Editing Adaptive Multi-Rate audio codec (section)

{{Short description|Audio compression format optimized for speech coding}}
{{Infobox file format
| name                   = Adaptive Multi-Rate (AMR)
| icon =
| logo =
| caption =
| extension              = .amr, .3ga<!-- Samsung Galaxy phones use .3ga -->
| mime                   = audio/amr, audio/3gpp, audio/3gpp2
| type code =
| uniform type =
| magic =
| owner =
| released               = {{Start date|1999|06|23|df=yes}}<!-- {{Start date|YYYY|mm|dd|df=yes}} --><ref name="3gpp-26090">{{cite web |url=http://www.3gpp.org/ftp/Specs/html-info/26090.htm | title=3GPP TS 26.090 - Mandatory Speech Codec speech processing functions; Adaptive Multi-Rate (AMR) speech codec; Transcoding functions |publisher=3GPP |access-date=2010-07-21}}</ref><ref name="3gpp-26071">{{cite web |url=http://www.3gpp.org/ftp/Specs/html-info/26071.htm | title=3GPP TS 26.071 - Mandatory speech CODEC speech processing functions; AMR speech Codec; General description |publisher=3GPP |access-date=2010-07-21}}</ref>
| latest release version = 14.0.0
| latest release date    = {{Start date and age|2017|03|17|df=yes}}<!-- {{Start date and age|YYYY|mm|dd|df=yes}} -->
| type                   = [[Lossy compression|Lossy]] [[Audio file format|audio]]
| container for =
| contained by =
| extended from =
| extended to =
| standard =
| open                   = Yes
| free                   = No
| url                    = 
}}

The '''Adaptive Multi-Rate''' ('''AMR''', '''AMR-NB''' or '''GSM-AMR''') '''audio codec''' is an [[audio compression format]] optimized for [[speech coding]]. AMR is a multi-rate [[narrowband]] speech [[codec]] that encodes narrowband (200–3400&nbsp;Hz) signals at variable bit rates ranging from 4.75 to 12.2&nbsp;kbit/s with toll quality<ref>{{cite web |title=What's toll-quality voice? |url=https://www.itworld.com/article/2783105/what-s-toll-quality-voice-.html |website=ITworld |date=13 December 2000 |access-date=26 July 2019}}</ref> speech starting at 7.4&nbsp;kbit/s.<ref>[http://tools.ietf.org/html/rfc4867#page-5 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>

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>