[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Why not just reproduce the second sight card?

zwsdotcom@gmail.com wrote:

On Mar 23, 11:19 am, "Michael J. Mahon" <mjma...@aol.com> wrote:


which is very strange. The sampling can be selected to be up to WXGA
resolution at VS=75Hz. But they were only $40 :)

If you've found one that produces a stable display from Apple II
composite video, with good quality, I'd like a pointer.  ;-)


Give me a quick BASIC program to demo the color/hires effects that
sucked on the hardware you've tried and I'll take a video of the
result. I'll see if I can get a good pic of my monitor with Appleworks
on it, but it's hard to take good photos of white text on a black
background.


On the "Cheese box" that I tried first, the colors in *any* graphic
were "cheesy" and garish in comparison to their appearance on a well-
adjusted color composite monitor--no special graphics test pattern
is required.  ;-)

And my primary concern for my use is text rendering.  While 40-column
text was readable, it was as if each horizontal scan line was
"squirming", since any vertical line in a character was jumping
back and forth about half a pixel or so.  This made the display
essentially unusable for text.

80-column text was even worse, since the bandwidth of the monochrome
composite input was clearly being limited by the converter, smearing
the (still squiggling) text.

Photos are easy to take if you have manual controls on the camera.
The trick is to set the exposure for the display being all white,
so that the white characters are not overexposed.


on, have had sampling artifacts that made them quite unusable for
text (with "squirmy" verticals, in particular).


In the default configuration I noticed some _horizontal_ artifacts on
single pixels in 80-col mode (e.g. the point in a curly bracket). I
adjusted a couple of the OSD parameters and that went away.


I wonder if that is allowing you to trim the sampling clock...?


I get the very best results for 80-column text by tinkering with the
sharpness setting of the converter, and putting it in S-video mode
(i.e. making it think the chroma is coming in on a separate connector,
which isn't in fact connected to anything). The only thing I could
wish for is green screen mode (yeah, I could disconnect the r,b lines
to the monitor but that's a bit extreme :)


S-video does not impose an arbitrarily low bandwidth on the luminance
signal, so that path can lead to sharp 80-column characters.

Actually, switching off R and B is the standard way of simulating
a green phosphor on a color monitor, but its usually done with a
switch for convenience.  I've used a "white" display on a color
monitor for long enough that I'm quite used to it--and using all
colors tends to make the shadow mask pitch less of an issue, too.


But the difference between the s-video setting and regular color-
capable composite setting is just a matter of blur, not crawling or
other mobile artifacting.


My converter doesn't have an S-video input, unfortunately (nor did
several I researched)--it sounds like yours is well-adapted to the
task.

That your converter can apparently phase lock to the Apple II 14MHz
dot clock is a huge advantage, and apparently relatively rare.


I am using this converter: KWorld TV Box 1440. <http://
www.shopping.com/xPO-input_adapters_kworld_tvbox_1440>. I bought them
on eBay for around $40 a year or two ago.


They seem a little harder to find now--though there are many
related products, I'd be loath to try anything but the exact
same product for fear of bad luck.  ;-)  I suppose that the
impending demise of analog TV broadcasts is marginalizing these
units...

-michael

******** Note new website URL ********

NadaNet and AppleCrate II for Apple II parallel computing!
Home page:  http://home.comcast.net/~mjmahon/

"The wastebasket is our most important design
tool--and it's seriously underused."