Adaptive Multi-Rate audio codec

The Adaptive Multi-Rate (AMR, AMR-NB or GSM-AMR) audio codec is an <a href="/facts/Audio_compression_format/qHAhppfD">audio compression format</a> optimized for <a href="/facts/Speech_coding/xs5gvMXq">speech coding</a>. AMR is a multi-rate <a href="/facts/Narrowband/76nBsRml">narrowband</a> speech <a href="/facts/Codec/C7b7Am8t">codec</a> that encodes narrowband (200–3400 Hz) signals at variable bit rates ranging from 4.75 to 12.2 kbit/s with toll quality speech starting at 7.4 kbit/s.
AMR was adopted as the standard speech <a href="/facts/Codec/C7b7Am8t">codec</a> by <a href="/facts/3GPP/TBrQYKFF">3GPP</a> in October 1999 and is now widely used in <a href="/facts/GSM/Sw8QYaLE">GSM</a> and <a href="/facts/UMTS/lhy2RrMw">UMTS</a>. It uses <a href="/facts/Link_adaptation/vegwIxN8">link adaptation</a> 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 <a href="/facts/Free_software/IaoVtJXn">free</a> and proprietary programs exist (see 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 <a href="/facts/Filename_extension/cJgfAym4">filename extension</a> is .amr. 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 <a href="/facts/3GP/EYCqToLu">3GP</a> <a href="/facts/Container_format_(digital)/mSfwwdSA">container format</a> based on ISO base media file format.

Adaptive Multi-Rate audio codec open-in-new

Adaptive Multi-Rate audio codec