MX2008012280A - Reduced number of channels decoding. - Google Patents

Abstract

An intermediate channel representation of a multi-channel signal can be reconstructed highly efficient and with high fidelity, when upmix parameters for upmixing a transmitted downmix signal to the intermediate channel representation are derived that allow for an upmix using the same upmixing algorithms as within the multi-channel reconstruction. This can be achieved when a parameter re-calculator is used to derive the upmix parameters that takes into account also parameters having information on channels that are not included in the intermediate channel representation.

Description

REDUCED NUMBER OF CHANNEL DECODIFICATION Field of the Invention The present invention relates to the decoding of audio signals and in particular to the decoding of a multi-channel, or multichannel, downstream parametric conversion of an original multi-channel signal to a smaller number of channels than the number of channels of the original multi-channel signal.

BACKGROUND OF THE INVENTION The recent development of audio coding has made possible the ability to recreate a multi-channel, or multichannel, representation of an audio signal based on a stereo (or mono) signal and the corresponding control data. These methods differ substantially from the older matrix-based solutions, such as Dolby Prologic, since the additional control data is transmitted to control recreation, also referred to as the up-conversion, of the surround channels based on the mono or stereo channels transmitted. Thus, such multi-channel parametric audio decoder, for example MPEG Envelope, reconstructs N channels based on M transmitted channels, where N > M, and in basis to the additional control data. The additional control data represents a significantly lower data rate than the transmission of all N channels, making the coding very efficient, while, at the same time, ensuring compatibility with both M-channel devices and N-devices. channels. These parametric envelope encoding methods usually include a parameterization of the envelope signal based on the Inter-Channel Intensity Difference (IID) and the Inter-Channel Coherence (ICC). These parameters describe energy relationships and correlation between pairs of channels in the up-conversion process. Additional parameters, also used in the prior art, include the prediction parameters used to predict the intermediate or output channels during the up-conversion procedure. Two famous examples of such multichannel coding are BCC coding and enveloping MPEG. In BCC coding, a number of input audio channels are converted to a spectral representation using a transformation based on the Discrete Fourier Transform (DFT) with overlapping windows. The resulting uniform spectrum is then divided into non-superimposed partitions. Each partition has a bandwidth proportional to the equivalent rectangular bandwidth (ERB, for its acronym in English). Then, the spatial parameters called Level Difference Between Channels (ICLD) and Time Difference Between Channels (ICTD) are estimated for each partition. The ICLD parameter describes a difference level between two channels and the ICTD parameter describes the time difference (phase change) between two signals from different channels. Level differences and time differences are given for each channel with respect to a common reference channel. After the derivation of these parameters, the parameters are quantized and encoded for transmission. The individual parameters are estimated with respect to the single reference channel in the BCC coding. In other parametric envelope coding systems, for example in the MPEG envelope, a parametrization with tree structure is used. This means that the parameters are no longer estimated with respect to a single common reference channel, but with different reference channels that can still be a combination of channels of the original multi-channel signal. For example, having a 5.1 channel signal, the parameters can be estimated between a combination of the front channels and between a combination of the subsequent channels.

Of course, backwards compatibility with currently established audio standards is highly desirable also for parametric coding schemes. For example, having a signal converted to mono downward, it is desirable that a possibility of creating a stereo reproduction signal with high fidelity is also provided. This means that a monophonic signal converted downwards has to be converted upwards into a stereo signal, making use of the additional parameters transmitted in the best possible way. A common problem in multi-channel coding is the preservation of the energy in the upward conversion, since the human perception of the spatial position of a sound source is dominated by the sound intensity of the signal, that is, by the energy contained inside the signal. Therefore, extreme care must be taken in the reproduction of the signal to attribute the correct sound intensity to each reconstructed channel, in such a way that the introduction of artifacts that greatly diminish the perception of the quality of the reconstructed signal is avoided. Since during the down conversion, the amplitudes of the signals are commonly summed, the possibility of interference increases, being described by the correlation or coherence parameter.

When it comes to the reconstruction of a small number of channels (a number of channels less than the number original channels of the multichannel signal), schemes such as the BCC are simple to use, since each parameter is transmitted with respect to the same single reference channel. Therefore, having knowledge about the reference channel, the most relevant level of information (absolute measure of energy) can easily be derived for each channel needed for the upward conversion. In this way, a reduced number of channels can be reconstructed without the need to reconstruct the complete multichannel signal in principle. Thus, the computation of the energy for the energies of the multichannel signal is simpler in the BCC when using unique variables instead of the products of the variables, but this is only a first step. When discussing the derivation of energies and correlations from a small number of channels, which should be as close as possible to the partial conversions downwards of the original multi-channel signals, the level of difficulty between the MPEG Envelope and the BCC is comparable. In contrast to this, a tree-based structure, such as the MPEG envelope, uses a parameterization in which the relevant information for each individual channel is not contained in a single parameter. Accordingly, in the prior art, the reconstruction of a reduced number of channels requires the reconstruction of the multi-channel signal followed by a down-conversion in the reduced amount. of channels so as not to violate the requirement of energy preservation. This has the obvious disadvantage of an extremely high computational complexity.

