acl wrote:Steve, how would the MK3 handle eight second SSTV with VIS code included?
It should simply ignore it, it's a modified video line I believe, I'll look into it and make sure that's correct. Which means it may show up on the screen, much like VITC (Vertical Interval Time Code) used in analogue FSTV video recording and editing, though for FSTV it's in the overscan area at the top of the frame/field and shouldn't be visible normally. Same applies to the old teletext system.
If the VIS code is always on the same line it would be a simple task to blank that line...a big if!
Added later:- VIS code is nothing like a standard line, at least in duration, there's also now 16-bit VIS codes just to make things interesting!
There is a VIS code for the ROBOT 8-second mode, either 1, 2 or 3 - for Red, Green, Blue. The Green code is used for monochrome pictures. Same code(s) used for 8 or 7.2s modes.
I think I may have to take back what I said above, "It should simply ignore it..." I'll have to think on how to get it to handle signals with a VIS code, though not actually use it.
Also an updated modulator which can add (or not) the appropriate VIS code, then maybe some of these PC based software applications might spring into life?
Here's a listing of VIS codes, not sure how up-to-date it is, or how accurate, but note the ROBOT 8-second mode is described as 160 lines, 120 columns (pixels?). Also the Wraase 8-second B&W is 120x128, different, yet similar. Different codes too. (Wraase 8-second B&W, 17, 18 & 19) No mention of aspect ratios either.
Steve A.
I'm not going to spend too much time on this VIS matter at this stage, it may be an add-on later.