Internet Low Bitrate Codec
Internet Low Bitrate Codec is a royalty-free narrowband speech audio coding format and an open-source reference implementation, developed by Global IP Solutions formerly Global IP Sound. It was formerly freeware with limitations on commercial use, but since 2011 it is available under a free software/open source license as a part of the open source WebRTC project. 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.
iLBC handles 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 cause errors to propagate 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, Google Talk, Maemo Recorder, Polycom IP Phone, Cisco, QuteCom, Tuenti, Yahoo! Messenger, Ooma and many others.
iLBC was submitted to IETF in 2002 and the final specification was published in 2004.Parameters and features
