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Internet Speech Audio Codec

Topic: Software

 From HandWiki - Reading time: 5 min

internet Speech Audio Codec
Internet media typeaudio/isac[1]
Developed byGlobal IP Solutions, now Google Inc
Type of formatAudio compression format
Codec
Developer(s)Global IP Solutions, now Google Inc
Written inC
Operating systemCross-platform
TypeAudio codec, reference implementation
Licenseformerly proprietary, now 3-clause BSD
Websitewebrtc.org

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)[1][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)[1][6][7]
  • 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

References

  1. ↑ 1.0 1.1 1.2 Grand, Tina le; Jones, Paul; Huart, Pascal; Shabestary, Turaj Zakizadeh; Alvestrand, Harald T. (2013). "RTP Payload Format for the iSAC Codec". https://tools.ietf.org/html/draft-ietf-avt-rtp-isac-04. 
  2. ↑ Dana Blankenhorn (2010-05-18). "Why Google bought Global IP Solutions". http://www.zdnet.com/blog/open-source/why-google-bought-global-ip-solutions/6501. 
  3. ↑ "iLBC Freeware". http://www.webrtc.org/ilbc-freeware. 
  4. ↑ webrtc.org/faq/#what-is-the-isac-audio-codec .
  5. ↑ webrtc.org/license/additional-ip-grant/ .
  6. ↑ 6.0 6.1 "WebRTC FAQ - What are the parameters of iSAC?". http://sites.google.com/site/webrtc/faq#TOC-What-are-the-parameters-of-iSAC-. 
  7. ↑ 7.0 7.1 "WebRTC components". http://www.webrtc.org/reference/webrtc-components#TOC-iSAC. 



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