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Siren is a patented, transform-based, [[wideband audio|wideband]] [[audio codec]] developed and licensed by PictureTel Corporation (now [[Polycom]], Inc.).<ref name="picturetel">{{cite web |author=Business Wire |publisher=thefreelibrary.com |url=http://www.thefreelibrary.com/PictureTel+Announces+New+Siren+Wideband+Audio+Technology+Licensing...-a072261882 |title=PictureTel Announces New Siren Wideband Audio Technology Licensing Program |date=2001-03-26 |accessdate=2009-09-10}}</ref> There are three Siren codecs: Siren 7, Siren 14 and Siren 22.
'''Siren''' is a family of patented, transform-based, [[wideband audio|wideband]] [[audio coding formats]] and their [[audio codec]] implementations developed and licensed by [[PictureTel Corp.|PictureTel Corporation]] (acquired by [[Polycom]], Inc. in 2001).<ref name="picturetel">{{cite web |author=Business Wire |publisher=thefreelibrary.com |url=http://www.thefreelibrary.com/PictureTel+Announces+New+Siren+Wideband+Audio+Technology+Licensing...-a072261882 |title=PictureTel Announces New Siren Wideband Audio Technology Licensing Program |date=2001-03-26 |access-date=2009-09-10 |archive-date=2012-10-13 |archive-url=https://web.archive.org/web/20121013184749/http://www.thefreelibrary.com/PictureTel+Announces+New+Siren+Wideband+Audio+Technology+Licensing...-a072261882 |url-status=dead }}</ref> There are three Siren codecs: Siren 7, Siren 14 and Siren 22.


== Editions ==
'''Siren 7''' (or Siren7 or only Siren) provides 7 kHz audio, [[bit rate]]s 16, 24, 32 kbps and [[sampling frequency]] 16 kHz. Siren is derived from PictureTel's PT716plus algorithm.<ref name="picturetel-intel">{{cite web |author=Business Wire |publisher=thefreelibrary.com |url=http://www.thefreelibrary.com/PictureTel+Licenses+Audio+Technology+Suite+to+Intel.-a063558475 |title=PictureTel Licenses Audio Technology Suite to Intel |date=2000-07-19 |accessdate=2009-09-10}}</ref> [[ITU-T]] [[G.722.1]] recommendation approved in 1999 is based on Siren 7, but provides only bit rates 24 kbps and 32 kbps.<ref>(2008-08-05) [http://www.reuters.com/article/pressRelease/idUS135735+05-Aug-2008+MW20080805 Polycom Enables Acceleration of HD Voice Adoption by Offering Royalty-Free Codec], Retrieved 2009-09-07</ref><ref name="g7221-faq">{{cite web |author= |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren_g7221/faq.html |title=Polycom Siren/G 722.1 FAQs |date= |accessdate=2009-09-07}}</ref> The algorithm of Siren 7 is identical to its successor, G.722.1, although the data formats are slightly different.
'''Siren 7''' (or Siren7 or simply Siren) provides 7&nbsp;kHz audio, [[bit rate]]s 16, 24, 32&nbsp;kbit/s and [[sampling frequency]] 16&nbsp;kHz. Siren is derived from PictureTel's PT716plus algorithm.<ref name="picturetel-intel">{{cite web |author=Business Wire |publisher=thefreelibrary.com |url=http://www.thefreelibrary.com/PictureTel+Licenses+Audio+Technology+Suite+to+Intel.-a063558475 |title=PictureTel Licenses Audio Technology Suite to Intel |date=2000-07-19 |access-date=2009-09-10 |archive-date=2012-10-13 |archive-url=https://web.archive.org/web/20121013184755/http://www.thefreelibrary.com/PictureTel+Licenses+Audio+Technology+Suite+to+Intel.-a063558475 |url-status=dead }}</ref> In 1999, [[ITU-T]] approved [[G.722.1]] recommendation, which is based on Siren 7 algorithm. It was approved after a four-year selection process involving extensive testing.<ref name="picturetel-intel" /> G.722.1 provides only bit rates 24 and 32&nbsp;kbit/s and does not support Siren 7's bit rate 16&nbsp;kbit/s.<ref>(2008-08-05) [https://www.reuters.com/article/pressRelease/idUS135735+05-Aug-2008+MW20080805 Polycom Enables Acceleration of HD Voice Adoption by Offering Royalty-Free Codec] {{Webarchive|url=https://archive.today/20130201102055/http://www.reuters.com/article/pressRelease/idUS135735+05-Aug-2008+MW20080805 |date=2013-02-01 }}, Retrieved 2009-09-07</ref><ref name="g7221-faq">{{cite web |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren_g7221/faq.html |title=Polycom Siren/G 722.1 FAQs |access-date=2009-09-07}}</ref> The algorithm of Siren 7 is identical to its successor, G.722.1, although the data formats are slightly different.


