MKVToolNix is a set of Open Source tools to create, alter and inspect Matroska media files under Linux, macOS and Windows. The package consists of:
• mkvmerge: used to create Matroska files from other container formats such as MP4, AVI, Ogg, QuickTime, MPEG program streams (VOB) or transport streams (M2TS). mkvmerge supports numerous audio, video and subtitle codecs including most recent ones (e.g. AVC, HEVC, AAC, DTS, Vorbis). It can split big files into multiple smaller ones and append multiple smaller ones into a single big one.
• mkvextract: the inverse of what mkvmerge does. It takes tracks from a Matroska file and writes them into other container formats (e.g. video tracks into AVI files).
• mkvinfo: outputs information about the structure and content of a Matroska file
• mkvpropedit: allows editing header and track-level properties (such as the file title, track languages etc.) of Matroska files without having to multiplex them again
• MKVToolNix GUI: a nice GUI that uses the other tools mentioned above under the hood to do the heavy lifting. It also includes a nice chapter editor.