Internet Low Bitrate Codec

From Wikipedia, the free encyclopedia
  (Redirected from Internet Low Bit Rate Codec)
Jump to: navigation, search
Internet Low Bit Rate Codec (iLBC)
Filename extension .lbc[1]
Internet media type audio/iLBC[1]
Magic number '#!iLBC30\n' or '#!iLBC20\n'[1]
Developed by Global IP Solutions, now Google Inc
Initial release 2004 (2004)[1]
Type of format Audio compression format
Standard RFC 3951
iLBC Speech Coder
Developer(s) Global IP Solutions, now Google Inc
Initial release 2004
Written in C
Operating system Cross-platform
Type Audio codec, reference implementation
License 3-clause BSD
Website http://www.webrtc.org/ilbc-freeware

Internet Low Bitrate Codec (iLBC) is an open source royalty-free narrowband speech audio coding format and reference codec implementation, developed by Global IP Solutions (GIPS) formerly Global IP Solutions(acquired by Google Inc in 2011[2]). It was formerly freeware with limited commercial use,[3][4] but since 2011 it is available under a free software/open source (3-clause BSD license) license as a part of the open source WebRTC project.[5] It is suitable for VoIP applications, streaming audio, archival and messaging. The algorithm is a version of block-independent linear predictive coding, with the choice of data frame lengths of 20 and 30 milliseconds. The encoded blocks have to be encapsulated in a suitable protocol for transport, usually the Real-time Transport Protocol (RTP).

iLBC handles the case of lost frames through graceful speech quality degradation. Lost frames often occur in connection with lost or delayed IP packets. Ordinary low-bitrate codecs exploit dependencies between speech frames, which unfortunately results in error propagation when packets are lost or delayed. In contrast, iLBC-encoded speech frames are independent and so this problem will not occur.

iLBC is defined in RFC 3951. It is one of the codecs used by Gizmo5, webRTC, Ekiga, QuteCom, Google Talk, Yahoo! Messenger, Polycom IP Phone and Maemo Recorder (on the Nokia N800/N810) and many others.

iLBC was submitted to IETF in 2002[6][7] and the final specification was published in 2004.

Parameters and features[edit]

See also[edit]

References[edit]

  1. ^ a b c d "Real-time Transport Protocol (RTP) Payload Format for internet Low Bit Rate Codec (iLBC) Speech". 2004. Retrieved 2011-06-23. 
  2. ^ Dana Blankenhorn (2010-05-18). "Why Google bought Global IP Solutions". Retrieved 2011-06-23. 
  3. ^ "Global IP Solutions iLBC Freeware Public License" (PDF). 2008-10-30. Retrieved 2011-06-23. 
  4. ^ "iLBCfreeware". 
  5. ^ a b "iLBC Freeware". Retrieved 2011-06-23. 
  6. ^ Roar Hagen, Speech Coders - a VoIP perspective, retrieved 2011-06-23 
  7. ^ "Internet Low Bit Rate Codec - draft-andersen-ilbc-00.txt". 2002. Retrieved 2011-06-23. 
  8. ^ former GIPS license

External links[edit]