Multi-channel audio decoder, method and computer program using an adjustment of a contribution of a decorrelated signal

DESCRIPTION

MULTI CHANNEL AUDIO DECODER, METHOD AND COMPUTER PROGRAM USING ADJUSTMENT OF A DECORRELATED SIGNAL CONTRIBUTION

FIELD OF TECHNIQUE

One embodiment according to the invention relates to a multi-channel audio decoder for providing at least two output audio signals based on a coded representation.

Another embodiment according to the invention relates to a method for providing at least two output audio signals based on a coded representation.

Another embodiment according to the present invention relates to a computer program for carrying out the method. Generally, some embodiments according to the invention relate to a parametric and residual combined encoding.

BACKGROUND OF THE INVENTION

In recent years, the need for storage and transmission of audio content has progressively increased. Moreover, quality requirements for the storage and transmission of audio content have also progressively increased. In this way, the concepts for encoding and decoding audio content have been improved. For example, so-called advanced audio coding (AAC) has been developed which is described for example in the international standard ISO / IEC 13818-7: 2003.

Moreover, some spatial extensions were produced, such as the so-called MPEG surround concept, which is described, for example, in the international standard ISO / IEC 23003-1: 2007. Further enhancements to the encoding and decoding of spatial information of audio signals are described in the international standard ISO / IEC 23003-2: 2010, which relates to so-called spatial audio object coding. In addition, a flexible (switchable) audio encoding / decoding concept, which provides the ability to encode both general audio and voice signals with good encoding efficiency and to handle multichannel audio signals, is defined in the international standard. ISO / IEC 23003-3: 2012, which describes the so-called unified voice and audio coding concept. WO 2009/141775 A1 discloses parametric stereo upmix using a downmix signal, a residual signal and a unrelated signal. However there is a desire to provide an even more advanced concept for efficient decoding of multi-channel audio signals.

SUMMARY OF THE INVENTION

According to the invention there is provided a multi-channel audio decoder for providing at least two mackerel audio signals based on a coded representation as set forth in claim 1. A method as set forth in claim 19 and a program are also provided. as set forth in claim 20. The invention is based on the finding that output audio signals can be obtained on the basis of a coded representation in a very efficient manner if a weighting describing a contribution of the uncorrelated signal to the weighted combination of a downmix signal, a uncorrelated signal. and a residual signal are adjusted depending on the residual signal. Thus, by adjusting the weight describing the contribution of the uncorrelated signal to the weighted combination of the residual signal dependence, it is possible to mix (or fade) between a parametric coding (or a mostly parametric coding) and a residual coding (or a mostly coding). without transmitting additional control information. Moreover, it was found that the residual signal, which is included in the coded representation, is a good indication for the weight describing the contribution of the uncorrelated signal to the weighted combination. since it is typically preferable to put a (comparatively) higher weight on the decorrelated signal if the residual signal is (comparatively) weak (or insufficient for a reconstruction of the desired energy) and to put a (comparatively) lower weight on the decorrelated signal if the residual signal is (comparatively) strong (or sufficient to reconstruct the desired energy). Thus, the aforementioned concept allows a gradual transition between a parametric coding (wherein, for example, desired energy characteristics and / or correlation characteristics are signaled by parameters and reconstructed by adding one that the uncorrelated signal) and a coding. residual (in

<td>residual signal is</td><td>used</td><td>for</td><td>rebuild</td><td>signs of</td><td>audio</td><td>in</td><td>output</td>

<td>- in some cases</td><td>, up until</td><td>same</td><td>the way of</td><td>wave of</td><td>signals</td><td>in</td><td>audio</td>

<td>output - with</td><td>base</td><td>on one</td><td>sign of</td><td>downmix).</td><td>Of this</td><td colspan="2">mode is</td>

It is also possible to adapt the technique to the reconstruction, and reconstruction quality, for the decoded signals without having an additional signaling overhead.

By determining the residual signal weighted correlation it may well be the weight that describes the contribution of the signal to the weighted combination dependent on and dependent on the correlated signal, adjusted to the characteristics of the signal, so that a good reconstruction quality of at least two Output audio signals based on the encoded representation (in particular, based on the downmix signal, the uncorrelated signal and the residual signal) can be achieved.

In a preferred embodiment, the multi channel audio decoder is configured to obtain upmix parameters based on the encoded representation and to determine the weight describing the contribution of the decorrelated signal to the weighted combination depending on the upmix parameters. Considering the upmix parameters, it is possible to reconstruct desired characteristics of the output audio signals (such as, for example, a desired correlation between the output audio signals, and / or the desired energy characteristics of the output audio signals). to get a desired value.

In a preferred embodiment, the multi-channel audio decoder is configured to determine the weight describing the contribution of the uncorrelated signal to the weighted combination, such that the weight of the uncorrelated signal decreases with increasing energy from one or more signals. residuals. This mechanism allows you to adjust the reconstruction accuracy of at least two output audio signals depending on the residual signal energy. If the energy of the residual signals is comparatively high, the weight of the contribution of the uncorrelated signal is comparatively small, so that the uncorrelated signal no longer adversely affects a high reproduction quality that is caused by the use of the residual signal. In contrast, if the residual signal energy is comparatively low, or even zero, a large weight is given to the unrelated signal, so that the unrelated signal can efficiently bring the characteristics of the output audio signals to desired values.

In a preferred embodiment, the multi-channel audio decoder is configured to determine the weight describing the contribution of the decorrelated signal to the weighted combination, such that a maximum weight, which is determined by a decorrelated signal upmix parameter, be associated with the uncorrelated signal if a residual signal energy is zero, and so that a zero weight is associated with the uncorrelated signal if a residual signal energy weighted with

<td>the use of</td><td>a residual signal weighting coefficient is</td>

<td>larger or</td><td>equal to an uncorrelated signal energy,</td>

<td>weighted</td><td>with the uncorrelated signal upmix parameter.</td>

This embodiment is based on the realization that the desired energy, which must be added to the downmix signal, is determined by the correlated signal energy, weighted with the uncorrelated signal upmix parameter. Thus, it is concluded that it is no longer necessary to add the uncorrelated signal if the residual signal energy, weighted with the residual signal weighting coefficient, is greater than or equal to said decorrelated signal energy, weighted with the upmix parameter of unrelated signal. In other words, the uncorrelated signal is no longer used to provide the at least two output audio signals if the residual signal is deemed to carry sufficient energy (e.g. sufficient to achieve sufficient total energy).

In a preferred embodiment, the multi-channel audio decoder is configured to compute a weighted energy value of the mismatched signal, dependent on one or more mismatched signal upmix parameters, and to compute a weighted energy value of the signal. weighted using one or more residual signal upmix parameters (which may be equal to the residual signal weighting coefficient mentioned above), to determine a factor in dependence on the weighted energy value of the uncorrelated signal and the weighted energy value of the residual signal, and to obtain a weight describing the contribution of the uncorrelated signal to (at least) one of the audio output signals based on in the factor. It has been found that this procedure is well suited for efficient weight computation describing the contribution of the uncorrelated signal to one or more of the output audio signals.

In a preferred embodiment, the multi-channel audio decoder is configured to multiply the factor by a decorrelated signal upmix parameter to obtain the weight describing the contribution of the decorrelated signal to (at least) one of the audio signals. output. Using such a procedure, it is possible to consider both one or more parameters describing desired signal characteristics of the at least two output audio signals (which are described by the uncorrelated signal upmix parameter) and the relationship between the uncorrelated signal energy and the residual signal energy to determine the weight describing the contribution of the uncorrelated signal to the weighted combination. Thus, there is both the possibility of mixing (or fading) between parametric encoding (or predominantly parametric encoding) and residual encoding (or predominantly residual encoding) while still taking into account the desired characteristics of the output audio signals ( which are reflected by the uncorrelated signal upmix parameter).

In a preferred embodiment, the multi-channel audio decoder is configured to compute the unrelated signal energy weighted using the unrelated signal upmix parameters on a plurality of upmix channels and time slots to obtain the value. weighted energy of the uncorrelated signal. In this way, strong variations in the weighted energy value of the uncorrelated signal can be avoided. Thus a stable adjustment of the multi channel audio decoder is achieved.

Similarly, the multi-channel audio decoder is configured to compute residual signal energy, weighted using residual signal upmix parameters, on a plurality of upmix channels and time slots, to obtain energy value. weighted residual signal.

In this way a stable adjustment of the multichannel audio decoder is achieved as strong variations in the weighted energy value of the residual signal are avoided.

However, the reference period can be selected short enough to allow for a dynamic adjustment of the weighting.

In a preferred embodiment, the multi channel audio decoder is configured to compute the factor depending on a difference between the weighted energy value of the uncorrelated signal and the weighted energy value of the residual signal. A computation, which compares the weighted energy value of the uncorrelated signal and the weighted energy value of the residual signal, makes it possible to supplement the residual signal (or the weighted version of the residual signal) with the use (of the weighted version) of the uncorrelated signal, where The weight describing the contribution of the uncorrelated signal is adjusted to the requirements for providing at least two audio channel signals.

In a preferred embodiment, the multi-channel audio decoder is configured to compute the factor depending on a ratio of a difference between the weighted energy value of the uncorrelated signal and the weighted energy value of the residual signal, and the value of weighted energy of the uncorrelated signal. It was found that the computation of the factor in dependence on this ratio gives good particular results. Furthermore, it should be noted that the ratio describes which portion of the total energy of the uncorrelated signal (weighted using the uncorrelated signal upmix parameter) is required in the presence of the residual signal in order to achieve a good impression of hearing (or equivalently, to have substantially the same signal energy in the output audio signals as compared to the case where there is no residual signal).

In a preferred embodiment, the multi channel audio decoder is configured to determine weights that describe contributions of the decorrelated signal to two or more output audio signals. In this case, the multi channel audio decoder is configured to determine a decoupling signal contribution to a first output audio signal based on the decoupled signal weighted energy value and a first channel decoupled signal upmix parameter. Further, the multi channel audio decoder is configured to determine a decoupled signal contribution to a second output audio channel based on the decoupled signal weighted energy value and a second channel decoupled signal upmix parameter. Thus, two output audio signals can be endowed with moderate effort and good audio quality, where the differences between the two output audio signals are considered using a first channel decorrelated signal upmix parameter and a second channel uncorrelated signal upmix parameter.

In a preferred embodiment, the multi-channel audio decoder is configured to disable a mismatch signal contribution to the weighted combination if a residual energy exceeds a mismatch energy (i.e., a mismatched signal energy, or a weighted version). this). In this way it is possible to switch to pure residual coding without the use of the uncorrelated signal if the residual signal carries sufficient energy, if the residual energy exceeds the decorrelator energy.

In a preferred embodiment, the audio decoder is configured to determine, at band level, the weight describing the contribution of the uncorrelated signal to the weighted combination pending a determination in terms of bandwidth determination of a signal weighted energy value. residual. Thus, it can be flexibly decided, without additional signaling overhead, in which frequency bands a refinement of at least two output audio signals should be based (or should be predominantly based) on a parametric coding, and on which frequency bands the refinement of at least two output audio signals must be based (or must be a residual coding).

Thus, it can be flexibly decided in which frequency bands a waveform reconstruction (or at least one waveform reconstruction should be performed using (at least predominantly) the residual coding at the same time. keeps the weight of the unrelated signal comparatively low. In this way, good audio quality can be achieved by selectively applying parametric coding (which is mainly based on providing a unrelated signal) and residual coding (which is mainly based on providing a residual signal).

In a preferred embodiment, the audio decoder is configured to determine the weight describing the contribution of the uncorrelated signal in a weighted combination for each frame of the output audio signals. In this way a fine temporal resolution can be obtained which allows to flexibly switch between parametric coding (or predominantly parametric coding) and residual coding (or predominantly residual coding) between subsequent frames. In this way the audio decoding can be adjusted to the characteristics of the audio signal with a good time resolution.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments according to the invention will subsequently be described with reference to the accompanying figures, wherein

<td>Figure 1 shows a diagram of</td><td>blocks</td><td>schematic</td><td>in</td><td>one</td>

<td>multi-channel audio encoder;</td><td></td><td></td><td></td><td></td>

<td>Figure 2 shows a diagram of</td><td>blocks</td><td>schematic</td><td>in</td><td>one</td>

<td>multi channel audio decoder,</td><td colspan="2">according to a</td><td>form</td><td>in</td>

<td>realization of the invention;</td><td></td><td></td><td></td><td></td>

<td>Figure 3 shows a diagram of</td><td>blocks</td><td>schematic</td><td>in</td><td>one</td>

multi-channel audio decoder according to another embodiment of the present invention;

Figure 4 shows a flowchart of a method for providing a coded representation of a multi-channel audio signal;

Figure 5 shows a flowchart of a method for providing at least two output audio signals based on a coded representation, according to an embodiment of the invention;

Figure 6 shows a flowchart of a method for providing at least two output audio signals based on a coded representation according to another embodiment of the invention; and

Figure 7 shows a flow diagram of a decoder according to an embodiment of the present invention; and

Figure 8 shows a schematic representation of a Hybrid Residual Decoder.

DETAILED DESCRIPTION OF EMBODIMENTS

1. Multi-channel audio encoder according to Figure 1

Figure 1 shows a schematic block diagram of a multi channel audio encoder 100 for providing an encoded representation of a multi channel signal.

The multi-channel audio encoder 100 is configured to receive a multi-channel audio signal 110 and to provide, based thereon, an encoded representation 112 of the multi-channel audio signal 110. The multi-channel audio encoder 100 comprises a processor (or processing device) 120, which is configured to receive the multi channel audio signal and to obtain a downmix signal 122 based on the multi channel audio signal 110. Processor 120 is further configured to provide parameters 124 describing dependencies between channels of multi-channel audio signal 110. Further, processor 120 is configured to provide a residual signal 126. Further, multi-channel audio encoder comprises residual signal processing 130, which is configured to vary an amount of residual signal included in coded representation 112 depending on multi-channel audio signal 110.

However, it should be noted that the multi-channel audio decoder need not comprise a separate processor 120 and separate residual signal processing 130. Instead, it is sufficient if the multi-channel audio encoder is in any way configured to perform the functionality of processor 120 and residual signal processing 130.

Considering the functionality of the multi channel audio encoder 100, it can be seen that the channel signals of the multi channel audio signal 110 are typically encoded using a multi channel encoding, wherein the encoded representation

112 typically comprises (in a coded form) the downmix signal

122, the parameters

124 describing dependencies between canars of the multi-channel audio signal 110 and the residual signal 126. The downmix signal

122 For example, a combination (e.g., a combination of the channel signals of the multi-channel audio signal may be based. However, a downmix signal 122 may be provided based on a plurality of channel signals of the audio signal). Alternatively, however, two or more downmix signals may be associated with a larger number (typically greater than the number of downmix signals) of channel signals of the multi-channel audio signal 110. Parameters 124 may describe dependencies (for example, a correlation, covariance, level relationship or the like) between channels (or channel signals) of the multi-channel audio signal 110. Thus, parameters 124 serve the purpose of deriving a reconstructed version of the channel signals from the multi-channel audio signal 110 based on the downmix signal 122 on the side of an audio decoder. For this purpose, parameters 124 describe desired characteristics (e.g., individual characteristics or relative characteristics) of the channel signals of the multi-channel audio signal, so that an audio encoder using parametric decoding can reconstruct the signals. based on one or more downmix signals 122.

In addition, the multi-channel audio decoder 100 provides the residual signal 126, which typically represents signal components that, as expected or estimated from the multi-channel audio encoder, cannot be reconstructed by a audio decoder (for example, by an audio decoder that follows a certain processing rule) based on downmix signal 122 and parameters 124. Thus, the residual signal 126 may typically be considered as a refinement signal, which allows a waveform reconstruction, or at least a partial waveform reconstruction, on the side of an audio decoder.

However, the multi-channel audio encoder 100 is configured to vary a residual signal amount included in the encoded representation 112 depending on the multi-channel audio signal 110. In other words, the multi-channel audio encoder may, for example, For example, deciding on the strength (or energy) of the residual signal 126 that is included in the coded representation 112. Additionally or alternatively, the multi-channel audio encoder 100 may decide with respect to which frequency bands and / or how many frequency bands the residual signal is included in the encoded representation 112. By varying the amount of residual signal 126 included in the encoded representation 112 depending on the multi-channel audio signal (and / or depending on an available bit rate), the multichannel audio encoder 100 can flexibly determine how Accurately the channel signals of the multi-channel audio signal 110 can be reconstructed on the side of an audio decoder based on the encoded representation 112. Thus, the accuracy with which the channel signals of the multi channel audio signal 110 can be reconstructed can be adapted to the psychoacoustic relevance of different signal portions of the channel signals of the multi channel audio signal 110 (such as eg time portions, frequency portions and / or time / frequency portions). Thus, signal portions of high psychoacoustic relevance (such as tonal signal portions or signal portions comprising transient events may be encoded with particularly high resolution by including a large amount of residual signal 126 in the encoded representation.

For example, a comparatively high energy residual signal may be achieved to be included in the coded representation 112 for signal portions of high psychoacoustic relevance. Moreover, a high energy residual signal can be achieved to be included in the coded representation.

112 if downmix signal 122 comprises of poor quality, for example, if there is substantial cancellation of signal components by combining the channel signals of multi-channel audio signal 112 into downmix signal

122. In other words, the multi-channel audio decoder

100 may selectively input a larger amount of residual signal (for example, a residual signal having an energy in coded representation 112 for signal portions of multi-channel audio signal 110 so that providing a comparatively large amount of residual signal provides a Significant enhancement of rebuilt channel signals (rebuilt on the side of an audio decoder).

Thus, by varying the amount of residual signal included in the encoded representation depending on the multi-channel audio signal 110, it is possible to adapt the encoded representation 112 (for example, the residual signal 126, which is included in the encoded representation in an encoded form). 110 multi-channel audio signal, so that a good compromise between bitrate efficiency and audio quality of the rebuilt multi-channel audio signal (rebuilt on the side of an audio decoder) can be achieved.

It should be noted that multi-channel audio encoder 100 can be optionally enhanced in many different ways. For example, the multi channel audio encoder may be configured to vary a residual signal bandwidth 126 (which is included in the encoded representation) depending on the multi channel audio signal 110. Thus, the amount of residual signal included in the coded representation 112 may be adapted to the most important perceptually frequency bands.

Optionally, the multi channel audio decoder may be configured to select frequency bands for which the residual signal 126 is included in the coded representation 112 depending on the multi channel audio signal 110. In this way, coded representation 120 (more precisely, the amount of residual signal included in coded representation 112) can be adapted to the multi-channel audio signal, for example to the perceptually more important frequency bands of the multi-channel audio signal. 110

Optionally, the multi-channel audio encoder may be configured to include residual signal 126 in the encoded representation for frequency bands for which the multi-channel audio signal is tonal. In addition, the multi-channel audio encoder may be configured not to include residual signal 126 in the coded representation 112 for frequency bands where the multi-channel audio signal is non-tonal (unless otherwise specified). is satisfied that it motivates an inclusion of the residual signal in the coded representation for a specific frequency band). Thus, the residual signal may be selectively included in the coded representation for perceptually important tonal frequency bands.

Optionally, the multi-channel audio encoder 100 may be configured to selectively include the residual signal in the coded representation for time portions and / or frequency bands where downmix signal formation results in signal signal component cancellation. multichannel audio For example, the multi-channel audio encoder may be configured to detect a cancellation of signal components from the multi-channel audio signal 110 in downmix signal 122, and to enable the provision of residual signal 126 (e.g., inclusion residual signal 126 in coded representation 112) in response to the detection result. Thus, if downmix (or any other typically linear combination) of channel signals from multi-channel audio signal 110 in downmix signal 122 results in cancellation of signal components from multi-channel audio signal 112 (which may be caused, for example, by signal components of different channel srnars which are phase shifted into residual signal 126, which aids in overcoming the detrimental effect of this cancellation during reconstruction of multi-channel audio signal 110 in an audio decoder, will be included in coded representation 112. For example, residual signal 126 may be selectively included in coded representation 112 for audio bands. frequency for which there is such a cancellation.

Optionally, the multi-channel audio encoder may be configured to compute the residual signal using a linear combination of at least two channel signals of the multi-channel audio signal and depending on upmix coefficients to be used on the side. of a multi-channel audio decoder. Such computation of a residual signal is efficient and allows simple reconstruction of channel signals on the side of an audio decoder.

Optionally, the multi-channel audio encoder can be configured to encode upmix coefficients using parameter 124 which describes dependencies between channels of the multi-channel audio signal, or to derive upmix coefficients from parameters that describe dependencies between the channels of the multi-channel audio signal. Thus, parameters 124 (which may for example be intracanal level difference parameters, intracanal correlation parameters or the like) can be used for both parametric coding (coding or decoding) as well as residual signal assisted coding (coding). or decoding).

Thus, use of residual signal 126 does not result in additional signaling overload. Instead, parameters 124, which are used for parametric coding (coding / decoding) anyway, are also reused for residual coding (coding / decoding).

<td>Thus a</td><td>high efficiency</td><td>in</td><td>coding</td><td>Can be</td>

<td>achieved. Optionally, the</td><td>decoder</td><td>audio</td><td>multi channel</td><td>Can be</td>

<td>set up</td><td>for</td><td>determine from</td><td>variant mode</td><td>in time the</td>

<td>amount</td><td>in</td><td>residual signal</td><td>included in</td><td>representation</td>

<td>coded</td><td>as</td><td>use of a template</td><td>psychoacoustic.</td><td>Thus, the</td>

Coding accuracy can be adapted to psychoacoustic characteristics of the signal, which typically result in good bitrate efficiency.

However, it should be noted that the multichannel audio encoder may optionally be supplemented by any of the features or functionality described herein (both in the description and in the claims). Further, the multi-channel audio encoder may also be adapted in parallel with the audio decoder described herein to cooperate with the audio decoder.

2. Multi-channel audio decoder according to Figure 2

Figure 2 shows a schematic block diagram of a multi-channel audio decoder 200 according to an embodiment of the present invention.

The multi-channel audio decoder 200 is configured to receive a coded representation 210 and to provide, based thereon, at least two output audio signals 212, 214. The multi-channel audio decoder 200 may, for example, comprise a weighting combiner 220 which is configured to perform a weighted combination of a downmix signal 222, an uncorrelated signal 224, and a residual signal 226 to obtain ( at least one of the output signals, for example the first output audio signal 212. It should be noted herein that downmix signal 212, uncorrelated signal 224 and residual signal 226 may, for example, be derived from coded representation 210, wherein coded representation 210 may carry a coded representation of signal downmix 220 and an encoded representation of the residual signal 226. Further, the uncorrelated signal 224 may, for example, be derived from the downmix signal 222 or may be derived using additional information included in the coded representation 210. However, the uncorrelated signal may also be provided without any specificity information. 210. According to an example useful for understanding the invention, the multi-channel audio decoder 200 is also

<td>set up</td><td colspan="2">to determine a weight</td><td>what</td><td>describe</td><td>an</td>

<td>contribution</td><td>of the signal</td><td>unrelated</td><td> 224</td><td colspan="2">in combination</td>

<td>weighted in</td><td>dependency</td><td>of residual signal</td><td> 226.</td><td>For example</td><td>, O</td>

<td>decoded</td><td>r audio</td><td>multi channel 200</td><td>can</td><td>understand</td><td>one</td>

weighting determiner 230, which is configured to determine a weighting 232 that describes the contribution of the uncorrelated signal 224 in the weighted combination (for example, the contribution of the uncorrelated signal 224 to the first freckle audio signal 212) based on the residual signal 226 .

