Audio affecting video...

[Dylan]

My friend just called and had this idea for his band, they want to have a few TV's on stage when they play and on them they'll be playing old Public domain horror movies and stuff, he was wondering if there was any way that if when they play louder they could get the video to kind of wobble/get staticy. Is there anyway to do this?

[LoFi-Ninja]

With computer: Some live VJ software.. You need a good PC

Without: I have no idea.. Try bending a DVD player 

[Gordonjcp]

Wobblevision.

[LoFi-Ninja]

Ahh but can you have wobble on top of a video so you see both ? I think not... 

[Gordonjcp]

Ahh but can you have wobble on top of a video so you see both ? I think not... 

'Course you can.  Get an el-cheapo black and white TV, google the datasheets for the frame oscillator (usually a single chip) and come back and tell me how you figured out how to do it.

[LoFi-Ninja]

Ahh but can you have wobble on top of a video so you see both ? I think not... 

'Course you can.  Get an el-cheapo black and white TV, google the datasheets for the frame oscillator (usually a single chip) and come back and tell me how you figured out how to do it.

Video or it didn't happen ! 

[Tyler1144]

My friend just called and had this idea for his band, they want to have a few TV's on stage when they play and on them they'll be playing old Public domain horror movies and stuff, he was wondering if there was any way that if when they play louder they could get the video to kind of wobble/get staticy. Is there anyway to do this?

I saw this done with something before. All you need to do is get whatever your using to play the movies, hook the video out into a box, and then from the box into the tv. What you do in the box is up to you but i have one idea.

1. Find a distortion pedal or something that is designed to change a sound.

2. De house it, put it in the box.

3. Remove the pedal pot and replace with photocell.

4. Get an audio- out from your instruments and hook it up to an led (may require a resistor)

5. Tape the led and photocell together with electrical tape.

THERE YOU GO, The tv will get distorted depending on how loud you play.

Cost: However much a distortion pedal costs +$15!

[Circuitbenders]

are you suggesting distorting video with an audio distortion pedal?

I don't think thats going to work.

Your idea might work if you found some kind of vision mixer designed for video and hooked an LDR up to one of the controls, even better if the vision mixer had some kind of onboard effects that could be controlled that way.

[Gordonjcp]

If you mounted a large coil of some sort beside each TV and fed it from an audio amp, it would distort the picture in various weird ways depending on the audio you passed to it.  Experiment with driving it with rectified and somewhat smoothed audio, so you are following the envelope of the sound rather than the actual waveform.

There was also an article in Electronics Today International in the early 80s for a TV oscilloscope that basically switched a bright spot on at a point during a scan line depending on the input voltage.  You could sync something like that to an incoming video signal and use that to gate the picture on or off, or switch it negative or something.

Basically to do the oscilloscope thing, you need to detect line sync pulses and lock a sawtooth generator to it - so you've got a 15.625kHz sawtooth (line rate) starting at the lowest level on the left and working its way up as it goes across to the right.  This would give you a gradual black-to-white transition across the screen.  Now the clever bit here is you'd use a comparator to compare your incoming audio signal with the ramp, and use the comparator output to do something to the video.

Clear as mud, right?

Another interesting trick is to use video distortion where you boost the video gain too high and get solarisation, where highlights "fold over" and start becoming darker.