Brief Description of the Invention It is the object of the present invention to provide a concept for obtaining a reduced number of channels from a multi-channel parametric signal more efficiently.

In accordance with a first aspect of the present invention, this objective is achieved by means of a parameter calculator to derive the parameters of the up-conversion to up-convert a down-converted signal to an intermediate channel representation of a multichannel signal with more channels than the coinverted signal and fewer channels in the multichannel signal, the signal having a downward effect having the multichannel parameters associated therewith describing the spatial properties of the multichannel signal, in which the multichannel signal it includes channels that are not included in the intermediate channel representation and in which multichannel parameters include training on channels not included in the intermediate channel representation, the parameter calculator includes: a parameter re-calculator to derive the parameters of upward conversion from the multichannel parameters using the parameters with informs tion on channels not included in the intermediate channel representation. In accordance with a second aspect of the present invention, this objective is achieved by means of a channel reconstructor with a parameter reconstructor, which includes: a parameter calculator to derive the conversion parameters upwards to convert upwards a downconverted signal in an intermediate channel representation of a multi-channel signal with more channels than the downconverted signal and fewer channels than the multichannel signal, the downconverted signal having the multichannel parameters associated therewith that describe the spatial properties of the multichannel signal, in which the multichannel signal includes the channels not included in the intermediate channel representation and in which the multichannel parameters include the information on the channels not included in the intermediate channel representation; including the parameter calculator: a parameter recalculator for deriving the parameters converted upwards from the multichannel parameters using the parameters with the information on the channels not included in the intermediate channel representation; and a converter on the upside to derive the intermediate channel representation using the up conversion parameters and the down converted signal.

In accordance with a third aspect of the present invention, this objective is achieved by means of a method for generating the up-conversion parameters to up-convert a down-converted signal to an intermediate channel representation of a multichannel signal. with more channels than the down-converted signal and fewer channels than the multichannel signal, the down-converted signal having the multichannel parameters associated with it that describe the spatial properties of the multichannel signal, in which the multichannel signal includes the channels not included in the intermediate channel representation and in which the multichannel parameters include information about the channels not included in the intermediate channel representation; including the method: the derivation of the up-conversion parameters from the multichannel parameters using the parameters with the information on the channels not included in the intermediate channel representation. In accordance with a fourth aspect of the present invention, this objective is achieved by an audio receiver or an audio player, the audio receiver or player having a parameter calculator to derive the conversion parameters upward to convert to the raises a down-converted signal in an intermediate channel representation of a multichannel signal with more channels than the signal converted to the low and less channels than the muitic signal, the signal having been converted downwards the multichannel parameters associated therewith which describe the spatial properties of the multichannel signal, in which the multichannel signal includes the channels not included in the intermediate channel representation and in which multichannel parameters include information about the channels not included in the intermediate channel representation; including the parameter calculator: a parameter recalculator to derive the up-conversion parameters from the multichannel parameters using the parameters with the information on the channels not included in the intermediate channel representation. In accordance with a fifth aspect of the present invention, this objective is achieved by means of a method of receiving or reproducing audio, the method having a method to generate up conversion parameters to convert upward a converted signal to the low in an intermediate channel representation of a multichannel signal with more channels than the signal converted to the low and fewer channels than the multichannel signal, the signal having been converted downwards the multichannel parameters associated therewith describing the spatial properties of the signal multichannel signal, in which the multichannel signal includes the channels not included in the intermediate channel representation and in the which multichannel parameters include information about the channels not included in the intermediate channel representation, the method including: the derivation of the up-conversion parameters from the multichannel parameters using the parameters with the information about the channels not included in the intermediate channel representation. The present invention is based on finding that an intermediate channel representation of a multichannel signal can be reconstructed in a highly efficient manner and with high fidelity when the parameters are converted upwards, in order to convert upwards a transmitted signal converted downwards in the representation of intermediate channel, are derivatives so that they allow the upward conversion using the same conversion algorithms upwards that those of the multichannel reconstruction. This can be achieved when a parameter re-calculator is used to derive the conversion parameters upwards taking into account also the parameters with the information on the channels not included in the intermediate channel representation. In one embodiment of the present invention, a decoder is capable of reconstructing an output stereo signal from a downward parametric conversion of a five-channel multichannel signal, including downward parametric conversion a monophonic signal converted to the downside and associated multi-channel parameters. In accordance with the invention, the spatial parameters are combined to derive the up-conversion parameters for the up-conversion of a stereo signal, in which the combination also takes into account the multi-channel parameters not associated with the left channel. frontal or the right-frontal channel. In this way, the absolute energies for the upstream stereo channels can be derived and a measure of coherence between the right and left channels can be derived allowing a high-fidelity stereo reconstruction of the multichannel signal. In addition, an ICC parameter and a CLD parameter are derived, allowing up-conversion to use existing algorithms and implementations. Using the parameters of the channels not associated with the reconstructed stereo channels allows the preservation of the energy within the signal with greater precision. This is of great importance, since the uncontrolled variations of the sound intensity greatly disturb the quality of the reproduced signal. Generally, the application of the inventive concept allows a reconstruction of a stereo conversion upwards from a mono down conversion of a multichannel signal, without the need for a total intermediate reconstruction of the multichannel signal, as in art methods. previous. Obviously, the computational complexity of the The side of the decoder can thus be significantly reduced. Also, using the multichannel parameters associated with the channels not included in the upward conversion (ie, the left frontal channel and the right frontal channel), a reconstruction is allowed that does not introduce any additional artifact or variations of sound intensity, but which instead perfectly preserves the energy of the signal. To be more specific, the energy ratio between the reconstructed left and right channels is calculated from numerous available multichannel parameters, also taking into account the multichannel parameters not associated with the left front and right frontal channels. Obviously, the ratio of the sound intensity between the reconstructed (converted to the upward) left and right channels is dominant with respect to the quality of the perception of the audio of the reconstructed stereo signal. Without the use of the inventive concept, a reconstruction of channels with the precisely correct energy ratio is not possible in the tree-based structures discussed in this document. Therefore, the implementation of the inventive concept allows a high-quality stereo reproduction of a down-conversion of a multi-channel signal, based on multichannel parameters, which are not derived for an accurate reproduction of a stereo signal.

It should be noted that the inventive concept can also be used when the number of reproduced channels is different from two, for example, when a central channel must also be reconstructed with high fidelity, as in the case of some reproduction environments. Within the following, a more detailed review of the multi-channel coding schemes of prior art (particularly of tree-based structures) will be given to underline the high benefit of the inventive concept.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention are described subsequently when referring to the indicated figures, in which: Figure 1 shows the examples of the tree-based parameterizations; Figure 2 shows the examples of the tree structure decoding schemes; Figure 3 shows an example of a multi-channel coder of the prior art; Figure 4 shows the examples of the decoders of the prior art; Figure 5 shows an example of the stereo reconstruction of the prior art of a down-converted multichannel signal; Figure 6 shows a block diagram of an example of an inventive parameter calculator; Figure 7 shows an example of an inventive channel reconstructor; and Figure 8 shows an example of an inventive audio receiver or player.

Detailed Description of the Invention The inventive concept will be described below, mainly with respect to MPEG coding, but also applicable to other schemes based on the parametric coding of multichannel signals. That is, the embodiments described as follows are merely illustrative for the principles of the present invention, for a reduced number of channel decoding for multi-channel tree structure systems. It is understood that the modifications and variations of the modalities and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the limit be only the approach of the imminent claims of the patent and not the specific details presented only as a description and explanation of the modalities of this text. As mentioned above, in some surround parametric coding systems, for example MPEG Envelope, a tree structure parameterization is employed. Such parameterization is diagrammed in Figures 1 and 2. Figure 1 shows two ways of parameterg a standard 5.1 channel audio scenario, with a left front channel 2, a center channel 3, a front right channel 4, a left surround channel 5 and a right channel Envelope 6. Optionally, a low frequency breeding channel 7 (LFE) can also be presented. Generally, individual channels, or channel pairs, are characterized by multichannel parameters from one another, such as, for example, by an ICC correlation parameter and a CLD level parameter. The possible parameterizations will be explained briefly in the following paragraph, the resulting tree structure decoding schemes are then illustrated in Figure 2. In the example shown on the left side of Figure 1 (parameterization 5-l-5i), the Multichannel signal is characterized by the CLD and ICC parameters that describe the relationship between the left surround channel 5 and the right surround channel 6, the left front channel 2 and the right front channel 4, and between the center channel 3 and the improvement channel low frequency 7. However, since all the configuration must be converted downwards into a single mono channel, for a complete description of the group of channels, additional parameters are required. Therefore, the additional parameters (CLDi, ICCi) are used, relating a combination of the LFE speaker 7 and the center speaker 3 with a combination of the left front channel 2 and the right front channel 4. Additionally, an additional group of parameters (CLD0, ICC0), these parameters describe a relationship between the combination of the surround channels 5 and 6 with the rest of the channels of the multichannel signal. In the parameterization of the right side (parameterization 5-l-52) the parameters are used, relating the left front channel 2 and the left envelope channel 5, the front right channel 4 and the right surround channel 6, and the center channel 3 and the low frequency improvement channel 7. The additional parameters (CLDi and ICCi) describe a combination of the left channels 2 and 5, with respect to the combination of the right channels 4 and 6. An additional group of parameters (CLD0 and ICC0 ) describe the relationship of a combination of the center channel 3 and the LFE channel 7 with respect to a combination of the remaining channels. Figure 2 shows the coding concepts that support the different parametrizations of Figure 1. On the decoder side, called OTT (for its acronym in English, One To Two), modules are used in a structure similar to the tree. Each OTT module converts a mono signal into two output signals. When they are decoded, the parameters for the OTT blocks have to be applied in the reverse order of the coding. Accordingly, in the tree structure 5-l-5i, the OTT module 20, which receives the down-converted signal 22 () is operative to use the parameters CLD0 and ICC0 to derive two channels, one being a combination of the left surround channel 5 and the right surround channel 6, and the other channel still being a combination of the remaining channels of the multichannel signal. Accordingly, the OTT module 24 derives the first channel, using CLDi and ICClf being a combined channel of the center channel 3 and the low frequency channel 7, and a second channel being a combination of the left front channel 2 and the front right channel 4 Likewise, the OTT module 26 derives the left envelope channel 5 and the right channel envelope 6, using CLD2 and ICC2. The OTT module 27 derives the center channel 3 and the low frequency channel 7, using CLD4, and the OTT module 28 derives the front left channel 2 and the right front channel 4, using CLD3 and ICC3. Finally, a reconstruction of the entire group of channels 30 is derived from a single monophonic channel converted to the down 22. For the tree structure 5-l-52, the general scheme of the OTT module is equivalent to the tree structure 5-l-5i. However, the OTT modules alone derive different combinations of channels, the channel combinations corresponding with the parameterization marked in Figure 1 for the case 5-l-52. It becomes evident from Figures 1 and 2 that the tree structure of the different parameterizations is only a visualization of the parameterization used.

