[ excerpt from developer's site ] matroska is a project aiming to become the standard of Multimedia Container Formats one day. It was derived from a similar project called MCF, but differentiates from that significantly because it is based on EBML (Extensible Binary Meta Language ), a kind of binary version of XML. This way the development team gains significant advantages in terms of future format extensability, without breaking file support in old parsers. Advanced because it is based on EBML, a kind of XML equivalent, that allow infinite extensibility of the format. And full featured because it includes precise seeking, any audio/video/subtitle codec support including VCM/ACM/DirectShow compatibility, timecode based format, complex frame dependencies, chaptering, internationalisation, error protection, tagging, file attachement, control track (to be defined), menu (to be defined), etc. All these features are not yet implemented but already defined in the format.