FR3123002A1 - WHISTLE DETECTION - Google Patents

Abstract

The system (102) for detecting an acoustic signal, such as a whistle, from a referee or judge (106) of a sports match, comprises: - first and second microphones (112, 113) designed to respectively provide first and second signals (S1, S2); and - an analysis device (204) adapted to analyze the first and second signals (S1, S2) to detect the acoustic signal, with the aim of stopping or restarting a timer (120). Figure for abstract: Fig. 1

Description

WHISTLE DETECTION

Technical field of the invention

The present invention relates to a system for detecting an acoustic signal, such as a whistle, from a referee or a judge of a sports match, an installation for controlling the playing time of a sports match comprising such a detection system, a method for detecting a corresponding acoustic signal and a computer program for implementing the method.

Technology background

The international application published under the number WO 2012/01275 A1 describes a system for detecting a whistle from a referee at a sporting match, comprising a microphone designed to supply a signal and an analysis device designed to analyze the signal to detect the whistle.

More precisely, in this publication, the analysis consists in comparing a signal envelope with a predefined envelope.

In a system of the type described in this publication, distant whistles, for example coming from the public at the sporting event, or equivalent noises such as the squealing of shoes can lead to non-detections or even untimely detections. .

It may thus be desirable to provide a system for detecting a whistle from a referee of a sporting match which makes it possible to improve the reliability of the detection of whistles from the referee or the judge of the match. athletic.

• des premier et deuxième microphones conçus pour respectivement fournir des premier et deuxième signaux ; et
• un dispositif d’analyse conçu pour analyser les premier et deuxième signaux pour détecter le signal acoustique, dans le but d’arrêter ou de relancer un chronomètre.

There is therefore proposed a system for detecting an acoustic signal, such as a whistle, from a referee or judge of a sporting match, characterized in that it comprises:

• first and second microphones configured to respectively provide first and second signals; and
• an analysis device adapted to analyze the first and second signals to detect the acoustic signal, in order to stop or restart a timer.

Thus, thanks to the use of two microphones, it is possible to improve the reliability of the detection of whistles, in particular vis-à-vis distant sound sources (public) or very close (squealing of shoes, horn ).

Within the meaning of the present invention, a microphone can be any acoustic-electric transducer.

Optionally, the analysis device comprises an amplitude determination module designed to determine an amplitude of the first signal.

Also optionally, the analysis device comprises an analysis module designed to compare this amplitude with a predefined threshold.

Also optionally, the amplitude determination module is further designed to determine an amplitude of the other of the first and second signals, and the analysis device comprises at least one analysis module designed to compare the amplitudes of the first and second signals.

Also optionally, the analysis device comprises at least one module for frequency analysis of the second signal supplied by the second microphone.

Also optionally, the system further comprises a device for transmitting, in the event of detection of the whistle, a whistle detection message.

Also optionally, the first and second microphones are designed to be placed at least 20 cm, preferably 40 cm, from each other.

Also optionally, the first microphone is attached to a referee's whistle so as to remain less than 5 cm from the whistle.

Also optionally, the system further comprises a strap to which the first microphone and the whistle are attached .

Also optionally, the system further comprises a system for attaching to the referee, for example on the referee's belt, and the second microphone is attached to this attachment system.

• un système de détection d’un coup de sifflet selon l’invention ; et
• le chronomètre de temps de jeu conçu pour recevoir le message de détection, par exemple via un récepteur, et s’arrêter ou bien se relancer en réponse au message de détection.

There is also proposed an installation for controlling the playing time of a sports meeting, comprising:

• a whistle detection system according to the invention; and
• the game time clock designed to receive the detection message, for example via a receiver, and to stop or start again in response to the detection message.

There is also proposed a method for detecting an acoustic signal, such as a whistle, from a referee or a judge of a sporting match, comprising the analysis of first and second signals respectively provided by first and second microphones, to detect the whistle, for the purpose of stopping or restarting a game time clock.

Optionally, the method comprises, prior to the analysis of the first and second signals, the installation of the first and second microphones on the referee so that the first microphone is less than 5 cm from the whistle when the whistle is used, preferably between 2 and 3 cm, and so that the second microphone is at least 20 cm, preferably 40 cm, further from the whistle than the first microphone when the whistle is used.

