EP2080411B1 - Device and method for generating a number of loudspeaker signals for a loudspeaker array which defines a reproduction area - Google Patents

Abstract

An apparatus for generating a number of loudspeaker signals for a loudspeaker array defining a reproduction space includes a prestage configured to generate a plurality of output audio signals while using one or more audio signals associated with one or more virtual positions, each output audio signal being associated to a loudspeaker position such that the plurality of output audio signals together replicate a reproduction of the input audio signal(s) at the virtual position(s), and a number of output audio signals being smaller than a number of loudspeaker signals. The apparatus further includes a main stage configured to obtain the plurality of output audio signals and further to obtain, as a virtual position for each output audio signal, the loudspeaker positions, and to generate the number of loudspeaker signals for the loudspeaker array such that the loudspeaker positions are replicated as a virtual sources by the loudspeaker array.

Description

The present invention relates to the reproduction of spatial audio signals, such as occur in the playback of film material, concerts or in the field of computer and video games.

In the field of spatial audio transmission in the prior art, several methods are known, including, for example, the wave field synthesis, the basic idea is based on the Huygen principle, according to which every point that is detected by a wave is the starting point of an elementary wave, which is spherical or spreads circularly. Wavefield synthesis is applied in acoustics based on a large number of loudspeakers arranged side by side, a so-called loudspeaker array, and is in principle able to emulate any form of incoming wavefront. In the simplest case, a single point source to be reproduced and a linear arrangement of the loudspeakers, the audio signals of each loudspeaker can be filtered with a time delay and amplitude scaling so that a corresponding spatial impression results for a listener, with the radiated sound fields of the individual loudspeakers correspondingly overlap. If several sound sources are available, the contribution to each loudspeaker is calculated separately for each source and the resulting signals are added together. If the sources to be reproduced are located in a room with reflective walls, it may be possible to compensate for reflections via corresponding filters with the help of the loudspeaker array.

The effort involved in calculating a wave field synthesis depends heavily on the number of sound sources to be reproduced, the reflection characteristics of a playback room, and the number of speakers. The possibilities of wave field synthesis can be better exploited the larger the speaker arrays are, ie. H. the more individual speakers are provided. The disadvantage here, however, that the required computing power increases with the number of individual speakers used. For each virtual sound source, i. To be reproduced sound source, a corresponding signal must be calculated and transmitted for each speaker of the speaker array. Particularly in the case of moving virtual sources, the arithmetic wall rises immensely, so that conventional systems very quickly reach their limits by displaying moving sound waves, the limiting factor being the computing power.

Another known technique for spatial sound field reproduction is Ambisonic. This technique is based on a harmonic decomposition of the acoustic field along a spherical surface (3-D) or along a circumference (2-D). During playback, a finite number of these harmonic components are used to reproduce the original sound field at a point, the listening point. Depending on the number of harmonic components used (called order), the spatial extent of the area of optimal reconstruction of the sound field increases. In the simplest reasonable case (1st order), a sound information is encoded into four channels, which is also known under the synonym Ambisonic B format. A channel contains a mono signal of the sound information. The three other channels contain the spatial components of the three spatial dimensions. These three signals are based on a harmonic decomposition of the acoustic field along a spherical surface and reflect the instantaneous pressure distribution of the sound waves. This case is also the most commercially viable case. Because the four signals originally as a competitor to Quadrofonie on record had to find space. Currently working on a specification that uses the medium of DVD and therefore allows more channels.

Ambisonic allows a spatial audio signal in the described four channels to disassemble, and reassemble accordingly. The signals refer to a reference point, which is arranged in the middle of a sphere, on the surface of which the corresponding loudspeakers are located. The representation of spatial audio signals according to the Ambisonic method thus offer a less complex possibility to store and reproduce spatial signals. A disadvantage of this technology, however, is that the spatial resolution and thus the achievable impression of a room sound are limited.

With increasing ambisonic order, it is possible to achieve qualitatively similar results as with WFS. However, this increases the complexity and there is no microphone that has the directional characteristic of these higher harmonics. Sophisticated mic arrays must be used here

WFS reconstructs within a volume (or area) in a quality that depends on the effort implemented (e.g., LS distance).