Additionally, it is more important to note that the individual parameters are parameters that describe a relationship between the different channels in contrast to, for example, the BCC coding scheme, in which similar parameters are derived with respect to a single reference channel. Therefore, in the parameterization shown, the individual channels can not be derived simply by using the parameters associated with the OTT blocks in the display, but some or all of the remaining parameters have to be taken into account additionally. The tree structure of the parameterization is only a visualization of the current flow or process of the signal, shown in Figure 3, illustrating the upward conversion from a low number of transmitted channels, achieved by means of matrix multiplication. . Figure 3 shows the decoding based on a received channel converted downward 40. The down converted channel 40 is sent as an input to a up conversion block 42, deriving the reconstructed multi-channel signal 44, in which the Channel composition differs between the settings used. However, the matrix elements of the hue, used by the reconstruction block 42, are derived directly from the tree structure. The reconstruction block 42 can be further decomposed in a prior matrix to the de-correlator 46, for illustrative purposes only, deriving additional decorrelated signals from the transmitted channel 40. These are then sent as input to a conversion matrix 48 which derives the multichannel signals 44 when converting the individual input channels. As shown in Figure 4, a direct approach to reduce the number of reconstructed channels would simply "prune" the tree from blocks one to two. Figure 4 shows a possible pruning of the trees on the dotted lines, omitting pruning the OTT modules on the right side of the tree during reconstruction, thus reducing the number of exit channels. However, using the settings of the prior art, shown in Figures 1 and 2, introduced because they offer the low bitrate encoding with the highest possible quality, simple pruning is not possible to obtain a stereo output that represents a downward conversion of the left side and a downward conversion of the right side of the original multichannel signal appropriately. Figure 5 shows an approach of the prior art to create a stereo output from the signals described above, using the obvious approach of first reconstructing the multichannel signal completely before converting the signal down sequentially in the stereo representation , using a Down converter 60 additional. Obviously, this has many disadvantages, such as high complexity and inferior sound quality. A solution to the aforementioned problem of obtaining the stereo output from a mono down conversion and parametric envelope parameters in a parameterization that does not naturally support "pruning" to a stereo output will be derived to continuation for the general case. This is followed by two specific modalities that show the use of the inventive concept in the parameterizations described above. In this way, solutions are provided to the problem of obtaining the stereo output from a mono down conversion and parametric envelope parameters in a parameterization that does not support "pruning" to a stereo output. The general approach of the re-calculation of the parameter will be seen later. In particular, it applies to the case of the computation of the stereo output parameters from an arbitrary number of N multichannel audio channels. It is further assumed that the audio signal is described by a sub-band representation, derived by using a bank of filters that could be real-valued or modulated in a complex way. Let all signals be considered as finite vectors of subband samples corresponding to a time-frequency frame, defined by the spatial parameters, and let the sub-band samples of a multi-channel audio signal reconstructed and formed from sub-band samples of the audio channels mi, m2, K , mM and the uncorrelated sub-band samples of the audio channels di, d2, K, dD, in accordance with a matrix conversion operation up and = Rx, where All signals being considered as vectors followed. The matrix R is of size N x (M + D) and represents the combined effect of the matrices MI and M2 of Figure 3 and the up conversion block 42 in such a way. A general method to achieve an appropriate energy and correlation parameters of a version converted to the downstream to iVD channels of the sub-band samples of the original multichannel audio signal is to form the covariance matrix of the virtual conversion to the defined downstream by a matrix D of conversion to the low ND x N, This covariance matrix can be computed by multiplication with the transposed complex conjugate, which is where the internal covariance matrix xx * is often known from the properties of the de-correlators and the transmitted parameters. An important special case, where this holds true, is for M = 1, and often this internal covariance matrix is in fact then equal to the identity matrix of size M + D. As a consequence, for a stereo output where ND = 2 , the CLD and ICC parameters can be read from A > ('' o) in the sense that Notice here, and then, that the following notation is applied. For the complex vectors x, y, the complex internal product and the square norm is defined by ? | * («) | 2,? where the asterisk denotes the complex conjugation. Subsequently, two embodiments of the present invention must be derived for the different parameterizations (5-1-5! And 5-l-52) shown in Figures 1 and 2. In the embodiments of the present invention, it is taught that, for output the signals based on a mono down conversion and the corresponding parameters of the MPEG envelope (multi-channel parameters), the up-conversion parameters need to be re-calculated as a unique group of CLD and ICC parameters that can be used to directly convert a stereo signal from the mono signal to the boost. Additionally, it is assumed that the processing of the individual audio channels is carried out in the form of intelligent frames, that is, in discrete portions of time. In this way, when speaking of powers or energies contained within a channel, the term "power" or "energy" should be understood as the power of the power contained within a frame of a specific channel.

