G.723.1 is an audio codec for voice that compresses voice audio in chunks of 30 milliseconds. Look ahead of 7.5 ms is also needed. Music or tones such as DTMF or Fax tones cannot be transported reliably with this CODEC, and thus use G.711 or Out-of-band methods to transport these signals.

G.723.1 is mostly used in Voice over IP (VoIP) applications for its low bandwidth requirement. ITU standard was finished in 1995. The complexity of the algorithm is below 16 MIPS 2.2 kilo bytes of RAM is needed for codebooks.

• There are 2 rates:
  • 6.3 Kbits/s (24 bytes chunks) uses MPC-MLQ algorithm
  • 5.3 Kbits/s (20 bytes chunks) uses ACELP algorithm

See also G.711, G.729