# Fast and Slow Fades — effect skill for transitions

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

- **Type:** [Effect](https://varg.ai/how-to/effects.md) · [Transitions](https://varg.ai/how-to/browse/skills/transitions.md)
- **Slug:** `xfade-fade-fast-slow`
- **Status:** live
- **Publisher:** varg (varg, verified)
- **License:** MIT
- **Source:** https://github.com/vargHQ/skills/blob/main/varg-video-edit-library/references/transitions.md#xfade-fade-fast-slow
- **Works in:** Claude Code, Claude.ai, Codex, Cursor, OpenClaw, Gemini CLI, Any MCP client, varg Studio
- **Requires:** ffmpeg, Remotion
- **Cost:** Free — the take renders locally; generated footage, if any, bills by the model

## 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).

```bash
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

- [FFmpeg filters: xfade](https://ffmpeg.org/ffmpeg-filters.html#xfade)
- [FFmpeg xfade gallery (trac wiki)](https://trac.ffmpeg.org/wiki/Xfade)
- [Remotion transition presentations](https://www.remotion.dev/docs/transitions/presentations)

## Use when

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

## Not for

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

## Install

- Claude Code: `claude plugin marketplace add vargHQ/skills && claude plugin install varg@varg`
- Codex: `npx skills add vargHQ/skills --skill varg-video-edit-library -a codex -y`
- Cursor: `npx skills add vargHQ/skills --skill varg-video-edit-library -a cursor -y`

## 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

- [editly](https://varg.ai/how-to/skills/editly.md): Declarative JSON5 video editing CLI/API: clips, titles, transitions, audio mixing, rendered with ffmpeg.
- [Mix (Cross Dissolve)](https://varg.ai/how-to/skills/mix-dissolve.md): The two shots blend through each other. The quietest transition: "time passes" or "this continues".
- [Dip to Black](https://varg.ai/how-to/skills/black-fade.md): A fades to black, then B fades up. Marks the end of a section or a bigger jump in time.
- [White Flash](https://varg.ai/how-to/skills/white-flash.md): The frame blows out to white for a moment and opens on the next shot. Energy, memory or a camera snap.
- [Pull In (Zoom In)](https://varg.ai/how-to/skills/pull-in-zoom.md): The camera rushes into shot A and lands, still moving forward, in shot B. The signature short-form transition.
- [Pull Out (Zoom Out)](https://varg.ai/how-to/skills/pull-out-zoom.md): The camera jerks backwards out of shot A and keeps pulling back as shot B settles in.