Automatic volume control taking into account different audio signals

Abstract

Volume control device for controlling the volume of various audio signals (1), comprising: - a volume control for automatically adjusting the volume for a selected audio signal (1); and - a storage means (21) for storing volume control information (22, 27, 3) per audio signal, wherein the volume control information (22, 27, 3) - a state variable (22, 27) of a state of the volume control resulting from the automatic control process or - a volume control variable (3) automatically set by the volume control as part of the automatic control process, wherein - the volume control device is designed such that when an audio signal (1) is deselected, the current state variable (22, 27) or current volume control variable is stored in the storage means (21) as volume control information (3) for the previously selected audio signal (1), and - when an audio signal (1) is selected, the volume control information (22, 27, 3) stored in the storage means (21) for the audio signal (1) is used to control or adjust the volume of the audio signal (1).

Description

The invention relates to the setting, in particular automatic control, of the volume of various audio signals, for example various audio signals of various audio transmitters or television transmitters, or various audio signals of various audio sources, such as CD players and radio.Entertainment systems in motor vehicles, for example car radios with a CD playback function, frequently rely on different audio signals whose origin, quality and standard conformance are not known apriori. Thus, when the audio signals are changed, there are sometimes severe volume changes.Without using volume control, the user of such an entertainment system is forced to compensate for these volume changes by manual readjustment.The problem of volume variation may even be critical with regard to safety in motor vehicles if the volume of a soft audio signal has been corrected manually by the central volume controller. During the subsequent changeover to a loud audio signal, a large volume jump can then result, which can lead to a startling situation.To reduce volume changes, it is known to use dynamic compressors. These have the purpose of preventing overdrive. When dynamic compressors are used, however, the hearing food is disturbed markedly by pumping effects. Moreover, audio signals with high dynamics can be developed by dynamic compressors.Source-specific volume adjusters are also typically used in entertainment systems. As a result, a part of the fluctuations can be reduced by the rigid compensation of an average deviation. Source-specific volume adjusters can only compensate for the mean level deviation. Unknown systems cannot necessarily be taken into account. Often, a dynamic compressor must be used as a protective measure in order to prevent an overload.The publication DE 103 24 964 A1 discloses a car radio with stored volume setting for individual radio transmitters. The volume control variable manually set by the user when listening to a radio transmitter is stored in a memory. When the radio transmitter is selected again, the stored volume control variable is used to set the volume. The storable volume manipulated variable is a user-defined volume manipulated variable. If this is not available during the later read-out of the memory, a volume preset by the manufacturer can be used.Reference is also made to the publication DE 11 49 440 B and the publication DE 34 01 748 A1 as further prior art.It is an object of the invention to provide an improved apparatus and an improved method for volume adjustment for different audio signals, which reduces a volume jump when switching between two audio signals.The object is achieved by the features of the independent claims.A first aspect of the invention relates to a volume control device for controlling the volume of different audio signals, for example different audio signals of different audio transmitters or television transmitters. The apparatus comprises a volume control for automatically controlling the volume for the respectively selected audio signal. The apparatus further comprises storage means for storing volume control information for the individual audio signals. Such volume control information comprises at least one state variable of a state of the automatic volume control resulting within the framework of the automatic control process (from which the value of a volume control variable then results) or directly a volume control variable automatically set by the volume control within the framework of the automatic control process. In this case, it is also possible to store for the individual audio signals how long the audio signal has already been heard (this gives information, for example, as to whether the volume control has already settled).The volume control information is stored in the storage means in such a way that, when the previously selected audio signal is deselected, the current state variable or current volume control variable is stored in the storage means as volume control information for the previously selected audio signal. The stored volume control information can be used later for controlling or adjusting the volume of the selected audio signal. In this case, it may occur that, when the audio signal is deselected, the volume control is not yet steady.Preferably, when selecting an audio signal, the volume control information stored in the storage means for the respective audio signal is used-if present-for controlling or adjusting the volume of the selected audio signal. If the control process is volume control information of a control process which has not yet settled, the previous control process can be continued on the basis of the stored volume control information when