Ogg

Ogg is a free, open container format maintained by the Xiph.Org Foundation. The creators of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high quality digital multimedia.

"Ogg" is derived from "ogging", jargon from the computer game Netrek:

The Ogg container format can multiplex a number of independent streams for audio, video, text (such as subtitles), and metadata.

In the Ogg 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 OggPCM.

Before 2007, the .ogg filename extension was used for all files whose content used the Ogg container format. Since 2007, the Xiph.Org Foundation recommends that .ogg only be used for Ogg Vorbis audio files. The Xiph.Org Foundation decided to create a new set of file extensions and media types to describe different types of content such as .oga for audio only files, .ogv for video with or without sound (including Theora), and .ogx for multiplexed Ogg.