Canon EOS R3 Advanced User's Manual page 511

3.
In the single-image display, press <
4.
Press < > to play back the movie.
The movie will start playing back. Sound is played through the speaker
(1).
You can pause playback and display the movie playback panel by
pressing <
Turn the <
>. Press it again to resume the playback.
> dial to adjust the volume (even during playback).
511
>.