EP2396711A2

EP2396711A2 - Device and process interpreting musical gestures

Info

Publication number: EP2396711A2
Application number: EP10703477A
Authority: EP
Inventors: Dominique David
Original assignee: Commissariat a lEnergie Atomique CEA; Movea SA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Movea SA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2009-02-13
Filing date: 2010-02-12
Publication date: 2011-12-21
Also published as: WO2010092139A3; WO2010092139A2; US20120062718A1; US9171531B2

Abstract

The invention relates to a device for interpreting musical gestures or gestures controlling or serving as musical instruments. Devices of the prior art enable a user to produce music by performing gestures on an adapted instrument or accompanied by pre-recorded musical content. However, none of the devices of the prior art are reliable and robust enough to guarantee satisfactory musical rendition. The invention enables remarkable musical rendition due to the use of microsensors, in particular accelerometers and magnetometers or rate gyros, and due to the adapted processing of the signals from the microsensors. In particular, the processing uses a merging of output data from the microsensors to eliminate false alarms consisting of the movements of the user that are not related to the music. The speed of the musical strokes is also measured by the device of the invention. The invention also enables the user to control the playback of MP3 or WAV music files to be played.

Description

DEVICE AND METHOD FOR INTERPRETATION OF MUSICAL GESTURES

The invention relates to the field of interpreting musical gestures or gestures acting on or as musical instruments. In particular, it relates to a device and a method for processing signals representative of the movements of a music player using an instrument or beating a rhythm of accompaniment. Devices and methods for play or learning have been developed to allow a musical instrument player using an object that simulates said instrument to play a partition, if necessary coupled with the scores of other instruments. The instruments whose interpretation is simulated can be a guitar, a piano, a saxophone, a drums .... In such devices, the scores of the score are generated from the player's actions. Such devices and methods can use buttons that trigger notes, if necessary by combining said buttons. Some devices such as the Wll ™ Music also use a recognition of certain gestures of the musician with the pressure on the buttons to play the score. Since the motion sensor of the Wll ™ Music is an optical sensor that requires a fixed reference, its measurements are both conditioned by the player's position relative to the reference and rudimentary, which considerably limits the possibilities of interpretation. A satisfying musical rendering indeed requires a high accuracy of the capture of the movements of the player who are really intended to operate the instrument. Such a rendering is not within the reach of the devices of the prior art, such as US Pat. No. 5,663,514.

The present invention provides an answer to these limitations of the prior art by using motion sensor measurements according to at least two axes and a processing of their measurements which allow this precision and thus allow a satisfactory musical rendering.

For this purpose, the present invention discloses a device for interpreting gestures of a user comprising at least one measurement input module comprising at least one motion capture assembly according to at least a first and a second axis, a module signal processing sampled at the output of the input module and an output module adapted to reproduce the musical meaning of said gestures, the signal processing module comprising a sub module for analysis and interpretation of gestures comprising a filter function, a function of significant gesture detection by comparing the variation between two successive values in the sample of at least one of the signals coming from at least the first axis of the set of sensors with at least a first selected threshold value and a function significant gesture detection confirmation device, said device being characterized in that said significant gesture detection confirmation function is able to compare at least one of the signals coming from at least the second axis of the set of sensors with at least one second threshold value chosen. Advantageously, the filtering function is capable of being executed by at least one pair of two successive low-pass recursive filters adapted to receive at least one of the output signals of the module as input.

Advantageously, the significant gesture detection function is able to identify sign changes between two successive values in the sample of the difference between at least one output of the first filter of at least one of the filter pairs at the current value and at least one output of the second filter of the same pair of filters for the same signal at the previous value.

Advantageously, the sub-module for analyzing and interpreting gestures further comprises a function for measuring the velocity of the gesture detected at the output of the detection confirmation function. Advantageously, the velocity measurement function is able to calculate the stroke (Max-Min) between two significant gestures detected. Advantageously, the second filter is able to operate at a cutoff frequency lower than that of the first filter. Advantageously, the input module comprises at least a first accelerometer type sensor and a second sensor selected from the group of magnetometer type sensors and gyrometer.

Advantageously, the significant gesture detection function is able to receive at least one output of the second recursive filter of one of the pairs of filters applied to at least one of the signals of the first sensor. Advantageously, the significant gesture detection confirmation function is able to receive as input at least one output of the second recursive filter of one of the pairs of filters applied to at least one of the signals of the second sensor. Advantageously, the threshold chosen for the significant gesture detection confirmation function is of the order of 5/1000 relative value of the filtered signal. Advantageously, the input module receives the signals from at least two sensors positioned on two independent parts of the body of the user, a first sensor providing via one of the pairs of recursive filters an input signal of the gesture detection function. significant and a second sensor providing via a pair of recursive filters an input signal of the gesture velocity measurement function detected at the output of the significant gesture detection confirmation function. Advantageously, the signal processing module comprises an input sub-module of pre-recorded multimedia contents.

Advantageously, the multimedia content input sub-module comprises a function of partitioning said multimedia time-slot contents that can be used to perform a second confirmation of detection of the significant gestures detected. Advantageously, the input module is able to transmit to the processing module a signal representative of the position of the user in a plane substantially orthogonal to the direction of the detected significant gesture to make a second confirmation. Advantageously, the output module comprises a reproduction sub-module of a prerecorded file of signals to be reproduced and in that the processing module comprises a temporal control sub-module of said prerecorded signals, said reproduction sub-module being adapted to be programmed to determine the times when are expected to control the rate of scrolling of the file, and in that said time control sub-module is able to calculate for a certain number of control keystrokes a corrected speed factor (CSF) relative preprogrammed keystrokes in the reproduction sub-module and keystrokes actually entered in the temporal control sub-module and a relative intensity factor velocities said keystrokes actually entered and expected and then adjust the scroll rate of said under- time control module for adjusting said corrected speed factor (CSF) to the following keystrokes at a selected value and the intensity of the output signals of said reproduction sub-module according to said relative velocity intensity factor. Advantageously, the velocity of the typing input is calculated from the deviation of the signal output of the second sensor.

Advantageously, the input module further comprises a submodule capable of interpreting user gestures whose output is used by the temporal control sub-module to control a characteristic of the audio output selected from the group constituted by the vibrato and tremolo.

Advantageously, the reproduction sub-module comprises a tag placement function in the prerecorded signal file to be reproduced at the times when the file's scroll rate control keys are expected, said tags being generated automatically according to the rhythm of pre-recorded signals that can be moved by a MIDI interface.

Advantageously, the value chosen in the time control sub-module for adjusting the running speed of the reproduction sub-module is equal to a value chosen from a set of calculated values, one of whose limits is calculated by applying a factor of CSF rate equal to the ratio of the time interval between the next tag and the previous tag minus the time interval between the current tap and the previous tap at the time interval between the current tap and the previous tap and whose the other values are calculated by linear interpolation between the current value and the value corresponding to that of the terminal used for the application of the CSF speed factor.

Advantageously, the value chosen in the time control sub-module for adjusting the running speed of the reproduction sub-module is equal to the value corresponding to that of the terminal used for applying the CSF speed factor.

The invention also discloses a method for interpreting significant gestures of a user comprising at least one measurement input step from at least one motion capture set according to at least a first and a second axis, a treatment stage of sampled signals at the output of the input step and an output step adapted to reproduce the musical meaning of said gestures, the signal processing step comprising a sub-step of analysis and interpretation of gesture comprising at least one filtering step, a significant gesture detection function by comparing the variation between two successive values in the sample of at least one of the signals coming from at least the first axis of the set of sensors with at least a first value chosen threshold and a significant gesture detection confirmation function, said method being characterized in that said significant gesture detection confirmation function is able to compare at least one of the signals coming from at least the second axis of the set of sensors with at least a second threshold value chosen. Advantageously, the output step comprises a sub-step of reproducing a prerecorded file of signals to be reproduced and in that the processing step comprises a substep of time control of said prerecorded signals, said substep of reproducing being able to determine the times when are awaited control strokes of the file scroll rate, and said substep time control being able to calculate for a number of control strokes a corrected speed factor (CSF) relative preprogrammed keystrokes in the reproduction sub-step and keystrokes actually entered during the time control sub-step and a relative intensity factor of the velocities of said keystrokes actually entered and expected and then adjusting the scroll rate of said prerecorded file to adjust said corrected speed factor (CSF) to the following keystrokes at a chosen value and the sity of the output signals of the reproduction step according to said relative velocity intensity factor.

Another advantage of the invention is that it uses micro sensors (accelerometers and magnetometers or gyrometers) at low cost. It can be used to play with the hands and / or beat the measure with the feet. It does not require a long learning and can be used by several players. It can be used with a large number of movements and instruments. It can also be used without any object simulating any instrument.

In addition, the device and the method of the invention can be used to control the scrolling rate and the reproduction volume of an mp3 or wav audio file ensuring satisfactory musical performance. Moreover, the invention makes it possible, in this embodiment, to carry out the control of the scrolling of the prerecorded audio files in an intuitive manner. New scroll control algorithms can also be easily integrated into the device of the invention.

The invention will be better understood, its various features and advantages will emerge from the following description of several embodiments and its accompanying figures, including:

FIG. 1 represents different contexts of use of the invention according to several embodiments;

FIG. 2 is a simplified representation of a functional architecture of a device for interpreting musical gestures according to one embodiment of the invention;

FIG. 3 (3a, 3b) represents a general flowchart of the treatments in one embodiment of the invention using an accelerometer and a magnetometer or a gyrometer;

FIG. 4 represents a flowchart of the filtering of the signals of the motion sensors in one embodiment of the invention;

FIG. 5 represents a flow diagram of the detection of the power of the signals of the motion sensors in one embodiment of the invention;

FIG. 6 represents a general flowchart of the treatments in one embodiment of the invention using only a gyrometer; FIG. 7 is a simplified representation of a functional architecture of a device for controlling the running speed of a prerecorded audio file by using the device and the method of the invention; FIGS. 8a and 8b show two cases of control of the scrolling of an audio file where respectively the typing speed is higher / lower than that of scrolling of the audio band;

FIG. 9 represents a flowchart of the processes of the function of measuring the velocity of the keystroke in a mode of control of the scrolling of an audio file;

FIG. 10 represents a general flowchart of the processes making it possible to control the scrolling of an audio file;

FIG. 11 represents a detail of FIG. 10 which shows the rhythmic control points desired by a user of a device for controlling the scrolling of an audio file;

FIG. 12 represents an expanded flowchart of a method for temporally controlling the scrolling of an audio file.

FIG. 1 shows three modes 10, 120A and 120B of input of musical gestures in a processing module 20 for reproduction by a musical synthesis module 30.