Considering the functionality of the multi channel audio decoder 200, it should be noted that the contribution of the decorrelated signal

224 in the weighted combination and, consequently for the first output audio signal 212, is flexibly adjusted (for example, with time variation residual signal dependence

226, without additional signaling overhead.

Thus, the amount of uncorrelated signal 224, which is included in the first output audio signal 212, is adapted depending on the amount of residual signal.

226 which is included in the first output audio signal 212, so that a good quality of the first output audio signal

212 be achieved.

Thus, appropriate weighting of the uncorrelated signal 224 can be obtained under any circumstances and without additional signaling overhead.

Thus, using the multi-channel audio decoder

200, good quality decoded output audio signal

212 can be achieved with moderate bitrate. A reconstruction accuracy can be flexibly adjusted by an audio encoder, wherein the audio encoder can determine an amount of residual signal 226 that is included in the encoded representation.

212 (for example, the amount of residual signal energy

226 coded representation 210, or how many frequency bands the residual signal 226 included in coded representation 210 refers to), and the multi-channel audio decoder 200 may react appropriately and adjust the weighting of the decorrelated signal

224 to correspond to the amount of residual signal 226 included in coded representation 210. Accordingly, if there is a large amount of residual signal 226 included in coded representation 210 (for example, for a specific frequency band, or for a specific time portion), weighted combination

220 may predominantly (or which provides consider residual signal

6th at the same time light weight (or none at all with the unrelated signal 224.

In contrast, if there is only a minor amount of a residual signal

226 included in the coded representation

210, weighted combination 220 may predominantly (or consider the uncorrelated signal 224, but only to a comparatively small degree (or none) the residual signal

226 in addition to the 222 downmix signal. Thus the multi-channel audio decoder

200 You can flexibly cooperate with an appropriate multi-channel audio encoder and adjust the weighted combination 220 to achieve the best possible audio quality under any circumstances (regardless of whether a smaller or larger amount of residual signal 226 is included.) coded representation 210).

It should be noted that the second output audio signal 214 may be generated in a similar manner. However, it is not necessary to apply the same mechanisms to the second output audio signal 214, for example, if there are different quality requirements with respect to the second output audio signal. According to the invention, the multi-channel audio decoder is configured to determine the weighting 232 which describes the contribution of the uncorrelated signal 224 in the weighted combination depending on the uncorrelated signal 224. In other words, the weighting 232 may depend on both signal 226 as the uncorrelated signal 224. In this way, the weighting 232 can be further adapted to an audio signal to be decoded without further signaling overhead.

As an optional enhancement, the multichannel audio decoder can be configured to obtain upmix parameters based on coded representation 212 and to determine weighting 232 which describes the contribution of the decorrelated signal to the weighted combination depending on the upmix parameters. Thus, weighting 232 may additionally depend on the upmix parameters, so that even better adaptation of weighting 232 can be achieved.

As another optional enhancement, the multi-channel audio decoder may be configured to determine the weight describing the contribution of the uncorrelated signal to the weighted combination so that the weight of the uncorrelated signal decreases with increasing residual signal energy. Thus, a mixing or fading can be performed between a decoding that is predominantly based on the decorrelated signal 224 (in addition to a downmix signal 222) and a decoding that is predominantly based on the residual signal 226 (in addition to a downmix signal 222) .

As another optional enhancement, the multi-channel audio decoder 200 may be configured to determine weighting 232 such that a maximum weight, which is determined by an uncorrelated signal upmix parameter (which may be included or derived from coded representation 210). ) is associated with the uncorrelated signal 224 if a residual signal energy 226 is zero, and such that a zero weight is associated with the uncorrelated signal 224 if a residual signal energy 226, weighted with the residual signal weighting coefficient (or a residual signal upmix parameter), is greater than or equal to an energy of the residual signal. uncorrelated signal 224, weighted with the uncorrelated signal upmix parameter. In this way, it is possible to completely mix (or fade) between a decorrelated signal based decoding 224 and a residual signal based decoding 226. If the residual signal 226 is judged to be strong enough (for example, when the weighted residual signal energy is equal to or greater than the weighted uncorrelated signal energy 224), the weighted combination may be based entirely on the residual signal 226. to refine downmix signal 222 while unrelated signal 224 is left out of consideration. In this case, a (at least partial) waveform reconstruction on the side of the multi-channel audio decoder 200 may be performed, since consideration of the decorrelated signal 224 typically avoids a particularly good waveform reconstruction while using of residual signal 226 typically allows good waveform reconstruction.

In another optional enhancement, the multi-channel audio decoder 200 may be configured to compute a weighted energy value of a correlated signal, weighted depending on one or more uncorrelated signal upmix parameters, and to compute a weighted energy value of the residual signal, weighted using one or more residual signal upmix parameters. In this case, the multi-channel audio decoder may be configured to determine a factor depending on the weighted energy value of the correlated signal and the weighted energy value of the residual signal and to obtain a weight describing the contribution of the uncorrelated signal 224 to one of the output audio signals (for example, the first output audio signal 212) based on the factor. Thus, weighting 230 can provide particularly well-matched weighting values ​​232.

In an optional enhancement, multichannel audio decoder 200 (or weighting determiner 230 thereof) may be configured to multiply the factor by the uncorrelated signal upmix parameter (which may be included in coded representation 210, or derived from coded representation 210) , to obtain the weight (or weighting value) 232 describing the contribution of the uncorrelated signal 224 to one of the output audio signals (e.g., the first output audio signal 212).

In an optional enhancement, the channel decoder (or weighting determiner 230 configured to compute the power of the multi-correlated audio signal

224, weighted using uncorrelated signal upmix parameters (which can be included in the encoded representation

210, or which may be derived from the encoded representation on a plurality of time slot upmix channels, to obtain the weighted energy value of the uncorrelated signal.

As an additional optional enhancement, multi-channel audio decoder 200 may be configured to compute residual signal energy 224, weighted using residual signal upmix parameters (which may be included in coded representation 210 or may be derived from plotted against a plurality of upmix channels and time slots to obtain the weighted energy value of the residual signal.

As another optional enhancement, the multi-channel audio decoder 200 (or its weighting determiner 232) may be configured to compute the above factor depending on a difference between the weighted energy value of the uncorrelated signal and the energy value. weighted residual signal. Such computation has been found to be an efficient solution for determining weighting values ​​232.

As an optional enhancement, the multichannel audio decoder may be configured to compute the factor depending on a ratio of a difference between the weighted energy value of the uncorrelated signal 224 and the weighted energy value of the residual signal 226, and the value of weighted energy of the uncorrelated signal 224. It has been found that such factor computation provides good results for mixing between a predominantly downmix signal decorrelation signal-based refinement 222 and predominantly residual downmix signal-based refinement of signal 222.

As an optional enhancement, the multichannel audio decoder 200 may be configured to determine weights that describe contributions of the correlated signals to two or more output audio signals, such as the first output audio signal 212 and the second signal. In this case, the multi-channel audio decoder may be configured to determine a contribution of the uncorrelated signal 224 to the first output audio signal.

212 based on the weighted energy value of the correlated signal

224 a first channel uncorrelated signal upmix parameter.

Moreover, multi-channel audio decoder can be configured to determine a decorrelated signal contribution.

