SILK is an audio compression
format and audio codec
developed by Skype Limited
, now a Microsoft
subsidiary. It was developed for use in Skype
, as a replacement for the SVOPC
codec. Since licensing out, it has also been used by others. It has been extended to the Internet standard Opus
Skype Limited announced that SILK can use a sampling frequency
of 8, 12, 16 or 24 kHz and a bit rate
from 6 to 40 kbit/s. It can also use a low algorithmic delay
of 25 ms (20 ms frame size + 5 ms look-ahead).
The reference implementation is written in the C programming language. The codec technology is based on linear predictive coding
The SILK binary SDK
The SILK codec is patented and licensed separately from the SILK SDK.
The codec is open-source
, available royalty free
with restrictions on use and distribution.
The SDK was initially available only by application by giving details of name, address, phone, and description of how SILK will be used.
(version 1.0.9) the SDK can by downloaded without application, but the licence restricts the use to internal evaluation and testing purposes only, excluding software distribution or use in any commercial product or service.
SILK replaces the previously used SVOPC
in Skype, which was a in-house solution to replace the iSAC
, which again were licensed from Global IP Solutions
. The SILK codec was a separate development branch from SVOPC and it has been under development for over 3 years.
It was announced in January 2009 on the Consumer Electronics Show
and was integrated in Skype for the first time in version 4.0 beta 3 from January 7, 2009,
with the final version being released on February 3.
On March 3, 2009 Skype Limited announced that the SILK codec will be available soon under a royalty free
license to third-party software and hardware developers.
The first draft of the ''SILK Speech Codec'' description was submitted to the Internet Engineering Task Force
(IETF) as a candidate for the standardisation of a new Internet wideband audio codec on July 6, 2009, thereby openly publishing the format along with the source code of the reference implementation.
There is also a first draft of the ''RTP
Payload Format and File Storage Format for SILK Speech and Audio Codec''.
SILK is a foundation (with CELT
) of the hybrid codec ''Opus
'' (at the time called "Harmony") that was submitted to the IETF in September 2010,
and was chosen as the final candidate for the new standard. Opus was published as an IETF proposed standard in September 2012.
* The stable version of SILK was first introduced in Skype 4.0 Beta 3 for Windows, released on January 7, 2009.
* The final version of Skype 4.0 was released on February 3, 2009.
* On March 22, 2011 the Steam game platform
started using the SILK codec for its integrated in-game and community voice chat.
* Later in 14 April, in ''Team Fortress 2
'', the codec was implemented into the in-game voice chat.
* On January 29, 2013 the updated to SteamPipe platform Gold Source
started using the SILK codec for the in-game voice chat.
* It has been found being used on Zoom
* Skype protocol
* Comparison of audio formats
* Forward error correction
Category:Microsoft free software
Category:Software using the BSD license
Category:Free software programmed in C++