Found a scan doubler ( who would like one ) ?

[Damion]

Not sure I get it... the XRGB2 is pretty expensive, and difficult to find now.

[Damion]

I guess what I'm not understanding is that the link is for a device that connects a coco to an XRGB... the Amiga can connect to an XRGB with nothing more than a SCART cable. (In fact, doesn't the XRGB handle 15kHz via an RGB in?)

Granted, if someone can produce a scan doubler + flicker-fixer for $65, I'm sure it would sell very well.

[Damion]

alexh wrote:

-D- wrote:
I guess what I'm not understanding is that the link is for a device that connects a coco to an XRGB...

No it aint, it's a CoCo 15KHz RGB to 31khz VGA. I think the URL kinda gives it away ;-)

The link in the op has now been corrected... it was originally something about a coco -> XRBG2 adapter. :-P


EDIT -- Also, I think it's fair to point out that this unit would be fine for the majority of AGA games/demos (256 color screens). HAM modes aren't used often (at all?) for games at least.

[Damion]

SamuraiCrow wrote:

-D- wrote:
EDIT -- Also, I think it's fair to point out that this unit would be fine for the majority of AGA games/demos (256 color screens). HAM modes aren't used often (at all?) for games at least.

The palette entries on an AGA system are 24-bits long.  The colors would look a little off on AGA.  I've got an A1200 and I want AGA colors to look right.  I intend to play Total Chaos with this and it has splash screens in HAM8 also.

Bullspit.

Millions of devices around the world use these chips for video playback, I guarantee it will handle 256 simultaneous colors just fine, with or without an internal 24-bit palette. It will be at least as capable as any earlier "amiga specific" scandoubler.

Furthermore, if it is indeed using the Averlogic chips which alexh mentioned, they both have 8-bit DACs each for RGB. Also, the AL250 has an additional LUT for gamma correction, essentially (I assume) so that manufactures can tweak the output for best results with their application. (Pretty decent feature, actually, something Eizo advertises as well.) Look up the datasheets yourself, it's right there in black and white.

In addition to this, a good majority of consumer LCDs out there aren't "true" 8bpp panels anyhow (even some which are advertised to be). I also appreciate a good display, but let's not get too ridiculous about the color output of an early 90s era computer. (HAM8 mode is essentially a 15-bit *external* output, anyhow.)

Bottom line, if you want something better be prepared to shell out multiple thousands... and then ask yourself, "is it really worth it?"

[Damion]

alexh wrote:

-D- wrote:
EDIT -- Also, I think it's fair to point out that this unit would be fine for the majority of AGA games/demos (256 color screens). HAM modes aren't used often (at all?) for games at least.

-D- I am sorry man but that is not true! We've had this conversation before. AGA modes (including 256 colour) are 24-bit! For example a 256 colour screen has 256 different, 24-bit colours!

Using a 16-bit scandoubler for AGA demo's and games will give bad results almost all the time.

How bad depends on the colours in the program. If they were 256 shades of red for example (highly unlikely) you would only see 32 of them.

As an example, open this image in windows with a 24-bit (or 32-bit) screen.

http://www.spronkey.com/sdc-gradients.png

Then change the colours to 16-bit. You will see the loss of information on the 256-colour (smooth) gradient bars, but also on the others.

Alexh I'm not necessarily disagreeing with that, all I'm saying is that I'm not convinced this unit is 16-bit and/or would b0rk the color output.

And I agree, 24-bit color gradients will look messed up switched to 16-bit. But this isn't exactly the same thing, as AGA isn't capable of *outputting* smooth gradients, since it can't simultaneously display the amount of colors necessary for that (and HAM8 produces nasty color artifacts).

[Damion]

Sorry but you are just thick if you cannot understand it.

The 16-bit scandoubler ignores the 3 LSB's of Red and Blue and 2 LSB's of green. That means that an AGA colour with a blue value of 0 is displayed the same as an AGA colour with a blue value of 7! (assuming the other components are the same)

LOL, I'm "thick" because because the datasheets for the chips you mentioned state they have 8-bit DACs for each color, yet you keep saying it's 16-bit. That's pretty funny.

This has nothing to do with me not understanding the difference between 16 and 24-bit output. Any dumbass can switch from truecolor to highcolor and see the difference (and I've already stated my awareness of the AGA 24-bit *internal* palette).

AGA can display smooth gradients. If say the colours in a program used 256 shades of red for example (highly unlikely but possible) it would have ALL the possible RED shades of a 24-bit screen and if you use a 16-bit scandoubler you would only be able to distinguish 32 of them from the others.

Yes, using 256 colors it's possible for a smooth gradient, but as you've stated, highly impractical. Try viewing the image you linked to on an AGA screen, and it will look like ass.

You get a BANDING effect as what was supposed to be a subtle gradient of colours appears as one.

Due to the very nature of how HAM works, you get fugly looking images, gradients included. This even has nothing to do with HAM8 not being a 24-bit output in the sense of displayable colors, regardless of the internal palette.

[Damion]

OK, I will try it... and if I have to eat shoe, I will :-p

And I agree, a 16-bit scandoubler might not be ideal for AGA, if indeed it effects the internal palette and not just the "amount" of displayable colors, admittedly I'm not an expert on this.

BUT, I can't find anything in the datasheet for the AL250a indicating a castrated input, however, I'm open to correction.


 

[Damion]

alexh wrote:
http://www.averlogic.com/admin_en/product_en/pic8/540738.pdf

Look at the number of bits on the input on the diagram on page 1. 16-bits

OK -- you are correct. I agree this is sub-optimal...


@JosephC

Dead wrong. 100% incorect, false and untrue. You should be ashamed of yourself.

Get over yourself. 256 color gradients, yes. HAM8 gradients look fugly with an excess of color fringing/bleeding.

[Damion]

alexh wrote:

-D- wrote:
Get over yourself. 256 color gradients, yes.

No, no, no.

Not just 256 colour gradients.

Any picture.

If the colours use the lower 3-bits, and there are several of them. They will appear as one colour.

Ugh... there seems to be a bit of misunderstanding going on here.

Issue one -- In the above reference (@JosephC), my intention wasn't to say that a 256 color gradient would look as it should with a 16-bit SD, only that while AGA itself (viewed normally) is definitely capable of 256 color smooth gradients, HAM8 gradients don't look right because of the way HAM works.

Issue two -- I figured that since AGA is only capable of displaying 256 simultaneous colors (for the most part, outside of HAM modes), that therefore a 16-bit SD should be fine... not taking into consideration that a 16-bit SD could actually mess with the palette capabilities (it must "round off" certain colors, so to speak). I clearly understand the difference between 16 and 24-bit in regard to displayable colors, but didn't consider that the palette (in the case of AGA, 24-bit) might also be affected. Therefore, I stand both enlightened and corrected in this regard.

Also, I determined (from a quick browse of the datasheets) that the Averlogic SD was 24-bit, after noticing the 3 8-bit DACs. I stand corrected here also, as alexh is right, the input is indeed 16-bit.

My apologies to the thread.

[Damion]

alexh wrote:

-D- wrote:
BUT, I can't find anything in the datasheet for the AL250a indicating a castrated input, however, I'm open to correction.

http://www.averlogic.com/admin_en/product_en/pic8/540738.pdf

Look at the number of bits on the input on the diagram on page 1. 16-bits

-D- wrote:
if I have to eat shoe, I will :-p

Nowt bad about being wrong mate, happens to me several times a day, you just pick yourself up, learn from it and get on with it. Makes you a stonger engineer.

Cheers. I came out guns blazing, only to feel like an ass. Sorry guys :lol:

[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.

[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.)

[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: