|An enhanced version of the phase visualisation|
ffmpeg contains another great visualisation.
You might (or might not) have seen one of my videos or explanation of the spectrogram visualisation using ffmpeg. I use it very frequently indeed for my youtube videos; so frequently that I felt I really needed something different!
What this does is draw out the phase difference between the left and right channels. If the left the right are the same then it draws a 45 degree slanted line. For each frame of the video it will draw a dot showing the instantaneous magnitude of the signal. However, when left and right channels are different in magnitude this deflects the dot to the left or right.
The dots, once drawn, slowly fade in intensity and colour from blue through to red. Here is the command line to make a mov file from an mp3 without recoding the mp3:
./ffmpeg -i x.mp3 -filter_complex "[0:a]avectorscope=s=1920x1080:bc=200:gc=100:rc=75:bf=5:gf=3:rf=1:zoom=2,format=yuv420p[vid]" -map "[vid]" -map 0:a -codec:v libx264 -crf 1 -preset fast -acodec copy -strict -2 BWV-1031-I.mov
The effect is quite nice for busy music, but becomes much more striking for very simple music. IE, the more notes playing at once the more the effect becomes a shifting colour cloud; the simpler the music, the more we see the trace its self. See there for an example tracing: