AMR File Documentation

Overview

Feature Value
File Extension .amr
Full Name Adaptive Multi-Rate Codec File
MIME Type audio/amr
Format Type Audio file format
Developed By 3rd Generation Partnership Project (3GPP)
Compression Yes, Lossy
Bit Rates Variable, 4.75 to 12.2 kbps
Channels Mono
Sample Rate 8000 Hz
Usage Speech Compression
Codec AMR-NB (Narrow Band)
File Structure Header followed by audio data frames
Header Identifier #!AMR
Popularity Common in mobile telephony
Advantages Good compression, optimized for speech
Disadvantages Lossy, not suitable for music
Adaptive Multi-Rate - Wideband (AMR-WB) Extension .amr but with higher fidelity
License Proprietary
Alternative Formats MP3, AAC, OGG
Typical Applications VoIP, Audio Recording in Mobile Phones