| Filename extension | .ogg, .ogv, .oga, .ogx, .ogm, .spx, .opus |
|---|---|
| Internet media type | video/ogg, audio/ogg, application/ogg |
| Magic number | OggS |
| Developed by | Xiph.Org Foundation |
| Initial release | May 2003; 21 years ago (2003-05) |
| Type of format | Container format |
| Container for | Vorbis,Theora,Speex,Opus,FLAC,Dirac, and others. |
| Open format? | Yes |
| Free format? | Yes[1] |
 | |
| Developer(s) | Xiph.Org Foundation |
|---|---|
| Initial release | 22 September 2004; 20 years ago (2004-09-22) |
| Stable release | 1.3.5 / 4 June 2021; 3 years ago (2021-06-04) |
| Type | Reference implementation (multiplexer/demultiplexer) |
| License | BSD-style license[2] |
| Website | downloads |
Ogg is afree,opencontainer format maintained by theXiph.Org Foundation. The authors of the Ogg format state that it is unrestricted bysoftware patents[3] and is designed to provide for efficientstreaming and manipulation of high-qualitydigital multimedia. Its name is derived from "ogging",jargon from the computer gameNetrek.[4]
The Ogg container format canmultiplex a number of independentstreams foraudio,video, text (such assubtitles), andmetadata.
In the Ogg multimedia framework,Theora provides alossy video layer. Theaudio layer is most commonly provided by the music-orientedVorbisformat or its successorOpus.Lossless audio compression formats includeFLAC, andOggPCM.
Before 2007, the .oggfilename 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.[5]
As of November 7, 2017, the current version of the Xiph.Org Foundation's reference implementation is libogg 1.3.3.[6] Another version, libogg2, has been in development, but is awaiting a rewrite as of 2018.[7] Bothsoftware libraries arefree software, released under theNew BSD License. Ogg reference implementation was separated from Vorbis on September 2, 2000.[8]
Ogg's variouscodecs have been incorporated into a number of different free andproprietarymedia players, both commercial and non-commercial, as well asportable media players andGPS receivers from different manufacturers.
TheOgg Vorbis project started in 1993. It was originally named "Squish" but that name was already trademarked, so the project underwent a name change. The new name, "OggSquish", was used until 2001 when it was changed again to "Ogg". Ogg has since come to refer to thecontainer format, which is now part of the larger Xiph.org multimedia project. Today, "Squish" (now known as "Vorbis") refers to a particularaudio coding format typically used with the Ogg container format.
Ogg is derived from "ogging",jargon from the computer gameNetrek, which came to mean doing something forcefully, possibly without consideration of the drain on future resources.[4][failed verification] At its inception, the Ogg project was thought by the authors to be somewhat ambitious given the limited power of thePC hardware of the time. Although the name Ogg is unrelated to the characterNanny Ogg inTerry Pratchett'sDiscworld novels, "Vorbis" is named after another Terry Pratchett character from the bookSmall Gods.[9]
The "Ogg"bitstream format, designed principally by the Xiph.Org Foundation, has been developed as the framework of a larger initiative aimed at producing a set of components for the coding and decoding of multimedia files, which are available free of charge and freely re-implementable in software and hardware.
The format consists of chunks of data each called an "Ogg page". Each page begins with the characters "OggS" to identify the file as Ogg format.
A "serial number" and "page number" in the page header identifies each page as part of a series of pages making up abitstream. Multiple bitstreams may bemultiplexed in the file where pages from each bitstream are ordered by the seek time of the contained data. Bitstreams may also be appended to existing files, a process known as "chaining", to cause the bitstreams to be decoded in sequence.
ABSD-licensed library, called "libvorbis", is available to encode and decode data from "Vorbis" streams. Independent Ogg implementations are used in several projects such asRealPlayer and a set ofDirectShow filters.[10]
Mogg, the "Multi-Track-Single-Logical-Stream Ogg-Vorbis", is the multi-channel or multi-track Ogg file format.
The following is the field layout of an Ogg page header:
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| Bit | Value | Flag | Page type |
|---|---|---|---|
| 0 | 0x01 | Continuation | The first packet on this page is a continuation of the previous packet in the logical bitstream. |
| 1 | 0x02 | BOS | Beginning Of Stream. This page is the first page in the logical bitstream. The BOS flag must be set on the first page of every logical bitstream, and must not be set on any other page. |
| 2 | 0x04 | EOS | End Of Stream. This page is the last page in the logical bitstream. The EOS flag must be set on the final page of every logical bitstream, and must not be set on any other page. |
The segments provide a way to group segments into packets, which are meaningful units of data for the decoder. When the segment's length is indicated to be 255, this indicates that the following segment is to be concatenated to this one and is part of the same packet. When the segment's length is 0–254, this indicates that this segment is the final segment in this packet. Where a packet's length is a multiple of 255, the final segment is length 0.
Where the final packet continues on the next page, the final segment value is 255, and the continuation flag is set on the following page to indicate that the start of the new page is a continuation of last page.
