Vorbis is a completely open and free audio compression (codec) project from the Xiph.org Foundation. It is frequently used in conjunction with the Ogg container and is then called Ogg Vorbis.
Vorbis was started following a September 1998 letter from Fraunhofer Gesellschaft announcing plans to charge licensing fees for the MP3 format. Soon after founder Christopher Montgomery began work on the project, he was assisted by a growing collection of other developers. They continued refining the code until a stable version 1.0 of the codec was released on July 19, 2002.
The latest version is 1.1.0 http://lists.xiph.org/pipermail/vorbis-dev/2004-September/017670.html released on 2004-09-22 . Source code for this release is available from the official Vorbis web site http://www.vorbis.com/ , while many Windows binaries can be downloaded at Rarewares http://www.rarewares.org/ .
Popularity growth
The Ogg Vorbis format has proved popular among open source communities; they argue that its higher fidelity and completely free nature make it a natural replacement for the entrenched MP3 format. However, MP3 has a popular history dating back to the mid-1990s and as of 2004 is still the primary lossy audio format. It may be some time before one sees more Ogg format files than MP3 files. In the commercial sector, Vorbis has already had success with many newer video game titles employing Vorbis as opposed to MP3. The increasing number of hardware players that support Vorbis is encouraging its growth as of July 2004; see the compatible hardware below.
Technical details
Given 44.1 kHz (standard CD audio sample frequency) stereo input, the current encoder as of September 2004 will produce output from 45 to 500 kbit/s depending on the specified quality setting. Quality settings run from -1 to 10 and are an arbitary metric; files encoded at -q5, for example, should have the same quality of sound in all versions of the encoder, but newer versions should be able to achieve that quality with a lower bitrate. Vorbis is inherently variable-bitrate (VBR).
Vorbis uses the modified discrete cosine transform (MDCT) for converting sound data from the time domain to the frequency domain. The resulting frequency-domain data is broken into noise floor and residue components, and then quantized and entropy coded using a codebook-based vector quantization algorithm. The decompression algorithm reverses these stages.
Many users feel that Vorbis reaches 'transparency' (sound quality that is indistinguishable from the original source recording) at a quality setting of -q5, approximately 160kps. For comparison, it is commonly felt that MP3 reaches transparency at around 192kps, resulting in larger file sizes for the same sound quality.
Various 'tuned' versions of the encoder (Garf, aoTuV or MegaMix) attempt to provide better sound at a specified quality setting, usually by dealing with certain problematic waveforms by temporarily increasing the bitrate. The most consistently cited problem with Vorbis is 'pre-echo', a faint copy of a sharp attack that occurs just before the actual sound (the sound of castanets is commonly cited as causing this effect). Most of the 'tuned' versions of Vorbis attempt to fix this problem and to increase the sound quality of lower quality settings (-q0 through -q4). Some of the tuning suggestions created by the Vorbis user community http://www.hydrogenaudio.org/forums/index.php?act=SF&s=d78db69e2943a6f4d1a3d2eaf
3aabe4a&f=8 (especially the Garf and aoTuV tunings) have been incorporated into the 1.1 release.
Licensing
Vorbis's specifications are in the public domain (Xiph.org reserves the right to set the Vorbis specification and certify compliance). Its libraries are released under a BSD-style license and its tools are released under the GPL (GNU General Public License).
The Xiph.org Foundation says that Vorbis, like all its developments, is completely free from the licensing or patent issues raised by other proprietary formats such as MP3. Although Xiph says it has conducted a patent search that supports its claims, outside parties (notably engineers working on rival formats) have expressed doubt that Vorbis is free of patented technology. Xiph says that it was privately issued a legal opinion subject to attorney/client privilege. It has not released an official statement on the patent status of Vorbis, pointing out that such a statement is technically impossible due to the number and scope of patents in existence and the questionable validity of many of them. Such issues cannot be resolved outside of a court of law. Some Vorbis proponents have derided the uncertainty concerning the patent status as "FUD": disinformation spread by large companies with a vested interest.
Ogg Vorbis is supported by several large digital audio player manufacturers such as Rio, Neuros and iRiver. Many feel that the growing support for the Vorbis codec within the industry supports their interpretation of its patent status, as multinational corporations are unlikely to distribute software with questionable legal status.
Hardware and software support
Tremor, a version of the Vorbis decoder which uses fixed-point arithmetic (rather than floating point) was made available to the public on September 2, 2002 (also under a BSD-style license). Tremor, or platform specific versions based on it, is more suited to implementation on the limited facilities available in commercial audio systems (such as portable players). A number of versions, which make adjustments for specific platforms, and which include customised optimisations for given embedded microprocessors, have been produced. Several hardware manufacturers have expressed an intention to produce Vorbis-compliant devices, and new Vorbis devices seem to be appearing at a steady rate, especially in South Korea, although availability might differ from country to country.
Hardware
The VorbisHardware node at the xiph.org wiki http://wiki.xiph.org/VorbisHardware has an up-to-date list of Vorbis-supporting hardware, such as portables, PDAs, and microchips.
Here are a few examples of devices that play Ogg Vorbis files:
- All iRiver harddisk players support Ogg Vorbis. Most of the flash-memory players will play Ogg Vorbis without a firmware upgrade.
- The Neuros (site) http://www.neurosaudio.com portable player released a firmware upgrade offering Ogg Vorbis support after a beta testing period in the latter half of 2003. Firmware http://www.neurosaudio.com/support/support_updates.asp versions 1.45 and newer support Ogg Vorbis.
-
Rio Karma http://www.digitalnetworksna.com/shop/_templates/item_main_Rio.asp?model=261 , an mp3 player supporting both Ogg Vorbis and FLAC.
- The Jens of Sweden MP-130 (site) http://www.jensofsweden.com/ supports Ogg Vorbis.
- The Xclef HD800 [1] http://www.xclef.com/main.htm supports Ogg Vorbis amongst other formats.
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Cowon iAudio M3 [2] http://eng.cowon.com/product/iAUDIOM3/about.html
- Samsung YP-60V
- KiSS DVD-Players (site) http://www.kiss-technology.com/ are supporting Ogg Vorbis, MP3 and WMA. Some models have an Ethernet port allowing to stream audio and video from a PC on the network or listen to Web radio.
Software
Ogg Vorbis (as of 2003) can be played using these (and other) players:
In July 2002, RealNetworks announced that they will support Ogg Vorbis in their products. See Helix project for more details.
Trivia
"Ogg" is not named after the witch Nanny Ogg in Terry Pratchett's Discworld books. However, "Vorbis" is named after another Discworld character, High Priest Vorbis in Small Gods.
See also
External links
- Xiph.org Foundation http://www.xiph.org/
-
Ogg Vorbis site http://www.vorbis.com/
- Listening test comparing Vorbis to MP3, RealAudio, WMA, etc. http://www.xiph.org/ogg/vorbis/listen.html
- List of Vorbis streams http://wiki.xiph.org/VorbisStreams
- Vorbis FAQ http://www.vorbis.com/faq.psp
- Vorbis documentation http://www.xiph.org/ogg/vorbis/docs.html
- modified discrete cosine transform Description http://www.free-comp-shop.com/vorbis.html
- Christopher "Monty" Montgomery (main developer) interview, slashdot.org http://slashdot.org/article.pl?sid=00/08/14/1034209
- Listening Tests conducted by Roberto J. Amorim (comparing MP3, Vorbis, AAC, etc) http://www.rjamorim.com/test/
- Ogg Vorbis binaries at Rarewares http://www.rarewares.org/ogg.html
Last updated: 02-06-2005 02:00:18
