Decoder, encoder, method, data stream for coding a multi-channel waveform signal

Abstract

An apparatus and method for coding a multi-channel waveform signal from or into a data stream using block-based prediction is presented. The apparatus is configured to decode from the data stream a commonality syntax element indicating for a plurality of channels of the multi-channel waveform signal, whether, among a set of prediction modes supported by the apparatus, one prediction mode is commonly attributed to the plurality of channels, if the commonality syntax element indicates that one prediction mode is commonly attributed to the plurality of channels, decode a set of one or more prediction mode syntax elements from the data stream which indicate a selected prediction mode out of the set of prediction modes, wherein the selected prediction mode is the one prediction mode, or appoint a selected prediction mode indicated by a set of one or more prediction mode syntax elements decoded for a first channel among the plurality of channels the one prediction mode, or use a default prediction mode among the set of prediction modes as the one prediction mode, and decode each of the plurality of channels using the one prediction mode, and, if the commonality syntax element does not indicate that one prediction mode is commonly attributed to the plurality of channels, decode, from the data stream, for each of the plurality of channels, the set of one or more prediction mode syntax elements, which indicate a selected prediction mode out of the set of prediction modes for the respective channel, and decode each of the plurality of channels using the selected prediction mode for the respective channel.

Description

[0001] Decoder, Encoder, method, data stream for coding a multi-channel waveform signal

[0002] Description

[0003] Technical field

[0004] Embodiments relate to decoders, encoders, methods for decoding, methods for encoding, computer programs and data streams pertaining to coding of a multi-channel waveform signal. Embodiments may also be titled “Efficient waveform coding”.

[0005] Background

[0006] There are many applications, that generate waveform signals, such as biophysical, geophysical, or acoustic signals. Such signals can be encoded into and decoded from a data stream, e.g., for more efficient storage and / or transmission. With increasing amount of available data, there is a demand for improved coding efficiency.

[0007] This is achieved by the subject matter of the independent claims of the present application. Further embodiments according to the invention are defined by the subject matter of the dependent claims of the present application.

[0008] Summary of the invention

[0009] In accordance with a first aspect of the invention, an apparatus for decoding a multi-channel waveform signal from a data stream using block-based prediction is provided. The apparatus is configured to decode from the data stream a commonality syntax element indicating for a plurality of channels of the multi-channel waveform signal, whether, among a set of prediction modes supported by the apparatus, one prediction mode is commonly attributed to the plurality of channels, if the commonality syntax element indicates that one prediction mode is commonly attributed to the plurality of channels, decode a set of one or more prediction mode syntax elements from the data stream which indicate a selected prediction mode out of the set of prediction modes, wherein the selected prediction mode is the one prediction mode, or appoint a selected prediction mode indicated by a set of one or more prediction mode syntax elements decoded for a first channel among the plurality of channels the one prediction mode, or use a default prediction mode among the set of prediction

[0010] FH241108PEP-2025376085fe modes as the one prediction mode, and decode each of the plurality of channels using the one prediction mode, and if the commonality syntax element does not indicate that one prediction mode is commonly attributed to the plurality of channels, decode, from the data stream, for each of the plurality of channels, the set of one or more prediction mode syntax elements, which indicate a selected prediction mode out of the set of prediction modes for the respective channel, and decode each of the plurality of channels using the selected prediction mode for the respective channel.

[0011] An encoder (e.g., apparatus that encoded the bit stream) may efficiently signal common prediction mode for plurality of channels. Additional overhead is more than compensated by necessitating the signaling of the set of one or more prediction mode syntax elements merely once in cases of commonality. In case of a communality of a prediction mode, a transmission of the prediction modes of individual channels may not be required any longer. For example, a communality of a prediction mode may occur by coincidence (e.g., an encoding apparatus determined for each channel that a certain prediction mode is optimal, which happened to be the same for all channels), and / or may be considered by the encoding apparatus, e.g., in order to reduce coding complexity or improve coding efficiency (e.g., based on a rate-distortion algorithm). Furthermore, a plurality of channels may be established based on a channel grouping, which may result in similar channels being grouped together. As a result, the probability of a same prediction mode being viable may increase, which can be exploited by signaling the commonality syntax element. The prediction mode can be signaled directly for the plurality of channels or for the first channel. The prediction mode may even be set by a default mode, e.g., automatically in case of a communality, which can further reduce the amount of signaled data. In cases of communality, other coding techniques such as prediction (e.g., prediction based on already decoded residuals) may yield different or better results. Therefore, the commonality syntax element may also form a parameter that influences or implicitly signals prediction parameters. In case the channels are to be decoded with different prediction modes, the apparatus can accordingly be informed based on the commonality syntax element (e.g., using the communality syntax element for implicit signaling, e.g., of prediction modes and / or prediction parameters). The concept of communality may even be extended to parameters of the prediction mode (e.g., in case the common prediction mode is parametrizable), which may further improve coding efficiency.

[0012] According to a second aspect, an apparatus for decoding a multi-channel waveform signal from a data stream using block-based prediction, inter-channel transform-domain residual

[0013] FH241108PEP-2025376085fe prediction and transform-based prediction residual decoding is provided. The apparatus is configured to decode from the data stream a further commonality syntax element indicating for a plurality of channels of the multi-channel waveform signal, whether, among a set of transform domains supported by the apparatus, one transform domain is commonly attributed to the plurality of channels, if the further commonality syntax element indicates that one transform domain is commonly attributed to the plurality of channels, decode each of the plurality of channels using the one transform domain for the transform-based prediction residual decoding, and if the further commonality syntax element does not indicate that one transform domain is commonly attributed to the plurality of channels, decode each of the plurality of channels using a selected transform domain, which is channel-individually selected out of the set of transform domains, for the transform-based prediction residual decoding.

[0014] An apparatus for encoding may efficiently achieve transform equality thereby yielding a more effective singling which likely efficiently takes advantage from inter-channel transformdomain residual prediction. Similar to the case of prediction mode communality described above, signaling a common transform domain may require no additional signaling of transform domains for each individual channel. Communality of transform domain may be the result of random communality and / or communality for coding efficiency (e.g., based on a rate distortion algorithm). Furthermore, a common transform domain may affect or influence further predictions, rendering the further commonality syntax element a useful tool for implicit signaling (e.g., implicit signaling of a prediction mode, prediction communality, or prediction parameters).

[0015] According to a third aspect, an apparatus for decoding a waveform signal from a data stream is provided. The apparatus is configured to perform sample-to-sample prediction for a block of the waveform signal, to obtain a preliminary time-domain block predictor; spectrally filter the preliminary time-domain predictor to obtain a filtered time-domain block predictor; perform transform-domain-to-transform-domain prediction for the block of the waveform signal to obtain a transform-domain predictor; decode a residual spectrum from the data stream, correct the transform-domain predictor using the residual spectrum to obtain a corrected residual spectrum, subject the corrected residual spectrum to a re-transfor- mation to obtain a time-domain residual signal; correct the time-domain block predictor using the time-domain residual signal, wherein the apparatus is configured to perform the spectrally filtering the preliminary time-domain predictor using a transfer function being higher in a first spectral region than compared to a second spectral region, and perform the

[0016] FH241108PEP-2025376085fe transform-domain-to-transform-domain prediction spectrally restricted to the second spectral region, or by obtaining a preliminary transform-domain predictor and spectrally filtering the preliminary transform-domain predictor using a transfer function being higher in the second spectral region than compared to the first spectral region to obtain the transform-do- main predictor; or by performing filter synthesis using an impulse response which is higher in the second spectral region than compared to the first spectral region.

[0017] The apparatus therefore provides two types of predictions in form of sample-to-sample prediction and transform-domain-to-transform domain prediction. The preliminary time-predictor of the sample-to-sample prediction is spectrally filtered to be higher in the first spectral region, whereas the transform-domain-to-transform-domain prediction is processed with an emphasis on the second spectral region. As a result, the two predictions can be processed to have an emphasis on different spectral regions. Therefore, the predictions can be adjusted, e.g., for higher coding efficiency. It has been recognized that for many applications, it can be more beneficial (e.g., in terms of improving prediction, e.g., thusly improving coding efficiency), if the first spectral region is located at lower frequencies than the second spectral regions. Such different spectral regions can be realized by the third aspect. A restriction of the transform-domain-to-transform-domain prediction to the second spectral region may reduce coding complexity. Using a transfer function that is higher in the second spectral region or performing filter synthesis using an impulse response which is higher in the second spectral range may improve prediction accuracy.

[0018] Furthermore, according to the first, second, and third aspect, respectively, a corresponding apparatus for encoding, an encoded data stream, encoding and decoding methods and a computer program for said methods are provided.

[0019] Brief Description of the Drawings

[0020] The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings, in which:

[0021] Fig. 1 shows a schematic view of an apparatus for decoding a multi-channel waveform signal from a data stream using block-based prediction;

[0022] Fig. 2 shows a schematic view of another example of the apparatus;

[0023] FH241108PEP-2025376085fe Fig. 3 shows a schematic view of an example of a plurality of channels;

[0024] Fig. 4 shows a schematic view of an apparatus for encoding a multi-channel waveform signal into a data stream using block-based prediction;

[0025] Fig. 5 shows a schematic view of another example of the apparatus;

[0026] Fig. 6 shows an apparatus for decoding a multi-channel waveform signal from a data stream using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual decoding;

[0027] Fig. 7 shows another example of an apparatus for decoding a multi-channel waveform signal;

[0028] Fig. 8 shows a schematic view of an apparatus for encoding a multi-channel waveform signal into a data stream using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual encoding;

[0029] Fig. 9 shows another example of an apparatus for encoding a multi-channel waveform signal into a data stream using block-based prediction;

[0030] Fig. 10 shows a schematic view of an apparatus for decoding a waveform signal from a data stream;

[0031] Fig. 11 shows a schematic view of a sample-to-sample prediction of a block;

[0032] Fig. 12a shows a first example of a first and second spectral region;

[0033] Fig. 12b shows a second example of a first and second spectral region;

[0034] Fig. 12c shows a third example of a first and second spectral region;

[0035] Fig. 12d shows a fourth example of a first and second spectral region;

[0036] FH241108PEP-2025376085fe Fig. 13 shows a schematic view of an apparatus for encoding a waveform signal into a data stream;

[0037] Fig. 14 shows a flow diagram of a method for decoding a multi-channel waveform signal from a data stream using block-based prediction;

[0038] Fig. 15 shows a flow diagram of a method for decoding a multi-channel waveform signal into a data stream using block-based prediction;

[0039] Fig. 16 shows a flow diagram of a method for decoding multi-channel waveform signal from a data stream using block-based prediction, inter-channel trans- form-domain residual prediction and transform-based prediction residual decoding;

[0040] Fig. 17 shows a flow diagram of a method encoding a multi-channel waveform signal into a data stream using block-based prediction, inter-channel transform-do- main residual prediction and transform-based prediction residual encoding;

[0041] Fig. 18 shows a flow diagram of a method for decoding a waveform signal from a data stream;

[0042] Fig. 19 shows a flow diagram of a method for encoding a waveform signal into a data stream;

[0043] Fig. 20 shows an exemplary signaling configuration for one prediction mode is commonly attributed to the plurality of channels; and

[0044] Fig. 21 shows an exemplary framework of an encoder for encoding a multi-channel digital signal into a data stream as well as decoder for decoding the multichannel digital signal from data stream.

[0045] Detailed of the Embodiments

[0046] FH241108PEP-2025376085fe Equal or equivalent elements or elements with equal or equivalent functionality are denoted in the following description by equal or equivalent reference numerals even if occurring in different figures.

[0047] In the following description, a plurality of details is set forth to provide a more throughout explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form rather than in detail in order to avoid obscuring embodiments of the present invention. In addition, features of the different embodiments described herein after may be combined with each other, unless specifically noted otherwise.

[0048] Introductory remarks:

[0049] In the following different embodiments and aspects will be described (e.g., with reference to fig. 1 to 19). These embodiments can be freely combined with further embodiments described further below in sections “Summary or Outline of underlying ideas”, “Detailed Options for Signalling of Common Flags”, “Preferred Embodiment of Common Prediction Mode”, “Preferred Embodiment of Common Transform Mode”, “Alternative to Usage of Common Flags”, and “general framework”.

[0050] Also, further embodiments will be defined by the enclosed claims.

[0051] It should be noted that any embodiments as defined by the claims can be supplemented by any of the details (features and functionalities) described in the above-mentioned sections.

[0052] Also, the embodiments described in the above-mentioned sections can be used individually, and can also be supplemented by any of the features in another section, or by any feature included in the claims.

[0053] Also, it should be noted that individual aspects described herein can be used individually or in combination. Thus, details can be added to each of said individual aspects without adding details to another one of said aspects.

[0054] Moreover, features and functionalities disclosed herein relating to a method can also be used in an apparatus (configured to perform such functionality). Furthermore, any features

[0055] FH241108PEP-2025376085fe and functionalities disclosed herein with respect to an apparatus can also be used in a corresponding method. In other words, the methods disclosed herein can be supplemented by any of the features and functionalities described with respect to the apparatuses.

[0056] Moreover, features and functionalities disclosed herein relating to a method, in particular an encoding method can also be used in a data stream or bitstream (e.g. defining a respective data stream or bitstream element). Furthermore, any features and functionalities disclosed herein with respect to an apparatus can also be used in a corresponding data stream, e.g. as a resulting data stream as providing by said encoder. In other words, the data streams disclosed herein can be supplemented by any of the features and functionalities described with respect to the apparatuses and methods.

[0057] Also, any of the features and functionalities described herein can be implemented in hardware or in software, or using a combination of hardware and software, as will be described in the section “Implementation alternatives”.

[0058] In the following, three aspects are described, wherein a first aspect relates to a common prediction mode, a second aspect relates to a common transform mode, and a third aspect relates to different spectral ranges for prediction. While the three aspects can be provided in isolation, they are not exclusive to each other and are freely combinable. Therefore, any feature disclosed with reference to one of the three aspects can be combined in any feature combination with any of the other aspects. In the following, the first aspect will be described first.

[0059] Fig. 1 shows a schematic view of an apparatus 12 for decoding a multi-channel waveform signal 14 from a data stream 16 using block-based prediction.

[0060] The apparatus 12 (e.g., decoder) is configured to decode from the data stream 16 a commonality syntax element 13 (e.g. common_pred_mode, e.g., common_block_predf) indicating for a plurality of channels 21a-f (e.g., channels 21a-f of one channel group 240a) of the multi-channel waveform signal 14, whether, among a set 29 of prediction modes supported by the apparatus 12, one prediction mode 25 is commonly attributed to the plurality of channels 21a-f (e.g. relating to one temporal block 30, i.e. one set of mutually aligned blocks 140, e.g. of one channel group 240a),

[0061] FH241108PEP-2025376085fe The apparatus 12 is configured to, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly (e.g., jointly, mutually, collectively) attributed to the plurality of channels 21 a-f, decode a set 31 of one or more prediction mode syntax elements (e.g. block_pred_mode) from the data stream 16 which indicate a selected prediction mode 33 out of the set 29 of prediction modes, wherein the selected prediction mode 33 is the one prediction mode 25, or appoint a selected prediction mode 33 indicated by a set 31 of one or more prediction mode syntax elements decoded for a first channel 21a among the plurality of channels 21 a-f the one prediction mode 25, or use a default prediction 35 mode among the set 29 of prediction modes as the one prediction mode 25. The apparatus 12 is configured to decode each of the plurality of channels 21 a-f using the one prediction mode 25.

[0062] The apparatus 12 is configured to, if the commonality syntax element 13 does not indicate that one prediction mode is commonly attributed to the plurality of channels 21 -d, decode, from the data stream 16, for each of the plurality of channels 21 a-f, the set 31 of one or more prediction mode syntax elements, which indicate a selected prediction mode 39 (e.g., comprising prediction modes 39a, b, c, etc.) out of the set 29 of prediction modes for the respective channel 21 a-f, and decode each of the plurality of channels 21a-f using the selected prediction mode 39 for the respective channel 21 a-f.

[0063] The apparatus 12 may be, may comprise, or may be part of a decoder. The apparatus 12 may comprise a processor (e.g., microprocessor) configured to perform the functions (e.g., steps) of the apparatus 12. The apparatus 12 may be part of or may comprise a computer, smartphone, tablet, smart-watch, medical device, displaying device, server, or any other form of cloud computing resource. The apparatus 12 may be part of or comprise a medical device (e.g., electroencephalograph and / or electrocardiograph), a seismic device (e.g., seismograph or seismometer), or an audio processing device. The digital waveform data 14 may represent (e.g., may be or may comprise) a biometric signal (e.g., of heart, brain, or eye functions, e.g., body temperature), seismic data (e.g., amplitude of ground motion), or a sound signal (e.g., sound amplitude, e.g., of one or more audio channels). The digital waveform data 14 may be a time varying signal (e.g., in units of ms, e.g., in units of samples). A combination of an encoder and decoder may be referred to as codec. The apparatus 12 (and / or apparatus 10 described further below) may be or may be part of a codec. The term “codec” may be used herein to refer to either apparatus and may be considered a term related to a general coding concept (e.g., not necessarily limited to either of a decoder or encoder aspect).

[0064] FH241108PEP-2025376085fe In the example shown in fig. 1 , the digital waveform data 14 has seven channels 21a-g, wherein the plurality of channels 21a-f comprises six channels 21. However, the digital waveform data 14 may comprise any other number of channels (e.g., two, three, four, five, six, or more). Similarly, the plurality of channels 21a-g may comprise any other number of channels 21 (e.g., two, three, four, five, six, or more, e.g., a power of two). A channel 21 may define a single parameter assuming values over time, e.g., wherein the parameter is sampled over temporally successive samples. The channels 21 may identifiable or indexable by an identifier, e.g., seven unique identifiers for seven channels 21a-g. One or more of the channels 21a-g may have different sampling rates (e.g., number of samples per second). Similarly, different channels 21 may have the same sampling rate. The channels 21 of the plurality of channels 21a-f may have the same sampling rate and / or be of a same channel type. It is noted that herein, the plurality of channels is referenced by the reference sign 21a-f. However, this reference sign does not limit or define the number of channels 21 of the plurality of channels 21a-f.

[0065] The digital waveform data 14 may comprise one or more (e.g., two more more) channel groups 240, wherein each channel group 240 comprises one or more (e.g., two more more) channels 21. Two or more channel groups 240 may have the same number or different number of channels 21. In the example shown in fig. 1 , the digital waveform data 14 comprises a first channel group 240a that forms or comprises the plurality of channels 21 a-f and a second channel group 240b comprising channel 21 e. However, any other number of channel groups 240 and / or size of channel groups 240 may be used.

[0066] One or more (e.g., all) channels 21 may be temporally subdivided into blocks, e.g., having a common number of samples (e.g., 4, 8, 16, 32, 64 samples). The plurality of channels 21a-f may each be subdivided into blocks, e.g., having have the same number of samples. The blocks of the plurality of channels 21 a-f (and optionally of all channels) may be temporally aligned. A plurality of blocks (e.g., of the plurality of channels 21 a-f) may form a temporal block. A plurality of blocks (or a plurality of temporal blocks, e.g., of the plurality of channels 21a-f) may form a frame. For example, a frame (or a temporal block) may form a two-dimensional array of samples.

[0067] The commonality syntax element 13 may be or may comprise a (e.g., binary) flag, e.g., indicating whether or not the one prediction mode 25 is the commonly attributed to the plu-

[0068] FH241108PEP-2025376085fe rality of channels 21a-f. The commonality syntax element 13 may optionally comprise common channel identification information, which indicates the plurality of channels 21 a-f, e.g., indicating a number of channels and / or IDs of the channels 21 a-f. However, the commonality syntax element 13 may not require such an information, e.g., and only consist of a flag. For example, no further information may be required if all channels 21 of the digital waveform data 14 form the plurality of channels 21 a-f and / or if there is already a grouping channels (e.g., indicated with a different syntax element and / or based on pre-defined grouping rules). In case of already established channel groups 240, the commonality syntax element 13 may be signaled in association (e.g., interspersed within packets, e.g., indicated in a packet header) with the channels of the plurality of channels 21a-f (e.g., with or before a first channel of the plurality of channels 21 a-f).

[0069] The set 31 of one or more prediction mode syntax elements may be indicative or representative of parameters to be used for the selected prediction mode 33. For example, in the case of the selected prediction mode 33 indicating an intra-channel line-fitting prediction mode, the set 31 of one or more prediction mode syntax elements may optionally comprise parameters for defining a line for the line fit.

[0070] Decoding one or more of the channels 21 a-f may comprise one or more of decoding a residual signal (e.g. a transformed version thereof), dequantizing the residual signal, retransforming a transformed version of the residual signal, and correcting a prediction signal using the residual signal. It is noted that any correcting disclosed herein may be performed as or based as an addition, e.g., performed sample-wise of coefficient-wise.

[0071] The apparatus 12 may relate or realize an aspect of a common prediction mode. It is noted that the commonality syntax element 13 may be transmitted prior to a first set 31 of one or more prediction mode syntax elements or subsequently thereto. For example, it could also be sent in-between, e.g., in case of more than one prediction mode syntax element 31. In an example, a state of the commonality syntax element 13 indicating commonality might even be indicative of the common prediction mode.

[0072] Fig. 2 shows a schematic view of another example of the apparatus 12. The apparatus 12 may comprise any feature of function disclosed for any other apparatus 12 (or its counterpart apparatus 10 described further below).

[0073] FH241108PEP-2025376085fe Fig. 3 shows a schematic view of an example of a plurality of channels 21a-f. The plurality of channels 21a-f in fig. 3 may (or may not) be the plurality of channels 21a-f shown in fig. 1 or 2.

[0074] The apparatus 12 may be configured to derive, for each channel 21a-f of the plurality of channels, a prediction residual 200 (e.g., in fig. 3 exemplarily shown in form of a prediction for channel 21 d) by, for each of one or more dependent channels 201 (e.g., exemplarily dependent channel 201 in form of channel 21d in fig. 3) in the set of the plurality of channels 21 a-f, using inter-channel transform-domain residual prediction 204a; 204b from the prediction residual 206a; 206b of one or more reference channels 202 (e.g., in fig. 3 exemplarily reference channels 202 in form of channels 21a-c, e.g., all temporally aligned channels, e.g., a pre-determined number of channels) within the plurality of channels 21a-f to obtain a predicted transform-domain residual signal 208a; 208b, decoding a signaled transformdomain residual signal 210 (e.g., for channel 21d) from the data stream 16, correcting 212 the predicted transform-domain residual signal 208a; 208b using the signaled transformdomain residual signal 210, and correct 230, for each channel of the plurality of channels 21 a-f, a prediction signal 214 obtained by the prediction mode using which the respective dependent channel 201 (e.g., channel 21d) is decoded using the prediction residual 200 decoded for the respective channel 21 (e.g., channel 21d).

[0075] It is noted that the prediction residual 200 may be called a first prediction residual 200 and the prediction residual 206a; 206b may be called second prediction residual 206a; 206b. However, the prediction residual 200 may eventually function as a prediction residual 206a; 206b for a decoding of a block 140 later in a coding order.

[0076] The dependent channel 201 may be a currently to be decoded channel of the plurality of channels 21 a-f, for which the transform-domain residual signal 208a; 208b may be obtained from. For example, the first channel 21a may not be a dependent channel 201 if it is the first channel 21a of the plurality of channels 21a-f be decoded and transform-domain residual signal 208a; 208b were to only obtained from temporally co-located blocks 140. However, the first channel 21a may also be a dependent channel 201 , for example, if the transformdomain residual signal 208a; 208b may be obtained from temporally preceding blocks 140. Dependent channels 201 may be any channel of the plurality of channels 21 that is not a first one in a channel order 32. Dependent channels 201 may be any channel that is not a random access point. A channel may be a dependent channel on a temporal position of its

[0077] FH241108PEP-2025376085fe block 140. For example, a channel 21 may border a random access border between channels (e.g. extending horizontally in fig. 3, e.g., see random access border 98 in fig. 21), wherein the channel 21 is not treated as a dependent channel 201 when a block 140 of the channel 21 is also bordering a temporal random access border (e.g., extending vertically in fig. 3, e.g., see random access border 96 in fig. 21) and treated as a dependent channel 201 when a block 140 of the channel 21 is not bordering a temporal random access border (e.g., wherein a dependency may be established with one or more temporally preceding blocks 140).

[0078] The transform-domain may be a frequency domain, wherein, for example values (e.g., samples, e.g., sample differences) of a time-domain can be transformed to (e.g., coefficient, e.g., coefficient differences in) the transform-domain using a transform (e.g., discrete cosine transform, DCT, discrete sine transform, DST, fast Fourier transform, FFT) and vice versa using a re-transform.

[0079] The predicted transform-domain residual signal 208b may be, for example, based on a mean of one or more transform-domain residual signals of the one or more reference channels 202. For the example, the predicted transform-domain residual signal 208b may be (or may be based on) an (e.g., coefficient-wise) identical or a rescaled version of the transformdomain residual signal one reference channel 202, e.g., an, in channel order 32 and / or coding order, immediately preceding or neighboring reference channel 202. For example, the transform-domain residual signal 208b for the channel 21 d may be or may be based on the coefficients of the channel 21c, which, in channel order 32 and / or coding order, immediately precedes channel 21d. In a different example, the predicted transform-domain residual signal 208b may be (or may be based on) an (e.g., coefficient-wise) average or weighted average of transform-domain residual signals of more than one reference channel 202, e.g., more than one consecutive reference channel 202, e.g., all temporally aligned reference channels 202. For example, the transform-domain residual signal 208b for the channel 21d may be or may be based on a coefficient-wise (e.g., weighted) average the coefficients of prediction residual 206b of the channels 21a-c.

[0080] The predicted transform-domain residual signal 208b may be, for example, based on a spectrally filtered version of the one or more reference channels 202 (e.g., using a filter kernel 216). The predicted transform-domain residual signal 208b may be, for example,

[0081] FH241108PEP-2025376085fe based on both, the mean of one or more transform-domain residual signals and the spectrally filtered version of the one or more reference channels 202 (e.g., based on a coefficientwise sum or average or weighted average).

[0082] It is noted that a codec (e.g., the apparatus 12) may combine commonality signaling (e.g., as shown in fig. 1 and 2) with inter-channel transform-domain residual prediction (e.g., as shown in fig. 3). The inter-channel transform-domain residual prediction might use, for example, a spectral filtering, e.g., using a filter kernel 216 which extends from the respective dependent channel 201 (e.g., channel 21d) into one or more reference channels 202 (e.g., one or more of channels 21a-c) so as to cover already reconstructed transform coefficients 218 of these channels (i.e. dependent channel 201 and one or more reference channels 202) and the correction 212 may coefficient wise alternatingly be performed with the interchannel residual prediction while moving the filter kernel 216 spectrally as illustrated by 220, thereby reconstructing the transform coefficients of channel 201 along direction 220 (e.g., towards lower order coefficients) sequentially, or the inter-channel transform-domain residual prediction might simply copy 222 transform coefficients 218 of one or more reference channels 202. The prediction residual of any in terms of inter-channel transform-domain residual prediction independently coded channels may be decoded by using the signaled spectrum 210 directly.

[0083] The inter-channel transform-domain residual prediction may provide an advantage, wherein by rending the transmission of a common prediction mode among the channels more efficient in terms of less singling overhead, it becomes more likely to occur with the advantage that the inter-channel transform-domain residual prediction will, at higher likelihood, be efficient as the reference channel is more likely coded in same prediction mode.

[0084] The apparatus 12 may be configured to derive, for each channel 21a-f of the plurality of channels 21 a-f, a prediction residual by, for each of one or more dependent channels 201 (e.g., channels 21 a-f) in the set of the plurality of channels 21 a-f (e.g. for any non-dependent channel, a signaled transform-domain residual signal is decoded from the data stream 16 into which the prediction residual is coded without inter-channel transform-domain residual prediction), decoding an inter-channel transform-domain residual prediction syntax element 41 (e.g., a flag, e.g., in a packet header or a separate packet) from the data stream 16, if the inter-channel transform-domain residual prediction syntax element 41 is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel trans-

[0085] FH241108PEP-2025376085fe form-domain residual prediction from the prediction residual of one or more reference channels 202 within the plurality of channels 21a-f to obtain a predicted transform-domain residual signal 208a; 208b, decoding a signaled transform-domain residual signal 210 from the data stream 16 and correcting 212 the predicted transform-domain residual signal 208a; 208b using the signaled transform-domain residual signal 210, and if the inter-channel transform-domain residual prediction syntax element 41 is not indicative of the use of interchannel transform-domain residual prediction, decoding a signaled transform-domain residual signal 210 from the data stream 16 into which the prediction residual is coded without inter-channel transform-domain residual prediction, and correct 230, for each channel 21a- f of the plurality of channels 21 a-f, a prediction signal 214 obtained by the prediction mode using which the respective channel 21 a-f is decoded using the prediction residual 214 derived for the respective channel 21 a-f.

[0086] In other words, the apparatus 12 may be configured to perform or not perform the interchannel transform-domain residual prediction as described above dependent on the interchannel transform-domain residual prediction syntax element 41 . In general, the inter-channel transform-domain residual prediction may form an additional first stage for predicting a block, wherein instead of simply decoding a residual signal and using the residual signal to correct a prediction signal, the residual signal itself is formed in said first stage, wherein an additional prediction (e.g., in form of the predicted transform-domain residual signal 208a; 208b) is performed in the transform-domain and the signaled transform-domain residual signal 210 is used to correct the first stage prediction, resulting in a second stage residual signal (e.g., in form of prediction residual 200), which can subsequently be used to correct the prediction signal 214 in a second stage. The inter-channel transform-domain residual prediction syntax element 41 may form a syntax element that allows switching this first prediction stage on or off.

[0087] It is noted that the codec (e.g. apparatus 12) combines commonality signaling with interchannel transform-domain residual prediction channel-individually activatable. It is notes that, here, the dependent channels 202 may be the channels possibly coded using interchannel transform-domain residual prediction. For example, whether inter-channel trans- form-domain residual prediction is indeed used may depend on some inter-channel trans- form-domain residual prediction syntax element 41 .

[0088] One advantage may be that by rending the transmission of a common prediction mode among the channels 21 more efficient in terms of less singling overhead, it may become

[0089] FH241108PEP-2025376085fe more likely to occur with the advantage that the inter-channel transform-domain residual prediction will, at higher likelihood, be efficient as the reference channel is more likely coded in same prediction mode.

[0090] The apparatus 12 may be configured to derive, for each channel 21a-f of the plurality of channels 21 a-f, a prediction residual by, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, for each of one or more dependent channels 201 in the set of the plurality of channels 21a-f (e.g. for any non-dependent channel, a signaled transform-domain residual signal 210 may be decoded from the data stream 16 into which the prediction residual 200 is coded without interchannel transform-domain residual prediction), decoding an inter-channel transform-do- main residual prediction syntax element 41 (e.g., as described above) from the data stream 16, if the inter-channel transform-domain residual prediction syntax element 41 is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual 206a; 206b of one or more reference channels 202 within the plurality of channels 21 a-f to obtain a predicted transformdomain residual signal 208a; 208b, decoding a signaled transform-domain residual signal 210 from the data stream 16 and correcting 212 the predicted transform-domain residual signal 208a; 208b using the signaled transform-domain residual signal 210, and if the interchannel transform-domain residual prediction syntax element 41 is not indicative of the use of inter-channel transform-domain residual prediction, decoding a signaled transform-do- main residual signal 210 from the data stream 16 into which the prediction residual is coded without inter-channel transform-domain residual prediction, and if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, for each channel 21 of the plurality of channels 21 a-f, decoding a signaled transform-domain residual signal 210 from the data stream 16 into which the prediction residual is coded without inter-channel transform-domain residual prediction, and correct, for each channel 21 of the plurality of channels 21a-f, a prediction signal obtained by the prediction mode 39 using which the respective channel 21 a-f is decoded using the prediction residual derived for the respective channel 21 a-f.

[0091] It is noted, that the codec (e.g., apparatus 12) may use negative commonality signaling concurrently as means to guide dependent-channel-wise transform-domain residual prediction switch: e.g., infer that transform-domain residual prediction is off for all channels 21a-f in case of non-commonality.

[0092] FH241108PEP-2025376085fe In other words, the apparatus 12 may be configured to check based on the commonality syntax element 13, whether one prediction mode 25 is commonly attributed to the plurality of channels 21a-f. In case there is not a commonly attributed prediction mode 25, the chance that the prediction residuals of these non-common predictions being useful for interchannel transform-domain residual prediction may be low. Therefore, the apparatus 12 may then automatically skip parsing or checking for an inter-channel transform-domain residual prediction syntax element 41 , since such inter-channel transform-domain residual prediction may not be useful. As a result, an inter-channel transform-domain residual prediction syntax element 41 may be omitted, increasing overall coding efficiency. However, if one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, inter-channel transform-domain residual prediction may be more feasible, and the apparatus 12 may be configured to subsequently check for (e.g., parse, e.g., expect) an inter-channel transformdomain residual prediction syntax element 41 , which indicates whether inter-channel trans- form-domain residual prediction is to be performed.

[0093] An advantage may be that by restricting the transmission of inter-channel transform-domain residual prediction syntax elements 41 to case where commonality applies, transmission overhead may be increased, with nevertheless enabling channel wise activation of interchannel transform-domain residual prediction in case of commonality.

[0094] In the above, example, a lack of one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f is used as an indicator that inter-channel transform-domain residual prediction is, in essence skipped, wherein upon a presence of one prediction mode 25, inter-channel transform-domain residual prediction still depends on an inter-channel trans- form-domain residual prediction syntax element 41. On other words, a lack of one prediction mode 25 leads to inferral. However, in a different example, a presence of one prediction mode 25 may also infer inter-channel transform-domain residual prediction, as will be described below.

[0095] The apparatus 12 may be configured to derive, for each channel 21 of the plurality of channels 21 a-f, a prediction residual by, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, for each of one or more dependent channels 202 in the set of the plurality of channels 21 a-f (e.g. for any non-dependent channel, a signaled transform-domain residual signal 210 may be decoded from the data stream 16 into which the prediction residual 214 is coded without inter-channel

[0096] FH241108PEP-2025376085fe transform-domain residual prediction), using inter-channel transform-domain residual prediction from the prediction residual 206a; 206b of one or more reference channels 202 within the plurality of channels 21a-f to obtain a predicted transform-domain residual signal 208a; 208b, decoding a signaled transform-domain residual signal 210 from the data stream 16 and correcting the predicted transform-domain residual signal 208a; 208b using the signaled transform-domain residual signal 210, and, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, for each of the one or more dependent channels 202 in the set of the plurality of channels 21 a-f (e.g. for any non-dependent channel, a signaled transform-domain residual signal 210 may be decoded from the data stream 16 into which the prediction residual 214 is coded without inter-channel transform-domain residual prediction), decoding an inter-channel transform-domain residual prediction syntax element 41 from the data stream 16, if the inter-channel transform-domain residual prediction syntax element 41 is indicative of a use of inter-channel transform-domain residual prediction, using the interchannel transform-domain residual prediction from the prediction residual 208a; 208b of one or more reference channels 202 within the plurality of channels 21 a-f to obtain a predicted transform-domain residual signal 206a; 206b, decoding a signaled transform-domain residual signal 210 from the data stream and correcting the predicted transform-domain residual signal 208a; 208b using the signaled transform-domain residual signal 210, and if the inter-channel transform-domain residual prediction syntax element 41 is not indicative of the use of inter-channel transform-domain residual prediction, decoding a signaled trans- form-domain residual signal 210 from the data stream 16 into which the prediction residual is coded without inter-channel transform-domain residual prediction, and correct, for each channel of the plurality of channels, a prediction signal obtained by the prediction mode using which the respective channel is decoded using the prediction residual derived for the respective channel.

[0097] In other words, the apparatus 12 may be configured to perform inter-channel transformdomain residual prediction automatically or by default if one prediction mode 25 is commonly attributed to the plurality of channels 21a-f (e.g., the apparatus 12 may skip checking or parsing for an inter-channel transform-domain residual prediction syntax element 41). Therefore, coding efficiency may be improved. However, if there is no one prediction mode 25, there is still a chance that inter-channel transform-domain residual prediction, which may be determined by an apparatus for encoding (e.g., an encoder). Therefore, in case of a lack of one prediction mode 25 commonly attributed to the plurality of channels 21 a-f, the apparatus 12 may check (e.g., parse or expect) an inter-channel transform-domain residual

[0098] FH241108PEP-2025376085fe prediction syntax element 41 , which indicates whether to perform inter-channel transformdomain residual prediction.

[0099] It is noted that the codec (e.g., apparatus 12) may use confirmative commonality signaling concurrently as means to infer that dependent transform-domain residual prediction is on (e.g., switched on, e.g., to be performed) for all channels (e.g., dependent channels 202, e.g., channels 21a-f) in case of commonality.

[0100] An advantage may be that by restricting the transmission of inter-channel transform-domain residual prediction syntax elements 41 to case where commonality does not apply, transmission overhead may be tailored to cases where the activation of inter-channel transformdomain residual prediction is less likely to apply while exploiting that inter-channel trans- form-domain residual prediction is likely to be useful in case of commonality.

[0101] The two examples above, in essence, define whether inter-channel transform-domain residual prediction is or is not performed by default in case of communality. Which one of the two examples (e.g., which one the two default cases of inter-channel transform-domain residual prediction) is not be used may be defined in a pre-determined rule or may be signaled. For example, which default case is to be used may be signaled, for example, once at the start of the bitstream 16 and / or at regular intervals.

[0102] The apparatus 12 may be configured to subject a corrected transform-domain residual signal 224 obtained by the correcting 212 the predicted transform-domain residual signal 208a, b using the signaled transform-domain residual signal 210 to a reverse transformation 226 (e.g., T'1) to obtain a non-transform-domain residual signal 228, and correct 230 the prediction signal 214 using the non-transform-domain residual signal 228. The prediction residual 200 may be provided in a non-transform domain (e.g., time-domain) in form of non-trans- form-domain residual signal 228 or in a transform domain in form of transform-domain residual signal 224. For example, the signaled transform-domain residual signal 210 and the predicted transform-domain residual signal 208a; 208b may be added coefficient-wise, resulting in a transform-domain residual signal 224 that is consequently also in the transformdomain. The prediction signal 214 may be provided in the non-transform domain, wherein the transform-domain residual signal 224 is first re-transformed into the non-transform domain so as to be combined with the prediction signal 214, e.g., by sample-wise addition. However, the prediction signal 214 may also be provided in the transform-domain, in which

[0103] FH241108PEP-2025376085fe case, the transform-domain residual signal 224 may not be re-transformed and directly combined with the prediction signal 214 (e.g. coefficient-wise addition), wherein the combined signal may then be re-transformed into the non-transform domain.

[0104] It is noted that the correction (e.g., correction 230) may be in a non-transform domain such as a time-domain. Here, thus, the non-transform-domain residual signal 228 is the “prediction residual derived for the respective channel”.

[0105] The apparatus 12 may be configured to decode, for each channel 21 of the plurality of channels 21 a-f, a transform-domain syntax element 43 from the data stream 16 which indicates a selected transform domain out of a set of transform domains, subjecting a corrected transform-domain residual signal 224 obtained by the correcting the predicted transformdomain residual signal 208a; 208b using the signaled transform-domain residual signal 210 to a reverse transformation 226 associated with the selected transform-domain for the respective channel 21 a-f to obtain a non-transform-domain residual signal 228 and correct 230 the prediction signal 214 using the non-transform-domain residual signal 228.

[0106] It is noted that the set of transform domains being available might comprise DST (discrete sine transform) and DCT (discrete cosine transform) (and optionally bypass or identity transform). In other words, the set of transform domains may comprise (or consist of) one or more of DST, DCT, bypass transform and identify transform. For example, the set of transform domains may comprise DCT and not DST or may comprise DST and not DCT. Furthermore, the set of transform domains may comprise one of DCT and DST and may further comprise an identify transform. The transform-domain syntax element 43 may indicate which one of these transform domains is to be used. For example, the set of transform domains may comprise only DST and DCT and the transform-domain syntax element 43 may be a flag that indicates whether the transform domain is defined by DST or DCT. The apparatus 12 may subsequently use a reverse transform (or re-transform) based on the signaled one of DST and DCT that transforms the transform-domain residual signal 224 into the non-transform-domain residual signal 228. The selected transform domain may be signaled jointly (e.g., once) for more than one (e.g., all) of the plurality of channels 21a-f.

[0107] In the following example, the set of transform domains may comprise an identify transform (e.g., a transformation, which does not change values of the transform-domain residual signal 224, e.g., a reverse transformation for which samples have the same values as coefficients).

[0108] FH241108PEP-2025376085fe The apparatus 12 may be configured to decode, for each channel 21 of the plurality of channels 21 a-f, a transform-domain syntax element 43 from the data stream 16 which indicates a selected transform domain out of a set of transform domains, the set of transform domains including an identity transform, for each channel of the plurality of channels 21a-f whose selected transform-domain is not the identity transform, subject a corrected trans- form-domain residual signal 224 obtained by the correcting the predicted transform-domain residual signal 208a; 208b using the signaled transform-domain residual signal 210 to a reverse transformation 226 associated with the selected transform-domain for the respective channel 21 a-f to obtain a non-transform-domain residual signal 228 and correct 230 the prediction signal 214 using the non-transform-domain residual signal. It is noted that the set of transform domains being available may thusly comprise an identity transform. In other words, the set of transform domains may comprise an identify transform, wherein the apparatus 12 may be configured to skip performing a reverse transformation for those transformdomain residual signals 224, for which the identity transform is indicated, for example, and continue using the transform-domain residual signals 224 as a non-transform-domain residual signal 228.

[0109] The one or more dependent channels 202 may encompass all channels of the plurality of channels 201 a-d except one intra-channel-coded channel. The intra-channel-coded channel may be, for example, in channel order 32 and / or coding order, a first channel of the plurality of channels 201a-d. For example, channel 21a may be an intra-channel coded channel. The intra-channel-coded channel may be a channel with a channel index of 0. A block in the intra-channel-coded channel may be decodable independent from previously decoded blocks 140, e.g., decodable without inter-channel prediction. For example, dependent channels 202 may be are those for which AND with depChMask yields non-zero.

[0110] For each of the one or more dependent channels 201 , the one or more reference channels 202 may be determined by default (e.g. a channel immediately preceding in a channel decoding order 32 or intra-channel-coded channel), or by implicit or explicit (e.g. per dependent channel 202 or per channel group 240, and / or per block 140 or per sequence of blocks 140) signaling in the data stream 16. In other words, the apparatus 12 may be able to determine the reference channels 202 without or with additional information signaled in the data stream 16.

[0111] FH241108PEP-2025376085fe An explicit signaling may comprise a signaling information specifically for its use, e.g., a specific syntax element intended to provide the information for determining the reference signal 202. An implicit signaling may comprise signaling one or more syntax elements with a main information function, wherein said one or more syntax element may have additional information function for a different use.

[0112] For example, the one or more reference channels 202 may be a pre-determined number (e.g., one, two, three, or more) and / or all channels 21 preceding the dependent channel 201. In one example, all channels preceding a dependent channel 201 in channel order may be reference channels. For example, channel 21a may be a (e.g., the only) reference channel 202 for channel 21b, channels 21a, b, may be reference channels 202 for channel 21c, and channels 21a-c may be reference channels 202 for channel 21 d. The number of reference channels 202 may be limited, e.g., to one or two channels 21a-f. For example, the number of reference channels 202 may be limited to two so that, for example, channels 21 b, c (e.g., at not channel 21a) may be reference channels for channel 21d. The reference channels 202 are not necessarily limited to immediately preceding channels 21. For example, one or more channels may always form a reference channel 202, e.g., wherein channel 21a forms a reference channel for each of the channels 21b-d (e.g., due to being decoded first and / or being intra-coded). The reference channels 202 may form a combination of default channels and preceding channels. For example, for each dependent channel 201 , channel 21a (e.g., intra-coded) as well as an immediately preceding channel (e.g., in channel order 32, e.g., unless the preceding channel is already channel 21a) may form reference channels 202.

[0113] The reference channels 202 may be inferred from a channel group 240, for example, wherein, in case a channel group 240 has more than one channel, only channels 21 of the channel group 240 can form a reference channel 202. For example, reference channels 202 may be defined as all (or a subset thereof) channels of the channel group 240 that precede the dependent channel in channel order 32.

[0114] The plurality of channels 21a-f may be one of a plurality of channel groups 240 of channels 21 of the multi-channel waveform signal 14, and the apparatus 12 may be configured to decode the multi-channel waveform signal 14 from the data stream 16 channel group 240 wise with decoding the commonality syntax element 13 for each channel group 240.

[0115] FH241108PEP-2025376085fe It is noted that commonality signaling may be made per channel group 240. Fig. 3 might show a channel group at 240, comprising channels 21 a-f, and optionally more channels). One advantage may be that channel grouping may, thus, additionally render coding more effective by accordingly grouping channels. For example, grouping may be performed based on similarities, e.g., in regards to sampling rate and / or data type. A signaling of commonality may use already established channel structures and therefore do not have to define the channel groups themselves, allowing for improved coding efficiency.

[0116] Each channel 21 of the plurality of channels 21 a-f may be partitioned into a sequence of blocks 140c (e.g., a block 140 of a channel or channel index c) so that the blocks 140c of the channels c are mutually (e.g., temporally) aligned to each other, and the apparatus 12 may be configured to perform the decoding the commonality syntax element 13, the, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, decoding the set 31 of one or more prediction mode syntax elements or appointing or using and decoding each of the plurality of channels 21a-f using the one prediction mode 25, and the, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, decoding the set 31 of one or more prediction mode syntax elements for each of the plurality of channels 21 a-f, and decoding each of the plurality of channels 21 a-f using the prediction mode 39 decoded for the respective channel block-wise for a set 250 of mutually aligned blocks 140 of the plurality of channels 21 a-f comprising one block 140 of each channel 21 of the plurality of channels 21 a-f which is aligned to the one block 140 of each other channel 21 of the plurality of channels 21a-f. In other words, the decoding (e.g., as depicted in fig. 1 and 2) may be performed block-wise for a set 250 of mutually aligned blocks 140 of the plurality of channels 21 a-f.

[0117] It is noted that commonality signaling may be done, e.g., along a waveform sequence, in blocks, which blocks may be the temporal blocks 30 in which prediction takes place or frames. The mutual alignment may comprise that first samples of blocks 140 of the plurality of channels 21 a-f are assigned a same time instances (e.g., within a tolerance range, e.g., of 50% or 25% of a sample duration) and last samples of the blocks 140 of the plurality of channels 21a-f are assigned a same time instance. The alignment is exemplarily depicted in fig. 3 as a vertical alignment of left edges of the blocks 140 in the set 250 of mutually aligned blocks. The plurality of channels 21a-f may further have a common number of samples. The mutual alignment may extend across all channels 21 of a channel group 240 or of multiple channel groups 240.

[0118] FH241108PEP-2025376085fe In the example shown in fig. 3, the set of 250 of mutually aligned blocks 140 has exactly one block 140 per channel 21. However, the set 250 of mutually aligned blocks 140 may have larger number (e.g., two, three, four, or more) of blocks 140 for each channel 21. The set 250 of mutually aligned blocks 140 may comprise (e.g., consist of) the blocks 140 of a temporal block 30 or a frame (e.g., having plurality of temporal blocks 30).

[0119] The apparatus 12 may be configured to, for each of one or more parametrized prediction modes of the set 29 of prediction modes, perform a decoding of a current channel 21 (e.g., channel 21d) of the plurality of channels 21a-f using the respective parametrized prediction mode by deriving one or more prediction parameters (e.g. block_pred_parameters()) for the current channel 21 and decoding the current channel 21 using the respective parametrized prediction mode parametrized according to the one or more prediction parameters.

[0120] It is noted that all prediction modes in the set 29 of prediction modes may be parametrized prediction modes, or merely a proper subset thereof. A parametrized prediction mode may be a prediction mode that may require, apart from an identification of the prediction mode itself, additional parameters for performing the parametrized prediction mode. For example, a no-prediction mode (or bypass mode), which may define skipping or not performing of a prediction may not be a parametrized prediction mode, as the skipping may not require additional parameters (e.g., the apparatus 12 may simply skip prediction upon identifying that the prediction mode to be performed is the no-prediction mode). In a different example, an intra-channel DC prediction mode may define a constant value for all samples of a block 140, in which case the constant value may parametrizable, thusly requiring signaling one or more prediction parameters that all determining the constant value. Such an intra-channel DC prediction mode may be considered a parametrized (or parametrizable) prediction mode. Prediction parameters may be signaled channel-wise (e.g., for channels 21 that require prediction parameters) or for more than one channel collectively, e.g., for the plurality of channels 21 a-f, for a channel group 240, for a set 250 of mutually aligned blocks 140, for a temporal block 30, or a frame.

[0121] The apparatus 12 may be configured to, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, if the one prediction mode 25 is one of the one or more parametrized prediction modes, decode one or more prediction parameters from the data stream 16, and decode each of the plurality of channels 21 a-f using the one prediction mode parametrized according to the one or

[0122] FH241108PEP-2025376085fe more prediction parameters, and if the commonality syntax element 13 does not indicate that one prediction mode is commonly attributed to the plurality of channels, decode, from the data stream 16, for each of the plurality of channels 21a-f for which the selected prediction mode 39 is one of the one or more parametrized prediction modes, one or more prediction parameters from the data stream 16, and decode the respective channel parametrized according to the one or more prediction parameters decoded for the respective channel. In other words, in case of communality of a parametrized prediction mode, the apparatus 12 may be configured to decode one or more prediction parameters for decoding the plurality of channels 21a-f. The one or more prediction parameters may thusly be decoded once jointly for the plurality of channels 21 a-f.

[0123] It is noted, for example, that the codec (e.g., apparatus 12) uses confirmative commonality signaling concurrently also as a commonality indication of prediction mode parameter, as exemplary shown left in Fig. 20 (e.g., as will be discussed further below). One advantage is that by restricting the transmission of channel wise prediction mode parameters to cases where commonality does not apply, transmission overhead may be improved.

[0124] The apparatus 12 may be configured to, irrespective of whether the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, decode, from the data stream 16, for each of the plurality of channels 21a- f decoded using a prediction mode being one of the one or more parametrized prediction modes, one or more prediction parameters from the data stream 16, and decode the respective channel 21 parametrized according to the one or more prediction parameters decoded for the respective channel 21 .

[0125] It is noted that the codec (e.g., apparatus 12) does not use confirmative commonality signaling concurrently as a commonality indication of prediction mode parameter, for example, as shown right in Fig. 20. An advantage is that by not restricting the transmission of channel wise prediction mode parameters to cases where commonality does not apply, the case of mode communality is made more likely to occur.

[0126] The apparatus 12 may be configured to, if the commonality syntax element 13 indicates that one prediction mode is commonly attributed to the plurality of channels 21 a-f, for each of the plurality of channels 21 a-f, decode one or more prediction parameters from the data stream 16, and decode the respective channels 21 using the one prediction mode 25 parametrized according to the one or more prediction parameters, and if the commonality syntax

[0127] FH241108PEP-2025376085fe element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, decode, from the data stream 16, for each of the plurality of channels 21 a-f for which the selected prediction mode is one of one or more parametrized prediction modes, one or more prediction parameters from the data stream 16, and decode the respective channel 21 parametrized according to the one or more prediction parameters decoded for the respective channel 21. In other words, the apparatus 12 may not automatically use common prediction parameters for all channels 21 the plurality of channels 21a- f, but decodes prediction parameters for individual channels 21 , thusly providing flexibility in the prediction parameter, which may promote a common prediction mode.

[0128] It is noted that the codec (e.g., apparatus 12), for example, does not use confirmative commonality signaling concurrently also as a commonality indication of prediction mode parameter. An advantage may be that by not restricting the transmission of channel wise prediction mode parameters to cases where commonality does not apply, the case of mode com- munality is made more likely to occur.

[0129] The apparatus 12 may be configured to, in decoding each of the plurality of channels 21 a-f using the one prediction mode 25 or the decoding each of the plurality of channels 21 a-f using the selected prediction mode for the respective channel, use transform-based prediction residual decoding in, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, one transform domain out of a set of transform domains which is commonly selected among the plurality of channels 21 a-f, and, if the commonality syntax element does 13 not indicate that one prediction mode is commonly attributed to the plurality of channels 21 a-f, for each of the plurality of channels 21 a-f, a selected transform domain which is channel-individually selected out of the set of transform domains. In other words, in case of communality, the apparatus 12 may be configured to use transform-based prediction residual decoding in one (e.g., single) transform domain that is commonly selected for among the plurality of channels 21 a-f. The selection may be signaled, e.g., wherein an indicator representative of the transform domain is signaled before or with the first block 140 of a first channel 21a. In a different example, the selected transform domain may be selected by default, e.g., due to a communality (e.g., wherein the apparatus 12 selects a transform domain of DCT (or any other transform) in case of communality).

[0130] FH241108PEP-2025376085fe It is noted, for example, that the codec (e.g., apparatus 12) uses confirmative commonality signaling concurrently also as a transform domain commonality singling. An advantage may be that this may further increase coding efficiency.

[0131] The apparatus 12 may be configured to decode from the data stream 16 a further commonality syntax element 45 indicating for the plurality of channels 21a-f of the multi-channel waveform signal 14, whether, among a set of transform domains supported by the apparatus 12, one transform domain is commonly attributed to the plurality of channels 21 a-f, in decoding each of the plurality of channels 21 a-f using the one prediction mode 25 or the decoding each of the plurality of channels using the selected prediction mode for the respective channel 21 , use transform-based prediction residual decoding in, if the further commonality syntax element 45 indicates that one transform domain is commonly attributed to the plurality of channels 21 a-f, the one transform domain, and, if the further commonality syntax element 45 does not indicate that one transform domain is commonly attributed to the plurality of channels 21 a-f, for each of the plurality of channels 21 a-f, a selected transform domain which is channel-individually selected out of the set of transform domains.

[0132] In other words, the further commonality syntax element 45 may indicate whether the plurality of channels 21 a-f are to be transform-based prediction residual decoded in one (e.g., single) transform domain jointly used for all channels 21 of the plurality of channels 21a-f or in channel-individually selected transform domains. A signaling of a transform domain may therefore be bundled into a signaling for all of the plurality of channels 21 a-f, which may improve coding efficiency. It is noted that, for example, the codec (e.g., apparatus 12) uses further (parallel) commonality signaling as a transform domain commonality singling. An advantage may be that this may further increase coding efficiency.

[0133] The above example of a further commonality syntax element 45 may essentially form a switch for whether or not to use transform-based prediction residual decoding in a transform domain that is commonly attributed to the plurality of channels 21 a-f. The use of the further commonality syntax element 45 may be independent of the commonality syntax element 13. However, in a different example, a parsing or checking of a further commonality syntax element 45 may depend on the commonality syntax element 13.

[0134] The apparatus 12 may be configured to, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, decode from the data stream 16 a further commonality syntax element 45 indicating for the

[0135] FH241108PEP-2025376085fe plurality of channels 21a-f of the multi-channel waveform signal 14, whether, among a set of transform domains supported by the apparatus 12, one transform domain is commonly attributed to the plurality of channels 21 a-f, in decoding each of the plurality of channels 21a-f using the one prediction mode, use transform-based prediction residual decoding in, if the further commonality syntax element 45 indicates that one transform domain is commonly attributed to the plurality of channels 21 a-f, the one transform domain, and, if the further commonality syntax element 45 does not indicate that one transform domain is commonly attributed to the plurality of channels 21 a-f, for each of the plurality of channels 21a- f, a selected transform domain which is channel-individually selected out of the set of transform domains, and, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, in decoding each of the plurality of channels 21a-f using the decoding each of the plurality of channels 21a-f using the selected prediction mode for the respective channel, use transform-based prediction residual decoding in, for each of the plurality of channels 21 a-f, a selected transform domain which is channel-individually selected out of the set of transform domains. In other words, the apparatus 12 may be configured to decode (e.g., parse, expect) a further commonality syntax element 45 only if the commonality syntax element 13 indicates commu- nality, but may not decode (e.g., skip or not parse or not expect) a further commonality syntax element 45 and instead proceed with decoding each of the plurality of channels 21a- f in channel-individually selected domains, if the commonality syntax element 13 does not indicate communality. As a result, signaling of the further commonality syntax element 45 may be omitted in certain cases (e.g., when the commonality syntax element 13 does not indicate communality), which may improve coding efficiency.

[0136] It is noted, for example, that the codec uses further (subsidiary) commonality signaling as a transform domain commonality singling. One advantage may be that this may further increase coding efficiency as further commonality transmission overhead is more likely to occur if prediction mode commonality signaling is active; wherein further commonality syntax element needs only be transmitted then.

[0137] Above, different examples have been described that are related to one transform domain out of a set of transform domain which is commonly selected among the plurality of channels 21 a-f. For example, the one transform domain may be selected if the commonality syntax element 13 indicates communality of one prediction mode, or if a further commonality syntax element 45 indicates communality of one transform domain. Such one transform domain

[0138] FH241108PEP-2025376085fe may be selected by default, by implicit signaling, or by explicit signaling as described in the following.

[0139] The apparatus 12 may be configured to, if it is indicated (e.g., by the commonality syntax element 13) that one prediction mode is commonly attributed to the plurality of channels 21 a-f, select the one transform domain out of the set of transform domain by default or by implicitly or explicit signaling, and, if it is not indicated that one prediction mode is commonly attributed to the plurality of channels, select, for each of the plurality of channels 21 a-f, the selected transform domain by default or by implicitly or explicit signaling contained in the data stream 16 for the respective channel 21 .

[0140] For example, a default one transformation domain may be selected based on a state (e.g., zero or one of a flag) of the commonality syntax element 13 and / or the further commonality syntax element 45 (if present). For example, if communality of prediction mode is indicated, the apparatus 12 may be configured to select a default one transformation domain that pertains to DCT (or DST). Similarly, a state of the further commonality syntax element 45 may additionally or alternatively affect the default one transformation domain.

[0141] The set 29 of prediction modes may comprise one or more of one or more intra-channel prediction modes, and one or more inter-channel prediction modes. For example, the set 29 of prediction modes may comprise (e.g., respectively one or more prediction modes of) only intra-channel prediction modes, only inter-channel prediction modes or both, intra- and inter-channel prediction modes.

[0142] For example, the set 29 of prediction modes may comprises one or more of an intra-channel DC prediction mode, an intra-channel line-fitting prediction mode, an intra-channel block matching prediction mode, a no-prediction mode, and one or more inter-channel prediction modes. The intra-channel DC prediction mode may comprise setting values to be predicted (e.g., samples or coefficients to be predicted) to a single value (e.g., wherein the single value may be pre-defined or parametrizable using on signaled prediction parameters). The intra-channel line-fitting prediction mode may comprise setting values to be predicted (e.g., samples or coefficients to be predicted) according to a linear function (e.g., with a sample position or coefficient position as parameter), wherein, as an option the linear function may be pre-determined or parametrizable using on signaled prediction parameters. The intra- channel block matching prediction may comprise copying values (e.g., samples or coefficients) of already decoded bock 140 of the same channel and using the copied values (e.g.,

[0143] FH241108PEP-2025376085fe or a re-scaled version thereof) as a prediction signal. The intra-channel block matching prediction may be parametrizable in regards to prediction parameters (e.g., offset, e.g., sample offset or coefficient offset) that allow identifying a decoded block 140 to be copied. The noprediction mode may comprise using only zero values (e.g., for samples of coefficients), wherein, for example, a block 140 to be decoded is reconstructed only based on a signaled residual signal. An inter-channel prediction mode may comprise copying values (e.g., samples or coefficients) of already decoded values (e.g., already decoded block 140) of a channel other than a currently to be coded channel (e.g., other than a currently to be coded block 140).

[0144] The apparatus 12 may be configured to decode the set 31 of one or more prediction mode syntax elements for a first channel (e.g., channel 21a) among the plurality of channels 21a- f prior to the commonality syntax element 13 and, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, the set 31 of one or more prediction mode syntax elements decoded for a first channel (e.g., channel 21a) may indicate the one prediction mode 25, and if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, sequentially decode the set 31 of one or more prediction mode syntax elements for subsequent channels (e.g., channels 21 b-f) among the plurality of channels 21 a-f. E.g., as in the syntax example, the commonality syntax element 13 may follow the mode syntax (e.g., set 31 of one or more prediction mode syntax elements) for the first channel of the channel group 240).

[0145] The apparatus 12 may be configured to decode the commonality syntax element 13 under a condition that the set 29 of one or more prediction mode syntax elements decoded for the first channel (e.g., channel 21a) indicate a selected prediction mode falling into a predetermined subset of one or more prediction modes. In other words, the commonality syntax element 13 may only be signaled (e.g., and parsed) if a prediction mode indicated by the set 29 of one or more prediction mode syntax elements of the first channel triggers such a signaling, e.g., because only certain prediction modes of the predetermined subset may have a sufficient probability of being viable for being commonly attributed to the plurality of channels 21 a-f. For example, an intra-channel DC prediction mode and / or no-prediction mode may not be part of the subset (e.g., due to generating low similarity predictions), such that if the set 29 of one or more prediction mode syntax elements of the first channel indicates the intra-channel DC prediction mode and / or no-prediction mode, the apparatus 12

[0146] FH241108PEP-2025376085fe may not parse or expect a commonality syntax element 13. However, any other predetermined subset or complement to the predetermined subset may be defined.

[0147] E.g., other than in the syntax example, the commonality syntax element 13, for example, may only follow the mode syntax (e.g., set 31 of one or more prediction mode syntax elements) for the first channel of the channel group 240 if this mode syntax indicates a certain mode which turns out to make the commonality signaling worthwhile thereby rendering the signaling more efficient.

[0148] Fig. 4 shows a schematic view of an apparatus 12 (e.g., encoder) for encoding a multichannel waveform signal 14 into a data stream 16 using block-based prediction.

[0149] The apparatus 10 is configured to encode into the data stream 16 a commonality syntax element 13 (e.g. common_pred_mode) indicating for a plurality of channels 21a-f (e.g., channels 21 of one channel group 240a) of the multi-channel waveform signal 14, whether, among a set 29 of prediction modes supported by the apparatus 10, one prediction mode 25 is commonly attributed to the plurality of channels 21a-f (e.g. relating to one temporal block 30, i.e. one set 250 of mutually aligned blocks 140, e.g. of one channel group 240), if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21a-f.

[0150] The apparatus 10 is configured to encode a set 31 of one or more prediction mode syntax elements (e.g. block_pred_mode) into the data stream 16 which indicate a selected prediction mode 33 out of the set 29 of prediction modes, wherein the selected prediction mode 33 is the one prediction mode 25, or a set 31 of one or more prediction mode syntax elements encoded for a first channel 21a among the plurality of channels 21a-f is to be appointed the one prediction mode 25, or a default prediction mode 35 among the set 29 of prediction modes is to be used as the one prediction mode 25, and encode each of the plurality of channels 21a-f using the one prediction mode 25.

[0151] The apparatus 10 is configured to, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, encode, into the data stream 16, for each of the plurality of channels 21 a-f, the set 31 of one or more prediction mode syntax elements, which indicate a selected prediction mode 39 (e.g., comprising prediction modes 39a, b, c, etc.) out of the set 29 of prediction modes for

[0152] FH241108PEP-2025376085fe the respective channel 21 a-f, and encode each of the plurality of channels 21a-f using the selected prediction mode 39 for the respective channel 21 a-f.

[0153] The apparatus 10 may therefore realize an aspect of a common prediction mode. It is noted that, for example, the commonality syntax element 13 may be transmitted prior to a first set 31 of one or more prediction mode syntax elements or subsequently thereto. It could also be sent in-between, e.g., in case of more than one prediction mode syntax element. A state of the commonality syntax element 13 indicating commonality might even be indicative of the common prediction mode. Ine advantage may be that the apparatus 10 (e.g., encoder) may efficiently signal a common prediction mode 25 for the plurality of channels 21 a-f; an additional overhead may be more than compensated by necessitating the signaling of the set 31 of one or more prediction mode syntax elements merely once in cases of commonality).

[0154] The apparatus 10 may be, may comprise, or may be part of an encoder. The apparatus 10 may comprise a processor (e.g., microprocessor) configured to perform the functions (e.g., steps) of the apparatus 10. The decoder 10 may be part of or may comprise a computer, smartphone, tablet, smart-watch, medical device, displaying device, server, or any other form of cloud computing resource. The encoder 10 may be part of or comprise a medical device (e.g., electroencephalograph and / or electrocardiograph), a seismic device (e.g., seismograph or seismometer), or an audio processing device. The apparatus 10 may be configured to encode a data stream 14 decodable by any apparatus 12 disclosed herein. Vice versa, any apparatus 12 disclosed herein may be configured to decode any data stream 14 disclosed herein, e.g., encoded by any apparatus 10 disclosed herein. Any feature disclosed herein with reference to apparatus 12 may be applicable in any feature combination to the apparatus 10 and vice versa.

[0155] The apparatus 10 may be configured to determine whether to use a common prediction mode independent of a rate-distortion optimization. For example, the apparatus 10 may select the prediction mode for each channel independent from a selection of a prediction mode of the other channels of the plurality of channels 21 a-f, and if (e.g., by coincidence) all the channels of the plurality of channels 21a-f have the same prediction mode, encode the commonality syntax element 13 into the data stream 16. In a different example, the apparatus 10 may be configured to determine based on rate-distortion optimization whether to use a common prediction mode for the plurality of channels 21 a-f. For example, the ap-

[0156] FH241108PEP-2025376085fe paratus 10 may compare a rate and distortion for the plurality of channels 21a-f being encoded with independent (e.g., different) prediction modes with a rate and distortion of the plurality of channels 21a-f using a common prediction mode (e.g., wherein one or more common prediction modes may be tested). Dependent on the rate distortion, the apparatus 10 may then chose to encode with or without a common prediction mode.

[0157] Fig. 5 shows a schematic view of another example of the apparatus 10. The apparatus 10 may comprise any feature of function disclosed for any other apparatus 1 (or apparatus 12). The apparatus 10 may be configured to encode the data stream 16 shown in fig. 3. Therefore, the following description also makes reference to fig. 3.

[0158] The apparatus 10 may be configured to encode, for each channel 21 of the plurality of channels 21 a-f, a prediction residual 200 by, for each of one or more dependent channels 201 in the set of the plurality of channels 21 a-f, using inter-channel transform-domain residual prediction 204a; 204b from the prediction residual 206a; 206b of one or more reference channels 202 within the plurality of channels to obtain a predicted transform-domain residual signal 208a; 208b, and encoding a signaled transform-domain residual signal 210 into the data stream 16 using which the predicted transform-domain residual signal 208a; 208b is correctable, and so that, for each channel of the plurality of channels 21 a-f, a prediction signal 214 obtained by the prediction mode using which the respective dependent channel 201 is encoded is correctable using the prediction residual 200 encoded for the respective channel.

[0159] It is noted that, for example, the codec (e.g., functions of the apparatus 10) combines commonality signaling with inter-channel transform-domain residual prediction, e.g., wherein the inter-channel transform-domain residual prediction might use a spectral filtering using a filter kernel 216 which extends from the respective dependent channel 201 into one or more reference channels 202 so as to cover already reconstructed transform coefficients 218 of these channels (i.e. 201 and 202) and the correction 212 may coefficient wise alternatingly be performed with the inter-channel residual prediction while moving the filter kernel 216 spectrally as illustrated by 220, thereby reconstructing the transform coefficients of channel 201 along direction 220 sequentially, or the inter-channel transform-domain residual prediction might simply copy 222 transform coefficients 218 of one or more reference channels. The prediction residual of any in terms of inter-channel transform-domain residual prediction independently coded channels may be encoded by using the signaled spectrum 210 directly. An advantage may be that by rending the transmission of a common prediction mode

[0160] FH241108PEP-2025376085fe among the channels 21a-f more efficient in terms of less singling overhead, it becomes more likely to occur with the advantage that the inter-channel transform-domain residual prediction will, at higher likelihood, be efficient as the reference channel 202 is more likely coded in same prediction mode.

[0161] The apparatus 10 may be configured to encode, for each channel 21 of the plurality of channels 21 a-f, a prediction residual 200 (e.g., see fig. 3) by, for each of one or more dependent channels 201 in the set of the plurality of channels 21a-f (e.g. for any non-depend- ent channel, a signaled transform-domain residual signal is encoded into the data stream 16 into which the prediction residual 200 is coded without inter-channel transform-domain residual prediction), encoding an inter-channel transform-domain residual prediction syntax element 41 into the data stream 16, if the inter-channel transform-domain residual prediction syntax element 41 is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual 206a, 206b of one or more reference channels 202 within the plurality of channels 21a- f to obtain a predicted transform-domain residual signal 208a, 208b, and encoding a signaled transform-domain residual signal 210 into the data stream 16 using which the predicted transform-domain residual signal 208a, 208b is correctable, and, if the inter-channel transform-domain residual prediction syntax element 41 is not indicative of the use of interchannel transform-domain residual prediction, encoding a signaled transform-domain residual signal 210 into the data stream 16 into which the prediction residual 200 is coded without inter-channel transform-domain residual prediction, and, so that, for each channel of the plurality of channels 21 a-f, a prediction signal 214 obtained by the prediction mode using which the respective channel 21 is encoded is correctable using the prediction residual 200 (e.g., signaled transform-domain residual signal 210 or a reverse transformed version thereof) encoded for the respective channel 21.

[0162] It is noted, for example, the codec combines commonality signaling with inter-channel trans- form-domain residual prediction channel-individually activatable. It is noted that, here, the dependent channels 201 are the channels 21 possibly coded using inter-channel transformdomain residual prediction. Whether inter-channel transform-domain residual prediction is indeed used may depend on some inter-channel transform-domain residual prediction syntax element. An advantage may be that by rending the transmission of a common prediction mode 25 among the channels 21 more efficient in terms of less singling overhead, it be-

[0163] FH241108PEP-2025376085fe comes more likely to occur with the advantage that the inter-channel transform-domain residual prediction will, at higher likelihood, be efficient as the reference channel 202 is more likely coded in same prediction mode.

[0164] The apparatus 10 may be configured to encode, for each channel 21 of the plurality of channels 21 a-f, a prediction residual 200 by, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21a-f, for each of one or more dependent channels 201 in the set of the plurality of channels 21 a-f (e.g. for any non-dependent channel, a signaled transform-domain residual signal 210 is encoded into the data stream 16 into which the prediction residual 200 is coded without inter-channel transform-domain residual prediction), encoding an inter-channel transformdomain residual prediction syntax element 41 into the data stream, if the inter-channel trans- form-domain residual prediction syntax element 41 is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual 206a, 206b of one or more reference channels 202 within the plurality of channels 21a-f to obtain a predicted transform-domain residual signal 208a, 208b, and encoding a signaled transform-domain residual signal 210 into the data stream using which the predicted transform-domain residual signal 208a, 208b is correctable, and, if the inter-channel transform-domain residual prediction syntax element 41 is not indicative of the use of inter-channel transform-domain residual prediction, encoding a signaled transform-domain residual signal 210 into the data stream 16 into which the prediction residual 200 is coded without inter-channel transform-domain residual prediction, and if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, for each channel of the plurality of channels 21 a-f, encoding a signaled transform-domain residual signal 210 into the data stream 16 into which the prediction residual 200 is coded without inter-channel transform-domain residual prediction, and so that, for each channel of the plurality of channels 21 a-f, a prediction signal 214 obtained by the prediction mode 39 using which the respective channel 21 is encoded is correctable using the prediction residual 200 encoded for the respective channel 21.

[0165] It is noted, for example, the codec uses negative commonality signaling concurrently as means to guide dependent-channel-wise transform-domain residual prediction switch: infer that transform-domain residual prediction is off for all channels in case of non-commonality. An advantage may be that by restricting the transmission of inter-channel transform-domain residual prediction syntax elements to a case where commonality applies, transmission

[0166] FH241108PEP-2025376085fe overhead is increased, with nevertheless enabling channel wise activation of inter-channel transform-domain residual prediction in case of commonality.

[0167] The apparatus 10 may be configured to encode, for each channel of the plurality of channels 21 a-f, a prediction residual 200 by, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, for each of one or more dependent channels 201 in the set of the plurality of channels 21 a-f (e.g. for any non-dependent channel, a signaled transform-domain residual signal 210 is encoded into the data stream 16 into which the prediction residual 200 is coded without inter-channel transform-domain residual prediction), using inter-channel transform-domain residual prediction from the prediction residual 206a, 206b of one or more reference channels 202 within the plurality of channels 21 a-f to obtain a predicted transform-domain residual signal 208a, 208b, and encoding a signaled transform-domain residual signal 210 into the data stream 16 using which the predicted transform-domain residual signal 208a, 208b is correctable, and, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, for each of the one or more dependent channels 201 in the set of the plurality of channels 21 a-f (e.g. for any non-dependent channel, a signaled transform-domain residual signal 210 is encoded into the data stream 16 into which the prediction residual 200 is coded without inter-channel transform-domain residual prediction), encoding an inter-channel transform-domain residual prediction syntax element 41 into the data stream 16, if the inter-channel transform-domain residual prediction syntax element 41 is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual 206a, 206b of one or more reference channels 202 within the plurality of channels 21a- f to obtain a predicted transform-domain residual signal 208a, 208b, and encoding a signaled transform-domain residual signal 210 into the data stream 16 using which the predicted transform-domain residual signal 208a, 208b is correctable, and, if the inter-channel transform-domain residual prediction syntax element 41 is not indicative of the use of interchannel transform-domain residual prediction, encoding a signaled transform-domain residual signal 210 into the data stream 16 into which the prediction residual 200 is coded without inter-channel transform-domain residual prediction, and so that, for each channel of the plurality of channels 21 a-f, a prediction signal 214 obtained by the prediction mode 39 using which the respective channel 21 is encoded is correctable using the prediction residual 200 encoded for the respective channel 21.

[0168] FH241108PEP-2025376085fe It is noted that, for example, the codec uses confirmative commonality signaling concurrently as means to infer that dependent transform-domain residual prediction is on for all channels in case of commonality. An advantage may be that by restricting the transmission of inter-channel transform-domain residual prediction syntax elements to case where commonality does not apply, transmission overhead is tailored to cases where the activation of inter-channel transform-domain residual prediction is less likely to apply while exploiting that inter-channel transform-domain residual prediction is likely to be useful in case of commonality).

[0169] For correcting the prediction signal 214, a corrected transform-domain residual signal 224 obtained by the correcting 212 the predicted transform-domain residual signal 208a, b using the signaled transform-domain residual signal 210 may be subject to a reverse transformation 226 to obtain a non-transform-domain residual signal 228, and the prediction signal 214 may be corrected using the non-transform-domain residual signal 228.

[0170] It is noted, for example, a correction in non-transform domain such as time-domain may be used. Here, thus, the non-transform-domain residual signal may be the “prediction residual derived for the respective channel”.

[0171] The apparatus 10 may be configured to encode, for each channel 21 of the plurality of channels 21 a-f, a transform-domain syntax element 43 into the data stream 16 which indicates a selected transform domain out of a set of transform domains, so that for correcting the prediction signal 214, a corrected transform-domain residual signal 224 obtained by the correcting the predicted transform-domain residual signal 208a, 208b using the signaled transform-domain residual signal 210 may be subject to a reverse transformation 226 associated with the selected transform-domain for the respective channel 21 to obtain a non- transform-domain residual signal 228 and the prediction signal 214 may be corrected using the non-transform-domain residual signal 228.

[0172] It is noted that, for example, a set of transform domains being available might comprise DST and DCT (and optionally bypass or identity transform). For example, the set of transform domains may comprise DCT and not DST or may comprise DST and not DCT.

[0173] The apparatus 10 may be configured to encode, for each channel of the plurality of channels 21 a-f, a transform-domain syntax element 43 into the data stream 16 which indicates a selected transform domain out of a set of transform domains, the set of transform domains

[0174] FH241108PEP-2025376085fe including an identity transform, for each channel of the plurality of channels 21a-f whose selected transform-domain is not the identity transform, for correcting the prediction signal 214, a corrected transform-domain residual signal 224 obtained by the correcting the predicted transform-domain residual signal 208a, 208b using the signaled transform-domain residual signal 210 is to be subject to a reverse transformation 226 associated with the selected transform-domain for the respective channel to obtain a non-transform-domain residual signal 228 and the prediction signal 214 is to be corrected using the non- transformdomain residual signal 228.

[0175] It is noted, for example, that a set of transform domains being available may comprise identity transform.

[0176] The one or more dependent channels 201 may encompass all channels of the plurality of channels 21a-f except one intra-channel-coded channel. It is noted that, e.g., dependent channels 201 may be those for which AND with depChMask yields non-zero.

[0177] For each of the one or more dependent channels 201 , the one or more reference channels 202 may be determined by default (e.g. a channel immediately preceding in a channel encoding order or intra-channel-coded channel), or by implicit or explicit (e.g. per dependent channel or per channel group, and / pr per block or per sequence of blocks) signaling in the data stream 16.

[0178] The plurality of channels 21a-f may be one of a plurality of channel groups 240 of channels 21 of the multi-channel waveform signal 14, and the apparatus 10 may be configured to encode the multi-channel waveform signal 14 into the data stream 16 channel group wise with encoding the commonality syntax element 13 for each channel group 240.

[0179] It is noted, for example, that commonality signaling may be made per channel group; Fig. 3 might show a channel group at 240. An advantage may be that channel grouping may, thus, additionally render coding more effective by accordingly grouping channels.

[0180] Each channel of the plurality of channels 21 a-f may be partitioned into a sequence of blocks 140cso that the blocks 140cof the channels c may be mutually aligned to each other, and the apparatus 10 may be configured to perform the encoding the commonality syntax element 13, the, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, encoding the set 31 of one or more

[0181] FH241108PEP-2025376085fe prediction mode syntax elements or encoding or using and encoding each of the plurality of channels 21a-f using the one prediction mode 25, and the, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, encoding the set 31 of one or more prediction mode syntax elements for each of the plurality of channels 21 a-f, and encoding each of the plurality of channels 21a- f using the prediction mode encoded for the respective channel block-wise for a set 250 of mutually aligned blocks 140 of the plurality of channels 21a-f comprising one block 140 of each channel 21 of the plurality of channels 21 a-f which is aligned to the one block 140 of each other channel of the plurality of channels 21a-f.

[0182] It is noted, e.g., that commonality signaling may be done, along waveform sequence, in blocks which blocks may be the temporal blocks 30 in which prediction takes place or frames.