'''Siren 14''' (or Siren14) provides 14 kHz audio, bit rates 24, 32, 48 kbps for mono, 48, 64, 96 kbps for stereo and sampling frequency 32 kHz. Siren 14 supports stereo and mono audio. It offers 40 millisecond algorithmic delay, using 20 millisecond frame lengths. The mono version of Siren 14 became ITU-T G.722.1C (14 kHz, 24/32/48 kbps) in April 2005.<ref name="g7221c">Polycom, Inc. (2005-04-12) [http://findarticles.com/p/articles/mi_m0EIN/is_2005_April_12/ai_n13600182/ ITU Approves Polycom Siren14 as New International Standard], Retrieved 2009-09-07</ref><ref name="g7221c-polycom">{{cite web |author= |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren14_g7221c/index.html |title=Polycom Siren 14/G 722.1C |date= |accessdate=2009-09-07}}</ref><ref name="businesswire">{{cite web |author= |publisher=BusinessWire.com |url=http://www.businesswire.com/portal/site/home/permalink/?ndmViewId=news_view&newsId=20050412005325&newsLang=en |title=ITU Approves Polycom Siren14 as New International Standard |date=2005-04-12 |accessdate=2009-09-10}}</ref>
'''Siren 14''' (or Siren14) provides 14&nbsp;kHz audio, bit rates 24, 32, 48&nbsp;kbit/s for mono, 48, 64, 96&nbsp;kbit/s for stereo and sampling frequency 32&nbsp;kHz. Siren 14 supports stereo and mono audio. It offers 40 millisecond algorithmic delay, using 20 millisecond frame lengths. The mono version of Siren 14 became ITU-T G.722.1C (14&nbsp;kHz, 24/32/48&nbsp;kbit/s) in April 2005.<ref name="g7221c">Polycom, Inc. (2005-04-12) [http://findarticles.com/p/articles/mi_m0EIN/is_2005_April_12/ai_n13600182/ ITU Approves Polycom Siren14 as New International Standard], Retrieved 2009-09-07</ref><ref name="g7221c-polycom">{{cite web |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren14_g7221c/index.html |title=Polycom Siren 14/G 722.1C |access-date=2009-09-07}}</ref><ref name="businesswire">{{cite web |publisher=BusinessWire.com |url=http://www.businesswire.com/portal/site/home/permalink/?ndmViewId=news_view&newsId=20050412005325&newsLang=en |title=ITU Approves Polycom Siren14 as New International Standard |date=2005-04-12 |access-date=2009-09-10}}</ref> The algorithm is based on [[transform coding]] technology, using a [[Modified discrete cosine transform|modulated lapped transform]] (MLT),<ref>{{citation |url=http://www.polycom.com/global/documents/company/about_us/technology/siren14_g7221c/info_for_prospective_licensees.pdf |title=Siren 14 information for Prospective Licensees |access-date=2010-06-08}}</ref> a type of [[discrete cosine transform]] (DCT)<ref>{{cite book |last1=Hersent |first1=Olivier |last2=Petit |first2=Jean-Pierre |last3=Gurle |first3=David |title=Beyond VoIP Protocols: Understanding Voice Technology and Networking Techniques for IP Telephony |date=2005 |publisher=[[John Wiley & Sons]] |isbn=9780470023631 |page=55 |url=https://books.google.com/books?id=SMvNToRs-DgC&pg=PA55}}</ref> or [[modified discrete cosine transform]] (MDCT).<ref>{{cite book |last1=Britanak |first1=Vladimir |last2=Rao |first2=K. R. |author2-link=K. R. Rao |title=Cosine-/Sine-Modulated Filter Banks: General Properties, Fast Algorithms and Integer Approximations |date=2017 |publisher=Springer |isbn=9783319610801 |page=478 |url=https://books.google.com/books?id=cZ4vDwAAQBAJ&pg=PA478}}</ref>


