First
Let's check if you have Nvidia drivers installed
Install:
$ sudo apt install software-properties-gtk software-properties-common
Open:
$ software-properties-gtk
Choose the tab Additional Drivers
Wait for the loading list, and then you should see the installed drivers.

If you don't see any NVIDIA proprietary driver in the list, you need to install them
If you see them, just choose it and then reboot to start clean
To install the driver
Use the command:
$ sudo ubuntu-drivers list
You should get something like this (probably different version numbers):
nvidia-304
nvidia-340
intel-microcode
nvidia-367
Install nvidia-367
(or the version you want/need, and could be different)
$ sudo apt install nvidia-367 nvidia-settings
Then and again you have to choose the driver
Open:
$ software-properties-gtk
Choose the tab Additional Drivers
Wait for the loading list, and then you should see the installed drivers.

Just choose the driver in the list and then reboot to start clean
ref: https://gist.github.com/Jiab77/d3344422ee6d334f284425b558dc572c
Now, after reboot, open $ nvidia-settings
Look after an entry named PRIME Profiles
, select it and then choose the NVIDIA GPU

Reboot again
Now try open a video
Use mpv
(If you don't have it install it with sudo apt install mpv
)
Play the video with the command:
mpv -v filename.mp4
(or mkv,avi, etc)
In case the error continues, just copy and paste the text in the terminal. It will be a lot because of the -v
flag.
Additional Info
You can also check and change PRIME using a command
Install:
$ sudo apt install nvidia-prime
To check
$ sudo prime-select query
To select Intel GPU as PRIME
$ sudo prime-select intel
To select NVIDIA GPU as PRIME
$ sudo prime-select nvidia
ref: https://www.linuxbabe.com/desktop-linux/switch-intel-nvidia-graphics-card-ubuntu
Also for future reference in case the answer doesn't work
Run
sudo lshw -sanitize -class system,processor,display,multimedia
copy the output and paste it here editing your own post