ISAC
Encyclopedia
internet Speech Audio Codec (iSAC) is a wideband
speech codec
, developed by Global IP Solutions
(GIPS) (acquired by Google Inc in 2011). It is suitable for VoIP applications and streaming audio. The encoded blocks have to be encapsulated in a suitable protocol for transport, eg. RTP
.
It is one of the codecs used by AIM
Triton, the Gizmo5
, QQ, and Google Talk
. It was formerly a proprietary codec
licensed by Global IP Solutions. As of June 2011, it is part of open source
WebRTC
project, which includes a royalty-free license for iSAC when using the WebRTC codebase.
Wideband
In communications, wideband is a relative term used to describe a wide range of frequencies in a spectrum. A system is typically described as wideband if the message bandwidth significantly exceeds the channel's coherence bandwidth....
speech codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
, developed by Global IP Solutions
Global IP Solutions
Global IP Solutions is a United States-based corporation that develops real-time voice and video processing software for IP networks. The company delivers embedded solutions that enable real-time communications capabilities for video and Voice over IP...
(GIPS) (acquired by Google Inc in 2011). It is suitable for VoIP applications and streaming audio. The encoded blocks have to be encapsulated in a suitable protocol for transport, eg. RTP
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...
.
It is one of the codecs used by AIM
AOL Instant Messenger
AOL Instant Messenger is an instant messaging and presence computer program which uses the proprietary OSCAR instant messaging protocol and the TOC protocol to allow registered users to communicate in real time. It was released by AOL in May 1997...
Triton, the Gizmo5
Gizmo5
Gizmo5 was a Voice over Internet Protocol communications network and a proprietary freeware soft phone for that network. On November 12, 2009, Google announced that it had acquired Gizmo5...
, QQ, and Google Talk
Google Talk
Google Talk is a freeware voice over Internet protocol client application offered by Google Inc. The first beta version of the program was released on August 24, 2005...
. It was formerly a proprietary codec
Proprietary software
Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...
licensed by Global IP Solutions. As of June 2011, it is part of open source
Open-source software
Open-source software is computer software that is available in source code form: the source code and certain other rights normally reserved for copyright holders are provided under a software license that permits users to study, change, improve and at times also to distribute the software.Open...
WebRTC
WebRTC
WebRTC is a framework that was open sourced on June 1, 2011 that allows web browsers to conduct real-time video chat.Its inclusion in the World Wide Web Consortium standards is supported by Google, Mozilla and Opera....
project, which includes a royalty-free license for iSAC when using the WebRTC codebase.
Parameters and features
- Sampling frequency 16 kHz (or 32 kHz according to WebRTCWebRTCWebRTC is a framework that was open sourced on June 1, 2011 that allows web browsers to conduct real-time video chat.Its inclusion in the World Wide Web Consortium standards is supported by Google, Mozilla and Opera....
) - Adaptive and variable bit rateBit rateIn telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
(10 kbit/s to 32 kbit/s) (or 10 kbit/s to 52 kbit/s according to WebRTCWebRTCWebRTC is a framework that was open sourced on June 1, 2011 that allows web browsers to conduct real-time video chat.Its inclusion in the World Wide Web Consortium standards is supported by Google, Mozilla and Opera....
) - Adaptive packet size 30 to 60ms
- Complexity comparable to G.722.2 at comparable bit-rates
- Algorithmic delay of frame size plus 3ms