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Re: What GSE-Reactive Really Needs to Make
josephoswaldgg@hotmail.com wrote:
Michael J. Mahon wrote:
The product's value remains linked to the cost and scarcity of NTSC-
standards monitors, which are still both inexpensive and available in
most parts of the world.
I would argue somewhat with this. The scarcity is of NTSC-compatible
monitors that don't limit the bandwidth beyond standard definition
broadcast (i.e., eliminate the audio carrier, if I am not mistaken).
Actually, the limiter for composite signal separation is usually
imposed by the color subcarrier frequency. This limitation can
be overcome to a significant degree if the monitor uses a comb
filter instead of traditional LC filters, as essentially all
digital TVs do.
Although RF-linked monitor will have to filter out the 4.5MHz
FM sound signal, using a baseband composite input bypasses the
sound separation circuits.
The market for analog monitors is quickly developing into
1) LCD TVs that expect HD or SD video; I believe most of the composite
inputs for these will filter out what they expect to be composite
audio+video from a legacy DVD or VCR player; i.e. unusable for 80
column video.
If it is really a digital TV, capable of 720x480 (DVD) quality in
an NTSC format (480i), then it may well be capable of doing a good
job on 80-column text, though it may not support VGA input. (HDMI,
a derivative of DVI, is becoming a more likely common ground between
TV monitors and computer video cards.)
My tests of composite input on a Sony WEGA digital TV indicate that
the readability of a monochrome text display is not as good as on an
AppleColor Composite monitor ("m" and "w" are distinguishable but not
fully resolved), but all other letters, while not really sharp, are
quite readable.
The sampling clock does not lock to the Apple dot clock (14MHz), but
it is oversampling somewhat. The result is that monochrome text
"throbs" about 20% in brightness at about 8Hz--pretty annoying to
look at for long.
With the color burst on, resolution holds up (comb filter), and the
throbbing stops (sampler apparently locks to a multiple of the color
burst frequency), but, of course, the color artifacting on text is
severe, and readability suffers accordingly.
2) LCD monitors that accept VGA-style video inputs (treating them as
analog RGB with the VGA sync), either on a DB-15 or DVI connector, but
typically no composite input.
Although there are several high-resolution VGA monitors that also
provide NTSC support, I'm afraid that may still be unsatisfactory.
My tests on a Samsung Syncmaster 170MP with VGA, TV tuner, composite,
and S-video inputs show that all the NTSC inputs are bandwidth-limited.
80-column video, while readable, is pretty blurry, and lower case "m"
and "w" are unresolved.
I must conclude that analog NTSC support in this monitor is more of
an afterthought than a design goal, since the NTSC processing seems
to be analog.
I don't have a clue where to get composite color monitors with
80-column bandwidth, except off eBay, where I would be buying an
Apple-II vintage monitor, with a heavy CRT, and questionable age. Plus,
having to pay shipping for a heavy item that won't usefully hook up to
anything else I own.
If you have any information that demonstrates I can get an LCD monitor,
compatible with both my current computers and Apple II 80-column video,
I'd be glad to hear I was wrong with points 1 & 2.
I wish I could. Perhaps fully digital LCD TVs will do it, maybe not.
Though there is presently no market scarcity of suitable used monitors,
I can't argue with your concerns about shipping dangers and costs. If
a monitor cannot be found locally, that constitutes scarcity.
I'm beginning to get more interested in a modification to VGA CRT
monitors that would lower their horizontal scan frequency to 15kHz. ;-)
Of course, that would be a potential solution for an analog RGB or
monochrome monitor, but not for a "modern" composite color monitor.
OK, I'm sold! Let's see a nice VGA output "RGB" card for slotted 8-bit
Apple II's and another for the IIgs (Go, Ed!). ;-)
BTW, for those who want to see the "real" Apple II artifact colors,
there would still be a need for a *good* NTSC composite-to-VGA scan
doubler. Maybe this just means providing an "NTSC" mode for the
RGB model...
-michael
Music synthesis for 8-bit Apple II's!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it is seriously underused."