On Dec 13, 2011, at 9:58 AM, Vintage Coder wrote:
I understood from Tony a CRT monitor should just work.
I was asking him if I understood him correctly. From your post, it seems I didn't!
I think he probably meant once you'd converted it from RF/composite, it would work. A
composite signal is a mashed-up luma/chroma (brightness/color) signal, which is in turn a
mashed-up YPbPr (brightness/difference from blue/difference from red) signal. Once you
get back to YPbPr, you need to do a transform to turn that into RGB values, which is what
a CRT monitor will understand. You also need to separate out the vertical and horizontal
sync signals, because a CRT expects to get them separately (well, most do; there are
monitors which expect it to be superimposed on the green signal).
It's a non-trivial job to turn a composite signal into RGB, which is what a CRT (or a
DVI monitor, which expects the same thing but digitally) wants to see. A TV card will do
that for you and DMA the RGB data straight into your computer's RAM, or you can get a
converter box that does it all and blasts it out to VGA or HDMI (which should convert to
HDMI through a very cheap passive adaptor, since HDMI is inter-compatible with DVI).
Either way, there's going to need to be something in between.
I'm also not familiar with the CoCo line; did they ever make a PAL version? If not,
it wouldn't be useful to you to have a TV (well, not a UK TV, anyway) because it
wouldn't work. Most TV cards (especially if you're not using the god-awful
manufacturer's provided software) will tune to NTSC, PAL and SECAM and successfully
decode all three (though SECAM is left out often enough). You'll want to make sure
you get a card that can tune to US frequencies, though; the tuners are often a bolt-on
thing which can vary by manufacturer.
I can highly recommend the ATI Tv Wonder Pro
(
http://www.amazon.com/ATI-Technologies-Wonder-PCI-NTSC-100-703138/dp/B0000C…; it may
be available in your flavor of Amazon for a similar price). This particular one tunes
NTSC, so it will pick up an NTSC CoCo just fine. From my recollection, only the tuner is
restricted to NTSC (the frequency bands tend to be the issue there), so you should be able
to take in PAL/SECAM input sources on the other input connector if you should ever need to
do so.
- Dave