Vorbis is a free and open-source software project headed by the Xiph.Org Foundation (formerly Xiphophorus company). The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in conjunction with the Ogv container format and it is therefore often referred to as Ogv Vorbis. The Ogv container format can multiplex a number of independent streams for audio, video, text (such as subtitles), and metadata. In the Ogv multimedia framework, Theora provides a lossy video layer. The audio layer is most commonly provided by the music-oriented Vorbis format but other codec options include the compression codec Opus, the lossless audio compression codec FLAC, and OgvPCM.
The Matroska Multimedia Container is an open standard free container format, a file format that can hold an unlimited number of video, audio, picture, or subtitle tracks in one file. It is intended to serve as a universal format for storing common multimedia content, like movies or TV shows. Matroska is similar in concept to other containers like AVI, MP4, or Advanced Systems Format (ASF), but is entirely open in specification, with implementations consisting mostly of open source software. Matroska file extensions are .MKV for video (with subtitles and audio), .MK3D for stereoscopic video, .MKA for audio-only files, and .MKS for subtitles only.