Found a scan doubler ( who would like one ) ?

[alexh]

Darrin wrote:
I'd be more interested in someone using one to run Zool2 AGA, Gunship 2000 AGA or UFO Enemy Unknown AGA and letting us know if they are "aware" of any problems when playing a game.

Probably not. You'd just shrug off having fewer colours as being part of the game. DCE FlickerMagic/ScanMagic internal scandoublers are I think 16-bit and they are widely used. I think only recently did it come to light that they were (but I am probably wrong and when they came out everyone hated them, but then forgot the limitation over time ;-))

I would imagine that using WinUAE with the aforementioned games and switching to a 16-bit direct colour mode may have the same effect as a 16-bit scandoubler. Try it.

[Damion]

Darrin wrote:

nBit7 wrote:
Maybe someone can find or make up a graphic that shows a 256 8bit single colour gradient next to the equivalent using only 4 and 5 bits.

That way people can see the difference for them self without having to resort to fiddling with screen modes.

I'd be more interested in someone using one to run Zool2 AGA, Gunship 2000 AGA or UFO Enemy Unknown AGA and letting us know if they are "aware" of any problems when playing a game.

I'm sure that squinting at hi-res static screens will reveal obvious differences, but I wonder if the naked eye when confronted with scrolling backdrops and fast moving sprites will detect any problems.  I use a SDFF (internal) in my A1200T and I haven't noticed any problems.  Granted, most games are ECS and I haven't tried to compare the cutput of the SDFF on a VGA monitor with my 1081 connected to the usual video out.

Dunno... probably not for the most part, but I suppose the best would be a back to back comparison. I ran the internal DCE unit for years and thought it was great, though now I'm wondering if it skewed my impression of AGA capabilities (like HAM8 photo viewing).

Bummer I sold it, as now would be a great time to make some comparisons... especially if the unit is in fact 16-bit.

[nBit7]

To be able to reproduce the full 16M colours would require using more than 24bits (3*8bits) at the analogue to digital converter (ADC).
This is because it would near impossible to line every analogue step with the corresponding digital.  For example suppose the analogue Red signal with 256steps (8bit) went from 0Volts for off to 1 volts.  Then each step will be 1/256 Volts or 3.9mV (0.0039V).

colour value = Analogue voltage level
-------------------------------------
0 = 0V
1 = 3.9mV
2 = 7.8mV
...
253 = 992mV
254 = 996mV
255 = 1000mV  (1V)

If the DAC was only looking at a range of say 0 to 995mVolts
it is clear that it would not correctly detect all the levels.  This is even before we consider all the various types of distortion.

If we sampled with say 16bits per colour and make the digital capture range slightly larger than the analogue then we can capture the full range of colours.

[hardlink]

-D- wrote:
 I ran the internal DCE unit for years and thought it was great, though now I'm wondering if it skewed my impression of AGA capabilities (like HAM8 photo viewing).

Bummer I sold it, as now would be a great time to make some comparisons... especially if the unit is in fact 16-bit.

You are on this side of the pond and you let an internal SD/FF get away???

The only time I saw one over here was at the EyeTech booth at the 2001 Gateway show. Alan Redhouse did not want to schlepp remaining stock back to the UK, so he offered either the internal or external for about US$60. I couldn't afford both, so I picked the external because it works on any Amiga, and I've been regretting the choice ever since.

That external SD/FF, and probably this new one too, adds a lot of noticeable noise to the image because of the extra Analog->Digital conversion. Still looking for an internal unit for my A1200, after all these years.

[Damion]

I played around a bit with WinUAE (AGA modes) and the gradients image alexh linked to earlier.

Cutting out the 0-255 color diagonal gradients and viewing them with PPaint, there is a loss of color (255 color gradients aren't perfectly smooth), however they look better than I expected, and the color loss in this case could be down to PPaint image handling/conversion process. The 256 color red sphere looks amazing since the banding is less perceptible.

While viewing the same image, switching WinUAE video mode down from 32-bit to 16-bit setting produced a horrific color loss, easily seen.

There was obvious banding viewing the reverse-aligned and RGB cube images, but this was to be expected since they use more than 256 simultaneous colors.

I played around with the HAM viewer, and as I recalled, gradients looked rather poor IMO. Yes, they can be somewhat smooth, but the weird HAM effects (looks like over-saturated colors and blurring) are obvious.

These are my observations after a quick test, and I realize there are too many variables involved to make any "definitive" statements (plus I'd really like to attempt some better testing using a "real" AGA machine).

