AMR is a file format for storing spoken audio using the AMR codec. There are lots of modern cell phone handsets which will allow you to store short recordings in the AMR format. Both open source and commercial programs exist to convert between this and other formats such as MP3, although it should be remembered that AMR is a speech format and is unlikely to give ideal results for other audio. The common file extension is .amr.
File extension AMR formatted file has been coded with eight source codecs with bit-rates of 12.2, 10.2, 7.95, 7.40, 6.70, 5.90, 5.15 and 4.75 kbit/s. AMR codec was developed by Ericsson.
File extension AMR has been extensively used in cell phones as a basic audio file format. Because the bandwidth limitation, AMR utilizes Discontinuous Transmission (DTX), with Voice Activity Detection (VAD) and Comfort Noise Generation (CNG) to reduce bandwidth usage during silence periods.
AMR player is a free freeware to play AMR audio files, which can convert AMR with MP3/WAV audio format. Quicktime player and RealPlayer can also play AMR audio files.
AMR is also used in VoIP (Voice over Internet Protocol) services, which allows for extremely high QoS (Quality of Service) results due to the utilization of 8 different bit rates.
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