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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
Add a scrolling spectrogram to input.mp4 Palette: fiery
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 scrolling spectrogram 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 |
|---|---|---|
BAND | 0.20 | Spectrogram height as a share of the frame height. |
Y | 0.75 | Top of the spectrogram, 0-1 down the frame. |
SPEED | 160 | Scroll speed in pixels per second. Faster makes each hit wider and the history shorter. |
PALETTE | fiery | showspectrum color map: fiery, fire, magma, plasma, viridis... |
TOP_HZ | 8000 | Highest frequency shown; low notes sit at the bottom. |
SHADE | 0.7 | Opacity of the dark strip behind the spectrogram. |
RANGE | 80 | Loudness range shown, in dB. Lower hides quiet sounds. |
Without the skill
Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the command itself.
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In input.mp4 (540x960, it has a drum track), add a scrolling spectrogram of the audio near the bottom. Darken a full-width strip from y=720 to y=912 (192 pixels tall) with black at 70% opacity. Over that strip, place a 540x192 spectrogram made with ffmpeg's showspectrum filter from the input's own audio: slide=scroll (new sound enters at the right edge and moves left), 160 columns per second (fps=160, then resample to 30fps), color=fiery, scale=log, fscale=log, stop=8000 Hz, drange=80. Make its black (silent) parts transparent with colorkey=black:0.04:0.1 so the video shows through the gaps. Leave everything above y=720 and below y=912 untouched. There's no text; if you add any, draw it with Pillow, not ffmpeg's drawtext. Keep the size, 30fps, 6 second length and the audio. Save it as output.mp4.Run it without Claude
This is the exact command we tested. Save it as scrolling-spectrogram.sh and run:
sh scrolling-spectrogram.sh input.mp4 output.mp4Show the command
#!/bin/sh
# Scrolling spectrogram: a red-to-yellow map of the soundtrack's frequencies scrolls right to left along a dark strip near the bottom.
# Usage: sh recipe.sh input.mp4 output.mp4 (the input needs an audio track)
set -e
IN="$1"; OUT="$2"
BAND=0.20 # spectrogram height as a share of the frame height
Y=0.75 # top of the spectrogram (0-1 down the frame)
SPEED=160 # scroll speed in pixels per second
PALETTE=fiery # showspectrum color map: fiery, fire, magma, plasma, viridis...
TOP_HZ=8000 # highest frequency shown; low notes sit at the bottom
SHADE=0.7 # opacity of the dark strip behind the spectrogram
RANGE=80 # loudness range shown, in dB: lower hides quiet sounds
SIZE=$(ffprobe -v error -select_streams v:0 -show_entries stream=width,height -of csv=s=x:p=0 "$IN")
W=${SIZE%x*}; H=${SIZE#*x}
SH=$(echo "$H * $BAND / 2 * 2" | bc) # even height for the spectrogram strip
TOP=$(echo "$H * $Y / 1" | bc)
# showspectrum adds one column per audio window and slides the picture left; colorkey makes the silent
# (black) parts see-through, so only the sound shows over a darkened strip of the video
ffmpeg -y -i "$IN" -filter_complex "\
[0:a]showspectrum=s=${W}x${SH}:slide=scroll:mode=combined:color=$PALETTE:scale=log:fscale=log:stop=$TOP_HZ:drange=$RANGE:fps=$SPEED,\
fps=30,format=rgba,colorkey=black:0.04:0.1[spec];\
[0:v]drawbox=x=0:y=$TOP:w=$W:h=$SH:color=black@$SHADE:t=fill[bg];\
[bg][spec]overlay=0:$TOP:shortest=1,format=yuv420p[v]" \
-map "[v]" -map 0:a -r 30 -c:v libx264 -crf 18 -c:a copy "$OUT"