Generally, parameters such as CLD and ICC are also valid for a single frame. Having a square with k samples of value a, the energy E within the square can be, for example, represented by the sum of the squares of the values of the sub-band sample within the square: The channel level differences (CLD), transmitted and used for the calculation of the up-conversion parameters to convert upwards the M signal converted to the downside, into an intermediate anal representation ( stereo) of the multichannel signal, are defined as follows: Where L0 and Ro denote the energy of the signals in question, within the frame for which the CLD parameter must be derived. Therefore, for the case 5-l-5i, the four parameters CLD, CLDX, X = 0,1,2,3, can be used to obtain normalized channel energies by the energy of the mono channel converted to the low m .

= (C10C1! C23) ' C = (c, 0c2!), = (c2ocn) ' Channel earnings are defined The final goal is to derive optimal stereo channels 10 and r0, in the sense that there is the appropriate estimation of the normalized energies and the correlation of the stereo channels (intermediate channel representation), formed by l0 = l + qc, with / = G (/ ^ - + / í), so that L = Lr + Ls, rQ = r + qc, with r = G (f + rx), so that R = Rf + Rs, where the central weight of conversion to the downside is g = 1 / V2. The energies computed from this assumption turn out to be LQ = L + q2C + 2Rc (l, qc), Rü = R + q2C + 2Re (r, qc).

Reflects to be the most beneficial to suppose that both, the combined left channel 1 and the combined right channel r, are not correlated with the central channel c, instead of trying to incorporate the information and the correlation carried by the parameters ICC1, mx, X = 0.1. Therefore, the normalized energies of the output stereo channels are estimated as r r r C Having derived the energies from the output channels the desired CLD parameter can be easily computed using the definition of the CLD parameter given above. In accordance with the inventive concept, an ICC parameter is derived to allow a stereo conversion to rise. The correlation between the two output channels is defined by the following expression: p = Re (/ 0, r0.}. = q2C + Re { /, r) + qRe (c, l + r).

An attractive group of simplifying assumptions is found here again, so that the combined left channel 1 and the combined right channel r are not correlated with the center channel c, and further, so that the surround channels are not correlated with the channels Frontal These assumptions can be expressed as Re { c, / + r) = 0, Re { /, r) = Re (/, r /) + Re (/ i, ri) The resulting estimate for p depends on the two parameters ICC, ICCX, X = 2.3, which describe the normalized left / right correlations that can be written as P ~ 2 ' In this way, the final correlation value depends on several parameters of the multichannel parameterization, allowing the reconstruction of high fidelity of the signal. The ICC parameter is finally derived using the following formula: In accordance with the inventive concept, the energy distribution between the reconstructed channels is reconstructed with high precision. However, a Global scaling of energy applied to both channels may be necessary globally, to ensure the preservation of total energy. As the relative distribution of energy between the channels is vital for the spatial perception of the reconstructed signal, global scaling can deteriorate the perceptual quality of the reconstructed signal. It should be emphasized that global scaling is only global within a time-frequency table defined in a parameter locally in the scaling of parameter tables. In other words, the two gains, of frequency and time, will be applied, which results in spectral coloration artifacts and time modulation. A gain adjustment factor for global scaling is necessary to ensure that the up-conversion stereo process is preserving the energy of the mono channel converted to the low m. However, this factor is defined by g = ^ Lo + Ro, which results in g = 1, for the configuration 5-l-5i, since L0 + Ro = Lf + Rf + C + Ls + Rs = 1. As an additional embodiment, the application of the inventive concept to the tree structure 5-l-52 will be described in the following paragraphs. For the creation of a high-fidelity stereo signal, the first two groups of CLD and ICC parameters, which correspond to the upper branches of the tree, are relevant.

The two parameters CLD, CLDX for X = 0.1, are used primarily to obtain normalized channel energies from the combined left and right channels and the central channel C = c2 where the channel earnings are defined by CLDX / \ Q 10 C] X Vi + io0"" 0 and Ü2X V i + i oCI¾ / 1 ° The goal is to derive the energies and the correlation of channels converted downwards / 0 = / + qc, r0 = r + qc, where the weight of the central channel is q = 1 / V2. The computation of the energies from this assumption turns out to be LQ = L + q2C + 2Rc (¡, qc), = R + q2C + 2Re (r, qc).

