Found a scan doubler ( who would like one ) ?

[alexh]

IOWASURFER wrote:
http://www.miba51.com/CoCo_VGA_Adpater.html

here is the one Roy worked on for the Atari..

Actually that website shows Roy's first(?) use for his scandoubler, the Tandy Colour Computer (aka CoCo).

I believe its his design or a variation..
The info is on this site..

Yes I think it is, based perhaps on the Averlogic reference design. So far his scandoubler looks to be approx the same design between different computers (Tandy, Atari) perhaps a little evolution between revisions.

AFAIK he tweaks the default register settings to find the best one for each computer. centering, contrast, brightness, overscan etc.

The source code for the "tweaking program" and the I2C emulator is/was available from the Averlogic support site.

I guess you'd have to ask Roy about a cable if you wanted to tweak the settings yourself.

The heart of the scandoubler is/was an Averlogic AL875 ADC and an 16-bit AL250A Scandoubler/Flicker Fixer.

The big downer is that it is 16-bit, which means a fewer colours for AGA screens (which can be 24-bit). The Atari STe and ECS Amiga are 12-bit which are fine.

The little downer is that it probably wont work (well) with every Amiga screen mode possible. But I am sure it will work with PAL/NTSC with and without lace fine.

I hope that this time he uses a sheilded monitor cable instead of a ribbon cable like on the Tandy and Atari.

[Pyromania]

The magic question though is does it work for the Amiga Video Toaster?

[alexh]

Not by default.

A quick browse of the internet seems to show the video toaster to have 720 x 480i 60Hz Y/C outputs.

This is an RGB scandoubler by default, but it can be tweaked in software to be a Y/C scandoubler.

You would need to ask Roy about the tweak program and cable.

If anything this would work BETTER with the video toaster than an AGA Amiga because 16-bit Y/C can display more colours than 16-bit RGB.

[alexh]

-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 ;-)

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

The Averlogic chips are dirt cheap as they are in most low cost LCDTV's.

Roy is making a profit at $65-$75, and so he should, anything less than 50% profit he wont bother making more than a handful.

That said, I dont know how he first sold them (albeit at cost) for $48 including PSU? I guess that was before the decline of the US dollar.

[SamuraiCrow]

If I get a scandoubler, I want one that will do 24-bit RGB color rather than 16-bit.  I don't mind if it's internal though.

I'll probably wait until Hi-Def TVs come down in price and use one of those.

[alexh]

If you intend to use it on an A1000, A500, A600, A2000, A3000 or CDTV (that must be well over 50% of all Amiga's ever made?) then a 16-bit scandoubler wont make an ounce of difference as they are all 12-bit.

Some HDTV's have 16-bit RGB scandoublers.

[Darrin]

I would be interested in one for my A2000 native video out.

[amigadave]

If I didn't own 7 or 8 1080/1084 monitors already I might be more interested in this thread, but just out of curiosity, did the guy make any Amiga SD/FFs and has anyone from here tested one?

Did they sell for $48, or was the price higher?

[IOWASURFER]

The 65-75 was just my best guess could be a lot cheaper or vice versa until he is done with the first AMIGA prototype however with his ATARI successes I bet he will come up with some good stuff..

I guess the best thing about this scan doubler is it allows the little man to have a easily found cheap solution for a real Amiga computer without paying a leg and arm..

Finally a real hardware solution for the AMIGA if he can get them tweaked ALEXH we will be in for a treat dont ya think!?!?!

Joe..

[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.

[SamuraiCrow]

-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.

[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?"

[alexh]

-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.

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.

[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).

[rkauer]

 I don't want to throw water in the kettle, but the only limitation to this SD is it not SD the "special" screen modes an Amiga can do (DBLNTSC, DBLPAL, Euro modes, etc).

 But for 15kHz modes it works just fine, I think.

 For retro machines it works fine (A500, 600, etc). Specially for games.

[alexh]

-D- wrote:
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).

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)

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.

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