Although Ambisonic reconstructs exactly, but starting from one point and only for very high orders on a surface as large as WFS.

Both methods have a common theoretical basis, holophony.

The signals refer to a reference point in which a listener is ideally located, what the supply a larger area, such as a cinema or a concert hall accordingly difficult.

Furthermore, it is a prerequisite that both the playback speakers with respect to the listening point and the virtual sound objects with respect to the playback speakers are located at a sufficiently distant distance, so that in any case even wavefronts can be assumed.

Furthermore, other methods for displaying spatial sound sources are known from technology. For example, DTS (Digital Theater System) is a multi-channel digital surround sound format.

Methods such as DTS, Dolby Surround, can also be considered as encoding formats. This makes it possible to use audio signals suitable for 5.1 reproduction on e.g. save a DVD.

It is used both in movie theaters and on data carriers, such as DVDs. The reproduction ideally takes place via circularly arranged loudspeakers, in the middle of which there is a reproduction room that is more favorable for the spatial reproduction of sound, which is also called "sweet area". Another group of spatial sound signals is the Dolby Digital signals, which are available in several variants. Apart from the wave field synthesis, many audio formats have the disadvantage that only a very limited spatial resolution and thus a limited spatial sound effect can be achieved. Although the wave field synthesis itself provides the spatial resolution, but this is just in the case of multiple moving virtual sound sources due to limited computing power can not be achieved if z. For example, for consumer applications, cost arguments also play a role with regard to the available computing power. Furthermore, the variable delay values of a moving audio source give rise to Doppler artifacts. Wave field synthesis is dependent from the computational effort, which in turn depends on the number of virtual audio sources, the number of rendering channels, the source movements, the filtering method, the delay interpolation method and so on.

Regarding the signal processing of ambisonic surround signals, Jerome Daniel, "Further Study of Sound Field Coding with Higher Order Ambisonics" presented at the AES 116th Convention, Berlin 2004 provides a good overview. An assessment of the quality of the sound field reproduction by ambisonics can in Martin Dewhirst, Slawomir Zielinski, Philip Jackson, Francis Rumsey: "Objective Assessment of Spatial Localization Attributes of surround sound reproduction system", presented at the AES 118 ^th Convention, Barcelona found of 2005. Alois Sontacchi, Robert Höldrich, "Further Investigations on 3D Sound Fields Using Distance Coding", presented at the Proceedings of the COST G-6 Conference on Digital Audio Effects, Limerick 2001 deals with the storage of spatial audio signals. The WO 2005/015954 A2 and the WO 02/085068 deal with ambisonic signals, and describe the spatial coding with the associated signal processing.

G. Theile, H. Wittek, and M. Reisinger "Wave Field Synthesis - New Possibilities of Spatial Sound Recording and Playback - Part II", Television and Cinema Engineering, Vol. 57, No. 6, June 2003, pages 282-285 , specifies a method for reproducing two- and multi-channel stereophonic signals using a wave-field synthesis system (see Section 5.2 there).

It is the object of the present invention to provide an apparatus and a method for reproducing spatial audio signals more efficiently and with better spatial resolution.

This object is achieved by a device according to claim 1, a method according to claim 17, or a computer program according to claim 18.

The core idea of the present invention lies in recognizing that, for example with the help of wave field synthesis, a high spatial resolution can be achieved, which can be used to simulate static virtual sound waves. The static virtual sound waves can then be adapted to the respective audio format.

It is also preferable that the property of the virtual sound waves can be adjusted to the reproduction format so that the characteristics of point sources or plane waves can be used.

For example, a 5.1. Audio signal, which is transmitted over five z. B. arranged on a circle speaker is reproduced by five simulated sound waves using a wave field synthesis, for example, a speaker array of one hundred speakers, emulated. In this way, the advantages of wave field synthesis, that is, the higher spatial resolution, and the advantages of other spatial audio signal processing methods, such as ambisonic, can be exploited. Accordingly, with the method according to the invention, a plurality of mobile sources can now be reproduced via a wave field synthesis, whereby the computation outlay for the wave field synthesis can be kept constant since this only has to simulate static sources which are based on static filters.

