I am using PI4 with raspbian buster. While I am playing videos on VLC the screen sometimes blink. The blinking interval is random. Is it normal or is there a problem that is needed to be fixed?
I also use VLC on the latest Buster and RPi4. I remember getting some screen blinking when I used a crappy HDMI cable which I have since replaced. One easy test you can do is changing the screen resolution to a lower one, e.g. 1280x720. You can do this e.g. by editing
raspi-config (those two require a reboot), by going to Application Menu > Preferences, or using command line by running
sudo tvservice -e "CEA 4". If the blinking goes away or is substantially reduced, your problem is likely in the cable, and you should get a shorter one if possible, and from a shop those quality you trust.
Sometimes, Screen flickering is attributed due to low power supply. Please check at the top right of your screen you will see a yellow thunder icon if that is the case.