WO2008129443A2

WO2008129443A2 - Audio playing system and method

Info

Publication number: WO2008129443A2
Application number: PCT/IB2008/051406
Authority: WO
Inventors: Arjan Claassen; Frank Wartena
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-04-20
Filing date: 2008-04-14
Publication date: 2008-10-30
Also published as: WO2008129443A3

Abstract

Audio playing system (1), comprising: a tempo provider (3) to provide a tempo parameter, wherein during operation the tempo parameter provides an indication to a desired audio tempo of audio to be played; -an audio signal provider (12) to provide a plurality of audio signals having different principle audio tempos; a controller (5) configured to provide an audio tempo sub-range that includes the desired audio tempo as well as principle audio tempos of a sub-group of the audio signals, provided by the audio signal provider, wherein the controller (5) is configured to select at least one of the audio signals from the sub-group, to be played; and - an audio player (7) configured to play the selected audio signal, preferably at the desired audio tempo as indicated by the tempo parameter.

Description

Audio playing system and method

FIELD OF THE INVENTION

The invention relates to an audio playing system and an audio playing method.

BACKGROUND OF THE INVENTION WO2005/082472 describes an audio pacing device comprising a sensing unit to obtain a parameter of a user in physical exercise, a memory to store a plurality of audio signals having predetermined tempo values, and a processing unit configured to determine whether intensity of the parameter of the user should be increased, decreased or maintained by using the parameter of the user from the sensing unit and a predetermined reference value, and select an audio signal having a tempo that enables the user to increase, decrease or maintain the intensity.

For example, this device can be used to coach individual exercisers with a personalized training program. A song collection can be tagged with labels identifying the tempo in 'beats per minute' (BPM) of the music. The tempo of the music can be used for matching (alignment, in phase) the music to the pace of the runner.

According to WO2005/082472, if the user's exercise intensity is insufficient for his heart rate to attain a target rate, the tempo of the audio signal is increased. This can be accomplished by increasing the playing tempo of a current audio signal. However, increasing the playing tempo of the current signal with more than a fixed percentage (about 10%) from the natural (i.e. principle) tempo will not go unnoticed by the user, and may be annoying to the user. Therefore, the pacing device will first try to pace the user by speeding up the tempo of the current audio signal. If the tempo is 110% and the user's heart rate is still below target, the device will select another audio signal having a higher principle BPM value than that of the current signal. A disadvantage of the known device is that the devices is not very flexible in the selection of audio signals. Thus, a user will hear the same audio signal a relatively large number of times during a training period when he is exercising at a certain tempo.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved audio playing system. Particularly, an object is to provide a more flexible audio playing system that can prevent that a user hears the same audio signal often.

According to the invention, this is achieved by an audio playing system, comprising: - a tempo provider to provide a tempo parameter, wherein during operation the tempo parameter provides an indication to a desired audio tempo of audio to be played; an audio signal provider to provide a plurality of audio signals having different principle audio tempos; a controller configured to provide an audio tempo sub-range that includes the desired audio tempo as well as principle audio tempos of a sub-group of the audio signals, provided by the audio signal provider, wherein the controller is configured to select at least one of the audio signals from the sub-group, to be played; and an audio player configured to play the selected audio signal, preferably at the desired audio tempo as indicated by the tempo parameter. In this way, there is provided a very flexible audio playing system that can prevent that a user hears the same audio signal often. For example, the audio playing system can be a coaching system or a pacing device, to coach or pace a user of the device.

Also, the invention provides an audio playing method, comprising: providing a tempo parameter, which provides an indication to a desired audio tempo of audio to be played; providing a plurality of audio signals having predetermined principal audio tempos; providing an audio tempo sub-range that includes the desired audio tempo as well as principle audio tempos of a sub-group of the audio signals, wherein at least one of the audio signals from the sub-group is being selected, to be played; and playing each selected audio signal, preferably at the desired audio tempo.

Also, there is provided a set of machine executable instructions, for example software, configured to carry out a method according to the invention in the case that the instructions are being executed by a machine, for example controller, computer or processor. For example, the set of machine executable instructions can be embedded in the audio playing system, to be executed thereby. Also, for example, the set of machine executable instructions can be loaded into an audio pacing device to provide a system according to the invention (particularly, to add functionality to the device such that the device can subsequently operate as a system according to the invention). In a further embodiment, such set of machine executable instructions can be provided to a user of the system via a suitable information carrier, for example storage medium, memory means or disk, or be provided in a suitable data format via a communication network, for example a Wide Area Network, for example Internet. A basic idea of the invention is the use (selection) of one or more sub-groups of audio signals, from the plurality (i.e. a main group) of audio signals. For example, a subgroup can at least be selected or defined each time a new audio signal is to be played, i.e., before the playing of a current audio signal has ended. In this way, a high degree of variation of the playing of audio signals can be obtained, so that a repeatedly playing the same audio signal can be prevented. Also, the present invention can provide an adapting of the music to a pace of the user, without increasing the chance for annoying audio artefacts. For example, according to an embodiment, the user can be prevented from hearing audio artefacts during training, by the selection of other music songs when artefacts start to appear. Moreover, embodiments can minimize the number of song changes during the training by using smart selection methods for song selection, for example using the current pace of a runner as a main selection parameter.

Further advantageous embodiments of the invention are described in the dependent claims. These and other aspects of the invention will be apparent from and elucidated with reference to non-limiting embodiments described hereafter, shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically shows an embodiment of a system according to the invention; Fig. 2 schematically depicts a graph of a number of audio signals per audio tempo value, relating to a plurality of audio signals, and indicates a selection of an audio signal;

Fig. 3 is a flow chart of an embodiment of a method according to the invention; Fig. 4 is similar to Fig. 2 and indicates an audio signal selection of part of a method according to the invention;

Fig. 5 is similar to Fig. 4 and indicates an alternative audio signal selection of part of a method according to the invention; and Fig. 6 is similar to Fig. 4 and indicates another alternative audio signal selection of part of a method according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Similar or corresponding features are denoted by similar or corresponding reference signs in the present patent application.

Figure 1 schematically depicts a non- limiting embodiment of a music playing system 1. The system includes: a tempo provider 3 to provide a tempo parameter, wherein during operation, the tempo parameter can provide an indication to a desired audio tempo of audio to be played; an audio signal provider 12 to provide a plurality of audio signals (for example a main collection of signals) having different principle audio tempos; a controller 5 that can be configured to cooperate with the tempo provider, to select at least one of the audio signals, to be played; and an audio player 7 configured to play the selected audio signal.

In the present embodiment, the system can be a coaching device, particularly a pacing device 1. For example, the device 1 can be configured to provide user coaching information in the form of music (i.e. audio signals), to a respective user (not shown) of the device 1. The device 1 can be configured in various ways, as will be appreciated by the skilled person. For example, the device 1 can be substantially similar to the device described in WO2005/082472, or be different there-from. Preferably, the device 1 is portable by a respective user during operation. For example, the pacing device 1 can be adapted to be worn or carried by the user, for example by a neck, arm, wrist or other body part of a user, it can be integrated with clothing worn by the user, and/or can be adapted to be contained in/by clothing or other means that are carried by the user. According to an embodiment, the pacing device 1 can include a dedicated pacing device, being primarily configured to coach the respective user. In another embodiment, the pacing device 1 can have various functions, next to the coaching of the user. The device 1 can be, or be provided by, for example, a PDA (personal digital assistant), cellular phone, watch, position tracking device (for example GPS, i.e. Global Positioning System, device), a user condition monitoring device, and a combination of such and/or other devices.

The device 1 can comprise the afore-mentioned controller 5 that can be configured to control operation of the device 1 and for example to carry out device functionality. For example, the controller 5 can be configured to control the playing of the music signals.

In an embodiment, the mentioned controller 5 and audio signal provider 12 can be separate parts, or be integrated with each other. Also, the audio player 7 of the device 1 can be integrated in the controller 5, or be a separate unit. The controller 5, audio signal provider and/or other device components can be provided by suitable hardware, software, microelectronics, and/or other means. The controller 5 can be provided by a suitable processor, computer or computing unit, or differently.

The present device 1 can include a single housing H having all of the components 3, 5, 7, 12 of the device 1, however, the device 1 can also include an assembly of a number of different/separate housings that include the components.

According to a preferred embodiment, the pacing device 1 can be configured to detect an, particularly instantaneous, training performance of the user of the device. For example, the training performance can include at least one of: a user position, user speed, user pace, user speed gradient, user physical state, user posture, user muscle power, and user heart rate (pulse rate).

The pacing device 1 can include a sensor 13 to detect or measure a training performance of a user of the device. For example, the pacing device 1 can be provided by a user physical state sensor 13, particularly a heart rate sensor 13 or a muscle power sensor. Also, the sensor can include: a user position sensor, user speed or pace sensor, user speed gradient sensor, user posture sensor, or a combination of the mentioned sensors and/or other sensors suitable to detect a certain training performance. For example, the device 1 can include a user position tracker (for example GPS device) that can provide data to be used to determine instantaneous user position, user speed and/or the speed gradient. A user posture sensor can be configured to detect a posture of at least one body part of the user, for example a leg, arm, head, body, and/or to detect a certain variation of that posture.

In a further embodiment, the sensor can be part of the controller 5, or be connected to the controller 5, wherein the controller 5 can be configured to calculate, estimate or determine an instantaneous training performance based on sensor output data. During operation, the sensor 13 can be positioned onto the body of the user (i.e. be in physical contact with the user) to detect the training performance, for example to detect a user heart rate and/or muscle power.

The device can include a user interface 15, for example, one or more user operable units, at least one key, switch or knob, a touchpad, touch screen, display, voice operated user interface, keyboard, and/or other user interface. The user interface 15 can be configured to be operated by the user, to enter user commands into the device 1 (for example, to activate the device, change a mode of device operation, and deactivate the device 1). Also, the user interface 15 can be designed to provide information to the user, for example audio and/or visual information. In an embodiment, the user interface 15 can include or be connected to an audio output unit 16.

For example, in the case that the pacing device 1 is an assembly of separate parts of units (for example, in the case of a central controller unit 5 being associated with a remote audio playing unit and/or remote user interface), the various parts of the device 1 can include suitable respective communication means to communicate with each other.

The tempo provider 3 can be part of the controller 5, as in the present embodiment, or it can be separate there-from. According to an embodiment, the tempo provider 3 can cooperate with the sensor 13, or be provided with the sensor 13, to associate the tempo parameter with a detected (training) performance of a user of the device. According to an example, the tempo provider 3 can be configured to provide a tempo parameter, such that the user can be coached, using the audio signals, to follow a predetermined training performance, for example to achieve a predetermined speed or speed profile, or to achieve and maintain a predetermined physical state such as a target heartbeat or heartbeat range. According to an example, the tempo provider 3 can be configured to adjust the tempo parameter depending on a sensor output of the sensor 13. Preferably, the sensor 13 (or sensing unit) obtains a parameter of the user in physical exercise during operation, wherein the tempo provider 3 is configured to determine whether intensity of the tempo parameter should be increased, decreased or maintained by using the parameter of the user (i.e. sensor output) from the sensor 13 (for example depending on a predetermined or desired training program, for example a target value or target range of the parameter of the user).

The tempo parameter that is provided by the tempo provider 3 can indicate a desired pacing tempo, for example in the form of a BPM value, or can simply be a logical parameter, such as a 0 (zero) in case a current user tempo is to be maintained, -1 in case the a user tempo is to be decreased, and +1 in case a user tempo is to be increased, of in a different manner.

Besides, alternatively, the tempo provider can simply be configured to copy a detected current user tempo to the tempo parameter, for example in the case that the tempo parameter is not particularly used to train the user. The device 1 can be provided with a memory 12 to store information, for example to store the plurality of music signals (for example songs) and/or other information. Preferably, the memory is or comprises the aforementioned audio signal provider 12, as in the present embodiment. The audio player part 7 of the device 1 can include or be connectable to one or more suitable audio output units 16, such that the music signals are perceived by the user. A coaching audio output unit 16 can comprise, for example, speakers, an in-ear or behind-the- ear speaker or headphone, to play audio pacing signals to be heard by the user.

For example, the device 1 can be configured to provide pacing information in the form of a music rhythm of music that is played by the player 7, for example a beats-per- minute (BPM) signal to indicate a desired user pacing rate or movement rate, for example a user step rate, that is to be followed by the respective user. Also, preferably, the pacing device 1 contains personalized music signals to be played to provide personal coaching information, for example music signals in one or more suitable format, for example a music compression format, MP3, WAV, AAC, MPEG4, and/or other formats.

In an embodiment, the audio signal provider 12 contains the aforementioned different audio signals in combination with information of their natural, i.e. initial or principle, audio tempo. For example, this information can be a BPM (beats per minute) label, value or tag, which is stored in the audio signal provider 12 in conjunction with each respective audio signal. As an example, the audio signal can be stored in a data file, which data file also contains such principle tempo tag. Also, for example, the audio signal provider 12 can contain the different audio signals in a predetermined, sorted order, such that the signals are being sorted with respect to each other based on their principle tempo, for example from a signal with a lowest principle tempo to a signal having a highest principle tempo. Also, the audio signal provider 12 can contain a list or inventory relating to the plurality of audio signals, the list or inventory containing the principle (natural) tempo information of each of the audio signals. In an embodiment, the principle (natural) audio tempo of an audio signal is the tempo of the signal at the signal was originally recorded, for example during a music recording process, as will be appreciated by the skilled person. A graph of a-non limiting example of the plurality of audio signals is schematically shown in Figure 2. The graph shows the number of audio signals N(tempo) per principle audio tempo, of a plurality of signals stored in the memory/signal provider 12 of the device 1. In the present example, the plurality of audio signals has principle tempos in a range between 90 and 130 BPM. In Figure 2, a total of seventeen audio signals is available at various tempos, wherein two signals have the same tempo (at 125 BPM), as an example.

