AMR was designed to allow transcoder-free connectivity between GSM, US-TDMA and PDC networks; AMR is the 3GPP mandatory standard codec for narrowband speech over GSM, WCDMA, GPRS and EDGE networks. AMR operates at 8 bitrates in the range of 4.75 to 12.2 kbps and was specifically designed to improve link robustness. AMR supports dynamic adaptation to network conditions, using lower bitrates during network congestion or degradation while preserving audio quality. AMR provides toll quality speech starting at 7.4 kbps, with near-toll quality at lower rates and greater robustness and better reproduction of non-speech sounds at higher rates.

AMR Codec Overview

The memory and CPU details are generic Standard specifications.

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AMR Codec Technical Specifications

  • Bandwidth: 200-3400 Hz
  • Standardized: ETSI / 3GPP 1999
  • Technology: ACELP
  • Bit rate: 4.75/5.15/5.9/6.7/7.4/7.95/10.2/12.2 kbps
  • Delay (msec): 25
  • Frame size (msec): 20
  • Lookahead (msec): 5
  • Quality: Narrowband / PSTN
  • Complexity (MIPS): 20
  • ROM (bytes): 150K
  • RAM (bytes): 20K