SVOPC (Sinusoidal Voice Over Packet Coder) is a compression method for audio which is used by

VOIP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...

applications. It is a

lossy In information technology, lossy compression or irreversible compression is the class of data compression methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size ...

speech compression

codec A codec is a device or computer program that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or ...

designed specifically towards communication channels suffering from

packet loss Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is either caused by errors in data transmission, typically across wireless networks, or network congestion.Kur ...

. It uses more bandwidth than best bandwidth-optimised codecs, but it is

resistant instead. Skype Limited developed a codec called 'SVOPC' for Skype. It was first used in Skype 3.2 beta 53, released on March 28, 2007.Skype Community (2008-07-29
Current codec uses
(Internet Archive)Skype Journal (2007-03-28

Retrieved 2009-09-01Lee S. Dryburgh (2008-02-06

eComm Media, Inc. Retrieved 2009-09-01Michael Stanford (2009-01-13
Skype’s new super-wideband codec (SILK)
Wirevolution, Retrieved 2009-09-01 Starting with Skype 4.0, SVOPC is replaced by

SILK Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the ...

Technical information

Operation is quasi-harmonic modelling of the

linear prediction Linear prediction is a mathematical operation where future values of a discrete-time signal are estimated as a linear function of previous samples. In digital signal processing, linear prediction is often called linear predictive coding (LPC) and ...

residual. The codec uses a 16 kHz

sample rate In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples". A sample is a value of the signal at a point in time and/or spa ...

and allows for 8 kHz of audio

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

. SVOPC provides synthesized speech of good subjective quality at around 20 kbit/s. Because the compression relies on

floating point In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can b ...

mathematics it can be inefficient when it's running in an

embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...

as this will likely not offer the same kind of floating point capabilities as, say, a PC. The new codec

has been designed with this in mind.

References

Sources

* Dryburghon, L.
"Interview with Jonathan Christensen, General Manager of Skype, about SVOPC Audio"
* Lindblom, J.
"Sinusoidal Voice Over Packet Coder Tailored for the Frame-Erasure Channel"
* Stanford, M.
"Skype’s new super-wideband codec"
Skype Audio codecs Speech codecs {{multimedia-software-stub

Technical information

See also

References

Sources