224 to the second output audio signal

214 based on the weighted energy value of the uncorrelated signal 224 and a second channel uncorrelated signal upmix parameter. In other words, different uncorrelated signal upmix parameters can be used to provide the first output audio signal 212 and the second output audio signal 214. However, the same weighted energy value of the uncorrelated signal may be used to determine the contribution of the uncorrelated signal to the first output audio signal 212 and the contribution of the uncorrelated signal to the second output audio signal 214. In this way, efficient tuning is possible, however, where different characteristics of the two output audio signals 212, 214 can be considered by different uncorrelated signal upmix parameters.

As an optional enhancement, the multichannel audio decoder 200 may be configured to disable a contribution of the uncorrelated signal 224 to the weighted combination if a residual energy (e.g., a residual signal energy 226 or a residual signal weighted version 226) exceeds a uncorrelated energy (e.g., an energy of the uncorrelated signal 224 or a weighted version of the uncorrelated signal 224).

As an additional optional enhancement, the audio decoder may be configured to determine, in terms of bandwidth, weighting 232 which describes a contribution of the uncorrelated signal 224 in the weighted combination depending on a determination, in terms of bandwidth, of a value of. weighted energy of the residual signal. In this way, fine tuning of the multi-channel audio decoder 200 to the signals to be decoded can be performed.

In another optional enhancement, the decoder being configured to determine the weight that the contribution of the decorrelated signal to audio may describe a weighted combination for each

So a good

In an enhancement frame weight value of the output audio signal 212, 214.

temporal resolution can be achieved.

additionally optional, the determination of the

232 can be performed according to some of the equations provided below.

Furthermore, it should be noted that the multi-channel audio decoder 200 may be supplemented by any of the features or functionality described herein, also in relation to other embodiments.

3 Multi-channel audio decoder according to Figure 3

Figure 3 shows a schematic block diagram of a multi-channel audio decoder 300 according to an embodiment of the invention. The multi-channel audio decoder 300 is configured to receive a coded representation 310 and to provide, based thereon, two or more output audio signals 312, 314. Coded representation 310 may, for example, comprise a coded representation of a downmix signal, a coded representation of one or more spatial parameters, and a coded representation of a residual signal. The multi-channel audio decoder 300 is configured to receive (at least) one of the output audio signals, for example a first output audio signal 312 and / or a second output audio signal 314, based on coded representation of the downmix signal, in a plurality of coded spatial parameters in a coded representation of the residual signal. According to an example useful for understanding the invention, the multi channel audio decoder

300 is configured to mix between a parametric encoding and a residual encoding depending on the residual signal (which is encoded in the representation

In other words, multi-channel audio decoder 300 can mix between a decoding mode in which providing the output audio signals

312, 314 is performed based on the downmix signal and using spatial parameters that describe a desired relationship between the output audio signals 312, 314 (e.g., a desired intercanal level difference or a desired intercanal correlation of the signals). output audio 312, decoding mode in which output audio signals 312,

314 are reconstructed based on the downmix signal using the residual signal. Thus, the intensity (e.g., energy) of the residual signal, which is included in the coded representation 310, can determine whether decoding is mainly (or exclusively) based on spatial parameters (in addition to the downmix signal) or if decoding is mainly (or exclusively) based on the residual signal (in addition to the downmix signal), or if an intermediate state is considered where both spatial parameters and residual signal affect downmix signal refinement to derive the output audio signals 312, 314 from the downmix signal.

Moreover, the multi-channel audio decoder 300 allows decoding that is well suited to current audio content without high signaling overhead by mixing parametric encoding, (where typically a comparatively high weight is provided to a signal). uncorrelated when output audio signals 312, 314 are provided and a residual coding (where typically a comparatively low weight is given to a unrelated signal) depending on the residual signal.

Further, it should be noted that the multi-channel audio decoder 300 is based on considerations similar to the multi-channel audio decoder 200 and that optional enhancements described above with respect to the multi-channel audio decoder 200 may also be applied to the 300 multi-channel audio decoder.

4 Method for providing a coded representation of a multi-channel audio signal according to Figure 4

Figure 4 shows a flowchart of a method 400 for providing a coded representation of a multi-channel audio signal.

Method 400 comprises a step 410 of obtaining a downmix signal based on a multi-channel audio signal. Method 400 also comprises a step 420 of providing parameters describing dependencies between the channels of the multi-channel audio signal. For example, inter-channel level difference parameters and / or inter-channel correlation parameters (or covariance parameters) may be provided, which describe dependencies between channels of the multichannel audio signal. Method 400 also comprises a step 430 of providing a residual signal. Further, the method comprises a step 440 of varying an amount of residual signal included in the encoded representation in dependence on the multi-channel audio signal.

It should be noted that method 400 is based on the same considerations as audio coder 100 according to Figure 1. Further, method 400 may be supplemented by any of the features and functionality described herein with respect to the apparatus of invention.

5 Method for providing at least two output audio signals based on a coded representation according to Figure 5.

Figure 5 shows a flow chart of a method 500 for providing at least two output audio signals based on a coded representation. Method 500 comprises determining 510 a weight describing a contribution of a unrelated signal in a weighted combination dependent on a residual signal. Method 500 also comprises performing a weighted combination of a downmix signal, a unrelated signal and a residual signal 520 to obtain one of the output audio signals.

It should be noted that method 500 may be supplemented by any of the features and functionality described herein in relation to the apparatus of the invention.

6 Method for providing at least two output audio signals based on a coded representation according to Figure 6.

Figure 6 shows a flowchart of a method 600 for providing at least two output audio signals based on a coded representation. Method 600 comprises obtaining 610 one

<td>of the signs</td><td>in</td><td>audio</td><td>output with</td><td>base</td><td>in</td><td>representation</td>

<td>coded</td><td>in</td><td colspan="2">a downmix signal,</td><td colspan="2">of a</td><td>plurality of</td>

<td>parameters</td><td colspan="2">space</td><td>coded and</td><td>in</td><td>an</td><td>representation</td>

<td>coded</td><td>in</td><td>a signal</td><td colspan="2">residual. Get 610</td><td>one</td><td>of the signs of</td>

output audio comprises performing

620 a mixture between a parametric coding and a residual coding depending on the residual signal.

It should be noted that method 600 may be supplemented by any of the features and functionality described herein with respect to the apparatus of the invention.

7 Additional Embodiments

In the following, some general considerations and some additional embodiments will be described.

7.1 General Considerations

Embodiments according to the invention are based on the idea that instead of using a fixed residual bandwidth, a decoder (e.g., a multi-channel audio decoder) detects the amount of residual signal transmitted by measuring their band-level energy for each frame (or generally at least for a plurality of frequency bands and / or for a plurality of time portions). Depending on the transmitted spatial parameters, a decorrelated output is added when residual energy is absent to achieve a required (or desired) amount of decorrelation and output energy. This allows for variable residual bandwidth as well as bandwidth style residual signals. For example, you can only use residual coding for tonal bands. To be able to use simplified downmix for parametric coding as well as waveform preservation coding (which is also referred to as residual coding), a residual signal for simplified downmix is ​​defined herein.

7.2 Residual Signal Calculation for Simplified Downmix

In the following, some considerations regarding residual signal calculation and channel signal construction of a multi-channel audio signal will be described.

In unified voice and audio coding (USAC), there is no residual signal defined when a so-called simplified downmix is ​​used. Thus, no partial mode waveform preservation coding is possible. However, a method for calculating a residual signal for the so-called simplified downmix will be described below.

Simplified downmix weights d₃, d2 are calculated by scale factor band, whereas parametric upmix coefficients u_di u_d2 are calculated by parameter band. Thus, coefficients w_rlf w_r2, to calculate the residual signal cannot be computed directly from the spatial parameters (as is the case for a classic surround MPEG), but may need to be determined by scale factor band from the downmix and upmix coefficients.

With L, R being the input channels and D being the downmix channel, a residual signal res must satisfy the following properties:

D dg. vd * .R

H - iy)!) -J-? F_f..2rí? S (1) (2) (2)

This is achieved by calculating the residual as using downmix weights.

