Re: AST Visionplus

[mjmahon@aol.com (Michael J. Mahon)]

I was looking over my AST VisionPlus board last night, and I'm becoming
very curious about how it works and how it should be calibrated.

First, how it works:  I don't see any RAM on the board, so the actual
storage of video samples must be in the Apple's RAM.  But if it is a
frame capture board, that means that the whole frame must get sampled
in real time.  Assuming 256x200 pixels (or so) that adds up to over
1MB/s, the bandwidth of the Apple expansion bus--even at only one byte
per pixel, which I think is low for the 12-bit color it is capable of.

So what gives?  Does it actually require multiple frame times to
capture a frame?  (If this is the case, then a still image should be
sampled much better than a moving one, although I hear that it does
a good job on live video.)

Second issue:  calibration.  The card has two jumpers, a variable
capacitor and a variable inductor, and five trimpots.  What do these
adjustments control, and what is the procedure for calibrating the
card?  (I have an oscilloscope and can find a signal generator, but
I need to know the procedure.)

Does anyone have the documentation for this card, and possibly even
the service information?  I'd be happy to pay for copying.

-michael

 Email:  mjmahon@aol.com
 Home page:  http://members.aol.com/MJMahon/