AMR refers to Adaptive Multi-Rate audio codec, which is a patented audio data compression scheme. It was adopted as the standard speech codec by 3GPP in 1998, developed and widely used in GSM and UMTS in 1999.

The storage of spoken audio used is AMR format files. Based on ISO base media file format, it is the container of 3GPP-specified 3GP container. When you use mobile telephone handsets, or you want to leave a short recording message, the information you leave is saved in the AMR format. It is widely used in the answering service industry. Currently it is used more and more in the cell phone industry. Additionally, as to random access and synchronization with video, this kind of application is with more advanced demands on the storage format. AMR is an appropriate format.

AMR uses link adaptation to select from one of eight different bit rates based on link conditions. The optimized link adaptation can select out the best codec mode that can meet the local radio channel and capacity requirements. If the radio conditions are bad, the source coding will be reduced and channel coding will be increased. The new intelligent system allows the network operator to prioritize the capacity of the base station. This optimized method may sacrifice some voice clarity, but improve the quality and robustness of the network connection.

A file with the AMR file extension is an Adaptive Multi-Rate ACELP Codec file, a technology aiming at encoding audio files. To open these files needs an AMR viewer or editor application installed. The easiest way to open an AMR file is to double-click on it and your PC will choose the right application.

There is an easy way to convert an AMR file to another file. First open the AMR file and save it as another file format. Then use a File Conversion Online Service or software program to convert the AMR file to another file format. To do this, you need the right program to open and convert AMR files.