Application: Gnome Subtitles
What it is:
Gnome Subtitles is a subtitle editor for the GNOME desktop. It
supports the most common text-based subtitle formats and allows for
subtitle editing, conversion and synchronization.
Gnome Subtitles supports popular subtitle formats, such as SubStation
Alpha (and also Advanced SubStation Alpha), SubRip and MicroDVD.
To know more about:
sudo apt-get install gnome-subtitles