Abstract: In a method for producing a data stream of code words of variable lengths which are divided up into a plurality of sets of code words, wherein a raster having segments is specified for the data stream, wherein two adjacent raster points define a segment, code words of the first sets are written into the data stream starting at raster points. Subsequently, code words of the second set are written into the data stream pursuant to a predetermined assignment rule, wherein each code word of the second set is assigned to a different segment. Entire code words or parts of code words which cannot be written according to their assignment, are stored and entered into the data stream in further attempts, wherein the assignment by a predetermined regulation is changed from attempt to attempt. This procedure is analogously repeated for any further set which may be present.

Abstract: When encoding an audio signal, the audio signal is first encoded with the first encoder to obtain a first encoder output signal. This first encoder output signal is written into a bit stream. It is further decoded by a decoder to provide a decoded audio signal. The decoded audio signal is compared with the original audio signal to obtain a residual signal. The residual signal is then encoded via a second encoder to provide a second encoder output signal which is also written into a bit stream. The first encoder has a first time or frequency resolution. The second encoder has a second time or frequency resolution. The first resolution differs from the second resolution, so that in a respective decoder, an audio signal with both a high time resolution as well as a high frequency resolution can be retrieved.

Abstract: An apparatus for encoding an audio signal to obtain an encoded audio signal to be used by a decoder having a high frequency reconstruction module for performing a high frequency reconstruction for a frequency range above a crossover frequency includes, a core encoder for encoding a lower frequency band of the audio signal up to the crossover frequency, the crossover frequency being variable, and the core encoder being operable on a block-wise frame by frame basis, and a crossover frequency control module for estimating, dependent on a measure of the degree of difficulty for encoding the audio signal by the core encoder and/or a boarder between a tonal and a noise-like frequency range of the audio signal, the crossover frequency to be selected by the core encoder for a frame of a series of subsequent frames, so that the crossover frequency is variable adaptively over time for the series of subsequent frames.

Abstract: An apparatus for analyzing an analysis time signal that has been generated from encoding and decoding an original time signal according to an encoding algorithm first, wherein first the encoding block raster underlying the analysis time signal used by the encoding algorithm is determined. Thereupon, the analysis time signal will be converted from its timely representation comprising a plurality of analysis spectral coefficients, to a spectral representation by using the established encoding block raster. Then, at least two analysis spectral coefficients or at least two spectral coefficients derived from the analysis spectral coefficients by multiplication of an encoding amplification factor or by multiplication with a compression function are grouped.

Abstract: In determining a coding block raster on which a decoded signal is based, a segment of the decoded signal is picked out first, said segment beginning at a certain output sampling value of the decoded signal. Said segment is then converted into a spectral representation, whereupon said spectral representation is then evaluated in relation to a predetermined criterion in order to obtain an evaluation result for the segment. This procedure is repeated for a plurality of different segments beginning at different output sampling values each, in order to obtain a plurality of evaluation results. Finally, the plurality of the evaluation results is searched in order to establish the evaluation result that has an extreme value as compared to the other evaluation results, in such a way that it can be assumed that the segment to which this evaluation result is allocated matches the coding block raster on which the decoded signal is based.

Abstract: In determining a coding block raster on which a decoded signal is based, a segment of the decoded signal is picked out first (11), said segment beginning at a certain output sampling value of the decoded signal. Said segment is then converted into a spectral representation (12), whereupon said spectral representation is then evaluated in relation to a predetermined criterion (13) in order to obtain an evaluation result for the segment. This procedure is repeated for a plurality of different segments beginning at different output sampling values each, in order to obtain a plurality of evaluation results. Finally, the plurality of the evaluation results is searched (14) in order to establish the evaluation result that has an extreme value as compared to the other evaluation results, in such a way that it can be assumed that the segment to which this evaluation result is allocated matches the coding block raster on which the decoded signal is based.

Abstract: The present invention relates to digital audio coding systems that employ high frequency reconstruction (HFR) methods. It teaches how to improve the overall performance of such systems, by means of an adaption over time of the crossover frequency between the lowband coded by a core codec, and the highband coded by an HFR system. Different methods of establishing the instantaneous optimum choice of crossover frequency are introduced.