What is a MK3D file?
Matroska 3D video container format
The Matroksta 3D (MK3D) file format is used for storing 3D content (video and audio) while using the standard MKV container. However, it also uses a StereoMode field for 3D video files which have a variety of configurations such as side by side (left eye is first) or top-bottom (right eye is first). The Matroska file format is seeking to be the future of 3D audio and video file formats. It was derived from a project called MCF, but MK3D files differentiate themselves from it significantly because it is based on EBML (Extensible Binary Meta Language), a binary derivative of XML. EBML enables the Matroska Development Team to gain significant advantages in terms of future format extensibility, without breaking file support from old media parsers.