'''Siren 22''' (or Siren22) provides 22 kHz audio, sampling frequency 48 kHz, bit rates 64, 96, 128 kbps stereo and 32, 48, 64 kbps mono. Siren 22 offers 40 millisecond algorithmic delay using 20 millisecond frame lengths. In May 2008, ITU-T approved the new [[G.719]] full-band codec which is based on Polycom Siren 22 audio technology and Ericsson’s advanced audio techniques.<ref name="siren22-polycom">{{cite web |author= |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren22/index.html |title=Polycom Siren 22 |date= |accessdate=2009-09-07}}</ref><ref name="g719-polycom">{{cite web |author= |publisher=Polycom, Inc. |url=http://www.polycom.com/global/documents/whitepapers/g719-the-first-itut-standard-for-full-band-audio.pdf |title=G.719: The First ITU-T Standard for Full-Band Audio |date=2009-04 |accessdate=2009-09-07}}</ref>
'''Siren 22''' (or Siren22) provides 22&nbsp;kHz audio, sampling frequency 48&nbsp;kHz, bit rates 64, 96, 128&nbsp;kbit/s stereo and 32, 48, 64&nbsp;kbit/s mono. Siren 22 offers 40 millisecond algorithmic delay using 20 millisecond frame lengths. In May 2008, ITU-T approved the new [[G.719]] full-band codec which is based on Polycom Siren 22 audio technology and Ericsson's advanced audio techniques.<ref name="siren22-polycom">{{cite web |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren22/index.html |title=Polycom Siren 22 |access-date=2009-09-07}}</ref><ref name="g719-polycom">{{cite web |publisher=Polycom, Inc. |url=http://www.polycom.com/global/documents/whitepapers/g719-the-first-itut-standard-for-full-band-audio.pdf |title=G.719: The First ITU-T Standard for Full-Band Audio |date=April 2009 |access-date=2009-09-07}}</ref>


== Software support ==
== Software support ==
Siren 7 is commonly used in videoconferencing systems and is also part of [[Microsoft Office Communicator]] when using A/V conferencing. [[Microsoft Office Communications Server]] uses Siren 7 during audio conferencing. With the default Officed Communicator client, point to point audio is by default performed using Microsoft's proprietary code [[RTAudio]]. When a call is promoted into an audio conference (any time 3 or more participants have joined), the codec is switched on the fly to Siren. This is done for performance reasons.
Siren 7 is commonly used in videoconferencing systems and is also part of [[Microsoft Office Communicator]] when using A/V conferencing. [[Microsoft Office Communications Server]] uses Siren 7 during audio conferencing. With the default Office Communicator client, point to point audio is by default performed using Microsoft's proprietary codec [[RTAudio]]. When a call is promoted into an audio conference (any time 3 or more participants have joined), the codec is switched on the fly to Siren. This is done for performance reasons. Note that even if the conference is reduced to below 3 participants, OCS does not demote the conference to be point-to-point; it remains an A/V conference until the conference is terminated.


