mkvtoolnix-gui software package provides Set of tools to work with Matroska files - GUI frontend, you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install mkvtoolnix-gui
mkvtoolnix-gui is installed in your system.
Make ensure the mkvtoolnix-gui package were installed using the commands given below,
$ sudo dpkg-query -l | grep mkvtoolnix-gui *
You will get with mkvtoolnix-gui package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | Graphics |
| Package | mkvtoolnix-gui |
| Version | 6.7.0-1 |
| Description | Set of tools to work with Matroska files - GUI frontend |
| Sub Section | Graphics |