My error lied in how I was viewing the "16" and "24" bit terminology in relation to Amiga video display, vs how alexh and others (admittedly more technical) usage. Normally, a distinction isn't made when referring to internal palette vs amount of displayable colors, since they are almost always the same. AGA is a bit unusual in this regard, having an 24-bit color palette, yet usually only capable of what would normally be termed an 8-bit (256 simulaneous colors) output (though from a 24-bit palette). I think this is why there is so much conflicting information abound on the subject. For example, HAM8 drivers for Shapeshifter are referred to by their authors as being 15-bit, simply in reference to the potential of displayable colors, not in reference to the internal palette. So the disparity here is really down to terminology. (And I still think it's a little unfair to say AGA is a 24-bit output without first clarifying things.)

Anyhow -- I'm not sure the DCE internal unit is 16-bit, at least not in the same sense as viewing, say, a 256 color blue gradient in WinUAE/AGA, and then switching to 16-bit. I used to do quite a bit of photo-related things using both HAM and 256 color screenmodes, and probably would have noticed such a terrible color-loss. Alexh and and I both agree that the GPS chip on that unit is certainly 24-bit, and if the output has been reduced it's not discernable from looking at the hardware specs.

Any SD that is 16-bit I would certainly avoid for AGA, though.

 

[Damion]

hardlink wrote:

-D- wrote:
 I ran the internal DCE unit for years and thought it was great, though now I'm wondering if it skewed my impression of AGA capabilities (like HAM8 photo viewing).

Bummer I sold it, as now would be a great time to make some comparisons... especially if the unit is in fact 16-bit.

You are on this side of the pond and you let an internal SD/FF get away???

The only time I saw one over here was at the EyeTech booth at the 2001 Gateway show. Alan Redhouse did not want to schlepp remaining stock back to the UK, so he offered either the internal or external for about US$60. I couldn't afford both, so I picked the external because it works on any Amiga, and I've been regretting the choice ever since.

That external SD/FF, and probably this new one too, adds a lot of noticeable noise to the image because of the extra Analog->Digital conversion. Still looking for an internal unit for my A1200, after all these years.

Yeah, what can I say, but bummer on my part. I sold it years back when I felt WinUAE was at a sufficient point of replacement. At the time, I was using it with a really nice Trinitron, and the quality was fantastic. (Aside from the 50 Hz PAL flicker, which I'm VERY sensitive to.)

I'm still searching for something to adequately replace it, since I've once again been smitten by the "oldies"... I've recently started putting my A1200 back together (just picked up a PG upgraded Apollo 1260) solely for the purpose of watching demos. This time, I won't be selling anything, that's for sure. :-)

There's a unit on Ebay that looks pretty good, except that one of its "features" is converting 50 Hz to 60 Hz, which might (to one extent or another) screw up all those lovely PAL demos. And then there's this guy, which doesn't convert from 50 to 60 Hz, but may be more of a pain to setup. The only quality scalers I've found cost an arm and a leg.

Ideally, I'd love to have my old internal DCE unit back + quality CRT for demos, and an LCD for WB-related things (to cut the eyestrain).

It's a real drag they're so rare and coveted these days... I dunno if it would be practical anymore (or if the parts are still available), but I bet DCE could probably sell a couple hundred units.

One positive thing to consider though, the internal unit runs really hot, as do the custom chips that are covered up by it. Might have an effect on longevity, which isn't an issue with your external version. Also, I found it to be kind of a PITA in a desktop case. (Between the IDE-Fix "Express" and the SD, 3 custom chips were covered up, LOL.)

[hardlink]

-D- wrote:
One positive thing to consider though, the internal unit runs really hot, as do the custom chips that are covered up by it. Might have an effect on longevity, which isn't an issue with your external version. Also, I found it to be kind of a PITA in a desktop case. (Between the IDE-Fix "Express" and the SD, 3 custom chips were covered up, LOL.)

Yes, those are very good points, especially about the DCE internal. Looks like the Micronik Scandy 1200 was a different design approach, with 2 small bare/passive chip 'snap-ons' and only memory and 2 big custom(?) chips on the main PCB snap-on:

http://www.amiga-hardware.com/showhardware.cgi?HARDID=373

I wonder if a design like this could be resurrected; maybe 3  passive ventilated snap-ons and a PCB that could be placed out of the way. Seems like it should be even simpler than an external unit if you can grab the digital RGB data, saving 3 A/D converters, and the image quality would be MUCH better.

[nBit7]

Cutting out the 0-255 color diagonal gradients and viewing them with PPaint, there is a loss of color (255 color gradients aren't perfectly smooth), however they look better than I expected, and the color loss in this case could be down to PPaint image handling/conversion process. The 256 color red sphere looks amazing since the banding is less perceptible.

remember that the gradients are restricted to 256 different colors at once.  But those 256 colours can be any out of the 24bit.