There is also proposed a computer program downloadable from a communication network and/or recorded on a computer-readable medium, characterized in that it comprises instructions for the execution of the steps of a method according to the invention, when said program is run on a computer.

Brief description of figures

The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the appended drawings in which:

the is a schematic view of an installation for controlling the playing time of a sports match, comprising a system for detecting a whistle according to the invention,

the is a functional view of the detection system of the ,

the is a functional view of an analysis unit of the detection system of the , and

the is a block diagram of a whistle detection method according to the invention.

Detailed description of the invention

With reference to the , an example of an installation 100 for controlling the playing time of a sporting event, such as a basketball match, in which the invention is implemented, will now be described.

The installation 100 firstly comprises a detection system 102 designed to detect a whistle of the sporting event. More specifically, in the example described, the acoustic signal is a whistle emitted by a whistle 104 of a referee or a judge 106 of the sporting event, signaling for example a stoppage or a resumption of playing time The detection system 102 is further designed to transmit, preferably wirelessly, a detection message resulting from the detection of the whistle. The whistle 104 is for example attached to a strap 108 which can be passed around the neck of the referee 106.

The detection system 102 comprises, in the example described, a main box 110 and first and second microphones 112, 113. The first microphone 112 is, in the example described, external to the main box 110 and for example connected to this last via a wired connection 114. Alternatively, a wireless connection could be used between the first microphone 112 and the main box 110. The second microphone 113 is located, in the example described, in the main box 110. Alternatively, it could be located outside the main housing 110, for example attached to the latter.

The detection system 102 is preferably portable in order to be worn by the referee 106. Thus, the microphone 112 is for example attached to the strap 108 or directly to the whistle 104, while the main box 110 comprises a system of attaches (not shown) to the body of the referee 106, that is to say on any part of the body of the referee except the head and the neck of the referee 106. The attachment system can be attach directly to the body of the referee or else indirectly, on clothing of the referee 106, for example to the belt of the referee 106. The fastening system comprises for example a clip for fastening to the belt. Thus, at least when the whistle 104 is used, the first microphone 112 is located close to the whistle 104, for example less than 5 cm, preferably between 2 and 3 cm, while the second microphone 113 is located at least 20 cm, preferably at least 40 cm, further from the whistle 104 than the first microphone 112.

Thus, subsequently, the first microphone 112 will be called “near microphone” and the second microphone 113 will be called “far microphone”.

The installation 100 further comprises a receiver 118 and a stopwatch 120, for example game time, connected to each other, for example by a wired connection 122. The receiver 118 is designed to receive the detection message and transmit it to the stopwatch 120. The latter is in particular designed, in response to the reception of the detection message, to stop or to start again.

With reference to the , the detection system 102 will now be described in more detail.

The microphones 112, 113 are designed to provide respectively first and second signals S1, S2, for example analog or digital, representative of respective measurements of the sound environment.

The detection system 102 further comprises a device 204 for analyzing the signals S1, S2 to detect a whistle in the sound environment.

In the example described, the analysis device 204 includes band-pass filters 205, 206 to respectively filter the signals S1, S2. Preferably, these band-pass filters 205, 206 have a bandwidth of between 3 kHz and 5 kHz. For example, the bandwidth ranges from 3.25 kHz to 4.75 kHz.

The analysis device 204 further comprises, when the signals S1, S2 are analog, analog-digital converters 208, 210 to convert the filtered signals into digital signals S'1, S'2. Alternatively, the filtering could be performed after the analog-to-digital conversion.

The analysis device 204 further comprises a unit 212 for analyzing the digital signals S'1, S'2 designed to detect the whistle from the analysis of the digital signals S'1, S'2 and, in this case, provide a detection message.

In the example described, the analysis unit 212 comprises a computer, that is to say a computer system comprising a data processing unit 212A (such as a microprocessor) and a main memory 212B (such as a RAM memory, standing for “Random Access Memory”) accessible by the processing unit 212A. The computer system further comprises, for example, a network interface (not shown) and/or a computer-readable medium (not shown), such as for example a local medium (such as a local hard disk or else a FLASH memory) or else a remote medium (such as a remote hard disk accessible via the network interface through a communication network (not shown) or even a removable medium (such as a USB key, English " Universal Serial Bus") readable by means of a reader (not shown) suitable for the computer system (such as a USB port). A computer program (212C) containing instructions for the processing unit 212A is recorded on the medium and/or downloadable via the network interface.This computer program 212C is for example intended to be loaded into the main memory 212B, so that the processing unit executes its instructions. computer (212C), instructions will be described below as organized into software modules. However, this presentation does not prejudge the form of the computer program 212C, which may be arbitrary. In addition, the term “computer” is to be taken in the broad sense and covers both, for example, a microcontroller and a smart phone (from the English “smartphone”).

