these (not exclusively for Amiga use!) and it works well.
- Ali
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JimS wrote:
There are schematics on the net for folks who want to "roll their own"
This one for example (http://www.keohi.com/keohihdtv/interfaces/diytranscoder.html)
Just google for "RGB to component schematic" and you'll find several to look at. I've not built one myself, but have been considering it.
This plan seems generally good but this is still designed for VGA RGB and not for a 15.75KhZ RGB. It convert to 480p (progressive).
However, the resistors value allows for easy checking of the gain ratio.
It seems to be a good starting point.
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That particular plan doesn't do anything with the scan rates, so if you put the Amiga's TV RGB in, you should get TV component out. What would that be.... 480i?
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JimS wrote:
That particular plan doesn't do anything with the scan rates, so if you put the Amiga's TV RGB in, you should get TV component out. What would that be.... 480i?
Sounds like a fair assumption. However since the plan is said to convert VGA RGB into 480p component, is it electrically compatible with the Amiga's analog signal?
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not sure what you are asking about "electrically compatible with the Amiga's analog signal", anyway...
Conversion from analogic RGB+CSync to Y-Pb-Pr is not a matter of "few components and some resistors" and an equation (as you can see in a pic from that (http://www.js-technology.com/product_info.php?products_id=36) site)
Do you see how many components are required? (just to get the idea) impedance compensation, op- amp right PCB design/routing (to avoid intenference/diaphony reflections etc.
It costs too much? naaaa! you can spare something doing it by yourself? mhhh...prepare you to a great disappointment ;-)
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Framiga wrote:
not sure what you are asking about "electrically compatible with the Amiga's analog signal", anyway...
The scan rate from a non-progressive NTSC DVD player's component output is EXACTLY the same as that from an NTSC Amiga. Better, like I earlier said, when I hook up the monochrome output from my old Amiga 2000 to the Y channel of my TV set, I get a perfectly sharp monochrome image that seems just as sharp as the image I get when I hook up the Amiga's RGB output to the 1080.
Also, I made an experimental connector here.
I have a DVD player here and it has 3 component output modes. When I set it to RGB, and make some adapter cable from 3 RCA jacks to a DB-9 connector and hook it up to my old 1080, I get an image than can truly be qualified as being as good and sharp as the original Amiga quality. I didn't even have to connect the H-Sync V-Sync lines, the 1080 was smart enough to find these signals embedded in the RGB lines.
I am familiar with impedance compensation and correction. I am familiar with PCB design as I regularly use Altium DXP. Interferences and diaphony reflections may proove to be a problem but that remains to be seen.
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"I am familiar with impedance compensation and correction. I am familiar with PCB design as I regularly use Altium DXP. Interferences and diaphony reflections may proove to be a problem but that remains to be seen."
sorry but ... why ask over here if you already know it?
edited- just noticed that the above link is for a VGA to Y-Pb-PrTV (to no use for your needs)
or better ... you could attempt this way:
look for an AmigaRGB to VGA commodore adapter and the above mentioned VGA to Y-Pb-PrTV transcoder. It should works seen that frequwncies doesn't matters in this scenario.
How well it will works, "remains to be see" ;-) but if you have time and skills it worth a try.
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I am happy i live in Europe, where one can just plug it into the scart that is present all tvs 21" or higher after the 80s..
I really wonder why they never had such a input in usa/canada, considering that scart+rgb gives much better picture than svideo and composite.
I bet it would be easier to just get a pal tv set. Most newer pal tvs also support ntsc input, so that should be no problem either.
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It is perfectly possible to convert the Amiga's RGB signal to Y-Pb-Pr (component) video. Even if it is interlaced. It is then called 480i(ntsc) or 576i(pal). My panasonic television supports all formats (480i/480p/576i/576p/720p and 1080i) over the component input. The schematics posted here should work and can be made even simpler because of the sync signal. The Amiga puts out a composite sync signal that can be directly added to the component video. No need to adjust pulse widths at all! It should also work with AGA 31khz modes too. Just make sure the opamps used have enough bandwidth and drive capability.
Good luck!
Dennis
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Dennis wrote:
It is perfectly possible to convert the Amiga's RGB signal to Y-Pb-Pr (component) video. Even if it is interlaced. It is then called 480i(ntsc) or 576i(pal). My panasonic television supports all formats (480i/480p/576i/576p/720p and 1080i) over the component input. The schematics posted here should work and can be made even simpler because of the sync signal. The Amiga puts out a composite sync signal that can be directly added to the component video. No need to adjust pulse widths at all! It should also work with AGA 31khz modes too. Just make sure the opamps used have enough bandwidth and drive capability.
Good luck!
Dennis
I take it that as far as you know, nobody has actually done it before.
What I would really need is accurate timing and electrical specifications on the Amiga RGB signals and the same for the Y-Pb-Pr signals.
Assuming I can make a working prototype, the next big hurdle would be to find female DB-23 connectors.
I also assume, from what I read, that if the device easily converts NTSC Amiga RGB into Y-Pb-Pr 480i, then it should also convert PAL Amiga RGB into Y-Pb-Pr 576i without any switches or alterations.
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The neobitz http://www.neobitz.com/ seems to do just that but getting one of these appears to be quite difficult...
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Have I found the jackpot?
This plan : http://elm-chan.org/works/yuv2rgb/rgb2yuv.png
Was used to create this (jump down to RGB->Component converter) : http://www.freewebs.com/segasonicfan/arcadeworks.htm
Yesssss!