A beneficial assumption here is that both ICC, between channels I and c and between channels r and c, is the same that is given by ICC0 between channels 1 + r and c. This assumption results in the estimated with the estimates of the normalized energies that become As in the previous modality, having the energy values L0 and R0, the desired CLD parameter can be derived: The derivation of the correlation and finally of the ICC parameter starts from the general definition of the correlation value: p = Re (/ 0, r0) = q 2 C + Re =. { /, r) + q Re (c, I + r) All the necessary information is available from the parameters of the tree structure 5-l-52, since \\! + r \ f = L + R + 2 Re { /, r), The final results can be written as > = ¿+ - + yÍ2ICC0cl0c. { , c2 20 ' RQ = R + - + Í2JCCQclQc2ic2Q, The required adjustment factor of gain gr is defined by It can be noted that the generated CLD and ICC parameters can be further quantified to allow the use of location tables in the decoder for the creation of the up conversion matrix, instead of performing the complex calculations. This further increases the efficiency of the up conversion process. Generally, the upward conversion is possible using existing OTT modules. This has the advantage that the inventive concept can be implemented in a simple manner in already existing decoding scenarios. Generally, the up conversion matrix can be described as: C, COS (Ú: +?) C, sin (a +?) c, cos (-a +?) c2 sin (-a +?) r where: 10 CIDno c, = CLD IQ c-, = CLD.10 1 + 10 '1 + 1 0 c7 c. ß = arelan tan (cr) and = - arceos (/ CC). c, + c, Therefore, having inventively derived the CLD and ICC parameters, the upward stereo conversion of a down-conversion transmitted can be performed with high fidelity using standard up-conversion modules. In a further embodiment of the present invention, an inventive channel reconstruction includes a parameter calculator for deriving up-conversion parameters and an up-converter to derive an intermediate channel representation using the conversion parameters to the rise and a transmitted signal converted to the downside. The inventive concept is underlined again in Figure 6, showing an inventive calculator of parameter 502, which receives various ICC parameters 504 and various CLD parameters 506. In accordance with one embodiment of the present invention, the inventive parameter calculator 502 derives a unique CLD 508 parameter and a single ICC 510 parameter for the recreation of a stereo signal, also using the multichannel parameters (ICC and CLD) with information about the channels not included or related to the channels of the stereo conversion upwards. It should be noted that the inventive concept can easily be adapted to scenarios with an upward conversion that includes more than two channels. Upconversion occurs in the general defined sense as an intermediate channel representation of the multichannel signal, in which the intermediate channel representation has more channels than the downconverted signal and fewer channels than the multichannel signal . A common scenario is a configuration in which an additional central channel is reconstructed. The application of the inventive concept is underlined again in Figure 7, showing the inventive calculator of parameter 502 and an OTT block 1 to 2 520. Block OTT 520 receives as input the mono transmitted signal 522, as already detailed in the Figure 6. The inventive parameter calculator 502 receives several ICC values 504 and several CLD values 506 to derive a unique CLD 508 parameter and a unique ICC 510 parameter. The unique CLD and ICC parameters, 508 and 510, are sent as input to the OTT module 520, to guide the up-conversion of the down-converted monophonic signal 522. Thus, at the output of the OTT 520 module, a Stereo signal 524 can be provided as an intermediate channel representation of the multichannel signal. Figure 8 shows an audio receiver or player 600 inventive, with an inventive audio decoder 601, a bitstream input 602, and an audio output 604.

A bit stream may be the input at the input 602 of the inventive audio receiver / player 600. The decoder 601 then decodes the bit stream and the decoded signal is output or reproduced at the output 604 of the inventive audio player / receiver 600. Although the inventive concept has been underlined mainly with respect to MPEG Envelope coding, it is by no means limited to the application of the specific parametric coding scenario. Due to the high flexibility of the inventive concept, it can be simply applied to other coding schemes, as well as to, for example, 7.1 or 7.2 channel configurations or BCC schemes.

Although the embodiments of the present invention, which relate to MPEG coding, introduce some simplifying assumptions for the generation of the common CLD and ICC parameter, this is not imperative. It is also possible, of course, not to introduce those simplifications. Depending on certain implementation requirements of the inventive methods, the inventive methods can be implemented in hardware or software. The implementation can be carried out using a digital storage medium, particularly on disk, DVD or CD with electronically readable control signals stored therein, which cooperate with a programmable computing system so that the inventive methods are performed. Generally, the present invention is, therefore, a computer programmable product with a program code stored in a machine readable carrier, the program code being operative to perform the inventive methods when the computer program product is executed in a computer program. a computer. In other words, the inventive methods are, accordingly, a computer program with a program code to carry out at least one of the inventive methods when the computer program is executed on a computer. While the above has been described and shown in a particular way in relation to the particular modalities from this, it will be understood by those with skill in the art that various other changes in form and details can be made without departing from the spirit and focus of this. It is understood that several changes can be made in the adaptation of the different modalities without departing from the broader concepts described herein and comprised by the following claims.