An advantage of the method according to the invention is also the selectable adaptation of the complexity of the necessary calculations to the resources available during the reproduction.

Fig. 1

ein Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 2

ein weiteres Ausführungsbeispiel der vorliegenden Erfindung;

Fig. 3

eine Veranschaulichung eines Ausführungsbeispiels der vorliegenden Erfindung; und

Fig. 4

eine beispielhafte Implementierung der Näherungslösung mit Lautsprechern außerhalb eines Kreises.

Embodiments of the present invention will be explained in more detail below with reference to the accompanying figures. Show it:

Fig. 1

an embodiment of the present invention;

Fig. 2

another embodiment of the present invention;

Fig. 3

an illustration of an embodiment of the present invention; and

Fig. 4

an exemplary implementation of the approximate solution with speakers outside a circle.

Fig. 1 FIG. 10 shows a device 100 for generating a number of speaker signals 102 for a loudspeaker array that defines a playback space. The apparatus 100 includes a pre-stage 110 configured to generate a plurality of output audio signals 116 using one or more input audio signals 112 associated with one or more virtual locations 114, each output audio signal 116 associated with a loudspeaker position 118 defined by the pre-stage 110, and wherein the pre-stage 110 is configured such that the plurality of output audio signals 116 together simulate a reproduction of the input audio signal (s) 112 at the virtual position (s) 114, and wherein a number of output audio signals 116 is less than a number of loudspeaker signals 102 for the loudspeaker array. The apparatus 100 further includes a main stage 120 configured to receive the plurality of output audio signals 116 and further as a virtual position for each output audio signal 116 to receive the loudspeaker positions 118 determined by the pre-stage 110, and wherein the main stage 120 is formed, to generate the number of speaker signals 102 for the speaker array such that the loudspeaker array replicates the loudspeaker positions 118 defined by the pre-stage 110 as a virtual source.

In one embodiment of the present invention, the main stage 120 is configured to generate the number of loudspeaker signals 102 and those generated by the pre-stage 110 fixed loudspeaker positions 118 by wave field synthesis. The loudspeaker array is controlled accordingly by the main stage 120. The defined loudspeaker positions 118 are thereby generated statically or in another embodiment semi-statically such that changes in position of the loudspeaker positions 118 occur less frequently or more slowly than changes in position of the virtual positions 114.

As a result, only static sources or semi-static sources are generated via wave field synthesis. As a result, the computation outlay for wavefield synthesis is reduced considerably, with moving sources still being able to take place via the preceding preamplifier 110 by corresponding control of the output audio signals 116.

In another embodiment of the present invention, the main stage 120 is configured to emulate a virtual speaker system that includes fewer speakers than the speaker array. The virtual speaker system can be emulated by point sources or by plane waves. If moving sources are to be simulated, this can be achieved by adapting the output audio signals 116 via the pre-stage 110, wherein the loudspeaker positions 118 can be left unchanged.

Input audio signals 112 are conceivable in many formats in embodiments of the present invention. In the embodiment, in Fig. 1 By way of example, it is assumed that the input audio signals 112 are provided separately from their virtual positions 114 of the pre-stage. According to the invention, however, all spatial audio formats are conceivable, such as Ambisonic, Quadrophonic, Prologic, Prologic II, Dolby Digital, Dolby Digital EX, DTS, DTS-ES, SDDS (SDDS = Sonic Dynamic Digital Sound), THX, IMAX, etc. According to the invention Pre-stage 110 via its input terminals, such as in the Fig. 1 the input audio signals 112 and the virtual positions 114, an image area in an audio format available. This image area is then imaged by the device 100 according to the invention into a real area that corresponds to the loudspeaker array and its loudspeaker signals 102. In this case, the pre-stage 110 converts the image area into an intermediate area, which can be mapped inexpensively from the main stage 120 into the real area.

In another embodiment, the inventive device 100 may be further configured to receive additional audio signals or additional locations that are also mapped to the loudspeaker signals 102 and the loudspeaker array, and whose format may differ from the format of the input audio signals 112. For example, it would be conceivable to drive static sources directly via the wave field synthesis, and to provide their virtual source positions and output audio signals directly to the main stage 120, whereas moving audio sources are driven via the pre-stage 110. The loudspeaker array itself can be realized, for example, by a circular loudspeaker array. In general, however, arbitrary forms of loudspeaker arrays are conceivable, wherein the main stage 120 may be designed to map the arbitrary shapes of loudspeaker arrays onto a virtual circle. This can be done for example by filtering the signals of the individual speakers, such. By amplitude scaling and delays per speaker. In this context, it is also possible to speak of irregular loudspeaker arrays, which in embodiments of the present invention can be imaged, for example, on a virtual circular array.

To further illustrate the present invention shows Fig. 2 an embodiment of a movie theater or concert hall 200. First, it was assumed that a speaker array 210 is disposed on a circle 215. The speaker array 210 encloses an auditorium 220 in which the spectators are present during a performance. With the help of the loudspeaker array 210, virtual sound waves 225 can now be generated via wave field synthesis. These virtual sound waves 225 can now be used at low cost, ie without increasing the computational requirements of wave field synthesis, in order to generate a spatial sound experience for a viewer in the auditorium 220.

In one embodiment of the present invention, wave field synthesis is used as a rendering system with the known advantages. In this case, only static sources are represented with the aid of wave field synthesis, which results in the elimination of the disadvantages caused by swelling and, for example, by dynamic filters. The computational effort of the wave field synthesis is kept largely constant, if necessary, the number of virtual sources can be reduced. The wave field synthesis thus provides a constant virtual speaker system. About a hybrid method, for. As coding of movements in Ambisonic, 5.1, VBAP, etc., now moving sources can be realized via the virtual speaker system.

Thus, a transmission in an image area is realized. A virtual sound source in the wave field synthesis represents a speaker of the virtual display device for the respective audio playback method into which the dynamic scene can be converted. These virtual speakers can be reproduced in wave field synthesis as point sources or even plane waves. Depending on the desired degree of reality or available computing capacity, an image area, for example in the Ambisonic domain, can be scaled in the degree of representation. The movement of a sound source takes place in the virtual speaker system as a change in volume of the virtual speakers. If necessary, in one embodiment, the duration of an original source, for example, directly in the original area, or changed, as in Higher Order Ambisonic possible, even in the image area. In general, the format of the audio scenes is not subject to any restrictions. For example, a wave field synthesis scene could be made from e.g. B. Ambientic XMT SAW or in any other multi-channel audio playback method, such as 5.1. Characteristic of this hybrid method is a separation into two areas, the original and the image area. Synonymous with this is an independence in the scene creation or coding of the ultimately used speaker set-up.

The following is a preferred conversion of WFS input data into Ambisonic data. The starting point is the XML format. The individual sound events are encoded as objects. The following information is contained in the object descriptions: Position of the .wav file with the audio signal of the source, existence period of the source, and movement information of the source (position of the source with time stamps).

The coding then takes place as follows: The position (distance and angle of incidence) of the sound source are calculated accurately to the sample. This information can be used to directly calculate Ambisonic signals for simple Ambisonic and Ambisonic-WFS Hybrid. In ambisonic with near-field coding, the ambisonic weighting factors in the frequency domain are calculated. With a window length which allows a good reproduction quality, only a sudden movement of the source is possible. Window overlapping, however, can mitigate the effect. The Ambisonic-WFS hybrid method calculates the symmetry properties of Ambisonic for more efficient computation. When hybrid and near field coded Ambisonic is to be noted that the Ambisonics signals are valid for a circle with a given radius, since the near field effects of both the source and the speaker are included in the calculation.

When playing simple Ambisonics signals no further effects need to be considered. Playback simply takes place via the Ambisonicplayer.

If the display corresponds exactly to the assumptions in the encoding, the Ambisonics signals from the hybrid and near-field coded method can also be used directly. If the display does not exactly match, there are two possibilities: The near field effects of the speakers are considered exactly. This takes into account the near-field effect already assumed during decoding. However, this method is expensive.

The second possibility is an approximate solution. For this purpose, the signals of the loudspeakers are delayed and amplified according to their distance from the center of the circle. Simulations have shown that this approach provides results comparable to the first (exact) approach. The prerequisite is that the radius of the loudspeaker assumed in the coding is on the order of magnitude of the radii of the playback loudspeakers (best mean value).

A preferred arrangement of the circle is in Fig. 4 shown. If you set the radius so that sources are within the radius, so you would attenuate the signals according to their distance from the center and "accelerate" compared to the other speakers, which z. B. can be achieved by delaying all other speaker signals, so that the one non-delayed speaker is accelerated compared to the other speakers.

Generally speaking, the pre-stage 110 is preferably configured to change the position of the moved virtual positions 114 by matching the output audio signals 116 and leaving the speaker positions 118 unchanged, the adaptation comprising delaying or amplifying a component component signal originating from a virtual source corresponding to a distance of a virtual source from an imaginary circle center on which the speaker positions are placeable.

Here, it is preferred that for each loudspeaker position, the loudspeaker component signals for the moving virtual sources be added after the respective delay or gain to produce a matched output audio signal.

For example, changing the position of a source away from one loudspeaker and towards another loudspeaker causes the component signal of the source for the loudspeaker from which the source has been moved to be delayed and somewhat attenuated depending on the amount of change in position becomes. In contrast, the component signal of the loudspeaker to which the source has been moved may be delayed negatively and somewhat amplified depending on the displacement of the position change. If a negative delay is not possible, the signal can not be changed, but all other signals, so that effectively a negative delay or "acceleration" of the one signal with respect to the other signals is achieved.

Embodiments of the present invention may also use non-circular or irregular speaker assemblies. In this case, the signals are prefiltered according to their reproduction position, ie, their amplitude and phase and sound spectrum are changed in such a way that the distance of a loudspeaker from a virtual circle is compensated. In this case, irregular loudspeaker arrangements are restored to a virtual circular loudspeaker arrangement displayed. This effect is in the Fig. 2 also clarified. Assuming that the movie theater or concert hall has a rectangular shape, as indicated by 230, for example, embodiments of the present invention may map these non-regular speakers to a virtual circle 215 by scaling the corresponding signals in amplitude, and whose delay is adjusted.

It does not matter how the ambisonic signals were obtained, for example. Furthermore, embodiments of the present invention offer the possibility of adapting the ideal listening area. This possibility is given indirectly by the virtual sound sources, which in another embodiment are adaptable or semi-static.

The Fig. 3 clarifies this procedure. Fig. 3 FIG. 12 shows an original area 300, an image area 310, and a wave field synthesis rendering 320. In the original area 300, there is, for example, a stereo signal or a signal in any other spatial audio format. This signal can now be converted into an image area, whereby the order of the image area is scalable according to the audio format. The image area 310 could be, for example, an ambisonic signal. The image area 310 is based on the Fig. 1 provided by the pre-stage 110. From the image area 310 is adapted to a speaker setup, which also irregular speaker setups are taken into account, there is a hybridization of the audio signal. Wave field synthesis playback 320 in FIG Fig. 3 corresponds to the main level 120 of Fig. 1 and finally maps the image area into a real area, namely loudspeaker signals for a loudspeaker array.

The complexity, that is, the computational effort required for wave field synthesis, can thus be finite Number of static filters are restricted. Thus, many problems of wave field synthesis with respect to moving sound waves can be solved, such as the occurrence of Doppler artifacts and temporal interpolation artifacts. The computational effort of the wave field synthesis can thus be kept almost constant and much lower than comparable wave field synthesis rendering. Embodiments of the present invention thus offer the advantage that a realization on DSP boards can be carried out much more cost-effectively (DSP = Digital Signal Processor).

To realize a wave field synthesis, for example, the exact solution of a wave equation can be used for the coding. The signals of the original range could be made, for example, from the direction coding according to the classical Ambisonic theory and a distance-dependent coding. Distance coding can be done by filtering the ambisonic signals of the individual orders. Near-field effects of the loudspeaker array loudspeakers as well as the coded sound sources can be combined, so that the resulting ambisonic signals can be kept limited. The filters used for wave field synthesis depend both on the frequency of the input signal and on the distance between the loudspeakers and the reproduced sound source. The filtering can be done in the frequency domain, with variable distance, a sliding windowing in the time domain can be made, the filter can be adjusted according to a different distance.

A calculation of the near-field-coded ambisonic signals by the hybrid approach provides a filter in the time domain, which is automatically valid for all frequencies. Thus, the consideration of different distances of the reproduced sound sources, ie the virtual sound sources, is easily possible. Furthermore, there is the possibility of prefiltering the signals to process-related To compensate for attenuation of high frequencies. Then even higher frequencies can be discretely reproduced to exclude aliasing effects. Rotational matrices for Ambisonic can also be exploited to reduce the computational burden. The computational effort can then be reduced to a quarter, the two-dimensional case, or to an eighth, in the three-dimensional case, the cost of the direct calculation.

Embodiments of the present invention thus offer the advantage that the computational effort of spatial audio signals can be significantly reduced, and an adaptive system is realized.

In particular, it should be noted that, depending on the circumstances, the inventive scheme can also be implemented in software. The implementation may be on a digital storage medium, in particular a floppy disk or a CD with electronically readable control signals, which may cooperate with a programmable computer system such that the corresponding method is executed. In general, the invention thus also consists in a computer program product with program code stored on a machine-readable carrier for carrying out the method according to the invention when the computer program product runs on a computer. In other words, the invention can thus be realized as a computer program with a program code for carrying out the method when the computer program product runs on a computer.

LIST OF REFERENCE NUMBERS

100

Apparatus for generating a number of loudspeaker signals

102

Loudspeaker signal

110

preliminary stage

112

Input audio signal

114

virtual positions

116

Output Output signals

118

Speaker positions

120

main stage

200

Movie theater or concert hall

210

Speaker array for wave field synthesis

215

Circle.

220

auditorium

225

virtual sound sources

230

rectangular speaker arrangement

300

original area

310

image area

320

Wave field synthesis reproduction

Claims (18)

1. An apparatus (100) for generating a number of loudspeaker signals (102) for a loudspeaker array which defines a reproduction space, the apparatus comprising:

   a prestage (110) configured to generate a plurality of output audio signals (116) while using one or more virtual sources, a virtual source comprising one input audio signal (112), respectively, which is associated with a virtual position (114), each output audio signal (116) being associated to a loudspeaker position (118) specified by the prestage (110), and the prestage (110) being configured such that the plurality of output audio signals (116) together replicate a reproduction of the input audio signal(s) (112) at the virtual position(s) (114), and a number of output audio signals (116) being smaller than a number of loudspeaker signals (102) for the loudspeaker array; and

