Canon EOS-1D X Mark III Advanced User's Manual page 277

Note
To display RAW movies on a computer, using Digital Photo Professional (EOS
software, hereafter DPP) is recommended.
Older versions of DPP Ver.4.x do not support display, processing, editing, or other
operations with RAW movies recorded by this camera. If a previous version of DPP
Ver.4.x is installed on your computer, obtain and install the latest version of DPP
from the Canon website to update it ( ). (The previous version will be overwritten.)
Similarly, DPP Ver.3.x or earlier does not support display, processing, editing, or
other operations with RAW movies recorded by this camera.
Commercially available software may not be able to display RAW movies recorded
by this camera. For compatibility information, contact the software manufacturer.
To prioritize gradation in highlights, set Canon Log to [On]. For RAW movies,
consider setting the color matrix to CINEMA EOS Original.
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