Difference between revisions of "Vorbis"

From Hydrogenaudio Knowledgebase
Jump to: navigation, search
m (fixed spacing, renamed hardware to supported digital audio players)
(capped vorbis; proper noun)
 
(248 intermediate revisions by 27 users not shown)
Line 1: Line 1:
=Introduction=
+
{{featured}}
'''Ogg Vorbis''' ([http://www.vorbis.com www.vorbis.com]) is a fully open, non-proprietary, patent-free <small>(subject to [http://www.hydrogenaudio.org/forums/index.php?showtopic=13531 speculation])</small>, and royalty-free, general-purpose compressed audio format for mid to high quality (8khz-48.0kHz, 16+ bit, polyphonic) 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 [[MP3]], twinvq ([[VQF]]), [[WMA]] and [[PAC]].
+
{{Codec Infobox
 +
| name      = Ogg Vorbis
 +
| logo      = [[Image:Fish logo.png]]
 +
| type      = lossy
 +
| purpose    = General audio compression at bitrates ~64–400 kbps
 +
| maintainer = Christopher Montgomery, Xiph Community
 +
| website    = http://www.vorbis.com/
 +
}}
 +
{{infobox ha recommended encoder
 +
| encoder = [[aoTuV]]
 +
| encoder version = beta 5
 +
| encoder release date = {{start date and age|2006|10|24}}
 +
}}
 +
'''Vorbis''' (commonly used inside the [[Ogg]] container) is a fully open, non-proprietary, patent-free (subject to [http://www.hydrogenaudio.org/forums/index.php?showtopic=13531 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.
  
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.
  
Informal listening test suggests Vorbis to be comparable to MPEG-4 [[AAC]] at most bitrates and [[MPC]] 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 [http://sjeng.org/vorbisgt3.html Garf] and [http://www.geocities.jp/aoyoume/aotuv/ 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 <span style="color:blue;">it is currently the recommended Vorbis encoder at Hydrogenaudio.</span>
  
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 lead by other coders such as [http://sjeng.org/vorbisgt3.html Garf] and [http://www.geocities.jp/aoyoume/aotuv/ 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. Currently Aoyumi is working on AoTuv Beta 4 and future releases.  
+
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 [http://www.openal.org/extensions.html OpenAL] API extension library, used in many popular [http://www.openal.org/titles.html computer games]. On April 10, 2006, [http://www.radgametools.com/ 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 [http://wiki.xiph.org/index.php/Games_that_use_Vorbis xiph wiki] for a full list of games confirmed to use (Ogg) Vorbis.
  
==Pros==
+
Vorbis was recently adopted in May of 2010 as the open source codec for Google's new [http://www.webmproject.org/ 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.
* Free (as in speech), Open Source and claimed to be patent free
+
 
* Good all-round performance (>48 kbps - a leading codec at [http://www.rjamorim.com/test/multiformat128/results.html 128 kbps])
+
'''Before encoding files using (Ogg) Vorbis, check out the [[Recommended Ogg Vorbis|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 [http://web.archive.org/web/20070403025834/http://www.rjamorim.com/test/multiformat128/results.html 128 kbps])
 
* Well written [http://www.xiph.org/ogg/vorbis/docs.html specs]
 
* Well written [http://www.xiph.org/ogg/vorbis/docs.html specs]
* Several portable [http://wiki.hydrogenaudio.org/index.php?title=Ogg_Vorbis#Hardware hardware players]  
+
* Supported by most portable (Ogg) [[Vorbis#Supporting Digital Audio Players|DAPs]]
 
* Suitable for internet-streaming (via [http://www.icecast.org/ Icecast] and other methods)
 
* Suitable for internet-streaming (via [http://www.icecast.org/ Icecast] and other methods)
 
* Fully [[gapless]] playback
 
* Fully [[gapless]] playback
 
* High potential for further tuning
 
* High potential for further tuning
 +
* Structured to allow the design for a hybrid filterbank
  
==Cons==
+
===Cons===
* Limited official development (third-party developement is always encouraged)
+
* Limited official development (third-party development is always encouraged)
* Current implementations are more computationally intensive to encode and decode than MP3 (Vorbis 2.0 seeks to overcome this limitations by slimlining the encoder)
+
* Some implementations are more computationally intensive to decode than MP3 (depending upon the architecture and [[Tremor]] optimizations).
* Quality could benefit from further tuning
+
  
 +
== 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)
 +
:<math>w_k = \sin{(\frac{\pi}{2} \cdot sin^2[(\pi\div2n \cdot (k+0.5))]}</math>
 +
* Psychoacoustics masking is exploited via an ([[ATH]] model)
 +
* Masking curves are computed from an ''emperically'' adjusted set of [http://www.zainea.com/masking2.htm 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 [http://www.data-compression.com/speech.html#ana 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 [[channel coupling|coupled]] ''strictly'' by residue using ([http://us.xiph.org/ogg/vorbis/doc/stereo.html 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
  