Claims (1)

1. Claims 1. The parameter calculator for deriving the up-conversion parameters (508, 510) to up-convert a down-converted signal (522) into a stereo representation (524) of a multi-channel signal with more channels than the down converted signal (522) and fewer channels than the multi-channel signal, characterizing the stereo representation, (514) a downward conversion on the left side and a downward conversion on the right side (522) of the multichannel signal, the downconverted signal having the multi-channel parameters (504, 506) associated therewith that describe the spatial properties of the multichannel signal, in which the multichannel signal includes the channels not included in the stereo representation (524) and the multichannel parameters they include the information about the channels not included in the stereo representation (524), characterized in that it includes: a re-calculator of parameter (502) to derive the parameters of conv Upstream (508, 510) including a CLD parameter (508) and an ICC parameter (510) from the multichannel parameters (504, 506) using the parameters with the information about the channels not included in the stereo representation , the CLD parameter (508) with the energy information for a left channel and a right channel of the stereo representation and the ICC parameter (510) with information about a correlation between the left and right channel. The parameter calculator according to claim 1, characterized in that the parameter re-calculator (502) is adapted to the use of multichannel parameters (504, 506) that describe the properties of the signal of a channel or a combination of channels of the multichannel signal with respect to another channel or other combination of multichannel signal channels. 3. The parameter calculator according to claim 2, characterized in that the parameter re-calculator (502) is operative to derive the up-conversion parameters (508, 510) that describe the same properties of the signal of the channels of the intermediate channel representation as the multi-channel parameters (504, 506). The parameter calculator according to claim 1, characterized in that the parameter re-calculator (502) is adapted to the use of the correlation parameters (ICC) (504) with the information about a correlation and the level parameters. (CLD) (506) with the energy information for a channel or a combination of channels of the multichannel signal with respect to another channel or other combination of channels of a multichannel signal. 5. The parameter calculator in accordance with the claim 4, characterized in that it is adapted to the use of multichannel parameters for a multichannel signal that includes a left front channel (LF, for its acronym in English) (2), enveloping left (LS) (5), frontal right (RF) (4), surrounding right (RS) (6) and central (C) (3) . The parameter calculator according to claim 5, characterized in that the parameter re-calculator (502) is operative to derive the CLD parameter (508), using: a first CLD parameter (CLD0) with energy information for a combination of channel LS (5) and RS (6) and a combination of the remaining channels of the multichannel signal; a second parameter (CLDi) with energy information for a combination of the LF (2) and RF (4) channel and the central channel (C) (3); a third parameter (CLD2) with energy information for the LS (5) and RS (6) channels; and a fourth CLD parameter (CLD3) with energy information for the LF (2) and RF (4) channels. The parameter calculator according to claim 6, characterized in that the parameter re-calculator (502) is operative to derive the CLD parameter in accordance with the following formula: where L0 and o are the normalized energies of the output stereo channels L and R (524) derived by c L0 = Lf + Ls + -2 'C In which the energies of multichannel signals are derived from the CLD parameters as follows: C = (CIOC2l) '= (C20C! 2)' 8. The parameter calculator according to claim 5, characterized in that the parameter re-calculator (502) is operative to derive the ICC parameter (510) using: a first CLD parameter (CLD0) with information from the energy for a combination of the LS (5) and RS (6) channel and a combination of the remaining channels of the multichannel signal: a second parameter (CLDX) with energy information for a combination of the LF (2) and RF ( 4) and the central channel (C) (3): a third parameter (CLD2) with energy information for the LS (5) and RS (6) channels; and a short parameter CLD (CLD3) with energy information for the LF (2) and RF (4) channels; a first ICC parameter (ICC2) with correlation information between the LS (5) and RS (6) channels; and a second ICC parameter (ICC3) with information on the correlation between the LF (2) and RF (4) channels. 9. The parameter calculator according to claim 8, characterized in that the ICC parameter (510) is derived in accordance with the following formula: in which an estimated p of the correlation is defined as where CLDxno 1 and c 2X ~, CLDxnO 1 + 10 ' 10. The parameter calculator according to claim 5, characterized in that the parameter re-calculator is operative to derive the CLD parameter (508), using: a first CLD parameter (CLD0) with information of the central channel energy (C) (3) and a combination of other multichannel signal channels; a second CLD parameter (CLDx) with energy information for a combination of the LF (2) and LS (5) channel and a combination of the RF (4) and RS (6) channels; an ICC parameter (ICC0) with information of the correlation between the central channel (C) (3) and a combination of other channels of the multichannel signal. 11. The parameter calculator according to claim 10, characterized in that the parameter CLD (508) is derived from the following formula: in which L0 and R0 are the normalized energies of the output stereo channels L and R derived by where # = (c.oc21) 2 ' 12. The parameter calculator according to claim 5, characterized in that the parameter re-calculator (502) is operative to derive the ICC parameter (510) using: a first CLD parameter (CLD0) with energy information of the central channel ( C) (3) and a combination of other channels of the multichannel signal a second CLD parameter (CLDX) with energy information for a combination of the LF (2) and LS (5) channel and a combination of the RF channel (4) and RS (6); a first ICC parameter (ICC0) with information of the correlation between the central channel (C) (3) and a combination of other channels of the multichannel signal; and a second ICC parameter (ICCi) with information from correlation between a combination of channel LF (2) and LS (5) and a combination of channel RF (4) and RS (6). The parameter calculator according to claim 5, characterized in that the parameter re-calculator (502) is operative to derive the ICC value using the following formula: where the correlation measure p is derived as with Y 1 . The parameter calculator according to claim 5, characterized in that the parameter re-calculator (502) is operative to use the multi-channel parameters (504, 506) that describe a sub-band representation of the multichannel signal. 