Vorbis

Si you do not manage to read the files with the format Ogg present on Wikipédia, consult the page Aide: To listen to sounds ogg.

Vorbis is an algorithm of compression and decompression (codec) digital audio, without patent, open and free, more powerful in term of quality and compression ratio that the format MP3, but less popular than this last.

Promoted by the foundation Xiph.org, it is one of the components of their project Ogg, the purpose of which is to create a whole of open formats and codecs Multimédia (its, video), free of any patent.

Let us note that the sound format Vorbis must obligatorily be encapsulated. It is it in the majority of the cases by the format Ogg, from where the name of Ogg Vorbis. Nevertheless, Vorbis and Ogg are different (one being contents and the other the container, Matroska which can be used as alternate container). Ogg Vorbis is thus not a format, but a whole of formats.

Principle of operation

Like MP3, Ogg Vorbis is a format of audio Compression destroying or with losses, i.e. the decompressed compressed file then will not be identical bit for bit with the original. One can compare it with the format JPEG for the images, the more so as it uses similar techniques. Like all the formats of compression based on this principle, it is conceived so that the listener does not make the difference with listening with the original, by exploiting the characteristics of the acoustic Perception human, more particularly by removing the frequencies present least audible compared to the others.

The tools for coding exploited by the format are more advanced than those which the MP3 exploits, which pays its seniority here. That explains the higher performances of the format, in particular for the low flows, lower than 100 kilobits a second. It should however be noted that these more powerful algorithms induce a more important complexity of treatment, and thus a time of compression generally higher than the same file that one would compress in MP3 on a of the same machine power.

Starting from a stereophonic source sampled to 44,1 K Hz in 16 bit (standard sampling of a audio CD), the Vorbis coder produced of the files whose flow of exit varies between 30 and 500 kbit/s, according to the selected quality of coding and of the type of music. Vorbis is a format VBR ( Variable Bitrate , or variable flow). That enables him to allocate more information to compress difficult passages (generally, but not always, the passages difficult to code are the very polyphonic passages containing many acute frequencies, but that depends also much on the Musical genre), and to save place on less demanding passages (for example one starts piece where the beater gives the Tempo, or ideally a numerical Silence). Thus, it is sound quality which is constant (in theory) and not the Débit of data, which seems desirable in all the cases, except in certain cases of Streaming on Internet which can have requirements for regularity of the flow.

Technical details

Starting from a sampled stereo audio stream with 44,1 Khz (standard sampling of a CD audio), the coder produces at exit a flow with a flow from 45 to 500 Kbit/s according to selected quality (cf table). The coefficient of quality is metric arbitrary and can vary from -1 to 10 (- 2 to 10 for AoTuV).

The files coded with quality 5 (- q5), for example, should have same sound quality whatever the version of the coder, but the new versions must be able to reach this quality with a lower Binary debit. The binary debits provided in the table are it as an indication, Vorbis having intrinsically a variable binary debit, this last can thus change considerably from one sample to another.

Copyrights and patents

As all the remainder of the project Ogg, Vorbis is announced as being completely free of the problems of Brevet S or licenses owners. Indeed, all publication of a process not patented as a preliminary is equivalent legally to a setting in the public domain (because one can patent only one process not having never published before).

The specifications of the project are placed in the public domain; the libraries are diffused under a license of the type BSD, and the utilities (which include/understand, inter alia, the coder oggenc and the reader in line of order ogg123 ) are diffused under license LPG.

However, this irrefutable fact was not proven yet, from complexity and/or the costs which an exhaustive search for patents would imply, former to the format and to which the algorithms used would cover. Suspicions would plane on the alleged freedom of the format, in particular since the possible use of patented techniques was proposed.

Diffusion of the format

Ogg Vorbis is relatively recent, version 1.0 being available since the July 19th 2002. Its popularity is consequently less than that of the MP3. From its exit, the format knows an increasing diffusion however. This popularity constitutes a market, which from now on editors and industrialists exploit. Thus popular software such Winamp or Nero supports the format in a native way. The industry of the video game uses also more and more Vorbis for the sound compression of its productions, the quality ratio/compression being definitely higher than that of the mp3, it also makes it possible to save the price of a license of use of a format owner.

During the year 2004 also appeared several compatible walkmans Vorbis, in particular of Cowon and Samsung.

The distributions GNU/Linux Fedora and Ubuntu chose format OGG instead of the MP3, subjected to the patent.

Software readers

The company RealNetworks announced that it would deal with Ogg Vorbis in its product range. See the project Helix player for further details.

Ogg Vorbis can be read by the following utilities, inter alia:

Amarok, audio reader functioning on GNU/Linux, and more specifically envisaged for KDE.
Audacious, for the systems Linux/Unix
Foobar2000 (for Windows, Graticiel)
Audio Jet of Cowon. Graticiel for Windows
J-Ogg (program 100% Java)
JOrbis (program 100% Java, LGPL)
MPlayer (for GNU/Linux, Windows, and Mac OS X, LPG), in line of order: http://www.mplayerhq.hu/
Rhythmbox, audio reader functioning on GNU/Linux, and more specifically envisaged for GNOME
Songbird, an audio reader free and based on architecture XUL of Mozilla.
Streamplug, audio/video reader integrable in a page Internet (plugin)
VideoLAN Customer (VLC) (for Windows, Mac OS X, GNU/Linux, and others UNIX, LPG)
Whamb (for Mac OS X, Graticiel)
Winamp (for Windows, Graticiel)
Windows Media Player thanks to the Codecs DirectShow. See.
XMMS (for the systems of the type UNIX, LPG X11amp)
Zinf (under GNU/Linux and Windows, LPG FreeAmp)

Material readers

Another important aspect concerning the diffusion of the format Ogg Vorbis is its recognition by the manufacturers of digital music players (" MP3" readers;) portables. The VorbisHardware page of Wiki xiph.org wiki an up to date list of the readers contains supporting Vorbis such as portable readers, of PDAs, and microchips. Several models of Samsung, IRiver, Rio, or Cowon, mainly of the top-of-the-range models, can read the files in Ogg Vorbis, although with sometimes some restrictions of frequencies. However, the reader more spread, the IPod of Apple, Inc. does not propose this functionality and Apple, Inc. did not declare anything on this subject. It would seem however that the last versions of ITunes have a function of reading of files Ogg Vorbis, function decontaminated by Apple. It is however possible to circumvent this problem by the installation of a firmware (IPodLinux or Rockbox) on its reader iPod.

Radio France started to diffuse its stations in Ogg Vorbis (following many criticisms of users occurred in December 2002, when Radio France chose to stop its diffusion in RealAudio to use in the place the audio format owner of Microsoft, Windows Media Audio). For still unknown reasons, without explanations, Radio France seems to have ceased this diffusion during the summer 2006.

Ogg Tremor

A placement of the decoder Ogg Vorbis called Ogg Tremor , using calculations into arithmetic whole (requiring less resources Processor), it also diffused under a license of the type BSD, is available since the September 2nd 2002. The purpose of this application is to motivate the manufacturers of audio material (wandering…) to deal with the format in the new versions and models of their products. The manufacturers iRiver America (manufacturer of the popular walkman MP3/WMA) and ISM (French manufacturer), provide for some their products of the updates of the firmware , making them compatible with the Vorbis format.

Etymology

The name Vorbis comes from a character of Terry Pratchett, the Vorbis deacon, in the Small Gods . The name Ogg also comes from a character of the same author, the witch Nounou Ogg, present in various novels of the series of the Disc-World.

Notes and references of the article

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