Right now there are handful of multimedia converters available for Linux. It is an free and open-source application that converts to plenty of formats using FFMpeg and avconv. It is written using Python programming language and GTK3 for GUI. Currently has ability to convert more than 100 different formats.
Curlew multimedia converter is around from quite sometime and known to have some extra features such as: ability to show file information(duration, progress, approx size, duration etc.), preview file before conversion, convert part of specified file, attach subtitles to videos, show errors in details if occurs, allow to skip files or remove during conversion process, and fairly simple user interface. It is available for all currently supported Ubuntu 18.04/16.04/14.04/Linux Mint 19/18/17 and other Ubuntu based distributions.
Curlew multimedia converter is around from quite sometime and known to have some extra features such as: ability to show file information(duration, progress, approx size, duration etc.), preview file before conversion, convert part of specified file, attach subtitles to videos, show errors in details if occurs, allow to skip files or remove during conversion process, and fairly simple user interface. It is available for all currently supported Ubuntu 18.04/16.04/14.04/Linux Mint 19/18/17 and other Ubuntu based distributions.