Circle Crop Through Black — effect skill for transitions

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A closes to a circle on black, then B opens from it — the cartoon “that’s all folks” beat.

What it does

Built on Iris Wipe by Kapish Dima (remocn), MIT. The write-up and recipes below are varg's.

The frame shrinks to a circle, the screen goes black, and a circle grows into the next shot.

When: A playful end of scene, comedic beats, retro edits.

Watch out: Using it in a serious piece; it always reads as a gag.

Timing: 0.8–1.2 s.

Also called: Iris out / iris in, Circle close

In FFmpeg

Both inputs need the same size, frame rate, timebase, SAR and pixel format (settb=AVTB fixes the timebase error that fps alone leaves). offset is where the transition starts on the first clip's timeline (its length minus the overlap).

ffmpeg -i a.mp4 -i b.mp4 -filter_complex \
 "[0:v]fps=30,scale=1920:1080,setsar=1,settb=AVTB,format=yuv420p[a];[1:v]fps=30,scale=1920:1080,setsar=1,settb=AVTB,format=yuv420p[b];\
  [a][b]xfade=transition=circlecrop:duration=0.5:offset=4.5[v];[0:a][1:a]acrossfade=d=0.5[a]" \
 -map "[v]" -map "[a]" out.mp4

In HyperFrames

Two clip-path tweens: circle(75% at 50% 50%) → circle(0%) on A, then the reverse on B.

In CapCut

Transitions → Mask → Circle twice, through a black frame.

Ready-made components

Where this comes from

Use when

Not for

Install

Example output

https://s3.varg.ai/how-to/previews/8b9e2ae88080/take-xfade-circle-crop.mp4 — circlecrop between two shots, with the timeline strip of the edit. Footage: Charge (2022), Blender Studio | studio.blender.org, CC BY 4.0; Tears of Steel (2012), (CC) Blender Foundation | mango.blender.org, CC BY 3.0. (credit: Rendered by varg · Charge (2022) + Tears of Steel (2012))

More transitions skills

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