The present invention generally pertains to music spatialisation. More specifically, the present invention relates to a music spatialisation system and a music spatialisation method which take account of the positions of different sound sources with respect to a listener for controlling the spatial characteristics of a music produced by the sound sources.
Several music spatialisation systems are known in the art. Most of them simulate, by way of a software, acoustic environments for existing sound signals. These systems are based on results in psychoacoustics that allow to model the perception of sound sources by the human ear using a limited number of perceptive parameters. The models have led to techniques allowing to recreate impression of sound localisation using a limited number of loudspeakers. These techniques typically exploit difference of amplitude in sound channels, delays between sound channels to account for interaural distances, and sound filtering techniques such as reverberation to recreate impressions of distance.
The spatialisation system xe2x80x9cSPATxe2x80x9d (registered trademark) by the IRCAM (Institut de Recherche et Coordination Acoustique/Musique) is a virtual acoustic processor that allows to define the sound scene as a set of perceptive factors such as azimuth, elevation and orientation angles of sound sources relatively to the listener. This processor can adapt itself to a sound reproduction device, such as headphones, pairs of loudspeakers, or collections of loudspeakers, for reproducing a music based on these perceptive factors.
The above-mentioned spatialisation techniques have the drawback that the consistency of music is not always maintained upon changing the spatial characteristics of the music.
The present invention aims at remedying this drawback, and providing a system which enables to modify in real-time the positions of various sound sources and a listener in a sound scene, thereby modifying the spatial characteristics of the music produced by the sound sources, while maintaining consistency of the music.
For this purpose there is provided a system for controlling a music spatialisation unit, characterised in that it comprises:
storage means for storing data representative of one or several sound sources and a listener of said sound sources, said data comprising position data corresponding to respective positions of the sound sources and the listener,
interface means for enabling a user to select the listener or a sound source and to control a chance in the position data corresponding to the selected listener or sound source,
constraint solver means for changing, in response to the position data change controlled by the user, at least some of the position data corresponding to the element(s), among the listener and the sound sources, other than said selected listener or sound source, in accordance with predetermined constraints, and
means for delivering control data exploitable by a music spatialisation unit as a function of the position data corresponding to the sound sources and the listener.
Thus, according to the present invention, predetermined constraints are imposed on the positions of the listener and/or the sound sources in the sound scene. Thanks to these constraints, desired properties for the music produced by the sound sources can be preserved, even, for instance, after the position of a sound source has been modified by the user.
Typically, the music spatialisation unit is a remote controllable mixing device for mixing musical data representative of music pieces respectively produced by the sound sources.
Preferably, the interface means comprises a graphical interface for providing a graphical representation of the listener and the sound sources, and means for moving the listener and/or the sound sources in said graphical representation in response to the position data change controlled by the user and/or the position data change(s) performed by the constraint solver means.
Advantageously, the interface means further comprises means for enabling the user to selectively activate or deactivate the predetermined constraints. The constraint solver means then takes account only of the constraints that have been activated by the user.
In order to render the system according to the present invention immediately reactive, the interface means also comprises means for sampling the position data change controlled by the user into elementary position data changes and for activating the constraint solver means each time an elementary position change has been controlled by the user.
Typically, the predetermined constraints comprise at least one of the following constraints: a constraint specifying that the respective distances between two given sound sources and the listener should always remain in the same ratio; a constraint specifying that the product of the respective distances between each sound source and the listener should always remain constant; a constraint specifying that a given sound source should not cross a predetermined radial limit with respect to the listener; and a constraint specifying that a given sound source should not cross a predetermined angular limit with respect to the listener.
Typically, the constraint solver means performs a constraint propagation algorithm having said position data as variables for changing said at least some of the position data. According to the present invention, the constraint propagation algorithm is a recursive algorithm wherein:
inequality constraints are merely checked;
for each functional constraint, in response to a change in the value of one of the variables involved by the constraint, the other variables involved by the constraint are given arbitrary values such that the constraint be satisfied;
a variable that has been given an arbitrary value at a given step of the algorithm will not change value at any further step thereof; and
if, at a given step of the algorithm, an inequality constraint is not satisfied, or a functional constraint cannot be satisfied in view of an arbitrary value previously given to one of its variables, the algorithm is ended and the position data change controlled by the user is refused.
The control data depend on the position of each sound source with respect to the listener. More specifically, the control data comprise, for each sound source: a volume parameter depending on the distance between said each sound source and the listener, and a panoramic parameter depending on an angular position of said each sound source with respect to the listener.
The present invention further relates to a music spatialisation system for controlling the spatial characteristics of a music produced by one or several sound sources, characterised in that it comprises: a system as defined above for producing control data depending on the respective positions of the sound sources and a listener of said sound sources, and a spatialisation unit for mixing predetermined musical data representative of music pieces respectively produced by the sound sources as a function of said control data.
The music spatialisation system can further comprise a sound reproducing device for reproducing the mixed musical data produced by the spatialisation unit.
The present invention further relates to a method for controlling a music spatialisation unit, characterised in that it comprises the following steps:
storing data representative of one or several sound sources and a listener of said sound sources, said data comprising position data corresponding to respective positions of the sound sources and the listener,
enabling a user to select the listener or a sound source and to control a change in the position data corresponding to the selected listener or sound source through an interface means,
changing, in response to the position data change controlled by the user, at least some of the position data corresponding to the element(s), among the listener and the sound sources, other than said selected listener or sound source, in accordance with predetermined constraints, and
delivering control data exploitable by a music spatialisation unit as a function of the position data corresponding to the sound sources and the listener.
The present invention further relates to a music spatialisation method for controlling the spatial characteristics of a music produced by one or several sound sources, characterised in that it comprises:
a method as defined above for producing control data depending on the respective positions of the sound sources and a listener of said sound sources, and
a spatialisation step for mixing predetermined musical data representative of music pieces respectively produced by said sound sources as a function of said control data.
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