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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.).[1][2] 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.[3] It is an implementation of the mono version of Polycom's Siren 14 audio coding format.[4][2]

G.722.1 is the successor to PT716plus developed by PictureTel Corp. (now Polycom, Inc.),[2] 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.[5] G.722.1/Annex C was approved by ITU-T on May 14, 2005.[3]

G.722.1 is a transform-based compressor that is optimized for both speech and music. The G.722.1 algorithm is based on lapped transform technology, using a Modulated Lapped Transform (MLT). The computational complexity is quite low (5.5 floating-point MIPS) for an efficient high-quality compressor, and the algorithmic delay end-to-end is 40 ms. A 14 kHz (32 ksps) extension, G.722.1/Annex C, was approved by ITU-T on May 14, 2005. Also known as the mono version of Siren 14, this extension is also available from Polycom as a royalty-free license.[6]

The numbering of the wideband ITU audio codecs is sometimes confusing. There are three principal codecs, which are unrelated, but all carrying the G.722 label. G.722 is the original 7 kHz codec, using ADPCM and operating at 48 – 64 kbit/s. G.722.1, another 7 kHz codec, operates at half the data rate while delivering comparable or better quality as G.722, but is a transform-based codec. G.722.1 Annex C is very similar to G.722.1, but provides twice the audio bandwidth, 14 kHz. And G.722.2, which operates on wideband speech and delivers very low bitrates, is an ACELP-based algorithm.


G.722.1 is available under a royalty-free license by Polycom Corporation, who owns all rights.[6][7][8][9][10] Licensees also receive the right to use Polycom's 16 kbit/s decoder extension of G.722.1, as well as G.722.1 Annex C, and Polycom's IP within the new 20 kHz ITU fullband codec, G.719.

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  1. ^ Business Wire (2001-03-26). "PictureTel Announces New Siren Wideband Audio Technology Licensing Program". thefreelibrary.com. Retrieved 2009-09-10. 
  2. ^ a b c "Polycom Siren/Codecs FAQs". Polycom, Inc. Retrieved 2014-07-16. 
  3. ^ a b ITU-T (May 2005). ITU-T G.722.1, 05/2005 (ZIP, PDF). ITU-T. p. i. Retrieved 2009-09-10. 
  4. ^ "ITU Approves Polycom Siren14 as New International Standard". businesswire.com. 2005-04-12. Retrieved 2014-07-16. 
  5. ^ Business Wire (2000-07-19). "PictureTel Licenses Audio Technology Suite to Intel". thefreelibrary.com. Retrieved 2009-09-10. 
  6. ^ a b Polycom, Inc. "Polycom Siren/Codecs FAQs - What are the terms on the free license?". Polycom, Inc. Retrieved 2014-07-16. 
  7. ^ "libg722_1 - COPYING". FreeSWITCH. Retrieved 2014-07-16. 
  8. ^ Polycom, Inc. "Siren7/Siren14/G.719 License Agreement". Polycom, Inc. Retrieved 2014-07-16. 
  9. ^ Xiph.Org Foundation (2009). "CELT - Codec Feature Comparison". Xiph.Org Foundation. Retrieved 2009-09-07. 
  10. ^ Xiph.Org Foundation (2006). "Speex - Codec Quality Comparison". Xiph.Org Foundation. Retrieved 2009-09-07. 

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