AMR file format
| Extension | .amr |
| Category | audio |
| Programs | Apple QuickTime Realplayer VLC media Player |
| Main program | Audacity |
| Description | AMR is a compressed file format that is designed to improve speech coding and includes multiple sampling rates for narrowband devices used in encoding or decoding. AMR files can be recorded using mobile phones. To play video and audio files simultaneously or achieve random access memory, one can use the 3GPP format. Each frame contains 160 20-millisecond samples that are encoded using AMR with ACELP, DTX, VAD, and CNG. Recorded AMR files can be converted to other formats for distribution and use. |
| Technical details | AMR is capable of encoding signals in the range of 4.75 to 12.2 kbit/s, with quality starting at 7.4 kbit/s. 3GPP adopted this file format in 1999, which is used by GSM and UMTS. It employs link adaptation to choose from eight different bit rates. AMR optimizes link adaptation by selecting the best codec devices for use on radio channels and capacity requirements. However, this optimization only works if the connection is strong enough to prevent any loss of audio quality. |
| MIME type | audio/amr |