Alternatively, all or part of the modules could be implemented in the form of hardware modules, that is to say in the form of an electronic circuit, for example micro-wired, not involving a computer program.

The detection system 102 further comprises a wireless transmission device 214, for example placed in the box 110, designed to transmit the detection message D to the receiver 118.

With reference to the , the modules of the analysis unit 212 will now be described in more detail.

The analysis unit 212 firstly comprises an acquisition module 302 designed to acquire a predefined number of consecutive samples simultaneously for the digital signal S'1 and the digital signal S'2, i.e. say over the same time interval for the two digital signals S'1, S'2. These samples form a frame T1 for the digital signal S'1 and a frame T2 for the digital signal S'2. Preferably, each frame T1, T2 comprises at least 100 samples, for example 512 consecutive samples.

The analysis unit 212 can be designed to carry out an amplitude analysis of at least one of the digital signals S'1, S'2.

Thus, the analysis unit 212 further includes an amplitude determination module 304 designed to respectively determine amplitudes A1, A2 of frames T1, T2. For example, each amplitude A1, A2 is equal to the effective value (from the English "Root Mean Square", or RMS) of the samples of the respective frame T1, T2.

The analysis unit 212 further comprises, in the example described, three amplitude analysis modules 306, 308, 310.

The first amplitude analysis module 306 is designed to compare the amplitude A1 coming from the close microphone 112 with a first predefined threshold V1, and to provide a first amplitude analysis result RA1, positive when the amplitude A1 is greater than threshold V1 and negative otherwise. A positive result indicates the presence of a noise loud enough to be a whistle. This analysis thus makes it possible to avoid untimely detections which could, for example, come from the breath of the referee when he is running.

The threshold V1 is for example set according to the type of close microphone 112 used, the minimum sound level of the type of whistle 104 likely to be used and the distance between the close microphone 112 and the whistle 104 when using the detection system 102. For example, the close microphone 112 is attached to the strap 108 at a distance of between 2 and 3 cm from the whistle 104, which is taken into account to set the threshold V1.

The second amplitude analysis module 308 is designed to compare the amplitudes A1, A2 with each other, and to provide a second amplitude analysis result RA2, positive when the amplitude A1 coming from the microphone near 112 is greater than the amplitude A2 from the far microphone 113 and negative otherwise.

The third amplitude analysis module 310 is designed to determine an absolute difference D between the amplitudes A1, A2, for example given by D = |A1 - A2|, where |…| is the absolute value function. The third amplitude analysis module 310 is also designed to compare this absolute difference D with a second predefined threshold V2, and to provide a third amplitude analysis result R3, positive when the absolute difference D is greater than the threshold V2 and negative otherwise.

The modules 308, 310 could be grouped together in a single module designed to determine a relative difference D' between the amplitudes A1, A2 (for example given by D'=A1-A2) and to compare this relative difference D' with the threshold V2 .

These comparisons between the two amplitudes A1, A2 make it possible to determine more precisely whether the perceived sound is ambient, whether it comes from a source which encompasses the two microphones 112, 113, such as a vuvuzela or the horn of a spectator. Indeed, during a whistle from the referee 106, the amplitude A1 of the signal S1 supplied by the close microphone 112 is greater than that of the signal S2 supplied by the distant microphone 113. If the difference is less than this value V2, it is considered that the sound cannot come from the whistle 104, but rather from a distant source. If the A2 amplitude is greater than the A1 amplitude, the sound source must be coming from the ground and is probably a shoe squeal.

It will be appreciated that the comparison of the amplitudes A1, A2 is a simple solution for detecting whether the source of the sound is compatible or not with a referee's whistle 106 and does not require, in particular, complex calculations of difference in propagation time to try to locate the position of the sound source, in order to determine if this position is compatible with the position of the whistle 104 when it is used.

