Scandoubler schematics

[amigite]

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.

[Kin-Hell]

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.

[amiga_3k]

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.

[alexh]

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?

[amiga_3k]

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.

[alexh]

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.

[countzero]

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 ?

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.

[JimS]

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...

[Zac67]

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)...

[alexh]

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.

[JimS]

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.

[JimS]

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. ;-)

[alexh]

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.

[1NOM155]

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