Category: ideas

Analog video synthesis

Generative art in motion.

ck

https://vimeo.com/cskonopka

By Christopher Konopka

Background

In the past year, Chris has published nearly 2500 improvised video pieces.

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You may be familiar with analog modular audio synthesis. The hardware to produce video looks nearly identical – a maze of patch cords and dials.

Television

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Analog video is television. A CRT (cathode ray tube) resynthesizes video information by demodulating signals from a camera. Vintage televisions have dials to adjust color and vertical sync. When you turn the dials you are synthesizing analog video. Distortion, filtering, and feedback – either at the source (camera) or the destination (tv screen) – offer up an infinite variety of images.

Analog vs. Digital

Today all media is digital. Like the screen you are looking at. The difference with analog is in how it’s produced. Boundaries are less definite. Lines curve. Colors waver. Feedback looks like flames. Every frame is a painting.

Patterns

Images can be generated electronically using modules – without a camera.

Filters

Like with audio sampling, anything is a source. Movies, Youtube, live television, even Felix the Cat.

Feedback

When you aim a guitar at an amplifier it screams. Tilt it away slightly and the screaming subsides. In between there’s sweet spot. The same is true with cameras and screens. Feedback results when output is mixed with input.

Radio

Analog shortwave radio signals are distorted by the atmosphere in a manner similar to video filtering.

A studio in Bethel, Maine.

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An improvised collaboration between Chris and Tom Zicarelli using shortwave radio processed with audio effects.

Live Performance

Gem

A recent screen test at the Gem Theatre in Bethel, Maine. Source material is a time lapse film of a glacier installation – produced at the same theatre – by Wade Kavanaugh and Steven Nguyen. https://www.youtube.com/watch?v=6c36Y-Dcj30  The film was re-synthesized using analog video and feedback. Soundtrack by Tom Zicarelli.

Big screen equals mind bending experience.

Note: previous clip excerpted from this 15 minute jam: https://vimeo.com/177843310

TAL

The patterns in this clip appear to be three dimensional. They are not.

From a show that happened somewhere in the known universe:

Alto

Improvised analog video with the band “Alto”. Patterns reminiscent of magical textiles.

More about analog video synthesis

 

Teufelsberg

An acoustically interesting dome in an abandoned spy station at the highest point in Berlin.

dome

We ran into flutist Thomas Von Der Brücke in the woods around Teufelsberg. Thomas has often recorded and performed in the dome. He invited us to come along for a tour.

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Thomas on Flute…

Thomas on vocals and flute, with me on percussion

 

Photographs by Rebecca Zicarelli

Glacier Sounds

Overlapping loops of varying duration to represent natural cycles.

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In October I collaborated with Wade Kavanaugh and Stephen P. Nguyen to compose and perform the sounds of a glacier for their installation at the Gem theatre in Bethel, Maine. The glacier was made from paper.

Wade and Stephen:

wadeandsteven

A time-lapse video of the project:

A time-lapse video of a similar project they did in Minnesota 2005:

The approach was to take a series of ambient loops and organize them by duration. The longer loops would represent the slow movement of time. Shorter loops would represent events like avalanches. One-shot samples would represent quick events, like the cracking of ice.

It took several iterations to produce something slow and boring enough to be convincing. I used samples from the Ron MacLeod’s Cyclic Waves library from Cycling 74 https://www.ableton.com/en/packs/cyclic-waves/. Samples were pitched down to imply largeness.

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Each vertical column in an Ableton Live set represents a time-frame of waves. That is, the far left column contains quick events and the far right column contains long cycle events. Left to right, the columns have gradually increasing cycle durations.  I used a Push controller to trigger samples in real time as people walked through the theatre to see the glacier.

The theatre speakers were arranged in stereo but from front to back. Since the glacier was also arranged along the same axis, a slow auto-panning effect sent sounds drifting off into the distance, or vice versa. Visually and sonically there was a sense that the space extended beyond the walls of the theatre.