The threshold V2 is for example fixed according to the respective locations of the two microphones 112, 113 provided on the referee (strap-belt in the example described).

The analysis unit 212 can be designed to perform, in addition to an amplitude analysis or instead, a frequency analysis on at least one of the frames T1, T2. Preferably, the latter is carried out only from the T2 frame coming from the distant microphone 113, because the analog signal S1 supplied by the close microphone 112 is likely to be saturated, which would risk distorting the frequency analysis. by introducing parasitic frequency peaks which do not really exist.

Thus, in the example described, the analysis unit 212 further comprises a frequency conversion module 312 designed to convert the frame T2 coming from the remote microphone 113 in a frequency domain in order to obtain a frequency spectrum F2. The frequency spectrum F2 is for example obtained by Fourier transform of the frame T2, for example a fast Fourier transform (from the English “Fast Fourier Transform”, or FFT).

The analysis unit 212 further comprises, still in the example described, a peak search module 314, designed to search for frequency peaks P2 in the frequency spectrum F2. Each peak found is for example defined by an amplitude and a frequency at which it is found. Peaks outside the passband of bandpass filter 206 may also be found.

The analysis unit 212 further comprises, in the example described, three frequency analysis modules 316, 318, 320.

The first frequency analysis module 316 is designed to determine the highest amplitude among the amplitudes of the peaks present in a predefined frequency interval, preferably equal to the passband of the bandpass filter 206. The first frequency analysis module frequency analysis 316 is also designed to compare this highest amplitude with a third predefined threshold V3, and to provide a first frequency analysis result RF1, positive if the threshold V3 is exceeded and negative otherwise. Thus, the frequency analysis result RF1 is positive even if there are other peaks detected outside the frequency range of the whistle 104, which generally extends from 2800Hz to 4500Hz, presenting similar amplitudes. This makes it possible to detect a very powerful peak, drowned in very high ambient noise. It is thus considered that this very powerful peak corresponds to the fact that the referee 106 blows hard into the whistle 104 to drown out the ambient noise.

The second frequency analysis module 318 is designed to compare the amplitude of each peak found in a predefined frequency interval, preferably equal to the bandwidth of the bandpass filter 206, with a fourth predefined threshold V4, and to provide a second frequency analysis result RF2, positive if the amplitude of each peak found is greater than threshold V4 and negative otherwise. Preferably, the threshold V4 is at least twice lower than the threshold V3, or, in other words, the threshold V3 is at least twice higher than the threshold V4. This detection corresponds to a normal situation. Indeed, the frequency interval (in particular the bandwidth) is chosen to be included in the frequency bands of the whistles usually used.

The third frequency analysis module 320 is designed to search, in a predefined frequency interval, equal for example to the bandwidth, among the peaks P2 found, two peaks of the same frequency (or of close frequency, for example close to 20 % near) respectively of the current frame T2 and the previously acquired frame T2 whose sum of the amplitudes is greater than a fifth predefined threshold V5. The third frequency analysis module 320 is further designed to determine if noise is present in the current T2 frame, as well as in the previously acquired T2 frame. The third frequency analysis module 320 is also designed, optionally, to determine whether peaks (for example of amplitude greater than a certain threshold) are present outside the passband. The third frequency analysis module 320 is then designed to provide a third frequency analysis result RF3, positive (i) if there are two consecutive peaks whose sum of amplitudes is greater than the threshold V5, (ii) if no noise is detected in the current T2 frame and in the previous one and, if applicable, (iii) if there are no peaks outside the passband, and negative otherwise. This analysis has the function of detecting a weak whistle in a calm atmosphere.

The analysis unit further comprises a synthesis module 322 designed to detect or not the whistle as a function of at least part of the analysis results RA1, RA2, RA3, RF1, RF2 and RF3.

More specifically, in the example described, the synthesis module 322 is designed to provide an overall frequency analysis result RF from the frequency analysis results RF1, RF2 and RF3, positive when at least of the latter is positive and negative otherwise (block “≥1” on the ).

The synthesis module 322 is further designed to detect a whistle when all the RA1, RA2, RA3 amplitude analysis and RF frequency analysis results are positive, and not to detect a whistle in the contrary case (“&” block on the ). In this case, the synthesis module 322 does not need all the results RA1, RA2, RA3 and RF to conclude that there is no whistle, it only needs a single negative result.

