Get this effect
Switch to Code in your Claude Desktop App
Install the skill (once)
Show the prompt
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
Add a back-and-forth loop to input.mp4 Second of the input the slice starts at: 2.0 Seconds of the input in the slice: 3.0
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.
Add a back-and-forth loop to @clip1.mp4, put a sale badge on @clip2.mp4, give @clip3.mp4 a VHS look, then join all three with crossfades.
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 |
|---|---|---|
START | 2.0 | Second of the input the slice starts at. |
SLICE | 3.0 | Seconds of the input in the slice. |
SPEED | 3 | How many times faster than real time the slice plays. 3s at 3x makes a 1-second pass. |
TIMES | 3 | Forward-and-back cycles in the output. Three 2-second cycles make 6 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
Make a boomerang (back-and-forth loop) from input.mp4 (540x960, 30fps, 6 seconds). Take the slice from input second 2.0 to 5.0 and speed it up 3x so it plays in 1 second (30 frames, keeping every third input frame: input frames 60, 63, 66 ... 147). Play those 30 frames forward, then the same 30 frames in reverse, and repeat that forward-then-backward cycle 3 times, so the output is exactly 6 seconds (180 frames): output 0-1s shows input 2.0s to 4.9s, output 1-2s shows input 4.9s back to 2.0s, and the same again for 2-4s and 4-6s. Don't crop, zoom or add anything to the picture, and don't add any text. For the sound, keep the input's own audio playing normally from 0 to 6 seconds (don't reverse or speed it up). Use ffmpeg, keep the size, frame rate and audio, and save it as output.mp4.Run it without Claude
This is the exact command we tested. Save it as back-and-forth-loop.sh and run:
sh back-and-forth-loop.sh input.mp4 output.mp4Show the command
#!/bin/sh
# Back-and-forth loop: a slice of the clip plays forward fast, then backward, three times over, under the clip's own sound.
# Usage: sh back-and-forth-loop.sh input.mp4 output.mp4
set -e
IN="$1"; OUT="$2"
START=2.0 # second of the input the slice starts at
SLICE=3.0 # seconds of the input in the slice
SPEED=3 # how many times faster than real time it plays (3s at 3x = a 1s pass)
TIMES=3 # forward-and-back cycles in the output
FPS=$(ffprobe -v error -select_streams v:0 -show_entries stream=r_frame_rate -of csv=p=0 "$IN")
PASS=$(awk "BEGIN{print $SLICE / $SPEED}") # seconds one forward pass takes
FRAMES=$(awk "BEGIN{print int($PASS * $FPS * 2 + 0.5)}") # frames in one forward-and-back cycle
LENGTH=$(awk "BEGIN{print $PASS * 2 * $TIMES}") # output length in seconds
REPEATS=$((TIMES - 1)) # cycles after the first
ffmpeg -y -v error -i "$IN" -filter_complex "
[0:v]trim=start=$START:duration=$SLICE,setpts=(PTS-STARTPTS)/$SPEED,fps=$FPS,split[fwd][back];
[back]reverse[rev];
[fwd][rev]concat=n=2:v=1:a=0,loop=loop=$REPEATS:size=$FRAMES,setpts=N/($FPS)/TB[v];
[0:a]atrim=0:$LENGTH,asetpts=PTS-STARTPTS[a]" \
-map "[v]" -map "[a]" -r "$FPS" -c:v libx264 -crf 18 -pix_fmt yuv420p -c:a aac "$OUT"