In Windows XP, Siren 7 codec is implemented in <tt>%systemroot%\system32\SIRENACM.DLL</tt>. It is used by MSN Messenger for sending and receiving voice clips and also as one of the available codecs for the 'Computer Call' feature.<ref name="multimediawiki">{{cite web |author= |publisher=MultimediaWiki |url=http://wiki.multimedia.cx/index.php?title=Siren |title=Siren |date= |accessdate=2009-09-07}}</ref><ref name="mplayer">{{cite web |author= |publisher=MultimediaWiki |url=http://www.mplayerhq.hu/DOCS/codecs-status.html#ac |title=MPlayer - Status of codecs support |date= |accessdate=2009-09-07}}</ref><ref name="winxp">{{cite web |author=Microsoft |publisher=Microsoft |url=http://msdn.microsoft.com/en-us/library/ms997607.aspx |title=Media Support in the Microsoft Windows Real-Time Communications Platform |date=2001-11 |accessdate=2009-09-07}}</ref>
In Windows XP and later versions of Windows, the Siren 7 codec is implemented in {{mono|%systemroot%\system32\SIRENACM.DLL}}. It is used by MSN Messenger and Live Messenger for sending and receiving voice clips and also as one of the available codecs for the 'Computer Call' feature.<ref name="multimediawiki">{{cite web |publisher=MultimediaWiki |url=http://wiki.multimedia.cx/index.php?title=Siren |title=Siren |access-date=2009-09-07}}</ref><ref name="mplayer">{{cite web |publisher=MultimediaWiki |url=http://www.mplayerhq.hu/DOCS/codecs-status.html#ac |title=MPlayer - Status of codecs support |access-date=2009-09-07}}</ref><ref name="winxp">{{cite web |author=Microsoft |publisher=Microsoft |url=http://msdn.microsoft.com/en-us/library/ms997607.aspx |title=Media Support in the Microsoft Windows Real-Time Communications Platform |date=November 2001 |access-date=2009-09-07}}</ref>


[[FreeSWITCH]] communication open source software can do transcoding, conferencing and bridging of Siren 7/G.722.1 and Siren 14/G.722.1C audio formats.<ref name="freeswitch">{{cite web |author= |publisher=FreeSWITCH |url=http://www.freeswitch.org/node/153 |title=FreeSWITCH First to Support Polycom's 32khz HD-Audio. |date=2008-12-15 |accessdate=2009-09-07}}</ref><ref name="libg7221">{{cite web |author= |publisher=FreeSWITCH |url=http://svn.freeswitch.org/svn/freeswitch/trunk/libs/libg722_1/COPYING |title=libg722_1 - COPYING |date= |accessdate=2009-09-07}}</ref><ref name="libg7221-readme">{{cite web |author= |publisher=FreeSWITCH |url=http://svn.freeswitch.org/svn/freeswitch/trunk/libs/libg722_1/README |title=libg722_1 - README |date= |accessdate=2009-09-07}}</ref>
[[FreeSWITCH]] communication open source software can do transcoding, conferencing and bridging of Siren 7/G.722.1 and Siren 14/G.722.1C audio formats.<ref name="freeswitch">{{cite web |publisher=FreeSWITCH |url=http://www.freeswitch.org/node/153 |title=FreeSWITCH First to Support Polycom's 32khz HD-Audio. |date=2008-12-15 |access-date=2009-09-07 |archive-url=https://web.archive.org/web/20090508170812/http://freeswitch.org/node/153 |archive-date=2009-05-08 |url-status=dead }}</ref><ref name="libg7221">{{cite web |publisher=FreeSWITCH |url=https://stash.freeswitch.org/projects/FS/repos/freeswitch/browse/libs/libg722_1/COPYING |title=libg722_1 - COPYING |access-date=2014-07-19}}</ref><ref name="libg7221-readme">{{cite web |publisher=FreeSWITCH |url=https://stash.freeswitch.org/projects/FS/repos/freeswitch/browse/libs/libg722_1/README |title=libg722_1 - README |access-date=2014-07-19}}</ref>


[[aMSN]], an open source Windows Live Messenger clone uses open source library "libmsn", which includes "libsiren" for Siren audio compression and decompression.<ref name="libmsn">{{cite web |author= |publisher=Libmsn project at Sourceforge.net |url=http://sourceforge.net/projects/libmsn/ |title=Libmsn - is a reusable, open-source, fully documented library for connecting to Microsoft's MSN Messenger service. |date=2009 |accessdate=2009-09-07}}</ref><ref name="kakaroto">KaKaRoTo (2008-02-12) [http://pidgin.im/pipermail/openim/2008-February/000045.html MSN Protocol documentation], Pidgin.im mailinglist, Retrieved 2009-09-08</ref><ref name="libmsn-svn">{{cite web |author= |publisher=Libmsn project at Sourceforge.net |url=http://libmsn.svn.sourceforge.net/viewvc/libmsn/trunk/msn/libsiren/ |title=SCM Repositories - libmsn - libsiren |date=2009 |accessdate=2009-09-07}}</ref> The libsiren library is also used in msn-pecan project, which provides plug-in for [[Pidgin (software)|Pidgin]] and [[Adium]] instant messaging clients.<ref name="msn-pecan0018">{{cite web |author= |publisher=msn-pecan |url=http://felipec.wordpress.com/category/development/page/2/ |title=msn-pecan 0.0.18 released, now with voice clips support |date=2009-02-16 |accessdate=2009-09-07}}</ref><ref name="msn-pecan">{{cite web |author= |publisher=msn-pecan |url=http://code.google.com/p/msn-pecan/ |title=msn-pecan |date= |accessdate=2009-09-07}}</ref><ref name="kakaroto" />
[[aMSN]], an open source Windows Live Messenger clone uses for Siren audio compression and decompression the "libsiren" library, an open source implementation of the codec, written by aMSN developer Youness Alaoui (KaKaRoTo) .<ref name="kakaroto">KaKaRoTo (2008-02-12) [http://pidgin.im/pipermail/openim/2008-February/000045.html MSN Protocol documentation] {{Webarchive|url=https://web.archive.org/web/20130524081438/http://pidgin.im/pipermail/openim/2008-February/000045.html |date=2013-05-24 }}, Pidgin.im mailinglist, Retrieved 2009-09-08</ref> The libsiren library has also been copied into libmsn and into the msn-pecan project, which provides plug-in for [[Pidgin (software)|Pidgin]] and [[Adium]] instant messaging clients.<ref name="kakaroto" /><ref name="msn-pecan0018">{{cite web |publisher=msn-pecan |url=http://felipec.wordpress.com/2009/02/16/msn-pecan-0018-released-now-with-voice-clips-support/ |title=msn-pecan 0.0.18 released, now with voice clips support |date=2009-02-16 |access-date=2014-07-19}}</ref><ref name="msn-pecan">{{cite web |publisher=msn-pecan |url=http://code.google.com/p/msn-pecan/ |title=msn-pecan |access-date=2009-09-07}}</ref><ref name="libmsn">{{cite web |publisher=Libmsn project at Sourceforge.net |url=http://sourceforge.net/projects/libmsn/ |title=Libmsn - is a reusable, open-source, fully documented library for connecting to Microsoft's MSN Messenger service. |year=2009 |access-date=2009-09-07}}</ref><ref name="libmsn-svn">{{cite web |publisher=Libmsn project at Sourceforge.net |url=http://libmsn.svn.sourceforge.net/viewvc/libmsn/trunk/msn/libsiren/ |title=SCM Repositories - libmsn - libsiren |year=2009 |access-date=2009-09-07}}</ref>


