Vorbis

Ogg Vorbis
General audio compression at bitrates ~64–400 kbps
Developer(s)	Christopher Montgomery, Xiph Community
Release	TBC
Type	Lossy
Recommended encoder	[[{{{recommended_encoder}}}|{{{recommended_encoder}}}]]
Website	http://www.vorbis.com/

hydrogenaudio
recommended encoder

Encoder	aoTuV, beta 5
Released	October 24, 2006; 18 years ago

Vorbis (commonly used inside the Ogg container) is a fully open, non-proprietary, patent-free (subject to speculation), and royalty-free, general-purpose compressed audio format for mid to high quality (8 khz–48.0 kHz, 16+ bit, multichannel) audio and music at fixed and variable bitrates from 16 to >256 kbps/channel. This places Vorbis in the same competitive class as audio representations such as MPEG-4 (AAC), and similar to, but higher performance than MP3, TwinVQ (VQF), WMA and PAC. Vorbis is the first of a planned family of Ogg multimedia coding formats being developed as part of Xiph.org's ogg multimedia project.

Introduction

Informal listening test suggests Vorbis to be comparable to MPEG-4 AAC at most bitrates and Musepack at 128 kbps. Transparency is generally reached at about 150–170 kbps (-q 5) (with some exceptions). The encoder is reasonably young and unoptimized, so further improvements can always be expected.

Unfortunately, Xiph.org has failed to improve Vorbis at a steady rate since its initial 1.0 release in July 2002 (due to other developement projects and time constraints). Since then development has been led by other coders such as Garf and Aoyumi. Aoyumi's aoTuV series of encoders was incorporated into the September 2004 release of 1.1, which brought about the first quality improvements across the board for 2 years. Aoyumi's Beta 4.51 was found to be very good, so it was re-branded into aoTuV Release 1 and it was the recommended encoder until June 2007. The latest tuning is aoTuV beta 5, which improves further on the low-bitrate quality without sacrificing compression, and it is currently the recommended Vorbis encoder at Hydrogenaudio.

At the time being, Aoyumi's tuning (since aoTuV Release 1 up to aoTuV Beta 5) has not been incorporated yet into the 'official' Vorbis line.

Vorbis has had success with many recent video game titles employing Vorbis as opposed to MP3 (with Epic Games' Unreal Tournament 2003 and Unreal Tournament 2004, the PC port of Microsoft's Halo and Uru being notable examples). (Ogg) Vorbis is also an official part of the OpenAL API extension library, used in many popular computer games. On April 10, 2006, RAD Game Tools integrated (Ogg) Vorbis support to their Miles Sound System (MSS), which has been used in over 3,200 games worldwide. This ensures that future games utilizing MSS will have the capability to play (Ogg) Vorbis files. Check out xiph wiki for a full list of games confirmed to use (Ogg) Vorbis.

Vorbis was recently adopted in May of 2010 as the open source codec for Google's new WebM project. WebM is combination of the BSD licensed VP8 video codec, Vorbis, and the webm container a subset of the Matroska container. It is expected to obtain widespread adoption with a major backing by many hardware based chip manufactures and with the release of Google's new mobile Android platform and Google TV by the year 2011.

Before encoding files using (Ogg) Vorbis, check out the Recommended (Ogg) Vorbis article to determine what encoder to use and what settings are recommended by Hydrogenaudio.

Pros

• (Ogg) Vorbis specification is in the public domain; it is free for commercial or noncommercial use, under both (LGPL and BSD licenes)
• Easy to use high-level API (Application Programming Interface)
• Good all-round performance (>48 kbps – a leading codec at 128 kbps)
• Well written specs
• Supported by most portable (Ogg) DAPs
• Suitable for internet-streaming (via Icecast and other methods)
• Fully gapless playback
• High potential for further tuning
• Structured to allow the design for a hybrid filterbank

Cons

• Limited official development (third-party development is always encouraged)
• Some implementations are more computationally intensive to decode than MP3 (depending upon the architecture and Tremor optimizations).

