Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 321)

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3 Setting the Movie Recording Quality
Movie Shooting Time Limit
When shooting movies other than High Frame Rate movies
The maximum recording time of one movie clip is 29 min. 59 sec. If
the movie shooting time reaches 29 min. 59 sec., the movie shooting
will stop automatically. You can start shooting a movie again by
pressing the <
0 > button. (The movie will be recorded as a new
movie file.)
When shooting High Frame Rate movies
The maximum recording time of one movie clip is 7 min. 29 sec. If
the movie shooting time reaches 7 min. 29 sec., the movie shooting
will stop automatically. You can start shooting a movie at a high
frame rate again by pressing the <
0 > button. (The movie will be
recorded as a new movie file.)
When downloading movie files exceeding 4 GB to a computer, use either
the EOS Utility (p.550) or a card reader (p.551). If you connect the
camera to a computer and download images with the computer’s OS,
movie files exceeding 4 GB cannot be downloaded.
Deleting any of the movie files created when a movie shot at one time
exceeds 4GB will make it impossible for EOS MOVIE Utility (p.553) to
play back the movie files consecutively or to merge and save them as a
single movie file.
Using EOS MOVIE Utility, you can automatically merge multiple MOV
format movies files split when exceeding 4 GB and save them as a single
movie file.