FR2922404A1 - Audio environment i.e. surround audio environment, creating method for e.g. home theater type audio-visual or audiophonic private room, involves generating audio signal for loudspeaker such that signal is dependent on theoretical signals - Google Patents

Abstract

The method involves identifying two theoretical loudspeakers (HPT2, HPT3), which are nearest to a loudspeaker (HP1). A relative position reflecting data of the loud speaker is determined with respect to the theoretical loudspeaker (HPT2). Another relative position reflecting data of the loud speaker is determined with respect to the theoretical loudspeaker (HPT3). An audio signal supplied to the loudspeaker is generated such that the signal is dependent on the data and theoretical signals supplied to the theoretical speakers. An independent claim is also included for a system for creating an audio environment with speakers.

Description

The invention relates to a method and a system for creating an audio environment. More particularly, it makes it possible to create an audio environment with N loudspeakers fed by signals generated from M signals derived from information encoded on a medium.

The invention will find particular application in the field of audiovisual rooms and audio rooms and more particularly in the field of private or non-professional audio-visual rooms or home theater type. As is known, the rendering of an audio environment in a home theater-type room is effected by supplying loudspeakers with signals carrying audio information. These signals are obtained by decoding a content stored on a medium such as a CDROM or DVD etc. This content results itself from the compression and encoding of audio data reflecting the original sound environment that we want to restore. Encoding and decoding are usually carried out according to widely used technologies such as technologies designated by 5.1 and 7.1 formats. These technologies make it possible to create a distributed audio environment around a person. Such an environment is usually called surround. These technologies respectively allow to supply five speakers plus a subwoofer and seven speakers plus a subwoofer distributed in a circle in the center of which the person is intended to be positioned. A system respecting the 5.1 format recommendations is shown in Figure 2. According to these technologies each loudspeaker is powered by a separate signal through a separate channel. Thus, these 25 technologies are described as multi-channel. Systems operating according to technologies of type 5.1 or 7.1 have many disadvantages. Indeed, to obtain a satisfactory quality, it is advisable to respect the number of loudspeakers as well as the position of each of the loudspeakers as recommended by the encoding format. For example, for audio content encoded according to the 5.1 format, a sound environment reproduction system must be equipped with five speakers and a subwoofer, the five loudspeakers being imperatively arranged as follows: - at the front of the person and successively arranged from left to right: a front left speaker, a center speaker, a front right speaker - in the back of the person arranged from the left towards right: a left rear speaker and a right rear speaker. In addition, each loudspeaker must be carefully positioned angularly in particular to obtain a satisfactory audio reproduction. To improve the quality of the rendering of an audio environment it is necessary to increase the number of sources reflecting this environment. However, if two speakers arranged at different locations emit the same sound reflecting in the original environment the same source, this results in a location error resulting in a significant degradation of the quality of the audio environment. returned. It has been proposed solutions to record on the same medium several audio contents encoded in different formats. Thus a user can select the decoding format that corresponds to his rendering system. Such a solution generates a substantial increase in the amount of information that must be recorded for a given environment. It therefore limits the size of the content that the same medium can carry for a given sound environment. Moreover solutions have been proposed to increase the number of channels while providing each speaker a separate signal. However, these solutions imply at least to change the encoding format so as to record additional channels on the medium. In addition, these solutions do not make it possible to increase the number of channels in a truly significant manner. In addition, these solutions require very precise positioning of the various loudspeakers. These speaker positioning constraints are particularly damaging in private and non-professional rooms. Indeed, the size, the configuration, the furniture and the presence of doors or windows can considerably limit the possibilities of respecting the recommendations of conventional encoding formats.

Therefore, it would be particularly valuable to be able to render a quality audio environment from speakers whose number and location are not imposed by the encoding format of the audio content.

For this purpose there is provided according to the invention a method for creating an audio environment with N loudspeakers HP ;, i = 1 ... N powered by N audio signals Si, i = 1 ... N generated from M theoretical audio signals STj, j-1 ... M intended to feed M theoretical speakers HPTj, j = 1 ... M, the positioning of each of the theoretical speakers HPTj with respect to the assumed location io a person for whom the audio environment is created being predetermined, in which each HP loudspeaker is positioned; and for each HP speaker; the two theoretical speakers HPTj and HPTj + 1, which would be the closest to the loudspeaker HP, are identified; a data item d is determined; reflecting the relative position of the HP speaker; relative to the theoretical loudspeaker HPTj, - a data d +1 is determined, reflecting the relative position of the loudspeaker HP; relative to the theoretical loudspeaker HPTj + 1, a signal Si is generated for supplying the loudspeaker HP; so that Si is dependent on the data d; and d; +1 as well as theoretical signals Si and Sj + 1 provided for respectively supplying the theoretical loudspeakers HPTj and HPTj + 1. Thus, the invention makes it possible to create a surround-like audio environment with loudspeakers whose number and location are not conditioned by the encoding format of the audio content. In addition, each speaker reproduces a single signal. Therefore, the invention makes it possible to create a substantially improved quality audio environment over existing systems. In addition, it makes it possible to considerably reduce the stresses imposed by the latter. The invention may further optionally have at least one of the following features: the signal Si is proportional to the expression: Si x d '+ ~ + S; +1 xd '+ d ~ + 1 + d di di j + l _ prior to the identification of the theoretical loudspeakers HPTj and HPTj + 1 the position of the loudspeaker HPi is determined, - to obtain the data di and di +1 the coordinates of the theoretical loudspeakers HPTj and HPTj + 1 and the loudspeaker HPi are determined, - the data di and di + 1 are the angular distances separating the loudspeaker HPi respectively from the theoretical loudspeaker HPTj and from the top theoretical speaker HPTj + 1 taken on a circle or a sphere centered on said location, - the coordinates are two-dimensional or three-dimensional coordinates expressed in a cartesian or trigonometric coordinate system, - the processor determines the data di and di + 1 and generates for each loudspeaker HPi the signal Si, - for each loudspeaker HPi is determined the distance of the latter relative to a mean circle centered on the presumed location of said person and passing through the theoretical position of the M high- PARLEU In theory, the distance of each speaker HPi from the speaker HPi, which is disposed closest to the presumed location of said person, is determined. The signal Si is then processed so that it takes into account said distance so that said person receives at each instant t the set of signals Si, i = 1 ... N generated by combining the theoretical signals STj, j = 1 ... M provided to achieve said person at the same time t, the signal Si is processed so that it takes into account said distance so that said person receives at each instant t all the signals Si generated by the theoretical signals STj provided for to reach the person at time t, - the number N of speakers HPi is greater than the number M of theoretical speakers.

In addition, a system for creating an audio environment with N loudspeakers HPi, i = 1 ... N fed by N audio signals Si, i = 1 ... N generated from M is also provided according to the invention. theoretical audio signals Si, j = 1 ... M intended to supply M theoretical speakers HPi, j = 1 ... M whose positionings with respect to the location of a person for whom the audio environment is are predetermined, characterized in that it comprises a processor arranged to generate for each speaker HPi a signal-dependent signal Si di and di + 1 as well as theoretical signals Si and Sj + 1, the theoretical signals Si and Sj + 1 being the theoretical signals provided for respectively powering the theoretical loudspeakers HPTj and HPTj + 1 identified as being the closest to the speaker HPi, - the data di reflecting the relative position of the speaker HPi relative to the theoretical loudspeaker HPTj, - the data di + 1 reflective As the relative position of the loudspeaker HPi 20 relative to the theoretical loudspeaker HPTj + 1. The accompanying drawings are given by way of example and are not limiting of the invention. They represent only one embodiment of the invention and will make it easy to understand. FIG. 1 is a block diagram of a known system making it possible to create an audio environment; FIG. 2 is a simplified diagram of a known system equipping a type 5.1 installation; FIG. 3 is a block diagram of FIG. A system according to an exemplary embodiment of the invention. FIG. 4 is a simplified diagram of a system according to an example embodiment of the invention.

Referring to Figure 1 there is shown a known system for creating an audio environment from a content encoded in a type 5.1 format. In a known manner, in such a system, the content recorded on a medium 1 or medium is decoded by a decoder 2. The medium may be, for example, a DVD, a CDROM, a memory, a hard disk or any other medium making it possible to store data. digital information. The decoder 2 has at its output six channels (FL, C, FR, RL, RR, S) on which a signal is respectively transmitted. The FL, C, FR, RL and RR channels are respectively connected to the speakers HPFL, HPc, HPFR, HPRL, HPRR. The S channel is connected to the subwoofer SB. A known system for creating an audio environment from 5.1 format encoded content is shown in FIG. 2. Thus the speakers HPc, HPFR, HPRR, HPRL and HPFL are shown and are respectively referenced HPT1, HPT2 , HPT3, HPT4, HPT5. The subwoofer is not shown. Each loudspeaker is arranged in accordance with the 5.1 format recommendations. Thus, if the person for whom the surround sound environment is created is located at the center of the circle C and oriented along the X axis, each of the loudspeakers must be positioned on the circle and at a precise angle. As indicated above, the known systems do not allow to freely adjust the number and position of the speakers used. They therefore prove to be substantially restrictive especially for installations in private rooms where the positioning constraints related to the dimensions and decor are strict. FIG. 3 represents a block diagram of an exemplary embodiment of a system according to the invention. The system comprises a DSP digital signal processor 20, HP speakers, i = 1 ... N and channels connecting the DSP 20 to the HP speakers; i = 1 ... N. The DSP 20 includes a decoder 21 adapted to decode digital data contained on a support 10. The decoder 21 is of conventional type. Therefore the invention does not require modification of the current methods of encoding and remains fully compatible with all existing media. The DSP 20 also comprises processing means 22 arranged so as to generate as many separate signals Si, i = 1 ... N as of channels connected to the speakers HPi, i = 1 ... N. The DSP receives as input digital data from the support 1 and after processing delivers, at the output, the signals Si, i = 1 ... N. The signals Si are generated by combining the signals decoded by the decoder 21 from the content recorded on the medium 10. The processing means 22 are configured to take into account the location of each speaker HPi to generate each signal Si In the remainder of the description, it is considered that for each channel there is only one speaker HPi, i = 1 ... N. Each speaker HPi, i = 1 ... N is thus powered by a single signal and therefore delivers a single sound at a given time. It should be noted, however, that in practice several HPi loudspeakers may be arranged on the same designated support. More precisely, the signals Si are generated in the following manner: - after having freely positioned the speakers HPi, data is determined relating to the position of each HPi speaker. These data are, for example, the coordinates of each of the speakers HPi expressed in a Cartesian reference frame in two or three dimensions or in a trigonometric reference frame in two or three dimensions. It is understandable that the more precisely the location of the speakers is appreciated, the better the quality of the reproduced audio environment. Thus, the determination of the coordinates of the loudspeakers in a three-dimensional reference is advantageous compared to a reference in two dimensions. Figure 4 is a diagram of a system according to the invention in which the positions of the loudspeakers are identified in a two-dimensional trigonometric marker. This determination of the data can be performed during the installation of the system and manually or automatically through sensors arranged on each speaker HPi. These data are transmitted to the DSP. This transmission can be performed manually by means of an interface such as a keyboard or by automatic input means associated with the sensor. - The DSP is provided secondary data characterizing the position of the speakers that should have been positioned to meet the recommendations of the encoding format. These secondary data can also be coordinates expressed in a Cartesian or trigonometric coordinate system. In this example for which the decoding format is of type 5.1, it would thus be necessary to provide the DSP with all the coordinates of the central loudspeakers, right front, right rear, left rear, front left and the subwoofer. These loudspeakers are hereafter referred to as theoretical loudspeakers since their position is dictated by the encoding / decoding format and must be determined accurately. The theoretical loudspeakers are shown in dashed lines in FIG. 4 and are referenced HPTi, with j = 1 ... M. In this exemplary embodiment, the encoding / decoding format is of type 5.1, M is therefore equal to 5. Each theoretical speaker HPTi is intended to be supplied with a signal derived from the decoding of the information carried by the medium. and designated theoretical signal STE, with j = 1 ... M. a theoretical circle is determined around which the theoretical HPTi loudspeakers should have been placed to respect the recommendations of the encoding format. The determination of this circle, designated theoretical circle 20 is performed by the DSP. The center of this circle is the presumed location of the person for whom the surround sound environment is being reproduced. - for each HP speaker; the DSP identifies the two theoretical HPTi and HPTi + 1 speakers that would be located closest to the 25 HP speaker; if they were present. The two theoretical speakers HPTi and HPTi + 1 are determined so that they are located on either side of the line passing through the loudspeaker HP; and the alleged location of the person for whom the surround sound environment is being reproduced. These two theoretical speakers HPTi and HPTi + 1 are thus qualified as adjacent. For example the 30 loudspeakers HP1 and HP2 would be associated with the theoretical speakers HPT2 and HPT3; the speaker HP3 would be associated with the theoretical speakers HPT3 and HPT4; the speaker HP4 would be associated with the theoretical speakers HPT4 and HPT5, the speaker HP5 would be associated with the theoretical speakers HPT5 and HPT1. the DSP generates the signal Si by combining the signal STE of each of the speakers HPTi adjacent to the loudspeaker HP; receiving the signal Si.

The proportion of each signal STE in the signal Si depends on the relative position between the loudspeaker HP; and the theoretical speaker HPTi associated with this theoretical signal STE. Thus the proportion of each theoretical signal STE is adjusted so that the person for whom the audio environment is created has the perception that an audio source is located at the same location as in the conventional installation arranged in accordance with the recommendations of the decoding format. Thus the loudspeaker HP1 which is equidistant from the theoretical speakers HPT2 and HPT3 receives a signal Si whose proportion of the signal ST2 corresponding to the theoretical loudspeaker HPT2 is identical to the proportion of the signal ST3 corresponding to the loudspeaker. theoretical speaker HPT3. In Figure 4, the angles 91_2 and 91_3 are indeed equal. The loudspeaker HP4 whose distance to the theoretical speaker HPT5 is half of that separating it from the theoretical loudspeaker HPT4 receives a signal S4 whose proportion of the signal ST5 corresponding to the theoretical loudspeaker HPT5 and half of the proportion of the signal ST4 corresponding to the theoretical loudspeaker HPT4. In Figure 4, the angle 94_4 is indeed half the angle 94_5. If an HP speaker; is positioned in place of a theoretical HPTi speaker then this HP speaker; will receive for signal If the signal STE 25 corresponding to this theoretical speaker HPTi. Preferably the relative position is assessed angularly, that is to say that it is determined by considering the position of a loudspeaker HP; after projection of this position on the theoretical circle. For example, the speaker HP6, after projection on the theoretical circle would occupy the place of the speaker 30 HPT1. It would thus be associated with the theoretical loudspeaker HPT1 only and receive the signal ST1. In a three-dimensional reference, the DSP determines a sphere from the theoretical circle and determines the angular distance on that sphere between each speaker HP; and the theoretical speakers HPT;

The processing means 22 generate the signal Si so that this signal is proportional to the expression: Si x d '+ 1 + Si +1 x d' + dj + 1 d. + D. in which :

Si and S +1 are the theoretical audio signals provided for respectively powering the theoretical speakers HPi and HPi + 1 adjacent to the HP speaker.

di and di + 1 are the distances respectively separating each of the theoretical loudspeakers HPi and HPi + 1 from the speakers HP; Preferentially,

15 distances di and di + 1 are angular distances taken on a circle if the reference considered is in two dimensions, or taken on a sphere if the reference considered is in three dimensions, the circle and the sphere having for center the presumed localization of the person for whom the surround sound environment is being reproduced.

20 If the layout of an HP speaker; does not allow to determine only two theoretical speakers then this expression will be easily adapted so that the signal Si takes into account the theoretical signals of each of the adjacent theoretical speakers, the proportion of each of these theoretical signals being weighted by the angular distance

25 taken on a circle centered on said person between the theoretical speaker with which it is associated and the loudspeaker HP;

In practice, the DSP attenuates the original signals of each of the theoretical speakers adjacent to an HP speaker; given and adds them up. By thus remixing the theoretical signals STE coming from the decoding the

DSP can generate a very large number of signals. Thus, the tests carried out made it possible to carry out installations the number of channels of which was increased to 32, 64 and even 128. FIG. 3 thus represents a system with 128 channels connected respectively to a loudspeaker HP1 to HP128. The invention thus makes it possible to significantly increase the number of channels compared to existing systems which usually have six or eight channels. The invention thus makes it possible to distribute the total power of the system over a much larger number of loudspeakers. It thus allows to equip the same room with less powerful speakers so much better quality speakers used in known systems while maintaining for the entire system the same power. Moreover, the invention makes the inconvenience caused by a faulty loudspeaker much less prejudicial since the perception of this loudspeaker is of little importance with regard to the audio environment created by the other loudspeakers. Indeed, the perception of a speaker not working is rendered almost undetectable in an installation equipped with a large number of speakers. In addition, the quality of the audio environment created is free from disruption related to location errors since each HP speaker; is powered by a specific signal. Thus the same sound is reproduced only at one location. The invention makes it possible to position each loudspeaker freely, taking into account the constraints related to the dimensions, the decor and the furniture of a room. The Si signals generated by the DSP take into account the position of each HP speaker; in order to reposition the source perceived by the person at the same location as in the original audio environment. In the exemplary embodiment shown in FIG. 4, only a few loudspeakers have been shown. In this figure, all the theoretical loudspeakers have been positioned according to the recommendations of a conventional format of type 5.1. Preferably, in addition to taking into account the angular position of the loudspeakers to determine the proportion of each theoretical signal Si in each signal Si, the DSP also takes into consideration the distance of each speaker HP; relative to the person for whom the surround sound environment is recreated. The DSP makes it possible to simulate the distance of a source. For this purpose, each signal Si is subject to a time adjustment designated delay. The DSP thus makes it possible to reconstruct a perfectly circular surround sound environment centered on said person.

The original audio environment is mixed before encoding considering that the 5 + 1 (or 7 + 1 according to the format of encoding / decoding) speakers will be arranged on a perfect circle during the restitution. All these speakers will therefore be located at the same distance from said person. An HPi loudspeaker positioned at a different distance from the other speakers HPi i = 1..N can be acoustically reduced by time adjustment by applying a delay. This delay can be positive or negative depending on whether the loudspeaker is located inside or outside the perfect circle on which the other speakers are arranged. This delay is calculated by taking into account the speed of propagation of the sound so that the person receives at a time t the set of signals reflecting the original audio environment taken at the same time t. The signal to be sent to each loudspeaker is first stored in the digital domain before being released and transmitted to the loudspeaker after a time equal to the delay and controlled by a clock of the DSP.

For this purpose, the DSP uses the coordinates of the speakers HPi to determine a circle if one operates in a reference in two dimensions or to determine a sphere if one operates in a reference in three dimensions. The DSP then calculates the distance of each speaker HPi from the circle or the sphere. As a function of this distance and the speed of propagation of the sound, he deduces a positive or negative delay to be applied to the signal Si. One can choose to determine the circle or the sphere so that their respective radius is equal to the distance between the nearest HPi speaker and the presumed location of the person for whom the surround sound environment is being reproduced.

This repositioning of each speaker can be performed with great finesse if the delay itself is determined accurately. For this purpose, the DSP according to the invention is equipped with a very high-precision clock for repositioning each speaker HP; to the nearest millimeter, which corresponds to a time adjustment of the order of the microsecond. The DSP is also arranged to ensure perfect synchronization between the different signals Si.

The signal processing operated by the DSP thus makes it possible to provide a mixed signal Si so that the person has the impression that the audio source reproduced by the speaker HP; comes from the same location as the audio source that would have been reproduced by the theoretical HPTi and HPTi + 1 speakers adjacent to the HP speaker. Similarly, the Si and S signals +1 of the neighboring HP speakers; and HP; +1 allow to recompose a virtual speaker positioned in the same place as a theoretical speaker HPi respecting the recommendations of the encoding format. In addition the system allows to take into account the parameters specific to each HP speaker. These settings include the built-in filter for each HP speaker; usually designated by its English equivalent built-in crossover or crossover. This filter influences the time adjustment as well as the mixing of each signal Si from the theoretical signals STE coming from the decoding. Very often a loudspeaker has several channels, means of reproduction and amplification means respectively for splitting the received signal into several frequency ranges respectively corresponding to one of said channels and amplifying the signals from this filtering and feeding each of the channels. Each of the channels is arranged to reproduce accurately a sound corresponding to one of the frequency ranges.

The invention makes it possible to adjust these signals temporally by applying a delay to these means of restitution and / or these amplification means. In addition, it makes it possible to apply an additional group delay induced by the crossover and to take into account this additional delay to reposition acoustically each speaker HP; on the surround circle to temporally adjust each HP speaker; Thus the invention makes it possible to increase the number of channels and to generate signals taking into account the precise position of the loudspeakers associated with these channels. The result is a surround sound environment in which the position of each of the sources is reflected with significantly improved accuracy. The invention thus makes it possible to overcome the constraints related to the size and décor of the room in which the audio environment is reproduced. The present invention is not limited to the embodiments described above but extends to any embodiment within its spirit. 10

Claims (13)

1. Method for creating an audio environment with N loudspeakers HPi, i = 1 ... N (HP1, HP2, HP3, HP4, HP5, HP6) powered by N audio signals Si, i = 1 ... N generated from M theoretical audio signals STj, j = 1 ... M intended to supply M theoretical speakers HPTj, j = 1 ... M (HPT1, HPT2, HPT3, HPT4, HPT5), the positioning of each of the theoretical speakers HPTj with respect to a presumed location of a person for whom the audio environment is created being predetermined, in which each speaker HPi is positioned and for each speaker HPi: it identifies the two speakers theoretical HPTj and HPTj + 1 that would be closest to the speaker HPi, - a data di is determined reflecting the relative position of the speaker HPi with respect to the theoretical speaker HPTj, - a di + 1 reflecting data is determined the relative position of the speaker HPi with respect to the theoretical loudspeaker HPTj + 1, an Si signal is generated for to supply the speaker HPi so that Si is dependent on the data di and di + 1 as well as theoretical signals Si and Sj + 1 provided for respectively supplying the theoretical loudspeakers HPTj and HPTj + 1. 2. Method according to the preceding claim, characterized in that the signal Si is proportional to the expression: Si x d '+ ~ + S; +1 x + d + 1 + d + 3. Method according to any one of the preceding claims, characterized in that prior to the identification of the theoretical loudspeakers HPTj and HPTj + 1 is determined the position of speaker HPi. 4. Method according to any one of the preceding claims, characterized in that to obtain the data di and di + 1 are determined thecoordonnations of the theoretical speakers HPTi and HPTi + 1 and HPi loudspeaker. 5. Method according to the preceding claim, characterized in that the data di and di + 1 are the angular distances separating the loudspeaker HPi respectively from the theoretical speaker HPTi and the theoretical speaker H PTE + 1. 6. Method according to the preceding claim, characterized in that the io coordinates are two-dimensional or three-dimensional coordinates expressed in a Cartesian or trigonometric coordinate system. 7. Method according to any one of the preceding claims, characterized in that the processor determines the data di and di + 1 and generates for each loudspeaker HPi the signal Si. 8. Method according to any one of the preceding claims, characterized in that for each HPi speaker is determined the distance from the latter with respect to a middle circle centered on the presumed location 20 of said person and passing through the theoretical position of the HPTi M theoretical loudspeakers. 9. Method according to any one of claims 1 to 7, characterized in that it determines the distance of each speaker HPi from the HPi speaker, disposed closest to the presumed location of said nobody. 10. Method according to any one of the two preceding claims, characterized in that the signal Si is processed so that said distance is taken into account so that said person receives at all times the set of signals. If, i = 1 ... N generated by combining the theoretical signals STE, i = 1 ... M expected to reach said person at this same time t. 11. Method according to any one of the preceding claims, characterized in that the number N of HPi speakers is greater than the number M of theoretical speakers. 12. System for creating an audio environment with N loudspeakers HPi, i = 1 ... N (HP1, HP2, HP3, HP4, HP5, HP6) powered by N audio signals Si, i = 1 ... N generated from M theoretical audio signals STj, j = 1 ... M provided for supplying M theoretical speakers HPTj, j = 1 ... M (HPT1, HPT2, HPT3, HPT4, HPT5), whose positioning relative to at the presumed location of a person for whom the audio environment is created are predetermined, characterized in that it comprises a processor arranged to generate for each speaker HPi a signal Si dependent on data di and di +1 as well as theoretical signals Si and Si + 1, the theoretical signals Si and Sj + 1 being the theoretical signals intended to respectively supply the theoretical loudspeakers HPTj and HPTj + 1 identified as being the closest to the loudspeaker HPi, the data di reflecting the relative position of the speaker HPi with respect to the theoretical speaker HPTj, the data di + 1 reflecting the relative position of the speaker HPi with respect to the theoretical loudspeaker HPTj + 1. 13. System according to the preceding claim, characterized in that it comprises N loudspeakers, N being greater than M.