[0183] The apparatus 10 may be configured to, for each of one or more parametrized prediction modes of the set 29 of prediction modes, perform an encoding of a current channel (e.g., channel 21d) of the plurality of channels 21a-f using the respective parametrized prediction mode by deriving one or more prediction parameters (e.g. block_pred_parameters()) for the current channel 21 and encoding the current channel 21 using the respective parametrized prediction mode parametrized according to the one or more prediction parameters.

[0184] It is noted, e.g., that all prediction modes in the set of prediction modes may parametrized prediction modes, or merely a proper subset thereof.

[0185] The apparatus 10 may be configured to, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, if the one prediction mode 25 is one of the one or more parametrized prediction modes, encode one or more prediction parameters into the data stream 16, and encode each of the plurality of channels 21 a-f using the one prediction mode 25 parametrized according to the one or more prediction parameters, and, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, encode, into the data stream 16, for each of the plurality of channels 21 a-f for which the selected prediction mode is one of the one or more parametrized prediction modes, one or more prediction parameters from the data stream 16, and encode the respective channel 21 parametrized according to the one or more prediction parameters encoded for the respective channel 21.

[0186] FH241108PEP-2025376085fe It is noted, e.g., that the codec (e.g., apparatus 10) may use confirmative commonality signaling concurrently also as a commonality indication of prediction mode parameter as shown left in Fig. 20. An advantage may be that by restricting the transmission of channel wise prediction mode parameters to cases where commonality does not apply, a transmission overhead may be improved.

[0187] The apparatus 10 may be configured to, irrespective of whether the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, encode, into the data stream 16, for each of the plurality of channels 21a-f encoded using a prediction mode being one of the one or more parametrized prediction modes, one or more prediction parameters from the data stream 16, and encode the respective channel parametrized according to the one or more prediction parameters encoded for the respective channel.

[0188] It is noted, e.g., that the codec does not use confirmative commonality signaling concurrently as a commonality indication of prediction mode parameter as shown right in Fig. 20. An advantage may be that by not restricting the transmission of channel wise prediction mode parameters to cases where commonality does not apply, the case of mode commu- nality is made more likely to occur.

[0189] The apparatus 10 may be configured to, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21a-f, for each of the plurality of channels 21 a-f, encode one or more prediction parameters into the data stream 16, and encode the respective channels 21 using the one prediction mode 25 parametrized according to the one or more prediction parameters, and, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, encode, into the data stream 16, for each of the plurality of channels 21 a-f for which the selected prediction mode is one of one or more parametrized prediction modes, one or more prediction parameters from the data stream 16, and encode the respective channel parametrized according to the one or more prediction parameters encoded for the respective channel.

[0190] It is noted, e.g., that the codec does not use confirmative commonality signaling concurrently also as a commonality indication of prediction mode parameter. An advantage may be that by not restricting the transmission of channel wise prediction mode parameters to

[0191] FH241108PEP-2025376085fe cases where commonality does not apply, the case of mode communality is made more likely to occur.

[0192] The apparatus 10 may be configured to, in encoding each of the plurality of channels 21a-f using the one prediction mode 25 or the decoding each of the plurality of channels 21a-f using the selected prediction mode for the respective channel, use transform-based prediction residual encoding in, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, one transform domain out of a set of transform domains which is commonly selected among the plurality of channels 21 a-f, and, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, for each of the plurality of channels 21 a-f, a selected transform domain which is channel-individually selected out of the set of transform domains.

[0193] It is noted, for example, that the codec uses confirmative commonality signaling concurrently also as a transform domain commonality singling. An advantage may be that this may further increase coding efficiency.

[0194] The apparatus 10 may be configured to encode into the data stream 16 a further commonality syntax element 45 indicating for the plurality of channels 21 a-f of the multi-channel waveform signal, whether, among a set of transform domains supported by the apparatus, one transform domain is commonly attributed to the plurality of channels 21 a-f, in encoding each of the plurality of channels 21 a-f using the one prediction mode 25 or the encoding each of the plurality of channels 21 a-f using the selected prediction mode for the respective channel, use transform-based prediction residual encoding in, if the further commonality syntax element 45 indicates that one transform domain is commonly attributed to the plurality of channels 21 a-f, the one transform domain, and, if the further commonality syntax element 45 does not indicate that one transform domain is commonly attributed to the plurality of channels 21 a-f, for each of the plurality of channels 21a-f, a selected transform domain which is channel-individually selected out of the set of transform domains.

[0195] It is noted, for example, that the codec uses further (parallel) commonality signaling as a transform domain commonality singling. An advantage may be that this may further increase coding efficiency.

[0196] FH241108PEP-2025376085fe For example, the set of transform domains may comprise one or more of discrete cosine transform (DCT, e.g., DCT-II), discrete sine transform (DST), discrete Fourier transform (DFT), and modified discrete cosine transform (MDCT).

[0197] The apparatus 10 may be configured to, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, encode into the data stream 16 a further commonality syntax element 45 indicating for the plurality of channels 21 a-f of the multi-channel waveform signal, whether, among a set of transform domains supported by the apparatus 10, one transform domain is commonly attributed to the plurality of channels 21 a-f, in encoding each of the plurality of channels 21a- f using the one prediction mode 25, use transform-based prediction residual encoding in, if the further commonality syntax element 45 indicates that one transform domain is commonly attributed to the plurality of channels 21 a-f, the one transform domain, and, if the further commonality syntax element 45 does not indicate that one transform domain is commonly attributed to the plurality of channels 21 a-f, for each of the plurality of channels 21a- f, a selected transform domain which is channel-individually selected out of the set of transform domains, and, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, in encoding each of the plurality of channels 21a-f using the decoding each of the plurality of channels 21a-f using the selected prediction mode for the respective channel 21 , use transform-based prediction residual encoding in, for each of the plurality of channels 21 a-f, a selected transform domain which is channel-individually selected out of the set of transform domains.

[0198] It is noted, for example, that the codec uses further (subsidiary) commonality signaling as a transform domain commonality singling. An advantage may be that this may further increase coding efficiency as further commonality transmission overhead is more likely to occur if prediction mode commonality signaling is active. One or more further commonality syntax element 45 needs only be transmitted then.

[0199] The apparatus 10 may be configured to, if it is indicated that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, select the one transform domain out of the set of transform domain by default or by implicitly or explicit signaling, and , if it is not indicated that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, select, for each of the plurality of channels 21 a-f, the selected transform domain by default or by implicitly or explicit signaling contained in the data stream 16 for the respective channel.

[0200] FH241108PEP-2025376085fe The set 29 of prediction modes may comprise one or more of one or more intra-channel prediction modes, and one or more inter-channel prediction modes. The set of prediction modes may comprise one or more of an intra-channel DC prediction mode, an intra-channel line-fitting prediction mode, an intra-channel block matching prediction mode, a no-predic- tion mode, and one or more inter-channel prediction modes.

[0201] The apparatus 10 may be configured to encode the set 31 of one or more prediction mode syntax elements for a first channel (e.g., channel 21a) among the plurality of channels 21a- f prior to the commonality syntax element 13 and if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, the set 31 of one or more prediction mode syntax elements encoded for the first channel indicates the one prediction mode 25, and if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, sequentially encode the set 31 of one or more prediction mode syntax elements for subsequent channels among the plurality of channels 21 a-f.

[0202] It is noted, for example, that as in the syntax example, the commonality syntax element 13 may follow the mode syntax for the first channel of the channel group 240.

[0203] The apparatus 10 may be configured to encode the commonality syntax element 13 under a condition that the set 31 of one or more prediction mode syntax elements encoded for the first channel (e.g., channel 21a) indicate a selected prediction mode falling into a predetermined subset of one or more prediction modes.

[0204] It is noted, for example, that other than in the syntax example, the commonality syntax element 13 may only follow the mode syntax for the first channel of the channel group if this mode syntax indicates a certain mode which turns out to make the commonality signaling worthwhile thereby rendering the signaling more efficient.

[0205] In the following, the second aspect, which relates to a common transform mode, will be described.

[0206] Fig. 6 shows an apparatus 12 for decoding a multi-channel waveform signal 14 from a data stream 16 using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual decoding.

[0207] FH241108PEP-2025376085fe The apparatus 12 is configured to decode from the data stream 16 a further commonality syntax element 45 indicating for a plurality of channels 21a-f of the multi-channel waveform signal 14, whether, among a set 51 of transform domains supported by the apparatus 12, one transform domain 53 is commonly attributed to the plurality of channels 21a-f.

[0208] The apparatus 12 is configured to, if the further commonality syntax element 45 indicates that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, decode each of the plurality of channels 21 a-f using the one transform domain 53 for the transform-based prediction residual decoding.

[0209] The apparatus 12 is configure to, if the further commonality syntax element 45 does not indicate that one transform domain is commonly attributed to the plurality of channels 21a- f, decode each of the plurality of channels 21 a-f using a selected transform domain 55 (e.g., transform domains 53a, 53b, 53c, etc.), which is channel-individually selected out of the set 51 of transform domains, for the transform-based prediction residual decoding.

[0210] The apparatus 12 therefore realizes an aspect of a common transform mode. An advantage may be that an apparatus for encoding (e.g., encoder, e.g., apparatus 10) may efficiently achieve transform equality thereby yielding a more effective singling which likely efficiently takes advantage from inter-channel transform-domain residual prediction.

[0211] Fig. 7 shows another example of an apparatus 12 for decoding a multi-channel waveform signal 14. The apparatus 12 shown in fig. 7 may comprise any feature disclosed with reference to fig. 6.

[0212] The use of a further commonality syntax element 45 has already been described above with reference to fig. 2 and 3. Therefore, any disclosure described above may be applicable to said apparatus 12 (e.g., with reference to of fig. 6 and 7) and vice versa.

[0213] The apparatus 12 may be configured to, if it is indicated that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, select the one transform domain 53 out of the set of transform domain by default (e.g., default transform domain 57) or by implicitly or explicit signaling, and, if it is not indicated that one transform domain is commonly attributed to the plurality of channels 21 a-f, select, for each of the plurality of channels 21a-

[0214] FH241108PEP-2025376085fe f, the selected transform domain 53 by default or by implicitly or explicit signaling contained in the data stream 16 for the respective channel 21.

[0215] For example, the further commonality syntax element 45 may be a flag (e.g., having two states), which only indicates whether one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, but not signal explicitly which transform domain to use. However, the apparatus 12 may still be able to one identify the one transform domain 53 or the selected transform domain, for example, by using the default transform domain 57 (e.g., in case of or in case of no commonality of a transform domain). The transform domain to be used may be explicitly signaled, e.g., by the further commonality syntax element 45 itself or a separate dedicated syntax element. In a different example, the transform domain to be used may be implicitly signaled, e.g., based on a syntax element having a different function, e.g., based on commonality syntax element 13.

[0216] The plurality of channels 21 a-f may be one of a plurality of channel groups 240 of channels 21 of the multi-channel waveform signal 14, and the apparatus 12 may be configured to decode the multi-channel waveform signal 14 from the data stream 16 channel group wise with decoding the further commonality syntax element 45 for each channel group 240.

[0217] It is noted, for example, that the commonality signaling may be made per channel group 240. For example, the apparatus 12 may be configured to decode the further commonality syntax element 45 once per channel group 240, e.g., before or with a first channel thereof. An advantage may be that channel grouping may, thus, additionally render coding more effective by accordingly grouping channels.

[0218] Each channel 21 of the plurality of channels 21 a-f may be partitioned into a sequence of blocks 140 so that the blocks 140 of the channels are mutually aligned (e.g., as described in the first aspect) to each other, and the apparatus 12 may be configured to perform the decoding the further commonality syntax element 45, the, if the further commonality syntax element 45 indicates that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, decoding each of the plurality of channels 21a-f using the one transform domain 53, and the, if the further commonality syntax element 45 does not indicate that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, decoding each of the plurality of channels 21 a-f using a selected transform domain 55 block-wise for a set 250 of mutually aligned blocks of the plurality of channels 21 a-f comprising one block

[0219] FH241108PEP-2025376085fe 140 of each channel 21 of the plurality of channels 21a-f which is aligned to the one block

[0220] 140 of each other channel 21 of the plurality of channels 21a-f.

[0221] It is noted, for example, that commonality signaling may be done, along waveform sequence, in blocks which blocks may be the temporal blocks 30 in which prediction takes place or frames.

[0222] The set 51 of transform domains may comprises a DCT domain, a DST domain and an identity transform domain. For example, the set of transform domains may comprise DCT and not DST or may comprise DST and not DCT.

[0223] Fig. 8 shows a schematic view of an apparatus 10 for encoding a multi-channel waveform signal 14 into a data stream 16 using block-based prediction, inter-channel transform-do- main residual prediction and transform-based prediction residual encoding. The apparatus 10 (e.g., encoder) may be configured to encode a data stream 16 decodable by the apparatus 12 described with reference to fig. 6 and 7. The apparatus 10 may have any feature of any apparatus 10 disclosed herein.

[0224] The apparatus 10 is configured to encode into the data stream 16 a further commonality syntax element 45 indicating for a plurality of channels 21a-f of the multi-channel waveform signal 14, whether, among a set 51 of transform domains supported by the apparatus 10, one transform domain 53 is commonly attributed to the plurality of channels 21a-f.

[0225] The apparatus 10 is configured to, if the further commonality syntax element 45 indicates that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, encode each of the plurality of channels 21 a-f using the one transform domain 53 for the transform-based prediction residual encoding.

[0226] The apparatus 10 is configured to, if the further commonality syntax element 45 does not indicate that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, encode each of the plurality of channels 21 a-f using a selected transform domain 55, which is channel-individually selected out of the set 51 of transform domains, for the transform-based prediction residual encoding.

[0227] FH241108PEP-2025376085fe The apparatus 10 my thusly may realize an aspect in form of a common transform mode. An advantage may be that the apparatus 10 (e.g., encoder) may efficiently achieve transform equality thereby yielding a more effective singling which likely efficiently takes advantage from inter-channel transform-domain residual prediction.

[0228] Fig. 9 shows another example of an apparatus 10 for encoding a multi-channel waveform signal 14 into a data stream 16 using block-based prediction. The apparatus 10 shown in fig. 9 may comprise any feature disclosed with reference to fig. 8.

[0229] The apparatus 10 may be configured to, if it is indicated that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, select the one transform domain 53 out of the set 51 of transform domains by default (e.g., default transform domain 57) or by implicitly or explicit signaling, and, if it is not indicated that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, select, for each of the plurality of channels 21 a-f, the selected transform domain by default or by implicitly or explicit signaling contained in the data stream 16for the respective channel 21.

[0230] The plurality of channels 21 a-f may be one of a plurality of channel groups 240 of channels of the multi-channel waveform signal 14, and the apparatus 10 may be configured to encode the multi-channel waveform signal 14 into the data stream 16channel group wise with encoding the further commonality syntax element 45 for each channel group 240. It is noted that, for example, commonality signaling may be made per channel group 240. An advantage may be that channel grouping may, thus, additionally render coding more effective by accordingly grouping channels.

[0231] Each channel of the plurality of channels 21 a-f may be partitioned into a sequence of blocks 140 so that the blocks 140 of the channels 21 are mutually aligned to each other, and the apparatus 10 may be configured to perform the encoding the further commonality syntax element 45, the, if the further commonality syntax element indicates that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, encoding each of the plurality of channels 21 a-f using the one transform domain 53, and the, if the further commonality syntax element 45 does not indicate that one transform domain 53 is commonly attributed to the plurality of channels 21a-f, encoding each of the plurality of channels 21a- f using a selected transform domain 55 block-wise for a set 250 of mutually aligned blocks 140 of the plurality of channels 21 a-f comprising one block of each channel of the plurality of channels 21 a-f which is aligned to the one block 140 of each other channel of the plurality

[0232] FH241108PEP-2025376085fe of channels 21a-f. It is noted that commonality signaling may be done, along waveform sequence, in blocks which blocks may be the temporal blocks 30, in which prediction takes place, or frames.

[0233] The set 51 of transform domains may comprise a DCT domain, a DST domain and an identity transform domain.

[0234] In the following, the third aspect, which relates to a common transform mode, will be described.

[0235] Fig. 10 shows a schematic view of an apparatus 12 for decoding a waveform signal 14 from a data stream 16. The apparatus 12 (e.g., decoder) may comprise any feature of any apparatus 12 disclosed herein.

[0236] Fig. 11 shows a schematic view of a sample-to-sample prediction of a block 140current (e.g., 140c), e.g., performed by the apparatus 12 of fig. 10.

[0237] The apparatus 12 is configured to perform sample-to-sample prediction 260 for a block 140CUrrent of the waveform signal 14 (e.g. in Fig. 11 more than one channel is shown for illustration only, however a single channel may be provided as well), to obtain a preliminary time-domain block predictor 214 (e.g., as disclosed herein with reference to aspect one and two, e.g., see also fig. 3), spectrally filter 300 the preliminary time-domain predictor 214 to obtain a filtered time-domain block predictor 302.

[0238] The apparatus 12 is further configured to perform transform-domain-to-transform-domain prediction 204a, b for the block 140current of the waveform signal 14 to obtain a transformdomain predictor 208a, b (e.g., as disclosed herein with reference to aspect one and two, e.g., see also fig. 3), decode a residual spectrum 210 from the data stream 16, and correct 212 (e.g., subject to a summation) the transform-domain predictor 208a, b using the residual spectrum 210 to obtain a corrected residual spectrum 224.

[0239] The apparatus 12 is configured to subject the corrected residual spectrum 224 to a retransformation 226 to obtain a time-domain residual signal 228, and correct 230 (e.g., subject to a summation) the time-domain block predictor 302 using the time-domain residual signal 228 (e.g. to obtain a reconstructed signal 304 for the block).

[0240] FH241108PEP-2025376085fe The apparatus 12 is configured to perform the spectrally filtering 300 the preliminary timedomain predictor 214 using a transfer function (e.g. by FIR filtering, e.g., using a digital filter) being higher (e.g., having a higher gain) in a first spectral region than compared to a second spectral region (e.g., different from the first spectral region, e.g., non-overlapping spectral regions), and perform the transform-domain-to-transform-domain prediction 204a, b spectrally restricted (e.g., using a spectral mask) to the second spectral region (e.g. restricting 204a, i.e. only there apply the filtering using a kernel 216), or by obtaining a preliminary transform-domain predictor (e.g., by obtaining transform-domain predictor 208a, b as described herein) and spectrally filtering the preliminary transform-domain predictor using a transfer function being higher in the second spectral region than compared to the first spectral region to obtain the transform-domain predictor (e.g. in 204b, i.e. multiplying with a corresponding transfer function which might be a step function being zero in the first and 1 in the second spectral region); or by performing filter synthesis using an impulse response which is higher in the second spectral region than compared to the first spectral region (e.g. in 204a, i.e. using different filter coefficients for kernel 216 in that same are, in terms of sum of squares or sum of absolutes for instance, smaller in first than in second spectral region).

[0241] It is noted, for example, that the spectrally varying prediction gain might be achieved by spectral filtering the time-domain block predictor and restricting, for instance, the transform- domain-to-transform-domain prediction 204a, b to the second spectral region. The trans- form-domain-to-transform-domain prediction 204a, b may be an inter-channel transform- domain-to-transform-domain prediction (e.g., as described herein such as in aspects one and two). The sample-to-sample prediction 260 may use block-wise selection among a set of prediction modes (e.g., set 29 of prediction modes as described herein, e.g., with reference to aspect one and two).

[0242] An advantage may be that since a more efficient prediction results from applying sample- to-sample prediction and the transform-domain-to-transform-domain prediction at different prediction gains in different spectral regions.

[0243] According to a first variant, the transform-domain-to-transform-domain prediction 204a, b is spectrally restricted to the second spectral region. As a result, the values (e.g., coefficients) are pre-selected before further processing (e.g., copying values and / or applying a filter kernel), reducing overall coding complexity. According to a second variant, the preliminary transform-domain predictor is spectrally filtered using a transfer function being higher in the second spectral region than compared to the first spectral region. Therefore, the filtering

[0244] FH241108PEP-2025376085fe may be defined in the transform domain (e.g., frequency domain). According to a third variant, filter synthesis is performed using an impulse response which is higher in the second spectral region than compared to the first spectral region. Therefore, the frequency response of the filtering may be defined in the non-transform domain (e.g., time domain).

[0245] Fig. 12a-d show different examples of a first spectral region 61a and second spectral region 61b. Furthermore, exemplary transfer functions 63a, b are shown, but the same principles may be applied to spectral restriction and / or spectral filtering. A horizontal axis shows a frequency and a vertical axis shows exemplarily a gain of a transfer function. However, other frequency dependent parameters may be used.

[0246] Fig. 12a shows a first example of a first and second spectral region 61a, b. The first and second spectral regions 61a, b may be disjoint, e.g., have no overlap. Furthermore, the first and second spectral regions 61a, b, may have a finite frequency range (e.g., having a lower frequency border larger than zero). The transfer functions 63a, b are exemplarily depicted with a constant gain over the respective first and second spectral region 61 ab.

[0247] Fig. 12b shows a second example of a first and second spectral region 61a, b. The first and second spectral region 61a, b may border each other. In other words, the first and second spectral region 61a, b may be distinguished by a single frequency threshold. Furthermore, one (a lower one) of the first and second spectral regions 61a, b may extend to a frequency of zero and / or the other one of the first and second spectral regions 61 , a, b may have no upper limit.

[0248] Fig. 12c shows a third example of a first and second spectral region 61a, b. The first and second spectral regions 61a, b may border each other and both have a finite spectral width (e.g., have an upper limit). Furthermore, one or both of the transfer functions 63a, b may have a slope on or both ends of the respective first and second spectral region 61a, b.

[0249] Fig. 12d shows a fourth example of a first and second spectral region 61a, b. The first and second spectral regions 61a, b may partially overlap (e.g., by less than 50% or 25% or 10% of a smaller spectral range of the first and second spectral region 61a, b).

[0250] The first spectral region and the second spectral regions 61a, b may be disjoint (e.g., spatially separate, e.g., have no spectral overlap). The first spectral region 61a may correspond to a lower frequency range than the second spectral region 61 b. As a result, the spectrally

[0251] FH241108PEP-2025376085fe filtering 300 the preliminary time-domain predictor 214 may realize a low-filter pass and performing the transform-domain-to-transform-domain prediction 204a, b may realize a high-filter pass (with “low” and “high” denoting the relationship between the first and second spectral region 61a, b). It has been found that in some applications, emphasizing lower frequencies for non-transform domain prediction and emphasizing higher frequencies for transform domain prediction may improve prediction quality (e.g., overall decrease required residual signals).

[0252] In other words, the apparatus 12 is configured to perform a prediction in a non-transform domain (e.g., time domain, by performing the sample-to-sample prediction 260) and a prediction in the transform domain (by performing the transform-domain-to-transform-domain prediction 204a, b), wherein the prediction in the non-transform domain emphasizes the first spectral region 61a and the prediction in the transform domain emphasizes the second spectral region 61b. Therefore, the apparatus allows adjusting prediction according to the respective domain.

[0253] The transform-domain-to-transform-domain prediction 204a, b may use already decoded prediction residuals of one (e.g., the only channel or a neighboring channel in case of multiple channels) or more channels. For example, the transform-domain-to-transform-domain prediction 204a, b may be obtained by copying (e.g., optionally rescaling) coefficients of already decoded prediction residuals of one or more channels (e.g., see transform-domain- to-transform-domain prediction 204a). In a different example, transform-domain-to-trans- form-domain prediction 204a, b may be obtained by using a filter-kernel 216, e.g., extending over one (e.g., the only channel or a neighboring channel in case of multiple channels) or more channels.

[0254] The waveform signal 14 may comprise a single channel 21 , or may comprise more than one channel 21 (e.g., as described herein, e.g., with reference to the first and second aspect).

[0255] The waveform signal may be a multi-channel waveform signal 14, the block may be a block 140 of a channel 21 of channels (e.g., the plurality of channels 21a-d) of the multi-channel signal 14, and the transform-domain-to-transform-domain prediction 204a, b may be an inter-channel transform-domain-to-transform-domain prediction 204a, b from one or more ref-

[0256] FH241108PEP-2025376085fe erence channels 202. It is noted, for example, that inter-channel transform-domain-to-trans- form-domain prediction 204a, b may be performed from a transform-domain residual signal of a reference channel 202 (e.g., as described with reference to aspect one and two).

[0257] The apparatus 12 may be configured to select, among a set 29 of prediction modes, a selected prediction mode (e.g., one prediction mode 25 or prediction mode 39) for the block 140, and perform the sample-to-sample prediction 260 for the block 140 using the selected prediction mode.

[0258] It is noted, for example, that owing to the different spectral regions 61a, b where transform- domain-to-transform-domain prediction 204a, b and sample-to-sample prediction 260 have higher prediction gain, respectively, transform-to-transform domain prediction may be less sensitive to prediction mode differences between the block’s channel and the reference channel 202.

[0259] The apparatus 12 may be configured to perform the transform-domain-to-transform-domain prediction 204a, b by spectrally applying a convolutional synthesis filter with a filter kernel 216 which extends into one or more reference channels 202 within the second spectral region 61b and setting the transform-domain predictor 208a to zero in the first spectral region 61a.

[0260] It is noted, for example, that here, the transform-domain-to-transform-domain prediction 204a, b and the correction 212 thereof may be done coefficientwise alternatingly: the filter kernel 216 may yields a predictor for a current coefficient, which is then corrected, so that the filter kernel 216 falls onto already corrected coefficients in the block’s channel and one or more reference channels 202. In other words, already corrected coefficients of the block may influence a correction of to be coded coefficients of the same block.

[0261] The apparatus 12 may be configured to perform the transform-domain-to-transform-domain prediction 204a, b by spectrally copying (e.g., coefficient-wise) from a corrected residual spectrum of a reference channel 202 within the second spectral region 61b and setting the transform-domain predictor 208a, b to zero in the first spectral region 61a, or spectrally copying from a corrected residual spectrum of the reference channel 202 to obtain a preliminary transform-domain predictor and spectrally shaping the preliminary transform-do- main predictor using a transfer function (e.g., a step function) according to the prediction gain of the transform-domain-to-transform-domain prediction.

