`showcqt’ (separating channels)

Watch on youtube.com

doc

https://ffmpeg.org/ffmpeg-filters.html#showcqt, https://ffmpeg.org/ffmpeg-filters.html#pan

#! /bin/sh
ifn="Air on the G String (from Orchestral Suite no. 3, BWV 1068).mp3"
ifnb="`basename \"${ifn}\" .mp3`"
pref="`basename $0 .sh`"

#
ffmpeg -y -i "${ifn}" -filter_complex "
[0:a]pan=stereo|c0=c0|c1=c0,showcqt=s=1920x540[vcqt_L];
[0:a]pan=stereo|c0=c1|c1=c1,showcqt=s=1920x540[vcqt_R];
[vcqt_L][vcqt_R]vstack[v]
" -map '[v]' -map '0:a' -c:a copy \
  "${pref}_${ifnb}.mp4"