On the left of Figure 1 are represented from top to bottom the three input modes 10 of musical gestures: - A musician 1 10 plays a guitar on which were fixed one or more motion sensors such as MotionPod ™ of Movea ™; it is then the movements of the guitar that are measured by the motion sensors and supplied to the processing unit 20; - A 120A musician directly carries motion sensors of the same type on a part of the body (hand, forearm, arm, foot, leg, thigh, etc.); he can play the score of an instrument or simply beat a rhythm;

- A 120B musician can also operate a GyroMouse ™ or a Movea AirMouse ™ which is a three-dimensional remote control that includes a three-axis gyrometer to control a point in motion on a used plane, offering the possibility to use either the point displacements are the measurements of one or more axes gyrometers. A MotionPod comprises a tri-axis accelerometer, a tri-axis magnetometer, a pre-processing capability for preforming signals from the sensors, a radiofrequency transmission module of said signals to the processing module itself and a battery. This motion sensor is called "3A3M" (three axes of accelerometer and three axes of magnetometer). Accelerometers and magnetometers are small, low-cost, low-cost commercial micro-sensors, such as a Kionix ™ three-way accelerometer (KXPA4 3628) and HoneyWell ™ HMC1041 Z magnetometers (one-way). vertical) and HMC1042L for the 2 horizontal tracks. Other suppliers include Memsic ™ or Asahi Kasei ™ for magnetometers and STM ™, Freescale ™, Analog Device ™ for accelerometers, to name just a few. In the MotionPod, for the 6 signal channels, there is only one analog filtering and then, after digital analog conversion (12 bits), the raw signals are transmitted by a radio frequency protocol in the Bluetooth ™ band (2.4GHz ) optimized for consumption in this type of applications. The data is therefore raw to a controller that can receive data from a set of sensors. They are read by the controller and made available software. The sampling rate is adjustable. By default, it is set at 200 Hz. Higher values (up to 3000 Hz or more) can nevertheless be envisaged, allowing greater accuracy in the detection of shocks, for example. The radio frequency protocol of the MotionPod makes it possible to guarantee the provision of the data to the controller with a controlled delay, which should not exceed 10ms (at 200 Hz), which is important for the music.

An accelerometer of the above type makes it possible to measure longitudinal displacements along its three axes and, by transformation, angular displacements (except around the direction of the earth's gravitational field) and orientations with respect to a Cartesian reference system in three dimensions. A set of magnetometers of the above type makes it possible to measure the orientation of the sensor to which it is fixed with respect to the terrestrial magnetic field and thus displacements and orientations with respect to the three axes of the reference frame (except around the direction of the magnetic field earthly). The 3A3M combination provides complementary and smooth motion information. In fact, in the invention only the information relating to one of the axes, the vertical axis Z or one of the other two axes is used. We can therefore be satisfied in principle with a single-axis sensor of each type, when two types of sensors (accelerometer and magnetometer or accelerometer and gyrometer) are used. In practice, given the low cost availability of 3A3M sensor modules incorporating transmission and processing of the six channels, this is the preferred approach.

Other motion sensors may be used, for example a combination of accelerometer and gyrometer (so-called "3A3G" sensors) or even a single three-axis gyrometer, as explained below in the description in comment to other figures.

When several sets of motion sensors are used, the remote controller of the MotionPod (at the input of the processing module 20, 210) synthesizes the signals of the sensor assemblies. A compromise must be found between the number of sensors, the sampling frequency of the sensors and the energy consumption autonomy of the sensor assemblies. In the remainder of the description, the term "output signal of the accelerometer or magnetometer in the singular indifferently the outputs of the controller depending on whether the input data come from a single sensor module 3A3M or a set of modules 3A3M synthesized in the controller.

The AirMouse includes two gyrometer type sensors, each with an axis of rotation. The gyrometers used are from the Epson reference XV3500. Their axes are orthogonal and deliver the pitch angles (yaw or rotation around the axis parallel to the horizontal axis of a plane facing the user of the AirMouse) and yaw (pitch or rotation around a axis parallel to the vertical axis of a plane facing the user of the AirMouse). The instantaneous pitch and yaw speeds measured by the two gyrometer axes are transmitted by radio frequency protocol to a controller of the input module (10) and converted by said controller in motion of a cursor in a screen facing the user. . In the application of the invention it is possible to use either one of the cursor control signals (in Z or Y), or both, or a direct measurement signal at the output of one of the gyrometer axes. The functionalities and the architecture of the processing module 20 will be discussed in connection with FIG. 2.

An output module 30 reproduces the sounds produced by the combination of pre-recorded contents and the capture of the musical gestures produced by the player via the input module 10. It may be a simple speaker or a a synthesizer.

The functional architecture of the device of the invention is described in FIG. 2. The modules 10 and 30 are not returned. The module 20 carries out the processing of the signals received from the input module 10 within a module of FIG. Gesture analysis and interpretation 210 whose outputs are provided to a module for calculating the music content control data 230. Pre-recorded multimedia content is also provided by a module 220 to the module 230. To correctly specify the algorithm analysis and interpretation of the musical gestures implanted in the module 210, it is necessary to take into account the specificity of the said gestures. In particular, playing a 5 minute piece of music for example by beating a moderately fast tempo at 120 bpm (beat per minute) results in 600 beats performed by the user. However, in a musical context, a single error results in a rupture of meaning and a loss of interest of the device. In case of false alarm, the system detects non-existent beats, in case of non-detection obviously the play of the piece is interrupted. However, in situation of musical interpretation by beat of tempo, the user adopts a gesture on the one hand which is his own, on the other hand admitting a certain variability within his own gestures. Moreover, human-specific motor physiological phenomena, themselves dependent on the beat speed, are superimposed on this variability (we have a quasi-sinusoidal mode at high speed, but with strong rebounds at slow speed). These findings have several consequences:

- it is necessary to use algorithms achieving a fidelity of the order of 1 per 1000, a very high value in a context of little known variability (human expressive movement);

- the only accelerometers do not allow today to reach such a performance, for at least two reasons (rebounds in case of average or slow speed, difficulty in anticipating and therefore producing a correct movement power information), hence the choice made to use bimodal sensors;

- The processing algorithms must be very adaptable. Moreover, it seems that the behavior of the user depends directly on his interaction with the content he is interpreting. It is therefore necessary to provide a process in situation, that is to say by putting the human system in an action / perception loop including all aspects involved (content, brain and cognitive, gestures, actuators, sensors. .). To meet these specifications, the general processing principle implemented in module 210 has the following two characteristics:

an adaptive processing to eliminate the components of the signals having slow variations (of the order of one second);

use of the outputs of a sensor (a magnetometer or a gyrometer) to detect a strike;

- the use of the outputs of the other sensor (the accelerometer or one of the measurements of the gyrometer if this sensor is used alone), to measure the intensity of the striking.

The module 220 makes it possible to insert pre-recorded contents of the MIDI (Musical Instrument Digital Interface) type coming from an electronic musical instrument, audio coming from a reader (MP3 - MPEG (Moving Picture Expert Group) 1/2 Layer 3, WAV - WAVeform audio format, WMA - Windows Media Audio, etc.), multimedia, images, video, etc. through a suitable interface. The outputs of the module 220 are provided concurrently with the module 210 (to allow consideration of the reactions of the music player) and the module 230 to be subsequently reproduced at the output of the processing device.

The module 230 makes it possible to synthesize the musical gestures interpreted by the module 210 and the pre-recorded contents at the output of the module 220. The simplest mode is to play a fragment, for example, encoded in MP3 or midi file (or file video) every time a strike is detected by the module 210, which will then sequentially seek the fragments in the module 220. This mode allows to many interesting applications. It is much more flexible and powerful than 220 integrates a method such as the one we disclosed in the application No. FR07 / 55244 entitled "computer-assisted music interpretation system" and having as holder the inventor of the this request. The device disclosed in this invention comprises two memories one of which comprises the musical data which define the totality of the musical events constituting the piece of music to be interpreted and the other the sequence of actions necessary for the reproduction of the stored musical events as well as the means for establishing said musical information by comparing the data stored in the first memory of the musical data and the memory of the sequence of the actions. In this case, the user will have complete control over what he wants to play and when, and what is left to the initiative of the machine (eg an accompaniment).

FIG. 3 (cut at 3a and 3b for readability reasons) represents a general flowchart of the treatments in one embodiment of the invention using an accelerometer and a magnetometer or a gyrometer. In the remainder of the description relating to this figure, whenever the word magnetometer is used, it denotes indifferently a magnetometer or a gyrometer. All the treatments are done in software in the module 210.

The treatments firstly comprise a low-pass filtering of the outputs of the sensors of the two modalities (accelerometer and magnetometer) whose detailed operation is explained in FIG. 4.

This filtering of the output signals of the motion sensor controller uses a recursive approach of order 1. The gain of the filter may for example be set at 0.3. In this case, the filter equation is given by the following formula:

Output (z (n)) = 0.3 ^* lnput (z (n-1)) + 0.7 ^* Output (z (n-1))

Where, for each of the modalities: z is the reading of the modality on the axis used; n is the reading of the current sample; n-1 is the reading of the previous sample. The treatment then comprises a low-pass filtering of the two modalities with a cut-off frequency lower than that of the first filter. This lower cut-off frequency results from the choice of a coefficient of the second filter which is lower than the gain of the first filter. In the case chosen in the example above, where the coefficient of the first filter is 0.3, the coefficient of the second filter can be set at 0.1. The equation of the second filter is then (with the same notation as above): Output (z (n)) = 0.1 ^* lnput (z (n-1)) + 0.9 ^* Output (z (n-1))

Then, the processing comprises a detection of a zero of the derivative of the output signal of the accelerometer with the measurement of the output signal of the magnetometer.

The following notations are applied: - A (n) the output signal of the accelerometer in the sample n;

AF1 (n) the signal of the accelerometer at the output of the first recursive filter in the sample n;

AF2 (n) the signal AF1 filtered again by the second recursive filter in the sample n; - B (n) the magnetometer signal in the sample n;

- BF1 (n) the magnetometer signal at the output of the first recursive filter in the sample n;

- BF2 (n) the signal BF1 filtered again by the second recursive filter in the sample n. Then, the following equation allows to compute a filtered derivative of the accelerometer signal in sample n: FDA (n) = AF1 (n) - AF2 (n-1)

A negative sign of the product FDA (n) ^* FDA (n-1) indicates a zero of the derivative of the filtered signal of the accelerometer and thus detects a strike.

For each of these zeros of the filtered signal of the accelerometer, the processing module checks the intensity of the deviation of the other modality at the filtered output of the magnetometer. If this value is too low, the strike is considered not as a primary strike but as a secondary or ternary strike and discarded. The threshold for excluding non-primary strikes depends on the expected amplitude of the deviation of the magnetometer. Typically, this value will be of the order of 5/1000 in the envisaged applications. This part of the treatment thus makes it possible to eliminate the insignificant strikes.

Finally, for all the primary keystrokes detected, the processing module calculates a velocity signal (or volume) of the strike by using the deflection of the filtered signal at the output of the magnetometer.

The value DELTAB (n) is introduced into the sample n which can be considered as the pre-filtered signal of the centered magnetometer and which is calculated in the following way: DELTAB (n) = BF1 (n) - BF2 (n)

The minimum and maximum values of DELTAB (n) are stored between two primary keystrokes detected. An acceptable value VEL (n) of the velocity of a primary strike detected in a sample n is then given by the following equation:

VEL (n) = Max {DELTAB (n), DELTAB (p)} - Min {DELTAB (n), DELTA (p)} Where p is the index of the sample in which the previous primary keystroke was detected. Velocity is thus the race (difference Max-Min) of the derivative of the signal between two detected primary strikes, characteristics of musical gestures.