In a prior art pacing method and device, during operation, a tempo provider can provide a tempo to indicate a desired audio tempo of audio to be played. In Figure 2, an arrow Ti schematically indicates a tempo (110 BPM in the present case) that is being provided by the tempo provider. For example, this tempo can be a desired running pace, and/or it can be a current pace of a runner.

A prior art pacing device is configured to select a music signal, from the plurality of audio signals, having a principle tempo (the song at 108 BPM in the present case) being closest to the indicated tempo Ti, as is indicated by an arrow S in Figure 2. This audio signal can than be easily adapted to match the runner's pace, without any recognizable audio artefacts. Such a music selection algorithm only looks at the principle tempo (BPM) of a song to see which song is the best candidate to play next. This means that when the user has at a constant pace, the same song will always have the best matching tempo (assuming every song has a different principle tempo). This will cause a very bad/boring user experience.

For example, when a runner is running an almost constant tempo, the runner will hear only a very small part of the complete collection, since there are maximum two tempo values closest to the current pace (the exact value, or the upper and lower closest value). When there is only one song with this exact tempo, this song will be selected each time, and played during the complete training session, which will lead to annoyance with the runner.

According to a preferred embodiment of the invention, the system 1 (particularly the controller 5) can be configured to provide an audio tempo sub-range that includes the desired audio tempo as well as principle audio tempos of a sub-group (i.e. sub- collection) of the audio signals, provided by the audio signal provider, wherein the controller 5 is configured to select at least one of the audio signals from the sub-group, to be played.

According to non-limiting embodiments, a mentioned audio tempo sub-range can be a range of 40 beats per minute, particularly 30 beats per minute, more particularly 20 beats per minute. Also, for example, a mentioned audio tempo sub-range can be a range between plus and minus a predetermined percentage, for example 20%, of the desired audio tempo, for example a range between plus and minus 15% of the desired audio tempo, preferably a range between plus and minus 10% of the desired audio tempo. Preferably, the tempo sub-range can provide a 'bandwidth' in which the playing tempo can be adapted without leading to audio artefacts. For example, the controller 5 can be configured to select the sub-group of audio signals such that the desired audio tempo, that is being indicated by the tempo parameter 3, is located near or in about the middle of the respective tempo range of the subgroup. Also, the controller 5 can be configured to apply a probability function (see

Figures 4-6) to select an audio signal to be played, for example such that a signal having a principle tempo close to a range limit of the sub-range has a lower probability to be selected than a signal having a principle (basis) tempo located farter away from the range limit, such as near a centre of the sub-range. According to an embodiment (see above), the tempo provider 3 is configured to adjust the tempo parameter based on one or more input parameters, for example a detected user heart rate and/or user speed or pace, wherein the audio player 7 is configured to adjust the audio tempo of the audio signal based on the adjusted tempo parameter. Preferably, the controller 5 is configured to detect when a desired adjusted audio tempo of audio to be played, as indicated by an adjusted tempo parameter, reaches a limit of a current audio tempo sub-range, wherein the controller 5 is configured to provide a new audio tempo sub-range in the case that the adjusted desired audio tempo has reached or approaches the limit of the respective sub-range, and to select at least one of the audio signals from the new audio tempo sub-group, to be played. Preferably, the controller 5 is configured to subsequently select different audio signals from the sub-group, to be played, for example such that the player 7 does not repeat playback of an audio signal after having just played that signal.

Figure 3 is of flow chart of an embodiment of operation of a system, for example the pacing device 1 , according to the invention. During operation, the system can carry out a method that includes: a step 100 of providing a plurality of audio signals (i.e. a main group of signals) having predetermined principal audio tempos, for example by the memory 12; a step 101 of (for example the tempo provider 3) providing a tempo parameter, which provides an indication to a desired audio tempo of audio to be played; - a step 102 of (for example the controller 5) providing an audio tempo subrange that includes the desired audio tempo as well as principle audio tempos of a sub-group of the audio signals; a step 103 of selecting at least one of the audio signals from the sub-group is being selected, to be played; and a step 104 of playing each selected audio signal at the desired audio tempo, by the audio player unit 7.

For example, in Figure 3 arrows kl and k2 indicate interrelations between steps 100 and 102, and steps 101 and 102 respectively, for example transmission of data from a memory and tempo parameter provider to a controller carrying out the step 102, the data relating to the available plurality of audio signals and the desired tempo parameter. Arrow k3 schematically indicates transmission of the desired tempo parameter to audio playing step 104. Dashed line k4 can indicate transmission of the selected audio signal (for example from a memory) to the audio player 7. In an embodiment, the playing of the selected signal continues, and a new signal can be selected to be played from a presently determined sub-group when the playing of a present signal has been finished. For example, this can be carried out in case the tempo parameter has not been substantially changed.

