[sdiy] Video-synth DIY ?

[Tony Clark]

   Hi CJ,

> Does/ has anybody here tinkered with making video synths or processors?

   I have dabbled just a tiny bit...  :)  I too have a huge interest in 
video synthesis, if nothing more than for audio visualization.

> I am aware that video signals run faster, with the various components
> synchronized together. What I have read on the topic at
> AudioVisualizers and other sites is not terribly specific about
> implementation. A lot of the older systems (circa 1968-1974) appeared
> to be analog modular (audio) synths which had interfaces hacked into
> video scan modulators, ramp generators, etc. Lots of emphasis on
> oscillators being "phase locked", which I'd guess is like hard sync?

   The concept is very similar to audio synthesis, but there are some 
distinct differences.  First, as you mentioned, everything runs much 
faster and is typically synced to a master clock.  Actually, there are 
two distinct clocks, vertical and horizontal refresh rates.  You can also 
have a pixel clock, but these run _really_ fast and need special care to 
avoid EMI issues.  But really depending on what effect you are after, 
you'll use a combination of both horizontal and vertical refresh clocks 
to time everything with.
   Another difference from audio side is that the circuitry needs to be 
free of temperature drift.  This would mean that linear oscillators (or 
phase accumulators) would be preferred over the expo type in normal 
modulars.

> Thinking ahead, since I will have a few panels together this year, I am
> wondering how I can interface these to video gear. My computers are not
> fast enough for most video stuff I have tried, and I am less inspired
> by the After Effects and Arkaos ways of doing things. NATO or Jitter
> would be fun, but are too expensive for me now, and I'd need a faster
> computer. So I am determined to learn more about video synth DIY. I
> currently have way too much stuff on my plate to fix, mod, and build -
> so I will start messing around with this stuff next year.

   It's not difficult to interface to things such as a VGA computer 
monitor, but is definately trickier to interface to a TV (NTSC/PAL).  
Timing is everything and there are too many standards, unfortunately!

> I'd be more than psyched to hear of anybody's experiences with such
> things!

   I hope to have something to show later this year, but currently I have 
to get a contract manufacturing job completed first before I can devote 
any time to it.
   BTW, I would be highly interested in any schematics or information 
about classic video synths.  I've scoured the net and haven't really 
found much...

   Cheers,

   Tony

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