MKVToolnix is a set of tools to create, alter and inspect Matroska
(and WebM) files. With these tools one can:

MKVToolnix requires wxGTK or wxPython.  It comes with internal versions 
of libembl and libmatroska, and it will use the internal versions if they
are not installed on the system.

Interested parties can build a QT GUI by passing QTGUI=yes to the script.