In another embodiment, the playing of the selected signal continues, and a new sub-group can be selected first, when the playing of a present signal has been finished, wherein a new signal will be selected from the newly selected sub-group to be played. This is indicated in Figure 3 by arrow k6.

In a preferred embodiment, the tempo provider can adjust the tempo parameter based on one or more input parameters (see above). Thus, a present tempo parameter can change during operation, and can lead to an adjusted desired audio playing tempo. In that case, preferably, a step 105 is provided, for example during the playing of an audio signal, the step 105 including a determination whether or not a presently (for example adjusted) desired audio tempo of audio to be played, as indicated by an adjusted tempo parameter, reaches a limit of a current audio tempo sub-range, wherein a new audio tempo sub-range is automatically determined in the case that the adjusted desired audio tempo has reached or approaches the limit of the respective sub-range. Subsequently, at least one of the audio signals will be selected from the new audio tempo sub-group, to be played at the desired, adjusted audio playing tempo. Also, this step 105 can be carried out by the mentioned controller 5. In Figure 3, a dashed arrow k5 can indicate transmission of the (adjusted) present tempo parameter, or a respective desired audio playing tempo, to the controller, to be used in the step 105.

Preferably, the above-steps are carried out real time, for example during the coaching or pacing of a user of the device 1. For example, each audio tempo sub-range can be selected substantially continuously, iteratively or periodically during operation. On the other hand, such selection can be triggered by certain specific conditions or changes, for example be triggered by a certain change of the tempo parameter (see above). In the latter case, the tempo provider 3 can trigger the controller 5 to start selecting a new sub-group.

Also, the present method can include: selecting the sub-group of audio signals such that the desired audio tempo that is being indicated by the tempo parameter, is located near or in about the middle of the respective tempo range of the sub-group. Preferably, each sub-group only contains part of the plurality of audio signals, wherein only audio signals from a current sub-group are being selected to be played. Also, preferably, each sub-group as such contains more than one audio signal, for example about 5 signals or more, from the plurality of audio signals. Preferably, each audio sub-group contains at least two different audio signals. Also, preferably, each audio sub-group contains at least two audio signals having different principal audio tempos.

In the above embodiments, the tempo parameter provides an indication to a single desired audio tempo. However, according to an advantageous embodiment, the tempo parameter can provide an indication to at least a first desired audio tempo tl and a second desired audio tempo t2 of audio to be played, wherein the first and second desired audio tempo are interrelated. For example, a ratio tl :t2 between the first and second audio tempos can be an integer, for example selected from the set of integers {2, 3, 4} and/or different integers. For example in case the first desired audio playing tempo is 60 BPM, the second tempo can be 120 or 180 BPM. In this way, a presently selected sub-group can contain a relatively large number of audio signals, to be chosen from. For example, tl :t2 = 2, 3, 4 , et cetera, or alternatively, t2:tl = 2, 3, 4, et cetera.

Besides, according to an embodiment, a music signal can be selected randomly from a defined sub-range. In that case, each music signal in a sub-collection will have an equal chance of being selected, the chance being 1 divided by the number of songs in the sub- collection. For example, in such an embodiment, music signals with a tempo far from a current desired pace of a runner will have equal chance of being selected as songs close to the current pace tempo.

To minimize the chance on additional audio artefacts and additional song changes in the future, a normally distributed selection chance can be applied, for example such that that music signals with a tempo close to a current desired runner's pace or close to an expected or desired future runners pace have a relatively high probability of being selected (i.e., higher than a selection probability for music signals with a tempo further away from a current desired runner's pace or close to an expected or desired future runners pace). For example, a suitable probability function can be used to select a mentioned audio signal sub-group. Examples are shown in Figures 4-6. In each of Figures 4-6, a respective probability function Pl(tempo), P2(tempo), P3(tempo) defines a probability that a certain music tempo can be selected. In each case, for example, the respective selection chance provided by the probability function can be in the range from 0 to 1. Preferably, the probability function is normalized, such that the sum of the respective probabilities to select respective music signals is 1 (so that the chance that a music signal will be selected during a selection step is always 100%).

