Canon EOS-1DX Instruction Manual page 246

3 Setting the Time Code
Regardless of the [Movie rec count] setting, the time code will always be
recorded to the movie file.
Movie Playback Count
You can select what to display on the movie playback screen.
[Rec time] : Displays the recording time and playback time during
movie playback.
[Time code] : Displays the time code during movie playback.
With [Time code] set:
During movie shooting
If you change the setting for either [Movie play count] in [z5 (movie):
Time code] or for [x3: Movie play count], the other setting will also
change automatically.
"Frames" are not displayed during movie shooting and movie playback.
Drop Frame
If the frame rate setting is 6(29.97 fps) or 8(59.94 fps), the time
code's frame count causes a discrepancy between the actual time and
time code. This discrepancy can be corrected automatically. This
correction function is called drop frame.
[Enable] : The discrepancy is corrected automatically by skipping
time code numbers (DF: Drop frame).
[Disable] : The discrepancy is not corrected (NDF: Non-drop frame).
When the frame rate is set to 4 (23.976fps), 5 (25.00fps), or 7
(50.00fps), the drop frame function does not take effect. (If 4 is set or [53:
Video system] is set to [PAL], drop frame option will not be displayed.)
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During movie playback