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 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 codec by 3GPP in October 1999 and is now widely used in GSM 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 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 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 based on ISO base media file format.

Usage

The frames contain 160 samples and are 20 milliseconds long. the last one being the License Administrator for the AMR patent pools. 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. 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.

  • Audacity (beta version 1.3) via the FFmpeg integration libraries (both input and output format)
  • FFmpeg with OpenCORE AMR libraries
  • Android Used for voice recorder.
  • AMR Codecs as Shared Libraries 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: RetroCode, Amr2Wav, both are in an early developmental stage
  • AMR Player is freeware to play AMR audio files, and can convert AMR from/to MP3/WAV audio format.
  • 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.
  • MPlayer (SMPlayer, <abbr title="Konqueror Media Player">KMPlayer</abbr>)
  • Parole Media Player 0.8.1 (in Ubuntu 16.04)
  • QuickTime Player and multimedia framework
  • RealPlayer version 11 and later
  • VLC media player version 1.1.0 and later (input format only, not output format)
  • ffdshow
  • Apple iPhone (can play back AMR files)
  • iOS & macOS (iMessage)
  • BlackBerry smartphones (used for voice recorder file format, while BlackBerry 10 cannot play AMR format)
  • K-Lite Codec Pack
  • Media Player Classic Home Cinema, around 1.7.1
  • foobar2000 with the component foo_input_amr

See also

  • Adaptive Multi-Rate Wideband (AMR-WB)
  • Extended Adaptive Multi-Rate – Wideband (AMR-WB+)
  • Half Rate
  • Full Rate
  • Enhanced Full Rate (EFR)
  • Sampling rate
  • IS-641
  • 3GP
  • Comparison of audio coding formats
  • RTP audio video profile

References

  • 3GPP TS 26.090Mandatory Speech Codec speech processing functions; Adaptive Multi-Rate (AMR) speech codec; Transcoding functions
  • 3GPP TS 26.071Mandatory Speech Codec speech processing functions; AMR Speech Codec; General Description
  • 3GPP codecs specifications; 3G and beyond / GSM, 26 series
  • RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs
  • The Codecs Parameter for "Bucket" Media Types