Vorbis (Ogg Vorbis in the corresponding container format) is a free audio format for lossy audio data reduction. The format was developed by the Xiph.Org Foundation as a patent-free alternative to the widely used MP3 format. The adaptability of the format was designed to allow for decades of use.
Vorbis can be encoded with both variable and constant bitrates between (average) 32 and 448 kbit/s. The format is streamable and multi-channel. As a broadband method, Vorbis supports the mapping of the entire human hearing spectrum with sampling rates of 44.1 kHz and more. Hearing tests showed 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 (AAC).
Technology of (Ogg) Vorbis Audio Format
Vorbis, like most of its kind, is a transformation codec based on modified discrete cosine transformation (MDCT). Vorbis data is usually embedded in Ogg container files (file name extension .ogg), which are also developed by the Xiph.Org Foundation. Vorbis data can also be contained in Matroska, OGM or WebM containers. For the collection of metadata, the specially developed, comparatively flexible Vorbis comment scheme is used. Vorbis supports up to 255 channels.
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In the IT industry, Vorbis has now established itself alongside MP3 and AAC. Among mobile music players, support is moderately widespread. Internet radio stations that use Vorbis. Vorbis is also used in numerous video games to compress the music, effects, and voice recordings. These include well-known titles such as: Doom 3, Far Cry, Gothic 3, Grand Theft Auto: Vice City, Grand Theft Auto: San Andreas, Minecraft, Quake 4, StarCraft II, Unreal II: The Awakening, Unreal Tournament 2003, Unreal Tournament 2004 and World of Warcraft etc to name a few.
The reference software implementations are released under a BSD-style license. In addition to these, separate developments took place in a number of spin-offs, the most important of which were also improved in the official version.
Vorbis itself is not supported on all hardware because the original implementation requires a floating-point unit, which is rarely available, especially on portable devices. Some hardware manufacturers now support the Vorbis format by default (e.g. Blackberry, Cowon, iriver, Samsung, TrekStor or SanDisk Sansa), others only after a firmware update. For some hardware, such as Apple’s iPod, there are alternative third-party firmware that offers Vorbis support. In the meantime, Vorbis support is also being 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 of (Ogg) Vorbis With MP3 and AAC
Compared to MP3 and AAC, decoding Vorbis is computationally simpler, but has a larger memory footprint because there is no static probability model and Huffman tables as well as data for the vector quantizer are included in the data stream itself. This data is only a few kilobytes in size in compressed form, but must be decompressed and stored in memory.
- One of the main differences is the different licenses: While the AAC technology is patented and licenses must be purchased for use, MP3 and Vorbis are completely free.
- MP3 and AAC, unlike Vorbis, are standardized by ISO.
- From a technical point of view, Vorbis and AAC compress more efficiently than MP3 (which is also much older) and the sound quality is still usable for voice recordings with a very strong compression (40 kbit/s).
- As is now the case with MP3, Vorbis’ specifications do not define fixed bitrates (CBRs). However, these are supported by many codecs and also by the reference implementation.
- Vorbis natively supports uninterrupted playback and replay gain. In the case of MP3, this is only possible through non-standard extensions, which 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. Significantly fewer portable players can play Vorbis, but more and more players 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.
