Error message "Mpeg-4 AAC decoder not installed" when playing video on Ubuntu 18.04.3 in VirtualBox byAuthor •October 12, 2023 The error message "Mpeg-4 AAC decoder not installed" typically indicates that your media player does not have the necessary codec to decode the audio in the video file. You can resolve this issue on Ubuntu 18.04 in VirtualBox by installing …