For 24bit colour RED GREEN and BLUE each can be set at 256 (0-255) levels (intensities)

If you were to use a gradient that used only one of those colours (eg. Black to RED, but not Black to RED to White).  In this case you would grantee that you didn't go over the 256 different colours at once limmit.   Then it can be displayed in 256 colour AGA with no loss what so ever, as there are only 256 red levels (in 24bit graphics) and AGA can display every one of them.  
An ECS or OCS amiga would only be able to display 16 levels of that gradient.  16levels leads to noticeable banding.

In an example where you had a gradient that went from Black to RED to White.  You have a situation where you can have 256 levels getting to full red then another 255 levels getting to white.
RED to White is made by keeping RED at 255 and bringing up GREEN and BLUE together.

[Vulture]

count me in if I see it working on a miggy (although I can't imagine a reason not to)!

[alexh]

nBit7 wrote:
To be able to reproduce the full 16M colours would require using more than 24bits (3*8bits) at the analogue to digital converter (ADC).

Not that it matters, but internal scandoublers, like the Arxon and Petsoff and DCE FlickerMagic / ScanMagic etc. dont have ADC's. They get their RGB information in digital form direct from the chips (Lisa/Denise).

For the best picture quality and colour representation the AL250a could be used on it's own directly attached to the Lisa/Denise chips without an AL875 ADC, but it would be and "Amiga only" solution. You'd need a different one for ECS and AGA Amiga's. It wouldnt be worth it. And it would still be 16-bit ;-)

[tokyoracer]

Are these still avalible? :-?

[Crumb]

Simply load the demo "Rain" by The Black Lotus. The clouds will look crap with 16bit scandoublers like DCE/phase5 CV3D scandoubler.

In contrast Arxxon or Picasso4 will look perfect.

BTW, AGA has a 24bit palette. That means I can make smooth transitions of just one bit. And it's noticeable if you are used to painting and computer graphics. It doesn't matter if you are showing just 16colours, it won't look smooth (read right) with a 16bit scandoubler!

Regarding HAM8, you can make very smooth transitions just changing one bit. The problem is not smoothness, the problem is changing from one colour to another one completely different.

In addition to that you should remember that AGA is not limited to 256 colours. Each few pixels the copper can change the palette.

If you can't notice the difference of AGA running through a 24bit scandoubler and a 16bit go to an eye specialist because you have some kind of visual problem

[adonay]

Does anyone have information about the Micronik Scandy 1200 is it 16bit also and would a CM-345Sscan with 24 bit ? just curious as i would like a CM-345S for other consoles and own the scandy "soon"

[DrDekker]

I'd definitely be interested in buying one - not bothered about it being 16-bit only as most of my games are non-AGA.  If I choose to run an AGA game, I'd just hook the A1200 up to the telly via the scart.

[hardlink]

alexh wrote:
For the best picture quality and colour representation the AL250a could be used on it's own directly attached to the Lisa/Denise chips without an AL875 ADC, but it would be and "Amiga only" solution. You'd need a different one for ECS and AGA Amiga's. It wouldnt be worth it. And it would still be 16-bit ;-)

Now your'e talking! I'm not so sure about needing one for ECS, the A3000 has one built in, and the A500 and A2000 can use the  old ICS Flicker Free Video 2, which seem a lot more plentiful than AGA internal doublers (I even have 2 of the ICS boards). And screw the A600

So for 16-bit quality, you think the AL250a would work? Does it need external RAM?

[Damion]

If you can't notice the difference of AGA running through a 24bit scandoubler and a 16bit go to an eye specialist because you have some kind of visual problem

No need to be an ass, at least I had the cojones to admit my mistake, instead of just disappearing. Once again, I've never stated AGA didn't have a 24-bit palette (or that a 0-255 red, green, or blue gradient couldn't be smooth utilizing 256 colors from said 24-bit palette). Also, never did I state that there isn't a difference betweeen 16 and 24-bit color. (Duh.) I simply didn't realize that a 16-bit scandoubler would actually castrate the palette, as opposed to only effecting the AMOUNT of displayable colors, and have since been corrected. It's a pretty honest mistake, considering how AGA is a bit (pardon the pun) different in this regard.

In addition, I still think HAM gradients look fugly (smooth or otherwise). They don't look good to me, as the colors appear over-saturated and blurry. This is simply a matter of personal opinion.
 
Clear as mud? :roll: