Vorbis

from Wikipedia, the free encyclopedia

Vorbis ( also known as Ogg Vorbis Listen ? / I in the corresponding container format ) is a (patent) free audio format for lossy audio data reduction . The format was developed by the Xiph.Org Foundation as a patent-free alternative to the widespread MP3 format. The format is said to be customizable enough to still be used in 2025. Audio file / audio sample

properties

Vorbis can be encoded with either a variable or a constant bit rate between (average) 32 and 448 kbit / s. The format is streaming and multi-channel capable . As a broadband process, Vorbis basically supports the mapping of the entire human hearing spectrum with sampling rates of 44.1 kHz and more. Hearing tests gave transparent results from 150 to 170 kbit / s (Vorbis quality level 5). Vorbis is on a similar level to Musepack or the proprietary Advanced Audio Coding .

technology

Vorbis is, like most of its kind, a transform codec based on the modified discrete cosine transform (MDCT). Vorbis data is usually in Ogg - Container files ( file extension .ogg) embedded, which are also developed by the Xiph.Org Foundation. Vorbis data can also be contained in Matroska , OGM or WebM containers (for example as an audio track for a video). The specially developed, comparatively flexible Vorbis comment scheme is used to record metadata .

Multi-channel sound

It supports up to 255 channels. The Vorbis I specification specifies the assignments depending on the number of channels.

Number of channels Occupancy
1 1 0 channels (mono) label.svg monophonic
2 2 0 channels (stereo) label.svg Stereo : left, right
3 3 0 channels (stereo front-center) label.svg1D surround : left, center, right
4th 4 0 channels (quadrophonic) (quadrophonie) label.svg Quadrophonic surround sound : front left, front right, rear left, rear right
5 5 0 channels (surround sound) label.svg 5-channel surround sound: front left, front center, front right, rear left, rear right
6th 5 1 channels (surround sound) label.svg 5.1 surround sound: front left, front center, front right, rear left, rear right, LFE channel (subwoofer)
7 or more 6 1 channels (extended surround sound) label.svg 7 1 channels (extended surround sound) label.png 7 2 channels (extended surround sound) label.svg application-specific, no specification

distribution

Vorbis has now established itself in the IT industry alongside MP3 and AAC . Audio files in Wikipedia and Wikimedia Commons are generally saved in this format. Support is mediocre among mobile music players. The internet radio stations that Vorbis use include Deutschlandradio , Bermuda radio , Radio Darmstadt , Radio Lora Munich , Freie Sender Kombinat and RadioTux . The music streaming service Spotify also uses the combination of Ogg-Vorbis in various average bit rates depending on the player.

software

Implementations

The reference implementations are published under a BSD-like license . In addition to these, separate further developments took place in a series of spin-offs, the most important of which were also improved in the official version.

aoTuV

Spectral analysis of a piece of music ( The Power of Thy Sword ) with two channels, each plotted against time. Comparison of the original with the results of the encoding in different lossy audio formats (including aoTuV). The original shows signals up to about 21 kHz, while after lossy coding the bandwidth is more or less reduced. However, this does not say much about the sound quality, as the lower frequencies are more important for the sound impression. If the circumcision is too severe, however, the highs may be audibly missing. ( MiniDisc frequency spectra from analog recording.)

aoTuV ( Aoyumi's Tuned Vorbis ) is a Vorbis encoder with the aim of further improving the sound quality. This is especially true for low bit rates (below 64 kb / s) - so far more of a weak point for Vorbis. The aoTuV code is based on the code from Xiph.Org and generates files that correspond to the Vorbis specifications. Since Vorbis v1.1, aoTuV Beta-2 has been an official part of the Vorbis encoder from Xiph.Org. With the Beta-3 version , 2 new quality levels (32 kb / s and 48 kb / s) were introduced in order to allow even stronger compression. The current version is Beta 6.03 (May 25, 2011) with further improved sound. The sound at higher bit rates has also been improved. In listening tests in which Vorbis is compared with other formats, the aoTuV encoder is often used, as it allows a better result to be expected.

Lancer

With the help of assembler, the Lancer project develops processor-specific versions of an encoder that are optimized for speed. Mainly through the use of the faster floating point instruction set extensions such as SSE that are present in many modern main processors , a doubling of the performance with the same quality is often achieved.

Playback software

Software for playing Vorbis audio data is available for all modern operating systems. It is included in most Linux distributions from the outset, and popular multimedia players under Windows such as AIMP , foobar2000 , Media Player Classic - Home Cinema , MPlayer , VLC media player or Winamp also come with Vorbis support. Since the Vorbis decoder Tremor , which places much lower demands on processors, is available in a similar way to the original Vorbis implementation, there is also software for some portable media players.

Hardware support

Vorbis itself is not supported on all hardware because the original implementation requires a floating point unit , which is seldom available, especially on portable devices. The integer Vorbis decoder Tremor performs the decoding without using a floating point unit.

Compared to MP3 and AAC, Vorbis decoding is computationally simpler, but it requires more memory, as there is no static probability model and Huffman tables and data for the vector quantizer are supplied in the data stream itself. This data is only a few kilobytes in compressed form, but must be decompressed and stored in memory.

Some hardware manufacturers now support the Vorbis format as standard (e.g. Blackberry , Cowon , iriver , Samsung , TrekStor or SanDisk Sansa), others only after a firmware update. For some hardware, such as B. Apple's iPod has alternative third-party firmware that Vorbis supports. The " Rockbox " project provides firmware with a Vorbis decoder that is under GPL. There are various homebrew programs for the PlayStation Portable and the Nintendo DS that also offer Vorbis support, but require modified firmware.

In the meantime, Vorbis support is also implemented directly in the hardware of signal processors, parallel to MP3 decoding, so that more and more players should be able to use the alternative format in the future.

All devices running the Android operating system support Vorbis.

Comparison with MP3 and AAC

  • One of the main differences are the different licenses: While the AAC technology is patented and licenses must be purchased for use, MP3 and Vorbis are completely free.
  • Unlike Vorbis, MP3 and AAC are standardized by the ISO .
  • Technically speaking, Vorbis and AAC compress more efficiently than MP3 (which is also much older) and the sound quality can still be used for voice recordings with a very strong compression (40 kbit / s).
  • As is now the case with MP3 , the Vorbis specifications do not define any fixed bit rates ( CBR ). However, these are supported by many codecs and also by the reference implementation.
  • Vorbis natively supports uninterrupted playback and replay gain . With MP3, this is only possible through non-standardized extensions that are only supported by a few codecs and players.
  • While MP3 supports a maximum of two channels (stereo) without extensions, Vorbis can use up to 255 channels in a flexible arrangement.
  • The Vorbis format is less common than the MP3 format. Much less portable playback devices (" MP3 players ") can play Vorbis, but more and more playback devices are coming onto the market that support this format.
  • Analogous to the ID3 tags for storing metadata in MP3 or AAC files, Vorbis offers the much more flexible Vorbis comments .

history

In autumn 1998 the Fraunhofer-Gesellschaft informed various audio codec developers that the distribution or sale of MP3 audio codec software was protected by license and that a license fee had to be paid for it. This announcement mainly affected many free software projects, most of which stopped their development (see also LAME ).

Christopher Montgomery then began to develop the free audio codec Vorbis , which is not subject to licenses or patents . The name "Vorbis" comes from the character "Exquisitor Vorbis" from Terry Pratchett's Discworld novel Simply divine .

The project went public for the first time in April 2000 and presented the audio codec , which was then still subject to the LGPL . In March 2001, the codec's license was changed to a BSD-like license to make the codec easier to use on commercial products.

Version 1.0 was published in July 2002. This made the first version of Vorbis available to end users. Shortly afterwards, Real Networks announced that it would support Vorbis in their Helix project . In September 2002, the previously not freely available decoder Tremor , which is tailored for use on special hardware, was also offered free of charge under a BSD-like license.

In 2003, hardware manufacturers began shipping portable music devices with Vorbis support. For example, iriver published a firmware update for the iHP-100 in October and released the successor with the appropriate firmware.

In August 2004, Real Networks followed a promise to support Vorbis in the Helix project and released versions of the Helix and RealPlayer that Vorbis could play.

Version 1.1.0 of the codec was published in September 2004.

In 2005 Microsoft released a license for the then new DRM system Janus , in which hardware manufacturers were prohibited from supporting alternative audio formats such as Vorbis. However, this condition was contradicted in October 2005 by judge Colleen Kollar-Kotelly.

In 2005, as part of the Ghost project, Xiph.Org worked for the first time on plans and drafts for a Vorbis successor (initially in conversation as Vorbis II). In addition to the codec plans of Christopher Montgomery, which are on hold in favor of the further development of Theora, this also resulted in the particularly low-latency real-time codec CELT by Jean-Marc Valin .

See also

Web links

Commons : Vorbis  - collection of images, videos and audio files

Individual evidence

  1. ↑ people.xiph.org
  2. ↑ web.mit.edu (PDF)
  3. ↑ wiki.hydrogenaudio.org
  4. ↑ older detailed comparative hearing test from August 2005 for bit rates of around 180 kbps (English)
  5. ↑ wiki.xiph.org
  6. ↑ Help: Audio
  7. ↑ Deutschlandradio on the Internet with OGG Vorbis Stream ( Memento of the original from August 30, 2009 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.dradio.de
  8. ↑ Free broadcaster Kombinat on the Internet with OGG Vorbis Stream
  9. ↑ What quality does Spotify offer for streaming? on support.spotify.com/de
  10. ↑ Help: Audio # Ogg-Vorbis-Player
  11. ↑ Android Developer - Supported Media Formats
  12. ↑ Ralph Giles: Vorbis and Wikipedia on a blog in response to a Wikipedia-related query, December 29, 2005.
  13. ^ Peter Nonhoff-Arps: New competition for MP3 on Heise online , April 13, 2000.
  14. ↑ Volker Zota: Ogg Vorbis: Free audio codec on the rise on Heise online , March 5, 2001.
  15. ↑ Nico Jurran: Free audio format Ogg Vorbis shines golden on Heise online , July 12, 2002.
  16. ↑ Volker Zota: Real wants to support the free audio format Ogg Vorbis on Heise online , July 25, 2002.
  17. ^ Sven Hansen: Audio codec for hardware players from Ogg Vorbis auf Heise online , September 4, 2002.
  18. ↑ Volker Zota: Ogg Vorbis' portable MP3 player plays online on Heise , October 23, 2003.
  19. ↑ Jürgen Kuri: RealNetworks releases media players for Linux on Heise online , August 3, 2004.
  20. ↑ Volker Zota: New version of the audio format Ogg Vorbis auf Heise online , September 23, 2004.
  21. ↑ Thomas C Greene: Judge blasts MS bid to monopolize music devices at theregister.co.uk, October 27, 2005.