This part of the treatment is illustrated in Figure 5.

An adaptive processing is thus carried out because the processing of the magnetic modality includes a centering of the signal. The signal itself subtracts its own slow variations (see formula above). For example, if the user turns 60 ° to the right, the magnetic signals received will be shifted, but the corresponding offset will be removed by the subtraction in question, keeping only the rapid variations due to the musical rhythm.

This treatment according to the invention makes it possible to interpret, without a single error, pieces of a few minutes, with fine control at the same time of the speed and the volume of play, both when the sensors are placed on the player's hand or when they are located on the foot of a player who beats the measure with his foot. The device of the invention can be used as it is, that is to say without any calibration, even magnetometers (we actually only work on signals cleared of continuous components). However, it may be advantageous to perform a calibration at the beginning of the game, which calibration can be repeated with each strike. It is then necessary to put in parallel the filtering having for object to free itself from the slow variations, and this calibration with each keystroke. In this case, it is no longer necessary to filter by the second filter. On the contrary, the fact of calibrating will ensure that in a position "almost" known to the user (at the moment of the keystroke) the magnetometer provides a reference datum thanks to the calibration. In a way, the data are realigned by these calibrations, whereas they were previously by the second filtering. One can also imagine to cumulate the second filtering and the calibration.

In addition, all of these treatments provide:

a trigger signal that can be used to synchronize the play of a MIDI file, or to synchronize the scrolling of an MP3, WAV or WMA type audio file, which is described below;

- An amplitude signal, which can be used to control the volume of a MIDI playback (usually in general, the velocity of the notes played) or the playback volume of an audio file.

Figure 6 shows a general flowchart of the treatments in one embodiment of the invention using only a gyrometer. For example, the input device is the Movea AirMouse or GyroMouse (player 12OB of FIG. 1). The processing carried out in the module 210 is comparable to the processing described above, except that we only use one sensor data item, which can be considered in an approximate manner that it is physically halfway between the accelerometer data. and the magnetometer data that provides absolute angles. The gyrometer is used here in the two detections: the one of the primary striking, with a treatment comparable to that of the accelerometer higher, except that the second filtering is not necessary, because a first filtering is already carried out in the AirMouse or the GyroMouse. Both filtering can however be cumulated. Crossings are detected here between the derivative of the signal coming from the AirMouse and this same filtered low pass signal recursively. The gesture power detection is also based on a measurement of the stroke between two successive primary keystrokes detected. This velocity calculation yields usable results, but is less effective than the two-mode approach. Because of the intermediate nature between measurements of an accelerometer and measurements of a magnetometer of the measurements of the gyrometer, it is sufficient for the two detections, but it is less effective also than the dedicated methods. This solution achieves a compromise that is not optimal but that can give other opportunities. On the one hand, the AirMouse is more accessible at least for the moment to the general public and is therefore of interest from this point of view even if we do not have the finesse of controlling the bimodality. In a way the Airmouse is between the Wii Music and a sensor providing two modes of motion capture. In addition, the mouse buttons provide complementary commands to, for example change a sound, or move to the next song, or to operate the pedal of a sampled piano for example.

The various embodiments of the invention may be improved by the variants set forth below.

An alternative embodiment consists in using two sensor modules in each of the player's hands, one of the modules being dedicated to the detection of primary keystrokes and the other to the measurement of velocity.

It is also possible to exploit the other axes of the sensors to determine a heading information that allows to introduce a pan control and thus improve the centering to make detections completely independent of the player's positioning. Another embodiment variant for improving robustness consists in exploiting the knowledge of the current musical content. We then introduce time windows deduced from current content in which a hit detected as primary is not taken into account because incoherent with said current content. In fact, this consistency will exploit a measure of the actual playing speed of the person (the time between the last two keystrokes) and compare it to the time between the two fragments contained in the module 220. If these two measures differ too much (for example by more than 25%), then an acceleration (or a deceleration) that seems excessive compared to what is played. It is deduced that there is a false detection. When such a false detection is identified, it is in fact always a strike devoid of musical meaning, which we deduce that this is an untimely detection. It is therefore purely and simply ignored (it does not trigger any multimedia fragment). Conversely, a non-detection can be palliated simply, the rhythmic elements of the piece being played by exploiting the last two keystrokes detected.

FIG. 7 is a simplified representation of a functional architecture of a device for controlling the running speed of a prerecorded audio file by using the device and method of the invention.

The characteristics of the module 720, the input of the signals to be reproduced, the timing control module 730 and the audio output module 740 are described below. The motion sensors of the Motion Pod or Air Mouse type described above are, in the embodiment described here, used to control the scrolling rate of a prerecorded audio file.

The gesture analysis and interpretation module 712, adapted to this embodiment, provides signals that can be directly exploited by the time control processor 730. The signals along an axis of the accelerometer and the magnetometer of the MotionPod are combined according to the method described above.

The treatments firstly advantageously comprise a double low-pass filtering of the outputs of the sensors of the two modalities (accelerometer and magnetometer) which has already been described above in relation with FIG. 4.

Then, the processing comprises the detection of a zero of the derivative of the signal at the output of the accelerometer with the measurement of the signal at the output of the magnetometer according to the methods explained above in comments to Figures 3a and 3b.

