Canon EOS-1 DX Mark III Advanced User's Manual page 306

For longer HDMI output
To continue HDMI output for longer than 30 min., select [
off] to [Disable] (
Caution
HDMI output without information prevents display of warnings about the card
space, battery level, or high internal temperature (
During HDMI output, display of the next image may take some time if you switch
between movies of different recording qualities or frame rates.
Avoid operating the camera when recording movies to external devices, which may
cause information to be displayed in the HDMI video output.
Brightness and color of movies recorded with the camera may look different from
that of HDMI video output recorded by external devices, depending on the viewing
environment.
Note
By pressing <
Time codes can be added to HDMI video output (
Audio is also output via HDMI, except when [Sound rec.] is set to [Disable].
).
> the button, you can change the information displayed.
+
) via HDMI.
).
306
], then set [ : Auto power