Amiga.org
Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: skurk on April 07, 2007, 09:48:10 PM
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Ok, I know this has been discussed before, but I haven't found any real info yet. And, it must be said, I have no idea what to expect here. :-)
So, does anyone out there have the schematics for a scandoubler?
I'd love to build one that slips into the RGB port. I can get my hands on most parts, and the price is not an issue at the moment.
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Those schematics are rather difficult to find. Depending on your electronics-skilss you could have a look at AverLogic (http://www.averlogic.com/dualport_sarm.asp?protype=Video%20Conversion%20ICs)
they provide a chip doing a part of the trick: Scandoubling. In front of it, you probably need some kind of RGB to composite conversion schematic. That part could possibly be handled by Motorola's MC1377.
So, if you can think of a schematic joining both chips in the correct way and make your design as such that you basically design a board meeant for the internal Video-slot (and build an converter such that it can be hooked to the external RGB) you might become a littlie hero ;-).
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I did stumble upon this one (http://starbase.globalpc.net/~vanessa/hobbies/projects/scandoubler-schematic-0.2.3.png), though. Looks plausible to my untrained eye, and the Amiga RGB port provides all the required input.
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If you want to plug in to the rgb port, you have to perform three tasks :
1 - decode the analogue RGB signal to digital (ADC)
2 - double the frequency
3 - convert the digital signal to analogue (DAC)
but, you can skip the first step if you use the digital signals directly from the amiga. For big box amigas, these are provided on the video slot. For desktop amigas you need some adaptors clipping on chips (well denise or lisa).
I asked this question before in another forum (http://eab.abime.net/showthread.php?t=25865&highlight=scandoubling) and got some valuable answers. You might want to check that.
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So, what are the chances of a schematic for a video slot scandoubler? :-D
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moto
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well, it shouldn't be too difficult if there were chips which handled the scandoubling. The averlogic chip seems good, but it says RGB 565 which sounds inadequate for AGA screenmodes. Though there are 8 bit DACs in the spreadsheet so I'm not sure if it actually performs real 8 bit scandoubling.
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This sounds like a job for Individual Computers. Jens are you reading this? :-)
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moto
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The big problem I have found with scandoublers is they get VERY hot. Why is this? It is because they do it in a rudimentary way to keep the cost down? If money was not a consideration, surely it wouldn't be hard to get a 15Hz signal, input it into a SVGA graphics processor and produce a 30+Hz signal?
As I understand it, your bog-standard scandoubler literally doubles the 15Hz signal, surely inputting the signal into another processor for output would keep the things from running so hot?
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What about these?
http://www.ramelectronics.net/HTML/video-to-vga.html
Couldn't they be modified in some way to take the signal from the RGB port?
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I already own a similar item (link (http://www.gadmei.com/new3/ProductShow.asp?ArticleID=136)) but the quality from the composite is horrible. Just horrible.
The ones with component sound interesting, though.
Are there any RGBI->Component cables/converters available? I think that, plus one of those component to VGA adapters would produce an OK picture.
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Hasn't this issue been thrashed over, ad nauseum? :-)
Best Scandoublers/FFs = plugged to chipset or built in (A3000) = horrendous price and zero availability!
Available Scandoublers/FFs = Mediocre performance, horrendous price.
LCD TVs = Cheaper than either the above, excellent performance and display.
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I use an LCD display for my A1200 see:
http://www.amiga600.net/temp/a1200_base.jpg
But! I cannot use it realistically any higher than Hi Res becuase of the flicker issue.
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Colin_Camper wrote:
Hasn't this issue been thrashed over, ad nauseum? :-)
Probably, but it never hurts to search for new solutions.
Component to VGA adapters are cheap on ebay, $15 and up. If it's possible to extract a component signal from the Amiga RGBI, then we have a decent and affordable solution.
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Hope this ends all nags
http://amigahardware.mariomisic.de/cgi-bin/showhardware_en.cgi?HARDID=1771
A 24-bit video slot scandoubler implemented using 2x A3000 AMBER deinterlacers.
http://www.gb97816.homepage.t-online.de/a2320_aga.htm
All the project files, schematics and CPLD code included
http://www.gb97816.homepage.t-online.de/download/a2320_aga.zip
countzero wrote:
The averlogic chip seems good, but it says RGB 565 which sounds inadequate for AGA screenmodes.