Explicit below is the modalities allowing the device of the invention to control the scrolling of a file of mp3, wav or similar type. A pre-recorded music file 720 to one of standard formats (MP3, WAV, WMA, etc.) is taken from a storage unit by a reader. To this file is associated another file with time marks or "tags" at predetermined times; for example, the table below shows nine tags at times in milliseconds that are listed next to the index of the decimal point:

1.0;

2, 335.411194;

3, 649.042419;

4, 904.593811;

5, 1160.145142;

6, 1462.1604;

7, 1740.943726;

8, 2054.574951;

9, 2356.59;

The tags can advantageously be placed at beats of the same index in the piece that is played. There is no constraint on the number of tags. Several techniques are possible to place tags in a pre-recorded piece of music:

- Manually, by searching on the musical wave the point corresponding to a rhythm where a tag must be placed; it is a possible but tedious process;

Semi-automatically, listening to the pre-recorded music track and pressing a keyboard key computer or MIDI keyboard when a rhythm where a tag is to be placed is heard;

- Automatically, using a rhythm detection algorithm that puts the tags in the right place; today, the algorithms are not reliable enough so that the result does not have to be retouched using one of the first two processes, but we can complete this automatism by a manual phase of retouching the created tags file.

The prerecorded signal input module 720 to be reproduced can process different types of audio files, in MP3, WAV, WMA formats. The file may also include other multimedia content than a simple sound recording. It may be for example video contents, with or without soundtrack, which will be tagged and whose scrolling can be controlled by the input module 710.

The time control processor 730 synchronizes the signals received from the input module 710 and the pre-recorded music piece 720, in a manner commented on in FIGS. 9A and 9B.

The audio output 740 reproduces the pre-recorded piece of music from the module 720 with the variations of rhythm introduced by the commands of the input module 710 interpreted by the time control processor 730. Any sound reproduction device does the same. case, including headphones, speakers.

Figs. 8A and 8B show cases where respectively the typing speed is higher / lower than the running speed of the audio band.

During the first hit marked by the motion sensor 71 1, the audio player of the module 720 starts playing the pre-recorded piece of music at a given rate. This rhythm can for example be indicated by several small prior strikes. Whenever the processor of time control receives a striking signal, the current playing speed of the user is calculated. This can for example be expressed as the speed factor SF (n) calculated as the ratio of the time interval between two successive tags T and n + 1 of the pre-recorded song at the time interval between two keystrokes H successive n and n + 1 of the user: SF (n) = [T (n + 1) - T (n)] / [H (n + 1) - H (n)]

In the case of Figure 8a, the player accelerates and advances the pre-recorded track: a new keystroke is received by the processor before the audio player has reached the sample of the piece of music where the tag is placed corresponding to this hit. For example, in the case of the figure, the speed factor SF is 4/3. Upon reading this SF value, the time control processor skips the reading of the file 720 to the sample containing the index mark corresponding to the keystroke. Part of the pre-recorded music is lost, but the quality of the musical rendering is not too disturbed because the attention of those who listen to a piece of music usually focuses on the elements of the main rhythm and the tags will normally be placed on these elements of the main rhythm. In addition, when the player jumps to the next tag, which is an element of the main beat, the listener who is waiting for that item, will pay less attention to the absence of the part of the pre recorded song that has been skipped, this jump thus passing almost unnoticed. The quality of listening can be further enhanced by smoothing the transition. This smoothing can for example be operated by interpolating a few samples (about ten) between before and after the tag to which the player is blown up to catch the player's typing speed. Playback of the pre-recorded song continues at the new speed resulting from that jump.

In the case of Figure 8b, the player slows down and lags behind the pre-recorded music track: the audio player reaches a point where a strike is expected before it is performed by the player. In the context of a musical listening, it is of course not possible to stop the player to wait for the keystroke. Therefore, audio playback continues at the current speed until the expected keystroke is received. It is at this moment that the speed of the reader is changed. A crude method is to fix the the speed of the reader according to the speed factor SF calculated at the moment the keystroke is received. This method already gives qualitatively satisfactory results. A more elaborate method is to compute a corrected playback speed that will re-synchronize the playback tempo to the player's tempo.

Three positions of the tags at time n + 2 (in the time scale of the audio file) before changing the speed of the reader are indicated in FIG. 3B:

the first starting from the left T (n + 2) is that corresponding to the speed of movement prior to the slowdown of the player;

the second, NT ₁ (n + 2), is the result of the calculation consisting in adjusting the speed of the player's scrolling speed to the player's typing speed by using the speed factor SF; we see that in this case the tags remain ahead of the keystrokes;

the third, NT ₂ (n + 2), is the result of a calculation using a corrected speed factor CSF; this corrected factor is calculated so that the dates of the following keystroke and tag are identical, which is seen in Figure 3B.

CSF is the ratio of the time interval from the n + 1 strike to the n + 2 tag relative to the time interval from the n + 1 strike to the n + 2 strike. Its formula is: CSF = {[T (n + 2) - T (n)] - [H (n + 1) - H (n)]} / [H (n + 1) - H ( n)] It is possible to improve the musical rendering by smoothing the profile of the tempo of the player. For this, instead of adjusting the speed of the reader as indicated above, it is possible to calculate a linear variation between the target value and the starting value over a relatively short duration, for example 50 ms and to increase the speed of the scrolling through these different intermediate values. The longer this adjustment time, the smoother the transition will be. This allows a better rendering, especially when many notes are played by the player between two keystrokes. But the smoothing is obviously at the expense of the dynamics of the musical response. Another improvement, applicable to the embodiment comprising one or more motion sensors, is to measure the player's striking energy or velocity to control the volume of the audio output. The manner in which velocity is measured indicated earlier in the description. This part of the processing carried out by the module 712 for analysis and interpretation of gestures is shown in FIG. 9. For all the primary keystrokes detected, the processing module calculates a velocity signal (or volume) of the striking using the deflection of the filtered signal at the output of the magnetometer. Using the same notations as above in comments of FIGS. 3a and 3b, the value DELTAB (n) is introduced into the sample n which can be considered as the pre-filtered signal of the centered magnetometer and which is calculated in the following manner : DELTAB (n) = BF1 (n) - BF2 (n) The minimum and maximum values of DELTAB (n) are stored between two detected primary keystrokes. An acceptable value VEL (n) of the velocity of a primary striking detected in a sample n is then given by the following equation: VEL (n) = Max {DELTAB (n), DELTAB (p)} - Min {DELTAB (n), DELTA (p)} Where p is the index of the sample in which the previous primary keystroke was detected. Velocity is thus the race (difference Max-Min) of the derivative of the signal between two detected primary strikes, characteristics of musical gestures. It is also possible, in this embodiment comprising several motion sensors, to control by other gestures other musical parameters such as the spatial origin of the sound (or panning), the vibrato or the tremolo. For example, a sensor in one hand will detect the striking while another sensor held in the other hand will detect the spatial origin of sound or tremolo. Rotations of the hand can also be taken into account: when the palm of the hand is horizontal, one obtains a value of the spatial origin of the sound or the tremolo; when the palm is vertical, another value of the same parameter is obtained; in both cases, the movements of the hand in space provide the detection of the strikes. In the case where a MIDI keyboard is used, conventionally used controllers can also be used in this embodiment of the invention to control the spatial origin of sounds, tremolo or vibrato.

The invention can be advantageously implemented by processing the keystrokes via a MAX / MSP program.

Figure 10 shows the general flowchart of the treatments in such a program. The display of the figure shows the waveform associated with the audio piece loaded in the system. There is a classical part to listen to the original piece.

At the bottom left is a portion, shown in Figure 1 1, to create a table containing the list of rhythmic control points desired by the person: listening to the song he taps a key at every moment that he wishes to type in the subsequent interpretation. Alternatively these times can be designated by the mouse on the waveform. Finally, they can be edited. Figure 12 details the portion of Figure 10 at the bottom right that represents the time control that is applied.

In the right column, the coefficient of acceleration / deceleration SF is calculated by comparing the duration existing between two consecutive marks on the one hand in the original piece, on the other hand in the current game of the user. The formula for calculating this speed factor is given above in the description.

In the central column, a timeout is set to stop the scrolling of the audio if the user has no longer typed for a time depending on the current musical content. In the left column, is the heart of the control system. It is based on a temporal compression / expansion algorithm. The difficulty is to transform a "discrete" control thus intervening at consecutive instants, in a regular modulation of the speed. Otherwise, the hearing suffers on the one hand of total interruptions of the sound (when the player slows down), on the other hand of clicks and abrupt jumps when he accelerates. These flaws, which make such an approach unrealistic because of an audio output unusable musically are resolved in the developed implementation. It consists :

- to never stop sound scrolling even if there is a substantial slowdown of the user. The "if" object in the left column detects whether it is slowing down or accelerating. In the event of a slowdown, the reading speed of the algorithm is changed, but no jump is made in the audio file. The new reading speed is not necessarily exactly the one calculated in the right column (SF), but can be corrected (CSF speed factor) to take into account that we have already exceeded in the audio the corresponding mark at the last action of the player;

- Jump to the audio file during an acceleration (second branch of the "if" object). In this case, it has little subjective impact on hearing, if the control marks correspond to musical moments sufficiently important on the psycho-acoustic level (here there is a parallel to perform with the basis of MP3 compression , which poorly encodes the less significant frequencies, and richly the preponderant frequencies). This is the macroscopic time domain, some moments in the listening of a piece are more significant than others, and it is on these moments that we wish to be able to act.

The examples described above are given by way of illustration of embodiments of the invention. They in no way limit the scope of the invention which is defined by the following claims.

Claims

1. Device for interpreting gestures of a user comprising at least one measurement input module (10) comprising at least one motion capture assembly according to at least a first and a second axis, a processing module (20) for signals sampled at the output of the input module and an output module (30) adapted to reproduce the musical meaning of said gestures, the signal processing module (20) comprising a sub module for analysis and interpretation of gestures ( 210) comprising a filtering function, a significant gesture detection function by comparing the variation between two successive values in the sample of at least one of the signals coming from at least the first axis of the sensor set with at least one of minus a first selected threshold value and a significant gesture detection confirmation function, said device being characterized in that said significant gesture detection confirmation function tif is able to compare at least one of the signals coming from at least the second axis of the set of sensors with at least a second threshold value chosen.

2. device for interpreting gestures according to claim 1 characterized in that the filtering function is adapted to be performed by at least one pair of two successive recursive low-pass filters adapted to receive at least one of the output signal input of the module (10).

3. A gesture interpretation device according to claim 2, characterized in that the significant gesture detection function is able to identify sign changes between two successive values in the sample of the difference between at least one output of the first filter. at least one of the filter pairs at the current value and at least one output of the second filter of the same pair of filters for the same signal at the previous value.

4. device for interpreting gestures according to one of claims 1 to 3 characterized in that the sub module for analyzing and interpreting gestures (210) further comprises a function for measuring the velocity of the gesture detected in exit of the detection confirmation function.

5. device for interpreting gestures according to claim 4 characterized in that the velocity measurement function is able to calculate the stroke (Max-Min) between two significant gestures detected.

6. device for interpreting gestures according to claim 2 and one of claims 3 to 5 characterized in that the second filter is adapted to operate at a cutoff frequency lower than that of the first filter.

