MKVToolNix is a small collection of tools (mkvmerge, mkvinfo,
mkvextract, mkvpropedit and mmg) that allows you to manipulate Matroska
(MKV) files in several ways. You can use MKVToolNix to create, split,
edit, mux, demux, merge, extract or inspect Matroska files. The program
will also work with other video formats (AVI, MPEG, MP4, MPEG, Ogg/OGM,
RealVideo, MPEG1/2, h264/AVC, Dirac, VC1) including some video codecs
(such as VP9 video codec support - reading from IVF/Matroska/WebM files,
extract to IVF files), audio (AAC, FLAC, MP2, MP3, (E)AC3, DTS/DTS-HD,
Vorbis, RealAudio) and also most subtitle formats (SRT, PGS/SUP, VobSub,
ASS, SSA etc.).
This is a cross platform application that will work on
Windows (both 32 and 64 bit versions), Mac OS X and Linux. Please note
that from this page you can download the Windows (installer and
portable) and Mac OS X versions.