How to play MP3, AAC, MKV, MP4, AVI, FLV etc on Ubuntu 21.04 (Hirsute Hippo) Install Multimedia Codecs
If you to play multimedia file like MP3, AAC, MKV, MP4, AVI, FLV, you will get a warning H.264/MPEG-4 AAC decoder is required to play the file, but are not installed or a similar warning like that
to solve it is very easy, you just need to install the codecs
how to open a terminal and run the following command
sudo apt install ubuntu-restricted-extras
if you see a warning like this press tab and enter
now try to open the multimedia file you want