internet Speech Audio Codec（iSAC）

 

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internet Speech Audio Codec (iSAC)

Internet media type	audio/isac[1]
Developed by	Global IP Solutions, now Google Inc
Type of format	Audio compression format

 

iSAC Codec

Developer(s)	Global IP Solutions, now Google Inc
Written in	C
Operating system	Cross-platform
Type	Audio codec, reference implementation
License	formerly proprietary, now 3-clause BSD
Website	[1]

 

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, 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^[4], which includes a royalty-free license for iSAC when using the WebRTC codebase^[5].

 

Parameters and features

• Sampling frequency 16 kHz^[1] (or 32 kHz according to WebRTC^[6][7])
• Adaptive and variable bit rate (10 kbit/s to 32 kbit/s) (or 10 kbit/s to 52 kbit/s according to WebRTC^[6][7])
• Adaptive packet size 30 to 60ms
• Complexity comparable to G.722.2 at comparable bit-rates
• Algorithmic delay of frame size plus 3ms