Internet Low Bitrate Codec (iLBC) is a

royalty-free Royalty-free (RF) material subject to copyright or other intellectual property rights may be used without the need to pay royalties or license fees for each use, per each copy or volume sold or some time period of use or sales. Computer standards ...

narrowband Narrowband signals are signals that occupy a narrow range of frequencies or that have a small fractional bandwidth. In the audio spectrum, ''narrowband sounds'' are sounds that occupy a narrow range of frequencies. In telephony, narrowband is ...

speech Speech is the use of the human voice as a medium for language. Spoken language combines vowel and consonant sounds to form units of meaning like words, which belong to a language's lexicon. There are many different intentional speech acts, suc ...

audio coding format An audio coding format (or sometimes audio compression format) is a content representation format for storage or transmission of digital audio (such as in digital television, digital radio and in audio and video files). Examples of audio coding f ...

and an

open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation ...

(

codec A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...

), developed by

Global IP Solutions Global IP Solutions (also known as GIPS) was a United States–based corporation that developed real-time voice and video processing software for Internet Protocol, IP networks, before it was acquired by Google in May 2010. The company delivered ...

(GIPS) formerly Global IP Sound (acquired by

Google Inc Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...

in 2011). It was formerly

freeware Freeware is software, often proprietary, that is distributed at no monetary cost to the end user. There is no agreed-upon set of rights, license, or EULA that defines ''freeware'' unambiguously; every publisher defines its own rules for the free ...

with limitations on commercial use, but since 2011 it is available under a

free software Free software, libre software, libreware sometimes known as freedom-respecting software is computer software distributed open-source license, under terms that allow users to run the software for any purpose as well as to study, change, distribut ...

/open source ( 3-clause BSD license) license as a part of the open source

WebRTC WebRTC (Web Real-Time Communication) is a free and open-source project providing web browsers and mobile applications with real-time communication (RTC) via application programming interfaces (APIs). It allows audio and video communication and ...

project. It is suitable for

VoIP Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...

applications, streaming audio, archival and messaging. The algorithm is a version of block-independent

linear predictive coding Linear predictive coding (LPC) is a method used mostly in audio signal processing and speech processing for representing the spectral envelope of a digital signal of speech in compressed form, using the information of a linear predictive model ...

, with the choice of

data frame A frame is a digital data transmission unit in computer networking and telecommunications. In packet switched systems, a frame is a simple container for a single network packet. In other telecommunications systems, a frame is a repeating structure ...

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 The Real-time Transport Protocol (RTP) is a network protocol for delivering audio and video over IP networks. RTP is used in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applic ...

(RTP). 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,

, Ekiga,

Google Talk Google Talk was an instant messaging service that provided both text and voice communication. The instant messaging service was variously referred to colloquially as Gchat, Gtalk, or Gmessage among its users. Google Talk was also the name o ...

Maemo Recorder Maemo is a Linux-based software platform originally developed by Nokia, now developed by the Free software movement, community, for smartphones and Internet tablets. The platform comprises both the Maemo operating system and Software development ...

(on the

Nokia N800 The Nokia N800 Internet tablet is a wireless Internet appliance from Nokia, originally announced at the Las Vegas CES 2007 Summit in January 2007. N800 allows the user to browse the Internet and communicate using Wi-Fi networks or with mobi ...

/ N810),

Polycom IP Phone Poly Inc., formerly Polycom, is an American multinational corporation that develops video, voice and content collaboration and communication technology. Poly is a subsidiary of HP Inc. Polycom was co-founded in 1990 by Brian L Hinman and Jeff ...

Cisco Cisco Systems, Inc. (using the trademark Cisco) is an American multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, s ...

, 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

Sampling frequency In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or s ...

8 kHz/16 bit (160 samples for 20 ms frames, 240 samples for 30 ms frames) * Controlled response to

packet loss Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is either caused by errors in data transmission, typically across wireless networks, or network congestion.Ku ...

, delay and

jitter In electronics and telecommunications, jitter is the deviation from true periodicity of a presumably periodic signal, often in relation to a reference clock signal. In clock recovery applications it is called timing jitter. Jitter is a signifi ...

* Fixed

bitrate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction ...

(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 Pulse-code modulation (PCM) is a method used to digitally represent analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitud ...

(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 Royalty-free (RF) material subject to copyright or other intellectual property rights may be used without the need to pay royalties or license fees for each use, per each copy or volume sold or some time period of use or sales. Computer standards ...

* Since 2011 it is available under an open source ( 3-clause BSD license) license as a part of the open source

project. (previously commercial use of the source code supplied by GIPS required a licence) * PSQM testing under ideal conditions yields

mean opinion score Mean opinion score (MOS) is a measure used in the domain of Quality of Experience and telecommunications engineering, representing overall quality of a stimulus or system. It is the arithmetic mean over all individual "values on a predefined scale ...

s of 4.14 for iLBC (15.2 kbit/s), compared to 4.3 for G.711 ( μ-law)

References

External links

Official homepage

iLBC former homepage
{{Compression Software Implementations Speech codecs Free audio codecs Open formats Software using the BSD license Formerly proprietary software

Parameters and features

See also

References

External links