Avidemux fará isso e muito, muito mais.
código-fonte aberto e plataforma cruzada
Avidemux is a free open-source program designed for multi-purpose video editing and processing. Downloads, documentation, and other features can be found at avidemux.org. It is written in C/C++, using the GTK+ graphics toolkit, and therefore is truly a platform independent, universal video processing program. It is available for almost all distributions of Linux that are capable of compiling C/C++, GTK+ and the SpiderMonkey ECMAScript scripting engine. A Win32 version of this program is also available for Windows users, as well as Mac OS X, FreeBSD, NetBSD, and OpenBSD ports and packages. The program can be run in 64bit operating systems that are non-Windows and non-Macintosh based.
Informações sobre Input Formatos e Formatos de saída