   a main stage (120) configured to obtain the plurality of output audio signals (116) and further to obtain, as a virtual position for each output audio signal (116), the loudspeaker positions (118) specified by the prestage (110), and the main stage (120) being configured to generate the number of loudspeaker signals (102) for the loudspeaker array such that the loudspeaker positions (118) specified by the prestage (110) are replicated as virtual sources by the loudspeaker array.
2. The apparatus as claimed in claim 1,
   wherein the virtual sources employed by the prestage (110) are moving virtual sources with variable positions,
   wherein the specified loudspeaker positions are static, and
   wherein the virtual positions corresponding to the specified static loudspeaker positions are static positions.
3. The apparatus (100) as claimed in claims 1 or 2,
   wherein the prestage is configured to process all of the moving virtual sources of a number of virtual sources input comprising moving and static virtual sources, and
   wherein the main stage is configured to process only static virtual sources,
   wherein the static virtual sources comprise the virtual sources which are specified by the static loudspeaker positions, and additionally comprise the static virtual sources input.
4. The apparatus (100) as claimed in any of claims 1 to 3, wherein the main stage (120) is configured to generate, by means of wave field synthesis, the number of loudspeaker signals (102) and the loudspeaker positions (118) specified by the prestage (110).
5. The apparatus (100) as claimed in any of claims 1 to 4, wherein the prestage (110) is configured to statically or semi-statically generate the specified loudspeaker positions (118) in such a manner that positional changes in the loudspeaker position (118) occur less frequently or more slowly than positional changes in the virtual positions (114).
6. The apparatus as claimed in any of claims 1 to 5, wherein the main stage (120) is configured to emulate a virtual loudspeaker system which comprises fewer loudspeakers than the loudspeaker array.
7. The apparatus (100) as claimed in claim 6, wherein the virtual loudspeaker system is emulated by point sources or plane waves.
8. The apparatus (100) as claimed in any of claims 1 to 7, wherein the prestage (110) is configured to map positional changes in the virtual positions (114) by adapting the output audio signals (116), and to leave the loudspeaker positions (118) unchanged.
9. The apparatus (100) as claimed in claim 8, wherein the prestage (110) is configured to effect the adaptation of the output audio signals (116) by means of a delay or amplification of a loudspeaker component signal going back to a virtual source, the delay or amplification corresponding to a distance of a virtual source from an imaginary center of a circle on which the loudspeaker positions may be placed.
10. The apparatus (100) as claimed in claim 9, wherein the prestage (110) is configured to add, for each loudspeaker position, the loudspeaker component signals for the moving virtual sources after the respective delay or amplification in order to generate an adapted output audio signal.
11. The apparatus (100) as claimed in any of claims 1 to 10, wherein the prestage (110) is configured to process input audio signals (112) encoded in accordance with XMT-SAW, Open-AI 5.1, Ambisonic, Quadrophonic, Prologic, Prologic II, Dolby Digital, Dolby Digital-EX, DTS, DTS-ES, SDDS, 10.2, THX or IMAX.
12. The apparatus (100) as claimed in any of claims 1 to 11, configured to provide, via the input audio signals (112) and the virtual positions (114), an image domain which is mapped to an original domain via the loudspeaker signals (102) and the loudspeaker array.
13. The apparatus (100) as claimed in any of claims 1 to 12, wherein the main stage (120) is configured to obtain additional audio signals or additional positions which are mapped to the loudspeaker signals (102) and to the loudspeaker array, and the formats of which differ from the formats of the input audio signals (112).
14. The apparatus (100) as claimed in any of claims 1 to 13, wherein the main stage (120) is configured to control a circular loudspeaker array.
15. The apparatus (100) as claimed in any of claims 1 to 14, wherein the main stage (120) is configured to control an irregular loudspeaker array such that the individual loudspeaker signals (102) are adapted to the irregular shape of the loudspeaker array.
16. The apparatus (100) as claimed in claim 15, wherein the main stage (120) is configured to perform the adaptation of the loudspeaker signals (102) to the irregular loudspeaker array by individually delaying and amplifying the loudspeaker signals (102).
17. A method of generating a number of loudspeaker signals (102) for a loudspeaker array which defines a reproduction space, the method comprising:

    generating a plurality of output audio signals (116) while using one or more virtual sources, a virtual source comprising one input audio signal (112), respectively, which is associated with one or more virtual positions (114), each output audio signal (116) being associated to a loudspeaker position (118) specified by a prestage (110), and the plurality of output audio signals (116) together replicating a reproduction of the input audio signals (112) at the virtual positions (114), and a number of output audio signals (116) being smaller than a number of loudspeaker signals (102) for the loudspeaker array;

    obtaining the plurality of output audio signals (116) and the loudspeaker positions (118) for each output audio signal (116); and

    generating the number of loudspeaker signals (102) for the loudspeaker array, so that the loudspeaker positions (118) specified by the prestage (110) are replicated as virtual sources by the loudspeaker array.
18. A computer program having a program code for performing the method as claimed in claim 17, when the computer program runs on a computer or microcontroller.

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