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Old 11 August 2006, 18:56   #1
girv
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Quality of different native-video output options?

So I'm at last in the process of (planning to start thinking about considering...) rebuilding my computer room in my new apartment, finally, after about a year of delays and no Amigas. I've got a nice 19" LCD monitor for the PC and Amiga gfx card outputs, but I'm looking for info on what to do about the Amiga's 15Khz native chipset output.

I do have an external scan doubler that I can feed into the LCD (I assume), but I'd read that an internal SD would give a better quality output picture.

Is that true? If so, how much better?

And generally, what is the quality like for RF, composite, RGB video output options in comparison ?

Any opinions welcome
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Old 11 August 2006, 19:05   #2
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lo Girv good to see you back posting... As for the Scan doubler, you dont need it , send it to me
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Old 14 August 2006, 02:27   #3
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Many many years ago I had an AmiVGA external scandoubler. It worked, but frankly was no competition for a "real" internal scandoubler such as ICD's FlickerFreeVideo. But, it was better than nothing. Oh, and its ECS chipset only...

In terms of which output gives the best picture quality, in ascending order

RF - same as TV connected directly to antenna.
Composite - better than RF, but can be smeary.
RGB video - best of the standard (or most commonly offered) connectors, although only if it is a TRUE RGB scart, i.e. uses seperate pins for R, G, and B, as opposed to a SCART connector that uses a composite video feed.

Not available as outputs on the Amiga, but worth mentioning in passing
S-Video - between comp and RGB. Does not carry sound signal though (although not an issue on the Amiga)
Component Video - offers best analogue picture quality, especially for progressive scan source.

I can speak, from experience, on the Dell FP2001 21" LCD. These offer VHDI, VGA, Composite and RF inputs, and are very, very good. Ok, its a 4-5 year old TFT, and 16ms may not quite cut the mustard (yeah, right. Its more than ample for games, DVD and TV playback, with no smear or tear) compared to 4 or 8ms, but the picture is superb, rock steady, and best of all, the price has dropped with the advent of the 2005 series. Excellent buy ex-stock, or even second hand. I had 2 dedicated to my PCs (using dual display) and one for single display mode/Amiga. Excellent. All 3 were occasionally pulled into use on the Parhelia, albeit this was analogue only, and the resolution dropped below the native 1600x1200. However, the 2001 can do 1:1/scale/zoom dispaly modes, which allows you to use non-native displays without pixel distortion.

Get a scan doubler, preferably internal model, if possible.
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Old 14 August 2006, 03:30   #4
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Quote:
Originally Posted by alewis
Many many years ago I had an AmiVGA external scandoubler. It worked, but frankly was no competition for a "real" internal scandoubler such as ICD's FlickerFreeVideo. But, it was better than nothing. Oh, and its ECS chipset only...
I've got one of those too, and being an interested type I opened it up to see what was in it. After carving out the hot-melt glue that the PCB was potted with, I discovered that it was basically the same as commodores silver VGA adaptor that shipped with the A4000, but with a passthrough port for a 15KHz monitor or genlock or whatever. The software disk that came with it simply forces the Amiga to use a VGA mode, which is why it only works on ECS (or AGA in theory) and doesn't work with most games.
There are real external scandoubler/flickerfixers, which while they will not match an internal one, will at least work with any software. However, they were never cheap even when new, and now cost several times what a video slot flicker fixer does.
Most of the console -> VGA type boxes you can get these days will only do composite or S-Video, with the better ones also offering component, but none that I've seen offer RGB. Fortunately, converting the RGB signal to component should be relatively trivial.

It is possible to hack s-video output onto the A1200/600, and the A520 modulator, instructions are on Aminet.

Alternatively, http://elm-chan.org/works/sc/report.html shows a lot of promise as a DIY scandoubler, though it seems it would not deinterlace, and may not work too well with LCDs if coming from a PAL source (but then, neither do either of my video slot ones with my elderly Apple LCD, modern displays might be a bit less picky).
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Old 14 August 2006, 06:21   #5
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I believe to de-interlace screens there needs to be a frame buffer/store. since the interlaced screens are essentially two screens these are intergrated by the given frequency of 15khz natively..

to get this to work on 31Khz or greater you would need a frame buffer and some logic that knows an interlaced screen is in use to re-intergrate as one image to then onto the 31khz+ output.

this i belive would be the primary fall of using a tv-tuner to crt/tft device. but if you get one that can sync as low as 15khz rgb, then you may be onto a winner... as least in the double pal/ntsc area...
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Old 14 August 2006, 10:29   #6
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Just use one of those "game v-boxes" that can take RGB in. (no point in using composite or s-video)

The quality is good for games, but at least mine gives a slight ghosting on vertical lines in WB use. Not 100% blurry or anything, but unfortunately I can't say it is perfect like with a digital internal scandoubler.

