Convierte MK3D a subtítulos opcionales

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.