Figure 4 shows an embodiment, wherein the controller applies a relatively simple, linear probability function Pl (shown by a dashed triangle) to select an audio signal to be played. Arrows Ll and L2 show respectively a lower and upper sub-group range limit, and arrow Ti indicates a desired audio playing tempo. In this embodiment, the probability function Pl (tempo) is triangular, such that a signal having a principle tempo close to each range limit Ll, L2 of the sub-range has a lower probability to be selected (for example 0) than a signal having a basis tempo located farter away from the range limit, such as near a centre Ti of the sub-range (which lies at about 110 BMP in Figure 5). In the present embodiment, the probability P_max that a signal having a basis tempo located near the centre of the sub-range is highest, wherein probabilities linearly decrease from that high value to 0 at the lower and upper range limits Ll, L2. Figure 5 is similar to Figure 4, and shows an embodiment wherein the selection function P2(tempo) has shifted towards a higher tempo range. This can be the case, for example, when the tempo parameter is increasing, is expected to increase or has increased, leading to an increase of the desired audio playing tempo Ti. For example, a user can be speeding up, such that a future desired audio playing tempo Ti will be higher than a current audio playing tempo Tc (see Figure 5). The shifting of the selection function P2(tempo) can be such that a current audio playing tempo Tc becomes a relatively low probability of being selected in a future music signal selection step, for example such that the current audio playing tempo Tc lies at or near a lower range limit of a newly determined audio signal sub-group. Also, the shifting of the selection function P2(tempo) can be such that the expected future desired audio playing tempo Ti becomes a relatively high probability of being selected in a future music signal selection step, for example such that the future desired audio playing tempo Ti lies at or near a centre of a newly determined audio signal sub-group. In this way, the process can take into account expected changes of the desired audio playing tempo, so that chances of audio artefacts can be reduced. Figure 6 is similar to Figure 4 and indicates another alternative audio signal selection of part of a method according to the invention. In this embodiment, the probability function is a Gaussian probability distribution (normal distribution) P3(tempo). Also, in this case, a signal having a principle tempo close to a range limit of the sub-range has a lower probability to be selected than a signal having a basis tempo located farter away from the range limit, such as near a centre of the sub-range. The peak of the present Gaussian distribution P3(tempo) preferably lies at or near the centre of the sub-rage (i.e. 110 BPM in Figure 6), for example at a desired audio playing tempo Ti (which can be a currently desired audio playing tempo or a future, expected, desired audio playing tempo). The application of probabilities, such as shown in Figures 4-6, for the selection of audio signals leads to a high degree of variation of the selection and playing of the music signals. Besides, according to an embodiment, the audio playing system can be configured to make use of several of such probability functions in case of the use of a single sub-group, and to switch between those functions depending on one or more parameters. For example, a function can be selected that provides a highest probability near a centre of a selected tempo sub-range, in the case that a training performance of the user, for example a current speed or pace, is substantially constant. In the case that a training performance is to be changed, for example increased, a different probability function can be used, that provides a higher probability near a range limit Ll, L2 of a currently selected sub-group. Also, in that case, the system can already take into account future changes of the sub-range, so that chances of playback artefacts can be reduced to a minimum.

The above embodiments can provide several advantages. For example, audio artefacts can appear when music is adapted beyond a certain threshold percentage (e.g. 20%) from the original tempo value (measured in beats per minute). The moment that the pacing device 1 needs to adapt the music more than the said threshold percentage, preferably, another song will be selected. Preferably, the present selection method ignores a music signal that is currently playing when a new music signal is to be selected. Also, preferably, the same music signal is never being played twice during a certain training period.

Embodiments of the present invention propose to introduce a sub-range in which a music signal (song) can be selected. The width of the sub-range can be configured with a maximum threshold percentage (for example plus and minus 10%) for hearing audio artefacts, as is described above. All songs in a selected sub-range (sub-collection) can be adapted to match the current running pace, since their tempo differs less than the said maximum threshold percentage. According to an example, the controller 5 can also be configured to select an audio signal having a higher principle audio tempo than a currently desired audio playing tempo in case the controller determines or estimates that the tempo parameter increases or will increase, wherein the controller can be configured to select an audio signal having a lower principle audio tempo than a currently desired audio playing tempo in case the controller determines or estimates that the tempo parameter decreases or will decrease.

For example, the number of song changes can be minimized by using the full bandwidth (i.e. the tempo range of an audio signal sub-group), when a user is being coached to follow a constant tempo. Also, according to an embodiment, only one half of the full bandwidth that can be used for adapting the tempo of the song can be taken into account. For example, if the user of the pacing device 1 is speeding up, a song can be selected based on one of the previous methods, wherein only an upper half of the bandwidth (e.g. relative tempo 100% till 110% of original tempo) is used for determining the sub-group. For example, to this aim, the derivative of a current user pace can be taken into account, to predict whether the user is speeding up or slowing down (i.e increasing or decreasing pace). This information can be used in the selection algorithm to shift the bandwidth (e.g. upwards, see Figure 5).

