internet Speech Audio Codec
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internet Speech Audio Codec (iSAC) is a
wideband In communications, a system is wideband when the message bandwidth significantly exceeds the coherence bandwidth of the Channel (communications), channel. Some communication links have such a high Bit rate, data rate that they are forced to use a ...
speech Speech is a human vocal communication using language. Each language uses Phonetics, phonetic combinations of vowel and consonant sounds that form the sound of its words (that is, all English words sound different from all French words, even if ...
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 da ...
, 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 em ...
(GIPS) (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 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 and
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 ...
. The encoded blocks have to be encapsulated in a suitable protocol for transport, e.g. RTP. It is one of the codecs used by AIM Triton, the
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 ...
, QQ, and
Google Talk Google Talk was an Instant messaging, 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 ...
. It was formerly a proprietary codec licensed by Global IP Solutions. As of June 2011, it is part of
open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
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, which includes a royalty-free license for iSAC when using the WebRTC codebase.webrtc.org/license/additional-ip-grant/


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 sp ...
of 16 kHz (wideband) or 32 kHz (superwideband) * Adaptive and variable
bit rate 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 w ...
of 10 kbit/s to 32 kbit/s (wideband) or 10 kbit/s to 52 kbit/s (superwideband) * Adaptive packet size 30 to 60 ms * Complexity comparable to
G.722.2 G7 is the Group of Seven, a group of seven industrialized nations, formed by Canada, France, Germany, Italy, Japan, the United Kingdom and the United States. G7 or G.VII may also refer to: Military * G7 howitzer, a light howitzer developed by ...
at comparable bit-rates * Algorithmic delay of frame size plus 3 ms


See also

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iLBC Internet Low Bitrate Codec (iLBC) is a royalty-free narrowband speech audio coding format and an open-source reference implementation (codec), developed by Global IP Solutions (GIPS) formerly Global IP Sound (acquired by Google Inc in 2011). It w ...
*
Opus (audio codec) Opus is a lossy audio coding format developed by the Xiph.Org Foundation and standardized by the Internet Engineering Task Force, designed to efficiently code speech and general audio in a single format, while remaining low-latency enough for ...
*
SILK Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the coc ...
*
G.722 G.722 is an ITU-T standard 7 kHz wideband audio codec operating at 48, 56 and 64 kbit/s. It was approved by ITU-T in November 1988. Technology of the codec is based on sub-band ADPCM (SB-ADPCM). The corresponding narrow-band codec based on ...
*
Speex Speex is an audio compression codec specifically tuned for the reproduction of human speech and also a free software speech codec that may be used on VoIP applications and podcasts. It is based on the CELP speech coding algorithm.Xiph.OrIntrodu ...
*
List of codecs The following is a list of compression formats and related codecs. Audio compression formats Non-compression * Linear pulse-code modulation (LPCM, generally only described as PCM) is the format for uncompressed audio in media files and it is al ...


References


External links


WebRTC codecs - GIT- source code for iSAC and other codecs
Speech codecs Free audio codecs Formerly proprietary software {{multimedia-software-stub