Girish Mahajan (Editor)

Internet Speech Audio Codec

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Internet media type
  
audio/isac

Developed by
  
Global IP Solutions, now Google Inc

Type of format
  
Audio compression format

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, 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, which includes a royalty-free license for iSAC when using the WebRTC codebase.

Parameters and features

  • Sampling frequency of 16 kHz (wideband) or 32 kHz (superwideband)
  • 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

    • References

    Internet Speech Audio Codec Wikipedia
    (Text) CC BY-SA