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

Other

Bodo Teichmann

Bernhard Grill

Karlheinz Brandenburg

J&uuml;rgen Herre

Martin Dietz

Manfred Lutzky

Ralph Sperschneider

Heinz Gerhauser

Oliver Kunz

Uwe Gbur

Nikolaus Rettelbach

Michael Schug

Jurgen Herre

Juergen Herre

James David Johnston

Heinz Gerh&auml;user

Michael Beer

Klaus Peichl

For determining a quantizer step size for quantizing a signal including audio or video information, a first quantizer step size as well as an interference threshold are provided. Then, the actual interference introduced by the first quantizer step size is determined and compared with the interference threshold. Despite the fact that the comparison reveals that the actually introduced interference exceeds the threshold, a second, coarser quantizer step size is nevertheless used, which will then be used for quantization if it turns out that the interference introduced by the coarser, second quantizer step size falls below the threshold or falls below the interference introduced by the first quantizer step size. Thus, the quantization interference is reduced while the quantization is coarsened and, thus, the compression gain is increased.

Apparatus and method for determining a quantizer step size

In a method for generating a scalable data stream, when a block of output data of a first encoder is present, this block of output data is written into the scalable data stream. If output data of a second encoder is present for a preceding period of time, this output data for the preceding section is written in transmission direction behind the block of output data of the first encoder into the data stream. When the output data of the scalable encoder for the current section is present, the output data of the second encoder is written into the bit stream subsequent to the output data of the first encoder. A determining data block is generated and written into the bit stream delayed by a period of time which corresponds to the size of the bit savings bank of the second encoder. Finally, buffer information is written into the bit stream, which indicates, where the beginning of the output data of the second encoder for the current section regarding the determining data block is, wherein the buffer information corresponds to the bit savings bank level. Thus, it is possible to simply signalize a bit savings bank in a scalable data stream. The maximum size of the bit savings bank may further be adjusted depending on the intended decoder delay and be communicated to a decoder by positioning the determining data block in the scalable data stream without an effort of additional bits in order to reduce the initial delay of the decoder.

Method and device for the generation or decoding of a scalable data stream with provision for a bit-store, encoder and scalable encoder

In a method for generating a scalable data stream from one or several blocks of output data of a first encoder and from one or several blocks of output data of a second encoder a determining data block for a current section of an input signal is written. In addition, output data of the second encoder representing a preceding section of the input signal are written in transmission direction from an encoder to a decoder after the determining data block. When the output data of the second encoder are written for a preceding section of the input signal, the output data of the second encoder are written representing the current section of the input signal. In order to signalize where the output data of the second encoder for the preceding section end and where the output data of the second encoder for the current section begin, buffer information is written into the scalable data stream. By the fact that output data of a preceding section follow a determining data block for the current section, a bit savings bank function may be implemented in the scalable encoder and simply be signalized in the bit stream.

Method and device for generating a scalable data stream and method and device for decoding a scalable data stream with provision for a bit saving bank function

In a method of producing a scalable data stream of at least two blocks of output data of a first coder and a block of output data of a second coder, wherein the at least two blocks of output data of the first coder together represent a current section of an input signal in the first coder, and wherein the block of output data of the second coder represents the same current section of the input signal, a determination data block for the current section of the input signal is written. In addition, the block of output data of the second coder, in the direction of transfer from a coding device to a decoding device, is written after the determination data block for the current section of the input signal. In addition, at least one block of output data of the first coder, in the direction of transfer, is written in front of the determination data block of the current section of the input signal, whereupon offset information is written into the scalable data stream indicating that the at least one block of output data of the first coder, in the direction of transfer, is in front of the determination data block. Thus a low-delay transfer and decoding of only the first scaling layer can be obtained.

Method and device for the generation of a scalable data stream and method and device for decoding a scalable data stream

In a device for processing a stereo audio signal having a first channel and a second channel the stereo signal is at first analyzed to obtain a measure for a quantity of bits required by a coder to code the stereo audio signal using a coding algorithm. The first channel and the second channel are then modified when the measure for the quantity of bits is larger than a predetermined value, the modification being performed in such a way that the energy of a sum signal of the first and the second modified channel is in a predetermined relation to the energy of a sum signal of the first and the second channel and that a difference signal of the first and the second modified channel is attenuated in contrast to the difference signal of the first and the second channel. Especially for audio coders requiring a constant output bit rate the side channel is attenuated in the case of stereo audio signals, the coding of which cannot meet the output bit rate of the coder, by which a stereo channel separation is abandoned for the benefit of an increased audio bandwidth or a reduction of quantizing disturbances, respectively.