<td></td><td colspan="2">1/1 - · * - X 1/1 WO- q (- X</td><td colspan="2">«R.2 J^;r.2 ./</td><td> (5) (6)</td>

<td>The</td><td>coefficients</td><td>from upmix</td><td>residuals u_ri love</td><td>U_r,2</td><td>used by</td>

Decoders are preferably chosen to ensure robust decoding. Since simplified downmix has asymmetric properties (as opposed to fixed weight MPEG Surround) an upmix depending on spatial parameters is applied, for example, using the following upmix coefficients:

In Í In · · ·· (&lt;

«, $ S» - lúax Ύί (2)

Another option is to set the residual upmix coefficients to be orthogonal to the downmix signal upmix coefficients so that:

<img file="PT3025331T_D0001.tif" />

In other words, an audio decoder can obtain downmix signal D using a linear combination of a left channel signal L (first channel signal) and a right channel signal R (second channel signal). Similarly, the residual signal res is obtained using a linear combination of the

<td>channel</td><td>left L and the channel signal</td><td>right</td><td>R</td><td>(or,</td><td>usually,</td>

<td>on one</td><td>first channel signal and one</td><td>second</td><td colspan="2">signal</td><td>channel</td>

<td>signal</td><td>channel audio).</td><td></td><td></td><td></td><td></td>

<td>Can</td><td>take place, for example, in</td><td colspan="2">Equations</td><td> (5)</td><td>and (6) the</td>

<td colspan="2">downmix weights w_r, iew_r,₂ for</td><td>obtain the</td><td colspan="2">signal</td><td>residual res</td>

can be obtained when simplified downmix weights d₂d₂, the parametric upmix coefficients u_4jthis_4i2 and the residual upmix coefficients u_rthis_r, 2 are determined. Moreover, it can be seen that a_rthis_r,₂ can be derived from Ud, ie Ud,₂ using equations (7) and (8) or equation (9). The simplified downmix weights d₂ ed_2f as well as the parametric upmix coefficients u ^ ie uj_i2 can be obtained in the usual way.

7.3 Coding Process

Here are some details regarding the encoding process. Encoding may, for example, be performed by multi-channel audio encoder 100 or any other suitable computer programs or means.

Preferably, the amount of a residual that is transmitted is determined by a psychoacoustic model of the encoder (e.g. multi-channel audio encoder) depending on the audio signal (e.g. depending on the channel signals of the multi-channel audio signal). channel 110) and an available bit rate. The transmitted residual signal may, for example, be used for partial waveform preservation or to prevent signal cancellation caused by the downmix method used (for example, the downmix method described by equation (1) above).

7.3.1 Partial Waveform Preservation

The following describes how partial waveform preservation can be achieved. For example, the calculated residual (e.g. the residuals according to equation (4)) is transmitted in a full band or limited band mode to provide partial waveform preservation within the residual bandwidth. Residual parts, which are detected as perceptually irrelevant by the psychoacoustic model can, for example, be quantized to zero (for example, by providing coded representation 112 based on residual signal 126). This includes, but is not limited to, reducing the transmitted residual bandwidth at run time (which can be considered the same as varying the amount of residual signal that is included in the encoded representation). This system may also allow bandwidth-style deletion of residual signal parts, as the missing signal energy will be rebuilt by the decoder (e.g., the multi-channel audio decoder 200 or the multi-channel audio decoder 300). Thus, for example, residual coding can only be applied to tone signal components, preserving their phase ratios, while background noise can be parametrically coded to reduce the residual bitrate. In other words, residual signal 126 can only be included in coded representation 112 (e.g., by residual signal processing 130) for frequency bands and / or time portions for which multi-channel audio signal 110 (or at least least one of the channel signals of the multi channel audio signal 110) is found to be tonal. In contrast, residual signal 126 may not be included in coded representation 112 for frequency bands and / or time portions for which the multi-channel audio signal 110 (or at least one or more channel signals of the multi-channel audio signal). -channel 110) is identified to be similar to noise. Thus, an amount of residual signal included in the encoded representation is varied depending on the multi-channel audio signal.

7.3.2 Downmix signal cancellation prevention

In the following, it will be described how downmix signal cancellation can be prevented (or compensated).

For low bitrate applications, parametric coding (which relies predominantly or exclusively on parameters 124 describing channel dependencies of the multichannel audio signal) rather than waveform preservation coding (which, for example, is based on predominantly on residual signal 126, in addition to downmix signal 122) is applied. In the present document, residual signal 126 is only used to compensate for signal cancellations in downmix 122 to minimize the use of residual bits. As long as no signal cancellation in downmix 122 is detected, the system runs in parametric mode using decorrelators (on the audio decoder side). When signal cancellations occur, for example, for phased tonal signals, a residual signal 126 is transmitted to the affected signal parts (e.g. frequency bands and / or time portions). In this way the signal energy can be restored by the decoder.

7.4 Decoding Process

7.4.1 Overview

In the decoder (e.g., multi-channel audio decoder 200 or multi-channel audio decoder 300) transmitted downmix and residual signals (e.g. downmix signal 222 or residual signal 226) are decoded by a decoder MPEG surround decoder in conjunction with the

Decoded MPEG surround. The residual upmix coefficients for the downmix of

Classic MPS are unchanged, and residual upmix coefficient for simplified downmix defined in equations

Additionally, the decoder outputs and their weighting coefficients are calculated, as for parametric decoding.

The residual signal and the slider outputs are weighted and both are mixed with the output signal. Therefore, the weighting factors are determined by measuring the residual signal and decorrelator energies.

In other words, residual upmix factors (or coefficients) can be determined by measuring the residual and uncorrelated signal energies.

For example, downmix signal 222 is provided based on coded representation 210, and uncorrelated signal 224 is derived from downmix signal 222 or generated based on parameters included in coded representation 210 (or otherwise).

Residual upmix coefficients can, for example, be derived from parametric upmix coefficients

Ud, l θ Ud, 2 according to equations (7) and (8) by the decoder, where the parametric upmix coefficients ua, i

Ud, 2 may be obtained based on coded representation 210, for example, directly or by deriving them from spatial data included in coded representation 210 (for example, from intercanal correlation coefficients and intercanal level difference coefficients, or from correlation coefficients

The upmix coefficients for the decorrelator output (or outputs) can be obtained as for conventional MPEG surround decoding. However, the weighting factors for weighting the de-correlator output (or de-correlator outputs) may be determined on the basis of residual signal energies (and possibly also on the signal energies or de-correlator signals) so that a weight that describes a contribution of the uncorrelated signal to the weighted combination to be determined in dependence on the residual signal.

7.4.2 Example Implementation

In the following, an exemplary implementation will be described with reference to Figure 7. However, it should be noted that the concept described herein can also be applied to multi-channel audio decoders 200 or 300 according to the Figures. 2 and 3.

Figure 7 shows a schematic block diagram (or flow diagram) of a decoder (e.g., a multi-channel audio decoder). The decoder according to Figure 7 is designated with 700 in its entirety. The decoder 700 is configured to receive a bit stream 710 and to provide based thereon a first output channel signal 712 and a second output channel signal 714. The decoder 700 comprises a core decoder 720 which is configured to receive bit stream 710 and to provide, based thereon, a downmix signal 722, a residual signal

724

726.

splatter the

and data

For example,

<td>decoder</td><td>in</td><td>core</td><td> 720</td><td>can provide,</td><td>as the sign</td><td>in</td>

<td>downmix one</td><td colspan="3">representation</td><td>domain name</td><td>time or</td><td>an</td>

<td>representation</td><td>in</td><td>domain</td><td>in</td><td colspan="2">transformed (for example,</td><td>an</td>

<td>representation</td><td>in</td><td>domain</td><td>in</td><td>frequency, one</td><td>representation</td><td>in</td>

<td colspan="2">MDCT domain,</td><td colspan="3">a domain representation</td><td colspan="2">QMF) of the signal</td>

Similarly, the core decoder 720 may provide either a time domain representation or a transform domain representation of the residual signal 724, which is represented by bit stream 710. Further, core decoder 720 may provide one or more spatial parameters 726, such as, for example, one or more intercanal correlation parameters, intercanal level difference parameters, or the like.

