Scandoubler output looks horrible on TFT, but great on CRT

[derringer3]

Dudes if you try the old games in lcd you will be always got a very pixelized graphics. Because nowadays most lcd's got the optimal resolution somewhere 1024*768 or better. And crt-s handled the pixel array a little bit different than lcd-s. So go for a bigger workbench at your home to put on a good crt.  :-D

The scandoublers are not the only ones which have problems with TFTs.

The Cybervision, by default, offers a number of display resolutions/refresh rates which are non standard and display horribly on TFTs.

I had to spend a couple hours hours making sure every available mode on my CV64/3D are VESA compliant and don't cause problems.

That being said, converting the Amigas NTSC display into VGA normally results on a display mode which is very close to 640 x 480 @60Hz but with a slightly higher pixel rate but still at the same scan rate. This is a VESA compliant standard.

However, a display mode with 50Hz vertical refresh (PAL x 2) and 576 horizontal scanlines does not exist in the VESA realm. Hence the problem with PAL but not NTSC.

[keropi]

Dont those suck for AGA screen modes? They are only 16-bit.

I had one of these too, they offer great quality, and never really saw the difference until I installed on the same 4000 an Arxon videoslot sd... there is color gradient missing on the dce, because it is 16bit...

[kidkoala]

I've had a lot of tweaking an generally a few problems when using a Scandoubler but i've found out a few things;

------------------------------------------------------------
A600 (A-RGB) + Indivision SD/FF + 17" LCD (VGA) =

PAL  - Too low frequency for the LCD wich results in a constant errormessage onscreen, but with a ok picture behind it. Picture offscreen on top and left sides. Tweaking with the pot-meter on the Indivision a lot to get a stable picture needed. For a LCD to work properly with a Scandoubler, you need the rare models that can sync down to 50Hz. Search the net for these.
 
NTSC - Almost too low frequnecy but good enough to work. No errormessage. Picture is crisp, clear, strong colours. Picture still offscreen. Tweaking with the pot-meter on the Indivision a lot to get a stable picture needed. Picture looks pixelated because of LCD technology. NTSC is not a good signalstandard when using the amiga for PAL-games and software, so this is not a good overall solution. The games and wb I tried worked good though.


CD32 (A-RGB) + Indivision SD/FF + 17" LCD (VGA) =

Same as above with both PAL and NTSC. Using SX32, that's why I could test with A-RGB on the CD32.



A600 (A-RGB) + Indivision SD/FF + DLP Projector (VGA2DVI) =

PAL and NTSC - After tweaking the pot-meter, very good picture, as I remember also no offscreen problems. Not so pixelated either, because of the DLP technology (kind of a CRT/LCD combo). The modern projector is a flexible and highly signal compatible piece of equipment and works good with scandoublers, in my experience.

CD32 (A-RGB) + Indivision SD/FF + DLP Projector (VGA2DVI) =

PAL and NTSC - Same as above.
------------------------------------------------------------


 
Overall a standard LCD is not the best solution, but you can make it work if using only NTSC. If you get hold of a LCD that can sync down to 50Hz you get a nice picture with PAL compatibility.
Using a LCD-tv is probably better because it is more compatible, but these also have their problems like being widescreen native so that you loose a lot of screensize when using it with 4:3 equipment.
Using modern Projectors produce very good pictures because of their compatibility but blowing your wb out on the big screen isn't always what you want to do, so unless you're a gamer only type..
Using a CRT is probably the best solution picture and compatibility wise but then again you loose deskspace etc.
 
I must state that these tests where done with the high quality, recently made Indivison SD/FF and I have no experience with older Scandoublers/other equipment.
I have spoken to Jens Schönfeld earlier and he has said that he is working on a new, better SD/FF that eliminates several problems, among them the "too low frequency on LCD's" one.




System Details


Amiga 600 Project:

M-Tec w/8Mb
68030@40Mhz + FPU@33Mhz
1Mb w/clock ram upgrade
IDE2Flash with 2Gb CF-card
New chassis
New original Competition Pro sportsticks x2
Indivision SD/FF
Original OS 3.1

Amiga CD32 Project:

SX32 MK2 w/8Mb
680EC020@20Mhz
IDE2Flash with 2Gb CF-card
New chassis
New original CD32 gamepads x2
Indivision SD/FF
Original OS 3.9

[Iggy_Drougge]

If you're using an LCD TV, why use a scan doubler at all?