the audio signal is selected again.It should be noted that control based on the stored volume control information can be performed with the same volume control or alternatively also in a different second volume control (which is assigned to a different receiver, for example).The selection and selection need not be related to the same volume control: for example, the selection may be related to a first volume control (for example, a control that feeds the storage means with loudness control information to be stored) and the selection may be related to another volume control (for example, a control that then later uses the stored volume control information). Selection and / or deselection are not necessarily initiated by the user; for example, the system can automatically initiate deselection when the volume control is operating in the background without the user actually listening to the audio signal.By storing volume control information according to the invention and by later recourse to previously stored volume control information, a volume jump during the switching of the audio signal is reduced or even completely suppressed.It is pointed out that for volume control, the selected audio signal does not actually have to be output via a loudspeaker and listened to by the user. Thus, it can be provided that the volume of the various audio signals is effected in the background.For example, a radio receiver can successively select individual transmitters in the background, wherein the volume is automatically controlled for each transmitter by means of the control and the volume control information is stored in a so-called history in each case. It can be provided that during this time the user can listen to a specific radio transmitter, for example via another radio receiver (if a second radio receiver is present), or listen to music via an entirely different source (e.g. CD).Preferably, each audio signal is assigned its own identifier, for example a transmitter identifier. The storage means is in this case configured to store the volume control information and the associated identifier per audio signal.According to an advantageous embodiment, a nonlinear controller is used in the automatic volume control. Preferably, a non-linear regulator is used which distinguishes between at least three input ranges for the input signal of the regulator, namely a first input range (adaptation range), a second input range (working range) lying above it and a third input range lying above the second input range (also referred to as a head room which avoids clipping).Each input area is assigned a controller state. Regulators of this type are also referred to as three-point regulators in three input ranges. The controller causes the volume to increase when the input signal of the controller is in the first input range. The controller causes a decrease in the volume when the input signal of the controller is in the third input range. On the other hand, the controller keeps the volume constant (i.e. the controller does not change the volume control value; the volume control value is frozen) if the input signal of the controller is in the second input range.The lower threshold value of the third input range is preferably -3 dB, i.e. the third input range comprises modulation values of the regulator input signal of approximately 70% to 100%. The second input region preferably begins from or above -13 dB.Preferably, the respective size of the three input ranges is time dependent. In this case, it can be provided that the size of the second input range increases with increasing time after the first selection of the respective audio signal and the size of the first and / or third input range decreases with increasing time after the first selection of the respective audio signal. This allows a very rapid transient response of the control process at the beginning of the control process. Just at the beginning after the first selection, the second region is preferably not present or consists only of a single point (e.g. of the setpoint value).The input signal of the controller is preferably determined via a peak detector. The measurement of the signal is preferably continuous, wherein the peak value is determined within a time interval. This value then corresponds to the control value which indicates the volume of the signal. The measurement can have interference suppression, for example by means of a dynamic compressor. Thus, in broadcast sources, there are frequently disturbances which are significantly louder than the actual music signals. This has the result that controllers are frequently caused to perform an undesired control on the interference signal. A dynamic compressor could be used for interference suppression if the error detection has not taken effect. On the other hand, even noises such as shots in a dark recording can lead to considerable disturbances in the controller behavior. By smoothing these disturbances by a dynamic compressor, these disturbances can be mitigated.According to an advantageous embodiment, the regulator uses a zero signal threshold (e.g. at -30 dB). For the very small input signal values of the controller less than or less than or equal to the zero signal threshold (referred to below as zero signal range), essentially no regulation takes place. The control value is frozen. By using a zero signal threshold, a regulation is avoided if no active audio signal is present, but only noise is present (which lies below the zero signal threshold). This is the case, for example, with a tuner source in the "no signal" state. No active audio signal is present even in the case of a pause audio source (e.g. CD in pause) or an audio source switched off because of interference signal.Each input region of the controller can be assigned a specific regulating speed (regulating weight). These are preferably different coefficients. These may also be zero (for example for the second input range or for values less than the zero signal threshold)Preferably, the control speed in the third input range (headroom) is greater in terms of amount than in the first input range (adaptation range). As a result, an overload is compensated very quickly; however, an excessively quiet signal is adapted gently in its volume without the signal being adulterated. For example, a control speed of -30 dB per second can be provided for the third input range (headroom), while the first control range has a control speed of 0.02 dB per second (or time-discrete 1 dB every 50 seconds), for example. In the zero signal range and in the second input range (working range), the controller is preferably passive; the control speed is then 0 dB per second.Instead of a non-linear volume control as described above, a linear volume control with a linear controller can also be used, for example with a PID controller.Alternatively, non-linear volume control and linear volume control can also be combined. For example, the nonlinear controller and a linear controller can be arranged parallel to one another for this purpose. The influence of the linear controller and / or nonlinear controller on the overall control can be defined by a weight factor. Alternatively, it can also be provided that in the nonlinear controller the control deviation in the non-passive regions (first and third regions) is weighted linearly, so that the controller also contains linear controller components.A second aspect of the invention is directed to an audio or audio / video playback apparatus for a motor vehicle, for example a car radio with radio, CD and optional television functions. The reproduction device is configured to reproduce different audio signals (for example, to reproduce different radio transmitters or to reproduce different audio sources). The reproduction apparatus comprises a volume control device as described above.It can be provided that the volume control is effected for a plurality of transmitters (e.g. radio transmitters) in the background without the user listening to the radio transmitters. For this purpose, the device selects the individual transmitters successively and adapts the volume in each case and stores the associated volume control information in each case. During a later reproduction of a transmitter, this stored information is then used to control the volume.Preferably, the playback device comprises at least two radio broadcast receivers, in particular two radio broadcast receivers or two radio broadcast receivers or one radio broadcast receiver and one radio broadcast receiver. A user-selected transmitter can be reproduced with the first radio receiver. By means of the second radio receiver, the volume of the transmitters can be adjusted in the background via the volume control device, wherein the respectively associated volume control information is stored.The stored loudness control information can be used later by a loudness control associated with the first radio receiver.A third aspect of the invention is directed to a method for controlling the volume of various audio signals. The features of the method correspond to the features of the aforementioned volume control device according to the first aspect of the invention. In this case, the volume for a selected audio signal is automatically regulated. When the audio signal selected up to now is selected, a current state variable of the state of the automatic volume control resulting from the automatic control process or the current volume manipulated variable automatically set by the volume control from the automatic control process is stored in a storage means as volume control information. When this audio signal is selected again, the volume control information stored in the selected audio signal storage means is used to control or adjust the volume of the selected audio signal.The above explanations regarding the volume control device according to the first aspect of the invention also apply in a corresponding manner to the method for controlling the volume according to the third aspect of the invention.The invention is described below with the aid of the appended drawings with reference to a plurality of exemplary embodiments. In these show: FIG. 1 shows an embodiment of the volume control device according to the invention for controlling the volume of various audio signals according to the first aspect of the invention; FIG. 2 shows an exemplary characteristic diagram of the nonlinear controller having four input ranges; FIG. 3 shows a volume setting device for setting the volume of at least two audio signals (not belonging to the invention); and FIG. 4 shows the exemplary time curves of the variables shown in Table 3 in graphical form (not belonging to the invention).The invention relates to the control of the volume of various audio signals. In this case, a non-linear controller with memory is preferably used. The aim of the regulation is to achieve the widest possible modulation range, the avoidance of clipping and the greatest possible non-influencing of the dynamics of the audio signal to be corrected.Each audio signal is assigned an identifier. The audio signals are preferably different radio transmitters, so that the identifier preferably indicates the respective radio transmitter. The audio signals can also originate from quite different audio sources and also have other identifiers (examples of such identifiers are: "DAB", "FM", "ZDF info", a CD hash code, "portable music player", "multimedia changer", Bluetooth audio profile X, "mobile telephone" or else an identifier of a recognizable advertising block within a radio or television program).Each audio signal is assigned a history