Fast and Slow Fades — effect skill for transitions

For AI agents: find the right skill in one call — curl -s "https://varg.ai/how-to/api/search?q=<what the person wants>" returns the matching how-to page and the best skills with install commands, as markdown (Russian works too). Full index: https://varg.ai/how-to/llms.txt. Every page has a markdown twin: add .md to its path. Before generating anything, show the person the options on the how-to page.

Dissolves with a curve: fadefast commits to B early, fadeslow lingers on A. Exist in FFmpeg 7+.

What it does

Like a cross dissolve, but the mix is not linear — the new shot takes over sooner (fast) or later (slow).

When: When a linear dissolve feels mushy in the middle: fadefast keeps the pace up, fadeslow holds an emotional beat.

Watch out: Older FFmpeg builds (6.x and earlier) do not have these names; check ffmpeg -h filter=xfade.

Timing: 0.5–1 s.

Also called: Eased dissolve

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=fadefast:duration=0.5:offset=4.5[v];[0:a][1:a]acrossfade=d=0.5[a]" \
 -map "[v]" -map "[a]" out.mp4

In Remotion

Pass an eased timing to fade(): linearTiming({ durationInFrames: 20, easing: Easing.out(Easing.cubic) }).

Where this comes from

Use when

Not for

Install

Example output

https://s3.varg.ai/how-to/previews/88a4238fa323/take-xfade-fade-fast-slow.mp4 — fadefast between two shots, with the timeline strip of the edit. Footage: Tears of Steel (2012), (CC) Blender Foundation | mango.blender.org, CC BY 3.0; Charge (2022), Blender Studio | studio.blender.org, CC BY 4.0. (credit: Rendered by varg · Tears of Steel (2012) + Charge (2022))

More transitions skills