[0262] FH241108PEP-2025376085fe Fig. 13 shows a schematic view of an apparatus 10 for encoding a waveform signal 14 into a data stream 16. The apparatus 10 (e.g., encoder) may be configured to encode a data stream 16 (e.g., as described with reference to fig. 11) decodable, for example, by the apparatus 12 shown in fig. 10. The apparatus 10 may comprise one or more features of any other apparatus 10 disclosed herein (e.g., with reference to aspect one and two).

[0263] The apparatus 10 is configured to perform sample-to-sample prediction 260 for a block 140CUrrent (or block 140) of the waveform signal 14 (e.g. in fig. 11 more than one channel is shown for illustration only), to obtain a preliminary time-domain block predictor 214, and spectrally filter 300 the preliminary time-domain predictor 214 to obtain a filtered time-do- main block predictor 302.

[0264] The apparatus 10 is configured to perform transform-domain-to-transform-domain prediction 204a, b for the block 140current of the waveform signal 14 to obtain a transform-domain predictor 208a, b, and encode a residual spectrum 210 into the data stream 16, using which the transform-domain predictor 208a, b is correctable (e.g., see fig. 10) to obtain a corrected residual spectrum 224, which, when being subject to a re-transformation 226, yields a timedomain residual signal 228 for correcting 230 the time-domain block predictor (e.g. to obtain a reconstructed signal 304 for the block).

[0265] The apparatus 10 is configured to perform the spectrally filtering 300 the preliminary timedomain predictor 214 using a transfer function (e.g. by FIR filtering) being higher in a first spectral region 61a than compared to a second spectral region 61b, and perform the trans- form-domain-to-transform-domain prediction 204a, b, spectrally restricted to the second spectral region 61 b (e.g. restricting 204a, i.e. only there apply the filtering using kernel 216, e.g., see fig. 3), or by obtaining a preliminary transform-domain predictor and spectrally filtering the preliminary transform-domain predictor using a transfer function being higher in the second spectral region 61 b than compared to the first spectral region 61a to obtain the transform-domain predictor (e.g. in 204b, i.e. multiplying with a corresponding transfer function which might be a step function being zero in the first and 1 in the second spectral region 61 b); or by performing filter synthesis using an impulse response which is higher in the second spectral region 61 b than compared to the first spectral region 61a (e.g. in 204a, i.e. using different filter coefficients for kernel 216 in that same are, in terms of sum of squares or sum of absolutes for instance, smaller in first than in second spectral region 61b).

[0266] FH241108PEP-2025376085fe It is noted, for example, that the spectrally varying prediction gain might be achieved by spectral filtering the time-domain block predictor 214 and restricting, for instance, the trans- form-domain-to-transform-domain prediction 204a, b to the second spectral region 61 b. The transform-domain-to-transform-domain prediction 204a, b may be an inter-channel trans- form-domain-to-transform-domain prediction. The sample-to-sample prediction 260 may use block-wise selection among a set of prediction modes. An advantage may be that since a more efficient prediction results from applying sample-to-sample prediction and the trans- form-domain-to-transform-domain prediction at different prediction gains in different spectral regions 61a, b.

[0267] The apparatus 10 may be configured to obtain the residual spectrum 210 based on a block to be reconstructed (e.g., block 304 or a variation thereof), the filtered time-domain block predictor 302, transform-domain predictor 208a, b. For example, the apparatus 10 may be configured to obtain the residual spectrum 210 based on a combination (e.g., subtraction) of the corrected residual spectrum 224 and the transform-domain predictor 208a, b, wherein, for example, the corrected residual spectrum 224 may be obtained based on a transformation of a time-domain residual signal 228 obtained based on a combination (e.g., subtraction) of the block to be reconstructed and the filtered time-domain block predictor 302.

[0268] The waveform signal may be a multi-channel waveform signal 14, the block 140CUrrent may be a block of a channel 21 of channels (e.g., plurality of channels 21a-f) of the multi-channel signal 14, and the transform-domain-to-transform-domain prediction 204a, b may be an inter-channel transform-domain-to-transform-domain prediction from one or more reference channels 202. It is noted, for example, that the inter-channel transform-domain-to-trans- form-domain prediction 204a, b may be performed from a transform-domain residual signal 206a, b of a reference channel 202.

[0269] The apparatus 10 may be configured to select, among a set 29 of prediction modes, a selected prediction mode for the block 140current, and perform the sample-to-sample prediction 260 for the block 140current using the selected prediction mode. It is noted, for example, that owing to the different spectral regions 61a, b where transform-domain-to-transform-domain prediction and sample-to-sample prediction have higher prediction gain, respectively, trans- form-to-transform domain prediction is less sensitive to prediction mode differences between the block’s channel and the reference channel.

[0270] FH241108PEP-2025376085fe The apparatus 10 may be configured to perform the transform-domain-to-transform-domain 204a, b prediction by spectrally applying a convolutional synthesis filter with a filter kernel which extends into one or more reference channels 202 within the second spectral region 61b and setting the transform-domain predictor to zero in the first spectral region 61a. It is noted, for example, that here, the transform-domain-to-transform-domain prediction 204a, b and the correction thereof may be done coefficientwise alternatingly: the filter kernel 216 yields a predictor for a current coefficient, which is then corrected, so that the filter kernel falls onto already corrected coefficients in the block’s channel and one or more reference channels.

[0271] The apparatus 10 may be configured to perform the transform-domain-to-transform-domain prediction by spectrally copying from a corrected residual spectrum of a reference channel within the second spectral region 61b and setting the transform-domain predictor to zero in the first spectral region 61a, or spectrally copying from a corrected residual spectrum of the reference channel to obtain a preliminary transform-domain predictor and spectrally shaping the preliminary transform-domain predictor using a transfer function according to the prediction gain of the transform-domain-to-transform-domain prediction.

[0272] Any functionalities described herein with reference to apparatus 10, 12 (e.g., of the first, second, and third aspect) may be provided in form of a method, which will be described in the following. Fig. 14 and 15 show methods 400 and 410 related to the first aspect.

[0273] Fig. 14 shows a flow diagram of a method 400 for decoding a multi-channel waveform signal 14 from a data stream 16 using block-based prediction. The method 400 may be performed by any apparatus 12 (e.g., decoder) disclosed herein.

[0274] The method 400 comprises, in step 402, decoding from the data stream 16 a commonality syntax element 13 (e.g. common_pred_mode) indicating for a plurality of channels 21a-f (e.g., channels 21 of one channel group 240) of the multi-channel waveform signal 14, whether, among a set 29 of prediction modes supported by the method 400, one prediction mode 25 is commonly attributed to the plurality of channels 21a-f (e.g. relating to one temporal block 30, i.e. one set 250 of mutually aligned blocks 140, e.g. of one channel group 240).

[0275] FH241108PEP-2025376085fe The method 400 comprises, in step 404, if the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, decoding a set 31 of one or more prediction mode syntax elements (e.g. block_pred_mode) from the data stream 16 which indicate a selected prediction mode 33 out of the set 29 of prediction modes, wherein the selected prediction mode 33 is the one prediction mode 25, or appointing a selected prediction mode indicated by a set 31 of one or more prediction mode syntax elements decoded for a first channel (e.g., channel 21a) among the plurality of channels 21a-f the one prediction mode 25, or using a default prediction 35 mode among the set 29 of prediction modes as the one prediction mode 25, and decoding each of the plurality of channels 21 a-f using the one prediction mode 25.

[0276] The method 400 comprises, in step 406, if the commonality syntax element does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f, decoding, from the data stream 16, for each of the plurality of channels 21 a-f, the set 31 of one or more prediction mode syntax elements, which indicate a selected prediction mode 39 out of the set 29 of prediction modes for the respective channel 21 , and decoding each of the plurality of channels 21 a-f using the selected prediction mode 39 for the respective channel 21.

[0277] Fig. 15 shows a flow diagram of a method 410 for decoding a multi-channel waveform signal 14 into a data stream 16 using block-based prediction. The method 410 may be performed by any apparatus 10 (e.g., encoder) disclosed herein.

[0278] The method 410 comprises, in step 412, encoding into the data stream 16 a commonality syntax element (e.g. common_pred_mode) indicating for a plurality of channels 21 a-f (e.g., channels 21 of one channel group 240) of the multi-channel waveform signal 14, whether, among a set of prediction modes supported by the method 410, one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f (e.g. relating to one temporal block 30, i.e. one set of mutually aligned blocks 140, e.g. of one channel group 240).

[0279] The method 410 comprises, in step 414, if the commonality syntax element indicates that one prediction mode is commonly attributed to the plurality of channels 21 a-f, encoding a set of one or more prediction mode syntax elements (e.g. block_pred_mode) into the data stream 16 which indicate a selected prediction mode out of the set of prediction modes, wherein the selected prediction mode is the one prediction mode, or a set of one or more prediction mode syntax elements encoded for a first channel among the plurality of channels

[0280] FH241108PEP-2025376085fe 21a-f is to be appointed the one prediction mode, or a default prediction mode among the set of prediction modes is to be used as the one prediction mode, and encoding each of the plurality of channels 21a-f using the one prediction mode.

[0281] The method 410 comprises, in step 416, if the commonality syntax element 13 does not indicate that one prediction mode 25 is commonly attributed to the plurality of channels 21a- f, encoding, into the data stream 16, for each of the plurality of channels 21 a-f, the set 31 of one or more prediction mode syntax elements, which indicate a selected prediction mode 39 out of the set 29 of prediction modes for the respective channel 21 , and encoding each of the plurality of channels 21 a-f using the selected prediction mode for the respective channel.

[0282] The methods 400, 410 therefore realize the aspect of a common prediction mode. It is noted, for example, that the commonality syntax element 13 may be transmitted prior to first set of one or more prediction mode syntax elements or subsequently thereto. It could also be sent in-between, in case of more than one prediction mode syntax element. The state of the commonality syntax element 13 indicating commonality might even be indicative of the common prediction mode. An advantage may be that the method 410 (e.g., encoder) may efficiently signal common prediction mode for plurality of channels 21a-f. Additional overhead is more than compensated by necessitating the signaling of the set of one or more prediction mode syntax elements merely once in cases of commonality.

[0283] Fig. 16 shows a flow diagram of a method 420 for decoding multi-channel waveform signal 14 from a data stream 16 using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual decoding. The method 420 may be performed by any apparatus 12 (e.g., decoder) disclosed herein.

[0284] The method 420 comprises, in step 422, decoding from the data stream a further commonality syntax element 45 indicating for a plurality of channels 21 a-f of the multi-channel waveform signal 14, whether, among a set 51 of transform domains supported by the method 420, one transform domain 53 is commonly attributed to the plurality of channels 21 a-f.

[0285] The method 420 comprises, in step 424, if the further commonality syntax element 45 indicates that one transform domain 53 is commonly attributed to the plurality of channels 21a- f, decoding each of the plurality of channels 21 a-f using the one transform domain 53 for the transform-based prediction residual decoding.

[0286] FH241108PEP-2025376085fe The method 420 comprises, in step 426, if the further commonality syntax element 45 does not indicate that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, decoding each of the plurality of channels 21a-f using a selected transform domain, which is channel-individually selected out of the set 51 of transform domains, for the transform-based prediction residual decoding.

[0287] Fig. 17 shows a flow diagram of a method 430 encoding a multi-channel waveform signal 14 into a data stream 16 using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual encoding. The method 430 may be performed by any apparatus 10 (e.g., encoder) disclosed herein.

[0288] The method 430 comprises, in step 432, encoding into the data stream 16 a further commonality syntax element 45 indicating for a plurality of channels 21a-f of the multi-channel waveform signal 14, whether, among a set 51 of transform domains supported by the apparatus, one transform domain 53 is commonly attributed to the plurality of channels 21 a-f.

[0289] The method 430 comprises, in step 434, if the further commonality syntax element 45 indicates that one transform domain 53 is commonly attributed to the plurality of channels 21a- f, encoding each of the plurality of channels 21 a-f using the one transform domain 53 for the transform-based prediction residual encoding.

[0290] The method 430 comprises, in step 436, if the further commonality syntax element 45 does not indicate that one transform domain 53 is commonly attributed to the plurality of channels 21 a-f, encoding each of the plurality of channels 21a-f using a selected transform domain, which is channel-individually selected out of the set 51 of transform domains, for the transform-based prediction residual encoding.

[0291] The methods 420, 430 therefore realize the aspect of a common transform mode. An advantage may be that the encoder may efficiently achieve transform equality thereby yielding a more effective singling which likely efficiently takes advantage from inter-channel trans- form-domain residual prediction.

[0292] Fig. 18 shows a flow diagram of a method 440 for decoding a waveform signal 14 from a data stream 16. The method 440 may be performed by any apparatus 12 (e.g., decoder) disclosed herein.

[0293] FH241108PEP-2025376085fe The method 440 comprises, in step 441 , performing sample-to-sample prediction 260 for a block 140CUrrent of the waveform signal (e.g. in Fig. 3 more than one channel is shown for illustration only), to obtain a preliminary time-domain block predictor 214.

[0294] The method 440 comprises, in step 300, spectrally filtering the preliminary time-domain predictor to obtain a filtered time-domain block predictor 302, in step 442, performing trans- form-domain-to-transform-domain prediction 204a, b for the block of the waveform signal to obtain a transform-domain predictor 208a, b, and in step 443, decoding a residual spectrum from the data stream 210.

[0295] The method 440 comprises, in step 212, correcting the transform-domain predictor 208a, b using the residual spectrum 210 to obtain a corrected residual spectrum 224, in step 444, subjecting the corrected residual spectrum 224 to a re-transformation 226 to obtain a timedomain residual signal 224, and in step 230, correcting the time-domain block predictor using the time-domain residual signal (e.g. to obtain a reconstructed signal 304 for the block).

[0296] The method 440 further comprises, in step 445 performing the spectrally filtering (300) the preliminary time-domain predictor (214) using a transfer function (e.g. by FIR filtering) being higher in a first spectral region than compared to a second spectral region.

[0297] The method 440 further comprises, in step 446, performing the transform-domain-to-trans- form-domain prediction 204a, b spectrally restricted to the second spectral region (e.g. restricting 204a, i.e. only there apply the filtering using kernel 216), or by obtaining a preliminary transform-domain predictor and spectrally filtering the preliminary transform-domain predictor using a transfer function being higher in the second spectral region than compared to the first spectral region to obtain the transform-domain predictor (e.g. in 204b, i.e. multiplying with a corresponding transfer function which might be a step function being zero in the first and 1 in the second spectral region); or by performing filter synthesis using an impulse response which is higher in the second spectral region than compared to the first spectral region (e.g. in 204a, i.e. using different filter coefficients for kernel 216 in that same are, in terms of sum of squares or sum of absolutes for instance, smaller in first than in second spectral region).

[0298] FH241108PEP-2025376085fe Fig. 19 shows a flow diagram of a method 450 for encoding a waveform signal 14 into a data stream 16. The method 450 may be performed by any apparatus 10 (e.g., encoder) disclosed herein.

[0299] The method 450 comprises, in step 451 , performing sample-to-sample prediction 260 for a block 140CUrrent of the waveform signal (e.g. in Fig. 3 more than one channel is shown for illustration only), to obtain a preliminary time-domain block predictor 214, and in step 300, spectrally filtering the preliminary time-domain predictor to obtain a filtered time-domain block predictor 302.

[0300] The method 450 comprises, in step 452, performing transform-domain-to-transform-domain prediction 204a, b for the block of the waveform signal to obtain a transform-domain predictor 208a, b and in step 453, encoding a residual spectrum into the data stream 16, using which the transform-domain predictor 208a, b is correctable to obtain a corrected residual spectrum 224, which, when being subject to a re-transformation 226, yields a time-domain residual signal 228 for correcting 230 the time-domain block predictor (e.g. to obtain a reconstructed signal 304 for the block).

[0301] The method 540 comprises, in step 454, performing the spectrally filtering 300 the preliminary time-domain predictor 214 using a transfer function (e.g. by FIR filtering) being higher in a first spectral region 61a than compared to a second spectral region 61b.

[0302] The method 540 comprises, in step 455, performing the transform-domain-to-transform- domain prediction 204a, b spectrally restricted to the second spectral region 61b (e.g. restricting 204a, i.e. only there apply the filtering using kernel 216), or by obtaining a preliminary transform-domain predictor and spectrally filtering the preliminary transform-domain predictor using a transfer function being higher in the second spectral region 61b than compared to the first spectral region 61a to obtain the transform-domain predictor (e.g. in 204b, i.e. multiplying with a corresponding transfer function which might be a step function being zero in the first and one in the second spectral region); or by performing filter synthesis using an impulse response which is higher in the second spectral region 61 b than compared to the first spectral region 61a (e.g. in 204a, i.e. using different filter coefficients for kernel 216 in that same are, in terms of sum of squares or sum of absolutes for instance, smaller in first than in second spectral region).

[0303] FH241108PEP-2025376085fe It is noted, for example, that the spectrally varying prediction gain might be achieved by spectral filtering the time-domain block predictor and restricting, for instance, the transform- domain-to-transform-domain prediction to the second spectral region. The transform-do- main-to-transform-domain prediction may be an inter-channel transform-domain-to-trans- form-domain prediction. The sample-to-sample prediction may use block-wise selection among a set of prediction modes. An advantage may be that since a more efficient prediction results from applying sample-to-sample prediction and the transform-domain-to-trans- form-domain prediction at different prediction gains in different spectral regions. The methods 440 and 450 may realize an aspect of different spectral ranges for prediction.

[0304] Any method disclosed herein may further include one or more steps of storing the data stream 16, transmitting the data stream 16, receiving the data stream 16, receiving the multi-channel waveform signal 14, storing the multi-channel waveform signal 14, and out- putting the multi-channel waveform signal 14.

[0305] Further is provided a computer program (e.g., computer program product), which may be stored on a computer-readable medium (e.g., transitory storage medium). The computer program comprises instructions that, when running on one or more processors (e.g., microprocessors) perform any method disclosed herein.

[0306] Further is provided a data stream 16 (e.g., any data stream 16 disclosed herein). The data stream 16 may be stored on a computer-readable medium (e.g., transitory storage medium). The data stream 16 has encoded therein a digital wave form signal 14 using any apparatus 10 (e.g., encoder, e.g., any encoding method) disclosed herein.

[0307] In the following exemplary embodiments of the three aspects will be described. It is noted that the three aspects are not limited to these exemplary embodiments and that different combination of features are possible. Furthermore, any feature disclosed in the following can be freely combined in any combination with any of the disclosure above, a framework described further below, or the disclosure of the claims.

[0308] Concepts are described which efficiently combine time-domain and frequency-domain prediction in multi-channel waveform coding.

[0309] Introduction

[0310] FH241108PEP-2025376085fe Digital waveform signals (e.g., multi-channel waveform signal 14), such as biophysical (e. g., medical), geophysical (e. g., seismic), or acoustic (e. g., audio) signals, often comprise a large number of channels. This is particularly true for electroencephalographic (EEG) or higher-order ambisonic (HOA) signals, to name a few. Encoding and / or decoding such multichannel waveform signals, e.g., for data compression purposes typically involves, e.g., an application of time-domain signal prediction methods such as, e.g., long-term prediction (LTP) or, as it is also referred to sometimes, block matching (BM), e.g., followed by time-to- frequency transformation of the resulting per-channel prediction residual waveform signal using, e.g., a trigonometric transform such as the discrete cosine transform (DOT). In modern waveform codecs like AC-4, a frequency-domain prediction may further be applied to the transform-domain (possibly LTP or BM residual) samples, e.g., in an intra or inter-channel fashion to minimize remaining signal redundancy before the coding stage.

[0311] Motivation

[0312] When frequency-domain inter-channel, i. e. cross-channel, prediction is applied in a certain block or frame f of a multi-channel waveform signal, it was found that the prediction gain can be largest, i. e., said cross-channel prediction may work best, e.g., when all transformdomain samples (e.g., coefficients) included in the derivation of the prediction signal for a certain channel (e.g., of the plurality of channels 21a-f) are represented in the same "residual domain", namely

[0313] •a frequency-domain (e.g., transformation domain) representation of the direct signal domain, where no time-domain signal prediction like LTP or BM is used and the, e. g., DCT is applied directly on the input samples, or

[0314] •a frequency-domain representation of a common-predictor residual signal domain, where in each channel the same time-domain signal prediction, e. g. always LTP or always BM, is applied.

[0315] However, using no or the same time-domain prediction method in a frame f across multiple channels (e. g. a group of adjacent channels, e.g., channels 21 of a channel group 240) of a multi-channel waveform signal may cause, e.g., redundancy in the side information signalled to recover the input signal representation, e.g., on the decoder side (i.e. , prediction parameters needed during decoding). Means for efficient combination and coding of timedomain and frequency-domain prediction parameters are, therefore, desirable but not yet disclosed in the state of the art, especially for the described case of combined LTP or BM and AC-4- style prediction.

[0316] FH241108PEP-2025376085fe Summary or Outline of underlying ideas

[0317] To achieve the above-mentioned desired efficient combination and coding, according to an embodiment, e.g., for a frame f or an entire waveform sequence (e.g., or other units such as temporal block 30 or set 250 of mutually aligned blocks), 1) signal a common prediction flag (e.g., commonality syntax element 13), e.g., at the start of a channel group (e.g., or other locations such as with or at the start of a first channel), indicating whether the same (or no), e.g., time-domain prediction (e.g., one prediction mode 25) is used in each channel (e.g., of the plurality of channels 21 a-f), and / or a common transform flag (e.g., further commonality syntax element 45) at the start of a channel group (e.g., or other locations such as with or at the start of a first channel), indicating whether the same (or no), e.g., trigonometric transform (e.g., one transform domain 53) is applied in each channel (e.g., of the plurality of channels 21 a-f), of said group (e.g., channel group 240), e.g., and 2) avoid a redundant signalling of identical time-domain prediction or trigonometric-transform parameters for f in a channel group (e.g., channel group 240) in cases where the respective common flag (e.g., commonality syntax element 13, e.g., further commonality syntax element 45) indicates "same prediction" (e.g., the commonality syntax element 13 indicates that one prediction mode 25 is commonly attributed to the plurality of channels 21 a-f) respectively "same transform" (e.g., further commonality syntax element 45 indicating that one transform domain is commonly attributed to the plurality of channels 21 a-f). Details on this proposal as well as preferred embodiments are described in the following 3 sections (e.g., Detailed Options for Signalling of Common Flags, Preferred Embodiment of Common Prediction Mode, Preferred Embodiment of Common Transform Mode, Alternative to Usage of Common Flags). It is noted that, therein, the time-domain prediction may, equivalently, be referred to as block prediction (e.g., and vice versa).

[0318] Detailed Options for Signalling of Common Flags

[0319] According to an embodiment, the proposed common prediction flag may be signalled as part of the side information, for example, for the first channel in a channel group (e.g., channel group 240), i. e., for each channel with an index c being zero or, more generally, an integer multiple of a constant number, such as 4 (either being predefined or signalled in a bitstream header, e.g., or any other integer number). The same may apply, additionally or alternatively, for the common transform flag. In both cases, the flag signalling may be achieved, e.g., simply by transmitting in / receiving from the bitstream (e.g., data stream 16)

[0320] FH241108PEP-2025376085fe one bit per such flag, the value of which indicates that the respective flag is on (e.g., "common", value 1) or off (e.g., "not common", value 0, e.g., or vice versa). However, each of these flags may also be subjected to a context adaptive binary arithmetic coding.

[0321] For a channel index c being zero (e.g., for a first channel 21) or said integer multiple of a constant number (preferably, a power of 2, especially in cases where dependent-channel mask elements like depChMask are being used), the common prediction and / or common transform flags may be signalled, in the bitstream, e.g., directly before or after the respective prediction mode and / or transform mode elements, respectively, for c.

[0322] Preferred Embodiment of Common Prediction Mode

[0323] According to an embodiment, given, for frame / block f and channel c, a signalled block prediction mode (e.g., out of the set 29 of prediction modes, e. g., DC value prediction, linefitting prediction, block matching prediction, or no block prediction), e.g., it possible to afterwards signal dedicated block prediction parameters (e. g., block matching time offsets, or lags), e.g., when the signalled prediction mode allows for parameter guided control of the prediction process. Regarding the combination with the common prediction flag, two exemplary usage options can be envisioned, with c representing said channel whose index is zero or said integer multiple of a constant number:

[0324] •When the common prediction flag is on (e. g., value 1), both the prediction mode and any dedicated block prediction parameters, e.g., for f and c are also used, during the prediction processes, in all other channels, e.g., of the group to which c belongs (e.g., appointing a selected prediction mode indicated by a set of one or more prediction mode syntax elements decoded for a first channel 21a among the plurality of channels 21a-f the one prediction mode 25). Also, e.g., no further prediction mode elements or dedicated block prediction parameters (other than for c, e.g., for channels 21 b-f) are signalled in said channel group.

[0325] •When common prediction is on, the prediction mode for f and c is also used in all other channels of the group to which c belongs, and no further prediction mode elements are signalled in said channel group. However, if the signalled prediction mode allows for parameter guided control (e.g., for each of one or more parametrized prediction modes of the set of prediction modes), e.g., dedicated block prediction parameters are still signalled for each channel in the group, preferably as part of any other channel specific and individual side information in the bitstream.

[0326] Preferred Embodiment of Common Transform Mode

[0327] FH241108PEP-2025376085fe According to an embodiment, given, for f and c, e.g., a trigonometric-transform mode signalled in the bitstream (e. g., DCT, DST, or no transform = transform skip), when the common transform flag is on, said trigonometric transform for c is also used, during the transformation processes, in all other channels of the group to which c belongs and no further trigonometric-transform mode elements are signalled in that channel group (e.g., one transform domain is commonly attributed to the plurality of channels 21a-f).

[0328] Alternative to Usage of Common Flags

[0329] In the Motivation section, it was noted that the frequency-domain prediction is often found to work optimally, e.g., when the "residual domain" is the same in all channels contributing to (i.e. included in) the frequency-domain prediction process (e.g., inter-channel transformdomain residual prediction 204a; 204b), i.e., when the same time-domain prediction, if any, preceding the forward trigonometric transform (to reach said frequency domain) is applied in all said channels. However, it was also found, e.g., that the frequency-domain prediction often performs well only or particularly in higher frequencies, i. e., on higher-index residual samples in the frequency domain, while, e.g., the time-domain block prediction preceding it (on the encoder side) often works well only or particularly in lower frequencies, since most of the signal energy typically resides in low frequencies. Hence, one may devise an alternative to the above-described synchronization of the time-domain prediction across the channels, namely,

[0330] •instead of signalling the common prediction flag, as described above, one may apply the time-domain (e.g., time-domain predictor 214) and the frequency-domain predictors (e.g., ) transform-domain predictor 208a, b) in different, preferably disjoint spectral regions (e.g., first and second spectral ranges 61a, b),

[0331] •if that alternative is implemented, one may use, e.g., lowpass filtering in the time-domain prediction process to restrict said block prediction to low frequencies (e.g., spectrally filtering 300 using a transfer function (e.g. by FIR filtering) being higher in a first spectral region 61a than compared to a second spectral region 61b), and / or one may let the frequencydomain predictor operate only above some threshold sample index (e.g., lower end of the second spectral region 61b) denoting a high frequency (e.g., using a transfer function being higher in the second spectral region 61 b or performing filter synthesis using an impulse response which is higher in the second spectral region 61 b).

[0332] FH241108PEP-2025376085fe In this way, and assuming, e.g., that the lowpass filter and the spectral threshold sample index are chosen carefully (the filter's cutoff frequency approaches or matches the frequency of the threshold sample index), the time-domain prediction is effective only in lower frequencies, leaving higher frequencies unaffected. As a result, the higher frequencies of the trigonometrically transformed block signals in each of said channels are not a prediction residual but represent the "direct signal domain" noted in the Motivation section, i. e., are by definition domain-synchronized across said channels, as desired.

[0333] It is noted that low-pass filtering may already be supported, e.g., by time-domain predictors such as LTP, BM, or time-domain cross-channel prediction (CCP). However, filtering may be forbidden, or disabled, by a high-level syntax flag such that only, e. g., LTP or BM or CCP without filtering may be allowed for a given waveform sequence or interval therein. In that case, it may be desirable to resort to the usage (and signalling) of a common prediction flag (e.g., commonality syntax element 13) in the first channel of each channel group, as described.

[0334] It is noted, also, that the frequency-domain predictor may, e.g., represent a predictive filtering operation that may execute the filtering process in the direction from low to high frequencies (i. e., beginning at or above the spectral threshold sample index) or in the reverse direction from high to low frequencies (ending at or above the spectral threshold sample index). The direction doesn't affect the concept described herein.

[0335] Fig. 20 shows an exemplary signaling configuration for one prediction mode 25 is commonly attributed to the plurality of channels 21a-f. In other words, fig. 20 may show an exemplary signalling configuration for preferred “Common Block Prediction” Embodiment. A left side of fig. 20 exemplarily shows a common block prediction mode and associated parameters and the right side exemplarily shows only common block prediction mode information.

[0336] The left side shows a first variation, wherein for a frame f, a parameter common_block_predfis initialized as 0. Then, for each channel c, it is checked, whether a channel is not dependent (or independent) based on “(c & depChMask) == 0” or whether a common prediction mode is switched off yet based on “common_block_predf== 0”. If either condition is true (e.g., for a first channel 21a, e.g., a non-dependent channel), a prediction mode of the current channel is parsed (e.g., Read block_pred_modef,c). In case that this prediction mode is LTP or BM, corresponding prediction parameters are read (e.g., read block_pred_parame- tersf,c())- If neither condition is true, a prediction mode and parameters of a previous channel

[0337] FH241108PEP-2025376085fe are set (e.g., set block_pred_modef,c= block_pred_modef,c-i; set block_pred_parametersf,c= block_pred_parametersf,c-i). Then, for a non-dependent channel, common_block_predf (e.g., commonality syntax element 13) is read (e.g., read common_block_predf) and set for the next channel. It is noted that in the first variation, the common_block_predf flag was read after reading or assigning the block_pred_modef,cfor the current channel.

[0338] Fig. 20 shows on the right side a second alternative, wherein for a non-dependent channel, a common_block_predf (e.g., commonality syntax element 13) is read from the start (e.g., read common_block_predf). If the channel is non-dependent and the read flag com- mon_block_predfis zero (e.g., indicating no common prediction mode), the prediction mode of the previous channel c-1 is used. Otherwise, if the prediction mode is LTP or BM (e.g., block_pred_modef,c== LTP or BM), corresponding prediction parameters are read (e.g., read block_pred_parametersf,c()).

[0339] General framework

[0340] The above description is extended in the following by the presentation of implementation examples. Before this, however, the description proceeds with a presentation of a possible framework or codec into which the embodiments described above as well as the examples described further below may be built into. Many details described in this framework are, however, optional when being combined with any of the above or subsequently described embodiments. To be more precise, the framework is described with respect to Fig. 21 which shows an encoder (e.g., apparatus 10) for encoding a multi-channel digital signal 14 into a data stream 16 as well as decoder 12 (e.g., apparatus 12) for decoding the multi-channel digital signal 14 from data stream 16. This description of Fig. 21 shall be seen as a presentation of new embodiments of the present application which result when combining any of the embodiments described above or any of the examples described subsequently or even any of the claimed subject matters is combined with the decoder 12 or encoder 10 of Fig. 21 either by adopting all details / functionalities described with respect to Fig. 21 or with leav- ing-out some of the details / functionalities described with respect to Fig. 21. Sometimes such “optional” features of Fig. 21 are explicitly identified as being optional with respect to the combination of the previously and subsequently described embodiments, but the just-mentioned possible combinations of the previously / subsequently explained embodiments with the description of Fig. 21 shall not be restricted to the these explicitly identified variations of Fig. 21 in terms of leaving-out certain features.

[0341] FH241108PEP-2025376085fe In Fig. 21 , the multi-channel digital signal 14 is illustrated by way of an array of samples with the samples being illustrated as small squares 18. Each line / row corresponds to a certain channel (e.g., channel 21) of the multi-channel digital signal 14. Each channel of signal 14 may have associated therewith a respective channel ID and Fig. 21 shows these channels as being ordered according to their channel ID along vertical axis 20 which, thus, corresponds to a “source” channel axis 20. The horizontal axis 22 corresponds to time so that samples 18 forming one column, or being horizontally aligned, are samples belonging to one common time instant. Such set / column of temporally co-located samples 18 is illustrated in Fig. 21 at 24.

[0342] Each channel, thus, forms a digital time-varying signal or time / amplitude or time-to-ampli- tude signal. The multi-channel digital signal m might have been obtained by at least one of Electrocardiography, Electroencephalography, Electromyography or seismic measurement. Differently speaking, the multi-channel digital signal might be a bio-physiological waveform data such as an electroencephalography (EEG) signal, an electrocardiogram (ECG), or an electromyography (EMG) signal, or seismic waveform data. However, each channel / signal might alternatively be another sort of waveform signal data such as scalar media data such as an audio signal and the signal 14 might be a multi-channel audio signal.

[0343] Fig. 21 illustrates the option according to which signal 14 is not coded directly, i.e., in the original domain 26 (e.g., non-transform domain), but in a so-called “coded domain” 28 (e.g., transform domain) which might differ from the original domain 26 by one or more of 1) channel transformation, 2) channel permutation and 3) temporal mutual channel alignment. The channel transformation, if applied, transforms, per sample time instant, a set or column 24 of samples from domain 26 to domain 28. Thus, in domain 28, the sample pitch and the time axis is the same as in domain 26, but the meaning of the channels is different, i.e., the “source” channels of domain 26 become transformed channels in domain 28. Accordingly, the vertical axis in Fig. 21 for domain 28 is denoted as 32. Note that the channel transformation might leave the number of channels unchanged so that there is the same number of channels in domain 26 as well as domain 28, but different approaches are also possible. Generally, the channel transformation would aim at reducing redundancy and trying to condense the channels’ energy onto a fewer number of channels in domain 28. As said, the channel transformation is optional. Accordingly, in general terms, the channels in domain 28 are called “coded channels” in order to distinguish them from the “original” or “source” channels of digital signal 14 in domain 26. The permutation is also optional and may be used in combination with, or without, the channel transformation. If used in combination with

[0344] FH241108PEP-2025376085fe the channel transformation, the permutation may be performed prior to and / or or subsequent to the channel transformation in order to permute / sort the source channels prior to transformation and the coded channels subsequent to the channel transformation. The channel transformation might be a DCT, DST, FFT or any other transformation. The temporal mutual alignment is also optional and might be seen as a constant temporal alignment between the source channels or the coded channels.

[0345] The module in encoder 10 performing the one or more of channel transformation, channel permutation and temporal mutual alignment is indicated in Fig. 21 as block 34. Side information 36 might be used in order to signal information on one or more of the following: 1) The channel transformation used, 2) information on the permutation(s) among the source channels and / or coded channels and 3) information on the mutual temporal alignment / de- lays between the source channels or coded channels wherein the temporal mutual alignment might be restricted to full sample precision. A corresponding block 38 in decoder 12 performs the reverse step, i.e. , performs one or more of: 1) a channel retransformation, 2) a re-permutation of the source channels and / or coded channels and 3) a temporal re-align- ment of the source channels or coded channels. Note, that if no channel transformation takes place, the coded channels are, in fact, equal to the source channels except for being temporally mutually aligned or being differently sorted due to permutation. Block 38 might be controlled by the before-mentioned side information 36.

[0346] Thus, the “actual coding” relates to the coded channels in domain 28. In the coded domain 28, the coded channels are depicted in Fig. 21 as lines or rows of samples 40, each extending along time axis 22, the coded channels being depicted one on top of the other along coded channel axis 32 - potentially ordered according to a coded channel ID they have associated therewith - so as to result into an array of samples 40. Again, although Fig. 21 depicts the case that the number of source channels equals the number of coded channels, the number might be different. Further, if channel transformation is used, while there is no longer a clear association between source channels on the one hand and coded channels on the other hand, the temporal association remains: For each temporally co-located samples 24, there is a corresponding temporally co-located set 42 of samples 40 of the coded channels, wherein the set 42 in domain 28 is a column and might be a set of horizontally mutually offset samples in case of, and according to, the mutual temporal alignment, if applied. In case of Fig. 21 , it has been assumed that no such temporal alignment took place so that both sets 42 and 24 are pure columns in the time / channel representation.

[0347] FH241108PEP-2025376085fe The actual coding is done in units of so-called temporal blocks 30. The term “block” or “temporal block” 30 is used so as to denote both a temporal portion of the multi-channel signal in domain 28, i.e., the set of coded channels, as well as a temporal portion of a certain coded channel. That is, for each temporal block 30, each coded channel has a temporal block such as block 140 depicted for some temporal block 30c and same are mutually colocated. The coding is done sequentially along these blocks 140, by following a coding / de- coding order, which traverses the blocks 140 temporal block 30 by temporal block 30 with traversing temporally co-located blocks of the coded channels along a channel order corresponding to the order of the coded channels along axis 32. This coding / decoding order is illustrated in Fig. 21 at 60. That is, in case of temporal block 140 being the block currently to be coded / decoded, the previously decoded / encoded temporal blocks include all preceding temporal blocks of all coded channels as well as the temporally co-located temporal blocks of coded channels preceding the coded channel 92 of temporal block 140 in channel order. These previously coded / decoded temporal blocks and their samples are illustrated in Fig. 21 by way of shading. In this regard, note that in Fig. 21 , merely one temporal block 140 has been illustrated explicitly in order to reduce the complexity of Fig. 21. Thus, in the specification herein, reference sign 140 is sometimes used to indicate the currently en- coded / decoded temporal block or to stand representatively for all temporal blocks. Further, as depicted in Fig. 21 , the partitioning of signal 14 into temporal blocks 30 and 140, respectively, might be done in a manner so that these blocks 30 and 140, respectively, are nonoverlapping.

[0348] The actual coding in units of the temporal blocks 140 is performed predictively. That is, the encoder 10 comprises a block predictor 62 which predicts the samples of the currently coded temporal block 140, thereby yielding a prediction signal 64, and the prediction residual 66 formed by a subtraction between the actual sample values of temporal block 140 and the predicted samples of prediction signal 64 formed at a subtractor 68 is coded into the data stream 16 by residual coder 70. The residual coding in residual coder 70 may, or may not, involve a coding error by means of quantization. In any case, block predictor 62 uses the reconstructable version as being available by previously coded temporal blocks in order to obtain the prediction signal 64. This reconstructable version 72 might be derived at encoder 10 by means of a residual decoder 74 which reverses, potentially under coding loss, such as quantization, e.g. by means of dequantization, the residual signal 76 as coded into data stream 16, and an adder 78 which sums-up prediction signal 64 and the reconstructable residual signal 80 as obtained by residual decoder 74. To be more precise, let’s call the channel-individual temporal blocks 140 subblocks with temporally collocated subblocks of

[0349] FH241108PEP-2025376085fe all channels forming a temporal block 30. Then, the prediction in module 62 or, to be more precise, the prediction at encoder and decoder, is performed in units of the subblocks 140, i.e. subblock wise. The encoder is free to choose different prediction modes for the subblocks within one block 30. As explained in more detail herein, within one block 30, one subblock 140 may be predicted based on one or more subblocks previously - according to the decoding order 60 - en / decoded within this block 30, while another subblock 140 within that block 30 might be coded / decoded based on the previously en / decoded subblock 140 of the same channel (but within the previous block 30). The transform residual en / decoding is then performed subblock wise by use of a one-dimensional transform signaled in the data stream as described hereinbelow.

[0350] The decoder 12 decodes the coded channels from data stream 16 in a corresponding manner, i.e., in units of the temporal blocks 30 or in temporal blocks 140, respectively, and using predictive decoding. To this end, the decoder 12 comprises a residual decoder 82, an adder 84 and a block predictor 86 which correspond to, and are mutually connected in the same manner as, elements 74, 78 and 62 of encoder 10. That is, the residual decoder 82 derives from the residual signal 76 in data stream 16 the reconstructable residual signal 80 for a currently decoded temporal block 140 which is then subject to addition with prediction signal 64 derived by block predictor 86 for temporal block 140 on the basis of the reconstructed version 72 of previously decoded temporal blocks at adder 84. The output of adder 84, thus, yields the reconstructed version 72 of the currently decoded temporal block 140 and becomes part of the pool of already decoded samples of previously decoded temporal blocks when the temporal blocks of the coded channels are, in this manner, traversed along cod- ing / decoding order 60 so as to reconstruct the coded channels in the coded domain 28.

[0351] Note that the above description concentrated on the so-called sample prediction where samples of a current block 140 are predicted based on reconstructed samples of one or more previously decoded blocks, but coding inter dependencies, namely intra-channel and inter-channel coding dependencies may be exploited not only in terms of sample prediction, but also in terms of other coding tools involving, for instance, parameter prediction and / or context derivation.

[0352] In order to enable a high degree of random access capability, some of the temporal blocks 30 may be coded in a random access manner meaning that the coded channels therein are coded independent from previous temporal blocks 30. Imagine, for instance, that temporal

[0353] FH241108PEP-2025376085fe blocks 30b and 30e are random access temporal blocks. Then, none of the temporal channel blocks 140 in temporal block 30b as well as 30e would depend on any preceding temporal block 140 and no coding dependency would cross these temporal blocks 30b and 30e, that is no temporal block 140 within any of temporal block 30b-30d would be coded depending on any block 140 temporally preceding temporal block 30b, and no temporal block 140 within any of temporal block 30e and following would be coded depending on any block 140 temporally preceding temporal block 30e.

[0354] Thus, in other words, coding dependencies are restricted so as to not reach-out beyond the border of a random access temporal block 30b and 30e towards any preceding temporal block 30. Such restriction might also hold for intermediate temporal blocks 30c to 30d between random access temporal blocks 30b and 30e in that same may not depend on any temporal block preceding the leading one among the random access temporal blocks 30b and 30e, here block 30b. Accordingly, leading temporal borders of the random access temporal blocks 30b and 30e are indicated by bold lines in Fig. 21. In a variant, the restriction is not valid for all en / decoding stages. For instance, while the grouping might hold true for prediction, but the residual en / decoding dependencies might cross borders between channel groups. It might be the case, for instance, that for the entropy coding and decoding, all channels are coded jointly, i.e. using a single arithmetic coding engine, but that for the sake of prediction and reconstruction, the channels are grouped as described into independent groups such that, after entropy decoding, each such group can be reconstructed completely independently from each other group. This means that no prediction of sample values or any other information is supported between different channel groups.

[0355] Further, it might be that the coding of the coded channels also interrupts or restricts interchannel dependencies. For example, one or more of the coded channels might be coded as random access coded channels so that same do not use inter-channel dependencies, but merely intra-channel dependencies. The restriction of inter-channel coding dependencies might follow the channel order 32: that is, coding of these random access coded channels and the intermediate coded channels therebetween would be restricted so as to not reach-out beyond such a random access coded channel toward any coded channel preceding that random access coded channel in channel order along axis 32. Two such random access coded channels 88a and 88b and the resulting inter-channel dependency borders are illustrated in Fig. 21. Note that the restriction of inter-channel dependencies might be differently and is illustrated here merely as an example where the definition of, along channel order 32, interspersed random access channels 88a and 88b defines channel groups

[0356] FH241108PEP-2025376085fe covering contiguous channels along the channel order 32. Other groups of channels might be defined, which do not necessarily follow the channel order 32, and inter-channel dependencies might be restricted not to render any channel of one group dependent on a channel of any other group, and within each group the inter-channel dependencies may also by restricted or each channel might by coded inter-channel dependent on any previously coded channel within its channel group.

[0357] The block predictor 62 and 86 of encoder 10 and decoder 12, respectively, operate synchronously, i.e., they generate the same prediction signal 64 based on the previously en- coded / decoded samples of previously encoded / decoded temporal blocks 140. On encoder side 10, the prediction for a certain temporal block 140 may be accompanied or determined by one or more prediction parameters. Same might be determined on encoder side based on a rate / distortion optimization. These prediction parameters 90 are coded into data stream 16 and they are decoded from data stream 16 and used by block predictor 86 so as to perform the same prediction.

[0358] It might be that encoder 10 and decoder 12 support more than one prediction mode. For instance, encoder 10 and decoder 12 may support an intra prediction mode (which mode may also be called block-copy mode) according to which the currently encoded / decoded temporal block 140 is predicted based on the reconstructable sample values of previously encoded / decoded temporal blocks of the same coded channel to which the currently encoded / decoded temporal block 140 belongs, which is coded channel 92 in the example of Fig. 21. Additionally or alternatively, encoder 10 and decoder 12 may support an inter-prediction mode (which mode may also be called cross-channel prediction mode) according to which the currently encoded / decoded temporal block 140 is predicted based on the reconstructable sample values of previously encoded / decoded temporal blocks of one or more coded channels preceding - in coding order 32 - the coded channel 92 to which the currently encoded / decoded temporal block 140 belongs. Additionally or alternatively, there may be a mixed prediction mode according to which the prediction signal 64 is obtained by both, re- constructed / reconstructable sample values of previously encoded / decoded temporal blocks of coded channel 92 itself as well as reconstructed / reconstructable sample values of one or more coded channels preceding coded channel 92 in channel order along axis 32. Beyond this, there may be temporal blocks 140 which are coded without any prediction at encoder 10 and decoded without any prediction at decoder 12 such as the first temporal blocks 140 in the tiles 94 resulting from mutually separating the temporal blocks by means of the random access borders 96 on the one hand and the random access channel borders

[0359] FH241108PEP-2025376085fe 98 on the other hand. This corresponds to the prediction signal 64 being set to zero and this may form an additional mode which could be called bypass mode. Additionally, or alternatively, there may be other modes such as ones deriving a DC predictor or linear function predictor for block 64 based on immediately preceding samples which immediately precede block 140. The prediction parameters 90 may, thus, contain for a currently encoded / de- coded temporal block 140 a prediction mode flag or prediction mode indicator indicating the prediction mode to be used for this currently encoded / decoded temporal block 140 and, optionally, one or more parameters parameterizing the prediction mode to be used for this currently encoded / decoded temporal block 140. It might also be that the prediction parameters are themselves coded predictively from already reconstructed blocks 140. In this prediction process, the laid out random-access capabilities in channel- and temporal-direction are, as an example, always maintained, i.e. the mentioned prediction of prediction parameters may never be supported across such a random access segment.

[0360] As mentioned, the aforementioned coding dependencies ought not to cross any of the borders 96 and 98 not only result from the just-described sample prediction capabilities of block predictor 62 and 86, respectively, but may optionally also result from other mechanisms such as parameter prediction according to which parameters such as the aforementioned prediction parameters 90 for a certain temporal block 140 are predicted based on coding parameters conveyed in the data stream 16 for any previous temporal block, or context derivation for context-adaptive entropy coding / decoding any coding parameter such as the prediction parameters 90 or any other side information such as side information 76 and 36 for temporal block 140 based on any coding parameter conveyed in the data stream 16 for any preceding temporal block.

[0361] That is, summarizing, the encoder 10 encodes the multi-channel signal 14 by transferring it into the coded domain 28 and then coding the coded channels into data stream 16 in the just-described block-wise and predictive manner, wherein decoder 12 decodes the coded channels of coded domain 28 from data stream 16 and the corresponding block-wise and predictive manner with then gaining the multi-channel signal 14 in its original form 26 based on the coded channels in coded domain 28 by means of segment 38. As said, the channel transformation is optional and if not used, each sample 40 in the coded domain 28 really corresponds to one sample 18 in the original domain 26. If, further, the temporal mutual alignment is not used, each sample 40 exactly corresponds to a sample 18 in the original domain 26 at exactly the same time instant or, differently speaking, all temporally co-located

[0362] FH241108PEP-2025376085fe samples 40 in coded domain 28 remain mutually temporally co-located in the original domain 26.

[0363] It should be noted that the temporal blocks 30 might, other than illustrated in Fig. 21 , vary in block length rather than being of a constant length as depicted in Fig. 21. For instance, encoder 10 may decide on the length of blocks 30 and signal the block length of blocks 30 (and the corresponding temporal blocks 140 of the coded channels) within data stream 16. Such signaling might be done on block level, such as for each temporal block 30 or, differently speaking for each temporally aligned bundle of blocks 140, so that the encoder may decide on the block size on the fly, or the block length might be signaled in the stream 16 on a larger scope such as for a sequence of blocks or even the whole stream 16.

[0364] As to the residual coder and residual decoder 70 and 82, they may use transform coding / de- coding in order to convey the residual signal 76 in data stream 16. That is, the residual signal 80 may be conveyed in data stream 16 in transform or spectral domain by way of transform coefficients in residual signal 76. The transform domain might be a DCT, DST or an FFT. The transform may be non-overlapping, i.e. it may only transform residual signal 80 and its re-transform may only cover residual signal 76 within block 140, and / or may be non-windowed, i.e. the residual signal might be transformed without any transform window used to temporally shape the residual signal 80 before the transform. The transform domain, i.e. the transformation leading from time domain to transform domain which is used by the encoder to transform the prediction residual signal 80 to be coded und the corresponding re-transformation leading from transform domain to time domain which is used by the decoder to derive the prediction residual signal 80, or the transformation, might be selected from a set of available transforms including, for instance, one or more of 1) one or more DCTs, 2) one or more DSTs and 3) an identity transform according to which the prediction residual signal 80 is coded into the data stream 14 in time domain directly. The transform may be critically sampled in that the number of transform coefficients resulting from the samples of one block 140 may equal the number of samples of block 140. Again, the samples might be the residual samples or may be, in case of the bypass mode, the channel samples directly.

[0365] The transform coefficients might be encoded by quantization, i.e. they may be quantized with the quantized coefficients then being coded in the data stream 16. Dequantization may occur at decoding. For quantization, either a scalar uniform reconstruction quantizer or a

[0366] FH241108PEP-2025376085fe low complexity vector quantizer might be used. In order to determine the quantization indices, the encoder may perform some optimization algorithm such as a rate-distortion optimized scalar quantization, or a trellis quantization with the goal to approximately minimize an approximated Lagrangian rate-distortion cost. At the decoder, the reconstruction process that yiels the transform coefficients may be conducted by multiplying the coded quantization indices with a certain step-size and, in case of the use of a low-complexity vector quantizer, by additionally invoking a state-machine based on the parity of previously decoded quantization indices in order to reconstruct the current quantization index.

[0367] In order to control the quantization noise, the transform coefficients might be subject to noise shaping. Spectral noise shaping may be used to shape the quantization noise spectrally. This may be done by signaling in the data stream spectral-band scale factors, i.e. a scale factor per spectral band, which represent a transfer function of a spectral filter which approximates the spectral envelope of the signal within the current block 140 (or its prediction residual, respectively), or signaling filter coefficients defining a temporal filter having a filter transfer function which approximates the spectral envelope of the signal within the current block 140 (or its prediction residual, respectively). On encoder side, spectral noise shaping may be applied in spectral domain by multiplying an inverse of scale factors, either directly signaled in the data stream or derivable from the filter coefficients by filter-to-factor conversion, with the transform coefficients before quantization. That is, at encoder, the coefficients are shaped by the inverse of the spectral envelope. At decoder side, spectral shaping may be applied in spectral domain by multiplying scale factors, either directly signaled in the data stream or derived from the filter coefficients by filter-to-factor conversion, with the transform coefficients, with then. That is, at decoder, the coefficients are shaped by the spectral envelope before applying retransformation. Additionally or alternatively, temporal noise shaping might be applied. To this end, TNS filter coefficients might be determined and signaled by the encoder. The TNS filter coefficients may represent a transfer function which approximates the temporal envelope of the current block 140 (or its residual signal). The encoder may apply TNS filtering using the filter coefficients by spectrally filtering the possibly spectrally shaped transform coefficients so as to filter them with a transfer function corresponding to an inverse of the temporal envelope. The TNS filter coefficients might be derived by linear prediction analysis of the possibly spectrally shaped transform coefficients so as to derive a linear prediction filter, then used as TNS filter, which minimizes a prediction residual when spectrally applied on the possibly spectrally shaped transform coefficients. At the encoder, the TNS filtered coefficients are then quantized and entropy coded. At decoder side, the inverse takes place: the possibly spectrally shaped transform

[0368] FH241108PEP-2025376085fe coefficients are inversely TNS filtered before applying retransformation. Additionally or alternatively, noise filling might be used. The filling may be applied to zero-quantized portions of the spectrum and controlled by the encoder via corresponding noise filling parameters.

