SVOPC is a compression method for audio which is used by applications such as Skype

Skype

Skype is a software application that allows users to make voice and video calls and chat over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system...

. It is a lossy speech compression

Speech encoding

Speech coding is the application of data compression of digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic data compression algorithms to represent the resulting...

 codec

Codec

A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...

 designed specifically towards communication channels suffering from packet loss

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 distinguished as one of the three main error types encountered in digital communications; the other two being bit error and spurious packets caused due to noise.-...

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

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 distinguished as one of the three main error types encountered in digital communications; the other two being bit error and spurious packets caused due to noise.-...

 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.

Technical Information

Operation is quasi-harmonic modelling of the linear prediction

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....

 residual.

The codec uses a 16 kHz sample rate and allows for 8 kHz of audio bandwidth. SVOPC provides synthesized speech of good subjective quality at around 20 kbit/s.

Because the compression relies on floating point

Floating point

In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...

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

Embedded system

An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...

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

Silk

Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...

has been designed with this in mind.

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"