VorbisComment is a base-level Metadata format initially authored for use with Ogg Vorbis. It has since been adopted in the specifications of Ogg encapsulations for other Xiph.Org codecs includingTheora,Speex,FLAC andOpus.VorbisComment is the simplest and most widely supported mechanism for storing metadata with Xiph.Org codecs.[11]
Notably,[attribution needed] one or moreMETADATA_BLOCK_PICTURE=... in aVorbisComment for thumbnails and cover art haveBase64-encoded values of the correspondingFLACMETADATA_BLOCK_PICTURE. In other words, FLAC stores thumbnails and cover art in binary blocks—outside of the FLAC tags in alittle-endianMETADATA_BLOCK_VORBIS_COMMENT.[12][13]
Other existing and proposed mechanisms are:[14]
The Ogg project began with a simple audio compression package as part of a larger project in 1993.[9] The software was originally namedSquish but due to an existing trade mark it was renamed toOggSquish. This name was later used for the whole Ogg project. In 1997, the Xiphophorus OggSquish was described as "an attempt both to create a flexible compressed audio format for modern audio applications as well as to provide the first audio format that is common on any and every modern computer platform".[16] The OggSquish was in 2000 referred to as "a group of several related multimedia and signal processing projects". In 2000, two projects were in active development for planned release: Ogg Vorbis format and libvorbis—the reference implementation of Vorbis. Research also included work on future video and lossless audio coding.[9][17][18][19][20] In 2001, OggSquish was renamed toOgg and it was described as "the umbrella for a group of several related multimedia and signal processing projects".[21] Ogg has come to stand for thefile format, as part of the larger Xiph.org multimedia project. Squish became just the name of one of the Ogg codecs.[9] In 2009, Ogg is described as "a multimedia container format, and the native file and stream format for the Xiph.org multimedia codecs".[22]
The Ogg reference implementation was separated from Vorbis on September 2, 2000.[8]
In May 2003, two InternetRFCs were published relating to the format. The Ogg bitstream was defined in RFC 3533 (which is classified as 'informative') and itsInternet content type (application/ogg) inRFC 3534 (which is, as of 2006[update], a proposed standard protocol). In September 2008, RFC 3534 was obsoleted byRFC 5334, which added content typesvideo/ogg,audio/ogg and filename extensions .ogx, .ogv, .oga, .spx.
In 2002, the lack of formal video support in Ogg resulted in the development of theOGM file format, a hack on Ogg that allowed embedding of video from the MicrosoftDirectShow framework into an Ogg-based wrapper. OGM was initially supported only by closed source Windows-only tools, but the codebase was subsequently opened. Later, video (and subtitle) support were formally specified for Ogg but in a manner incompatible with OGM. Independently, theMatroska container format reached maturity and provided an alternative for people interested in combining Vorbis audio and arbitrary video codecs. As a result, OGM is no longer supported or developed and is formally discouraged by Xiph.org.[23] Today, video in Ogg is found with the .ogv file extension, which is formally specified and officially supported. Software and codecs that support .ogm files are available without charge.[24]
Although Ogg had not reached anywhere near the ubiquity of theMPEG standards[25] (e.g.,MP3/MP4), as of 2006[update], it was commonly used to encodefree content (such as free music, multimedia onWikimedia Foundation projects andCreative Commons files) and had started to be supported by a significant minority ofdigital audio players. Also supporting the Ogg format were many popular video game engines, includingDoom 3,Unreal Tournament 2004,Halo: Combat Evolved,Jets'n'Guns,Mafia: The City of Lost Heaven,Myst IV: Revelation,StepMania,Serious Sam: The Second Encounter,Lineage 2,Vendetta Online,Battlefield 2, and theGrand Theft Auto engines, as well as the audio files of theJava-based game,Minecraft. The more popular Vorbis codec had built-in support on many software players, and extensions were available for nearly all the rest.
On May 16, 2007, theFree Software Foundation started a campaign to increase the use of Vorbis "as an ethically, legally and technically superior audio alternative to the proprietary MP3 format".[26] People were also encouraged to support the campaign by adding a web button to theirwebsite orblog. For those who did not want to download and use the FSF's suggested Ogg player (VLC), theXiph.Org Foundation had an official codec[27] forQuickTime-based applications inWindows andMac OS X, such asiTunes players andiMovie applications; and Windows users could install aWindows Media Player Ogg codec.[28]
By June 30, 2009, the Ogg container, through the use of the Theora and Vorbis, was the only container format included inFirefox 3.5 web browser's implementation of theHTML5<video> and<audio> elements.[29][30] This was in accordance with the original recommendation outlined in, but later removed from, the HTML5 draft specification (seeOgg controversy).
On March 3, 2010, a technical analysis by anFFmpeg developer was critical about the general purpose abilities of Ogg as a multimedia container format.[31] The author of Ogg later responded to these claims in an article of his own.[32]
Ogg is only a container format. The actual audio or video encoded by a codec is stored inside an Ogg container. Ogg containers may contain streams encoded with multiple codecs; for example, a video file with sound contains data encoded by both an audio codec and a video codec.
Being a container format, Ogg can embed audio and video in various formats[33][34] (such asDirac,MNG,CELT,MPEG-4,MP3 and others) but Ogg was intended to be, and usually is, used with the followingXiph.org free codecs:
Ogg audio media is registered asIANAmedia typeaudio/ogg with file extensions.oga,.ogg, and.spx. It is a proper subset of the Ogg video media typevideo/ogg with file extension.ogv. Other Ogg applications use media typeapplication/ogg with file extension.ogx; this is a superset ofvideo/ogg.[34] TheOpus media typeaudio/opus with file extension.opus was registered later inRFC7587 and7845.
3.3 Ogging: This is the art of killing a carrier, or potential carrier, by a suicide run.
This library was never released and now looks like it needs to be redesigned.