It's only RGB 16-bit (565) and only gives 16-shades of Red and Blue. Just like the DCE scandoublers Flicker/Scan Magic etc.
Though there are 8 bit DACs in the spreadsheet so I'm not sure if it actually performs real 8 bit scandoubling.
It doesnt. It only has 16-bit input, but 24-bit output. (It needs that incase you do Y'CbCr to RGB conversion.)
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So basically, now Clone-A is functioning, Individual Computers should now re-implement Amber? ;-)
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Has anyone done an english translation of the german pdf file yet? Failing that, is there a tool online that will do it? This looks like a great project, but I can't read the docs.
Thanks, Jeff
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Does an Amber card work on an A4000, or only an A3000?
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moto
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It looks good, but given that the amber chips are out of production I would not recommending all the A3000's in existance be butchered for the chips.
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I agree, however I already have enough spare parts around without hurting any good 3000's to build 1 board:-) So I may attempt it.
Jeff
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While we are slightly off-topic: Aren't there any VGA adapters for any game consoles that may be modified to fit the Amiga RGB port?
Playstation, Gamecube, Dreamcast, SNES..?
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yes, there are. the Xrgb and the CM-345S (http://www.amiga.org/gallery/index.php?n=1169=38) are the first to spring to mind. They equally (or more) expensive as the scandoublers.
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Are we saying that there are no chips in existence which can convert the video signals from the Video Slot to VGA?
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moto
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When fiddling with devices not intended for the Amiga, you'd have to distinguish between scan doublers and flicker fixers.
Simple scan doublers just buffer one 15 kHz line and output it twice at 31 kHz to make it VGA compatible. That's not what you want because you wouldn't get rid if interlace flicker.
Flicker fixers buffer a complete interlaced field and output the previous field in combination with the current one, thus producing a progressive output. OTOH, what you see is partially (the buffered field) already 20 ms older than the rest, which leads to ugly comb/shearing effects (http://en.wikipedia.org/wiki/Image:Interlace.jpg).
Wikipedia has a very good article (http://en.wikipedia.org/wiki/Interlace) on this.
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All Amiga' scandoublers have issues here and there except the one built it on the A3000 that works perfect cause it works through the amber chip that was specially designed for the amiga screenmodes
Other scandoublers or chips will work but with issues on the AGA palette or interlacing problems
I think that it's a waste of time try to build a home made scandoubler cause it will not work fine
That A2320 maybe works perfect even on AGA screens cause was designed with 2 ambers chips.....and is the only one that I wish built
but two A3000 required to built one of these
So....the best solution is a new LCD TV
bye
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So how does the 2320 eliminate the comb effect ? Does it manage to do it already in A3000's using interlaced screens at 15khz (i.e. 640x512)?
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Jose wrote:
So how does the 2320 eliminate the comb effect ?
It doesn't. Doesn't even try. Deinterlace interpolation with early 90's technology was out of the question.
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@Zac67
Ahh, I asked that cause some of you guys on this thread seemed to imply that it would be the perfect solution.. ( the A2320)
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@Jose:
The scandoubler/flickerfixer actually performed brilliant (especially when using a little slowish CRT monitor) in the Amiga 3000. The 'combing' effect was never a problem for me as the SD/FF was only flickerfixing while using Workbench (can't remember a single game with high-speed grafics in interlaced mode). Only the standard mouse pointer had to be replaced by some hi-res mouse hack. So, for your average dtp work, playing about with PPaint and stuff like that is was really usable.
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An A2320 / Amber board is probably the best solution you can get; only drawback with the original design is the limitation to 12 bit.
As to deinterlacing effects: for a computer's video output there's no definite solution to the problem. For a video (=camera) type signal there are some interpolation methods that work quite well - but a computer's output is very arbitrary and not predictable. E.g. fonts have to be reproduced very accurately to be easily readable. I doubt if there's a 'perfect' solution to this.
