Get this effect
Switch to Code in your Claude Desktop App
Install the skill (once)
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Install the Recharm video effects skill: download https://recharm-growth-staging.s3.us-east-2.amazonaws.com/website/downloads/recharm-video-effects.zip and unzip it into ~/.claude/skillsAsk for the effect
Join clipA.mp4 and clipB.mp4 with a fade through gray Length of the transition in seconds: 1.0
Several videos, several effects, one ask
Put your clips in the folder, mention them with @, and ask for everything at once. Claude runs one tested script after another on each clip, then joins them.
Put a sale badge on @clip1.mp4, give @clip2.mp4 a VHS look, then join them with a fade through gray.
Settings you can change
Ask Claude to change any of these, or edit them at the top of the command.
| Setting | Default | What it does |
|---|---|---|
D | 1.0 | Length of the transition in seconds. |
Without the skill
Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the command itself.
Show the prompt
Join clipA.mp4 and clipB.mp4 with a 1.0 second fade through gray starting 1.0 second before the end of A: A desaturates to black and white, the grayscale picture dissolves into grayscale B, then B's color returns (ffmpeg xfade transition=fadegrays, duration 1.0). Crossfade the audio over the same 1.0 second. Match B's size and frame rate to A. Use ffmpeg, keep H.264 yuv420p and save it as output.mp4.Run it without Claude
This is the exact command we tested. Save it as fade-through-gray.sh and run:
sh fade-through-gray.sh clipA.mp4 clipB.mp4 output.mp4Show the command
#!/bin/sh
# Fade through gray: clip A drains to grayscale, the gray picture dissolves into clip B, and B's color returns, over 1s. The sound crossfades underneath.
# Usage: sh fade-through-gray.sh clipA.mp4 clipB.mp4 output.mp4 (both clips need an audio track)
set -e
A="$1"; B="$2"; OUT="$3"
D=1.0 # transition length in seconds
LEN=$(ffprobe -v error -show_entries format=duration -of csv=p=0 "$A")
OFFSET=$(echo "$LEN - $D" | bc)
SIZE=$(ffprobe -v error -select_streams v:0 -show_entries stream=width,height -of csv=s=x:p=0 "$A")
FPS=$(ffprobe -v error -select_streams v:0 -show_entries stream=r_frame_rate -of csv=p=0 "$A")
W=${SIZE%x*}; H=${SIZE#*x}
# xfade needs both clips at the same size and frame rate, so B is fitted to A first
ffmpeg -y -i "$A" -i "$B" -filter_complex "\
[0:v]fps=$FPS,format=yuv420p,setsar=1[a];\
[1:v]scale=$W:$H:force_original_aspect_ratio=increase,crop=$W:$H,fps=$FPS,format=yuv420p,setsar=1[b];\
[a][b]xfade=transition=fadegrays:duration=$D:offset=$OFFSET[v];\
[0:a][1:a]acrossfade=d=$D[au]" \
-map "[v]" -map "[au]" -c:v libx264 -crf 18 -pix_fmt yuv420p -c:a aac "$OUT"
