Vorbis

Ogg Vorbis is a completely free and open audio compression (codec) project from the Xiph.org Foundation, and is part of their Ogg effort to create free and open multimedia and signal processing standards. Like all developments of the Ogg project, Vorbis is believed to be completely free of the licensing or patent issues raised by other proprietary formats such as MP3.

Compared to other audio formats Ogg Vorbis is a relatively new phenomenon, having been continually refined by developers until a stable version 1.0 of the codec was released on July 19, 2002. As such, it has yet to push out MP3 as the popular format for laypeople. There is no reason to assume it won't, however, given its higher fidelity and completely free nature. MP3 has a popular history dating back to the mid-1990s and was the primary lossy audio format so it may be some time before one sees more Ogg format files than MP3 files. In the commercial sector, Ogg Vorbis has already replaced MP3 as the de facto standard audio codec, with most newer video game titles employing Ogg Vorbis as opposed to MP3.

Table of contents 1 Technical Details 2 Hardware and Software Support 3 See also 4 External links

Technical Details

Given 44.1 kHz (standard CD audio sample frequency) stereo input, the current encoder will produce output from 64 to 400 kbps, depending upon the specified quality setting. While Vorbis 1.0 is tuned for bitrates of 16-128 kbps/channel, there's nothing saying you can't encode at 512 kbps or 8 kbps. These numbers are only approximate, however, as Vorbis is inherently variable bitrate (VBR). Vorbis currently produces better audio quality and smaller file sizes than other formats under comparable circumstances.

The specifications are placed in the public domain, the libraries are released under a BSD-style license, and the tools are released under the GPL (GNU General Public License).

Vorbis uses the modified discrete cosine transform (MDCT) for converting the sound data from time domain to frequency domain and back.

Hardware and Software Support

A fixed-point implementation of the Ogg Vorbis decoder, called Tremor, also under a BSD-style license, was released on September 2, 2002, in hopes that manufacturers of hardware audio players would support the format in upcoming versions and models of their devices. iRiver America, manufacturer of the popular iRiver MP3/WMA player, is reportedly in the testing stage of releasing a Vorbis-compatible firmware version.

RealNetworks has announced that they will support Ogg Vorbis in their products. See Helix project for more details.

Ogg Vorbis can be played using these (and other) players:

• XMMS (for UNIX-style systems, GPL [formerly known as X11amp])
• zinf (for Linux and Windows, GPL [formerly known as FreeAmp])
• Winamp (for Windows, freeware but not free software)
• JOrbis[?] (pure Java, LGPL)
• foobar2000[?] (for Windows, freeware, focused on high quality playback)

The BBC has recently experimented with putting out Vorbis-encoded audio streams. The technical experiments are now complete, and the BBC is considering whether to deploy the technology.

Unlike the name "Ogg", "Vorbis" is named after a Terry Pratchett character, High Priest Vorbis in Small Gods.

See also

• Ogg bitstream format
• Speex, speech codec
• FLAC, high fidelity audio codec
• Theora, video codec

External links

• The Xiph.org Foundation's site (http://www.xiph.org/)
• The Ogg Vorbis site (http://www.vorbis.com/)
  • Listening test of Vorbis vs. MP3, RealAudio, WMA, etc. (http://www.xiph.org/ogg/vorbis/listen)
  • Vorbis FAQ (http://www.vorbis.com/faq.psp)
  • Vorbis Documentation (http://www.xiph.org/ogg/vorbis/docs)
• Xiph's Wiki entry for Vorbis, including portable player support info. (http://wiki.xiph.org/Vorbis)
• BBC Vorbis testing page (http://support.bbc.co.uk/oggstreams.shtml)
• RealNetworks press release regarding Vorbis support (http://www.realnetworks.com/company/press/releases/2002/xiph)
• foobar2000 player (http://foobar2000.hydrogenaudio.org)
• Description of the modified discrete cosine transform (http://www.free-comp-shop.com/vorbis)