To save calculations and therefore energy - an important issue for portability - the analysis unit 212 is preferably designed to first activate successively the amplitude analysis modules 306, 308, 310 to obtain the results RA1, RA2, RA3, before activating the modules 312 to 320 relating to the frequency analysis if all the results RA1, RA2, RA3 are positive. Thus, as soon as a negative result is obtained, it is not necessary to activate the other modules and in particular those of frequency conversion 312 and search for peaks 314 which may involve significant calculations.

With reference to the , an example of a method 400 for detecting a whistle will now be described.

During a step 402, the detection device 102 is installed on the referee. In particular, the first microphone 112 is installed on the referee 106, for example as previously described, so that the first microphone 112 is within 5 cm of the whistle 104 when the whistle is used, preferably between 2 and 3 cm, and so that the second microphone 113 is at least 20 cm, preferably 40 cm, further from the whistle 104 than the first microphone 112 when the whistle 104 is used.

During a step 404, the microphones 112, 113 supply their respective signals S1, S2.

During a step 406, the analog signals S1, S2 are filtered and digitized to provide the digital signals S'1, S'2.

During a step 408, the acquisition module 302 provides the two current frames T1, T2.

During a step 410, the amplitude determination module 304 supplies the amplitudes A1, A2 of the frames T1, T2.

During a step 412, the first amplitude analysis module 306 compares the amplitude A1 coming from the close microphone 112 with the threshold V1. If the amplitude A1 is not greater than the threshold V1, the result RA1 is negative and the synthesis module 322 detects an absence of whistle. Method 400 then returns to step 404. Otherwise, method 400 continues.

During a step 414, the second amplitude analysis module 308 compares the amplitudes A1, A2 with each other. If the amplitude A1 (close microphone 112) is not greater than the amplitude A2 (far microphone 113), the result RA2 is negative and the synthesis module 322 detects an absence of whistle. Method 400 then returns to step 404. Otherwise, method 400 continues.

During a step 416, the third amplitude analysis module 310 compares the absolute difference D between the amplitudes A1, A2 with the threshold V2. If the absolute difference is not greater than the threshold V2, the result RA3 is negative and the synthesis module 322 detects an absence of whistle. Method 400 returns to step 404. Otherwise, method 400 continues.

During a step 418, the frequency conversion module 312 provides the frequency spectrum F2 of the frame T2 coming from the remote microphone 113.

During a step 420, the frequency peak search module 314 provides the frequency peaks P2 of the frequency spectrum F2.

During a step 422, the first frequency analysis module 316 determines the highest amplitude among the amplitudes of the peaks found in a predefined frequency interval, and compares it to the threshold V3. If the threshold V3 is exceeded (positive result RF1), a whistle is detected by the synthesis module 322 and the method 400 goes to step 428. Otherwise, the method 400 continues.

During a step 424, the second frequency analysis module 318 compares the amplitude of each peak found in a frequency interval with the threshold V4. If the amplitude of each peak found is greater than the threshold V4 (result RF2 positive), a whistle is detected by the synthesis module 322 and the method 400 proceeds to step 428. Otherwise, the method 400 keep on going.

During a step 426, the third frequency analysis module 320 verifies the three conditions described previously and, if they are all verified, provides a positive result RF3. In this case, a whistle is detected by the synthesis module 322 and the method 400 goes to step 428. Otherwise, no whistle is detected by the synthesis module 322 the method 400 returns at step 404.

During a step 428, the transmission module 214 transmits the detection message D and the receiver 118 receives it and transmits it to the timer 120.

During a step 430, the stopwatch 120 stops or restarts depending on its previous state.

The method then returns to step 404 to obtain new frames T1, T2. Preferably, the analysis is fast enough so that the new frames T1, T2 directly follow the previous frames T1, T2, i.e. the new frames T1, T2 start at the samples directly following the previous frames T1, T2.

It will also be noted that the invention is not limited to the embodiments described above. It will indeed appear to those skilled in the art that various modifications can be made to the embodiments described above, in the light of the teaching which has just been disclosed to them.