For example, if a runner has a constantly increasing pace (leading to an increasing tempo parameter), preferably, preferably no music signal will be selected that is subsequently to be played above its natural tempo (due to an increase of the tempo parameter), because with the constant increase of pace this will probably lead to a new song change in the near future. In that case, preferably, a song is selected that must be played below its natural tempo, for example at a relative speed/tempo close to 100% minus a maximum threshold percentage (such as 10%). In this case, a music signal can be started playing below its natural tempo, for example at 90% of its natural tempo, and can increase its tempo to 110% of the natural tempo. This means in an optimal case, that the number of song changes due to a too large stretching factor, can be reduced by a factor 2. This will significantly improve the user experience of the coaching method.

Also, when the pacing device 1 chances to a next song, the audio player can use existing "beat matching" algorithms, and fade in/out effects to create a smooth transition between the songs. For example, a beat mixing can be used by the device 1, to align the beats of subsequent songs during the changing of the songs. Using these algorithms and effects the user can continue running on a single, continuous beat. Besides, the pacing device 1 can be configured to signal that various session parts of a training programme (e.g. warm-up, main training, interval, cooldown, end of training) start or end. The signaling can be simple beep signals, or spoken messages or other signals. Also, according to an embodiment, the device 1 can be configured to select songs in such a way that the end of a song (and the beginning of the next song) is (almost) aligned with session part transitions. If a song would be just a few second short the user will hear a flash of a song, before hearing the beep. For a correct selection the remainder of the session part can be used to select a song with approximately the same length, or some slightly more. Following from the above, there can be provided a collection of music that is labeled with the tempo of each song. The pacing device can comprise a collection manager (for example the controller 5) that uses these values for the selection of the songs. The collection manager can be responsible for selecting the next song, using one, or a combination of more algorithms as described before. The audio player of the device will play the songs, and can be instructed to play the song on a tempo of a current pace of a runner, if the music must follow the runner, or in a tempo slightly differing from the current pace of the runner, if the device is coaching the runner by setting the new tempo. The audio player 7 can receive a relative speed (= required tempo divided by original music tempo) from the controller, if desired.

The device 1 can also take a playlist history into account, for example: how long ago a certain song was played. For example, the song selection can be based on both the natural tempo of the song and on when the song was last played by the device.

Besides music signals, other multi media formats can be used and played by the device 1, if desired, such as: images, movies, music video clips, flavours/smells/scents, 3D generated environment, and/or fractal images. For example, apart from coaching a runner by playing music at a certain bpm, the user can also be coached by visual stimulations. Options are playing a movieclip (with music) at a certain bpm; thus adjust the audio and the video. Another option is a music "visualiser" (like in winamp) that creates visual representations with a certain bpm; for instance a flashing led or something more interesting. The invention can be applied to use individual coaching devices 1, both indoors and outdoors. The audio playing system can also be fitness equipment, for example spinning bikes, cardio training devices or a other audio playing device.

Although the illustrative embodiments of the present invention have been described in greater detail with reference to the accompanying drawings, it will be understood that the invention is not limited to those embodiments. Various changes or modifications may be effected by one skilled in the art without departing from the scope or the spirit of the invention as defined in the claims.

It is to be understood that in the present application, the term "comprising" does not exclude other elements or steps. Also, each of the terms "a" and "an" does not exclude a plurality. Also, a single processor or other unit may fulfill functions of several means recited in the claims. Any reference sign(s) in the claims shall not be construed as limiting the scope of the claims.

Besides, there can be provided an audio playing system comprising: - a tempo provider 3 to provide a tempo parameter, wherein during operation the tempo parameter provides an indication to a desired audio tempo of audio to be played; an audio signal provider 12 to provide a plurality of audio signals having different principle audio tempos; a controller 5 configured to select at least one of the audio signals to be played, and configured to detect or estimate a change of the tempo parameter; and an audio player 7 configured to play the selected audio signal, preferably at the desired audio tempo as indicated by the tempo parameter, wherein the controller is configured to select an audio signal having a higher principle audio tempo than a currently desired audio playing tempo in case the controller determines or estimates that the tempo parameter increases or will increase, wherein the controller is configured to select an audio signal having a lower principle audio tempo than a currently desired audio playing tempo in case the controller determines or estimates that the tempo parameter decreases or will decrease.

