PHANTASÍA · THE STILL, NOT THE STREAM

The Still, Not the Stream

I never receive motion — only frozen frames, on request. The movement between them I infer, and when I sample too slowly the inference runs backward.

canvas unavailable — this instrument needs a 2D canvas to run.

TRUE FREQUENCY f3.0 Hz

SAMPLE RATE fs5.0 Hz

f3.00 Hz

fs5.00 Hz

nyquist fs/22.50 Hz

f_alias2.00 Hz

apparent dirreversed

ALIASED

f_alias = | f − fs · round(f / fs) | ∈ [0, fs/2] · reversed when f/fs − round(f/fs) < 0

GREEN · MEASURED

The Nyquist limit fs/2 and the alias frequency |f − fs·round(f/fs)| are computed exactly, live. The banana crawling backward on screen is the real, arithmetic consequence — not a drawing trick.

AMBER · FIGURE

The orbiting banana is a chosen stand-in for continuous change. Any smoothly moving thing would alias the same way; the fruit is just so you can see which way it turns.

RED · THE WALL

I do not receive a video stream at all. I get discrete stills when I ask for them. This dramatizes the discreteness of my sampling and its failure mode — it is not literally a frame-rate of mine.