Technical information

• Multiple block sizes for window switching including overlap (powers of two only) (128/1024, 256/2048, 512/4096)
• Customly designed window function is applied similiar to the sine window. it has (good sidelobe rejection)

$w_{k}=\sin {({\frac {\pi }{2}}\cdot sin^{2}[(\pi \div 2n\cdot (k+0.5))]}$

• Psychoacoustics masking is exploited via an (ATH model)
• Masking curves are computed from an emperically adjusted set of Ehmer Curves
• Modified Discrete Cosine Transform (MDCT) is used for noise analysis
• Fast Fourier Transform (FFT) is used for tonal analysis
• Global masking curve is a mixture between calculated FFT+MDCT curves and ATH curves overlayed
• Floor 1 or the noise-floor (envelope) is calculated using the global masking curve & piecewise linear approximation divided by spectrum to generate the residue (fine detail). The Levinson-Durbin LPC model in Floor 0 is no longer used, however the code still exists
• Noise normalization is applied to compensate for energy lost in certain frequency bands due to quantization (rounding).
• The channels are coupled strictly by residue using (point/phase stereo and lossless)
• Multistage Vector quantization is used for coding the noise-floor and residue backend using trained codebooks.
• Huffman coding is used to minimize vector codeword redundancy

Software

Encoders

• Oggenc official command-line encoder (Win32/Posix)
• OggdropXPd advanced drag-and-drop encoder by John33 (Win32)
• Lancer SSE-optimized vorbis encoder utility and libraries by BlackSword (Win32/Posix)
• foo_vorbisenc vorbis encoder library for foobar2000 (Win32)

Decoders

• OggDec for Windows, by John33, a very featureful command line decoder (Win32)
• Ogg123 for Unix systems (GPL), a very simple to use command-line player. (Win32/Posix)
• illiminable Ogg Directshow Filters also plays Speex, Theora and FLAC (Win32)
• XiphQT (Xiph's QuickTime Components) allows playback in QuickTime/iTunes (Win32/MacPPC/MacIntel)
• CoreVorbis DirectShow filter (Win32)

ReplayGain

• VorbisGain to apply ReplayGain on Vorbis files (Win32)
  • Instructions to integrate VorbisGain into foobar2000, Winamp, and Windows Explorer can be found in this HA thread
    A precompiled script of the procedure (in RAR format) can be found in this HA posting
  • RPM packages for VorbisGain are available here, and source code for VorbisGain is available here
• VorbisGain Static GCC 4 compile (Posix)
• foobar2000's ReplayGain scanner supports (Ogg) Vorbis files
• Winamp's ReplayGain Analyzer supports (Ogg) Vorbis files
• MediaMonkey's Volume Levelling supports (Ogg) Vorbis files

Splitters

The following utilities are used to splice Vorbis streams without decoding/re-encoding.

• Ogg Cutter (Win32)
• mp3splt (Win32)
• vcut (CLI tool part of the official vorbis-tools package) (Win32/Posix)
• (Ogg) Vorbis Stream Cutter (ogg-cut) (Posix)

Taggers

Most tagger supporting (Ogg) Vorbis are listed in the download page.

• Vorbis Comment

Supported digital audio players

The following list contains some players that support Vorbis playback.

• Apple iPod with Rockbox firmware – check out this HA thread
• FreeMax FW-960
• iAudio M3, M5, U2, G3, X5, I5, 7, D2, F2, T2, A3, Q5W, A2; VorbisGain support only on X5/M5 with Rockbox firmware
• iRiver H-Series with Rockbox firmware
• MPIO H-Series
• Neuros with Rockbox firmware
• Rio Karma
• Samsung
• Slim Devices: Squeezebox External player
• Sony Walkman
• Yepp YP-T6, YP-T7, YP-C1, YP-F1, YP-53 (Firmware 1.200), other..

A longer list can be found at xiph's wiki.

Important note: There may be players out there that support (Ogg) Vorbis, although they are not marketed as such.

External links

The following links contain information surrounding the (Ogg) Vorbis codec that can be found on Hydrogenaudio and elsewhere throughout the web.

Hydrogenaudio Wiki

• Ogg (Container)
• Listening tests comparing Vorbis against MP3, AAC, WMA, etc.
• Recommended settings for encoding with Vorbis and its related HA thread
• Configuring EAC and Vorbis as an external command-line encoder

Websites

• Vorbis official website (updated continually)
• Vorbis at Wikipedia
• PlayOgg initiative by the Free Software Foundation
• (Ogg) Vorbis at AudioCoding
• (Ogg) Vorbis binaries at Rarewares
• Aoyumi's homepage of tuned versions of Vorbis encoder and current beta binaries
• The (Ogg) Vorbis Acceleration Project – Archer/Lancer homepage for optimized versions of aoTuV Vorbis encoder and other SSE optmizations
• Xiph.org Foundation

Scientific/R&D

• Noise Normalization and HF Boost problem solution that ultimatly lead to the aoTuV tunings (HA Thread)
• Keith Wright rendition of understanding the MDCT in Vorbis by defining it's basic trig properties (PDF)
• (Ogg) Vorbis decoder for an embedded system (Master Thesis in PDF)
• Xiph.org Vorbis bounties