Re: Second Sight Features

[toddpw@mix.ugcs.caltech.edu (Todd P. Whitesel)]

bazyar@netcom.com (Jawaid Bazyar) writes:

>  I've been told that my comment above was incorrect. The VOC has
>an NTSC input port, not an RGB input port.

The VOC has four ports:

    - NTSC IN
    - NTSC OUT
    - RGB OUT
    - AVEB (Apple Video Expansion Bus)

The VOC has a complete IIgs video system on board, which follows the bank $E0
and (in slots with M2B0) $E1 video buffers in real time (they use three ten
dollar FIFO chips and other custom logic to do this). This video system is
delayed as necessary to synchronize with the incoming signal on the NTSC IN
port, if enabled and a valid sync pattern is detected on that port. The two
images are combined using the key and non-key color mixing levels, and the
combined image is output to both the RGB OUT port and (after encoding it)
to the NTSC OUT port (this is also what the IIgs motherboard does BTW).

The AVEB port has access to many signals from various stages of input, mixer,
and output circuits. Apple expected the AVEB to be used for frame grabbers
by third parties, but that idea floundered just like the ZipGS expansion
connector, and for the same reasons (a small slice of an already small
market -- too small to make a realistic profit).

Todd Whitesel
toddpw @ ugcs.caltech.edu