This audio playing system can be part of above-described embodiments, making use of sub-groups of music signals, however, this is not essential. Herein, preferably, the controller can be configured, in case the controller determines or estimates that the tempo parameter does/will change, to select a new audio signal having a principle tempo close to or at plus or minus 10% from a current audio playing tempo. After the selection of such a new audio signal, the signal will first be played at a tempo that is different from its natural/principle tempo. Due to the change of the tempo parameter (as determined or expected by the controller), the playing tempo of the signal will change towards its principle tempo. In this way, the controller can take into account changes of the tempo parameter, for example due to changes of the pace or speed of a runner, so that audio artefacts can be reduced.

Claims

CLAIMS:

1. Audio playing system (1), comprising: a tempo provider (3) to provide a tempo parameter, wherein during operation the tempo parameter provides an indication to a desired audio tempo of audio to be played; an audio signal provider (12) to provide a plurality of audio signals having different principle audio tempos; a controller (5) configured to provide an audio tempo sub-range that includes the desired audio tempo as well as principle audio tempos of a sub-group of the audio signals, provided by the audio signal provider, wherein the controller (5) is configured to select at least one of the audio signals from the sub-group, to be played; and - an audio player (7) configured to play the selected audio signal, preferably at the desired audio tempo as indicated by the tempo parameter.

2. System according to claim 1, wherein the controller (5) is configured to select the sub-group of audio signals such that the desired audio tempo, that is being indicated by the tempo parameter, is located near or in about the middle of the respective tempo range of the sub-group.

3. System according to any of the preceding claims, wherein the controller (5) is configured to apply a probability function to select an audio signal to be played, for example such that a signal having a principle tempo close to a range limit of the sub-range has a lower probability to be selected than a signal having a principle tempo located farter away from the range limit, such as near a centre of the sub-range.

4. System according to any of the preceding claims, wherein the tempo provider (3) is configured to adjust the tempo parameter based on one or more input parameters, for example a detected user heart rate, user pace and/or user speed, wherein the audio player (7) is configured to adjust the audio tempo of the audio signal based on the adjusted tempo parameter.

5. System according to claim 4, wherein the controller (5) is configured to detect when a desired adjusted audio tempo of audio to be played, as indicated by an adjusted tempo parameter, reaches a limit of a current audio tempo sub-range, wherein the controller is configured to provide a new audio tempo sub-range in the case that the adjusted desired audio tempo has reached or approaches the limit of the respective sub-range, and to select at least one of the audio signals from the new audio tempo sub-group, to be played.

6. System according to any of the preceding claims, wherein the audio tempo sub-range is at least one of: - a range of 40 beats per minute, particularly 30 beats per minute, more particularly 20 beats per minute; and a range between plus and minus a predetermined percentage, for example 20%, of the desired audio tempo, for example a range between plus and minus 15% of the desired audio tempo, preferably a range between plus and minus 10% of the desired audio tempo.

7. System according to any of the preceding claims, wherein the controller (5) is configured to subsequently select different audio signals from the sub-group, to be played.

8. Audio playing method, comprising: providing a tempo parameter, which provides an indication to a desired audio tempo of audio to be played; providing a plurality of audio signals having predetermined principal audio tempos; - providing an audio tempo sub-range that includes the desired audio tempo as well as principle audio tempos of a sub-group of the audio signals, wherein at least one of the audio signals from the sub-group is being selected, to be played; and playing each selected audio signal, preferably at the desired audio tempo.

9. The method according to claim 8, including: selecting the sub-group of audio signals such that the desired audio tempo, that is being indicated by the tempo parameter, is located near or in about the middle of the respective tempo range of the sub-group.

10. The method according to claim 8 or 9, including: applying a probability function to select an audio signal to be played, for example such that a signal having a principle tempo close to a range limit of the sub-range has a lower probability to be selected than a signal having a principle tempo located farter away from the range limit, such as near a centre of the sub-range.

11. The method according to claim 10, wherein the probability function is a Gaussian probability function.

12. Method according to any of claims 8-11, wherein each sub-group only contains part of the plurality of audio signals, wherein only audio signals from a current subgroup are being selected to be played.

13. The method according to any of claims 8-12, comprising: adjusting the tempo parameter based on one or more input parameters, for example a detected user heart rate, user pace and/or user speed, and adjusting the audio tempo of the audio signal based on the adjusted tempo parameter.

14. The method according to any of claims 8-13, wherein each audio sub-group contains at least two different audio signals, preferably at least two audio signals having different principal audio tempos.

15. The method according to any of the claims 8-14, wherein the tempo parameter provides an indication to at least a first and a second desired audio tempo of audio to be played, wherein the first and second desired audio tempo are interrelated, for example such that a ratio tl :t2 between the first and second desired audio tempo is an integer.

16. A set of machine executable instructions, for example software, configured to carry out a method according to any of the claims 8-14 in the case that the instructions are being executed by a machine, for example controller, computer or processor.