There are two workarounds for this problem:
- limit screen updates to 25/30 Hz - when both fields fit perfectly there will be no artifacts
- use a video card and get rid of this problem alltogether
OTOH what Amiga_3k writes is true: it's no real problem.
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I can't understand how anyone who owns the rights to this Amiga computer can go on doing business without addressing the video resolution problem. They leave it up to 3rd. parties but no one is interested in it.
Amiga needs a scandoubler, Flicker Fixer. A real one that works with all of the different hardware. We need a way of using modern resolution monitors. The 15 Khz resolution made for television was a different kind of idea at the time. But now its really getting old. We feel it because our monitors are really starting to show their age. We need a solution.
Software hut www.softhut.com had a solution called Toastscan. But they are not being made anymore. Software hut was trying to find someone to build them a new device to sell. Maybe you can contact them and they will turn you on to some business, if you have the talent required to build the thing.
There were some devices, made to convert RGB to VGA for Game consoles. Check this one out- http://www.tiptonium.com/videogames/reviews/other/XRGB2.htm
How about this one,
http://www.cypuk.com/cyp_techpage.php?product=228&&parent=0
or this one,
http://www.ihse.de/english/238-3f.htm
Then there is something called scart over in Europe. We don't see much of it here in the US, but some have reportedly had success using the input of a scart connector on new TV sets. Not quite SVGA resolution, but as good as some of our old monitors. No solution to flicker at some resolutions.
Amiga users were using them to circumvent the signal. None did the complete job all the time to my knowledge. I hope someone can prove me wrong and give us a solution.
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Then there is something called scart over in Europe. We don't see much of it here in the US, but some have reportedly had success using the input of a scart connector on new TV sets. Not quite SVGA resolution, but as good as some of our old monitors. No solution to flicker at some resolutions.
Er...any 0lder-TV will Always flicker. NTSC at best is 60Hz & PAL is 50Hz. Sit in front of a 100Hz TV for a few months. You wont stop griping about the flicker if you go back to a 50/60hz TV.
It's a bit like most folk saying they cant see the difference betweem 70Hz & 60Hz. Some argue you cant tell over 70 anyways! I certainly can tell the difference between 70Hz & say 85Hz. Its a huge difference to the Picture.
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Based on my experiences I think that it is rather accurate to say that the bigger the tube you're watching, the higher the refreshrate should be to create a solid picture.
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motorollin wrote:
Does an Amber card work on an A4000, or only an A3000?
The original AMBER A2320 works on all Big-box Amiga's but is limited to 12-bit.
Georg's A2320 AGA works at 12-bit in ECS/OCS Amiga's and 24-bit in AGA Amiga's like the A4000.
I know where I can located 30 Amber chips, but I cannot seem to get Georg interested in making anymore :-(
motorollin wrote:
Are we saying that there are no chips in existence which can convert the video signals from the Video Slot to VGA?
The problem is that full quality Digital Video is 16-bit in the Y'CbCr colourspace. The modern chips dont have more than 16 input pins on them. They support RGB but only with a 16-bit input (RGB 5:6:5).
If you didnt use an off the shelf chip you'd have to use an FPGA/CPLD which would drastically increase the costs.
You could make a 16-bit scandoubler/flicker fixer for video slots for well under €20 each, but who wants that?
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Would it be possible to combine two of those rather low-budget 16-bit chips? It should, in my theory, give 32 bit, giving 8 bit reserve.
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amiga_3k wrote:
Would it be possible to combine two of those rather low-budget 16-bit chips?
No that is not possible.
The reason you can use two AMBER chips is that they do not have on-chip video DAC's. Their output is 12-bit digital. You can drive an external 3*8-bit video DAC with some bits from one AMBER chip and some bits from the other AMBER chip.
The low cost budget chips have on-chip video DACS.
Their output is analog RGB.
Two analog RGB signals cannot be combined successfully into one RGB analog signal.
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alexh wrote:
You could make a 16-bit scandoubler/flicker fixer for video slots for well under €20 each, but who wants that?
maybe ECS users ? an internal scandoubler for the A500/A600 would need only 12 bits right ?
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Nobody in this thread seems to have considered the design of the original Microway's Flickerfixer.