Method and device for processing a stereo audio signal

A method of coding stereo audio spectral values first carries out grouping of those values in scale factor bands, with which scale factors are associated. Sections are formed next, each comprising at least one scale factor band. The spectral values are coded within at least one section with a code book assigned to the section, out of a plurality of code books each with a code book number assigned to it, the number of the code book used being transmitted as side information to the coded stereo audio spectral values. At least one additional code book number is provided, which does not refer to a code book but shows information relevant to the section to which it is assigned. A method of decoding stereo audio spectral values which are partly coded by the intensity stereo process and which have side information uses the relevant information, showing the additional code book numbers, to cancel the existing coding of the stereo audio spectral values.

Process for coding and decoding stereophonic spectral values

In a method for signalling a noise substitution when coding an audio signal, the time-domain audio signal is first transformed into the frequency domain to obtain spectral values. The spectral values are subsequently grouped together to form groups of spectral values. On the basis of a detection establishing whether a group of spectral values is a noisy group or not, a codebook is allocated to a non-noisy or tonal group by means of a codebook number for redundancy coding of the same. If a group is noisy, an additional codebook number which does not refer to a codebook is allocated to it in order to signal that this group is noisy and therefore does not have to be redundancy coded. By signalling noise substitution by means of a Huffman codebook number for noisy groups of spectral values, which are e.g. sections made up of scale factor bands which do not have to be redundancy coded, an opportunity is provided to indicate the presence of a noise substitution in a scale factor band in the bit stream syntax of the MPEG-2 Advanced Audio Coding (AAC) Standard without having to interfere with the basic coding structure and without having to meddle with the structure of the existing bit stream syntax.

Method for signalling a noise substitution during audio signal coding

A method of coding a time-discrete stereo signal, the stereo signal having a first and a second channel, permits scalable stereo coding. At first, a mono signal is formed from the stereo signal, which is then coded, whereupon the coded mono signal is transmitted to a bit stream. Thereafter, the coded mono singal is decoded again, whereupon stereo information is formed on the basis of the coded/decoded mono signal and the first and second channels, with such stereo information being coded and being also written into the bit stream in order to obtain a bit stream comprising a complete coded monolayer as well as a layer with coded stereo information.

Apparatus and method of coding a mono signal and stereo information

The present invention permits a combination of a scalable audio coder with the TNS technique. In a method for coding time signals sampled in a first sampling rate, second time signals are first generated whose sampling rate is smaller than the first sampling rate. The second time signals are then coded according to a first coding algorithm and written into a bit stream. The coded second time signals are, however, decoded again, and, like the first time signals, transformed into the frequency domain. From a spectral representation of the first time signals, TNS prediction coefficients are calculated. The transformed output signal of the coder/decoder with the first coding algorithm, like the spectral representation of the first time signal, undergoes a prediction over the frequency to obtain residual spectral values for both signals, though only the prediction coefficients calculated on the basis of the first time signals are used. These two signals are evaluated against each other. The evaluated residual spectral values are then coded by means of a second coding algorithm to obtain coded evaluated residual spectral values, which, together with the side information containing the calculated prediction coefficients, are written into the bit stream.

Method and a device for coding audio signals and a method and a device for decoding a bit stream

A method for coding or decoding an audio signal combines the advantages of TNS processing and noise substitution. A time-discrete audio signal is initially transformed to the frequency domain in order to obtain spectral values of the temporal audio signal. Subsequently, a prediction of the spectral values in relation to frequency is carried out in order to obtain spectral residual values. Within the spectral residual values, areas are detected encompassing spectral residual values with noise properties. The spectral residual values in the noise areas are noise-substituted, whereupon information concerning the noise areas and noise substitution is incorporated into side information pertaining to a coded audio signal. Thus, considerable bit savings in case of transient signals can be achieved.

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Fuerth, Germany

Bodo Teichmann