Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V.

Ali Nowbakht-Irani

Martin Dietz

Ralph Sperschneider

Karlheinz Brandenburg

Heinz Gerhaeuser

Oliver Kunz

Roland Bitto

Pierre Lauber

In a method for coding an audio signal to obtain a coded bit stream, discrete-time samples of the audio signal are transformed into the frequency domain to obtain spectral values. The spectral values are coded with a code table having a limited number of code words of different lengths to obtain spectral values coded by code words, the length of a code word assigned to a spectral value being that much shorter the higher the probability of occurrence of the spectral value is. A raster is then specified for the coded bit stream, the raster having equidistant raster points and the distance between the raster points depending on the code table(s) used. In order to obtain error-tolerant Huffman coding, priority code words, which represent particular spectral values which are psychoacoustically more important than other spectral values, are so arranged in the raster that the start of each priority code word coincides with a raster point.

Methods and devices for coding or decoding an audio signal or bit stream

A method and a device for entropy encoding and associated decoding make use of a code consisting on the one hand of a code table with reversible code words ( ) and comprising on the other hand an escape region for information words to be coded which are located outside the region ( ) defined by said code table. Said region can be selected in such a way that a major part of the information words is coded with symmetrical code words by the code table. On the one hand, it is thus possible to carry out, in addition to forward decoding, also backward decoding ( ) and on the other hand, use of reversible code words allows for rapid recognition of errors in a code word stream transmitted over a non-ideal channel.

Device and method for entropy encoding of information words and device and method for decoding entropy-encoded information words

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Erlangen, Germany

Ali Nowbakht-Irani