The PD modes are well-established hi-res colour modes for SSTV.
In digesting the specifications for these I notice there is no mention of vertical sync. There is mention of VIS codes, I cannot see why these couldn't replace the usual vertical sync. That assumes the VIS code is transmitted at the start of every frame, no problem there. It does possibly mean a somewhat different line (or insert shall we say) at the start of each frame, again no problem.
But so far I haven't been able to find any documented example of how this is done. I have quite a bit of data regarding this, but it's not very explicit. e.g. "VIS Codes Dayton Paper", particularly the PD section (attached).
Having downloaded a few PD mode files I was going to 'reverse engineer' these via a SSTV demodulator and 'scope and see what I might find. Though it's not the best way to get data.
Alternatively I was going to contact Paul Turner again and ask. But I'd rather not take up his time unless I really have to.
Can anyone here enlighten me? Has there been any updates to the version attached here. (Dayton SSTV forum, 20 May 2000).
Steve A.