Install ffmpeg2theora by entering the following commands in the terminal:
sudo apt update sudo apt install ffmpeg2theora
Description:
Theora video encoder using ffmpeg
This package provides a command-line tool to encode/recode various video formats (basically everything that ffmpeg can read) into Theora, the free video codec.
Homepage: http://v2v.cc/~j/ffmpeg2theora/
Version: 0.30-1build1
Section: universe/graphics