==Licensing==
==Licensing==


Usage of Siren 7 and Siren 14 compressions require the licencing of patents from Polycom, in most countries. A [[royalty free]] licence for Siren 7 and Siren 14 is available from Polycom if certain fairly basic conditions are met.<ref name="libg7221" /><ref name="celt-comparison">{{cite web |author=Xiph.Org Foundation |publisher=Xiph.Org Foundation |url=http://www.celt-codec.org/comparison/ |title=CELT - Codec Feature Comparison |date=2009 |accessdate=2009-09-07}}</ref><ref name="speex-comparison">{{cite web |author=Xiph.Org Foundation |publisher=Xiph.Org Foundation |url=http://www.speex.org/comparison/ |title=Speex - Codec Quality Comparison |date=2006 |accessdate=2009-09-07}}</ref><ref name="licensing">{{cite web |author=Polycom, Inc. |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren_g7221/license_schedule.html |title=Siren7/Siren14/G.719 License info |date= |accessdate=2009-09-07}}</ref><ref name="g7221-faq" /><ref name="g7221c-licensing">{{cite web |author=Polycom, Inc. |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren14_g7221c/faq.html#license_q3 |title=Polycom Siren 14/G 722.1C FAQs - What are the terms on the free license? |date= |accessdate=2009-09-07}}</ref><ref name="polycom-free-hd-voice">{{cite web |author=Greg Galitzine |publisher=TMCnet.com |url=http://hdvoice.tmcnet.com/topics/wideband-audio/articles/36272-polycom-cto-discusses-siren-7-hd-voice-codec.htm |title=Polycom CTO Discusses Siren 7 HD Voice Codec |date=2008-08-06 |accessdate=2009-09-07}}</ref>
Usage of Siren 7 and Siren 14 audio coding formats require the licensing of patents from Polycom, in most countries. A [[royalty free]] licence for Siren 7 and Siren 14 is available from Polycom if certain fairly basic conditions are met.<ref name="g7221-faq" /><ref name="libg7221" /><ref name="celt-comparison">{{cite web |author=Xiph.Org Foundation |publisher=Xiph.Org Foundation |url=http://www.celt-codec.org/comparison/ |title=CELT - Codec Feature Comparison |year=2009 |access-date=2009-09-07 |archive-date=2009-09-12 |archive-url=https://web.archive.org/web/20090912184544/http://www.celt-codec.org/comparison/ |url-status=dead }}</ref><ref name="speex-comparison">{{cite web |author=Xiph.Org Foundation |publisher=Xiph.Org Foundation |url=http://www.speex.org/comparison/ |title=Speex - Codec Quality Comparison |year=2006 |access-date=2009-09-07}}</ref><ref name="licensing">{{cite web |author=Polycom, Inc. |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren_g7221/license_schedule.html |title=Siren7/Siren14/G.719 License info |access-date=2009-09-07}}</ref><ref name="g7221c-licensing">{{cite web |author=Polycom, Inc. |publisher=Polycom, Inc. |url=http://www.polycom.com/company/about_us/technology/siren14_g7221c/faq.html#license_q3 |title=Polycom Siren 14/G 722.1C FAQs - What are the terms on the free license? |access-date=2009-09-07}}</ref><ref name="polycom-free-hd-voice">{{cite web |author=Greg Galitzine |publisher=TMCnet.com |url=http://technews.tmcnet.com/reseller/topics/wideband-audio/articles/36272-polycom-cto-discusses-siren-7-hd-voice-codec.htm |title=Polycom CTO Discusses Siren 7 HD Voice Codec |date=2008-08-06 |access-date=2014-07-19}}</ref>


Usage of Siren 22 also require the licencing of patents from Polycom.<ref name="licensing" />
Usage of Siren 22 also requires the licensing of patents from Polycom.<ref name="licensing" />


==See also==
==See also==
* [[Comparison of audio codecs]]
* [[Comparison of audio coding formats]]
* [[G.722.1]]
* [[G.722.1]]


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* [http://www.polycom.com/company/about_us/technology/siren22/index.html Polycom Siren 22]
* [http://www.polycom.com/company/about_us/technology/siren22/index.html Polycom Siren 22]


{{Compression formats}}
{{tech-stub}}

[[Category: Audio codecs]]
[[Category:Audio codecs]]

Latest revision as of 22:07, 25 April 2024

Siren is a family of patented, transform-based, wideband audio coding formats and their audio codec implementations developed and licensed by PictureTel Corporation (acquired by Polycom, Inc. in 2001).[1] There are three Siren codecs: Siren 7, Siren 14 and Siren 22.