For example, wrist strap 108 could be attached to the referee's wrist. In this case, the microphone 112 could be at times close to the microphone 113, or even below, when the referee does not use his whistle and keeps his arms along the body. However, if a sound from the ground (such as the squealing of a shoe) is picked up by microphones 112, 113 in this situation, even though module 308 provides a positive RA2 result because microphone 112 is temporarily lower than microphone 113, the result RA3 of the module 310 should be negative, due to the proximity of the two microphones 112, 113, leading to the absence of whistle detection. Thus, the solution described above is robust.

Furthermore, the analysis unit 212 could not comprise an analysis module designed to compare a characteristic of the two signals, but rather modules each dedicated to the analysis either of the signal S1, or of the signal S2, the results being then processed by the synthesis module 320 to detect a whistle or its absence. For example, taking the , modules 308 and 310 could be omitted. Thus, the analysis would indeed relate to the first signal S1 (module 306) and to the second signal S2 (modules 316, 316, 320) but without comparison between the signals S1, S2.

Furthermore, although the detection system described above is portable in order to equip the referee or the judge with it, it could also be used in a fixed manner, for example to detect the whistle of a referee or judge. present at the scorer's table, on the side of the sports meeting. In this case, the detection system could be placed at least partly on the scorer's table, with the two microphones preferably spaced apart from each other as described above.

In the detailed presentation of the invention which is made above, the terms used must not be interpreted as limiting the invention to the embodiments set out in the present description, but must be interpreted to include therein all the equivalents whose provision is within the reach of those skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims (14)

System (102) for detecting an acoustic signal, such as a whistle, from a referee or judge (106) at a sports match, characterized in that it comprises:

• first and second microphones (112, 113) configured to respectively provide first and second signals (S1, S2); and
• an analysis device (204) adapted to analyze the first and second signals (S1, S2) to detect the acoustic signal, in order to stop or restart a timer (120).

A system (102) according to claim 1, wherein the analysis device (204) includes an amplitude determination module (306) adapted to determine an amplitude (A1) of the first signal (S1). System (102) according to claim 2, in which the analysis device (204) comprises an analysis module (306) designed to compare this amplitude (A1) with a predefined threshold. A system (102) according to claim 2 or 3, wherein the amplitude determining module (304) is further adapted to determine an amplitude (A2) of the other (S2) of the first and second signals (S1, S2 ), and wherein the analysis device (204) comprises at least one analysis module (308, 310) designed to compare the amplitudes (A1, A2) of the first and second signals (S1, S2). System (102) according to any one of Claims 1 to 4, in which the analysis device (204) comprises at least one module (316, 318, 320) for frequency analysis of the second signal (S2) supplied by the second microphone (113). System (102) according to any one of claims 1 to 5, further comprising a device (214) for transmitting, in the event of detection of the whistle, a message of detection (D) of the whistle. System (102) according to any one of claims 1 to 6, wherein the first and second microphones (112, 113) are arranged to be placed at least 20 cm, preferably 40 cm, from each other . A system (102) according to any one of claims 1 to 7, wherein the first microphone (112) is attached to a whistle (104) of the referee (106) so as to remain within 5 cm of the whistle ( 104). A system (102) according to claim 8, further comprising a wrist strap (108) to which the first microphone (112) and the whistle (104) are attached. System (102) according to any one of claims 1 to 9, further comprising a system for attaching the referee (106), for example to the referee's belt (106), and in which the second microphone (113) is attached to this attachment system. Installation (100) for controlling the playing time of a sporting event, comprising:

• a whistle detection system (102) according to claim 10; and
• the timer (120) designed to receive the detection message (D), for example via a receiver (118), and stop or start again in response to the detection message.

Method (400) of detecting an acoustic signal, such as a whistle, from a referee or a judge (106) of a sporting match, comprising the analysis of first and second signals (S1, S2) respectively supplied by first and second microphones (112, 113), to detect the whistle, in order to stop or restart a timer (120). Method (400) according to claim 12, comprising, prior to the analysis of the first and second signals (S1, S2), the installation of the first and second microphones (112, 113) on the referee (106) so that the first microphone (112) is within 5 cm of the whistle (104) when the whistle is in use, preferably between 2 and 3 cm, and such that the second microphone (113) is at least 20 cm, preferably 40 cm, further from the whistle (104) than the first microphone (112) when the whistle (104) is used. Computer program downloadable from a communication network and/or recorded on a computer-readable medium, characterized in that it comprises instructions for the execution of the steps of a method according to claim 12, when said program is executed on a computer.