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RedDaemonFox
29th September 2009, 01:49
what do I need to build an Amiga RGB-VGA converter, and possibly scale the 15khz to 30/31khz

Zetr0
29th September 2009, 03:17
Okies letrs see if i can help

the cheap but good quality version would be a game of two halfs

firstly you will need one of these for 21.99 (inc postage) (*click image for ebay.com BIN*)

http://www.tinnou.com/images/com-57f.jpg (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290353998908&ru=http%3A%2F%2Fshop.ebay.com%3A80%2F%3F_from%3DR40%26_trksid%3Dm38%26_nkw%3D290353998908%26_fvi%3D1&_rdc=1)

secondly you need to have you Amiga output SVideo, (Y/C)

this is far superior to Composite RCA and very close to RGB quality.

There are many ways you can get your Amiga to output SVideo Y/C but by far the easist is to can get them from our AmiTrader UltraReliable from $33AUD + postage

http://www.amigamaniac.com/rgb_adapter_top.jpg

Now combining these two units what does it give you...

well the CRT/TFT Tuner outputs a VGA picture at the screen size you set (from 800x600 to 1440x1280) now any source video will be de-interlaced and scaled up (or down) to that VGA screen size.

essentially for aproximately 40 you get a Flicker Fixer / Scan doubler....

You also get PC VGA pass though, well Composite In/Out, 100 chanel RF in and Picture in Picture display....

I think thats pretty reasonable =)

RedDaemonFox
29th September 2009, 03:27
OMG TY Big Z, this will do so I don't have to spend so much money on an INDY or DCE SD/FF as I'm more frugal than a homeless person.

AndyLandy
29th September 2009, 11:28
Are there any of these boxes that will take a SCART input and scan-double that? For me at least, that'd save me getting the Amiga-to-S-Video bit, and probably give better quality too.

In fact, is there any reason why you couldn't connect an NTSC Amiga to a SCART cable, and use a SCART-to-VGA scandoubler (if such a thing exists?)

Zetr0
29th September 2009, 12:04
@all

In all fairness you could just ignore SVideo (Y/C) and plumb for the compos[h]ite input instead.... its not bad... yes it will flicker fix and yes it will scan double, but its far from the best in terms of picture quality.

However saying this, to be honest, if you are putting it on a small 17" or smaller screen and only likely to play games then it wont matter that much. but anhthing bigger than that say like my 42" plasma, then it really suffers, compos[h]ite is very VERY poor.

Howevere this would do in the interim while building / waiting or saving up for an RGB SVideo converter =)

I am sure there is a way to hack these types of boxes to accept analogue RGB in, I just have not had a close look yet.

@AndyLandy

There are few things out there that will do that, XRGB / XRGB2 and XRGB3 spring to mind, these solutions are NOT cheap, ranging from 150 to 300 personally for the difference, unless you are a L337357 PUR157 and must have every pixel exactly the right way at the right time, then presonally I wouldn't recomend them.

Harrison
29th September 2009, 12:47
What would be even better, but probably quite expensive, would be to work out how to convert the Amiga RGB output into component. That would give the best results on larger screens, because even using S-Video you are degrading the image slightly.

Component works by sending the video data though 3 cables. These are not RGB signals as some think because of the wiring colours, but instead are YUV. This works by sending the Master Y (black/white) Luminance signal down one wire, normally Yellow or Green, and the U (R-Y) and V (B-Y) signals (the colour difference signals) down the Red and Blue cables.

S-Video in contrast only sends the signal through 2 wires. One carrying the Y Luminance signal and the other carries a multiplexed version of the two colour-different signals. Therefore there is more chance of interference and signal mix up with the signals being combined down a single wire for the colour difference.

Taking video output in general, the SD PAL resolution is 720x576 (and NTSC 720x480). Firstly with composite you are lucky to clear 250 lines, ending up with about 240x576, which explains the bad blurring and degradation of colour on composite connections, and is about par with standard VHS recordings. Next S-Video is a much cleaner signal, but even this will only give you about 480x576 at the most from a good quality source, so you are still losing some resolution and degrading the image. Component and RGB SCART are the best output sources as both methods separate the RGB values and carries them between the source and destination along separate wires to remove nearly all degradation caused by noise and multiplexing. In addition the luminance and colour difference signals are also carried separately, so you get the cleanest signal at the other end.

Component and RGB Scart are pretty much identical in quality and output resolution. Therefore if you only want to output standard definition signals from an Amiga to a TV then an Amiga to RGB Scart cable will give the best results and is the cheapest option. No addition conversion needed. Converting to S-Video with one conversion box, and then upscaling the resulting image to VGA will in fact give you a worse picture than just connecting the Amiga directly via an RGB scart cable directly to the TV and letting the TV upscale the image to its panel resolution itself.

Obviously, if you need to output the Amiga signal to a VGA monitor, or wish to access the higher resolution modes without flicker, then you do still need a conversion and upscaling box of some sort. But the conversion to S-Video and then to VGA is not the ideal solution as you are converting the signal twice, and therefore degrading the signal each time, reducing colour accuracy and overall line resolution. But if only being used for Amiga games an RGB scart cable is in my view a good cheaper solution.