Sampling Frequency (Fs)
Defines the rate in Hertz which is used to digitise an audio signal during the sampling process.

SAOL (Structured Audio Orchestra Language)
SAOL is a powerful, flexible language for describing music synthesis, and integrating synthetic sound with "natural" (recorded) sound in an MPEG-4 bitstream. It is designed for very low bitrate files.

Scalability is the ability of a decoder to decode an ordered set of bitstreams to produce a reconstructed sequence. Moreover, useful signal is output when subsets are decoded. The minimum subset that can thus be decoded is the first bitstream in the set which is called the base layer. Each of the other bitstreams in the set is called an enhancement layer. When addressing a specific enhancement layer, lower layer refer to the bitstream which precedes the enhancement layer.

Factor by which a set of values is scaled before quantization.

Scalefactor band
A set of spectral coefficients which are scaled by one scalefactor.

Scalefactor index
A numerical code for a scalefactor.

Side information
Information in the bitstream necessary for controlling the decoder.

SNR scalability
A type of scalability where the enhancement layer(s) contain only coded refinement data for the DCT coefficients of the base layer.

Spectral coefficients
Discrete frequency domain data output from the analysis filterbank.

Spreading function
A function that describes the frequency spread of masking effects.

Standard bodies
Any country have national standard body where experts from industry and universities develop standards for all kinds of engineering problems. Among them are, for instance,
ANSI American National Standards Institute USA
DIN Deutsches Institut fuer Normung Germany
BSI British Standards Institution United Kingdom
AFNOR Association francaise de normalisation France
UNI Ente Nazionale Italiano di Unificazione Italy
NNI Nederlands Normalisatie-instituut Netherlands
SAA Standards Australia Australia
SANZ Standards Association of New Zealand New Zealand
NSF Norges Standardiseringsforbund Norway
DS Dansk Standard Denmark
and about 80 others.
    The International Organization for Standardization, ISO, in Geneva is the head organization of all these national standardization bodies. Together with the International Electrotechnical Commission, IEC, ISO concentrates its efforts on harmonizing national standards all over the world. The results of these activities are published as ISO standards. Among them are, for instance, the metric system of units, international stationery sizes, all kinds of bolt nuts, rules for technical drawings, electrical connectors, security regulations, computer protocols, file formats, bicycle components, ID cards, programming languages, International Standard Book Numbers (ISBN).
     Over 10,000 ISO standards have been published so far and you surely get in contact with a lot of things each day that conform to ISO standards you never heard of. By the way, ISO is not an acronym for the organization in any language. It's a wordplay based on the English/French initials and the Greek-derived prefix iso- meaning same.
    Within ISO, ISO/IEC Joint Technical Committee 1 (JTC1) deals with information technology.
    The International Telecommunication Union, ITU, is the United Nations specialized agency dealing with telecommunications. At present there are 164 member countries. One of its bodies is the International Telegraph and Telephone Consultative Committee, CCITT. A Plenary Assembly of the CCITT, which takes place every few years, draws up a list of 'Questions' about possible improvements in international electronic communication. In Study Groups, experts from different countries develop 'Recommendations' which are published after they have been adopted. Especially relevant to computing are the V series of recommendations on modems (e.g. V.32, V.42), the X series on data networks and OSI (e.g. X.25, X.400), the I and Q series that define ISDN, the Z series that defines specification and programming languages (SDL, CHILL), the T series on text communication (teletext, fax, videotext, ODA) and the H series on digital sound and video encoding.
    Since 1961, the European Computer Manufacturers Association, ECMA, has been a forum for data processing experts where agreements have been prepared and submitted for standardization to ISO, CCITT and other standards organizations.

A portion of a stereophonic audio signal which does not contribute to spatial perception.

An ordered series of bits that forms the coded representation of the data.

Streaming audio
Streaming refers to the playback of audio in real-time as it is transferred across the Internet. The advantage of this approach is that the user does not have wait for the entire music file to be downloaded before hearing it. The tradeoff is that the music must be highly compressed in order to support the access rates that most users have, typically 28.8 to 56 Kbps. This gives internet users instant gratification but relatively poor playback quality. In addition streaming audio players do not capture the content, so each time the clip is played it is transferred again.

Stuffing (bits/bytes)
Code-words that may be inserted at particular locations in the coded bitstream that are discarded in the decoding process. Their purpose is to increase the bitrate of the stream which would otherwise be lower than the desired bitrate.

Surround channel
An audio presentation channel added to the front channels (L and R or L, R, and C) to enhance the spatial perception.

Synthesis filterbank
Filterbank in the decoder that reconstructs a PCM audio signal from subband samples.

© 1999-2000 Gabriel Bouvigne for MP3'Tech - www.mp3tech.org