[sdiy] Modular Video?

[Rotwang the Mad Inventor]

Peace to all,
this strange morning... :-/

Videosynthesis interest me a lot. I really like to see a discussion tread 
on the subject, and the opportunity to take part of any experience in the 
field people may have.

Until recently, I have been working at Swedish Television at technical 
development. Thirty years ago my father worked there too, as a scanner 
operator /production technician. Stories I have heard from him as well as a 
few of the oldtimers at STV tells about weird experiments with the 
telecine/scanner apparatus in the late 60s. This could be considered as one 
of the first videosynthesisers ever made. The process is said to have 
involved several signal- and tonegenerators hooked up and hacked directly 
into the deflection cirquits of the telecine and scanner apparatus, thereby 
distorting the image material. The idea was to take material on film, scan 
it in a nonlinear pattern, record onto videotape (Yeah, Ampex 2"!), and 
then print back to film and so on. Round and round. The first experiments 
were made in b/w , never aired due to controversities with the broadcast 
company management, later on they made new attempts in color which my 
father tells me about - it seems to have been a pain in the *ss to 
recalibrate the machines efterwards...

I dug up something whicch seems like a homepage of one of the involved artists:
http://www.monumentintime.homestead.com/

To me there seems to be different approaches to image synthesis:

The "calligraphic" matematical representation of an image as an x/y plot. 
Just like those lissajous figures and filter "scope art" that may be found 
on PAiAs website for example.
The use of lasers and mirrors in the rave scene as well as JM Jarre also 
belongs to this kind of visual synthesis.

Another kind of visual synthesis would be manipulation of the line-scan 
video signal itself. There seem to have been video manipulating devices 
which operate directly on the composite video signal, but the more flexible 
machines first decodes the PAL/NTSC video signal into component signals. At 
least one have to separate sync signals, luminance and color information. 
With Y (luminance) and C (croma) separated, colour shift is easily achieved 
through simple phase shifting. For those of you that don't know, colour 
information is phase-modulated on a separated carrier wave.
Converting the signal into full components, RGB, would enable the signal to 
be processed in a fashion much like audio through a modular music 
synthesiser. You need a little more bandwidth on the modules though... :-)

My own upcoming experiments with video synthesisers will be centered around 
a hacked processing amplifier kit from Velleman (www.velleman.be). It uses 
Philips decoder/encoder TV chips to decode the composite signal into RGB 
and/or Y/C,  and separate sync, then pass it through variable amplification 
to adjust hue, intensity and contrast, then convert it back to composite 
again. By "modularising" this box, I will have a PAL/NTSC encoder/decoder 
at low cost and little hassle. Then my intentions are to find (analogue of 
course!) ways to process these signals by quantising, low/high pass 
filtering, shifting colours, nonlinear amplification, chroma-keying and so on.

Another idea I am having is a device to convert the x/y representation of a 
function into raster-scan signal. I guess I could just put a camera in 
front of an oscilloscope screen, creating a quik-n-dirty scan converter, 
bit I would lika an all electronic and less space-consuming approach. I 
have an idea, without using lots of RAM as a framestore, but it will most 
likely generate wierd results when using input signals close to the scan 
frequencies and its multiples. But hey, weird results - isn't that what I'm 
looking for in the first place?! :-)

A fellow analog-enthusiast (video, synthesisers, vintage mopeds...) of mine 
have a nice link collection on the subject.
http://www.mkv.mh.se/personal/per/videosynth/index.html

You will find a link to my videosynth ideas at the top. Note that there are 
mostly ideas, not much tried out in real world. I will have a go at the 
x/y-converter as soon as I get some free time from all this digital signal 
processing crap at work... ;-)

Speaking of video... and the miserable things happening in the US now, I 
noted that not just buildings were falling apart, the video signals were 
crumbling to bits too! Arghhh, this damn compression stuff is spreading 
like disease through the broadcast world... :-(
Well I guess there are more important  things to worry about just now than 
low bitrate... :-(

Take care, all of you!
And remember that one of the most uniting factors of people all over the 
world is music. Perhaps also synth-DIY.
Swing the soldering iron for peace on earth!

                 my humble thoughts this strange morning

                 /Patrik the Mad Inventor (didn't sleep much tonight)