View source for Internet Low Bitrate Codec

{{short description|Audio coding format}}
{{Infobox file format
|name         = Internet Low Bit Rate Codec (iLBC)
|icon         =
|logo         = 
|caption      = 
|extension    = .lbc<ref name="rfc3952">{{cite web |url=http://tools.ietf.org/html/rfc3952 |title=Real-time Transport Protocol (RTP) Payload Format for internet Low Bit Rate Codec (iLBC) Speech |year=2004 |access-date=2011-06-23 |last1=Duric |first1=Alan |last2=Andersen |first2=Soren Vang }}</ref>
|mime         = audio/iLBC<ref name="rfc3952" />
|type code    =
|uniform type =
|magic        = '#!iLBC30\n' or '#!iLBC20\n'<ref name="rfc3952" />
|owner        = [[Global IP Solutions]], now [[Google Inc]]
|released     = {{Start date|2004|df=yes}}<ref name="rfc3952" /><!-- {{Start date|YYYY|mm|dd|df=yes}} -->
|latest release version = 
|latest release date    = <!-- {{Start date and age|YYYY|mm|dd|df=yes/no}} -->
|genre        = [[Audio compression format]]
|containerfor =
|containedby  = 
|extendedfrom =
|extendedto   =
|standard     = RFC 3951
|url          =
}}
{{Infobox software
| name                   = iLBC Speech Coder
| logo                   =
| screenshot             =
| caption                =
| collapsible            =
| author                 = 
| developer              = [[Global IP Solutions]], now [[Google Inc]]
| released               = 2004
| programming language   = [[C (programming language)|C]]
| size                   =
| language               =
| genre                  = [[Audio codec]], [[reference implementation (computing)|reference implementation]]
| license                = [[BSD licenses|3-clause BSD]]
| website                = [https://webrtc.org/license/ilbc-freeware https://webrtc.org/license/ilbc-freeware]
| latest_release_version = 
| latest_release_date    = 
| latest_preview_version =
| latest_preview_date    =
| operating_system       = [[Cross-platform]]
}}
'''Internet Low Bitrate Codec''' ('''iLBC''') is a [[royalty-free]] [[narrowband]] [[Speech communication|speech]] [[audio coding format]] and an [[open-source software|open-source]] [[reference implementation]] ([[codec]]), developed by [[Global IP Solutions]] (GIPS) formerly Global IP Sound (acquired by [[Google Inc]] in 2011<ref>{{cite web |url=http://www.zdnet.com/blog/open-source/why-google-bought-global-ip-solutions/6501 |archive-url=https://web.archive.org/web/20100521163742/http://www.zdnet.com/blog/open-source/why-google-bought-global-ip-solutions/6501 |url-status=dead |archive-date=May 21, 2010 |title=Why Google bought Global IP Solutions |author=Dana Blankenhorn |website=[[ZDNet]] |date=2010-05-18 |access-date=2011-06-23}}</ref>). It was formerly [[freeware]] with limitations on commercial use,<ref>{{cite web|url=http://www.ilbcfreeware.org/documentation/gips_iLBClicense.pdf |title=Global IP Solutions iLBC Freeware Public License |date=2008-10-30 |access-date=2011-06-23 |url-status=dead |archive-url=https://web.archive.org/web/20081030043137/http://www.ilbcfreeware.org/documentation/gips_iLBClicense.pdf |archive-date=October 30, 2008 }}</ref><ref>{{cite web|url=http://www.ilbcfreeware.org/ |title=iLBCfreeware |url-status=dead |archive-url=https://web.archive.org/web/20081219092331/http://www.ilbcfreeware.org/ |archive-date=December 19, 2008 }}</ref> but since 2011 it is available under a [[free software]]/open source ([[BSD licenses#3-clause license ("New BSD License" or "Modified BSD License")|3-clause BSD license]]) license as a part of the open source [[WebRTC]] project.<ref name=licence>{{cite web |url=http://www.webrtc.org/ilbc-freeware |title=iLBC Freeware |access-date=2011-06-23 |url-status=dead |archive-url=https://web.archive.org/web/20110705082246/http://www.webrtc.org/ilbc-freeware |archive-date=2011-07-05 }}</ref> It is suitable for [[VoIP]] applications, [[streaming audio]], archival and messaging. The algorithm is a version of block-independent [[linear predictive coding]], with the choice of [[data frame]] lengths of 20 and 30 milliseconds. The encoded blocks have to be encapsulated in a suitable protocol for transport, usually the [[Real-time Transport Protocol]] (RTP).

