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iLBC is now part of the WebRTC project. Please go to for the latest information about iLBC.
This site is kept for historical reference only.

What is iLBC?

iLBC (internet Low Bitrate Codec) is a FREE speech codec suitable for robust voice communication over IP. The codec is designed for narrow band speech and results in a payload bit rate of 13.33 kbit/s with an encoding frame length of 30 ms and 15.20 kbps with an encoding length of 20 ms. The iLBC codec enables graceful speech quality degradation in the case of lost frames, which occurs in connection with lost or delayed IP packets.


  • Bitrate 13.33 kbps (399 bits, packetized in 50 bytes) for the frame size of 30 ms and 15.2 kbps (303 bits, packetized in 38 bytes) for the frame size of 20 ms

  • Basic quality higher then G.729A, high robustness to packet loss

  • Computational complexity in a range of G.729A

  • Royalty Free Codec

iLBC MOS chart

iLBC is free

Unlike other low bitrate codecs, iLBC is available for free and comes with full source code.

Contributing to the project

It is easy to contribute to the project. All you need to do is find a part of iLBC that you think could be improved or extended and make those changes (carefully and cleanly) and submit that back to the Project, by contacting us via this email or through IETF Audio Video Transport (avt) Working Group mailing list This could be anything from documentation, added functionality (such as Voice Activation Detection), to improvements on the source code. 


· Announcements
· iLBC codec spec
RTP Payload Format for iLBC 

Dec 6th, 2004. The final IETF RFC versions of the iLBC codec spec and the iLBC RTP Profile draft is available.

Aug 9th, 2004. GIPS iLBC has been specified as a mandatory codec in the recently released CableLabs PacketCableTM 1.1 Audio/Video Codec


· · Kphone 2.1 and above
· Asterisk Open Source PBX
· OpenH323
· More...

· SIPforum
· More...

Sponsored by:

 GIPS logo

To learn more about iLBC, please check the following presentations and IETF draft.


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