WO2014032709A1

WO2014032709A1 - Audio rendering system

Info

Publication number: WO2014032709A1
Application number: PCT/EP2012/066775
Authority: WO
Inventors: Yue Lang; David Virette
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2012-08-29
Filing date: 2012-08-29
Publication date: 2014-03-06
Also published as: EP2823650A1; EP2823650B1

Abstract

The invention relates to an audio rendering system(100) for audio rendering room acoustics, comprising: a plurality of loudspeakers (101); a mobile device (105) comprising at least two microphones (107), the mobile device (105) being located at a room position of a user (109) using the mobile device (105); and a control device (103) coupled to the plurality of loudspeakers (101) and coupled to the mobile device (105), wherein the control device (103) is configured to calibrate the audio rendering system (100) based on the room position of the user (109) and on room positions of the loudspeakers(101) by evaluating information of the at least two microphones (107) of the mobile device (105).

Description

DESCRIPTION

Audio rendering system BACKGROUND OF THE INVENTION

The present invention relates to an audio rendering system, in particular a stereo or multichannel rendering system for rendering room acoustics, a method for calibrating an audio rendering system and a portable electronic device, in particular a Smartphone or a Tablet PC usable for calibration of an audio rendering system.

The optimization of loudspeaker and/or room rendering is a technology which aims at improving and/or correcting the audio rendering of non-standard loudspeaker layouts. Some examples of such optimization can be found in JP2000261900, FR2850183 and EP2378795. The methods are based on adaptive modifications, i.e. filtering, gain, delay, equalization, etc. of the audio signal computed and applied for each channel which are used for the optimization of the rendering. The adaptation of the rendering is usually based on the measurement of the audio signal which is actually received at the listening position. This optimal position is usually called the "sweet spot". This can be done by a directional microphone system, i.e. at least a stereo microphone which aims at detecting the position of the loudspeaker and then provides the necessary information for the adaptation of the rendering. Those methods can be applied to a multichannel audio rendering system, i.e. an audio rendering system having at least two and more channels like a 5.1 , 7.1 , 10.2 or 22.2 system. In prior art, calibration systems are automatic and are not controlled by the user and do not give any freedom to the user for the adaptation. For multichannel audio rendering, the loudspeaker positions are usually standardized in order to have an optimized rendering for this loudspeaker layout. Figure 9 illustrates a 5.1 multichannel loudspeaker system 900 according to the recommendation ITU-R BS 775-1. Three front loudspeakers (left L, center C, right R) are combined with two rear/side loudspeakers (left surround L_s, right surround R_s). The left and right frontal loudspeakers are placed at the extremities of an arc subtending 60° at the reference listening point 901. For reasons of available space, it is preferred to place the frontal loudspeakers L, C, R on a straight line base, then it may be necessary to introduce compensating time delays in the signal feed of the center loudspeaker C. Both side/rear loudspeakers L_s, Rs should be placed within the sectors from 100° to 120° from the center front reference. Precise location is not necessary. Side/rear loudspeakers should be not closer to the listener than the frontal loudspeakers, unless compensating time delay is introduced. The frontal loudspeakers should ideally be at a height approximately equal to that of the listener's ears.

However, in practical applications, it is often difficult to strictly follow the standardized loudspeaker layout due to non-compatible dimensions of the room or other external constraints. Figure 10 illustrates a non-standardized 5.1 multichannel loudspeaker system 1000 which requires rendering adaptation and correction.

The three front loudspeakers L, C, R are not placed on a straight line base and the two rear/side loudspeakers L_s, Rs are located in different distances from the reference listening point 1001 . Both side/rear loudspeakers L_s, Rs are not placed within the sectors from 100° to 120° from the center front reference. The left and right frontal loudspeakers are not placed at the extremities of the arc subtending 60° at the reference listening point 1001 .

Conventional rendering adaptation systems are based on the configuration depicted in Figure 9, i.e. they can only adapt the rendering to the listening position, i.e. the sweet spot 901 . They cannot be controlled by the user or give any freedom to the user for the adaptation. A calibration process with a dedicated system does not allow an easy and dynamic calibration as it is based on a dedicated microphone and calibration is thus inflexible.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a concept for an audio rendering system providing a flexible and adaptive multi-loudspeaker calibration.

This object is achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures. The invention is based on the finding that by using the available microphones (two or more) of a mobile device, e.g. a mobile device 1 100 depicted in Fig. 1 1 or any other mobile device like a Smartphone or a Tablet PC for example, associated with an adapted user interface allows a flexible and adaptive multi-loudspeaker calibration of the audio rendering system comprising thereof. Such an audio rendering system improves the prior art calibration system by considering the position of the user which holds a mobile device used for the calibration process. In an implementation form, the audio rendering calibration system based on the mobile device comprises a mobile device with at least two microphones, synchronization means between the rendering system and the mobile device, e.g. WiFi, docking station, etc., rendering means for rendering of test or training signals, analysis means for analysis of the loudspeaker rendering system, e.g. position, frequency response, etc, and/or room characteristics, and compensation means for adaptive compensation of the audio rendering based on the analysis step performed by the analysis means.

By applying such audio rendering system where calibration is controlled by an adapted user interface evaluating information delivered by two or more microphones of the user's mobile device, the calibration process is significantly improved and the audio rendering is flexible and dynamic with respect to changing environments as will be presented in the following.

In order to describe the invention in detail, the following terms, abbreviations and notations will be used: audio

rendering: a reproduction technique capable of creating spatial sound fields in an extended area by means of loudspeakers or loudspeaker arrays, sweet

spot: listening position for optimal measurement of the audio signal as it is

actually received by the listener,

OS: operational system, App: application on a mobile device, WiFi Wireless Fidelity according to IEEE 802.1 1 standard.

According to a first aspect, the invention relates to an audio rendering system for audio rendering room acoustics, comprising: a plurality of loudspeakers; a mobile device comprising at least two microphones, the mobile device being located at a room position; and a control device coupled to the plurality of loudspeakers and coupled to the mobile device, wherein the control device is configured to calibrate the audio rendering system based on the room position of the mobile device and on room positions of the

loudspeakers by evaluating information of the at least two microphones of the mobile device. The room position of the mobile device corresponds, for example, to a room position of a user using the mobile device.

The audio rendering system allows a dynamic calibration, in particular a calibration when the user moves or changes his listening position, based on the synchronization between the rendering system and the mobile device, synchronized by WiFi, docking station, etc., for example.

Moreover, the audio rendering system provides a control interface to the user and allows the user to control the calibration of the rendering system. Hence, the user can directly feedback on the performance of the calibration, modify the detected position of the loudspeaker and thus improve the performance of the audio rendering system.

In a first possible implementation form of the audio rendering system according to the first aspect, the control device is configured to start calibrating the audio rendering system by sending a training signal through the plurality of loudspeakers.

By sending a training signal through the loudspeakers, the calibration of the audio rendering is started at a predetermined point in time.

In a second possible implementation form of the audio rendering system according to the first implementation form of the first aspect, the mobile device is configured to record the training signal and to send the recorded training signal and/or information based thereupon to the control device. When the mobile device records the training signal and sends the recorded training signal and/or information based thereupon to the control device, the control device is able to improve its audio rendering by exploiting data from a position inside the room. The room may be a closed room such as a theater, a concert hall or a small office room or it may be an open room such as an arena or a football stadium. When the recorded training signal is sent to the control device, complexity of the mobile device is low as processing is performed in the control device. When information based on the recorded training signal is sent to the control device, data being transmitted can be kept low, as pre-processing is performed in the mobile device and only key performance data is sent to the control device.

In a third possible implementation form of the audio rendering system according to the second implementation form of the first aspect, the information based on the recorded training signal comprises at least one of the following information: information on positions of the plurality of loudspeakers, information on a room characteristic, information on gains in signal paths between the plurality of loudspeakers and the at least two m rophones, information on delays in signal paths between the plurality of loudspeakers and the at least two microphones and information on transfer function in signal paths between the plurality of loudspeakers and the at least two microphones.

The more information the control device receives the better the accuracy of the audio rendering.

In a fourth possible implementation form of the audio rendering system according to the second implementation form or according to the third implementation form of thefirst aspect, the control device is configured to adapt the audio rendering of the audio rendering system based on the recorded training signal and/or information based thereupon received from the mobile device. Audio rendering is not limited to static environments, it performs well in dynamic environments by an adaptive rendering process based on the recorded training signal.

In a fifth possible implementation form of the audio rendering system according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the control device is located in a docking station of the mobile device. The control device does not require a separate unit, it can be integrated in an existing unit such as a docking station. Implementation effort and costs can be kept low when an existing docking station is enhanced by control device functionality.

In a sixth possible implementation form of the audio rendering system according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, each of the at least two microphones is located in the middle of a different edge of the mobile device.

When the microphones are located in the middle of different edges of the mobile device their spatial directivity is improved.

According to a second aspect, the invention relates to a portable electronic device, comprising: at least two microphones; and a processor configured to record a training signal received by the at least two microphones and to transmit the recorded training signal and/or information based thereupon via a transmit interface for calibration of an audio rendering system. The portable electronic device allows a dynamic calibration of an audio rendering system, in particular a calibration when the user moves or changes his listening position, based on the synchronization between the audio rendering system and the portable electronic device. The user is allowed to control the calibration of the audio rendering system.

Hence, the user can directly feedback on the performance of the calibration, modify the detected position of the loudspeaker and thus improve the performance of the audio rendering system.

In a first possible implementation form of the portable electronic device according to the second aspect, the processor comprises an analysis module configured for analyzing the recorded training signal to provide the information based on the recorded training signal.

When the processor comprises an analysis module for analyzing the recorded training signal, analyzed information based on the recorded training signal can be sent to the control device, thereby keeping the load of the interface between portable electronic device and the control device low. Only key performance data found by the analysis module is sent to the control device.

In a second possible implementation form of the portable electronic device according to the second aspect as such or according to the first implementation form of the second aspect, the analysis module is configured to provide as information based on the recorded training signal at least one of the following information: information on a room

characteristic, information on room positions of the loudspeakers, information on gains in signal paths between the loudspeakers and the at least two microphones, information on delays in signal paths between the loudspeakers and the at least two microphones, and information on transfer function in signal paths between the loudspeakers and the at least two microphones.

In a third possible implementation form of the portable electronic device according to the second aspect as such or according to any of the preceding implementation forms of the second aspect, the portable electronic device comprises a synchronization circuit configured to synchronize the recording of the training signal and the transmission of the recorded training signal and/or the information based thereupon with a control device initiating the calibration of the audio rendering system.

Synchronizing the calibration process improves the accuracy of audio rendering.

In a fourth possible implementation form of the portable electronic device according to the second aspect as such or according to any of the preceding implementation forms of the second aspect, the portable electronic device comprises a graphical user interface configured for allowing a user to control the calibration of the audio rendering system by inputting information on a room characteristic used for adapting the audio rendering system.

The graphical user interface enables the direct interaction with the user who can indicate if a loudspeaker which is positioned on the front should be actually positioned on the rear. For instance, if the mobile device is equipped with only two microphones, the analysis system can only discriminate the position of the loudspeaker according to one direction, e.g. left/right or front/back depending on the position of the microphones on the mobile device. The final set of loudspeaker positions and necessary rendering adaptation are then determined according to the recording and additional user information. The user, however, cannot provide the sufficient information on potential delay and equalization between channels. Recording is always necessary to achieve the optimal rendering.

The portable electronic device may comprise an App, i.e., an application tool on a mobile device with a graphic user interface, which can be installed in the mobile OS (operational system) directly. The user can directly get the feedback of the rendering system on the display, e.g. information on loudspeaker position, configuration of the room, etc. and control the adaptation of the rendering system without any difficulties.

In a fifth possible implementation form of the portable electronic device according to the second aspect as such or according to any of the preceding implementation forms of the second aspect, the portable electronic device further comprises earphones, wherein the processor is configured to record the training signal received by microphones integrated in the earphones for binaurally capturing the training signal at an ear canal of a user using the portable electronic device or to record the training signal by a combination of the at least two microphones and the microphones integrated in the earphones.

Thus, audio rendering can directly exploit information of the sweet spot. By a combined recording the audio rendering is improved and adapted to the listener's position. According to a third aspect, the invention relates to a method for calibrating an audio rendering system for audio rendering room acoustics, the method comprising: recording a training signal by at least two microphones of a mobile device being located in a room, the training signal being transmitted through a plurality of loudspeakers located in the room; transmitting the recorded training signal and/or information based thereupon to a control device configured for calibrating the audio rendering system.

This direct interaction with the user allows to always providing the rendering sweet spot to the listeners. It improves the multichannel audio rendering at the listening position for applications like Home Cinema, Home Theater, sound bar, docking station etc. based on an easy to use calibration tool based on mobile device as analysis/control tool. In a first possible implementation form of the method according to the third aspect, the method further comprises: initiating the calibrating by the mobile device by transmitting an initiation signal to the control device.

By sending an initiation signal to the control device, the calibration of the audio rendering is acknowledged by the mobile device and thus started at a predetermined point in time.

The methods described herein may be implemented as software in a Digital Signal Processor (DSP), in a micro-controller or in any other side-processor or as hardware circuit within an application specific integrated circuit (ASIC).

The invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the invention will be described with respect to the following figures, in which:

Fig. 1 shows a schematic diagram of a basic audio rendering system according to an implementation form; Fig. 2 shows a schematic diagram of an audio rendering system with the user being outside the system according to an implementation form;

Fig. 3 shows a schematic diagram of an audio rendering system with all loudspeakers being positioned in front of the user according to an implementation form;

Fig. 4 shows a schematic diagram of an audio rendering system with calibration based on a docking station according to an implementation form;

Fig. 5 shows a schematic diagram of a microphone arrangement on a Tablet PC according to an implementation form; Fig. 6 shows a schematic diagram of an audio rendering system with calibration based on a docking station integrating a control device according to an implementation form; Fig. 7 shows a schematic diagram of an audio rendering system with calibration based on microphones installed in headphones of a listener according to an implementation form;

Fig. 8 shows a schematic diagram of a method for calibrating an audio rendering system according to an implementation form;

Fig. 9 shows a schematic diagram of a 5.1 multichannel loudspeaker system according to the recommendation ITU- BS 775-1 ;

Fig. 10 shows a schematic diagram of a non-standardized 5.1 multichannel loudspeaker system; and

Fig. 1 1 shows a schematic diagram of a microphone configuration of a conventional mobile phone. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

There are two microphone configurations in current mobile phones. The first one corresponds to the configuration depicted in Fig. 1 1 but the second microphone 1 107 depicted in Fig. 1 1 is missing. It has only one single microphone 1 1 13 which is used for communication and any other mono sound pickup. This first configuration is based on omnidirectional microphone and cannot provide any stereo image.

The other configuration is illustrated in Fig. 1 1 and uses two omnidirectional microphones, the main microphone 1 1 13 and the auxiliary microphone 1 107. The main microphone 1 1 13 is used for the sound pick up, i.e. for communication application as well as simple audio/video recording. The auxiliary microphone 1 107 is used for noise cancellation and gain control. An omnidirectional microphone needs only one hole in the terminal as opposed to directional microphones. Indeed, the omnidirectional microphone offers a uniform directivity pattern in all the direction, equivalent to a sphere, and only one hole is then required for the microphone housing 1 1 15. The size of the hole and the actual microphone housing 1 1 15 will affect the directivity of the complete system, but a single hole is sufficient for perfect sound pickup. Two omnidirectional microphones mounted with a spacing of several centimeters can also be used in order to obtain a stereo recording. Fig. 1 shows a schematic diagram of a basic audio rendering system 100 according to an implementation form.

A user or listener 109 sitting on a sofa holds a mobile device 105, e.g. a Smartphone or a tablet PC including at least two microphones 107. The mobile device 105 is connected to a control device 103, e.g. a set top box or an amplifier through a wireless or a wire line connection. The control device 103 is performing the rendering adaptation, i.e., application of gains, delays, filters, etc. The audio rendering system 100 comprises the following elements:

a plurality of loudspeakers 101 , e.g. a loudspeaker array or a loudspeaker system; a mobile device 105, e.g. a Smartphone or a tablet PC with multiple microphones

107, i.e., at least two omnidirectional or directional microphones;

open or standardized synchronization means, e.g. via WiFi, docking station, etc. between the audio rendering control device 103 and the mobile device 105;

analysis device of the audio rendering system and/or room characteristics; and control device 103 for the adaptive compensation of the audio rendering based on an analysis step of the analysis device.

In an implementation form, the analysis and control devices are implemented in separated devices. In an alternative implementation form, the analysis and control devices are implemented in the same device. The adaptation of the multi-loudspeaker audio rendering can be directly calculated in the analysis device if the test signal is known a priori by this device.

In an implementation form, for calibrating the audio rendering system 100, the user 109 of the mobile device 105 performs the following steps which interact with the control device 103:

starting the calibration procedure, e.g., with a mobile device application using a graphical user interface; mobile device 105 sends indication to control device 103 of starting the procedure through the connection means, e.g. via WiFi, WLAN or docking station;

control device 103 starts the rendering of training signal through the loudspeaker system, i.e. through the multi-loudspeaker 101 shown in Fig. 1 ;

mobile device 105 records the training signal with multiple microphones 107; mobile device 105 analyzes the position of loudspeakers 101 and/or room characteristics;

a set of parameters, e.g. delay, gains, filters, etc. are extracted by the mobile device 105 to build a map of the loudspeaker system and to send these parameters to the control device 103. In an implementation form, at least positions of the loudspeakers 101 are transmitted by applying a specific protocol to exchange this information. In an alternative implementation form, the gains and delays are also transmitted. In an alternative implementation form, the mobile device 105 sends the recorded signals to the control device 103 and the analysis is done in the control device 103; and

control device 103 adapts the audio rendering based on the loudspeaker positions and/or room characteristic analysis.

In an implementation form, the mobile device 105 performs the computation of adaptation parameters such as delay, gains, filters, equalizer, etc. and sends these parameters to the control device 103. In an alternative implementation form, only the positions of the loudspeakers 101 are transmitted to the control device 103, the computation of the adaptation parameters are then performed in the rendering system, i.e., in the control device 103 in order to select the most appropriate processing, e.g., post processing of the audio channel signal, or adaptation in the coded domain.

Fig. 2 shows a schematic diagram of an audio rendering system 200 with the user 209 being outside the system 200 according to an implementation form.

A user or listener 209 sitting on a sofa outside the audio system holds a mobile device 205, e.g. a Smartphone or a tablet PC including at least two microphones 207. The mobile device 205 is connected to a control device 203, e.g. a set top box or an amplifier through a wireless or a wire line connection. The control device 203 is performing the rendering adaptation, i.e., application of gains, delays, filters, etc. The audio rendering system 200 comprises the following elements: a plurality of loudspeakers 201 , a mobile device 205 with at least two omnidirectional or directional microphones, a synchronization means between the control device 203 and the mobile device 205, an analysis device of the audio rendering system and/or room characteristics and a control device 103 for the adaptive compensation of the audio rendering based on the analysis of the analysis device.

The calibration is performed analogously to the procedure described with respect to Fig. 1 . The audio rendering system 200 is able to calibrate the system if the user 209 is not located at the sweet spot of the audio rendering system even if the user 209 is sitting outside the audio system.

Fig. 3 shows a schematic diagram of an audio rendering system 300 with all loudspeakers being positioned in front of the user according to an implementation form.

A user or listener 309 sitting on a sofa behind a loudspeaker array 301 arranged in a line in front of the user 309. The user 309 holds a mobile device 305, e.g. a Smartphone or a tablet PC including at least two microphones 307. The mobile device 305 is connected to a control device 303, e.g. a set top box or an amplifier through a wireless or a wire line connection. The control device 303 is performing the rendering adaptation, i.e., application of gains, delays, filters, etc. The audio rendering system 300 comprises the following elements: a plurality of loudspeakers 301 arranged in line in front of the user 309, a mobile device 305 with at least two omnidirectional or directional microphones 307, synchronization means between the control device 303 and the mobile device 305, analysis device of the audio rendering system and/or room characteristics and a control device 303 for the adaptive compensation of the audio rendering based on the analysis of the analysis device.

The calibration is performed analogously to the procedure described with respect to Fig. 1 . The audio rendering system 300 is able to calibrate the system even if the

loudspeakers 301 are arranged in front of the user 309 and if there are no surround loudspeakers available in the audio system.

Fig. 4 shows a schematic diagram of an audio rendering system 400 with calibration based on a docking station 401 according to an implementation form. A user or listener 409 is sitting on a sofa behind a docking station 401 comprising at least two loudspeakers. The user 409 holds a mobile device 405, e.g. a Smartphone or a tablet PC including at least two microphones 407. The mobile device 405 is connected to a control device 403, e.g. a set top box or an amplifier through a wireless or a wire line connection. The control device 403 is performing the rendering adaptation, i.e., application of gains, delays, filters, etc. The audio rendering system 400 comprises the following elements: loudspeakers integrated in a docking station 401 arranged in front of the user 409, a mobile device 405 with at least two omnidirectional or directional microphones 407, synchronization means between the control device 403 and the mobile device 405, analysis device of the audio rendering system and/or room characteristics and a control device 403 for the adaptive compensation of the audio rendering based on the analysis of the analysis device. Docking station 401 and control device 403 are separate units.

The calibration is performed analogously to the procedure described with respect to Fig. 1 . The audio rendering system 400 is able to calibrate the system even if there are only two loudspeakers integrated in the docking station 401 arranged in front of the user 409 and if there are no other front loudspeakers or surround loudspeakers available in the audio system. Fig. 5 shows a schematic diagram of a microphone arrangement on a Tablet PC 500 according to an implementation form.

The Tablet PC 500 comprises a number of four microphones 507 arranged in the middle of each edge of the tablet in order to better discriminate or distinguish the directions of the sounds. The tablet PC 500 corresponds to the mobile device described above with respect to Figures 1 to 4. The table PC 500 is adapted to perform the calibration analogously to the procedure described with respect to Fig. 1.

Fig. 6 shows a schematic diagram of an audio rendering system 600 with calibration based on a docking station integrating a control device according to an implementation form.

A user or listener 609 sitting on a sofa holds a mobile device 605, e.g. a Smartphone or a tablet PC including at least two microphones 607. The mobile device 605 is connected to a control device 603, e.g. a set top box or an amplifier through a wireless or a wire line connection. The control device 603 is performing the rendering adaptation, i.e., application of gains, delays, filters, etc. The audio rendering system 600 comprises the following elements:

mobile device 605, e.g. a Smartphone or a tablet PC with multiple microphones 607, i.e., at least two omnidirectional or directional microphones;

docking station 601 with the possibility to connect to the mobile device 605, e.g., by a dock connector;

analysis device of the audio rendering system and/or room characteristics; and control device integrated in the docking station 601 for the adaptive compensation of the audio rendering based on an analysis step of the analysis device.

In an implementation form, for calibrating the audio rendering system 600, the user 609 of the mobile device 605 performs the following steps which interact with the control device in the docking station 601 :

Connecting the mobile device 605 on the docking station 601 , e.g., by the dock connector;

starting the calibration procedure, e.g., with a mobile device application using a graphical user interface;

mobile device 605 sends indication to the docking station 601 of starting the calibration procedure;

docking station 601 starts the rendering of training signal through the loudspeaker system included in the docking station 601 ;

mobile device 605 records the training signal using the multiple microphones 607; mobile device 605 analyzes the position of loudspeaker in the docking station 601 and/or room characteristics;

user 609 puts the mobile device 605 on the docking station 601 and the mobile device 605 provides the loudspeaker positions and/or room characteristics to the docking station 605 which adapts the rendering based on the loudspeaker positions and/or room characteristics analysis.

In an alternative implementation form, for calibrating the audio rendering system 600, the user 609 of the mobile device 605 performs the following steps which interact with the control device in the docking station 601 :

Connecting the mobile device 605 on the docking station 601 , e.g., by the dock connector; starting the calibration procedure, e.g., with a mobile device application using a graphical user interface;

user 609 puts the mobile device 605 on the docking station 601 and the mobile device 605 transmits the recorded signal to the docking station 601 and the analysis is done directly in the docking station 601 prior to the adaptation of the rendering based on the loudspeaker positions and/or room characteristics analysis of the control device in the docking station 601 .

starting the calibration procedure by a timer integrated to the application to indicate how long the docking station must wait before starting to play the training sound;

mobile device 605 sends timing information to the docking station 601 to inform docking station 601 of starting the calibration procedure;

user 609 puts the mobile device 605 on the docking station 601 and the mobile device 605 provides the loudspeaker positions and/or room characteristics to the docking station 605 which adapts the rendering based on the loudspeaker positions and/or room characteristics analysis. In an alternative implementation form, for calibrating the audio rendering system 600, the user 609 of the mobile device 605 performs the following steps which interact with the control device in the docking station 601 :

user 609 puts the mobile device 605 on the docking station 601 and the mobile device 605 transmits the recorded signal to the docking station 601 and the analysis is done directly in the docking station 601 prior to the adaptation of the rendering based on the loudspeaker positions and/or room characteristics analysis of the control device in the docking station 601.

Fig. 7 shows a schematic diagram of an audio rendering system 700 with calibration based on microphones installed in headphones of a listener according to an

implementation form. A user or listener 709 is sitting on a sofa and holds a mobile device 705, e.g. a

Smartphone or a tablet PC including at least two microphones 707. The user 709 carries earphones with stereo microphones 713. The mobile device 705 is connected to a control device 703, e.g. a set top box or an amplifier through a wireless or a wire line connection. The control device 703 is performing the rendering adaptation, i.e., application of gains, delays, filters, etc. The audio rendering system 700 comprises the following elements: front loudspeakers 701 and surround loudspeakers 71 1 , a mobile device 705 with at least two omnidirectional or directional microphones 707, synchronization means between the control device 703 and the mobile device 705, analysis device of the audio rendering system and/or room characteristics and a control device 703 for the adaptive

compensation of the audio rendering based on the analysis of the analysis device. The calibration is performed analogously to the procedure described with respect to Fig. 1 . The audio rendering system 700, however, is based on the use of stereo microphones 713 installed on the earphones or headphones and which are connected to the mobile device 705.

Compared to the previous implementation forms described with respect to Figures 1 to 6, this alternative scenario is based on binaural recording made through earphones or headphones with microphones 713 mounted on each side. Microphones 713 are directly integrated in the earphones/headphones capturing the audio signal directly at the ear canal. The user 709 connects the earphones/headphones to the mobile device 705 and the sound recording is done by this binaural microphone 713.

This implementation form is advantageously based on recording which is directly representative of human perception of the multi-loudspeaker rendering system. The rendering adaptation is directly based on the recording at the user's 709 ears which ensure that the adaptation, if done properly, will perfectly reconstruct the optimal multichannel signal at the ears of the listener 709.

In a further alternative implementation form, the analysis device combines the recording by the microphones 713 integrated to the earphones with the recording by the

microphones 707 of the mobile device 705. This combined recording provides a larger area of adaptation and limits the over tuning of the calibration algorithm to the user ears position. Fig. 8 shows a schematic diagram of a method 800 for calibrating an audio rendering system according to an implementation form.

The method 800 comprises recording 801 a training signal by at least two microphones of a mobile device being located in a room, the training signal being transmitted through a plurality of loudspeakers located in the room.

The method 800 comprises transmitting 803 the recorded training signal and/or information based thereupon to a control device configured for calibrating the audio rendering system.

In an implementation form, the method 800 comprises initiating the calibrating by the mobile device by transmitting an initiation signal to the control device. From the foregoing, it will be apparent to those skilled in the art that a variety of methods, systems, computer programs on recording media, and the like, are provided. The present disclosure also supports a computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the performing and computing steps described herein.

The present disclosure also supports a system configured to execute the performing and computing steps described herein.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present inventions has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the spirit and scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the inventions may be practiced otherwise than as specifically described herein.

Claims

CLAIMS:

1 . Audio rendering system (100) for audio rendering room acoustics, comprising: a plurality of loudspeakers (101 ); a mobile device (105) comprising at least two microphones (107), the mobile device (105) being located at a room position ; and a control device (103) coupled to the plurality of loudspeakers (101 ) and coupled to the mobile device (105), wherein the control device (103) is configured to calibrate the audio rendering system (100) based on the room position of the mobile device (105) and based on room positions of the loudspeakers (101 ) by evaluating information of the at least two microphones (107) of the mobile device (105).

2. The audio rendering system (100) of claim 1 , wherein the control device (103) is configured to start calibrating the audio rendering system (100) by sending a training signal through the plurality of loudspeakers (101 ).

3. The audio rendering system (100) of claim 2, wherein the mobile device (105) is configured to record the training signal and to send the recorded training signal and/or information based thereupon to the control device (103).

4. The audio rendering system (100) of claim 3, wherein the information based on the recorded training signal comprises at least one of the following information: information on positions of the plurality of loudspeakers (101 ), information on a room characteristic, information on gains in signal paths between the plurality of loudspeakers (101 ) and the at least two microphones (107), information on delays in signal paths between the plurality of loudspeakers (101 ) and the at least two microphones (107), and information on transfer function in signal paths between the plurality of

loudspeakers (101 ) and the at least two microphones (107).

5. The audio rendering system (100) of claim 3 or claim 4, wherein the control device (103) is configured to adapt the audio rendering of the audio rendering system (100) based on the recorded training signal and/or information based thereupon received from the mobile device (105).

6. The audio rendering system (600) of one of the preceding claims, wherein the control device (103) is located in a docking station (601 ) of the mobile device (605).

7. The audio rendering system (100) of one of the preceding claims, wherein each of the at least two microphones (107) is located in the middle of a different edge of the mobile device (105).

8. A portable electronic device (500), comprising: at least two microphones (507); and a processor configured to record a training signal received by the at least two microphones (507) and to transmit the recorded training signal and/or information based thereupon via a transmit interface for calibration of an audio rendering system.

9. The portable electronic device (500) of claim 8, wherein the processor comprises an analysis module configured for analyzing the recorded training signal to provide the information based on the recorded training signal.

10. The portable electronic device (500) of claim 8 or claim 9, wherein the analysis module is configured to provide as information based on the recorded training signal at least one of the following information: information on a room characteristic, information on room positions of the loudspeakers, information on gains in signal paths between the loudspeakers and the at least two microphones (507), information on delays in signal paths between the loudspeakers and the at least two microphones (507), and information on transfer function in signal paths between the loudspeakers and the at least two microphones (507).

1 1. The portable electronic device (500) of one of claims 8 to 10, comprising a synchronization circuit configured to synchronize the recording of the training signal and the transmission of the recorded training signal and/or the information based thereupon with a control device initiating the calibration of the audio rendering system.

12. The portable electronic device (500) of one of claims 8 to 1 1 , comprising a graphical user interface configured for allowing a user to control the calibration of the audio rendering system by inputting information on a room characteristic used for adapting the audio rendering system.

13. The portable electronic device (500) of one of claims 8 to 12, further comprising earphones, wherein the processor is configured to record the training signal received by microphones (713) integrated in the earphones for binaurally capturing the training signal at an ear canal of a user using the portable electronic device (500) or to record the training signal by a combination of the at least two microphones (507) and the microphones (713) integrated in the earphones.

14. Method (800) for calibrating an audio rendering system for audio rendering room acoustics, the method comprising: recording (801 ) a training signal by at least two microphones of a mobile device being located in a room, the training signal being transmitted through a plurality of loudspeakers located in the room; transmitting (803) the recorded training signal and/or information based thereupon to a control device configured for calibrating the audio rendering system.

15. The method (800) of claim 14, further comprising: initiating the calibrating by the mobile device by transmitting an initiation signal to the control device.