[0369] As to the encoding / decoding the block or sequence of quantized transform coefficients of a current block into / from the data stream 16, arithmetic coding, such as context-adaptive binary arithmetic coding, CABAC, may be used. The CABAC encoding / decoding may be performed frame wise. That is, in each channel, the sequence of blocks 140 may be partitioned into immediately consecutive blocks 140, which form frames. This partitioning may be equal among the channels so that, again, a frame denotes both a temporal portion within each channel individually, as well as a temporal portion of the multi-channel signal, i.e. a collection of temporally aligned frames. Within each frame, the sequence of blocks 140 are CABAC en / decoded with once initializing the contexts and resetting the internal CABAC state at the beginning and then updating the contexts’ probabilities during en / decoding the respective frame. That is, blocks 140 are CABAC decodable merely in units of frames. The context initialization might be done independent from previous frames, or depending on the contexts as manifesting itself at the end of, of during, the en / decoding a previous frame.

[0370] Some deblocking processing might be used to avoid blocking artifacts. If, alternatively, an overlapped transform is used, an overlap-add processing with re-transforms of immediately preceding / succeeding temporal blocks of the same coded channel might be used in order to completely reconstruct the current temporal block’s 140 residual signal 76.

[0371] Besides such transform-(residual)-coded blocks there might be temporal blocks 140 which, additionally or alternatively, are coded using, besides the block prediction by block predictor 62 / 86 - which could be called a primary prediction - a secondary sample-wise prediction of the residual samples in residual block 66 such as by predicting a current sample’s residual sample by means of already decoded values of preceding - in sample coding order - residual samples in block 66 or 80, with then correcting same by means of a secondary- prediction-residual sample decoded from the data stream 16. The secondary-prediction- residual samples for such a block may be coded into the data stream en block in a transform domain or sample-wise in time domain.

[0372] Note that the afore-mentioned spectral shaping of the residual signal of a block 140 might be seen as a sample wise residual prediction, i.e. the case where filter coefficients are sig-

[0373] FH241108PEP-2025376085fe naled for a block which define a temporal filter having a filter transfer function which approximates the spectral envelope of the residual signal within a current block 140. In sample wise residual prediction, the residual predictor on a current block 140 might either be chosen out of a fixed set of prediction modes, where an index to such a residual prediction mode is signaled in the bit-stream, or the residual prediction mode might be ‘signal adaptive’. In the latter case, prediction filter coefficients for the residual predictor are determined at the encoder by solving for example a linear equation, and are then quantized and transmitted to the decoder. At the decoder, the coefficients are inverse quantized and then the samplewise prediction is conducted with these coefficients. The number of used coefficients may vary per block and might also be signaled in the bit-stream. Additionally, it might optionally (i.e. indicated by some information in the bit-stream) be supported to invoke collocated samples from a previous block for the sample wise residual prediction. Finally, the coefficients of the sample wise residual prediction might be coded predictively, i.e. be predicted from used coefficients of a previous block, where only the differences to the current coefficients are transmitted.

[0374] A final note shall be made with respect to the juxtaposition of frames, blocks 140, channels and channel groups and regarding decoding order. The description above already described the fact that the channels might be grouped into channel group with each channel group being coded independently from each other, meaning that the blocks 140 in a certain channel group are coded without dependencies from channels outside their channel group. The decoding order 60, thus, would traverse the channels channel-group individually, channel group by channel group. Within each channel group, the blocks 140 are traversed as described: all temporally aligned blocks 140 of all channels fist, then proceeding with the next blocks 140 and so forth. A frame may have a sequence of blocks of a channel group encoded thereinto along the mentioned decoding order , such as n temporally consecutive blocks 140 for all channels of a channel group. IF the channel group had m channels, m*n block104 would, thus, be coded into the frame. As mentioned, there might be dependent frames, for which the CABAC contexts are adopted from the preceding frame of the same channel group, i.e. the one having encoded the immediately preceding block 140. For such dependent frames, not only CABAC contexts may be adopted from the preceding frame, but it may also be allowed to allow for prediction from the preceding frame to the dependent frame. Prediction, and possibly also any coding dependencies, towards channels outside the channel group and, within the channel group, towards frames temporally preceding the mostly recently previously en / decoded independent frame would be disallowed. Thus, each

[0375] FH241108PEP-2025376085fe tile shown in Fig. 21 by bold lines may represent a sequence of an independent frame flowed by zero, one or more dependent frames.

[0376] As mentioned before, Fig. 21 only represents a possible “framework” into which the previously described embodiments and the embodiments described subsequently may be built into. Many modifications may be performed with respect to Fig. 21 , and some of these modifications might be mentioned in the subsequent description with respect to certain ones of the subsequently described embodiments, but these modifications shall then be treated as being also applicable with respect to other ones of the subsequently described embodiments.

[0377] The description is now resumed with respect to the announced subsequently described implementation examples.

[0378] Implementation alternatives

[0379] Although some aspects have been described in the context of an apparatus, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or a feature of a method step. Analogously, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus. Some or all of the method steps may be executed by (or using) a hardware apparatus, like for example, a microprocessor, a programmable computer or an electronic circuit. In some embodiments, one or more of the most important method steps may be executed by such an apparatus.

[0380] Depending on certain implementation requirements, embodiments of the invention can be implemented in hardware or in software. The implementation can be performed using a digital storage medium, for example a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having electronically readable control signals stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed. Therefore, the digital storage medium may be computer readable.

[0381] Some embodiments according to the invention comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed.

[0382] FH241108PEP-2025376085fe Generally, embodiments of the present invention can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer. The program code may for example be stored on a machine-readable carrier.

[0383] Other embodiments comprise the computer program for performing one of the methods described herein, stored on a machine-readable carrier.

[0384] In other words, an embodiment of the inventive method is, therefore, a computer program having a program code for performing one of the methods described herein, when the computer program runs on a computer.

[0385] A further embodiment of the inventive methods is, therefore, a data carrier (or a digital storage medium, or a computer-readable medium) comprising, recorded thereon, the computer program for performing one of the methods described herein. The data carrier, the digital storage medium or the recorded medium are typically tangible and / or non-transitionary.

[0386] A further embodiment of the inventive method is, therefore, a data stream or a sequence of signals representing the computer program for performing one of the methods described herein. The data stream or the sequence of signals may for example be configured to be transferred via a data communication connection, for example via the Internet.

[0387] A further embodiment comprises a processing means, for example a computer, or a programmable logic device, configured to or adapted to perform one of the methods described herein.

[0388] A further embodiment comprises a computer having installed thereon the computer program for performing one of the methods described herein.

[0389] A further embodiment according to the invention comprises an apparatus or a system configured to transfer (for example, electronically or optically) a computer program for performing one of the methods described herein to a receiver. The receiver may, for example, be a computer, a mobile device, a memory device or the like. The apparatus or system may, for example, comprise a file server for transferring the computer program to the receiver.

[0390] FH241108PEP-2025376085fe In some embodiments, a programmable logic device (for example a field programmable gate array) may be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor in order to perform one of the methods described herein. Generally, the methods are preferably performed by any hardware apparatus.

[0391] The apparatus described herein may be implemented using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

[0392] The apparatus described herein, or any components of the apparatus described herein, may be implemented at least partially in hardware and / or in software.

[0393] The methods described herein may be performed using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

[0394] The methods described herein, or any components of the apparatus described herein, may be performed at least partially by hardware and / or by software.

[0395] The above-described embodiments are merely illustrative for the principles of the present invention. It is understood that modifications and variations of the arrangements and the details described herein will be apparent to others skilled in the art. It is the intent, therefore, to be limited only by the scope of the impending patent claims and not by the specific details presented by way of description and explanation of the embodiments herein.

[0396] FH241108PEP-2025376085fe

Claims

Claims1. Apparatus (12) for decoding a multi-channel waveform signal (14) from a data stream (16) using block-based prediction, the apparatus configured to decode from the data stream (16) a commonality syntax element (13) indicating for a plurality of channels (21a-f) of the multi-channel waveform signal (14), whether, among a set (29) of prediction modes supported by the apparatus, one prediction mode is commonly attributed to the plurality of channels (21 a-f), if the commonality syntax element (13) indicates that one prediction mode is commonly attributed to the plurality of channels (21 a-f), decode a set (31) of one or more prediction mode syntax elements from the data stream (16) which indicate a selected prediction mode (33) out of the set (29) of prediction modes, wherein the selected prediction mode (33) is the one prediction mode, or appoint a selected prediction mode (33) indicated by a set (31) of one or more prediction mode syntax elements decoded for a first channel (21a) among the plurality of channels (21a-f) the one prediction mode, or use a default prediction mode (35) among the set (29) of prediction modes as the one prediction mode, and decode each of the plurality of channels (21a-f) using the one prediction mode, and if the commonality syntax element (13) does not indicate that one prediction mode is commonly attributed to the plurality of channels (21 a-f), decode, from the data stream (16), for each of the plurality of channels (21 a-f), the set (31) of one or more prediction mode syntax elements, which indicate a selected prediction mode (39) out of the set (29) of prediction modes for the respective channel (21), and decode each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21).

2. Apparatus (12) of claim 1 , configured to derive, for each channel of the plurality of channels (21 a-f), a prediction residual (200) by, for each of one or more dependent channels (201) in the set of the plurality of channels (21 a-f),FH241108PEP-2025376085feusing inter-channel transform-domain residual prediction (204a; 204b) from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21a-f) to obtain a predicted transform-domain residual signal (208a; 208b), decoding a signaled transform-domain residual signal (210) from the data stream (16), and correcting (212) the predicted transform-domain residual signal (208a; 208b) using the signaled transform-domain residual signal (210), and correct (230), for each channel of the plurality of channels (21 a-f), a prediction signal (214) obtained by the prediction mode using which the respective dependent channel (201) is decoded using the prediction residual (200) decoded for the respective channel (21).

3. Apparatus (12) of claim 1 or 2, configured to derive, for each channel of the plurality of channels (21 a-f), a prediction residual (200) by for each of one or more dependent channels (201) in the set of the plurality of channels (21 a-f), decoding an inter-channel transform-domain residual prediction syntax element (41) from the data stream (16), if the inter-channel transform-domain residual prediction syntax element (41) is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), decoding a signaled transform-domain residual signal (210) from the data stream (16) and correcting (212) the predicted transform-domain residual signal (208a; 208b) using the signaled trans- form-domain residual signal (210), and if the inter-channel transform-domain residual prediction syntax element (41) is not indicative of the use of inter-channel transform-domain residual prediction,FH241108PEP-2025376085fedecoding a signaled transform-domain residual signal (210) from the data stream (16) into which the prediction residual (200) is coded without inter-channel transform-do- main residual prediction, and correct (230), for each channel of the plurality of channels (21 a-f), a prediction signal obtained by the prediction mode using which the respective channel (21) is decoded using the prediction residual (200) derived for the respective channel (21).

4. Apparatus (12) of any previous claim, configured to derive, for each channel of the plurality of channels (21 a-f), a prediction residual (200) by if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each of one or more dependent channels (201) in the set of the plurality of channels (21 a-f) , decoding an inter-channel transform-domain residual prediction syntax element (41) from the data stream (16), if the inter-channel transform-domain residual prediction syntax element (41) is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), decoding a signaled transform-domain residual signal (210) from the data stream (16) and correcting (212) the predicted transform-domain residual signal (208a; 208b) using the signaled transform-domain residual signal (210), and if the inter-channel transform-domain residual prediction syntax element (41) is not indicative of the use of inter-channel transform-domain residual prediction, decoding a signaled transform-domain residual signal (210) from the data stream (16) into which the prediction residual (200) is coded without inter-channel transform-domain residual prediction, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each channel of the plurality of channels (21 a-f),FH241108PEP-2025376085fedecoding a signaled transform-domain residual signal (210) from the data stream (16) into which the prediction residual (200) is coded without inter-channel transform-do- main residual prediction, and correct (230), for each channel of the plurality of channels (21 a-f), a prediction signal obtained by the prediction mode using which the respective channel (21) is decoded using the prediction residual (200) derived for the respective channel (21).

5. Apparatus (12) of any previous claim, configured to derive, for each channel of the plurality of channels (21 a-f), a prediction residual (200) by if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each of one or more dependent channels (201) in the set of the plurality of channels (21 a-f) , using inter-channel transform-domain residual prediction from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), decoding a signaled transform-domain residual signal (210) from the data stream (16) and correcting (212) the predicted transform-domain residual signal (208a; 208b) using the signaled trans- form-domain residual signal (210), and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each of the one or more dependent channels (201) in the set of the plurality of channels (21 a-f) , decoding an inter-channel transform-domain residual prediction syntax element (41) from the data stream (16), if the inter-channel transform-domain residual prediction syntax element (41) is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), decoding a signaled transform-domain residual signal (210) from the data stream (16) and correctingFH241108PEP-2025376085fe(212) the predicted transform-domain residual signal (208a; 208b) using the signaled trans- form-domain residual signal (210), and if the inter-channel transform-domain residual prediction syntax element (41) is not indicative of the use of inter-channel transform-domain residual prediction, decoding a signaled transform-domain residual signal (210) from the data stream (16) into which the prediction residual (200) is coded without inter-channel transform-do- main residual prediction, and correct (230), for each channel of the plurality of channels (21 a-f), a prediction signal obtained by the prediction mode using which the respective channel (21) is decoded using the prediction residual (200) derived for the respective channel (21).

6. Apparatus (12) of any of claim 3 to 5, configured to subject a corrected transform-domain residual signal (224) obtained by the correcting (212) the predicted transform-domain residual signal (208a, b) using the signaled trans- form-domain residual signal (210) to a reverse transformation (226) to obtain a non- trans- form-domain residual signal (228), and correct (230) the prediction signal (214) using the non-transform-domain residual signal (228).

7. Apparatus (12) of any of claims 2 to 6, configured to decode, for each channel of the plurality of channels (21 a-f), a transform-domain syntax element (43) from the data stream (16) which indicates a selected transform domain (55) out of a set (51) of transform domains, subjecting a corrected transform-domain residual signal (224) obtained by the correcting (212) the predicted transform-domain residual signal (208a; 208b) using the signaled transform-domain residual signal (210) to a reverse transformation (226) associated with the selected transform-domain for the respective channel (21) to obtain a non-trans- form-domain residual signal (228) and correct (230) the prediction signal using the non-transform-domain residual signal (228).

8. Apparatus (12) of claims 2 to 7, configured to decode, for each channel of the plurality of channels (21 a-f), a transform-domain syntax element (43) from the data stream (16) which indicates a selected transform domainFH241108PEP-2025376085fe(55) out of a set (51) of transform domains, the set (51) of transform domains including an identity transform, for each channel of the plurality of channels (21a-f) whose selected transform-do- main is not the identity transform, subject a corrected transform-domain residual signal (224) obtained by the correcting (212) the predicted transform-domain residual signal (208a; 208b) using the signaled transform-domain residual signal (210) to a reverse transformation (226) associated with the selected transform-domain for the respective channel (21) to obtain a non-transform- domain residual signal (228) and correct (230) the prediction signal using the non-transform-domain residual signal (228).

9. Apparatus (12) of any of claim 2 to 8, wherein the one or more dependent channels (201) encompass all channels of the plurality of channels (21a-f) except one intra-channel- coded channel.

10. Apparatus (12) of any of claims 2 to 9, wherein for each of the one or more dependent channels (201), the one or more reference channels (202) is determined by default, or by implicit or explicit signaling in the data stream (16).

11. Apparatus (12) of any previous claim, wherein the plurality of channels (21a-f) is one of a plurality of channel groups (240) of channels of the multi-channel waveform signal (14), and the apparatus is configured to decode the multi-channel waveform signal (14) from the data stream (16) channel group wise with decoding the commonality syntax element (13) for each channel group (240).

12. Apparatus (12) of any previous claim, wherein each channel of the plurality of channels (21a-f) is partitioned into a sequence of blocks (140c) so that the blocks (140c) of the channels (c) are mutually aligned to each other, and the apparatus is configured to perform the decoding the commonality syntax element (13), the, if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), decoding the set (31) of one or more prediction mode syntax elements or appointing or using and decoding each of the plurality of channels (21 a-f) using the one prediction mode (25), and the, if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), decoding the set (31) of one or more prediction mode syntax elements for each of the plurality ofFH241108PEP-2025376085fechannels (21 a-f), and decoding each of the plurality of channels (21a-f) using the prediction mode decoded for the respective channel (21) block-wise for a set (250) of mutually aligned blocks (140) of the plurality of channels (21a-f) comprising one block (140) of each channel of the plurality of channels (21 a-f) which is aligned to the one block (140) of each other channel of the plurality of channels (21 a-f).

13. Apparatus (12) of any previous claim, configured to, for each of one or more parametrized prediction modes of the set (29) of prediction modes, perform a decoding of a current channel (21) of the plurality of channels (21 a-f) using the respective parametrized prediction mode by deriving one or more prediction parameters for the current channel (21) and decoding the current channel (21) using the respective parametrized prediction mode parametrized according to the one or more prediction parameters.

14. Apparatus (12) of claim 13, configured to if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), if the one prediction mode (25) is one of the one or more parametrized prediction modes, decode one or more prediction parameters from the data stream (16), and decode each of the plurality of channels (21 a-f) using the one prediction mode (25) parametrized according to the one or more prediction parameters, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), decode, from the data stream (16), for each of the plurality of channels (21 a-f) for which the selected prediction mode (39) is one of the one or more parametrized prediction modes, one or more prediction parameters from the data stream (16), and decode the respective channel (21) parametrized according to the one or more prediction parameters decoded for the respective channel (21).

15. Apparatus (12) of claim 13, configured to irrespective of whether the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f),FH241108PEP-2025376085fedecode, from the data stream (16), for each of the plurality of channels (21a-f) decoded using a prediction mode being one of the one or more parametrized prediction modes, one or more prediction parameters from the data stream (16), and decode the respective channel (21) parametrized according to the one or more prediction parameters decoded for the respective channel (21).

16. Apparatus (12) of any previous claim, configured to if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f) , for each of the plurality of channels (21 a-f), decode one or more prediction parameters from the data stream (16), and decode the respective channels (21) using the one prediction mode (25) parametrized according to the one or more prediction parameters, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), decode, from the data stream (16), for each of the plurality of channels (21 a-f) for which the selected prediction mode (39) is one of one or more parametrized prediction modes, one or more prediction parameters from the data stream (16), and decode the respective channel (21) parametrized according to the one or more prediction parameters decoded for the respective channel (21).

17. Apparatus (12) of any previous claim, configured to in decoding each of the plurality of channels (21 a-f) using the one prediction mode (25) or the decoding each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21), use transform-based prediction residual decoding in if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), one transform domain (53) out of a set (51) of transform domain which is commonly selected among the plurality of channels (21 a-f), and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f),FH241108PEP-2025376085fefor each of the plurality of channels (21 a-f), a selected transform domain (55) which is channel-individually selected out of the set (51) of transform domains.

18. Apparatus (12) of any previous claim, configured to decode from the data stream (16) a further commonality syntax element (13) indicating for the plurality of channels (21a-f) of the multi-channel waveform signal (14), whether, among a set (51) of transform domains supported by the apparatus, one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), in decoding each of the plurality of channels (21a-f) using the one prediction mode (25) or the decoding each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21), use transform-based prediction residual decoding in if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), the one transform domain (53), and if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), for each of the plurality of channels (21 a-f), a selected transform domain (55) which is channel-individually selected out of the set (51) of transform domains.

19. Apparatus (12) of any previous claim, configured to if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), decode from the data stream (16) a further commonality syntax (45) element indicating for the plurality of channels (21 a-f) of the multi-channel waveform signal (14), whether, among a set (51) of transform domains supported by the apparatus, one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), in decoding each of the plurality of channels using the one prediction mode (25), use transform-based prediction residual decoding in if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), the one transform domain (53), and if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f),FH241108PEP-2025376085fefor each of the plurality of channels (21 a-f), a selected transform domain (55) which is channel-individually selected out of the set (51) of transform domains, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), in decoding each of the plurality of channels (21 a-f) using the decoding each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21), use transform-based prediction residual decoding in for each of the plurality of channels (21 a-f), a selected transform domain (55) which is channel-individually selected out of the set (51) of transform domains.

20. Apparatus (12) of any of claims 17 to 19, configured to if it is indicated that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), select the one transform domain (53) out of the set (51) of transform domain by default or by implicitly or explicit signaling, and if it is not indicated that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), select, for each of the plurality of channels (21 a-f), the selected transform domain (55) by default or by implicitly or explicit signaling contained in the data stream (16) for the respective channel (21).21 . Apparatus (12) of any previous claim, wherein the set (29) of prediction modes comprises one or more of one or more intra-channel prediction modes, and one or more inter-channel prediction modes.

22. Apparatus (12) of any previous claim, wherein the set (29) of prediction modes comprises one or more of an intra-channel DC prediction mode, an intra-channel line-fitting prediction mode, an intra-channel block matching prediction mode, a no-prediction mode, and one or more inter-channel prediction modes.FH241108PEP-2025376085fe23. Apparatus (12) of any previous claim, configured to decode the set (31) of one or more prediction mode syntax elements for a first channel (21a) among the plurality of channels (21a-f) prior to the commonality syntax element (13) and if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), the set (31) of one or more prediction mode syntax elements decoded for a first channel (21a) indicates the one prediction mode (25), and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), sequentially decode the set (31) of one or more prediction mode syntax elements for subsequent channels among the plurality of channels (21a-f).

24. Apparatus (12) of any previous claim, configured to decode the commonality syntax element (13) under a condition that the set (31) of one or more prediction mode syntax elements decoded for the first channel (21a) indicate a selected prediction mode (33) falling into a predetermined subset of one or more prediction modes.

25. Apparatus (12) for decoding a multi-channel waveform signal (14) from a data stream (16) using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual decoding, the apparatus configured to decode from the data stream (16) a further commonality syntax element (45) indicating for a plurality of channels (21 a-f) of the multi-channel waveform signal (14), whether, among a set (51) of transform domains supported by the apparatus, one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), decode each of the plurality of channels (21 a-f) using the one transform domain (53) for the transform-based prediction residual decoding, and if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f),FH241108PEP-2025376085fedecode each of the plurality of channels (21a-f) using a selected transform domain (55), which is channel-individually selected out of the set (51) of transform domains, for the transform-based prediction residual decoding.

26. Apparatus (12) of claim 25, configured to if it is indicated that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), select the one transform domain (53) out of the set (51) of transform domain by default or by implicitly or explicit signaling, and if it is not indicated that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), select, for each of the plurality of channels (21 a-f), the selected transform domain (55) by default or by implicitly or explicit signaling contained in the data stream (16) for the respective channel (21).

27. Apparatus (12) of any of claims 25 and 26, wherein the plurality of channels (21 a-f) is one of a plurality of channel groups (240) of channels of the multi-channel waveform signal (14), and the apparatus is configured to decode the multi-channel waveform signal (14) from the data stream (16) channel group wise with decoding the further commonality syntax element (45) for each channel group (240).

28. Apparatus (12) of any of claims 25 to 27, wherein each channel of the plurality of channels (21a-f) is partitioned into a sequence of blocks (140) so that the blocks (140) of the channels are mutually aligned to each other, and the apparatus is configured to perform the decoding the further commonality syntax element (45), the, if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), decoding each of the plurality of channels (21a-f) using the one transform domain (53), and the, if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), decoding each of the plurality of channels (21a-f) using a selected transform domain (55) block-wise for a set (250) of mutually aligned blocks (140) of the plurality of channels (21a-f) comprising one block (140) of each channel of the plurality of channels (21a-f) which is aligned to the one block (140) of each other channel of the plurality of channels (21 a-f).FH241108PEP-2025376085fe29. Apparatus (12) of any of claims 25 to 28, wherein the set (51) of transform domains comprises a DCT domain or a DST domain and comprises an identity transform domain.

30. Apparatus (12) for decoding a waveform signal from a data stream (16), the apparatus configured to perform sample-to-sample prediction (260) for a block (140CUrrent) of the waveform signal, to obtain a preliminary time-domain block predictor (214); spectrally filter (300) the preliminary time-domain predictor to obtain a filtered timedomain block predictor (302); perform transform-domain-to-transform-domain prediction (204a, b) for the block (140CUrrent) of the waveform signal to obtain a transform-domain predictor (208a, b); decode a residual spectrum (210) from the data stream (16), correct (212) the transform-domain predictor (208a, b) using the residual spectrum (210) to obtain a corrected residual spectrum (224), subject the corrected residual spectrum (224) to a re-transformation (226) to obtain a time-domain residual signal (224); correct (230) the filtered time-domain block predictor (302) using the time-domain residual signal, wherein the apparatus is configured to perform the spectrally filtering (300) the preliminary time-domain predictor (214) using a transfer function being higher in a first spectral region (61a) than compared to a second spectral region (61 b), and perform the transform-domain-to-transform-domain prediction (204a, b) spectrally restricted to the second spectral region (61b), or by obtaining a preliminary transform-domain predictor and spectrally filtering (300) the preliminary transform-domain predictor using a transfer function being higher in the second spectral region (61b) than compared to the first spectral region (61a) to obtain the transform-domain predictor; orFH241108PEP-2025376085feby performing filter synthesis using an impulse response which is higher in the second spectral region (61 b) than compared to the first spectral region (61a).

31. Apparatus (12) according to claim 30, wherein the waveform signal is a multi-channel waveform signal (14), the block is a block (140) of a channel of channels of the multichannel signal, and the transform-domain-to-transform-domain prediction (204a, b) is an inter-channel transform-domain-to-transform-domain prediction (204a, b) from one or more reference channels (202).

32. Apparatus (12) according to claim 30 or 31 , configured to select, among a set (29) of prediction modes, a selected prediction mode (33) for the block (140), and perform the sample-to-sample prediction (260) for the block (140) using the selected prediction mode (33).

33. Apparatus (12) according to any of claims 30 to 32, configured to perform the transform-domain-to-transform-domain prediction (204a, b) by spectrally applying a convolutional synthesis filter with a filter kernel (216) which extends into one or more reference channels (202) within the second spectral region (61b) and setting the transform-domain predictor to zero in the first spectral region (61a).

34. Apparatus (12) according to any of claims 30 to 33, configured to perform the transform-domain-to-transform-domain prediction (204a, b) by spectrally copying from a corrected residual spectrum of a reference channel (202) within the second spectral region (61b) and setting the transform-domain predictor to zero in the first spectral region (61a), or spectrally copying from a corrected residual spectrum of the reference channel (202) to obtain a preliminary transform-domain predictor and spectrally shaping the preliminary transform-domain predictor using a transfer function according to the prediction gain of the transform-domain-to-transform-domain prediction (204a, b).

