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

Karl-Heinz Brandenburg

Ernst Eberlein

Thomas Sporer

Dieter Seitzer

Heinz Gerhauser

Bernhard Grill

Harald Popp

Christian Schmidmer

Michael Keyhl

Bernd Kurten

Jurgen Herre

Method for the cascaded coding and decoding of audio data

A process for reducing data in the transmission and/or storage of digital signals of several interdependent channels is described. As the signals from the channels are not independent of one another, an additional data quantity reduction is possible during transmission. In known processes for the coding of signals from two stereo channels, in the case of an unfavorable signal composition interference can be caused by the coding process and cannot be concealed by the signal actually present in the channel and consequently reduce listening enjoyment. In the process according to the invention and with the aid of the spectral values of corresponding blocks of several channels, there is a balancing of the necessary data rate for a separate coding of the two channels and for a joint coding. There is a joint coding of the channels for as long as the data rate for the joint coding does not exceed by a predeterminable value the data rate for the separate coding of the particular channel. In this case the spectral values of the corresponding blocks are similar, so that a joint coding is preferred. In the case of highly dissimilar signals the balancing leads to a separate transmission of the signals. In order to ensure that there is no interference, temporarily no use is made of the joint coding of several channels.

Process for reducing data in the transmission and/or storage of digital

A digital encoding process for transmitting and/or storing acoustical sigs and, in particular, music signals, in which scanned values of the acoustical signal are transformed by means of a transformation or a filter bank into a sequence of second scanned values, which reproduce the spectral composition of the acoustical signal, and the sequence of second scanned values is quantized in accordance with the requirements with varying precision and is partially or entirely encoded by an optimum encoder, and in which a corresponding decoding and inverse transformation takes place during the reproduction. An encoder is utilized in a manner in which the occurrence probability of the quantized spectral coefficient is correlated to the length of the code in such a way that the more frequently the spectral coefficient occurs, the shorter the code word. A code word and, if needed, a supplementary code is allocated to several elements of the sequence or to a value range in order to reduce the size of the table of the encoder. A portion of the code words of variable length are arranged in a raster, and the remaining code words are distributed in the gaps still left so that the beginning of a code word can be more easily found without completely decoding or in the event of faulty transmission.

Digital encoding process

Process for simultaneous transmission of signals from N signal sources

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Erlangen, Germany

Karl-Heinz Brandenburg