FFMPEG Stereo Difference Split and Join

gistfile1.txt

Creates L+R and L-R channels:

ffmpeg -i test.wav -filter_complex "[0:a]channelsplit=channel_layout=stereo[l][r];[r]volume=volume=-1[ri];[l][ri]amix=inputs=2[diff];[0:a]channelsplit=channel_layout=stereo[l][r];[l][r]amix=inputs=2:weights=0.5[add]" -map "[add]" add.wav -map "[diff]" diff.wav

Merges L+R and L-R back into a stereo file, identical to the original input:

ffmpeg -i add.wav -i diff.wav -filter_complex "[1:a]volume=volume=-1[diffi];[0:a][1:a]amix=inputs=2[l];[0:a][diffi]amix=inputs=2[r];[l][r]join=inputs=2:channel_layout=stereo[outpre];[outpre]volume=volume=2[out]" -map "[out]" testout.wav