Internet Speech Audio Codec Explained

internet Speech Audio Codec
Mime:	audio/isac^[1]
Owner:	Global IP Solutions, now Google Inc
Genre:	Audio compression format

Codec
Developer:	Global IP Solutions, now Google Inc
Programming Language:	C
Operating System:	Cross-platform
Genre:	Audio codec, reference implementation
License:	formerly proprietary, now 3-clause BSD

internet Speech Audio Codec (iSAC) is a wideband speech codec, developed by Global IP Solutions (GIPS) (acquired by Google Inc in 2011).^{[2] [3]} It is suitable for VoIP applications and streaming audio. 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, 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,^[4] which includes a royalty-free license for iSAC when using the WebRTC codebase.^[5]

Parameters and features

• Sampling frequency of 16 kHz (wideband) or 32 kHz (superwideband)^{[6] [7]}
• Adaptive and variable bit rate 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 at comparable bit-rates
• Algorithmic delay of frame size plus 3 ms

See also

• iLBC
• Opus (audio codec)
• SILK
• G.722
• Speex
• List of codecs

External links

• WebRTC codecs - GIT- source code for iSAC and other codecs

Notes and References

1. Web site: RTP Payload Format for the iSAC Codec . 2013 . 2016-04-30 . Grand . Tina le . Jones . Paul . Huart . Pascal . Shabestary . Turaj Zakizadeh . Alvestrand . Harald T. .
2. Web site: Why Google bought Global IP Solutions . https://web.archive.org/web/20100521163742/http://www.zdnet.com/blog/open-source/why-google-bought-global-ip-solutions/6501 . dead . May 21, 2010 . Dana Blankenhorn . . 2010-05-18 . 2011-06-23.
3. Web site: iLBC Freeware . 2011-06-23 . dead . https://web.archive.org/web/20110705082246/http://www.webrtc.org/ilbc-freeware . 2011-07-05 .
4. https://webrtc.org/faq/#what-is-the-isac-audio-codec webrtc.org/faq/#what-is-the-isac-audio-codec
5. https://webrtc.org/license/additional-ip-grant/ webrtc.org/license/additional-ip-grant/
6. Web site: WebRTC FAQ - What are the parameters of iSAC? . 2011-06-23 . 2016-11-17 . https://web.archive.org/web/20161117080721/http://sites.google.com/site/webrtc/faq#TOC-What-are-the-parameters-of-iSAC- . dead .
7. Web site: WebRTC components . 2011-06-23 . https://web.archive.org/web/20110628000815/http://www.webrtc.org/reference/webrtc-components#TOC-iSAC . 2011-06-28 . dead .