Convert a cross-eye webm to nintendo 3ds stereo video
ffmpeg -y -i "I:\2021-08-23 22-53-57 2 vr_vp9.webm" -r 20 -vcodec mjpeg -qscale 1 -filter_complex "[0:v]split[l][r];[l]crop=w=iw/2:h=ih:x=0:y=0,scale=480:-1,crop=480:240[lo];[r]crop=w=iw/2:h=ih:x=iw/2:y=0,scale=480:-1,crop=480:240[ro]" -map '[ro]' -map '[lo]' "VID_0001.AVI"