AMR - Adaptive Multi-Rate Codec File

What is a AMR file

AMR is a compression format to optimize speech coding consisting of multi-rate narrowband speech codecs. AMR files can be recorded with mobile phones. To accomplish random access or synchronization of audio and video the 3GPP format can be utilized. AMR uses ACELP, DTX, VAD, and CNG to code the 160 20-millisecond samples contained in each frame. AMR files are used for voice recording though the format is usually converted into other files for use and distribution.

AMR is capable of encoding 200-3400 Hz signals from 4.75 to 12.2 kbit/s with quality starting at 7.4 kbit/s. Adopted in 1999 by 3GPP, this method is used by GSM and UMTS, using link adaptation to choose from the 8 different bit rates. AMR optimizes link adaptation with the best codec available in order to be utilized with radio channel and capacity requirements. This is only possible if a good connection is provided to prevent the loss of the audio's quality.

Here's a small, but not exhaustive list of programs that can open AMR documents:

  • Audacity
  • Android
  • Open Source software
  • AMR Player
  • QuickTime
  • Real Player
  • VLS Media Player
  • Apple iPhone
About
Extension AMR
MIME type audio/amr, audio/3gpp, audio/3gpp2
Useful links
Example Files
example.amr
(55.16 KiB)