Internet Low Bitrate Codec (iLBC) is a royalty-free

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 usua ...

speech

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 ...

and an open-source

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 o ...

(

codec A codec is a device or computer program 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 on a signal or ...

), 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 IP networks, before it was acquired by Google in May 2010. The company delivered embedded software th ...

(GIPS) formerly Global IP Sound (acquired by

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

in 2011). It was formerly

freeware Freeware is software, most 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 t ...

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

free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...

/open source (

3-clause BSD license BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...

) 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 to wor ...

project. It is suitable for

VoIP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...

applications,

streaming audio Streaming media is multimedia that is delivered and consumed in a continuous manner from a source, with little or no intermediate storage in network elements. ''Streaming'' refers to the delivery method of content, rather than the content it ...

, 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 mod ...

, with the choice of

data frame A frame is a digital data transmission unit in computer networking and telecommunication. 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 s ...

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 applicati ...

(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 Gizmo5 (formerly known as Gizmo Project and SIPphone) was a voice over IP communications network and a proprietary freeware soft phone for that network. On November 12, 2009, Google announced that it had acquired Gizmo5. On March 4, 2011, Google ...

Ekiga Ekiga (formerly called GnomeMeeting) is a VoIP and video conferencing application for GNOME and Microsoft Windows. It is distributed as free software under the terms of the GNU GPL-2.0-or-later. It was the default VoIP client in Ubuntu until Octob ...

, Google Talk,

Maemo Recorder Maemo is a software platform originally developed by Nokia, now developed by the community, for smartphones and Internet tablets. The platform comprises both the Maemo operating system and SDK. Maemo played a key role in Nokia's strategy to c ...

(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 The Nokia N810 Internet tablet is an Internet appliance from Nokia, announced on 17 October 2007 at the Web 2.0 Summit in San Francisco. Despite Nokia's strong association with cellular products, the N810, like preceding tablets produced by Nok ...

Polycom IP Phone Poly, formerly Polycom, a part of HP Inc., is an American multinational corporation that develops video, voice and content collaboration and communication technology. Polycom was co-founded in 1990 by Brian L Hinman and Jeffrey Rodman. In 2018 ...

Cisco Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational digital communications technology conglomerate corporation headquartered in San Jose, California. Cisco develops, manufactures, and sells networking hardware, ...

QuteCom QuteCom (previously called WengoPhone) was a free-software SIP-compliant VoIP client developed by the QuteCom (previously OpenWengo) community under the GPL-2.0-or-later license. It allows users to speak to other users of SIP-compliant VoIP sof ...

Tuenti Tuenti Technologies, S.L.U is a mobile virtual network operator (MVNO) that operates with the Tuenti brand owned by Telefónica. It is a Spain-based tech company that focuses on providing a cloud-based services through its own application and i ...

Yahoo! Messenger Yahoo! Messenger (sometimes abbreviated Y!M) was an advertisement-supported instant messaging client (computing), client and associated protocol provided by Yahoo!. Yahoo! Messenger was provided free of charge and could be downloaded and used wit ...

, 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.Kur ...

, delay and jitter * 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 sampled 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 (comp ...

(PCM) with

packet loss concealment Packet loss concealment (PLC) is a technique to mask the effects of packet loss in voice over IP (VoIP) communications. When the voice signal is sent as VoIP packets on an IP network, the packets may (and likely will) travel different routes. A pa ...

, like the

ITU The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...

-T

G.711 G.711 is a narrowband audio codec originally designed for use in telephony that provides toll-quality audio at 64 kbit/s. G.711 passes audio signals in the range of 300–3400 Hz and samples them at the rate of 8,000 samples per second ...

* CPU load similar to

G.729A G.729 is a royalty-free narrow-band vocoder-based audio data compression algorithm using a frame length of 10 milliseconds. It is officially described as ''Coding of speech at 8 kbit/s using code-excited linear prediction'' speech coding (CS-ACEL ...

, with higher basic quality and better response to packet loss * Royalty-free * Since 2011 it is available under an open source (

) license as a part of the open source

project. (previously commercial use of the source code supplied by GIPS required a licenceformer GIPS license
) *

PSQM Perceptual Speech Quality Measure (PSQM) is a computational and modeling algorithm defined in Recommendation ITU-T P.861 that objectively evaluates and quantifies voice quality of voice-band (300 – 3400 Hz) speech codecs. It may be used to ...

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 t ...

s of 4.14 for iLBC (15.2 kbit/s), compared to 4.3 for

( 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