World Library  
Flag as Inappropriate
Email this Article

Internet Low Bitrate Codec

Article Id: WHEBN0002915808
Reproduction Date:

Title: Internet Low Bitrate Codec  
Author: World Heritage Encyclopedia
Language: English
Subject: SILK, Opus (audio format), FFmpeg, Moving Picture Experts Group, Speech codecs
Collection: Free Audio Codecs, Speech Codecs
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Internet Low Bitrate Codec

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), Ooma,[6] and many others.

iLBC was submitted to IETF in 2002[7][8] and the final specification was published in 2004.

Contents

  • Parameters and features 1
  • See also 2
  • References 3
  • External links 4

Parameters and features

  • Sampling frequency 8 kHz/16 bit (160 samples for 20 ms frames, 240 samples for 30 ms frames)
  • Controlled response to packet loss, delay and jitter
  • Fixed bitrate (15.2 kbit/s for 20 ms frames, 13.33 kbit/s for 30 ms frames)
  • Fixed frame size (304 bits per block for 20 ms frames, 400 bits per block for 30 ms frames)
  • Robustness similar to pulse code modulation (PCM) with packet loss concealment, like the ITU-T G.711
  • CPU load similar to G.729A, with higher basic quality and better response to packet loss
  • Royalty-free
  • Since 2011 it is available under an open source (3-clause BSD license) license as a part of the open source WebRTC project.[5] (previously commercial use of the source code supplied by GIPS required a licence[9])
  • PSQM testing under ideal conditions yields mean opinion scores of 4.14 for iLBC (15.2 kbit/s), compared to 4.3 for G.711 (µ-law)

See also

References

  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. ^ Ooma * codes 
  7. ^ Roar Hagen, Speech Coders - a VoIP perspective, retrieved 2011-06-23 
  8. ^ "Internet Low Bit Rate Codec - draft-andersen-ilbc-00.txt". 2002. Retrieved 2011-06-23. 
  9. ^ former GIPS license

External links

  • Official homepage
  • iLBC former homepage
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.