[kidkoala]

You're right, using an lcd-tv is like I said, better, and I didn't state you needed a Scandoubler for that purpose in my conclusion.

Anyway, I always try to use the best videosignals and when using a lcd-tv that would be a-rgb to vga so..you would need an adapter at least.
using a-rgb to scart would not produce the same quality, or am I totally wrong?

[meega]

Scart allows RGB at 15KHz, it's part of the standard.

[Iggy_Drougge]

kidkoala wrote:
You're right, using an lcd-tv is like I said, better, and I didn't state you needed a Scandoubler for that purpose in my conclusion.

Anyway, I always try to use the best videosignals and when using a lcd-tv that would be a-rgb to vga so..you would need an adapter at least.
using a-rgb to scart would not produce the same quality, or am I totally wrong?

You're totally wrong. The scandoubler is just an unnecessary extra step between your TV and the Amiga. And it might even be, that your TV is much better at handling PAL resolutions if you hook it up on the TV inputs and not the PC inputs.

[ZeBeeDee]

Sorry to hijack the thread but this looked promising a while back for Amiga users ... not sure if the project continues to this day or it's been shelved.

It appears it was intended for the C64 market but had very good possibilities for us amiga users as well.

The originating website (commodorescene.servebbs.org/vga.html) appears to be down at the time of posting, however Google has a cached version of the page if you search for it.

N.B. for some reason, I could not get A.org to insert the Google cached URL to the page  :getmad:

[kidkoala]

Well, I don't have a LCD-TV (cause I use a projector) but I know that the Scandoubler is of no use when using one. That's why I stated that I didn't write in my post that you do need one. I just stated that using an lcd-tv is a bit better than using a LCD-screen, because of the better compatibility with the signalstandard.

I do have a a-rgb2scart cable, and I'm getting an old standard tv from a friend soon so I might test that solution then, and I guess that solution will have better compatibility with the amiga, but the picture quality of an old tv isn't the best..

PS! I am on the lookout for a 15" lcd that can sync down to 50Hz so if anyone has one or know of a cheap one for sale pm me.

[Iggy_Drougge]

Are you saying that your LCD TV doesn't have a SCART input?

[kidkoala]

No, hehe, I'm saying I've never had an LCD-TV, I only have lcd-screen's (for computers) and a projector.

Using a lcd-tv is better than most lcd-screens, though when using lcd-tv's you will get a strecthed picture or loose a lot of the screensize because amigas aren't widescreen compatible.

[motorollin]

A few people have asked why I'm using a scandoubler with an LCD TV. Yes I know that using the SCART input from the Amiga's RGB socket will provide better quality. I have indeed been using it in this configuration for some time. But I wanted to use the CV64's autoswitch, which means scandoubling the RGB output to a VGA signal to feed in to the CV64. Now I know that scandoubled RGB screenmodes look horrible on a TFT screen (using a VGA input) I am no longer using the LCD TV.

--
moto

[kidkoala]

@motorollin

so what are you using now? i don't want a lcd-tv, but i do very much like to have a standard lcd-screen that syncs. down to 50hz, so that i don't have to use ntsc for my 600/cd32.

why is using a-rgb to scart input better than a-rgb to vga input (on lcd-tv's i presume)? and why do you say that pictures look awful when using vga input? i think they look ok, given the 10-15 years of age between the  machine and the screen, and given the incompatibility issues..the onl thing i think look bad is the pixelated style of the picture..not very amiga-like..

BTW what's a cv64?

i just need to understand the technical stuff..makes me confused..

[motorollin]

I'm currently using a Compaq 17" CRT. RGB -> SCART is better than RGB -> VGA on a TFT because low resolutions (like the Amiga's RGB output) have to be scaled up to the high resolution of the TFT screen, which can result in poor quality. If you use the RGB input, then there is presumably some circuitry in the screen's own scandoubler which scales and dithers it nicely. CV64 is shorthand for Cybervision64, which is the graphics card I use. It has a VGA input as well as an output, and it can auto-switch between them.

--
moto

[krize]

I guess I was luck; But i got a 19" HP LCD and using it with an external scandoubler (eyetech thingy). It works great!

Great screen to bring to demoparties etc =