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