They are the ones who coined the term flickerfixer because that's the name they gave to their product.
This card, back then, was very expensive because it used a full row of 32k x 8bit static RAM chips. Nowadays, a single 512k x 8bit chip costs only 6$.
It didn't use Amber for a simple reason, it didn't even exist. It used ordinary discreet logic chips that costs pennies today.
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XESS has a Spartan 2 FPGA board with a 32MBx16 ram chip for 88 bucks. It even has a VGA port, although it's only 3 bits/color. One more fpga pin & a resistor per color could fix that.
Been thinking about it, but I don't have a peecee with the oomph to run the design software...
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JimS wrote:
It even has a VGA port, although it's only 3 bits/color. One more fpga pin & a resistor per color could fix that.
Then again, that'd make only 12 bit output which is also possible w/ the low budget chips. 24 bit is a bit harder.
Hmm, combining two low cost chips w/ DAC could also be possible: if you use a small resistor array, you could actually 'add' the two analog signals (per color)...
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Hmm, combining two low cost chips w/ DAC could also be possible
If they had 24-bit digital RGB output, but they dont.
if you use a small resistor array, you could actually 'add' the two analog signals (per color)...
It wouldnt work.
XESS has a Spartan 2 FPGA board with a 32MBx16 ram chip for 88 bucks.
If you were going to do this with an FPGA you wouldnt a) use that FPGA and b) use that board! You'd have to make your own board to make the price sensible.
eslapion wrote:
Nobody in this thread seems to have considered the design of the original Microway's Flickerfixer.
Where is the design? Provide the schematics and the PLD source code and I'll look at it. Ah, you dont have it do you... never mind then.
It used ordinary discreet logic chips that costs pennies today.
I think you'll find they had a PLD (programmable logic device) something like a PAL/GAL/MACH etc.
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alexh wrote:
XESS has a Spartan 2 FPGA board with a 32MBx16 ram chip for 88 bucks.
If you were going to do this with an FPGA you wouldnt a) use that FPGA and b) use that board! You'd have to make your own board to make the price sensible.
Actually, I might very well use that FPGA and that board. The Spartan II is 5v tolerant. Just what you need for interfacing to old hardware like the Amiga without some extra chips to do the voltage translation. As for the board, I'm not interested in making a product for sale, so I don't care about the price. The XESS board would be cheaper than having a PCB made and trying to solder it in a toaster oven.
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Zac67 wrote:
JimS wrote:
It even has a VGA port, although it's only 3 bits/color. One more fpga pin & a resistor per color could fix that.
Then again, that'd make only 12 bit output which is also possible w/ the low budget chips. 24 bit is a bit harder.
That's true, of course... I've never owned an AGA machine, so I'm stuck in OCS/ECS thinking. ;-/
OK, how about an FPGA for logic and a byte-wide fast static RAM for each color... or if they make it in a 32-bit package, even better. It would make the board simpler, at the cost of wasting 8 bits/word.
Hmmm.... that LCD tv idea looks better all the time. ;-)
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JimS wrote:
how about an FPGA for logic and a byte-wide fast static RAM for each color..
That is the way most current scan doublers work. However they use a CPLD rather than an FPGA because the amount of logic you need is trivial.
JimS wrote:
if they make it in a 32-bit package, even better. It would make the board simpler, at the cost of wasting 8 bits/word.
This would make your FPGA/CPLD design more complicated but still feasible.
The problem means that you need write to the RAM at a rate of 27MHz while also reading from the RAM at a rate of 54MHz.
Previous implementations have opted for relatively expensive 3 * 8-bit dual port SRAM to overcome the reading and writing at the same time.
This is wasteful and poor design practice.
Instead if you make your rams 2x as wide and access two pixels at once you can read and write on alternate cycles.
Writing your own scandoubler is relatively easy. Writing your own flicker fixer is much harder.
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check this schematics, i will use on my own ScanDD.
http://elm-chan.org/works/sc/sc_sch.png
NTSC(YC/RGB) to VGA Scan Converter
http://elm-chan.org/works/sc/report.html
Simple Circuit Doubles Input Frequency
http://www.maxim-ic.com/appnotes.cfm/an_pk/3327