=Technologies used in compression=
+
== Software ==
* Advanced psymodel (based upon [[ATH]] model)
+
=== Encoders ===
* Coupled stereo modes ([http://us.xiph.org/ogg/vorbis/doc/stereo.html point/phase stereo] and lossless)
+
* [[Oggenc]] official command-line encoder (Win32/Posix)
* [[Huffman coding]]
+
* [[OggDropXPd|OggdropXPd]] advanced drag-and-drop encoder by John33 (Win32)
* [[Vector quantization]]
+
* [[Lancer]] SSE-optimized vorbis encoder utility and libraries by BlackSword (Win32/Posix)
* Modified Discrete Cosine Transform ([[MDCT]])
+
* [http://www.saunalahti.fi/cse/foobar2000/ foo_vorbisenc] vorbis encoder library for foobar2000 (Win32)
* Multiple block sizes for window switching
+
  
 +
=== Decoders ===
 +
* [http://www.rarewares.org/ogg.html 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)
 +
* [http://www.illiminable.com/ogg/ illiminable Ogg Directshow Filters] also plays Speex, Theora and FLAC (Win32)
 +
* [http://www.xiph.org/quicktime/ XiphQT] (Xiph's QuickTime Components) allows playback in [[QuickTime]]/[[iTunes]] (Win32/MacPPC/MacIntel)
 +
* [http://corevorbis.corecodec.org/ CoreVorbis] DirectShow filter (Win32)
  
=Software=
+
=== ReplayGain ===
'''Encoders'''
+
* [http://www.rarewares.org/ogg.html VorbisGain] to apply [[ReplayGain]] on Vorbis files (Win32)
* [[oggenc]] (Win32/Posix)
+
** Instructions to integrate VorbisGain into foobar2000, Winamp, and Windows Explorer can be found in [http://www.hydrogenaudio.org/forums/index.php?s=&showtopic=41880&view=findpost&p=396612 this HA thread]<br />''A precompiled script of the procedure (in RAR format) can be found in [http://www.hydrogenaudio.org/forums/index.php?s=&showtopic=45196&view=findpost&p=397803 this HA posting]''
* [[oggdropXPd]] (Win32)
+
** RPM packages for VorbisGain are available [http://rpm.pbone.net/index.php3?stat=3&search=vorbisgain&srodzaj=3 here], and source code for VorbisGain is available [http://sjeng.org/vorbisgain.html here]
* [http://www.saunalahti.fi/cse/foobar2000/foo_vorbisenc.zip foo_vorbisenc] (foobar2000)
+
* [http://www.rarewares.org/quantumknot/vorbisgain.gz 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
  
'''Decoders'''
+
=== Splitters ===
* [[ogg123]] for Unix systems (GPL), a very simple to use command-line player.  
+
The following utilities are used to splice Vorbis streams without decoding/re-encoding.
* [http://qtcomponents.sourceforge.net/ QuickTime Component] (Allows playback in [[QuickTime]]/[[iTunes]])
+
* [http://corevorbis.corecodec.org/ CoreVorbis] (DirectShow)
+
* [http://www.illiminable.com/ogg/ illiminable Ogg Directshow Filters] (Also plays Speex, Theora and FLAC)
+
  
 +
* [http://www.free-codecs.com/download/Ogg_Cutter.htm Ogg Cutter] (Win32)
 +
* [http://mp3splt.sourceforge.net/ mp3splt] (Win32)
 +
* [http://www.xiph.org/downloads/ vcut] (CLI tool part of the official vorbis-tools package) (Win32/Posix)
 +
* [http://sourceforge.net/projects/ogg-cut/ (Ogg) Vorbis Stream Cutter (ogg-cut)] (Posix)
  
=Supported Digital Audio Players=
+
=== Taggers ===
 +
Most tagger supporting (Ogg) Vorbis are listed in [[download page#Tagging Utilities|the download page]].
 +
* [http://www.rarewares.org/files/ogg/vorbiscomment-1.1.1.zip Vorbis Comment]
 +
 
 +
== Supported digital audio players ==
 
The following list contains some players that support Vorbis playback.
 
The following list contains some players that support Vorbis playback.
* [[iRiver H-Series]]
+
* [[Apple iPod]] with [[Rockbox]] firmware – check out this [http://www.hydrogenaudio.org/forums/index.php?s=32eeac65958144db631c8a739b41983c&showtopic=40992 HA thread]
* [[MPIO H-Series]]  
+
* [http://www.ifreemax.com/ FreeMax] FW-960
 +
* [http://www.iaudiophile.net/ iAudio] [[IAudio M3|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]]
 
* [[Rio Karma]]
* [[IAudio M3]]
+
* [http://www.samsung.com/Products Samsung]
* [[Neuros]]
+
* [http://www.slimdevices.com/ Slim Devices: Squeezebox] External player
 +
* [http://www.sony.com/electronics/walkman-digital-music-players/t/walkman Sony Walkman]
 +
* [http://www.yepp.co.kr/ Yepp] YP-T6, YP-T7, YP-C1, YP-F1, YP-53 (Firmware 1.200), other..
  