Editions

[edit]

Siren 7 (or Siren7 or simply Siren) provides 7 kHz audio, bit rates 16, 24, 32 kbit/s and sampling frequency 16 kHz. Siren is derived from PictureTel's PT716plus algorithm.[2] In 1999, ITU-T approved G.722.1 recommendation, which is based on Siren 7 algorithm. It was approved after a four-year selection process involving extensive testing.[2] G.722.1 provides only bit rates 24 and 32 kbit/s and does not support Siren 7's bit rate 16 kbit/s.[3][4] The algorithm of Siren 7 is identical to its successor, G.722.1, although the data formats are slightly different.

Siren 14 (or Siren14) provides 14 kHz audio, bit rates 24, 32, 48 kbit/s for mono, 48, 64, 96 kbit/s for stereo and sampling frequency 32 kHz. Siren 14 supports stereo and mono audio. It offers 40 millisecond algorithmic delay, using 20 millisecond frame lengths. The mono version of Siren 14 became ITU-T G.722.1C (14 kHz, 24/32/48 kbit/s) in April 2005.[5][6][7] The algorithm is based on transform coding technology, using a modulated lapped transform (MLT),[8] a type of discrete cosine transform (DCT)[9] or modified discrete cosine transform (MDCT).[10]

Siren 22 (or Siren22) provides 22 kHz audio, sampling frequency 48 kHz, bit rates 64, 96, 128 kbit/s stereo and 32, 48, 64 kbit/s mono. Siren 22 offers 40 millisecond algorithmic delay using 20 millisecond frame lengths. In May 2008, ITU-T approved the new G.719 full-band codec which is based on Polycom Siren 22 audio technology and Ericsson's advanced audio techniques.[11][12]

Software support

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Siren 7 is commonly used in videoconferencing systems and is also part of Microsoft Office Communicator when using A/V conferencing. Microsoft Office Communications Server uses Siren 7 during audio conferencing. With the default Office Communicator client, point to point audio is by default performed using Microsoft's proprietary codec RTAudio. When a call is promoted into an audio conference (any time 3 or more participants have joined), the codec is switched on the fly to Siren. This is done for performance reasons. Note that even if the conference is reduced to below 3 participants, OCS does not demote the conference to be point-to-point; it remains an A/V conference until the conference is terminated.

In Windows XP and later versions of Windows, the Siren 7 codec is implemented in %systemroot%\system32\SIRENACM.DLL. It is used by MSN Messenger and Live Messenger for sending and receiving voice clips and also as one of the available codecs for the 'Computer Call' feature.[13][14][15]

FreeSWITCH communication open source software can do transcoding, conferencing and bridging of Siren 7/G.722.1 and Siren 14/G.722.1C audio formats.[16][17][18]

aMSN, an open source Windows Live Messenger clone uses for Siren audio compression and decompression the "libsiren" library, an open source implementation of the codec, written by aMSN developer Youness Alaoui (KaKaRoTo) .[19] The libsiren library has also been copied into libmsn and into the msn-pecan project, which provides plug-in for Pidgin and Adium instant messaging clients.[19][20][21][22][23]

Licensing

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Usage of Siren 7 and Siren 14 audio coding formats require the licensing of patents from Polycom, in most countries. A royalty free licence for Siren 7 and Siren 14 is available from Polycom if certain fairly basic conditions are met.[4][17][24][25][26][27][28]

Usage of Siren 22 also requires the licensing of patents from Polycom.[26]