15. The parameter calculator according to claim 1, characterized in that the parameter re-calculator (502) is operative to use complex valued multichannel parameters (504, 506). 16. The channel reconstructor with a parameter reconstructor, characterized in that it includes: a parameter calculator according to claim 7; and an up-converter (520) to derive the stereo representation (524) using the up-conversion parameters (508, 510) and the down-converted signal (522). 17. The method for generating the up-conversion parameters (508, 510) to up-convert a down-converted signal (522) into a stereo representation (524) of a multichannel signal with more channels than the converted signal down and less channels than the multichannel signal, the stereo representation characterizing a downward conversion on the left side and a downward conversion on the right side of the multichannel signal, the signal having been converted downwards to the multi-channel parameters (504, 506) associated therewith which describe the spatial properties of the multichannel signal, wherein the multichannel signal includes the channels not included in the stereo representation and in which the multichannel parameters (504, 506) include the information on channels not included in the stereo representation; characterized in that the method includes: deriving the up-conversion parameters (508, 510) including a CLD parameter (508) and an ICC parameter (510) from the multichannel parameters using the parameters with information about the channels not included in the the stereo representation (524), the CLD parameter (508) with energy information for a left and right channel of the stereo representation and the ICC parameter (519) with information on a correlation between the left and right channel. 18. The audio receiver or player (600), the audio receiver or player having a parameter calculator (601) to derive the up-conversion parameters to up-convert a down-converted signal to a stereo representation of a multi-channel signal with more channels than the down-converted signal and fewer channels than the multi-channel signal, the stereo representation characterizing a downward conversion on the left side and a downward conversion on the right side of the multichannel signal, having the signal converted downwards the multichannel parameters associated therewith which describe the spatial properties of the multichannel signal, in which the multichannel signal includes the channels not included in the stereo representation and in which the multichannel parameters include information about the channels not included in the stereo representation; characterized the parameter calculator because it includes: a parameter re-calculator to derive the up-conversion parameters including a CLD parameter and an ICC parameter from the multichannel parameters using the parameters with information about the channels not included in the representation stereo, the CLD parameter informing the energy for a left and right channel of the stereo representation and tending to the ICC parameter information about a correlation between the left and right channel. 19. The method for receiving or reproducing audio, the method having a method for generating up-conversion parameters for up-converting a down-converted signal into a stereo representation of a multichannel signal with more channels than the converted signal. the low and fewer channels than the multichannel signal, the stereo representation characterizing a downward conversion on the left side and a downward conversion on the right side of the multichannel signal, the signal having been converted downwards with the multichannel parameters associated with this describe the spatial properties of the multichannel signal, in which the multichannel signal includes the channels not included in the stereo representation and in which the multichannel parameters include information on the channels not included in the stereo representation; characterized the method because it includes: deriving the conversion parameters upwards including a CLD parameter and an ICC parameter from the multichannel parameters using the parameters with information on the channels not included in the stereo representation, the CLD parameter having information on the energy for a left and right channel of the stereo representation and having the ICC parameter information about a correlation between the left and right channel. 20. The computer program with a program code to perform, when executed on a computer, a method to generate the up-conversion parameters to convert upwardly a down-converted signal into a stereo representation of a multi-channel signal with more channels than the down converted signal and fewer channels than the multichannel signal, the stereo representation characterizing a downward conversion on the left side and a downward conversion on the right side of the multichannel signal, having the signal converted downward the multichannel parameters associated therewith which describe the spatial properties of the multichannel signal, wherein the multichannel signal includes the channels not included in the stereo representation and in which the multichannel parameters include information about the channels not included in the stereo representation; characterized the method because it includes: deriving the conversion parameters upwards including a CLD parameter and an ICC parameter from the multichannel parameters using the parameters with information about the channels not included in the stereo representation, the CLD parameter having information of the energy for a left and right channel of the stereo representation and having the ICC parameter information about a correlation between the left and right channel. 21. The computer program with a program code to perform, when executed on a computer, a method for receiving or reproducing audio, the method having a method to generate up conversion parameters to convert upward a converted signal to the low in a stereo representation of a multi-channel signal with more channels than the down-converted signal and fewer channels than the multi-channel signal, the stereo representation characterizing a downward conversion on the left side and a downward conversion on the right side of the multichannel signal, having the signal converted downwards the multichannel parameters associated therewith which describe the spatial properties of the multichannel signal, in which the multichannel signal includes the channels not included in the stereo representation and in the that the multichannel parameters include information about the channels not included in the stereo representation; characterized the method because it includes: deriving the conversion parameters upwards including a CLD parameter and an ICC parameter from the multichannel parameters using the parameters with information about the channels not included in the stereo representation, the CLD parameter having information of the energy for a left and right channel of the stereo representation and having the ICC parameter information about a correlation between the left and right channel.