The decoder 700 also comprises a decorrelator

730, which is configured to provide an uncorrelated signal 732 based on the downmix signal 722. Any of the known uncorrelation concepts may be used by the decorrelator 730. Further, the decoder 700 also comprises an upmix coefficient calculator 740 which is configured to receive spatial data 726 and to provide upmix parameters (for example, upmix parameters Udmx,!, Udmx ^, Ud_ecFurther, the decoder 700 comprises an upmixer 750 which is configured to apply the upmix 742 parameters (also referred to as upmix coefficients) which are provided by the upmix coefficient calculator 740 based on spatial data. 726. For example, upmixer 750 can scale downmix signal 722 using two downmix signal upmix coefficients (for example, Udmx, i, u ^ x ^) to obtain two versions submitted to upmix 752, 754 of downmix signal 722.

configured to apply

Moreover, the upmixer 750 is also one or more upmix parameters (for example, two upmix parameters) to the unrelated signal.

732 provided by the 730 de-correlator, for a first upmix version

756 and a second submitted upmix (scaled) version of the uncorrelated signal 732.

What's more, the upmixer

750 is configured to apply one or more upmix coefficients (for example, two upmix coefficients) to residual signal 724, to obtain a first upmixed version 760 and a second upmixed version 762 of the residual signal 724.

The decoder

700 also comprises a weighting calculator 770 which is configured to measure the energies of the up-scaled versions 756, 758 of the decelated signal 752 and of the upmixed version 760, 762 of the residual signal 724. Further, weighting calculator 770 is configured to provide one or more weighting values ​​772 to a weighting 780. Weight 780 is configured to obtain a first upmixed and weighted version 782 of the mismatched signal 732, a second upmixed and weighted version 784 of the mismatched signal 732, a first upmixed and weighted 786 version of the residual signal 724 and a second upmixed and weighted 788 version of the residual signal 724 using one or more 772 weighting values ​​provided by the 770 weighting calculator . The decoder also comprises a first adder 790 which is configured to add the first upmixed version 752 of the downmix signal 720, the first upmixed and weighted version 782 of the unrelated signal 732, and the first version upmixed and weighted 786 of residual signal 724 to obtain the first output channel signal 712. Further, the decoder comprises a second adder 792 which is configured to add the second upmix 754 version of the downmix signal 720, the second upmix (weighted) and weighted version 784 of the decorrelated signal 732, and the second submitted version upmix 788 of the residual signal 724 to obtain the second output channel signal 714.

However, it should be noted that it is not necessary for the weight 780 to weigh all signals 756, 758, 760, 762. For example, in some embodiments, it may be sufficient to weight only signals 756, 758 at the same time. wherein signals 760, 762 are left unaffected (so that effectively signals 760, 762 are directly applied to adders 790, 792). Alternatively, however, the weighting of residual signals 760, 762 may be varied over time. For example, residual signals may be faded at the beginning or faded at the end. For example, the weighting (or weighting factors) of the uncorrelated signals may be smoothed over time, and the residual signals may be faded at the beginning or faded at the corresponding end.

Further, it should be noted that the weighting, which is performed by the 780 weighting, and the upmix, which is applied by the upmixer 750, can also be performed as a combined operation, where the weighting can be performed directly with the use of the uncorrelated signal 732 and the residual signal 724.

Here are some additional details regarding the functionality of the decoder 700.

A combined mode of parametric and residual coding may, for example, be signaled in a semi-backward compatible manner, for example by signaling the residual bandwidth of a parameter band in the bit stream. In this way, a legacy decoder will still pass and decode the bitstream by switching to parametric decoding above the first parameter band. Legacy bit streams using a residual bandwidth of one would not contain residual energy above the first parameter band, which leads to a parametric decoding in the proposed new decoder. However, within a 3D audio codec system, combined parametric and residual encoding can be used in conjunction with other core decoder tools as a quad channel element, which enables the decoder to explicitly detect legacy bit streams and decode them in the regular band-limited residual encoding mode. An effective residual bandwidth is preferably not explicitly signaled as it is determined by the decoder at run time. The calculation of upmix coefficients is set to the parametric mode instead of a residual coding mode. The energies of the weighted decorrelator output E_dec and residual signal

<td>weighted E_res</td><td>are calculated by the band</td><td>hybrid hb</td><td>in all</td>

<td>intervals of</td><td>ts time and upmix channels</td><td>ch for each</td><td>frame:</td>

<td></td><td>..... ch ts</td><td>(hb.is.chjy</td><td> (10)</td>

<td></td><td></td><td>hb. ts. vh. hi</td><td> (11)</td>

<td>Here u_dec</td><td>designates a parameter</td><td>from upmix</td><td>signal</td>

correlated to a frequency band hb, to a y

ts and for an upmix ch channel designates a y

sum of upmix channels, and designates a sum of time intervals. x_inc designates a value (for example, a complex transform domain value) of the uncorrelated signal for frequency band hb, time slot ts and upmix channel ch.

Residual signal (e.g., upmix 760 residual signal or upmix 762 residual signal) is added to the output channels (e.g. output channels 712, 714) with a weight of one. The decorrelator signal (eg the upmix 756 de-correlator signal or the upmix 758 de-correlator signal) can be weighted with an r factor (eg by weight 780) which is calculated as / | - Á_{ff; s}(hb) i.

V ΐ í (13) where E_dec(hb) represents a weighted energy value of the uncorrelated signal x_dec for a frequency band hb, and where E_res (hb) represents a weighted energy value of the residual signal x_res for a frequency band hb.

If no residual (for example, no residual signal 724) has been transmitted, for example if E_res = 0, r (the factor that can be applied by weight 780, and which can be considered as a weight value 772) becomes 1, which is the equivalent of a purely parametric decoding. If the residual energy (eg the energy of the upmix 760 residual signal and / or the upmix 762 residual signal) exceeds the energy of the decorrelator (for example, the energy of the upmix 756 decorrelated signal or the uncorrelated signal upmix 758), for example, if

AND_res > E_dec, the factor r can be set to zero, thus disabling the decoupler enabling partially the waveform preservation decoding (which can be considered as residual encoding).

In the upmix process, the weighted decoupler output (eg signals

782 and 784) and the residual signal (e.g., or signals 760, 762) are both added to the output channels (e.g.

In conclusion, this leads to an array-upmix rule

BB where chi represents one or more time domain samples or transform domain samples of a first output audio signal, where ch2 represents one or more time domain samples or one second transform domain samples output audio signal, where Xdm_x represents one or more time domain samples or downmix signal transform domain samples, where x_dec represents one or more time domain samples or non-correlated signal transform domain samples, where x_resrepresents one or more time domain samples or residual domain transform domain samples, where u ^ i represents a downmix signal upmix parameter for the first output audio signal, where u ^ x ^ represents a downmix signal upmix parameter for the second output audio signal, where u ^ i represents a decorrelated signal upmix parameter for the first output audio signal, wherein Ua_hike2 represents a decorrelated signal upmix parameter for the second output audio signal, where max represents a maximum operator, and r represents a factor describing a weighting of the decorrelated signal depending on the residual signal.

The upmix coefficients υ ^ x, j, Udmx ^ z Ud_eCfin, out_eCf2 are calculated as for the two-one-two (2-1-2) MPS parametric mode. For details, reference is made to the above mentioned standard of the MPEG surround concept.

In summary, an embodiment according to the invention provides a concept for providing output channel signals based on a downmix signal, a residual signal, and spatial data, wherein a de-correlated signal weight is flexibly adjusted without any significant signaling overhead.

