e.g. avidemux
see https://debian.pkgs.org/9/multimedia-main-i386/avidemux-cli_2.6.20-dmo3+deb9u1_i386.deb.html

Install Howto
=============
Add the following line to /etc/apt/sources.list:
 deb http://www.deb-multimedia.org stretch main
Update the package index:
 # sudo apt-get update
Install GPG key of the repository:
 # sudo apt-get install deb-multimedia-keyring
Install avidemux-cli deb package:
 # sudo apt-get install avidemux-cli