| Ogg Vorbis |
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Vorbis is an Open and Free Lossy Audio Compression ( Codec ) project headed by the Xiph.org Foundation . It is frequently used in conjunction with the Ogg container and is then called '''Ogg Vorbis'''. Although the Vorbis format is often simply referred to as ''Ogg'', this is technically incorrect as Ogg is a container format while Vorbis is an audio codec. Vorbis began following a September 1998 letter from Fraunhofer Gesellschaft announcing plans to charge licensing fees for the MP3 format. Soon after, founder Christopher "Monty" Montgomery commenced work on the project and 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 official version is 1.1.2 released on 2005-11-28 , but there are some fine-tuned Fork s available, like aoTuV beta 4.51. Source code (called ''libvorbis'') for the Xiph.org release is available from the official Vorbis.com web site , while many Windows binaries can be downloaded at Rarewares.org . Source code and binaries for the aoTuV release are available at the author's own site . 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 been widely used since the mid- 1990s and, As Of 2006 , is still the most prevalent Lossy audio format. {Link without Title} In the commercial sector, Vorbis is being used in many newer Video Game titles (see list below). While currently somewhat patchy, an increasing number of hardware players support Vorbis (see the compatible hardware list below). Many popular software players support the Vorbis format, with a few needing an external Plugin (see the compatible software below). Another indication of Ogg Vorbis's increasing popularity is the number of websites using it, such as Jamendo or Mindawn , as well as several national radio stations such as Radio France , CBC Radio and Virgin Radio providing additional Vorbis Streams . CODEC COMPARISONS Many other Lossy audio codecs exist, including:
Some listening tests have attempted to find the best quality lossy audio codecs at certain bitrates. The most recent large scale test at 128 kbit/s shows a four way tie between Vorbis, LAME MP3, WMA Pro and iTunes AAC, with each codec essentially transparent (sounds identical to the original music file). At 64 kbit/s, HE-AAC and mp3PRO performed better than other codecs. At higher bitrates (more than 128 kbit/s), most people do not hear significant differences. Many of these tests, however, are difficult to keep up-to-date due to the ever-evolving nature of the codecs. For many applications, Vorbis has clear advantages over other modern codecs in that it is patent-free and therefore free to use, implement, or modify as one sees fit yet produces smaller files than most other codecs at equivalent bitrates. TECHNICAL DETAILS Given 44.1 (VBR), so bitrate may vary considerably from sample to sample. 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. The noise floor approach gives Vorbis its characteristic analog noise -like failure mode (when the bitrate is too low to encode the audio without perceptible loss), which many people find more pleasing to the ears than the metallic warbling in the MP3 format. Many users feel that Vorbis reaches ''transparency'' (sound quality that is indistinguishable from the original source recording) at a quality setting of -q5, approximately 160 kbit/s. For comparison, it is commonly felt that MP3 reaches transparency at around 192 kbit/s (except for the frequency range, which only occasionally exceeds 16 kHz), 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 tuning suggestions created by the Vorbis user community (especially the aoTuV tunings) have been incorporated into the 1.1.0 release. The Vorbis format supports Bitrate Peeling for reducing the bitrate of already encoded files, and an experimental implemention of this can be found here . At the moment, re-encoding files at a lower bitrate will preserve more quality than the bitrate peeler. Vorbis streams can be encapsulated in other media Container Format s besides Ogg; another choice being MKV . Metadata Vorbis supports metadata 'tags' similar to those implemented in the ID3 standard for MP3. The metadata is stored in a vector of eight-bit-clean strings of arbitrary length and size. The size of the vector and the size of each string in bytes is limited to 232-1 (about 4.3 Billion , or any integer that can be expressed in 32 bits). This vector is stored in the second header packet that begins a Vorbis bitstream. {Link without Title} The strings are assumed to be encoded as UTF-8 , meaning that they support multiple character sets. Music tags are typically implemented as strings of the form " {Link without Title} = {Link without Title} ", for instance, "ARTIST=The John Smith Band". Since there is no strict field definition as in ID3, users and encoding software are free to use whichever tags are appropriate for the content. For example, an encoder could use localized tag labels, live music tracks might contain a "Venue=" tag or files could have multiple genre definitions. LICENSING Knowledge of Vorbis's specifications is in the states 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.org 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 {Link without Title} . Xiph.org maintains 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 ": misinformation spread by large companies with a vested interest. Ogg Vorbis is supported by several large Digital Audio Player manufacturers such as Samsung , Rio , Neuros , Cowon 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. The same could be said about its growing popularity in other commercial enterprises like mainstream computer games. USE IN VIDEO GAMES Since the Vorbis libraries are available under a BSD Licence (a Free Software Approved licence) and the format itself is Accepted as not covered by patents, several video game developers {Link without Title} have chosen to use Vorbis in their games rather than pay for patent-encumbered competitors like MP3. Some PC examples include:
A full list can be found at Xiph.org Wiki In addition to the PC, Vorbis has also gained popularity on video game consoles due to the need for developers to compress game data. Known console games which use Vorbis include:
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 portable players. A number of versions that make adjustments for specific platforms and include customized optimizations 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 may differ from country to country. Hardware The VorbisHardware node at the xiph.org wiki has an up-to-date list of Vorbis-supporting hardware, such as portables, PDAs, and microchips. Most players supported by Rockbox are capable of decoding Vorbis. Software The VorbisSoftwarePlayers node at the xiph.org wiki has an up-to-date list of Vorbis-supporting software for all operating systems. Users can test these players using the list of Vorbis audio streams available at [http://wiki.xiph.org/index.php/VorbisStreams]. Although . Windows DirectShow filters exist to decode Vorbis in multimedia players like Windows Media Player and others which support DirectShow . In July 2002 , RealNetworks announced that they would support Ogg Vorbis in their products. See Helix Project for more details. However, as of January 2006, only RealPlayer 10 for Linux supports Vorbis. TRIVIA
SEE ALSO
LISTENING TESTS
EXTERNAL LINKS
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