Video Tremolo/Flicker Controller?

technical questions/help
#1

Hi all,

Apologies for my ignorance here, but as some of you know I have spent the better part of the last decade or so making 16mm films, working with analog film gear, teaching 16mm film, and working professionally in film restoration, so even though I am not THAT old I feel like I have a very roundabout/naive way of approaching video synthesis and digital video technology.

That said, I have been spending a good part of the past few months diving into @cyberboy666’s R_E_C_U_R and recurboy, and @andrei_jay’s tools, both on rpi and desktop, and having a blast with them. I am really grateful for scanlines and the community around it and all of the knowledge and creative sharing that happens here.

Lately I have been wondering if there is any kind of existing video device that could provide an “on/off/on/off” type effect, something like very fast switching between source inputs (then one source could be empty or a solid color frame)? Something that mimics a severe tremolo effect

In my analog work I have worked extensively with flicker, both as clear or black frames on a filmstrip or with external motorized shutters in front of a projector. I would be so excited to apply some of these very visceral effects to a live video image.

When I looked into this around 10 years ago things like interlacing and refresh rate seemed to be hurdles to pulling this off in an affordable, elegant way.

Any thoughts or experiences or examples of something like this you all may have would be greatly appreciated. Thanks in advance!

#2

This is very easy to achieve in Coge, the VJ software I use. You can set the opacity of a layer in a layer group to be automated by a squarewave LFO. With a fast tempo: flickering between layers.

Not sure about other VJ software, but I assume they have a way to do this too. Can’t think of any standalone devices off the top of my head (maybe a midi-controllable mixer?) but perhaps others can chime in.

Of course, this is also easy to do with an LZX video synth (same basic principle, automating a mixer with a fast LFO), but I certainly wouldn’t call that option affordable.

#3

this might be a weird suggestion, but i have an idea of how to do this with two video mixers. if you have a no input loop plugged in on one mixer with the channel set to invert, it can generate a flicker between black and white on each new frame. then take that as an input to another mixer with a luma key set up, and use that change in brightness level to key between two images (or color mattes, etc). if the feedback mixer has a strobe effect, it could be used to control the speed of the flicker.

might be weird or not work depending on the mixers etc. i can think of half dozen other ways to do this, and using a raspberry pi to generate the flicker source would probably be much more effective, especially because then you could just generate the matte you want in there, but thought i’d share that answer because i found the idea whimsical. i guess it strikes me as an opportunity to do things in a fun or immediate and spontaneous way rather than going into it with an exact preconceived notion of what you expect to happen which i think is a more fun way to work… just my 2c :slight_smile:

#4

@sean and @palomakop thanks both of you for your thoughts on this, I appreciate it!

Of course, square wave LFO is what I am after, thank you for reminding me that. I am pretty new to this and naive as to how to achieve this still (I can picture it with audio, since I am more familiar with signal chain stuff there).

I love the idea of two mixers achieving this, I am ultimately after something that acts as an instrument that can be played and tweaked, even if it is a little imperfect. I am sort of coming at this from years and years of chaining together effects pedals and feeding mixer channels back into themselves (as I am sure lots of us here are familiar with). I have a WJ-AVE5, I have a lead on a V4 I can borrow. (and yes I agree, part of the attraction of working this way is to keep it ALIVE and a bit unpredictable, rather than total control over the image)

Would love to hear if anyone else has thoughts/experiences, I have to imagine others folks have explored this route before…

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