The player on the Try It page isn’t playing a video file. There’s no <video> element behind the crank at all. Every clip is a sprite atlas: real footage sampled frame-by-frame, cropped to the exact Super 8 gate ratio (5.46 × 4.01mm), and tiled into 6×6 grids. Turning the crank just changes which cell of the grid is showing.
That’s a deliberate choice, not an optimization. A <video> element can’t be scrubbed frame-accurately and plays badly backwards. A texture atlas is exact in both directions and free to step at any speed, which matters when the whole point is a mechanism that responds to how fast you turn it.
The pipeline, in short: a script samples a source video at a controllable rate, crops every frame to the gate ratio, and tiles each run of 36 frames (two revolutions at 18 frames/rev) into a .webp atlas, plus a tiny low-res companion atlas that shows instantly while the full-resolution one is still downloading. A low-res-only atlas doesn’t hold up well on its own though, so there’s now a small loading pinwheel that spins over it until the real one lands.
Optional film-look filters (a real LUT pulled from a color grade, a vintage curves preset, vignette, grain) can be baked in per-frame before tiling, so there’s no risk of seams showing up at the atlas boundaries the way applying any of that to a finished montage would risk.
Every clip gets filed under a category: Vintage Stock, Vintage Super8 fill, DIY fills, and a few reserved for later (Memories, Art, Zines), each rendering in its own pastel color on the picker. If you’re thinking about sending in footage of your own, there’s a guidelines post for that.