The frame is read out as a signal, sample by sample, and pushed through the things a sound goes through — a delay with feedback, a one-pole filter, a wavefolder — and what comes back is painted. Pull the knobs.
How much of the bent signal is mixed back over the original.
The delay time. Short smears within a line; long drags the damage down the frame. It only does anything once there is feedback to bring it back.
How much of the delayed signal is fed back in. This is what turns a smear into repeats.
One pole of filtering: heavy lag and dark damage at the bottom, all edges and grain at the top.
Drive into a triangle wavefolder. Past full scale the signal comes back instead of flattening, which is why it keeps detail where clipping turns to mush.
The picture is played through a real audio chain rather than stamped with a canned "glitch texture", so the damage belongs to your image: a short delay smears along a line, a long one drags it down the frame, and the feedback repeats it.
The picture keeps its own detail and gains the damage, rather than going soft. The same effect runs live on a cue inside Deckboy, fast enough to sit inside a frame at 1080p — so you can put it on something going to air, not just on a photo.
If the picture really is a signal, it can go to a speaker instead of a screen. Hear the picture plays your image as about four seconds of sound. A flat sky is a drone, a crosshatch is a tone, a busy frame is noise — and the delay and feedback you set are audible as repeats, because that is exactly what they are.
It is high-passed at 30 Hz before it plays, for the same reason a chip synthesiser is: an asymmetric signal sits off centre, and a signal that starts and stops off centre clicks rather than sounds.
In Deckboy this is a knob on a cue, so it runs on a clip, a camera, a captured window or a web page while the show is going out, with every parameter drivable from an oscillator. Its opposite number, audioprint, goes the other way: it draws the audio the deck has just played through the picture. Put one of each on the same cue and they bend each other.
Deckboy is free and open source, for Windows, macOS and Linux — a cue deck for live video, with clips, slides and live sources on one cue list and output to a screen, NDI, SRT, Blackmagic SDI or SMPTE ST 2110.