iLBC handles  lost frames through graceful speech quality degradation. Lost frames often occur in connection with lost or delayed IP packets. Ordinary low-bitrate codecs exploit dependencies between speech frames, which cause errors to propagate when packets are lost or delayed. In contrast, iLBC-encoded speech frames are independent and so this problem will not occur.

iLBC is defined in RFC 3951. It is one of the codecs used by [[Gizmo5]], [[WebRTC]], [[Ekiga]], [[Google Talk]], [[Maemo Recorder]] (on the [[Nokia N800]]/[[Nokia N810|N810]]), [[Polycom IP Phone]], [[Cisco]], [[QuteCom]], [[Tuenti]],<ref>{{Cite web|url=https://vimeo.com/109608566|title=Tuenti+WebRTC (Voip2day 2014)}}</ref> [[Yahoo! Messenger]], [[Ooma]]<ref>{{citation | url= http://support.ooma.com/home/star-codes-on-your-ooma-device/ |title=Ooma * codes|date=12 May 2015 }}</ref> and many others.

iLBC was submitted to IETF in 2002<ref>{{citation |url=http://www.itu.int/itudoc/itu-t/workshop/converge/s6am-p4_pp7.ppt |title=Speech Coders - a VoIP perspective |author=Roar Hagen |access-date=2011-06-23}}</ref><ref>{{cite web |url=http://tools.ietf.org/html/draft-andersen-ilbc-00 |title=Internet Low Bit Rate Codec - draft-andersen-ilbc-00.txt |year=2002 |access-date=2011-06-23 |last1=Duric |first1=Alan |last2=Andersen |first2=Steven C. }}</ref> and the final specification was published in 2004.

==Parameters and features==
* [[Sampling frequency]] 8&nbsp;kHz/16 bit (160 samples for 20 ms frames, 240 samples for 30 ms frames)
* Controlled response to [[packet loss]], delay and [[jitter]]
* Fixed [[bitrate]] (15.2&nbsp;kbit/s for 20 ms frames, 13.33&nbsp;kbit/s for 30 ms frames)
* Fixed frame size (304 bits per block for 20 ms frames, 400 bits per block for 30 ms frames)
* Robustness similar to [[pulse-code modulation]] (PCM) with [[packet loss concealment]], like the [[International Telecommunication Union|ITU]]-T [[G.711]]
* CPU load similar to [[G.729A]], with higher basic quality and better response to packet loss
* [[Royalty-free]]
* Since 2011 it is available under an open source ([[BSD licenses#3-clause license ("New BSD License" or "Modified BSD License")|3-clause BSD license]]) license as a part of the open source [[WebRTC]] project.<ref name=licence /> (previously commercial use of the source code supplied by GIPS required a licence<ref>{{Cite web|url=http://www.ilbcfreeware.org/documentation/gips_iLBClicense.pdf|archive-url=https://web.archive.org/web/20081030043137/http://www.ilbcfreeware.org/documentation/gips_iLBClicense.pdf|url-status=dead|title=former GIPS license|archive-date=October 30, 2008}}</ref>)
* [[PSQM]] testing under ideal conditions yields [[mean opinion score]]s of 4.14 for iLBC (15.2&nbsp;kbit/s), compared to 4.3 for [[G.711]] ([[μ-law]])

==See also==
*[[RTP audio video profile]]
*[[Comparison of audio coding formats]]

==References==
{{reflist|2}}

==External links==
* [https://web.archive.org/web/20110705082246/http://www.webrtc.org/ilbc-freeware Official homepage]
* [https://web.archive.org/web/20080513185652/http://www.ilbcfreeware.org/ iLBC former homepage]

{{Compression formats}}
{{Compression Software Implementations}}

[[Category:Speech codecs]]
[[Category:Free audio codecs]]
[[Category:Open formats]]
[[Category:Software using the BSD license]]
[[Category:Formerly proprietary software]]