From Wikipedia, the free encyclopedia
Audio codec and compression format
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
codec.
Details
[
edit
]
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).
[2]
The reference implementation is written in the C programming language. The codec technology is based on
linear predictive coding
(LPC).
[3]
The SILK
binary
SDK
is available.
[4]
License
[
edit
]
The SILK codec is patented and licensed separately from the SILK SDK.
[5]
The codec is
open-source
,
freeware
, available
royalty free
with restrictions on use and distribution.
[4]
[6]
[7]
The SDK was initially available only by application by giving details of name, address, phone, and description of how SILK will be used.
[4]
As of 2012
[update]
(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.
[4]
[8]
History
[
edit
]
SILK replaces the previously used
SVOPC
in Skype, which was a in-house solution to replace the
iSAC
and
iLBC
, 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.
[9]
It was announced in January 2009 on the
Consumer Electronics Show
[9]
and was integrated in Skype for the first time in version 4.0 beta 3 from January 7, 2009,
[10]
with the final version being released on February 3.
[11]
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.
[6]
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.
[12]
There is also a first draft of the
RTP
Payload Format and File Storage Format for SILK Speech and Audio Codec
.
[13]
Opus
[
edit
]
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,
[14]
and was chosen as the final candidate for the new standard. Opus was published as an IETF proposed standard in September 2012
[15]
and Skype announced that they would be using Opus going forward.
[16]
Usage
[
edit
]
- The stable version of SILK was first introduced in Skype 4.0 Beta 3 for Windows, released on January 7, 2009.
[10]
- The final version of Skype 4.0 was released on February 3, 2009.
[17]
[18]
- 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.
[19]
- 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
.
[20]
See also
[
edit
]
References
[
edit
]
- ^
"SILK codec"
.
GitHub
. 23 August 2021.
- ^
Skype
SILK Data Sheet
, Retrieved 2009-09-01
- ^
Audio-Mitschnitt
Archived
2013-02-10 at the
Wayback Machine
vom Treffen der IETF-Codec-Arbeitsgruppe auf der Konferenz IETF79 in Peking, China mit einer Darstellung der grundlegenden Funktionsprinzipien durch Koen Vos (MP3, ~70 MiB)
- ^
a
b
c
d
Skype
SILK ? Super Wideband Audio Codec
, Retrieved 2009-09-01
- ^
"SILK Patent License"
.
Skype
. December 6, 2010
. Retrieved
October 27,
2023
.
- ^
a
b
Jonathan Christensen (2009-03-03)
SILK, our super wideband audio codec, is now available for free
Archived
2009-12-23 at the
Wayback Machine
, Retrieved 2009-09-01
- ^
Skype publishes SILK audio codec source code
, Retrieved 2012-12-26
- ^
Skype Developer Forum - SILK SDK license
Archived
2012-08-03 at the
Wayback Machine
, Retrieved 2012-12-26
- ^
a
b
Michael Stanford (2009-01-13)
Skype’s new super-wideband codec
, Retrieved 2009-09-01
- ^
a
b
Skype Journal (2009-01-07)
Skype for Windows 4.0 Beta 3 Hotfix Introduces New Audio Codec
, Retrieved 2009-09-01
- ^
"All-New Skype Now Available - About Skype"
. Archived from
the original
on 2013-07-30
. Retrieved
2012-07-14
.
- ^
IETF (2009-07-06)
SILK Speech Codec - draft-vos-silk-00.txt
, Retrieved 2009-09-01
- ^
IETF (2009-07-06)
RTP Payload Format and File Storage Format for SILK Speech and Audio Codec
, Retrieved 2009-09-01
- ^
Valin, Jean-Marc; Vos, Koen (24 September 2010).
"Definition of the Harmony Audio Codec"
.
IETF Datatracker
.
- ^
Jean-Marc Valin, Koen Vos & Timothy B. Terriberry (September 2012).
"Definition of the Opus Audio Codec"
.
RFC 6716
. IETF
. Retrieved
2013-08-19
.
- ^
"Skype and a New Audio Codec"
. Microsoft. September 12, 2012. Archived from
the original
on October 18, 2017
. Retrieved
October 25,
2023
.
- ^
PCWorld (2009-02-04)
Skype Upgrade Simplifies VoIP Video Calls
, Retrieved 2009-09-01
- ^
(2009-02-04)
Skype 4.0 audio: smooth as SILK
Archived
2012-07-22 at the
Wayback Machine
, Retrieved 2009-09-01
- ^
"Team Fortress 2 - Hatless Update"
.
www.teamfortress.com
.
- ^
Marczak, Bill; Scott-Railton, John (3 April 2020).
"Move Fast and Roll Your Own Crypto: A Quick Look at the Confidentiality of Zoom Meetings"
.
External links
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