 +
A longer list can be found at [http://wiki.xiph.org/index.php/PortablePlayers xiph's wiki].
  
=External links=
+
'''Important note:''' There may be players out there that support (Ogg) Vorbis, although they are not marketed as such.
The following links contain information surrounding the Ogg Vorbis codec that can be found on Hydrogenaudio and elsewhere throughtout the web.  
+
 
 +
== 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)
 
* [[Ogg]] (Container)
* [http://en.wikipedia.org/wiki/Vorbis Ogg Vorbis at Wikipedia.]  
+
* [[Listening Tests#Multiformat Tests|Listening tests comparing Vorbis against MP3, AAC, WMA, etc.]]
* [http://www.audiocoding.com/modules/wiki/?page=Ogg+Vorbis Ogg Vorbis at AudioCoding]
+
* [[Recommended Ogg Vorbis|Recommended settings for encoding with Vorbis]] and its related [http://www.hydrogenaudio.org/forums/index.php?showtopic=15049 HA thread]
* [http://www.rarewares.org/ogg.html Ogg Vorbis binaries at Rarewares. ]
+
* [[EAC and Ogg Vorbis|Configuring EAC and Vorbis as an external command-line encoder]]
* [http://www.hydrogenaudio.org/show.php/showtopic/13531 Discussion of Vorbis' legal status]
+
 
* [http://www.hydrogenaudio.org/forums/index.php?showtopic=15049 Recommended settings thread for encoding with Vorbis.]
+
=== Websites ===
* [http://www.geocities.jp/aoyoume/aotuv/ Aoyumi homepage tuned versions of Vorbis 1.1 encoder and current beta binaries.]
+
* [http://www.vorbis.com Vorbis official website] (updated continually)
* [http://homepage3.nifty.com/blacksword/index_e.htm Archer homepage optimized versions of AoTuV Beta 3 Vorbis encoder and SSE optmizations. ]
+
* [http://en.wikipedia.org/wiki/Vorbis Vorbis at Wikipedia]
* [http://www.xiph.org Xiph.org Foundation]
+
* [http://www.playogg.org/ PlayOgg initiative] by the [http://www.fsf.org/ Free Software Foundation]
 +
* [http://www.audiocoding.com/modules/wiki/?page=Ogg+Vorbis (Ogg) Vorbis at AudioCoding]
 +
* [http://www.rarewares.org/ogg.html (Ogg) Vorbis binaries at Rarewares]
 +
* [http://www.geocities.jp/aoyoume/aotuv/ Aoyumi's homepage of tuned versions of Vorbis encoder and current beta binaries]
 +
* [http://homepage3.nifty.com/blacksword/index_e.htm The (Ogg) Vorbis Acceleration Project] – Archer/[[Lancer]] homepage for optimized versions of aoTuV Vorbis encoder and other SSE optmizations
 +
* [http://www.xiph.org/ Xiph.org Foundation]
 +
 
 +
=== Scientific/R&D ===
 +
* [http://www.hydrogenaudio.org/forums/index.php?showtopic=20132&st=0 Noise Normalization and HF Boost problem solution that ultimatly lead to the aoTuV tunings (HA Thread)]
 +
* [http://www.free-comp-shop.com/vorbis.pdf Keith Wright rendition of understanding the MDCT in Vorbis by defining it's basic trig properties (PDF)]
 +
* [http://www.mp3-tech.org/programmer/docs/embedded_vorbis_thesis.pdf (Ogg) Vorbis decoder for an embedded system (Master Thesis in PDF)]
 
* [http://wiki.xiph.org/index.php/Bounties Xiph.org Vorbis bounties]
 
* [http://wiki.xiph.org/index.php/Bounties Xiph.org Vorbis bounties]
 +
 +
{{navbox audio codecs}}
 +
 +
[[Category:Lossy]]

Latest revision as of 13:38, 15 March 2022

Featured article

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[edit]

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[edit]

  • (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[edit]

  • 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[edit]

  • 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\div2n \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[edit]

Encoders[edit]

  • 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[edit]

ReplayGain[edit]

Splitters[edit]

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

Taggers[edit]

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

Supported digital audio players[edit]

The following list contains some players that support Vorbis playback.

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[edit]

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

Hydrogenaudio Wiki[edit]

Websites[edit]

Scientific/R&D[edit]