wave form from audio

audio.gpi

#set output format and size
set term png size 320,180

#set output file
set output "audio.png"

# set y range
set yr [-1:1]

# we want just the data
unset key
unset tics
unset border
set lmargin 0             
set rmargin 0
set tmargin 0
set bmargin 0

# draw rectangle to change background color
set obj 1 rectangle behind from screen 0,0 to screen 1,1
set obj 1 fillstyle solid 1.0 fillcolor rgbcolor "#222222"

# draw data with foreground color
plot "audio_only.dat" with lines lt rgb 'white'

wave-form.sh

ffmpeg -i video.avi -vn -acodec copy output-audio.mp3

sox output-audio.mp3 audio.dat #create plaintext file of amplitude values
tail -n+3 audio.dat > audio_only.dat #remove comments

# write script file for gnuplot
echo set term png size 320,180 > audio.gpi #set output format
echo set output \"audio.png\" >> audio.gpi #set output file
echo plot \"audio_only.dat\" with lines >> audio.gpi #plot data

gnuplot audio.gpi #run script