7. Gesture interpretation device according to claim 1 characterized in that the input module comprises at least a first accelerometer-type sensor and a second sensor selected from the group of sensors type magnetometer and gyrometer.

8. device for interpreting gestures according to claim 2 and claim 7 characterized in that the function of significant gestures detection is adapted to receive at least one output of the second recursive filter of one of the filter couples applied to at least one of the signals of the first sensor.

9. A gesture interpretation device according to claim 2 and claim 7, characterized in that the significant gesture detection confirmation function is capable of receiving at least one output of the second recursive filter of one of the pairs of inputs. filters applied to at least one of the second sensor signals.

10. device for interpreting gestures according to claim 9 characterized in that the selected threshold of the significant gesture detection confirmation function is of the order of 5/1000 relative value of the filtered signal.

1 1. Gesture interpretation device according to claim 2 and claim 4 characterized in that the input module (10) receives the signals of at least two sensors positioned on two independent parts of the user's body, a first sensor providing via one of the pairs of recursive filters a signal at the input of the significant gesture detection function and a second sensor providing via one of the recursive filter pairs an input signal of the gesture velocity measurement function detected at the output of the significant gesture detection confirmation function.

12. Apparatus for interpreting gestures according to one of claims 1 to 1 1 characterized in that the signal processing module (20) comprises a submodule (220) input pre-recorded multimedia content.

13. Apparatus for interpreting gestures according to claim 12 characterized in that the sub-module (220) multimedia content input comprises a partitioning function of said multimedia content in time slots suitable for use in performing a second confirmation of detection of significant gestures detected.

14. device for interpreting gestures according to one of claims 1 to 13 characterized in that the input module (10) is adapted to transmit to the processing module (20) a signal representative of the position of the user in a plane substantially orthogonal to the direction of the significant gesture detected to make a second confirmation.

15. Apparatus for interpreting gestures according to one of claims 1 to 13 characterized in that the output module (30) comprises a sub-module (720) for reproducing a prerecorded file of signals to be reproduced and in that that the processing module (20) comprises a sub-module (730) for the temporal control of said pre-recorded signals, said reproduction sub-module (720) being able to be programmed to determine the times when control check strikes are expected. the rate of scrolling of the file, and in that said time control sub-module (730) is capable of calculating for a certain number of control keystrokes a corrected speed factor (CSF) of preprogrammed keystrokes in the sub-module of reproducing (720) and keystrokes actually entered into the temporal control sub-module (730) and a relative intensity factor of the velocities of said keystrokes actually entered and expected and then adjusting the rhythm me of scrolling of said sub- time control module for adjusting said corrected speed factor (CSF) to the following keystrokes at a selected value and the intensity of the output signals of said reproduction sub-module according to said relative velocity intensity factor.

6. A control device according to claim 15, characterized in that the velocity of the typing input is calculated from the deviation of the signal output of the second sensor.

17. Device for interpreting gestures according to claim 1, characterized in that the input module (710) further comprises a submodule adapted to interpret gestures of the user whose output is used by the submodule time control unit (730) for controlling a characteristic of the audio output selected from the group consisting of vibrato and tremolo.

18. Apparatus for interpreting gestures according to claim 15, characterized in that the reproducing sub-module comprises a tag placement function in the pre-recorded signal file to be reproduced at the times when are expected control strokes of the rhythm of scrolling the file, said tags being generated automatically according to the rhythm of the prerecorded signals and can be moved by a MIDI interface.

19. Apparatus for interpreting gestures according to claim 15, characterized in that the value chosen in the temporal control sub-module for adjusting the scrolling speed of the reproduction sub-module is equal to a value chosen from a set of calculated values of which one of the bounds is calculated by applying a CSF speed factor equal to the ratio of the time interval between the next tag and the previous tag decreased by the time interval between the current tap and the previous tap at the time interval between the current typing and the previous typing and whose other values are calculated by linear interpolation between the current value and the value corresponding to that of the terminal used for the application of the CSF speed factor.

20. A gesture interpretation device according to claim 19, characterized in that the value chosen in the temporal control sub-module for adjusting the scroll speed of the sub-module. Reproduction module is equal to the value corresponding to that of the terminal used for the application of the CSF speed factor.

21. A method of interpreting significant gestures of a user comprising at least one measurement input step from at least one motion capture set according to at least a first and a second axis, a sampled signal processing step at the output of the input step and an output step adapted to reproduce the musical meaning of said gestures, the signal processing step comprising a sub-step of analysis and gesture interpretation comprising at least one step of filtering, a significant gesture detection function by comparing the variation between two successive values in the sample of at least one of the signals coming from at least the first axis of the set of sensors with at least a first threshold value chosen and a significant gesture detection confirmation function, said method being characterized in that said significant gesture detection confirmation function atif is able to compare at least one of the signals coming from at least the second axis of the set of sensors with at least a second threshold value chosen.

22. A method of interpreting gestures according to claim 21, characterized in that the output step comprises a sub-step of reproducing a pre-recorded file of signals to be reproduced and in that the processing step comprises a sub-step of time control step of said prerecorded signals, said substep reproduction being able to determine the times when are expected control strokes of the file scroll rate, and said substep time control being able to calculate for a certain number of control strokes a corrected speed factor (CSF) of preprogrammed strikes in the reproduction substep and strokes actually entered during the time control substep and a relative velocity intensity factor of said strikes actually inputted and expected then to adjust the scrolling rate of said prerecorded file to adjust said life factor corrected esse (CSF) to the following strikes at a chosen value and the intensity of the output signals of the reproduction step as a function of said relative velocity intensity factor.