My Format Factory
My Format Factory

What is AMR?

Audio Format Description

AMR, or Adaptive Multi-Rate, is an audio data compression scheme used in speech coding. This open standard format involves compressing of audio data to allow more storage on voice files. Originally developed for GSM (Global System for Mobile), a circuit-switched telecommunication system, it has now been adopted by most cellular companies all over the world.

AMR operates on narrow-band signals (200-3400 Hz) at eight different bit rates - 12.2, 10.2, 7.95, 7.40, 6.70, 5.90, 5.15 and 4.75 kb/s – which are based on frames containing 160 samples and are 20 milliseconds long. AMR is optimized for link adaptation, which enables it to select the best coding technique for better reproduction. The coding techniques that AMR uses are ACELP (Algebraic Code Excited Linear Prediction), DTX (Discontinuous Transmission), VAD (Voice Activity Detection), and CNG (Comfort Noise Generation). Hence the name Adaptive Multi-Rate.

The benefits of AMR are:

  • AMR provides the best end-to-end solution to various applications, its flexible bit rate enables error correction
  • AMR can be used in multi-media applications after being encapsulated in 3GP or MPEG-4 file formats
  • AMR can easily be applied in low bit rate speech coding
  • AMR has the most consistent performance across all major languages

    AMR’s applications include multi-media services for cellular communication systems, Wi-Fi telephony, digital radio broadcasting, conferencing, voice over IP, internet applications, streaming, content downloads, unified messaging, and in portable audio devices.

    AMR is also a file format used for storing spoken audio. The main use of this file format is in storing short recordings in mobile telephones using the AMR codec. AMR is said to have more bits available for speech coding than any other speech codec, thus giving the most natural sounding voice quality to a recording than any other codec.


    User-friendly AMR Converter

    • AMR to WAV
    • AMR to MP3
    • AMR to AAC
    • Very flexible - change all settings to YOUR taste
    • Batch mode: convert any number of .AMR files at a time
    • Suggests lots of hits for beginners
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    AMR Converter

  • Wit of the day

    Music is the shorthand of emotion.
    Leo Tolstoy