See also

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References

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  1. ^ Business Wire (2001-03-26). "PictureTel Announces New Siren Wideband Audio Technology Licensing Program". thefreelibrary.com. Archived from the original on 2012-10-13. Retrieved 2009-09-10. {{cite web}}: |author= has generic name (help)
  2. ^ a b Business Wire (2000-07-19). "PictureTel Licenses Audio Technology Suite to Intel". thefreelibrary.com. Archived from the original on 2012-10-13. Retrieved 2009-09-10. {{cite web}}: |author= has generic name (help)
  3. ^ (2008-08-05) Polycom Enables Acceleration of HD Voice Adoption by Offering Royalty-Free Codec Archived 2013-02-01 at archive.today, Retrieved 2009-09-07
  4. ^ a b "Polycom Siren/G 722.1 FAQs". Polycom, Inc. Retrieved 2009-09-07.
  5. ^ Polycom, Inc. (2005-04-12) ITU Approves Polycom Siren14 as New International Standard, Retrieved 2009-09-07
  6. ^ "Polycom Siren 14/G 722.1C". Polycom, Inc. Retrieved 2009-09-07.
  7. ^ "ITU Approves Polycom Siren14 as New International Standard". BusinessWire.com. 2005-04-12. Retrieved 2009-09-10.
  8. ^ Siren 14 information for Prospective Licensees (PDF), retrieved 2010-06-08
  9. ^ Hersent, Olivier; Petit, Jean-Pierre; Gurle, David (2005). Beyond VoIP Protocols: Understanding Voice Technology and Networking Techniques for IP Telephony. John Wiley & Sons. p. 55. ISBN 9780470023631.
  10. ^ Britanak, Vladimir; Rao, K. R. (2017). Cosine-/Sine-Modulated Filter Banks: General Properties, Fast Algorithms and Integer Approximations. Springer. p. 478. ISBN 9783319610801.
  11. ^ "Polycom Siren 22". Polycom, Inc. Retrieved 2009-09-07.
  12. ^ "G.719: The First ITU-T Standard for Full-Band Audio" (PDF). Polycom, Inc. April 2009. Retrieved 2009-09-07.
  13. ^ "Siren". MultimediaWiki. Retrieved 2009-09-07.
  14. ^ "MPlayer - Status of codecs support". MultimediaWiki. Retrieved 2009-09-07.
  15. ^ Microsoft (November 2001). "Media Support in the Microsoft Windows Real-Time Communications Platform". Microsoft. Retrieved 2009-09-07.
  16. ^ "FreeSWITCH First to Support Polycom's 32khz HD-Audio". FreeSWITCH. 2008-12-15. Archived from the original on 2009-05-08. Retrieved 2009-09-07.
  17. ^ a b "libg722_1 - COPYING". FreeSWITCH. Retrieved 2014-07-19.
  18. ^ "libg722_1 - README". FreeSWITCH. Retrieved 2014-07-19.
  19. ^ a b KaKaRoTo (2008-02-12) MSN Protocol documentation Archived 2013-05-24 at the Wayback Machine, Pidgin.im mailinglist, Retrieved 2009-09-08
  20. ^ "msn-pecan 0.0.18 released, now with voice clips support". msn-pecan. 2009-02-16. Retrieved 2014-07-19.
  21. ^ "msn-pecan". msn-pecan. Retrieved 2009-09-07.
  22. ^ "Libmsn - is a reusable, open-source, fully documented library for connecting to Microsoft's MSN Messenger service". Libmsn project at Sourceforge.net. 2009. Retrieved 2009-09-07.
  23. ^ "SCM Repositories - libmsn - libsiren". Libmsn project at Sourceforge.net. 2009. Retrieved 2009-09-07.
  24. ^ Xiph.Org Foundation (2009). "CELT - Codec Feature Comparison". Xiph.Org Foundation. Archived from the original on 2009-09-12. Retrieved 2009-09-07.
  25. ^ Xiph.Org Foundation (2006). "Speex - Codec Quality Comparison". Xiph.Org Foundation. Retrieved 2009-09-07.
  26. ^ a b Polycom, Inc. "Siren7/Siren14/G.719 License info". Polycom, Inc. Retrieved 2009-09-07.
  27. ^ Polycom, Inc. "Polycom Siren 14/G 722.1C FAQs - What are the terms on the free license?". Polycom, Inc. Retrieved 2009-09-07.
  28. ^ Greg Galitzine (2008-08-06). "Polycom CTO Discusses Siren 7 HD Voice Codec". TMCnet.com. Retrieved 2014-07-19.
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