For a list of .mp4 files in a directory:

for i in $( ls ); do ffmpeg -i $i -filter:v \
  "setpts=0.003*PTS" -threads 4 -an -map_metadata 0\
  -map_metadata:s:v 0:s:v -map_metadata:s:a 0:s:a _$i\
  && exiftool "-filemodifydate<mediacreatedate" _$i; done