Canon EOS-1D X Mark III Advanced User's Manual page 895

Sound is not recorded in movies.
Sound is not recorded in High Frame Rate movies.
A time code is not added.
Time codes are not added when you record High Frame Rate movies with [Count up] in
[ : Time code] set to [Free run] (
video output (
Time codes advance faster than the actual time.
Time codes in High Frame Rate recording advance 4 sec. per second (
I cannot take still photos during movie recording.
Still photos cannot be taken during movie recording. To take still photos, stop the movie
recording and perform viewfinder shooting or Live View shooting.
).
). Additionally, no time code is added to HDMI
895
).