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 strobe to input.mp4 Second the strobe starts: 1.0 Seconds it runs: 2.0
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 strobe 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 |
|---|---|---|
AT | 1.0 | Second the strobe starts. |
DUR | 2.0 | Seconds it runs. |
ON | 2 | Frames each flash and each black gap lasts. 2 at 30fps is 7.5 flashes a second; 1 is the fastest possible. |
BOOST | 0.12 | How much brighter the flashes are than the normal picture. 0 leaves them unchanged. |
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
In input.mp4, add a strobe from 1.0 to 3.0 seconds. Work at 30fps and count frames from 1.0s (frame 30 of the video is strobe frame 0). Split the strobe into runs of 2 frames: runs 0, 2, 4... (strobe frames 0-1, 4-5, 8-9 and so on) are flashes, where the picture is brightened with ffmpeg's eq filter at brightness=0.12 and contrast=1.2; runs 1, 3, 5... (strobe frames 2-3, 6-7 and so on) are solid black (0, 0, 0) over the whole frame. That gives 7.5 flashes a second for 60 frames, ending on black at frame 89. Before 1.0s and from 3.0s on, the video must be unchanged. Keep the size, 30fps, 6 second length and audio the same. Use ffmpeg and save it as output.mp4 (H.264, yuv420p).Run it without Claude
This is the exact command we tested. Save it as strobe.sh and run:
sh strobe.sh input.mp4 output.mp4Show the command
#!/bin/sh
# Strobe: for two seconds the picture flashes on, brighter than normal, and cuts to black, a few times a second.
# Usage: sh strobe.sh input.mp4 output.mp4
set -e
IN="$1"; OUT="$2"
AT=1.0 # second the strobe starts
DUR=2.0 # seconds it runs
ON=2 # frames each flash and each black gap lasts (2 at 30fps = 7.5 flashes a second)
BOOST=0.12 # how much brighter the flashes are than the normal picture (0 = unchanged)
END=$(echo "$AT + $DUR" | bc)
# while the strobe is live (AT up to END), frames since AT go in runs of ON: even runs are a
# brightened flash, odd runs are covered in black
RUN="floor(((t-$AT)*30+0.5)/$ON)"
LIVE="gte(t,$AT)*lt(t,$END-0.01)"
ffmpeg -y -i "$IN" -vf "fps=30,\
eq=brightness=$BOOST:contrast=1.2:enable='$LIVE',\
drawbox=x=0:y=0:w=iw:h=ih:c=black:t=fill:enable='$LIVE*mod($RUN,2)'" \
-c:v libx264 -crf 18 -pix_fmt yuv420p -c:a copy "$OUT"
