EP1844627B1 - Device and method for simulating an electromagnetic field synthesis system - Google Patents

Abstract

For simulating a wave field synthesis system, an audio scene description defining a temporal sequence of audio objects is provided, an audio object having an audio file for a virtual source or a reference to the audio file and information on a source position of the virtual source. Furthermore, an output condition the wave field synthesis system is to satisfy is given. Furthermore, a simulator for simulating the behavior of the wave field synthesis system for the audio scene description, using the audio data and the source positions as well as information on the wave field synthesis system, is provided. Finally a checker performs a check to determine if the simulated behavior of the wave field synthesis system satisfies the output condition. This achieves more flexible audio scene description creation as well as flexible portability of an audio scene description developed for one system to another wave field synthesis system.

Description

The present invention relates to the wave field synthesis technique, and more particularly to tools for creating audio scene descriptions and for verifying audio scene descriptions, respectively.

There is an increasing demand for new technologies and innovative products in the field of consumer electronics. It is an important prerequisite for the success of new multimedia systems to offer optimal functionalities and capabilities. This is achieved through the use of digital technologies and especially computer technology. Examples of these are the applications that offer an improved, realistic audiovisual impression. In previous audio systems, a significant weakness lies in the quality of the spatial sound reproduction of natural, but also of virtual environments.

Methods for multi-channel speaker reproduction of audio signals have been known and standardized for many years. All the usual techniques have the disadvantage that both the installation site of the loudspeakers and the position of the listener are already impressed on the transmission format. If the speakers are arranged incorrectly with respect to the listener, the audio quality suffers significantly. An optimal sound is only possible in a small area of the playback room, the so-called sweet spot.

A better natural spatial impression as well as a stronger envelope in the audio reproduction can be achieved with the help of a new technology. The basics of this technology, the so-called wave field synthesis (WFS = Wave Field Synthesis), were researched at the TU Delft and first introduced in the late 80s ( Berkhout, AJ; de Vries, D .; Vogel, P .: Acoustic control by wave-field synthesis. JASA 93, 1993 ).

Due to the enormous demands of this method on computer performance and transmission rates, wave field synthesis has rarely been used in practice. Only the advances in the areas of microprocessor technology and audio coding allow today the use of this technology in concrete applications. The first professional products are expected next year. In a few years, the first wave field synthesis applications for the consumer sector will be launched.

The basic idea of WFS is based on the application of Huygens' principle of wave theory:

Every point, which is detected by a wave, is the starting point of an elementary wave, which spreads in a spherical or circular manner.

Applied to the acoustics can be simulated by a large number of speakers, which are arranged side by side (a so-called speaker array), any shape of an incoming wavefront. In the simplest case, a single point source to be reproduced and a linear arrangement of the speakers, the audio signals of each speaker must be fed with a time delay and amplitude scaling so that the radiated sound fields of each speaker properly overlap. With multiple sound sources, the contribution to each speaker is calculated separately for each source and the resulting signals added together. If the sources to be reproduced are in a room with reflective walls, reflections must also be reproduced as additional sources via the loudspeaker array. The effort in the calculation therefore depends heavily on the number of sound sources, the reflection characteristics of the recording room and the number of speakers.

The advantage of this technique is in particular that a natural spatial sound impression over a large area of the playback room is possible. In contrast to the known techniques, the direction and distance of sound sources are reproduced very accurately. To a limited extent, virtual sound sources can even be positioned between the real speaker array and the listener.

Although wavefield synthesis works well for environments whose characteristics are known, irregularities occur when the texture changes, or when wave field synthesis is performed based on environmental conditions that do not match the actual nature of the environment.

An environmental condition can be described by the impulse response of the environment.

This will be explained in more detail with reference to the following example. It is assumed that a loudspeaker emits a sound signal against a wall whose reflection is undesirable. For this simple example, the space compensation using wavefield synthesis would be to first determine the reflection of that wall to determine when a sound signal reflected from the wall will return to the loudspeaker and what amplitude this reflected sound signal will be Has. If the reflection from this wall is undesirable, then with the wave field synthesis it is possible to eliminate the reflection from this wall by impressing the loudspeaker with a signal of opposite amplitude to the reflection signal in addition to the original audio signal, so that the traveling compensating wave is the Reflectance wave extinguished, so that the reflection from this wall in the environment that looks is, is eliminated. This can be done by first computing the impulse response of the environment and determining the nature and position of the wall based on the impulse response of that environment, the wall being interpreted as a source of mirrors, that is, a sound source reflecting an incident sound.

If the impulse response of this environment is first measured and the compensation signal is then calculated, which must be impressed on the audio signal superimposed on the loudspeaker, then the reflection from this wall will be canceled, such that a listener in this environment will soundly have the impression that the latter Wall does not exist at all.

Decisive for an optimal compensation of the reflected wave, however, is that the impulse response of the room is accurately determined, so that no overcompensation or undercompensation occurs.

The wave field synthesis thus allows a correct mapping of virtual sound sources over a large playback area. At the same time it offers the sound engineer and sound engineer new technical and creative potential in the creation of even complex soundscapes. Wavefield synthesis (WFS or sound field synthesis), as developed at the TU Delft in the late 1980s, represents a holographic approach to sound reproduction. The basis for this is the Kirchhoff-Helmholtz integral. This states that any sound fields within a closed volume can be generated by means of a distribution of monopole and dipole sound sources (loudspeaker arrays) on the surface of this volume.

In wave field synthesis, a synthesis signal for each loudspeaker of the loudspeaker array is calculated from an audio signal which emits a virtual source at a virtual position, the synthesis signals being such in terms of amplitude and phase, that a wave resulting from the superposition of the individual sound waves output by the loudspeakers present in the loudspeaker array corresponds to the wave which would originate from the virtual source at the virtual position, if this virtual source is at the virtual position would be a real source with a real position.

Typically, multiple virtual sources exist at different virtual locations. The computation of the synthesis signals is performed for each virtual source at each virtual location, typically resulting in one virtual source in multiple speaker synthesis signals. Seen from a loudspeaker, this loudspeaker thus receives several synthesis signals, which go back to different virtual sources. A superimposition of these sources, which is possible due to the linear superposition principle, then gives the reproduced signal actually emitted by the speaker.

The possibilities of wave field synthesis can be better exploited, the larger the loudspeaker arrays are, d. H. the more individual speakers are provided. However, this also increases the computing power which a wave field synthesis unit has to accomplish, since channel information also typically has to be taken into account. This means in more detail that from each virtual source to each speaker in principle a separate transmission channel is present, and that in principle there may be the case that each virtual source leads to a synthesis signal for each speaker, or that each speaker a number of synthesis signals which equals the number of virtual sources.

If, in particular, in cinema applications the possibilities of wave field synthesis are to be exploited to the extent that the virtual sources can also be mobile, it can be seen that due to the calculation of the synthesis signals, the computation of the channel information and the generation of the playback signals by combining the channel information and the synthesis signals very considerable computing power are to be handled.

In addition, it should be noted at this point that the quality of the audio playback increases with the number of speakers provided. This means that the audio reproduction quality becomes better and more realistic as more loudspeakers are present in the loudspeaker array (s).

In the above scenario, the final-rendered and analog-to-digital converted reproduction signals for the individual loudspeakers could be transmitted, for example via two-wire lines, from the wave field synthesis central unit to the individual loudspeakers. Although this would have the advantage that it is almost ensured that all speakers work in sync, so that here for synchronization purposes, no further action would be required. On the other hand, the wave field synthesis central unit could always be made only for a special reproduction room or for a reproduction with a fixed number of loudspeakers. This means that a separate wave field synthesis central unit would have to be produced for each reproduction space, which has to accomplish a considerable amount of computing power, since the calculation of the audio reproduction signals has to be at least partially parallel and in real time, in particular with regard to many loudspeakers or many virtual sources ,

The German patent DE 10254404 B4 discloses a system as it is in Fig. 7 is shown. One part is the central wave field synthesis module 10. The other part is composed of individual speaker modules 12a, 12b, 12c, 12d, 12e which are connected to actual physical speakers 14a, 14b, 14c, 14d, 14e as shown in FIG Fig. 1 is shown. It should be noted that the number For example, in typical applications, the speaker 14a-14e is in the range above 50 and typically well above 100. If each loudspeaker is assigned its own loudspeaker module, the corresponding number of loudspeaker modules is also required. Depending on the application, however, it is preferred to address a small group of adjacent loudspeakers from a loudspeaker module. In this context, it is arbitrary whether a speaker module, which is connected to four speakers, for example, feeds the four speakers with the same playback signal, or whether the four speakers corresponding different synthesis signals are calculated, so that such a speaker module actually off consists of several individual speaker modules, but which are physically combined in one unit.

Between the wave field synthesis module 10 and each individual loudspeaker module 12a-12e there is a separate transmission link 16a-16e, each transmission link being coupled to the central wave field synthesis module and to a separate loudspeaker module.

As a data transmission mode for transmitting data from the wave field synthesis module to a speaker module, a serial transmission format providing a high data rate such as a so-called Firewire transmission format or a USB data format is preferred. Data transfer rates in excess of 100 megabits per second are advantageous.

The data stream which is transmitted from the wave field synthesis module 10 to a loudspeaker module is thus correspondingly formatted according to the selected data format in the wave field synthesis module and provided with synchronization information which is provided in conventional serial data formats. This synchronization information is extracted from the data stream by the individual loudspeaker modules and used to control the individual loudspeaker modules in terms of their reproduction, that is, ultimately to the analog-to-digital conversion to obtain the analog loudspeaker signal and the purpose of resampling to synchronize. The central wave-field synthesis module works as a master and all loudspeaker modules operate as clients, with the individual data streams across the different links 16a-16e all receiving the same synchronization information from the central module 10. This ensures that all loudspeaker modules operate synchronously, synchronized by the master 10, which is important to the audio playback system so as not to suffer any loss of audio quality, so that the synthesis signals computed by the wavefronts synthesis module are not delayed in response to the individual loudspeakers Audio rendering will be broadcast.

Although the concept described already provides considerable flexibility with regard to a wave field synthesis system that is scalable for various applications. However, it continues to suffer from the problem that the central wave field synthesis module, which performs the actual main rendering, which thus calculates the individual synthesis signals for the speakers, depending on the positions of the virtual sources and depending on the speaker positions Represents "bottleneck" for the entire system. Although in this system, the "post-rendering", ie the application of the synthesis signals with channel transfer functions, etc. already executed decentralized and thus already the necessary data transfer capacity between the central renderer module and the individual speaker modules by selecting synthesis signals with a smaller However, energy has been reduced as a certain threshold energy, but all virtual sources must be rendered so to speak for all speaker modules, so converted into synthesis signals, the Ausselektion takes place only after the rendering.

This means that the rendering still determines the total capacity of the system. Is the central rendering unit therefore z. For example, if it is able to render 32 virtual sources simultaneously, ie to compute the synthesis signals for these 32 virtual sources simultaneously, then serious capacity bottlenecks will occur if more than 32 sources are active at a time in an audio scene. This is sufficient for simple scenes. For more complex scenes, in particular with immersive sound impressions, ie when it rains and many raindrops are single sources, it is immediately obvious that the capacity with a maximum of 32 sources is no longer sufficient. A similar situation also occurs when you have a large orchestra and in fact want to process every orchestra player or at least each group of instruments as their own source in their own position. Here, 32 virtual sources can quickly become too little.

Typically, in the known wave field synthesis concept, a scene description is used in which the individual audio objects are defined together such that, using the data in the scene description and the audio data for the individual virtual sources, the complete scene is rendered by a renderer or a multi-rendering Arrangement can be processed. For each audio object, it is exactly defined where the audio object has to start and where the audio object ends. Furthermore, for each audio object, exactly the position of the virtual source is indicated at which the virtual source should be, which is to be entered into the wave field synthesis rendering device, so that for each speaker the corresponding synthesis signals are generated. As a result, by superposing the sound waves outputted from the individual speakers in response to the synthesis signals to a listener, an impression is made as if a sound source were at a position in the playback room or outside of the playback space defined by the source position of the virtual source.

A disadvantage of the concept described is the fact that it is relatively rigid, in particular when creating the audio scene descriptions. So a sound engineer will create an audio scene just for a particular wave field synthesizer, of which he knows exactly the situation in the playback room and the audio scene description created so that it runs smoothly on the well-defined wave field synthesis system known to the producers.

In this context, the sound engineer will consider the maximum capacity of the wave field synthesis rendering device as well as wave field requirements in the rendering room already when creating the audio scene description. For example, if a renderer has a maximum capacity of 32 audio sources to process, the sound engineer will already be careful to edit the audio scene description so that no more than 32 sources can be processed simultaneously.

Furthermore, the sound engineer already remember that in the positioning of z. B. two instruments, such as bass guitar and lead guitar for the entire playback room, whose expansions are known to the producer, Schallaufzeiten are to be met. So it is important for a clear and not blurred sound that z. B. bass guitar and lead guitar are relatively evenly perceived by the listener. A sound engineer will then, in the virtual positioning, so in the assignment of the virtual positions to these two sources, make sure that throughout the playback room is satisfied that the wavefront of these two instruments almost uniformly arrive at a listener.

An audio scene description is thus obtained as a sequence of audio objects, each audio object being a virtual one Position and a start time, an end time or a duration includes.

Normally, it is then effectively checked by manual checks, ie by listening to different positions in the playback room, whether the audio scene description can remain so, ie whether the producer of the audio scene description has actually worked well and has addressed all the requirements of the wave field synthesis system.

A disadvantage of this concept is that the sound engineer, who creates the audio scene description, must concentrate on boundary conditions of the wave field synthesis system, which actually have nothing to do with the creative side of the audio scene. It would therefore be desirable to whom the sound engineer could concentrate solely on the creative aspects without having to consider a particular wave field synthesis system on which his audi scene is to run.

Another disadvantage of the described concept is that when an audio scene description from a wave field synthesis system having a particular first behavior for which the audio scene description has been designed is to be made on another wave field synthesis system having a second behavior for which the audio scene has not been designed ,

Simply running the audio scene description on the system for which it was not designed would create problems in that audible errors will be introduced if the second system is less powerful than the first system.

On the other hand, if the second system is more powerful than the first system, the audio scene description becomes the second system only in terms of performance of the first system and do not exhaust the additional efficiency of the second system.

The second system also refers to a z. B. larger playback room, it can no longer be ensured at certain points that the wavefronts of two virtual sources, such as bass guitar and lead guitar, arrive almost simultaneously.

In particular, the problem of simultaneous or almost simultaneous perception of two virtual sources, which should be synchronous, is very problematic, especially since previously only manual test hearings and a subjective assessment of the quality at certain places in the playback room were possible for this purpose.

In response to such subjective assessments, the sound engineer was then required to thoroughly rework the already finished audio scene description for the second system, which in turn requires both time resources and financial resources.

In particular, due to the expectation of a strong spread of wave field synthesis systems in the near future, the question of flexible audio scene descriptions, which can be played universally on arbitrary systems, more and more, in order to achieve at some point a similar portability or compatibility, as for CDs or DVDs are common prior art.

The specialist publication " Wave Field Synthesis Simulation by Means of Finite-Difference Time-domain Technique ", José Escolano et al., Proceedings of the 12th European Signal Processing Conference (EUSIPCO 2004), September 6, 2004, pages 1777-1780 discloses a concept for simulating a wave field generated by a wave field synthesis system. For this purpose, the FDTD method is used, which has been used for the modeling of electromagnetic systems. For the FDTD simulation a uniform grid is used, whereby the maximum frequency of the simulation is adjustable by changing the cell size. It is possible to simulate the effect of the playback room on the synthesized sound field. This makes it possible to eliminate space effects dynamically by generating corresponding signals.

The object of the present invention is to provide a concept for simulating a wave field synthesis system by which an audio scene description can be efficiently examined for a particular wave field synthesis system and related potentially occurring errors.

This object is achieved by a device for simulating a wave field synthesis system according to claim 1 or a method for simulating a wave field synthesis system according to claim 15 or a computer program according to claim 16.

The present invention is based on the recognition that in addition to an audio scene description that defines a temporal sequence of audio objects, output conditions are provided either within the audio scene description or separately from the audio scene description, then the behavior of the wave field synthesis system on which an audio scene description is to run to simulate. Based on the simulated behavior of the wave field synthesis system and on the basis of the output conditions, it can then be checked whether the simulated behavior of the wave field synthesis system fulfills the output condition or not.

This concept makes it easy to simulate one audio scene description for another wave field synthesis system and to account for system independent general output conditions for the other wave field synthesis system without the sound engineer or creator of the audio scene description dealing with such "secular" things of an actual wave field synthesis. Would have to deal with systems. The occupation with the actual boundary conditions of a wave field synthesis system, for example with regard to the capacity of the renderers or the size or the number of speaker arrays in the reproduction room, is taken from the sound engineer by the device according to the invention. He can simply write his audio scene description, guided by creative thoughts, as he would like to, by protecting the artistic impression through the system-independent output conditions.

Then it is checked by the inventive concept, whether the audio scene description, the universal, ie has not been written for a particular system, can run on a specific system, if and where appropriate in the playback room problems occur. According to the invention, it is not necessary to wait for elaborate listening tests, etc., in this processing, but the processor can simulate the behavior of the wave field synthesis system almost in real time and verify it on the basis of the given output condition.

According to the invention, the output condition may refer to hardware aspects of the wave field synthesis system, such as a maximum processing capability of the renderer device, or to sound field specific things in the rendering room, such as having wavefronts of two virtual sources perceived within a maximum time difference. or that level differences between two virtual sources at all points or at least at certain points in the playback room must be in a predetermined corridor. In view of the hardware-specific output conditions, it is preferable not to include them in the audio scene description due to the flexibility and compatibility requirements, but to provide them externally to the reviewer.

On the other hand, in view of sound field-related output conditions, that is, output conditions that define what a sound field has to fulfill in the reproduction room, it is preferable to include them in the audio scene description. Thus, a creator of an audio scene description ensures that at least minimum sound impression requirements are met, but that some flexibility remains in wave field synthesis rendering in order to play an audio scene description not only with optimal quality on a single wave field synthesis system, but rather different wave-field synthesis systems, adding the flexibility granted by the author through intelligent post-processing of the audio scene description, However, which is preferably carried out by machine, is advantageously exploited.

In other words, the present invention serves as a tool to verify whether output conditions of an audio scene description can be met by a wave field synthesis system. Should violations of output conditions occur, the inventive concept in the preferred embodiment will inform the user which virtual sources are problematic, where in the playback room violations of the output conditions occur and at what time. Thus, it can be judged whether an audio scene description easily runs on any wave field synthesis system or whether the audio scene description needs to be rewritten due to serious violations of the output conditions, or if violations of the output conditions occur, but they are not so serious as to actually describe the audio scene would have to manipulate.

Fig. 1a

ein Blockschaltbild einer erfindungsgemäßen Vorrichtung zum Simulieren eines Wellenfeldsynthese-Systems;

Fig. 1b

eine spezielle Implementierung der Einrichtung zum Simulieren gemäß Fig. 1a;

Fig. 1c

ein Flussdiagramm zum Darstellen der Vorgänge bei einer Ausgabebedingung, die eine Eigenschaft zwischen zwei virtuellen Quellen definiert;

Fig. 1d

eine schematische Darstellung eines Wiedergaberaums und von Problemzonen bei einem bevorzugten Ausführungsbeispiel der vorliegenden Erfindung, bei dem Auftreffzeitpunkte von Schallfeldern in der Ausgabebedingung enthalten sind;

Fig. 2

ein beispielhaftes Audioobjekt;

Fig. 3

eine beispielhafte Szenenbeschreibung;

Fig. 4

einen Bitstrom, in dem jedem Audioobjekt ein Header mit den aktuellen Zeitdaten und Positionsdaten zugeordnet ist;

Fig. 5

eine Einbettung des erfindungsgemäßen Konzepts in ein Wellenfeldsynthese-Gesamtsystem;

Fig. 6

eine schematische Darstellung eines bekannten Wellenfeldsynthese-Konzepts; und

Fig. 7

eine weitere Darstellung eines bekannten Wellen-feldsynthese-Konzepts.

Preferred embodiments of the present invention will be explained below in detail with reference to the accompanying drawings. Show it:

Fig. 1a

a block diagram of an apparatus according to the invention for simulating a wave field synthesis system;

Fig. 1b

a specific implementation of the means for simulating according to Fig. 1a ;

Fig. 1c

a flowchart for illustrating the processes in an output condition that defines a property between two virtual sources;

Fig. 1d

a schematic representation of a playback room and problem areas in a preferred Embodiment of the present invention in which landing times of sound fields in the output condition are included;

Fig. 2

an exemplary audio object;

Fig. 3

an exemplary scene description;

Fig. 4

a bit stream in which each audio object is assigned a header with the current time data and position data;

Fig. 5

an embedding of the inventive concept in a wave field synthesis overall system;

Fig. 6

a schematic representation of a known wave field synthesis concept; and

Fig. 7

another illustration of a known wave field synthesis concept.

Fig. 1a shows a schematic representation of an inventive device for simulating a wave field synthesis system with a playback room in which one or more speaker arrays and a coupled to the speaker array wave field synthesis rendering device can be attached. The inventive apparatus comprises means 1 for providing an audio scene description defining a temporal sequence of audio objects, wherein an audio object comprises an audio file for a virtual source or a reference to the audio file and information about a source location of the virtual source. The audio files may either be contained directly in the audio scene description 1 or may be identifiable by references to audio files in an audio file database 2 and fed to a device 3 for simulating the behavior of the wave field synthesis system.

Depending on the implementation, the audio files are controlled via a control line 1a or supplied to the simulation device 3 via a line 1b, which also contains the source positions. On the other hand, if the files are supplied directly from the audio file database 2 to the device 3 for simulating the behavior of the wave field synthesis system, a line 3a will be active which is in Fig. 1a indicated by dashed lines. The device 3 for simulating the wave field synthesis system is designed to use information about the wave field synthesis system, and then, on the output side, to supply the simulated behavior of the wave field synthesis system to a device 4 for checking the output condition.

The device 4 is designed to check whether the simulated behavior of the wave field synthesis system fulfills the output condition or not. For this purpose, the device 4 for checking receives an output condition via an input line 4a, the output condition being supplied either externally to the device 4. Alternatively, the output condition may also be derived from the audio scene description, as represented by a dashed line 4b.

The first case, that is, where the issue condition is externally supplied, is preferred when the issue condition is a hardware-technical condition related to the wave-field synthesis system, such as a maximum transfer capacity of a data connection or, as a bottleneck of overall processing, a maximum Computing capacity of a renderer, or, in multi-renderer systems, a single renderer module.

Renderers generate synthesis signals from the audio files using information about the speakers and using information about the source locations of the virtual sources, that is, for each of the many speakers a separate signal, wherein the synthesis signals to each other have different phase and amplitude ratios, so that the many speakers according to the theory of wave field synthesis generate a common wavefront that propagates in the playback room. After the calculation of the synthesis signals is very expensive, typical renderer modules are limited in their capacity, such as a maximum capacity of 32 simultaneously to be processed virtual sources. Such an output condition, namely that a maximum of 32 sources may be processed by a renderer at a time, could be provided, for example, to the device 4 for checking the output condition.

Alternative output conditions, which should typically be included in the audio scene description according to the invention, relate to the sound field in the playback room. In particular, output conditions define a sound field or property of a sound field in the playback room.

In this case, the wave field synthesis system simulating means 3 is configured to simulate the sound field in the reproducing room using information about an arrangement of the one or more speaker arrays in the reproducing room and using the audio data.

Further, the means 4 for checking in this case is arranged to check whether or not the simulated sound field satisfies the output condition in the reproduction room.

Further, in a preferred embodiment of the present invention, the means 4 will be arranged to provide a display, such as an optical display, telling the user whether the dispensing condition is not met, completely satisfied, or only partially fulfilled. In the case of partial fulfillment, the device 4 is also designed to check to z. B., as it is based on Fig. 1d is presented to identify problem areas in the playback room (WGR), where z. B. a wavefront output condition is not met. Based on this information, a user of the simulation tool can then decide whether he accepts the partial violation or not, or whether he takes certain measures to achieve a lesser violation of the output conditions, etc.

Fig. 1b shows a preferred implementation of the device 3 for simulating a wave field synthesis system. The device 3 comprises in the in Fig. 1b shown preferred embodiment of the present invention, a required anyway for a wave field synthesis system wave field synthesis rendering device 3b to from the scene description, the audio files, the information about speaker positions or possibly further information about the z. B. acoustics of the playback room, etc. Synthesis signals to be generated, which are then supplied to a speaker simulator 3 c. The speaker simulator is configured to detect a sound field in the playback room, preferably at each position of interest in the playback room. With reference to the procedure, refer to below Fig. 1c is described, it can then be determined for each searched point in the playback room, whether a problem has occurred or not.

At the in Fig. 1c The flow diagram shown is first simulated by the device 3 for simulating a wavefront in the reproduction space for a first virtual source (5a). Then, by means 3, a wavefront in the reproduction space for the second virtual source is simulated (FIG. 5b). Of course, the two steps 5a and 5b in the presence of appropriate computing capacities also parallel to each other, so be performed simultaneously. This is followed in a step 5c on the basis of the first Wavefront calculated for the first virtual source and based on the second wavefront for the second virtual source a property to be simulated. Preferably, this property will be a property that must be satisfied between two particular virtual sources, such as a level difference, a runtime difference, etc. Which property is calculated in step 5c depends on the output condition, since of course only information needs to be simulated, which should also be compared with output conditions. The actual comparison of the calculated property, ie the result of step 5c, with the output condition takes place in a step 5d.

If the sequence of steps 5a to 5d is performed for different points, then in a step 5e, not only can it be indicated whether a condition is not satisfied, but also where in the playback room such a condition is not met. Furthermore, in the in Fig. 1c 5, the problematic virtual sources are also identified.

Subsequently, reference will be made to Fig. 1d a preferred embodiment of the present invention is shown. An output condition that is in Fig. 1 is considered, defines a sound propagation time with respect to audio data. Thus, it is preferable to specify in the audio scene description that the wavefront due to a guitar and the wavefront due to a bass at each point in the playback room only a maximum of a certain period of time .DELTA.tmax may arrive separated from each other, so this condition is particularly in the in Fig. 1d shown reproduction space, which is surrounded by four loudspeaker arrays LSA1, LSA2, LSA3, LSA4, then, if the sources are positioned according to the audio scene description very far apart, not to be fulfilled for each point in the playback room. Problem zones identified by the inventive concept are in Fig. 1d plotted in the playback room.

At the in Fig. 1d For example, the producer has positioned the guitar and the bass at a distance of 100 m. Further, as the output condition, a maximum transit time difference of 10 m was set for the entire reproduction space, that is, a period of 10 m divided by the speed of sound. The procedure according to the invention, as described on the basis of Fig. 1 has been described, the problem areas, as in Fig. 1d are hinted at and a producer or a sound engineer who the audio scene description with regard to the wave field synthesis system, the in Fig. 1d shown, communicate.

Therefore, according to the invention, performance bottlenecks and quality holes can be predicted. This is achieved by favoring centralized data management, that is to say that both the scene description and the audio files are stored in an intelligent database, and furthermore that a device 3 for simulating the wave field synthesis system is provided, which is a more or less accurate simulation of the wave field synthesis -Systems supplies. This eliminates costly manual testing and artificially limiting system performance to a level considered to be performance and quality assured.

In particular, it is preferable to set output conditions with respect to temporal references of different virtual sources. Thus, different audio sources have more or less fixed temporal references. While delaying the start of wind noise by 50 milliseconds does not result in much discernable quality degradation, drifting apart of the synchronous signals of a guitar and bass can result in significant quality degradation in the perceived audio signal. The severity of perceived quality degradation depends on the position of the listener in the playback room. According to the invention, such Problem zones in the playback room are automatically detected, visualized or blocked.

According to the invention, for a particularly favorable definition of the output conditions, a relative definition of the audio objects relative to each other and, in particular, a positioning which is variable within a time span or spatial range is preferred, as it is based on Fig. 3 will be described.

Thus, the relative positioning or arrangement of audio objects / audio files, either with or without the use of a database, provides a workable way to define output conditions that preferably relate to a property of two virtual objects, that is also something relative. Preferably, however, a database is still used to reuse such assignments / issuing conditions.

Furthermore, by relative allocation of audio objects to each other, greater flexibility is achieved in terms of scene handling. For example, the guitar should be timed with simultaneous steps. Moving the guitar 10 seconds into the future would automatically move the steps 10 seconds into the future, without having to change properties on the "step object".

According to the invention, both relative and variable constraints are used to test the violation of certain sound requirements on different systems. Thus, such an output condition is defined, for example, to the effect that the sound triggered by two audio objects A and B at a time t0 disturbs the listener with a maximum difference of e.g. B. t = 15 ms may reach. Then you position the audio objects A and B in the room. A test mechanism then checks the existing display area imposed by the wave field synthesis loudspeaker array for whether there are any positions which the issue condition is violated. Preferably, furthermore, the author of the sound scene is informed about this violation.

Depending on the implementation, the simulation device according to the invention can provide a pure indication of the situation of the output condition, ie whether or not it is injured and, where applicable, where it is injured and where not. However, the simulation device according to the invention is preferably designed not only to identify the problematic virtual sources, for example, but also to propose solutions to a processor. For example, using the example of the sound propaganda references, one solution would be to position the guitar and bass at those virtual positions that are only at a distance that is low enough that the wavefronts throughout the playback room actually arrive within the required difference determined by the output condition , In this case, the simulation device can use an iterative approach in which the sources are moved closer and closer to one another in a certain step size, in order then to see whether the output condition is now satisfied at previously problematic points in the reproduction space. So the "cost function" will be whether there are fewer issue condition violation points than in the previous iteration run.

For this purpose, the device according to the invention comprises a device for manipulating an audio object if the audio object violates the output condition. This manipulation can thus consist in an iterative manipulation in order to propose a positioning for the user.

Alternatively, the concept according to the invention with this manipulation device can also be used in wave-field synthesis processing in order to use a scene description to adapt it to the actual system Create schedule. This implementation is particularly preferred when the audio objects are not fixed in time and location, but in time and place is given a time span in which the audio object manipulation device is allowed to independently manipulate the audio objects without asking the sound engineer. Of course, according to the invention, care is taken in such a real-time simulation / processing that the output conditions are not violated even more by a shift within a time span or local span.

Alternatively, however, the apparatus of the invention may also operate off-line by writing from an audio scene description by audio object manipulation a schedule file based on the simulation results for different output conditions and then rendered in a wavefield synthesis system rather than the original audio scene description. The advantage of this implementation is that the audio file has been written without the intervention of the sound engineer, ie without the time and financial resources of a producer.

Subsequently, reference will be made to Fig. 2 pointed to information that should have an audio object advantageous. For example, an audio object should specify the audio file that effectively represents the audio content of a virtual source. However, the audio object does not need to include the audio file, but may have an index pointing to a defined location in a database where the actual audio file is stored.

Furthermore, an audio object preferably comprises an identification of the virtual source, which may be, for example, a source number or a meaningful file name, etc. Further, in the present invention, the audio object specifies a start and / or end time the virtual source, ie the audio file. Specifying only a time period for the start means that the actual starting point of the rendering of this file by the renderer can be changed within the time span. In addition, if a time limit is specified for the end, this also means that the end can also be varied within the time span, which, depending on the implementation, will generally lead to a variation of the audio file also in terms of its length. Any implementations are possible, such. For example, a definition of the start / end time of an audio file so that although the starting point may be moved, but in no case the length may be changed, so that automatically the end of the audio file is also moved. However, especially for noise, it is preferred to also keep the end variable, since it is typically not problematic whether z. For example, a wind noise starts sooner or later, or ends slightly earlier or later. Further specifications are possible or desired depending on the implementation, such as a specification, that although the starting point may be varied, but not the end point, etc.

Preferably, an audio object further comprises a location span for the position. So it will be irrelevant for certain audio objects, whether they z. B. come from the front left or front center, or if they are shifted by a (small) angle with respect to a reference point in the playback room. However, as has been said, audio objects, especially from the noise area, which can be positioned at any position and thus have a maximum spatial range, for example, by a code for "arbitrary" or by no code (implicit) in the Audio object can be specified.

An audio object may include other information, such as an indication of the nature of the virtual Source, that is, whether the virtual source must be a point source for sound waves, or whether it must be a source of plane waves, or whether it must be a source that generates sources of any wavefront, provided the renderers Modules are able to handle such information.

Fig. 3 shows by way of example a schematic representation of a scene description, in which the temporal sequence of different audio objects A01, .... AOn + 1 is shown. In particular, attention is drawn to the audio object A03, for which a period of time as shown in Fig. 3 is defined. Thus, both the start point and the end point of the audio object AO3 can be in Fig. 3 to be shifted by the time span. The definition of the audio object A03, however, is that the length must not be changed, but this can be set variably from audio object to audio object.

Thus, it can be seen that by shifting the audio object A03 in the positive temporal direction, a situation can be achieved in which the audio object A03 only begins after the audio object A02. If both audio objects are played on the same renderer, this measure avoids a short overlap 20 which otherwise might occur. If the audio object A03 in the prior art already had the audio object that would exceed the capacity of a renderer because of all the other audio objects to be processed on the renderer, such as audio object A02 and audio object AO1, without the present invention, a complete suppression of the audio object would take place A03, although the time span 20 was only very small. According to the audio object A03 is moved by the audio object manipulation device 3, so that no capacity overrun and thus no suppression of the audio object A03 takes place more.

In the preferred embodiment of the present invention, a scene description is used that has relative indications. Thus, the flexibility is increased by giving the beginning of the audio object A02 no longer at an absolute time, but in a relative time to the audio object AO1. Accordingly, a relative description of the location information is preferred, so not that an audio object is to be arranged at a certain position xy in the playback room, but z. B. is a vector offset to another audio object or to a reference object.

As a result, the time span information can be recorded very efficiently, namely simply by setting the time span such that it expresses that the audio object A03 has, for B. in a period between two minutes and two minutes and 20 seconds after the start of the audio object AO1 can begin.

Such a relative definition of the space and time conditions leads to a database efficient representation in the form of constraints, such as. In " Modeling Output Constraints in Multimedia Database Systems ", T. Heimrich, 11th International Multimedia Modeling Conference, IEEE, January 12, 2005 to January 14, 2005 , Melbourne, is described. It shows the use of constraints in database systems to define consistent database states. In particular, temporal constraints are described using Allen relationships and spatial constraints using spatial relationships. From this, favorable output constraints can be defined for synchronization purposes. Such output constraints include a temporal or spatial condition between the objects, a reaction in case of a violation of a constraint, and a verification time, ie when such a constraint needs to be checked.

In the preferred embodiment of the present invention, the spatial / temporal output objects of each scene are modeled relative to one another. The audio object manipulation device achieves a translation of these relative and variable definitions into an absolute spatial and temporal order. This order represents the output schedule which defines how, in particular, the renderer module is addressed in the wave-field synthesis system. The schedule is thus an output schedule that arranges the audio data according to the output conditions.

The following is based on Fig. 4 a preferred embodiment of such an output schedule set forth. In particular shows Fig. 4 a data stream according to Fig. 4 from left to right, that is, from an audio object manipulation device of one to one or more wave field synthesis renderers of a wavefield system. In particular, the data stream for each audio object in the in Fig. 4 In the embodiment shown, first a header H, in which the position information and the time information stand, and a subordinate audio file for the special audio object, which in Fig. 4 with AO1 for the first audio object, A02 for the second audio object, etc.

A wave field synthesis renderer then receives the data stream and detects z. B. to an existing and agreed synchronization information that now comes a header. Based on another synchronization information, the renderer then recognizes that the header is now over. Alternatively, a fixed length in bits can be agreed for each Haeder.

After receiving the header, the audio renderer knows the in Fig. 4 shown preferred embodiment of the present invention automatically that the subsequent audio file, ie, for. B. AO1, to the audio object, so to the Source location identified in the header.

Fig. 4 shows a serial data transfer to a wave field synthesis renderer. However, of course, several audio objects are played simultaneously in a renderer. Therefore, the renderer requires an input buffer preceded by a data stream reader to parse the data stream. The data stream reader will then interpret the header and store the associated audio data accordingly, so that when an audio object is to render, the renderer reads out the correct audio file and the correct source position from the input buffer. Other data for the data stream are of course possible. Also, a separate transmission of both the time / location information and the actual audio data may be used. In the Fig. 4 However, combined transfer shown is preferred because it eliminates data consistency problems by concatenating the position / time information with the audio file, since it always ensures that the audio renderer also has the correct source location, and not z. B. still renders audio from an earlier source, but already uses position information from the new source for rendering.

The present invention is thus based on an object-oriented approach, that is to say that the individual virtual sources are understood as objects which are distinguished by an audio file and a virtual position in space and possibly by the nature of the source, that is, if they are a point source for sound waves or a source of plane waves or a source of differently shaped sources.

As has been stated, the calculation of the wave fields is very computation-intensive and the capacities of the hardware used, such as sound cards and computers, in conjunction with the efficiency of the calculation algorithms bound. Even the best-equipped PC-based solution thus quickly reaches its limits in the calculation of wave field synthesis, when many sophisticated sound events are to be displayed simultaneously. Thus, the capacity limit of the software and hardware used dictates the limitation on the number of virtual sources in the mixdown and playback.

Fig. 6 shows such a limited in its known wave field synthesis concept that includes an authoring tool 60, a control renderer module 62, and an audio server 64, wherein the control renderer module is configured to provide a speaker array 66 with data for the speaker array 66 to generate a desired wavefront 68 by superimposing the single waves of the individual loudspeakers 70. The authoring tool 60 allows the user to create scenes, edit and control the wave field synthesis based system. A scene consists of information about the individual virtual audio sources as well as the audio data. The properties of the audio sources and the references to the audio data are stored in an XML scene file. The audio data itself is stored on the audio server 64 and transmitted from there to the renderer module. At the same time, the renderer module receives the control data from the authoring tool so that the control renderer module 62, which is centrally executed, can generate the synthesis signals for the individual loudspeakers. This in Fig. 6 shown concept is in " Authorization System for Wave Field Synthesis ", F. Melchior, T. Röder, S. Brix, S. Wabnik and C. Riegel, AES Convention Paper, 115th AES Assembly, October 10, 2003, New York s.

If this wave field synthesis system is operated with several renderer modules, each renderer is supplied with the same audio data, regardless of whether the renderer needs this data for playback or not because of the limited number of speakers assigned to it.

Since each of the current computers is capable of calculating 32 audio sources, this is the limit for the system. On the other hand, the number of renderable sources in the overall system should be significantly increased efficiently. This is one of the essential requirements for complex applications, such as movies, scenes with immersive atmospheres, such as rain or applause or other complex audio scenes.

According to the invention, a reduction of redundant data transfer operations and data processing operations in a wave field synthesis multi-renderer system is achieved, which leads to an increase in the computing capacity or the number of simultaneously computable audio sources.

To reduce the redundant transmission and processing of audio and metadata to the single renderer of the multi-renderer system, the audio server is extended by the data output device, which is able to determine which renderer needs which audio and metadata. The data output device, possibly supported by the data manager, requires a plurality of information in a preferred embodiment. This information is initially the audio data, then the source and position data of the sources, and finally the configuration of the renderers, that is, information about the connected speakers and their positions and their capacity. Using data management techniques and the definition of output conditions, an output schedule is generated by the data output device with a temporal and spatial arrangement of the audio objects. From the spatial arrangement, the time schedule and the renderer configuration, the data management module then calculates which source is relevant for which renderer at a particular time.

A preferred overall concept is in Fig. 5 shown. The database 22 is the output side to the data output device 24 supplemented, wherein the data output device is also referred to as a scheduler. This scheduler then generates at its outputs 20a, 20b, 20c for the various renderers 50 the renderer input signals in order to power the corresponding loudspeakers of the loudspeaker arrays.

Preferably, the scheduler 24 is still supported by a storage manager 52 in order to configure the database 22 by means of a RAID system and corresponding data organization specifications.

On the input side is a data generator 54, which may be, for example, a sound engineer or an audio engineer who is to model or describe an audio scene in an object-oriented manner. In this case, he provides a scene description that includes corresponding output conditions 56, which are then optionally stored in the database 22 together with audio data after a transformation 58. The audio data may be manipulated and updated using an insert / update tool 59.

Depending on the circumstances, the method according to the invention can be implemented in hardware or in software. The implementation may be on a digital storage medium, particularly a floppy disk or CD, with electronically readable control signals that may interact with a programmable computer system to perform the method. In general, the invention thus also consists in a computer program product with a program code stored on a machine-readable carrier for carrying out the method 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 runs on a computer.

Claims (17)

1. Apparatus for simulating a wave field synthesis system with respect to a reproduction room, in which one or more loudspeaker arrays, which can be coupled to a wave field synthesis rendering means, are attachable, comprising:

   a means (1) for providing an audio scene description defining a temporal sequence of audio objects, wherein an audio object comprises an audio file for a virtual source or a reference to the audio file and information on a source position of the virtual source, and wherein an output condition is given for the wave field synthesis system;

   a means (3) for simulating the behavior of the wave field synthesis system, using information on the wave field synthesis system and the audio files; and

   a means (4) for checking if the simulated behavior satisfies the output condition.
2. Apparatus according to claim 1, wherein the output condition defines a behavior of a sound field in the reproduction room,
   wherein the means for simulating is formed to simulate the sound field in the reproduction room, and
   wherein the means (4) for checking is formed to check if the simulated sound field satisfies the output condition in the reproduction room.
3. Apparatus according to claim 1, wherein the means (3) for simulating comprises:

   a wave field synthesis rendering means (3b) formed to generate synthesis signals from the audio scene description and from information on positions of the loudspeakers in the reproduction room; and

   a loudspeaker simulator (3c) for simulating the sound field generated by the loudspeakers, on the basis of the synthesis signals.
4. Apparatus according to one of the preceding claims,
   wherein the means (1) for providing is formed to provide an output condition comprising a defined property of a virtual source with respect to another virtual source,
   wherein the means (3) for simulating is formed to simulate a first sound field in the reproduction room due to a first virtual source without the other virtual source and also a second sound field in the reproduction room due to the other virtual source without the one virtual source, and
   wherein the means (4) for checking is formed to check the defined property on the basis of the first sound field and the second sound field.
5. Apparatus according to one of the preceding claims,
   wherein the means (3) for simulating is formed to simulate the sound field for various positions in the reproduction room, and
   wherein the means (4) for checking is formed to check the output condition for the various positions.
6. Apparatus according to one of the preceding claims, further comprising:

   a means for indicating (5e) whether and where the output condition is satisfied or not satisfied in the wave field synthesis system.
7. Apparatus according to one of the preceding claims, further comprising:

   a means for identifying (5f) which of the plurality of output conditions is host satisfied, and due to which virtual source of a plurality of virtual sources the output condition is violated.
8. Apparatus according to one of the preceding claims, wherein the output condition prescribes that a wave front due to a first virtual source and a wave front due to a second virtual source in the reproduction room must arrive within a predetermined time duration at a point in the reproduction room,
   wherein the means (3) for simulating is formed to calculate a time difference of the impingement of the wave front due to the first virtual source and the impingement of the wave front due to the second virtual source; and
   wherein the means (4) for checking is formed to compare the calculated time difference with the output condition.
9. Apparatus according to one of the preceding claims, further comprising:

   a means for manipulating an audio object if the audio object violates the output condition.
10. Apparatus according to claim 9, wherein the means for manipulating is formed to manipulate a virtual position of the audio object, a starting time instant or an end time instant, or mark the audio object in the audio scene as problematic, such that the audio object can be suppressed in the reproduction of the audio scene.
11. Apparatus according to one of the preceding claims, wherein the output condition defines a loudness difference between two virtual sources,
    wherein the means (3) for simulating is formed to determine a loudness difference of the two virtual sources at a location in the reproduction room, and
    wherein the means (4) for checking is formed to compare the determined loudness difference with the output condition.
12. Apparatus according to one of the preceding claims,
    wherein the output condition is a maximum number of audio objects to be processed by a wave field synthesis renderer means at the same time,
    wherein the means (3) for simulating is formed to determine a utilization of the wave field synthesis renderer means, and
    wherein the means (4) for checking is formed to compare a calculated utilization with the output condition.
13. Apparatus according to one of the preceding claims, wherein an audio object in the audio scene description defines a temporal start or a temporal end for an associated virtual source, wherein the audio object of the virtual source comprises a time span in which the start or the end must be, or comprises a location span in which a position of the virtual source must be.
14. Apparatus according to claim 13, further comprising:

    an audio object manipulation means for varying an actual starting point or end point of an audio object within the time span or an actual position of the virtual source within the location span in response to a violation of an output condition.
15. Apparatus according to claim 14, further formed to examine if a violation of an output condition can be remedied by the variation of the audio object within the time span or location span.
16. Method of simulating a wave field synthesis system with respect to the reproduction room, in which one or more loudspeaker arrays, which can be coupled to a wave field synthesis rendering means, are attachable, comprising:

    providing (1) an audio scene description defining a temporal sequence of audio objects, wherein an audio object comprises an audio file for a virtual source or a reference to the audio file and information on a source position of the virtual source, and wherein an output condition is given for the wave field synthesis system;

    simulating (3) the behavior of the wave field synthesis system, using information on the wave field synthesis system and the audio files; and

    checking (4) if the simulated behavior satisfies the output condition.
17. Computer program with program code for performing the method of simulating a wave field synthesis system according to claim 16, when the program is executed on a computer.

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