35. Apparatus (10) for encoding a multi-channel waveform signal (14) into a data stream (16) using block-based prediction, the apparatus configured toFH241108PEP-2025376085feencode into the data stream (16) a commonality syntax element (13) indicating for a plurality of channels (21a-f) of the multi-channel waveform signal (14), whether, among a set (29) of prediction modes supported by the apparatus, one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encode a set (31) of one or more prediction mode syntax elements into the data stream (16) which indicate a selected prediction mode (33) out of the set (29) of prediction modes, wherein the selected prediction mode (33) is the one prediction mode (25), or a set (31) of one or more prediction mode syntax elements encoded for a first channel (21a) among the plurality of channels (21 a-f) is to be appointed the one prediction mode (25), or a default prediction mode (35) among the set (29) of prediction modes is to be used as the one prediction mode (25), and encode each of the plurality of channels using the one prediction mode (25), and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encode, into the data stream (16), for each of the plurality of channels (21 a-f), the set (31) of one or more prediction mode syntax elements, which indicate a selected prediction mode (39) out of the set (29) of prediction modes for the respective channel (21), and encode each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21).

36. Apparatus (10) of claim 35, configured to encode, for each channel of the plurality of channels (21a-f), a prediction residual (200) by, for each of one or more dependent channels (201) in the set of the plurality of channels (21 a-f), using inter-channel transform-domain residual prediction (204a; 204b) from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), and encoding a signaled transform-domain residual signal (210) into the data stream (16) using which the predicted transform-domain residual signal (208a; 208b) is correctable, andFH241108PEP-2025376085feso that, for each channel of the plurality of channels (21 a-f), a prediction signal (214) obtained by the prediction mode using which the respective dependent channel (201) is encoded is correctable using the prediction residual (200) encoded for the respective channel (21).

37. Apparatus (10) of claim 35 or 36, configured to encode, for each channel of the plurality of channels (21 a-f), a prediction residual (200) by for each of one or more dependent channels (201) in the set of the plurality of channels (21 a-f), encoding an inter-channel transform-domain residual prediction syntax element (41) into the data stream (16), if the inter-channel transform-domain residual prediction syntax element (41) is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), and encoding a signaled transform-domain residual signal (210) into the data stream (16) using which the predicted transform-domain residual signal (208a; 208b) is correctable, and if the inter-channel transform-domain residual prediction syntax element (41) is not indicative of the use of inter-channel transform-domain residual prediction, encoding a signaled transform-domain residual signal (210) into the data stream (16) into which the prediction residual (200) is coded without inter-channel transform-domain residual prediction, and so that, for each channel of the plurality of channels (21a-f), a prediction signal obtained by the prediction mode using which the respective channel (21) is encoded is correctable using the prediction residual (200) encoded for the respective channel (21).

38. Apparatus (10) of any of claims 35 to 37, configured to encode, for each channel of the plurality of channels (21 a-f), a prediction residual (200) byFH241108PEP-2025376085feif the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each of one or more dependent channels (201) in the set of the plurality of channels (21 a-f), encoding an inter-channel transform-domain residual prediction syntax element (41) into the data stream (16), if the inter-channel transform-domain residual prediction syntax element (41) is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), and encoding a signaled transform-domain residual signal (210) into the data stream (16) using which the predicted trans- form-domain residual signal (208a; 208b) is correctable, and if the inter-channel transform-domain residual prediction syntax element (41) is not indicative of the use of inter-channel transform-domain residual prediction, encoding a signaled transform-domain residual signal (210) into the data stream (16) into which the prediction residual (200) is coded without inter-channel transform-domain residual prediction, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each channel of the plurality of channels (21 a-f), encoding a signaled transform-domain residual signal (210) into the data stream (16) into which the prediction residual (200) is coded without inter-channel transform-do- main residual prediction, and so that, for each channel of the plurality of channels (21a-f), a prediction signal obtained by the prediction mode using which the respective channel (21) is encoded is correctable using the prediction residual (200) encoded for the respective channel (21).

39. Apparatus (10) of any of claims 35 to 38, configured toFH241108PEP-2025376085feencode, for each channel of the plurality of channels (21 a-f), a prediction residual (200) by if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each of one or more dependent channels (201) in the set of the plurality of channels (21 a-f), using inter-channel transform-domain residual prediction from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), and encoding a signaled transform-domain residual signal (210) into the data stream (16) using which the predicted transform-domain residual signal (208a; 208b) is correctable, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each of the one or more dependent channels (201) in the set of the plurality of channels (21 a-f), encoding an inter-channel transform-domain residual prediction syntax element (41) into the data stream (16), if the inter-channel transform-domain residual prediction syntax element (41) is indicative of a use of inter-channel transform-domain residual prediction, using the inter-channel transform-domain residual prediction from the prediction residual (206a; 206b) of one or more reference channels (202) within the plurality of channels (21 a-f) to obtain a predicted transform-domain residual signal (208a; 208b), and encoding a signaled transform-domain residual signal (210) into the data stream (16) using which the predicted trans- form-domain residual signal (208a; 208b) is correctable, and if the inter-channel transform-domain residual prediction syntax element (41) is not indicative of the use of inter-channel transform-domain residual prediction, encoding a signaled transform-domain residual signal (210) into the data stream (16) into which the prediction residual (200) is coded without inter-channel transform-domain residual prediction, andFH241108PEP-2025376085feso that, for each channel of the plurality of channels (21 a-f), a prediction signal obtained by the prediction mode using which the respective channel (21) is encoded is correctable using the prediction residual (200) encoded for the respective channel (21).

40. Apparatus (10) of any of claims 36 to 39, wherein for correcting the prediction signal (214) a corrected transform-domain residual signal (224) obtained by the correcting (212) the predicted transform-domain residual signal (208a, b) using the signaled transform-do- main residual signal (210) is to be subject to a reverse transformation (226) to obtain a non- transform-domain residual signal (228), and the prediction signal (214) is to be corrected using the non-transform-domain residual signal (228).41 . Apparatus (10) of any of claims 36 to 40, configured to encode, for each channel of the plurality of channels (21 a-f), a transform-domain syntax element (43) into the data stream (16) which indicates a selected transform domain (55) out of a set (51) of transform domains, so that for correcting (230) the prediction signal (214) a corrected transform-domain residual signal (224) obtained by the correcting (212) the predicted transform-domain residual signal (208a; 208b) using the signaled transform-domain residual signal (210) is to be subject to a reverse transformation (226) associated with the selected transform-domain for the respective channel (21) to obtain a non-transform-domain residual signal (228) and the prediction signal is to be corrected using the non-transform-domain residual signal (228).

42. Apparatus (10) of any of claims 36 to 41 , configured to encode, for each channel of the plurality of channels (21 a-f), a transform-domain syntax element (43) into the data stream (16) which indicates a selected transform domain (55) out of a set (51) of transform domains, the set (51) of transform domains including an identity transform, for each channel of the plurality of channels (21 a-f) whose selected transform-do- main is not the identity transform, for correcting (230) the prediction signal (214) a corrected transform-domain residual signal (224) obtained by the correcting the predicted transform-domain residual signal (208a; 208b) using the signaledFH241108PEP-2025376085fetransform-domain residual signal (210) is to be subject to a reverse transformation (226) associated with the selected transform-domain for the respective channel (21) to obtain a non-transform-domain residual signal (228) and the prediction signal is to be corrected using the non-transform-domain residual signal (228).

43. Apparatus (10) of any of claims 36 to 42, wherein the one or more dependent channels (201) encompass all channels of the plurality of channels (21a-f) except one intra- channel-coded channel.

44. Apparatus (10) of any of claims 36 to 43, wherein for each of the one or more dependent channels (201), the one or more reference channels (202) is determined by default, or by implicit or explicit signaling in the data stream (16).

45. Apparatus (10) of any of claims 35 to 44, wherein the plurality of channels (21a-f) is one of a plurality of channel groups (240) of channels of the multi-channel waveform signal (14), and the apparatus is configured to encode the multi-channel waveform signal (14) into the data stream (16) channel group wise with encoding the commonality syntax element (13) for each channel group (240).

46. Apparatus (10) of any of claims 35 to 45, wherein each channel of the plurality of channels (21a-f) is partitioned into a sequence of blocks (140c) so that the blocks (140c) of the channels (c) are mutually aligned to each other, and the apparatus is configured to perform the encoding the commonality syntax element (13), the, if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encoding the set (31) of one or more prediction mode syntax elements or encoding or using and encoding each of the plurality of channels (21 a-f) using the one prediction mode (25), and the, if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encoding the set (31) of one or more prediction mode syntax elements for each of the plurality of channels (21 a-f), and encoding each of the plurality of channels (21a-f) using the prediction mode encoded for the respective channel (21) block-wise for a set (250) of mutually aligned blocks (140) of the plurality of channels (21a-f) comprising one block (140) of each channel of the plurality of channels (21 a-f) which is aligned to the one block (140) of each other channel of the plurality of channels (21 a-f).FH241108PEP-2025376085fe47. Apparatus (10) of any of claims 35 to 46, configured to, for each of one or more parametrized prediction modes of the set (29) of prediction modes, perform an encoding of a current channel of the plurality of channels (21a-f) using the respective parametrized prediction mode by deriving one or more prediction parameters for the current channel and encoding the current channel using the respective parametrized prediction mode parametrized according to the one or more prediction parameters.

48. Apparatus (10) of claim 47, configured to if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f) , if the one prediction mode (25) is one of the one or more parametrized prediction modes, encode one or more prediction parameters into the data stream (16), and encode each of the plurality of channels (21 a-f) using the one prediction mode (25) parametrized according to the one or more prediction parameters, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encode, into the data stream (16), for each of the plurality of channels (21 a-f) for which the selected prediction mode (39) is one of the one or more parametrized prediction modes, one or more prediction parameters from the data stream (16), and encode the respective channel (21) parametrized according to the one or more prediction parameters encoded for the respective channel (21).

49. Apparatus (10) of claim 47, configured to irrespective of whether the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encode, into the data stream (16), for each of the plurality of channels (21a-f) encoded using a prediction mode being one of the one or more parametrized prediction modes, one or more prediction parameters from the data stream (16), and encode the respective channel (21) parametrized according to the one or more prediction parameters encoded for the respective channel (21).

50. Apparatus (10) of any of claims 35 to 49, configured toFH241108PEP-2025376085feif the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each of the plurality of channels (21 a-f), encode one or more prediction parameters into the data stream (16), and encode the respective channels (21) using the one prediction mode (25) parametrized according to the one or more prediction parameters, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encode, into the data stream (16), for each of the plurality of channels (21 a-f) for which the selected prediction mode (39) is one of one or more parametrized prediction modes, one or more prediction parameters from the data stream (16), and encode the respective channel (21) parametrized according to the one or more prediction parameters encoded for the respective channel (21).51 . Apparatus (10) of any of claims 35 to 50, configured to in encoding each of the plurality of channels (21 a-f) using the one prediction mode (25) or the decoding each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21), use transform-based prediction residual encoding in if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), one transform domain (53) out of a set (51) of transform domain which is commonly selected among the plurality of channels (21 a-f), and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), for each of the plurality of channels (21 a-f), a selected transform domain (55) which is channel-individually selected out of the set (51) of transform domains.

52. Apparatus (10) of any of claims 35 to 51 , configured to encode into the data stream (16) a further commonality syntax element (45) indicating for the plurality of channels (21a-f) of the multi-channel waveform signal (14), whether,FH241108PEP-2025376085feamong a set (51) of transform domains supported by the apparatus, one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), in encoding each of the plurality of channels (21a-f) using the one prediction mode (25) or the encoding each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21), use transform-based prediction residual encoding in if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), the one transform domain (53), and if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), for each of the plurality of channels (21 a-f), a selected transform domain (55) which is channel-individually selected out of the set (51) of transform domains.

53. Apparatus (10) of any of claims 35 to 52, configured to if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encode into the data stream (16) a further commonality syntax element (45) indicating for the plurality of channels (21a-f) of the multi-channel waveform signal (14), whether, among a set (51) of transform domains supported by the apparatus, one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), in encoding each of the plurality of channels (21 a-f) using the one prediction mode (25), use transform-based prediction residual encoding in if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), the one transform domain (53), and if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), for each of the plurality of channels (21 a-f), a selected transform domain (55) which is channel-individually selected out of the set (51) of transform domains, and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f),FH241108PEP-2025376085fein encoding each of the plurality of channels (21a-f) using the decoding each of the plurality of channels (21a-f) using the selected prediction mode (39) for the respective channel (21), use transform-based prediction residual encoding in for each of the plurality of channels (21 a-f), a selected transform domain (55) which is channel-individually selected out of the set (51) of transform domains.

54. Apparatus (10) of any of claims 51 to 53, configured to if it is indicated that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), select the one transform domain (53) out of the set (51) of transform domain by default or by implicitly or explicit signaling, and if it is not indicated that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), select, for each of the plurality of channels (21 a-f), the selected transform domain (55) by default or by implicitly or explicit signaling contained in the data stream (16) for the respective channel (21).

55. Apparatus (10) of any of claims 35 to 54, wherein the set (29) of prediction modes comprises one or more of one or more intra-channel prediction modes, and one or more inter-channel prediction modes.

56. Apparatus (10) of any of claims 35 to 55, wherein the set (29) of prediction modes comprises one or more of an intra-channel DC prediction mode, an intra-channel line-fitting prediction mode, an intra-channel block matching prediction mode, a no-prediction mode, and one or more inter-channel prediction modes.

57. Apparatus (10) of any of claims 35 to 56, configured to encode the set (31) of one or more prediction mode syntax elements for a first channel (21a) among the plurality of channels (21 a-f) prior to the commonality syntax elementFH241108PEP-2025376085fe(13) and if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), the set (31) of one or more prediction mode syntax elements encoded for a first channel (21a) indicates the one prediction mode (25), and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), sequentially encode the set (31) of one or more prediction mode syntax elements for subsequent channels among the plurality of channels (21a-f).

58. Apparatus (10) of any of claims 35 to 57, configured to encode the commonality syntax element (13) under a condition that the set (31) of one or more prediction mode syntax elements encoded for the first channel (21a) indicate a selected prediction mode (33) falling into a predetermined subset of one or more prediction modes.

59. Apparatus (10) for encoding a multi-channel waveform signal (14) into a data stream (16) using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual encoding, the apparatus configured to encode into the data stream (16) a further commonality syntax element (45) indicating for a plurality of channels (21a-f) of the multi-channel waveform signal (14), whether, among a set (51) of transform domains supported by the apparatus, one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), encode each of the plurality of channels (21 a-f) using the one transform domain (53) for the transform-based prediction residual encoding, and if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), encode each of the plurality of channels (21a-f) using a selected transform domain (55), which is channel-individually selected out of the set (51) of transform domains, for the transform-based prediction residual encoding.

60. Apparatus (10) of claim 59, configured toFH241108PEP-2025376085feif it is indicated that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), select the one transform domain (53) out of the set (51) of transform domain by default or by implicitly or explicit signaling, and if it is not indicated that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), select, for each of the plurality of channels (21 a-f), the selected transform domain (55) by default or by implicitly or explicit signaling contained in the data stream (16) for the respective channel (21).

61. Apparatus (10) of claim 59 or 60, wherein the plurality of channels (21 a-f) is one of a plurality of channel groups (240) of channels of the multi-channel waveform signal (14), and the apparatus is configured to encode the multi-channel waveform signal (14) into the data stream (16) channel group wise with encoding the further commonality syntax element (45) for each channel group (240).

62. Apparatus (10) of any of claims 59 to 61 , wherein each channel of the plurality of channels (21a-f) is partitioned into a sequence of blocks (140) so that the blocks (140) of the channels are mutually aligned to each other, and the apparatus is configured to perform the encoding the further commonality syntax element (45), the, if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), encoding each of the plurality of channels (21a-f) using the one transform domain (53), and the, if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), encoding each of the plurality of channels (21a-f) using a selected transform domain (55) block-wise for a set (250) of mutually aligned blocks (140) of the plurality of channels (21a-f) comprising one block (140) of each channel of the plurality of channels (21a-f) which is aligned to the one block (140) of each other channel of the plurality of channels (21 a-f).

63. Apparatus (10) of any of claims 59 to 62, wherein the set (51) of transform domains comprises a DCT domain or a DST domain and comprises an identity transform domain.

64. Apparatus (10) for encoding a waveform signal into a data stream (16), the apparatus configured toFH241108PEP-2025376085feperform sample-to-sample prediction (260) for a block (140CUrrent) of the waveform signal, to obtain a preliminary time-domain block predictor (214); spectrally filter (300) the preliminary time-domain predictor to obtain a filtered timedomain block predictor (302); perform transform-domain-to-transform-domain prediction (204a, b) for the block (140CUrrent) of the waveform signal to obtain a transform-domain predictor (208a, b); encode a residual spectrum (210) into the data stream (16), using which the trans- form-domain predictor (208a, b) is correctable to obtain a corrected residual spectrum (224), which, when being subject to a re-transformation (226), yields a time-domain residual signal (224) for correcting (230) the time-domain block predictor (302), wherein the apparatus (10) is configured to perform the spectrally filtering (300) the preliminary time-domain predictor (214) using a transfer function being higher in a first spectral region (61a) than compared to a second spectral region (61 b), and perform the transform-domain-to-transform-domain prediction (204a, b) spectrally restricted to the second spectral region (61b), or by obtaining a preliminary transform-domain predictor and spectrally filtering (300) the preliminary transform-domain predictor using a transfer function being higher in the second spectral region (61b) than compared to the first spectral region (61a) to obtain the transform-domain predictor; or by performing filter synthesis using an impulse response which is higher in the second spectral region (61b) than compared to the first spectral region (61a).

65. Apparatus (10) according to claim 64, wherein the waveform signal is a multi-channel waveform signal (14), the block is a block (140) of a channel of channels of the multichannel signal, and the transform-domain-to-transform-domain prediction (204a, b) is an inter-channel transform-domain-to-transform-domain prediction (204a, b) from one or more reference channels (202).

66. Apparatus (10) according to any claim 64 or 65, configured toFH241108PEP-2025376085feselect, among a set (29) of prediction modes, a selected prediction mode (33) for the block (140), and perform the sample-to-sample prediction (260) for the block (140) using the selected prediction mode (33).

67. Apparatus (10) according to any of claims 64 to 66, configured to perform the transform-domain-to-transform-domain prediction (204a, b) by spectrally applying a convolutional synthesis filter with a filter kernel (216) which extends into one or more reference channels (202) within the second spectral region (61b) and setting the transform-domain predictor to zero in the first spectral region (61a).

68. Apparatus (10) according to any of claims 64 to 67, configured to perform the transform-domain-to-transform-domain prediction (204a, b) by spectrally copying from a corrected residual spectrum of a reference channel (202) within the second spectral region (61b) and setting the transform-domain predictor to zero in the first spectral region (61a), or spectrally copying from a corrected residual spectrum of the reference channel (202) to obtain a preliminary transform-domain predictor and spectrally shaping the preliminary transform-domain predictor using a transfer function according to the prediction gain of the transform-domain-to-transform-domain prediction (204a, b).

69. Method (400) for decoding a multi-channel waveform signal (14) from a data stream (16) using block-based prediction, the method (400) comprising: decoding (402) from the data stream (16) a commonality syntax element (13) indicating for a plurality of channels (21a-f) of the multi-channel waveform signal (14), whether, among a set (29) of prediction modes supported by the method, one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), decoding (404) a set (31) of one or more prediction mode syntax elements from the data stream (16) which indicate a selected prediction mode (33) out of the set (29) of prediction modes, wherein the selected prediction mode (33) is the one prediction mode (25), or appointing a selected prediction mode (33) indicated by a set (31) of one or moreFH241108PEP-2025376085feprediction mode syntax elements decoded for a first channel (21a) among the plurality of channels (21a-f) the one prediction mode (25), or using a default prediction mode (35) among the set (29) of prediction modes as the one prediction mode (25), and decoding each of the plurality of channels (21a-f) using the one prediction mode (25), and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), decoding (406), from the data stream (16), for each of the plurality of channels (21a- f), the set (31) of one or more prediction mode syntax elements, which indicate a selected prediction mode (39) out of the set (29) of prediction modes for the respective channel (21), and decoding each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21).

70. Method (420) for decoding a multi-channel waveform signal (14) from a data stream (16) using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual decoding, the method (420) comprising: decoding (222) from the data stream (16) a further commonality syntax element (45) indicating for a plurality of channels (21 a-f) of the multi-channel waveform signal (14), whether, among a set (51) of transform domains supported by the method (420), one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), decoding (424) each of the plurality of channels (21 a-f) using the one transform domain (53) for the transform-based prediction residual decoding, and if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), decoding (426) each of the plurality of channels (21 a-f) using a selected transform domain (55), which is channel-individually selected out of the set (51) of transform domains, for the transform-based prediction residual decoding.FH241108PEP-2025376085fe71. Method (440) for decoding a waveform signal from a data stream (16), the method (440) comprising: performing (441) sample-to-sample prediction (260) for a block (140CUrrent) of the waveform signal, to obtain a preliminary time-domain block predictor (214); spectrally filtering (300) the preliminary time-domain predictor to obtain a filtered time-domain block predictor (302); performing (442) transform-domain-to-transform-domain prediction (204a, b) for the block (140CUrrent) of the waveform signal to obtain a transform-domain predictor (208a, b); decoding (443) a residual spectrum (210) from the data stream (16), correcting (212) the transform-domain predictor (208a, b) using the residual spectrum (210) to obtain a corrected residual spectrum (224), subjecting (444) the corrected residual spectrum (224) to a re-transformation (226) to obtain a time-domain residual signal (224); correcting (230) the filtered time-domain block predictor (302) using the time-domain residual signal, wherein the method (440) further comprises performing (445) the spectrally filtering (300) the preliminary time-domain predictor (214) using a transfer function being higher in a first spectral region (61a) than compared to a second spectral region (61 b), and performing (446) the transform-domain-to-transform-domain prediction (204a, b) spectrally restricted to the second spectral region (61b), or by obtaining a preliminary transform-domain predictor and spectrally filtering (300) the preliminary transform -domain predictor using a transfer function being higher in the second spectral region (61b) than compared to the first spectral region (61a) to obtain the transform-domain predictor; or by performing filter synthesis using an impulse response which is higher in the second spectral region (61b) than compared to the first spectral region (61a).FH241108PEP-2025376085fe72. Method (410) for encoding a multi-channel waveform signal (14) into a data stream (16) using block-based prediction, the method (410) comprising: encoding (412) into the data stream (16) a commonality syntax element (13) indicating for a plurality of channels (21a-f) of the multi-channel waveform signal (14), whether, among a set (29) of prediction modes supported by the method, one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), if the commonality syntax element (13) indicates that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encoding (414) a set (31) of one or more prediction mode syntax elements into the data stream (16) which indicate a selected prediction mode (33) out of the set (29) of prediction modes, wherein the selected prediction mode (33) is the one prediction mode (25), or a set (31) of one or more prediction mode syntax elements encoded for a first channel (21a) among the plurality of channels (21 a-f) is to be appointed the one prediction mode (25), or a default prediction mode (35) among the set (29) of prediction modes is to be used as the one prediction mode (25), and encoding each of the plurality of channels (21 a-f) using the one prediction mode (25), and if the commonality syntax element (13) does not indicate that one prediction mode (25) is commonly attributed to the plurality of channels (21 a-f), encoding (416), into the data stream (16), for each of the plurality of channels (21a- f), the set (31) of one or more prediction mode syntax elements, which indicate a selected prediction mode (39) out of the set (29) of prediction modes for the respective channel (21), and encoding each of the plurality of channels (21 a-f) using the selected prediction mode (39) for the respective channel (21).

73. Method (430) for encoding a multi-channel waveform signal (14) into a data stream (16) using block-based prediction, inter-channel transform-domain residual prediction and transform-based prediction residual encoding, the method (430) comprising: encoding (432) into the data stream (16) a further commonality syntax element (45) indicating for a plurality of channels (21a-f) of the multi-channel waveform signal (14),FH241108PEP-2025376085fewhether, among a set (51) of transform domains supported by the method, one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), if the further commonality syntax element (45) indicates that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), encoding (434) each of the plurality of channels (21 a-f) using the one transform domain (53) for the transform-based prediction residual encoding, and if the further commonality syntax element (45) does not indicate that one transform domain (53) is commonly attributed to the plurality of channels (21 a-f), encoding (436) each of the plurality of channels (21 a-f) using a selected transform domain (55), which is channel-individually selected out of the set (51) of transform domains, for the transform-based prediction residual encoding.

74. Method (450) for encoding a waveform signal into a data stream (16), the method (450) comprising: performing (451) sample-to-sample prediction (260) for a block (140CUrrent) of the waveform signal, to obtain a preliminary time-domain block predictor (214); spectrally filtering (300) the preliminary time-domain predictor to obtain a filtered time-domain block predictor (302); performing (452) transform-domain-to-transform-domain prediction (204a, b) for the block (140CUrrent) of the waveform signal to obtain a transform-domain predictor (208a, b); encoding (453) a residual spectrum (210) into the data stream (16), using which the transform-domain predictor (208a, b) is correctable to obtain a corrected residual spectrum (224), which, when being subject to a re-transformation (226), yields a time-domain residual signal (224) for correcting (230) the time-domain block predictor (302), wherein the method (450) further comprises: performing (454) the spectrally filtering (300) the preliminary time-domain predictor (214) using a transfer function being higher in a first spectral region (61a) than compared to a second spectral region (61 b), andFH241108PEP-2025376085feperforming (455) the transform-domain-to-transform-domain prediction (204a, b) spectrally restricted to the second spectral region (61b), or by obtaining a preliminary transform-domain predictor and spectrally filtering (300) the preliminary transform-domain predictor using a transfer function being higher in the second spectral region (61 b) than compared to the first spectral region(61a) to obtain the transform-domain predictor; or by performing filter synthesis using an impulse response which is higher in the second spectral region (61b) than compared to the first spectral region (61a).

75. Data stream (16) having encoded therein a digital wave form signal (14) using the apparatus (10) according to any of claims 35 to 69.

76. Computer program comprising instructions that, when running on one or more processors perform the method according to any of claims 69 to 74.FH241108PEP-2025376085fe

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