I ought to post some pictures sometime.
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Old 14 August 2006, 13:04   #7
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I always wondered about the silver VGA adaptor that C= provided. What exactly did it do? Just adapt the 23 way video out to a 15pin VGA (still at 15KHz) or did it double the frequency to 31KHz as well?

Reason I ask is that a have a couple or three around here, just wondered whether I need to keep them or not.
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Old 14 August 2006, 13:37   #8
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@alewis: thanks, that's good info. It's pretty much what I figured but it's nice to have it confirmed from experience

I have an external scandoubler (two, actually) so I'll probably stick with that for now, but I might look into an internal model instead as the consensus here appears to be that it's much better.

@jope: can you give a web link to the sort of "v-boxes" you're talking about please?

@all: my LCD monitor has DVI input, but my KVM switch supports only standard 15 pin D-sub connections so the PC output will be fed through a DVI->VGA convertor. Will that affect the quality much? Is it worthwhile changing my KVM to a model that supports DVI and would one of those support the Amiga's VGA output ?

Thanks!
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Old 14 August 2006, 22:14   #9
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alewis: the Commodore silver adaptor IIRC buffers and inverts the sync lines, but apart from that, it will only output the video mode that is being input.

girv: A vga to DVI adaptor may not work, they're designed for connecting VGA monitors to graphics cards, which usually have the circuitry onboard to convert the digital DVI signal to analogue VGA, however, to the best of my knowledge LCD displays with DVI only do not have the ability to convert the analogue signal back to digital.
You can get boxes to do the conversion, but the price is not pleasing ( http://www2.dvigear.com/vgatodvicosc.html $400 for this one, but there are probably cheaper), and you'd still need a scandoubler to bring the output to VGA in the first place.
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Old 16 August 2006, 00:00   #10
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Girv

You *could* use a DVI->VGA adaptor (often included with DVI-only gfx cards) or cable. Then a VGA->DVI adaptor from KVM to LCD.

However, there will be noticable degradation.

What model LCD is it, and what inputs does it offer?

Why? Well, one drawback to KVM's is when you want to use >1 machine at a time (ie, my main work rig and another PC/Amiga/SPARCstatoin60). So, I used 2 KVMs and 4 keyboards (one on each KVM, plus dedicated Mig and Sparc). The FP2001 had multiple inputs, so the Opteron was directly connected to two LCD's via DVI; a
The single LCD had an Athlon64 via DVI, and a Tyan Thunder 2500, P4, and Mig via DSUB through the KVM. The 4th input on this KVM was for when I wanted to triplehead the Opteron, which required DSUB (and some messing around at the back of the PC with cable swaps!)

Complicated, but I wasn't constrained by the number/type of connectors on the KVM/cards/monitors. In addition, the Composite video and RF ports on the second [of the paired] LCDs were attached to a VHS deck and Matrox RT2500 for editing/monitoring purposes for video work.. *very* handy. And also of course, on the single LCD, for the Amiga.

So I could swap displays without losing conrol of the machine, useful at times when one needed to do more than PCAnywhere/VNC allowed. And all front panel selectable.

Wish I still had them :-(
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Old 16 August 2006, 04:32   #11
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to be honest griv.

composite is pretty good for games, but if you use a *LOT* of WorkBench in *NATIVE* screen modes then i would recomened an RGB solution.

if you do choose the flicker fixer / scan double route make sure that the hardware does both (in AGA) not just scan double ECS.

insofar as DMI/SVGA realistically, gonna be contrary to alewis, i couldnt notice the difference i figure unless you have cybernetic eyes that can sync to under 6ms scanlines..

I have an 19" LCD monitor connected to a 4port KVM via a DVI to SVGA inout... since all the devices i have only push SVGA thats all its gonna get.

I also have another connected DVI to my primary PC.. both are branded (samsung and sony) LCD's and both are under 8ms and i havent noticed any difference between either running Battle For Middle Earth 2 in 1280x1024x32
theres absolutly no difference what so ever... and truth is though your not, or wont, even pushing SVGA maximum let alone the DVI lol.
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Old 16 August 2006, 10:33   #12
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Girv, something along the lines of:

http://cypress.com.tw/product.php?PI...onverters&SR=1

There are many others, cheaper and more expensive devices..
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Old 17 August 2006, 01:48   #13
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@alewis: not sure of the model exactly, Iiyama Pro something circa 2003. It has DVI and DSUB inputs selectable from the front panel, but it's a pain to swap them that way as it takes about 4 button presses (menu->source->1 or 2->select). I hear what you're saying about not using a KVM, but I am space constrained here and can't fit two keyboards in with the rest of the junk

I'll have the single monitor for a little while yet so what I'll probably do is connect the Amiga to the DSUB input and the PC to the DVI, but then I'll need some way of switching between the Amiga gfx card and (scan doubled) native output. Once the second monitor is here I'll have the PC to both DVIs and the Amiga gfx card and native to one each of the DSUBs. And some inventive way of sharing the keyboard and mouse no doubt
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Old 17 August 2006, 09:40   #14
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Know what you mean about button presses - thats was another plus forthe 2001 - the input button was seperate from the menu.

