Adaptive Multi-Rate Codec
AMR is also called an adaptive multi-rate audio codec. The main purpose of designing an audio compression format was to optimize speech coding. It was initially released on the 23rd of June 1999. It uses audio file format and audio compression formats. It is also a file format for storing spoken audio files in AMR codec. AMR speech contact concepts of the multi-rate narrow band which signals at variable bit rates ranging from 4.75 to 12.2 kbit/s.