G.723.1 is an audio codec for voice that compresses voice audio in 30 ms frames. An algorithmic look-ahead of 7.5 ms duration means that total algorithmic delay is 37.5 ms. Its official name is Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s. It is sometimes associated with a Truespeech trademark in coprocessors produced by DSP Group.
Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s
There are two bit rates at which G.723.1 can operate:
6.3 kbit/s (using 24-byte frames) using a MPC-MLQ algorithm (MOS 3.9)
5.3 kbit/s (using 20-byte frames) using an ACELP algorithm (MOS 3.62)
G.723.1 is mostly used in Voice over IP (VoIP) applications due to its low bandwidth requirement. Music or tones such as DTMF or fax tones cannot be transported reliably with this codec, and thus some other method such as G.711 or out-of-band methods should be used to transport these signals. The complexity of the algorithm is below 16 MIPS. 2.2 kilobytes of RAM is needed for codebooks.
G.723.1 is a required audio codec in the H.324 ITU-T recommendation for H.324 terminals offering audio communication. In 3GPP3G-324M specification support for G.723.1 is not mandatory, but recommended.
Sampling frequency 8 kHz/16-bit (240 samples for 30 ms frames)
Fixed bit rate (5.3 kbit/s with 20 byte 30 ms frames, 6.3 kbit/s with 24 byte 30 ms frames)
Fixed frame size for each rate (5.3 kbit/s with 20 byte 30 ms frames, 6.3 kbit/s with 24 byte 30 ms frames)
Algorithmic delay is 37.5 ms per frame, with 7.5 ms look-ahead delay
G.723.1 is a hybrid speech coder, with high bit rate using multi-pulse maximum likelihood quantization (MP-MLQ) and low bit rate using algebraic code-excited linear prediction (ACELP)
The complexity of the algorithm is rated at 25, using a relative scale where G.711 is 1 and G.729a is 15.
As of January 1, 2017, the patent terms of most patents applying to G.723.1 have expired. With regard to the unexpired licensed patents of their G.723.1 patent license agreement, the licensors of G.723.1 patents, namely AudioCodes, Orange SA, and Université de Sherbrooke have agreed to license their patents under the existing terms on a royalty-free basis starting January 1, 2017.
^"G.723.1: Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s". www.itu.int. Archived from the original on 2021-06-13. Retrieved 2021-06-13.
^"CT8022 VOIP/VON G.723.1, G729AB TRUESPEECH® CO-PROCESSOR" (PDF). Archived from the original (PDF) on 4 April 2018. Retrieved 4 April 2018. The CT8022 has built-in TrueSpeech 8.5 (compatible with Microsoft Sound System 2.0, and a standard part of Microsoft Windows 95), and TrueSpeech G.723.1 (for H.323 and H.324). [...] The CT8022 provides two additional non-ITU TrueSpeech data rates at 4.8 and 4.1 KBPS.
^"SiproLAB Telecom - patent pool creation and management for standardized telecommunication technologies". 2017-12-22. Archived from the original on 2017-12-22. Retrieved 2018-01-10.
^VoiceAge Corporation (2007-10-14). "G.723.1 Licensing". Archived from the original on 2007-10-14. Retrieved 2009-09-17.
^Sipro Lab Telecom (2007-10-25). "FAQ G.729 and G.723.1". Archived from the original on 2007-10-25. Retrieved 2009-09-17.
^Sipro Lab Telecom (2006-10-29). "G.723.1, the highest ITU-T compression ratio". Archived from the original on 2006-10-29. Retrieved 2009-09-17.
^Sipro Lab Telecom (2006-10-29). "G.723.1 - Members". Archived from the original on 2006-10-29. Retrieved 2009-09-17.