In the “control room” above the theatre… using Push to trigger samples and a Korg NanoKontrol to set panning positions of each track:

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The performance lasted about 45 minutes. Occasionally the cracking of ice would startle people in the room. There were kids crawling around underneath the paper glacier. Afterwards we just let the sounds play on their own. A short excerpt:

 

Photographs by Rebecca Zicarelli.

Motorized potentiometers

And other ways to remotely control existing dials.

Suggestions from robotshop.com: http://www.robotshop.com/forum/post-p101569

 

Motorized potentiometers

from p3america: http://www.p3america.com/motorized_potentiometers_text.htm?gclid=CJSetfSYusUCFdOQHwodPEUAaw

Screen Shot 2015-05-11 at 1.38.41 PM

 

From Online Controls: http://www.onlinecontrols.com/mpots.htm

 Motorized faders

Sparkfun motorized fader (like the kind used in DAW control surfaces) https://www.sparkfun.com/products/10976

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Servo control and sensing

from electronics stack exchange: http://electronics.stackexchange.com/questions/60272/servo-controlled-potentiometer-using-rotary-position-sensor

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notes

The Potentiometer Handbook by Carl David Todd: https://www.bourns.com/pdfs/onlinepotentiometerhandbook.pdf

Google search: servo to turn a knob

Shower temperature control from SmithyTech: http://smithytech.com/?p=5

Arduino HVAC Servo Thermostat/Controller by tikka308: http://www.instructables.com/id/Arduino-HVAC-Servo-ThermostatController/

What kind of motor would I need to turn this central heating valve? http://electronics.stackexchange.com/questions/97269/what-kind-of-motor-would-i-need-to-turn-this-central-heating-valve – observations about the difficulty of using robots to turn knobs

Sous vide cooker with feedback control: http://www.nerdkits.com/videos/sous-vide/

servobox01_t

Homemade Electric Telescope Focuser: http://emediadesigns.com/focuser/

 

Use your Raspberry Pi to move parts of a robot or control anything that can rotate – by Rob Zwetsloot http://www.linuxuser.co.uk/tutorials/control-servos-with-a-raspberry-pi

Substituting components in parallel

Resistance and capacitance in an AM radio.

A first test to find out if its practical to ‘piggyback’ external controls on to an existing radio. The reason for doing this is to leave an original radio intact by clipping the remote components to the leads of the existing controls.

For example a varactor would be connected in parallel to the variable capacitor already in the circuit. The existing capacitor would be set low. The capacitance of the varactor would then be added to the total, using the formula for parallel capacitors.

For potentiometers, its not as easy because parallel resistors are divided:

ParallelWiderstaende

Formula:  Rtotal = R1×R2/(R1+R2)

For example if R1 is 10K, R2 would need to be 100K to get a total resistance of 9K. To get 99% of the existing resistance, the piggyback resistor needs to be 100 times the value of the existing resistor. 1 MegOhm if matched with 10K.

Practical considerations

What happens when the radio is not being controlled remotely?

  • For capacitance, the remote capacitor (varactor) should be set to 0.
  • For resistance, the remote resistor should be set as high as possible.

Conversely, how should the physical controls on the radio be set when operating remotely?

  • Variable capacitors should be set as low as possible.
  • Potentiometers should be set as high as possible. For a volume control this actually means turning the volume all the way down.

Switches

SPST switches can be considered as a form of potentiometer with infinite resistance. A piggybacked switch will only work if the existing switch is in the ‘off’ position. And vice-versa.

Double-Throw and Rotary switches present more difficulties as multiple states are maintained by the same device.

I don’t think multiple throw switches can be piggybacked. Two possible solutions:

  • mechanical connection to manual control (servo)
  • internal relays – requiring modification of the radio, so that the existing control and the remote control operate the same relays
  • Hybrid approach: Operate the switches manually while operating other controls remotely.

Testing

I piggybacked a tuning capacitor from an AM radio onto the tuning capacitor of a vintage Radio Shack Globe Patrol (regenerative receiver).