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The '''Adaptive Multi-Rate''' ('''AMR''', '''AMR-NB''' or '''GSM-AMR''') '''audio codec''' is an [[audio compression format]] optimized for [[speech coding]]. AMR
AMR was adopted as the standard speech [[codec]] by [[3GPP]] in October 1999 and is now widely used in [[GSM]]<ref>{{cite web | url=http://www.eetimes.com/electronics-news/4139026/Sorting-Through-GSM-Codecs-A-Tutorial | title=Sorting Through GSM Codecs: A Tutorial | date=11 July 2003 }}</ref> and [[UMTS]]. It uses [[link adaptation]] to select from one of eight different bit rates based on link conditions.
AMR is also a file format for storing spoken audio using the AMR codec. Many modern mobile telephone handsets can store short audio recordings in the AMR format, and both [[Free software|free]] and proprietary programs exist (see [[#Software support|Software support]]) to convert between this and other formats, although AMR is a speech format and is unlikely to give ideal results for other audio. The common [[filename extension]] is <code>.amr</code>. There also exists another storage format for AMR that is suitable for applications with more advanced demands on the storage format, like random access or synchronization with video. This format is the 3GPP-specified [[3GP]] [[container format (digital)|container format]] based on ISO base media file format.<ref>[http://tools.ietf.org/html/rfc4867#page-35 RFC 4867 - RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs] Page 35</ref>
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== Licensing and patent issues ==
AMR codecs incorporate several [[patent]]s of [[Nokia]], [[Ericsson]], [[Nippon Telegraph and Telephone|NTT]] and VoiceAge,<ref name="voiceage-amr_licterms">{{cite web |author=VoiceAge Corporation |publisher=VoiceAge Corporation |url=http://www.voiceage.com/amr_licterms.php |title=AMR Licensing Terms |date=2007-10-14 |access-date=2009-09-12 |archive-url=https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php |archive-date=2007-10-14}}</ref><ref name="voiceage-amr_licterms2">{{cite web|author=VoiceAge Corporation |publisher=VoiceAge Corporation |url=http://www.voiceage.com/amr_licterms.php |title=AMR Licensing Terms |date=June 2007 |access-date=2009-09-12 |url-status=dead |archive-url=https://web.archive.org/web/20071014162046/http://www.voiceage.com/amr_licterms.php |archive-date=2007-10-14 }}</ref> the last one being the ''License Administrator'' for the AMR [[patent pool]]s. VoiceAge also accepts submission of patents for determination of their possible essentiality to these standards
The initial fee for professional content creation tools and "real-time channel" products is US$6,500.{{When|date=November 2015}} The minimum annual royalty is $10,000, which, in the first year, excludes the initial fee. Per-channel license fees fall from $0.99 to $0.50 with volume, up to a maximum of $2 million annually.<ref name="voiceage-amr_licterms"/><ref name="voiceage-amr_licterms2"/>
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* [https://web.archive.org/web/20070630180010/http://www.3gpp.org/legal/legal.htm 3GPP legal issues]
* [https://web.archive.org/web/20070630180057/http://www.3gpp.org/faq/faq_2005_2.htm#A3.1 The 3G Patent Platform and its licensing policy]
* [http://www.penguin.cz/~utx/amr AMR Codecs as Shared Libraries] {{Webarchive|url=https://web.archive.org/web/20210411005805/http://www.penguin.cz/~utx/amr |date=2021-04-11 }} — legal notices for usage of amrnb and amrwb libraries based on the reference implementation
== Software support ==
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* [[FFmpeg]] with OpenCORE AMR libraries<ref name="ffmpeg-amr">[http://www.ffmpeg.org/general.html FFmpeg General Documentation - AMR external library], Retrieved on 2009-07-08</ref>
* [[Android (operating system)|Android]]<ref name="android-amr">[http://android.git.kernel.org/?p=platform/external/opencore.git;a=tree;f=codecs_v2/audio/gsm_amr;hb=HEAD Android AMR codecs], Retrieved on 2009-07-08 {{webarchive|url=https://web.archive.org/web/20090218232855/http://android.git.kernel.org/?p=platform%2Fexternal%2Fopencore.git%3Ba%3Dtree%3Bf%3Dcodecs_v2%2Faudio%2Fgsm_amr%3Bhb%3DHEAD |date=February 18, 2009 }}</ref> Used for voice recorder.
* [http://www.penguin.cz/~utx/amr AMR Codecs as Shared Libraries] {{Webarchive|url=https://web.archive.org/web/20210411005805/http://www.penguin.cz/~utx/amr |date=2021-04-11 }}{{snd}}amrnb and amrwb libraries development site. These libraries are based on the reference implementation and were created to prevent embedding of possibly patented source code into many open source projects.
* Open source software to convert the .amr format: [
* [http://www.amrplayer.com/ AMR Player] is freeware to play AMR audio files, and can convert AMR from/to MP3/WAV audio format.
* [https://web.archive.org/web/20120422173730/http://www.developer.nokia.com/info/sw.nokia.com/id/d1c17a7f-1231-4385-8c17-04f28f4f2d8e/Nokia_Multimedia_Converter_2.0.html Nokia Multimedia Converter 2.0 ] can convert (create) samples, one can use Nokia's conversion tool to create both .amr and .awb files. It works in Windows 7 as well if the setup is run in XP compatibility mode.
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