G.729 is an ITU standard codec.
Has two main flavors: A and B, see the ITU G series page for more info.

It offers toll quality speech at a reasonably low bit rate of 8Kbps. However, it is a rather "costly" codec in terms of CPU processing time, therefore some VoIP phones and adapters (notably the Linksys/Sipura/Cisco brands) can only handle one G.729 call (channel) at a time. This can cause calls to fail if the user attempts to use three-way calling, or place simultaneous calls on both lines of a two-line device, and G.729 is the only allowed codec.

Use of this codec in a product requires licensing. Licenses can be purchased from a company that re-sells G.729 licenses such as:

• Digium
• Howler Technologies
• VoiceAge

There are some free for non-commerical experimental use implementations for G.729

• http://www.readytechnology.co.uk/open/ipp-codecs-g729-g723.1/ for Asterisk based on Intel libraries
• VoiceAge Windows executable
• Intel Windows and Linux
• The ITU has reference source code available.
  • If your are not ITU member and want to download reference code for free:
    • Go to ITU Electronic Bookshop;
    • Select option #2: "I wish to REGISTER in order to download up to three (3) ITU Recommendations free of charge";
    • Receive mail with your access code.
  • Select recomendation at http://www.itu.int/rec/T-REC-G.729/e
  • Select language and format
  • Enter Login/Special ID* and Password and press Login.
  • Press button "Download ....."
  • NOTE: The descriptions for items with source code say something about "diskettes".

VOIP Phone Support

This codec is supported by at least the following phones:

• ACT P104SLD IP Phone - SIP IP phone
• Cisco ATA 186 - analogue phone adapter (limited to 1 channel)
• Cisco 79XX - hard phone
• Firefly - IAX softphone (with external DLL)
• Grandstream BudgeTone 100 series IP phones
• Sipura SPA-841 VOIP phone
• Sipura SPA-2000 - analogue phone adapter (limited to 1 channel)
• Sipura SPA-2002 - analogue phone adapter (limited to 1 channel)
• Sipura SPA-3000 ATA
• SNOM phones - SIP IP phone (ie. SNOM190)
• X-Pro
• Zyxel P2000W V2
• Polycom IP 301/330/601
• Linksys RTP300 and WRTP54G

Other Resources

• VoiceAge G.729A Mailing List
• Howler G.729a Installation and Licensing for Asterisk/Freeswitch
• Digium G.729a Installation and Licensing

Asterisk server supports it in pass-thru or with a license

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• Codecs
• ITU G series recommendations