Name

Usage

Codec comparisons

• Low bitrate (less than 64 kbit/s): the most recent public multiformat test at 48 kbit/s shows that aoTuV Vorbis has a better quality than WMA and LC-AAC, the same quality of WMA Professional, and a lower quality than HE-AAC.
• Mid to low bitrates (less than 128 kbit/s down to 64 kb/s): private tests at 80 kbit/s and 96 kbit/s shows that aoTuV Vorbis has a better quality than other lossy audio codecs (LC-AAC, HE-AAC, MP3, MPC, WMA).
• Mid bitrate (128kb/s): most recent public multiformat test at 128 kbit/s shows a four-way tie between aoTuV Vorbis, LAME-encoded MP3, WMA Pro, and QuickTime AAC, with each codec essentially transparent (sounds identical to the original music file).
• High bitrates (more than 128 kb/s): most people don't hear significant differences. However, trained listeners can often hear significant differences between codecs at identical bitrates, and aoTuV Vorbis performs better than LC-AAC, MP3, and MPC.

Listening tests

2005-2006 Public group test of Lame MP3, Vorbis AoTuV, iTunes AAC, Nero AAC, and WMA Pro at ~135 kbit/s nominal. Results suggest that further group testing at this bitrate is unnecessary because all codecs are statistically tied near transparency.
   The Vorbis format supports bitrate peeling for reducing the bitrate of already encoded files, and an experimental implementation is available. However, encoding at the lower bitrate will result in better audio quality than this experimental bitrate peeler.
   Vorbis streams can be encapsulated in other media container formats besides Ogg. A commonly used alternative is Matroska.

Metadata

Vorbis metadata, called comments, support 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.
   The strings are assumed to be encoded as UTF-8. Music tags are typically implemented as strings of the form "[TAG]=[VALUE]", for instance, "ARTIST=The John Smith Band". Like the current version of 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. Most applications also support common de facto standards such as discnumber and Replay Gain information.

Licensing

Knowledge of Vorbis's specifications is in the public domain. Concerning the specification itself, the Xiph.Org Foundation reserves the right to set the Vorbis specification and certify compliance. Its libraries are released under the revised 3-clause BSD license and its tools are released under the GNU General Public License. The libraries were originally released under the GNU Lesser General Public Licence, but a BSD license was later chosen with the endorsement of Richard Stallman. The Xiph.Org Foundation 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 the Xiph.Org Foundation states 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.
   The Xiph.Org Foundation maintains that it was privately issued a legal opinion subject to attorney-client privilege. It hasn't 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 can't 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.
   Vorbis is supported by several large digital audio player manufacturers such as Samsung, Rio, Neuros Technology, 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.

Hardware and software support

Hardware

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.
   Many high-end digital audio players such as Cowon's popular D2 and iAudio X5 ship with full ogg support. Although many digital audio players such as Apple's iPod don't natively support Vorbis, through the use of Rockbox, an open-source firmware project, many become capable of decoding Vorbis files. Support continues to grow; in May 2008 Sandisk added Vorbis capability to the 1.01.29 firmware for the Sansa Clip player. The Xiph.Org Foundation wiki has an up-to-date list of Vorbis-supporting hardware, such as portables, PDAs, and microchips.

Software

Software supporting Vorbis exists for many platforms. Although Apple iTunes doesn't natively support Vorbis, the Xiph.Org Foundation provides a QuickTime component which can be used in iTunes and QuickTime on both Microsoft Windows and Mac OS. On Windows, DirectShow filters exist to decode Vorbis in multimedia players like Windows Media Player and others which support DirectShow. Vorbis is well-supported on the Linux platform in programs like XMMS, xine, and many more. More information about Vorbis-supporting software can be found at the Xiph.Org Foundation wiki. Users can test these programs using the list of Vorbis audio streams available on the same wiki. The ever-popular Winamp can also play ".ogg" vorbis files.

Implementations

Because of Vorbis's free and open nature, developers are free to write compliant encoders and decoders.

Official

The Xiph.Org Foundation's reference implementation is free and open source, and licensed under the BSD License and the GNU Lesser General Public License.

aoTuV

Modified versions of the reference encoder are also available: aoTuV is a version that has received quality tweaks since the release of libVorbis 1.0; previous changes from aoTuV (Beta2) have been merged back into the Xiph.Org Foundation's libVorbis 1.1. Lancer is a modified version of aoTuV focusing on encoding speed. Current version: aoTuV Beta5.5 (2008/03/31)

Tremor

Tremor is an implementation of a Vorbis decoder using fixed-point arithmetic. It is intended for environments when a floating-point arithmetic unit is unavailable. The Xiph.Org Foundation has expressed interest in modifying Tremor into a floating-point version, which would replace the current floating-point reference decoder.

FFmpeg

The libavcodec library contains an LGPL-licensed Vorbis decoder that's faster than the reference implementation.
   

Further Information

Get more info on 'Ogg Vorbis'.

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