Install winff-doc by entering the following commands in the terminal:
sudo apt update sudo apt install winff-doc
Description:
winff documentation
WinFF is a graphical user interface for FFmpeg or avconv. It will convert almost any video file that FFmpeg or avconv will convert. WinFF does multiple files in multiple formats at one time. You can, for example, convert mpeg's, flv's, and mov's into avi's (or DVD/VCD format or MPEG or 3gp etc.) all at once. . This package contains the pdf-manuals for winff in several languages.
Homepage: http://www.winff.org/
Version: 1.5.5-4
Section: universe/doc