7.5 Implementation Alternatives

While 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. Similarly, 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 performed by (or using) a hardware apparatus, such as a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, some or more of the most important steps of the method may be performed by such apparatus.

The encoded audio signal of the invention may be stored on a digital storage medium or may be transmitted on a transmission medium such as a wireless transmission medium or a wired transmission medium such as the Internet.

Depending on certain implementation requirements, embodiments of the invention may be implemented in hardware or software. The implementation can be accomplished 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. has electronically readable control signals stored therein which cooperate (or have the ability to cooperate) with a programmable computer system so that the method thereof is performed.

<td>Therefore, the means of</td><td>storage</td><td>digital can be</td><td colspan="2">readable by</td>

<td>computer.</td><td></td><td></td><td></td><td></td>

<td>Some ways of</td><td>achievement</td><td>according</td><td>The</td><td>invention</td>

<td colspan="2">comprise a data bearer</td><td>that has signs</td><td>in</td><td>control</td>

electronically readable, capable of cooperating with a programmable computer system, so that one of the methods described herein is performed.

Generally, embodiments of the present invention may be implemented as a computer program product with a program code, the program code being operative to perform one of the methods when the computer program product is executed on a computer. The program code may, for example, be stored in a machine readable carrier.

Other embodiments comprise the computer program for performing one of the methods described herein stored in a machine readable carrier.

In other words, one embodiment of the method of the invention is therefore a computer program having a program code for performing one of the methods described herein when the computer program is executed on a computer.

A further embodiment of the methods of the invention is therefore a data bearer (or a digital storage medium, or a computer readable medium) comprising, recorded therein, the computer program for performing one of the methods described herein. document.

data bearer, digital storage medium or recorded medium is typically tangible and / or non-transient.

A further embodiment of the method of the invention is therefore a data stream or signal sequence representing computer program for performing one of the methods described herein. The data stream or signal sequence may, for example, be configured to be transferred over a data communication connection, for example over the Internet.

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

A further embodiment comprises a computer having the computer program installed therein to perform one of the methods described herein.

A further embodiment according to the invention comprises an apparatus or system configured to transfer (e.g., electronically or optically) a computer program to perform one of the methods described herein to a receiver. The receiver may, for example, be a computer, mobile device, memory device or the like. 0 The apparatus or system may, for example, comprise a file server for transferring the computer program to the receiver.

In some embodiments, a programmable logic device (e.g., a field programmable gate array) may be used to realize some or all of the functionality of the methods described herein. In some embodiments, a field programmable gate arrangement may cooperate with a microprocessor to perform one of the methods described herein. Generally, the methods are preferably performed by any hardware apparatus.

The embodiments described above are illustrative only for the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. They are therefore intended to be limited only by the scope of the appended patent claims and not by the specific details set forth by way of description and explanation of embodiments herein.

7.6 Additional Embodiment

In the following, another embodiment according to the invention will be described with reference to Figure 8, which shows a schematic block diagram of a so-called Hybrid Residual Decoder.

Hybrid Residual Decoder 800 according to Figure 8 is very similar to decoder 700 according to Figure 7, so that reference is made to the above explanations. However, in Hybrid Residual Decoder 800, additional weighting (in addition to applying the upmix parameters) is only applied to upmix decorrelated signals (corresponding to signals 756, 758 in decoder 700), but not to submitted residual signals. to upmix (which correspond to signals 760, 762 in decoder 700). Thus, the weight in the Hybrid Residual Decoder 800 is somewhat simpler than the weight in the decoder 700, but is in accordance, for example, with the weighting according to equation (14).

In the following, the combined Residual and Parametric Decoding (Hybrid Residual Encoding) according to Figure 8 will be explained in some more detail.

However, first, an overview will be provided.

In addition to the use of deconelator-based mono to stereo upmix or residual coding as described in ISO / IEC 23003-3, sub-item 7.11.1, Hybrid Residual Coding allows a combination of both signal-dependent modes. The residual signal and the correlator output are mixed together using time and frequency dependent weighting factors depending on the signal energies and spatial parameters as illustrated in Figure 8.

Next, the decoding process will be described.

Hybrid Residual Encoding mode is indicated by the bsResidualCoding == 1 and bsResidualBands == 1 syntax elements in Mps212Config (). In other words, the use of Hybrid Residual coding can be signaled using a bit stream element of the coded representation. The calculation of the mixing matrix M2 is performed as if bsResidualCoding == 0, following the calculation in ISO / IEC 23003-3, subclause 7.11.2.3. THE

R ^lm matrix ² for the decorrelator-based part is defined as

R l, m

<td>tt] yl, minil_there</td><td></td>

<td>j. OTT</td><td>j. OTT</td>

The upmix process is divided into Downmix, decorrelator and residual output. Downmix submitted to upmix u ^ x is calculated using:

H11X 0

H21X 0

The output of the correlator submitted to upmix ⁱⁿin_W is calculated using:

residual signal subjected to upmix ⁱⁿre_s is calculated using:

1, m

2. res

<td>O</td><td></td><td></td><td>O</td><td>max {0.5, '</td>

<td> 0</td><td>RES _</td><td></td><td> 0</td><td>-max {0.5, K21X}</td>

The residual signal energies subjected to upmix E_res and the uncorrelator output submitted to upmix Ed_ec are calculated by hybrid band as the sum of both output channels ch and all time intervals ts and a frame such as:

^AND res = ΣS ch ts ^AND dec = Σ Σ ||^Udec, tS) [ch ts

The upmixed correlator output is weighted using a weighting factor rd_ec calculated for each hybrid band per frame as:

I

1.......

if Σ, ...:> £._;..

if <s> / j where ε is a small number to avoid division by zero (for example, ε = le-9, or 0 <s <= le-5). However, in some embodiments, ε may be set to zero (replacing E_res < ^e by θ).

All three upmix signals are added to form the decoded output signal.

8 Conclusions

In conclusion, embodiments according to the invention produce a combined parametric and residual coding.

The present invention provides a method for a parametric and residual coding signal dependent combination for joint stereo coding, which is based on the USAC unified stereo tool. Instead of using a fixed residual bandwidth, the amount of residual transmitted is determined as signal dependent by an encoder, time and frequency variant. On the decoder side, the required amount of decorrelation between the output channels is generated by mixing the residual signal and the decorrelator output. Thus, a corresponding encoding / decoding system is capable of mixing between fully parametric encoding and residual waveform preservation encoding during execution, depending on the encoded signal.

Embodiments according to the invention outperform conventional solutions. For example, in USAC, a two-one-two (2-1-2) MPEG surround system is used for parametric or unified stereo encoding, transmitting the full bandwidth or bandwidth residual signal for preservation. of partial waveform. If a band-limited residual is transmitted, the parametric upmix using decorrelators is applied above the residual bandwidth. The disadvantage of this method is that the residual bandwidth is set to a fixed value at encoder initialization.

In contrast, embodiments according to the invention allow for signal dependent residual bandwidth adaptation or switching to parametric coding. Furthermore, if the downmix process in parametric coding mode produces signal cancellations for poorly conditioned phase relations, embodiments according to the invention allow reconstructing the missing signal parts (e.g., by providing an appropriate residual signal). It should be noted that the simplified downmix method produces fewer signal cancellations than the classic downmix MPS for parametric coding. However, although conventional simplified downmix cannot be used for partial waveform preservation, since no residual signal is defined in USAC, embodiments according to the invention allow for waveform reconstruction (e.g. , a selective partial waveform reconstruction for signal portions where partial waveform reconstruction appears to be important).

Still further, the embodiments according to the invention produce an apparatus, method or computer program for audio decoding as claimed in the claims.

References cited in description

The list of references cited by the proposer is for the reader's convenience only. It is not part of the European patent document. Despite all the care taken in compiling the references, errors or omissions cannot be excluded and the EPO refuses any responsibility in this regard.

Patent documents cited in description