G.722.1
G.722.1 is a licensed royalty-free ITU-T standard audio codec providing high quality, moderate bit rate (24 and 32 kbit/s) wideband (50 Hz – 7 kHz audio bandwidth, 16 ksps (kilo-samples per second) audio coding. It is a partial implementation of Siren 7 audio coding format (which offers bit rates 16, 24, 32 kbit/s) developed by PictureTel Corp. (now Polycom, Inc.). Its official name is Low-complexity coding at 24 and 32 kbit/s for hands-free operation in systems with low frame loss.
G.722.1 Annex C (or G.722.1C) is a low-complexity extension mode to G.722.1, which doubles the algorithm to permit 14 kHz audio bandwidth using a 32 kHz audio sample rate, at 24, 32, and 48 kbit/s. It is included in the official ITU-T Recommendation G.722.1. The name of this annex is Annex C – 14 kHz mode at 24, 32, and 48 kbit/s. It is an implementation of the mono version of Polycom's Siren 14 audio coding format.
G.722.1 is the successor to PT716plus developed by PictureTel Corp. (now Polycom, Inc.), which has been used in videoconferencing systems for many years. As ITU-T Recommendation G.722.1, it was approved on September 30, 1999 after a four-year selection process involving extensive testing. G.722.1/Annex C was approved by ITU-T on May 14, 2005.