C=128 80Col NTSC Color.
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From: The Questarian on 26 Mar 2007 21:31 a7yvm109gf5d1(a)netzero.com wrote: > If your definition of "work" is whatever is barely legible in a fuzzy > rainbow of shifting colors, more power to you, I guess. I point out > that this picture on Wikipedia looks too good to be true, I don't know > how they took it. As you can see, white text turns into a multi-color > brew. I'd have expected worse. I also expect it to be shimmering > constantly on a live screen. No way that's staying constant. > > The only way to get CGA properly encoded into an NTSC signal is with > some sophisticated signal processing. That's why you have to pay for > it, there's no demand for it. VGA to NTSC and NTSC to VGA is just as > hard, but almost everyone has a use for that so it's mass produced, > thus cheap. > > You have to read in a line with 16MHz pixel rate, then apply various > algorithms to limit the bandwidth and encode the colors in ways that > are compatible with the NTSC dot clock, and the limited bandwidth of > the I and Q sub-carriers. Oh not easy at all. > > CGA to VGA is easier because you don't have to care about a tight > relationship between clock frequencies because the colors are not > encoded, they're just voltages on three wires as opposed to phasors > buried in one wire. You just clock in the data at one speed, and toss > it out at twice the speed. Assuming you can get a clean clock signal. > > Now if only someone could tell me why I can't get the LUT to work on > my project... My VGA output is purple, but it's sharp! (More or less!) > > http://dfpresource.org/VGA_noLUT.jpg > > The blurriness here are JPG compression artifacts. > > Anyways, I hope people read that Wiki page, although it's vague on a > few things it should clear things up. > I'm interested in the CGA to VGA and NTSC to VGA... the CGA to VGA+ board would make a nice internal upgrade for my 128D... and it would round it out nicely to be able to route the composite through to the LCD monitor as well. I understand why they're pricey, but that they're available at all is the really attractive part...the price however is somewhat less attractive... the cga-vga board prices out at $141 USD, the NTSC/PAL-SXGA I'd like is $185 USD, and the NTSC-DVI converter I'd prefer give a choice is $275 USD. LOL, and that doesn't even include shipping from Australia.
From: a7yvm109gf5d1 on 26 Mar 2007 22:53 On Mar 26, 8:31 pm, The Questarian <J.bie...(a)REMOVEMETOSEND.Questarian.com> wrote: > a7yvm109gf...(a)netzero.com wrote: > > If your definition of "work" is whatever is barely legible in a fuzzy > > rainbow of shifting colors, more power to you, I guess. I point out > > that this picture on Wikipedia looks too good to be true, I don't know > > how they took it. As you can see, white text turns into a multi-color > > brew. I'd have expected worse. I also expect it to be shimmering > > constantly on a live screen. No way that's staying constant. > > > The only way to get CGA properly encoded into an NTSC signal is with > > some sophisticated signal processing. That's why you have to pay for > > it, there's no demand for it. VGA to NTSC and NTSC to VGA is just as > > hard, but almost everyone has a use for that so it's mass produced, > > thus cheap. > > > You have to read in a line with 16MHz pixel rate, then apply various > > algorithms to limit the bandwidth and encode the colors in ways that > > are compatible with the NTSC dot clock, and the limited bandwidth of > > the I and Q sub-carriers. Oh not easy at all. > > > CGA to VGA is easier because you don't have to care about a tight > > relationship between clock frequencies because the colors are not > > encoded, they're just voltages on three wires as opposed to phasors > > buried in one wire. You just clock in the data at one speed, and toss > > it out at twice the speed. Assuming you can get a clean clock signal. > > > Now if only someone could tell me why I can't get the LUT to work on > > my project... My VGA output is purple, but it's sharp! (More or less!) > > >http://dfpresource.org/VGA_noLUT.jpg > > > The blurriness here are JPG compression artifacts. > > > Anyways, I hope people read that Wiki page, although it's vague on a > > few things it should clear things up. > > I'm interested in the CGA to VGA and NTSC to VGA... the CGA to VGA+ > board would make a nice internal upgrade for my 128D... and it would > round it out nicely to be able to route the composite through to the LCD > monitor as well. > > I understand why they're pricey, but that they're available at all is > the really attractive part...the price however is somewhat less > attractive... the cga-vga board prices out at $141 USD, the > NTSC/PAL-SXGA I'd like is $185 USD, and the NTSC-DVI converter I'd > prefer give a choice is $275 USD. LOL, and that doesn't even include > shipping from Australia. Those prices are reasonable. It's a lot of work to design one of these. I mean if I released my design as-is, you'd end up paying about 33$ for just the PCB, toss in another 60$ for parts, and then you have to solder it, test it, put it in a case (another 20$), add a power supply, and that's if you build it yourself and have the equipment to do so.
From: Dopple on 26 Mar 2007 23:57 Could always jump into this like I jumped into making a batch of EZ232 and Link232 interfaces. I bought enough parts in quantity, and am selling them for $20 as a kit, and $30 assembled. Of course, you're looking at a lot more capital for a batch of these converters... BTW, I did buy one of the RGB to VGA converters from www.converters.tv. In a word: Sux0r. Problem is, they SAY it can do RGBI, but it can't. So, now I have to build a RGBI to RGBA converter to feed to this thing. -Jay a7yvm109gf5d1(a)netzero.com wrote: > Those prices are reasonable. It's a lot of work to design one of > these. I mean if I released my design as-is, you'd end up paying about > 33$ for just the PCB, toss in another 60$ for parts, and then you have > to solder it, test it, put it in a case (another 20$), add a power > supply, and that's if you build it yourself and have the equipment to > do so. >
From: Mangelore on 27 Mar 2007 01:55 The Questarian wrote: > Rick Balkins wrote: >> You're right Brian. >> >> However this thread began to evolve to a wider topic of converters >> suited for C128 80 col. video. I am addressing Mangelore's part and >> appeared to have provided an interesting input that seems to actually >> help. That is suprising in itself. >> > Out or curiosity, I've run into a site that has a variety of video > output format converts (cga,ega,vga,ntsc,pal, etc) at > http://www.converters.tv/ and there are CGA to VGA, CGA to NTSC, and > NTSC/PAL to VGA converters... some of them seem a bit pricey... has > anyone had any experience with these boards and that vendor? Yes, I've used one of their converters. They are expensive and don't support the I in RGBI, so you only get 8 colours. I'm working on a solution that will be more economical and support RGBI.
From: Mangelore on 27 Mar 2007 01:57
Dopple wrote: > Could always jump into this like I jumped into making a batch of EZ232 > and Link232 interfaces. I bought enough parts in quantity, and am > selling them for $20 as a kit, and $30 assembled. > > Of course, you're looking at a lot more capital for a batch of these > converters... > > BTW, I did buy one of the RGB to VGA converters from www.converters.tv. > > In a word: Sux0r. > > Problem is, they SAY it can do RGBI, but it can't. So, now I have to > build a RGBI to RGBA converter to feed to this thing. > > -Jay > It's very simple to integrate the Intensity signal. Just a few resistors and diodes does the trick. |