Presumably the mig gfx card is using a DSUB connector, what does the SD use? If it is DSUB, then the best solution would be a KVM, and the absolute best KVM was the Adder Smartview (not to be confused with the chaper Adderview) Don't skimp on cables - you dont realise how much they affect quality until you've witnessed it yourself.

As it hapens, have a spare 2port smartview and cables.
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Old 17 August 2006, 11:02   #15
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Quote:
Originally Posted by Secret Vampire
It is possible to hack s-video output onto the A1200/600, and the A520 modulator, instructions are on Aminet.
The local Melbourne Amiga Users Group has been converting A520's to S-Video recently, pity they're on the other side of the city to me so I never attend any meetings.

I've had a look on Aminet and all I could find was the A1200/A600 modifications for s-video:

http://www.aminet.net/package.php?pa...ideo_A1200.lzh


edit: google and the waybackmachine found the A520 modification:

http://web.archive.org/web/200406111...lock/A520.html
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Old 24 August 2006, 15:18   #16
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@alewis: the 'mig gfx card and scan doubled output both use DSUB-15 connectors.

I'm working on my master plan and so far it still involves a KVM. What's so cool about the Adder Smartview ?

DDNI put me on to the idea of an external TV Tuner box such as the following: [ebay] [aver media] [ads tech]; these offer a variety of selectable inputs and would also give me a 19" LCD TV, which is nice. I also have one of those Atari2600-innna-joystick TV game things that could be connected (composite) for some real retro fun

The AverTV Box9 is interesting as it offers component input which could (I think) be used to give very good quality Amiga output via an RGB->Component converter box. The trouble is the Box9 is about £85 and an RGB->Component converter about another £50 (for a cheap one), whereas the box from eBay is £30 all-in but then I'm stuck with sucky composite or RF output unless I hack S-Video into my A1200

That might be a good compromise, but I've looked at the A1200 S-Video instructions on Aminet [here] and I'm afraid that I just don't get it Is the CXA1145 (U12) chip on the motherboard (where?!) or do I have to build a circuit with it in it? The pictures in the archive aren't very clear.

Just thinking "out loud", feel free to ignore my ramblings
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Old 25 August 2006, 02:22   #17
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The Adder Smartview KVM was simply the best quality KVM for it's time - and to be honest I'm not aware of anything that has surpassed it since, especially as IP-KVM's appear to be all the rage now. It cleaned and boosted the video signal, to the point where the display via KVM was indiscernible from a direct video connection. It also used *very* high quality cables (using a "standard" Compaq supplied, or a cheap, video cable, caused a noticeable drop in quality. The cable sets cost more than the KVM,s iirc! They worked at resolutions up to 1600x1200 - possibly beyond, but that was the max res I ever used with rock solid, pin sharp picture.

They are that good I bought four of them, (2 4 port, 2x2port) back in 1999/2000.

As an aside, don't touch the Compaq 19" rackmount KVMs. They are useful for server work, and thats it. Signal is noticably degraded, and horrible at 1024x768, let alone higher.
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Old 27 August 2006, 20:23   #18
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Regarding the A1200 s-video hack, I just did it to my A600.
Unlike the author of the aminet hack, I removed the modulator eniterly, and screwed a panel mount mini-din socket to the shielding, and built the circuit using wire-wrap (on a piece of cardboard, since I didn't have any perf-board to hand)
Results are pretty good, there's still some bleeding, and the colours aren't perfect, but I built it as a quick hack using the cheap parts I had to hand, and the s-video cable came from poundland, so I wasn't expecting perfection. Anyway, the picture is still sharp enough for workbench use even in the super-hires laced mode.
The CXA1145 should be just to the left of the IDE connector looking from the front of the A1200, it's a surface mount chip so soldering on it is a little fiddly, but not too hard if you have a steady hand and some experience.
I took a photo of it with my phone-cam, but it is hard to tell what is going on due to the poor quality of said camera. I'll take a better picture when I've charged some batteries for my real camera and post in the pics forum.
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Old 04 September 2006, 10:26   #19
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Quote:
Originally Posted by gizmomelb
The local Melbourne Amiga Users Group has been converting A520's to S-Video recently, pity they're on the other side of the city to me so I never attend any meetings.
Hi. I've recently tried this mod to my A520 with momentary success. The S-video picture quality was great, for a second! You can read about it here.

Unfortunately, one of the transistors on the A520 started smoking. I think I have found the problem with my circuit, but now I think the transistor is broken (the blue smoke escaped).

The transistor is marked C945 and P213C on the line under, but this doesn't seem to conform to standard markings. Looking at this diagram of the A520 it's the one marked Q1 (the highest transistor in the first picture).

Anyone know if there's a way to identify the transistor so I can buy an equivalent for replacement?
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Old 04 September 2006, 10:36   #20
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C945
Probably either 2SC945 (It is very common to drop 2S-prefix) or BC945.
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