which includes volume control information (how long the audio signal has already been heard; which volume has been set). Each audio signal can be assigned its own regulator coefficients.This identifier can be obtained differently for each audio signal. The identifier serves to distinguish different audio signals. Of course, audio sources can also be combined (for instance different CDs in a CD changer) or explicitly excluded from the treatment.In the following, the "volume" or volume setting is understood to mean the compensation value or value of the noise level controller or multiplier of the input signal. This does not state anything about the actual volume.When an audio signal is selected, the stored volume setting associated with that audio signal is used for this purpose. When an audio signal is left, the last volume value or last state of the control is stored depending on the identification of the audio signal.FIG. 1 shows an embodiment of the volume control apparatus for controlling the volume of various audio signals according to the first aspect of the invention. In this case, a source-oriented level adaptation is preferably carried out.The selected audio signal 1 is applied to the automatic volume control. The audio signal 1 is multiplied by a volume control variable 3 via a multiplier 2. A peak detector 5 detects the peak of the resulting loudness corrected signal 4 within a time interval ti (e.g., ti=0.1 s). A controller 6 is supplied with the output signal of the peak detector 5. Furthermore, a dynamic compressor can optionally be provided (not shown), which accepts the signal 1 and controls the multiplier 2 on the output side.The regulator 6 is preferably a nonlinear regulator 6 having a plurality of input ranges for the input signal 7. the regulator 6 preferably has four input ranges 10, 11, 12 and 13 which are delimited from one another by the threshold values S 0, S 1 and S 2. FIG. 2 shows an exemplary characteristic diagram of the nonlinear controller 6 having four input ranges 10 (zero signal range), 11 (adaptation range), 12 (working range) and 13 (headroom). The threshold value S0 delimits the zero signal range 10 from the adaptation range 11; the threshold value S1 delimits the adaptation range 11 from the working range 12; and the threshold value S2 delimits the working range 12 from the head room 13. In this case, the threshold values S 0-S 2 and thus also the input ranges 10- 13 have been designed to be time-dependent. However, this is not obligatory.The control 6 is preferably operated as follows:If the input signal 7 of the controller 6 is not greater than the zero signal range 10, then no regulation takes place. Otherwise, if the input signal 7 is not greater than the adaptation range 11, the volume is increased. Otherwise, the controller does not change the control value if the input signal 7 is not greater than the operating range 12. Otherwise, the volume is lowered (in this case, the input signal 7 is in the head room 13). The output signal 8 of the controller 6 preferably has three different output states, namely a state with volume reduction (e.g. "-1"), a state with no change of the control value (e.g. "0") and a state with volume increase (e.g. "+1"). A downstream integrator 9 is supplied with the output signal 8 of the "core" regulator 6.This mode of operation of the controller 6 corresponds to that of a three-point controller with an additional zero signal range.Each region 10-13 is associated with a control speed (V0-V3). These are different coefficients, which can also be zero.In a limiter 20, the volume setting 3 at the controller output (downstream of the integrator 9) is limited by a minimum volume Cmin and a maximum volume Cmax. In addition, an e x- element (not shown) can also be provided on the output side or on the input side of the limiter. Such an e x- member can be used to mitigate the effect that a regulator typically responds more nervously at a large input volume of signal 1 than at a small input volume.When the audio signal changes, volume control information 22, such as the last value of the integrator 9 or another state variable of the control loop (e.g. the last volume value 3), is stored in a storage means 21 (also referred to as history or audio source database) depending on the respective identifier 25. If the same audio signal is selected again later, that volume control information from the storage means 21 is selected and used for the volume control which is associated with this particular audio signal. The selection is made on the basis of the identifier 25 of the audio signal. As a result, depending on the progress of the regulation, a jump in volume when the audio signal changes is avoided or at least reduced.It is noted that for a plurality of audio signals which may be selectively applied to the volume control loop, the volume control information may be stored in the storage means 21. For example, a look-up table can be used for storing, wherein the respective table entry is stored or called up depending on the identifier 25 of the audio signal.In a preferred embodiment, the controller can be tuned as follows: the lower limit S2 of the head room 13 is -3 dB, i.e. the head room comprises output values of approximately 70% to 100%. The working range starts above S1= -13 dB. The zero signal range 10 is at modulation values of less than S0= -30 dB.The control speed or control weights in the ranges can be chosen as follows:head room 13: V3 = -30 dB per second with a selected integration interval ti=0.1 s (if the control of the controller control unit 7 is at least once in the head room 13, is controlled);Operating range 12: V2= 0 dB per second (the controller is then passive and the control value is frozen);Adaptation range 11: V1=0.02 dB per second (a time-discrete control with 1 dB steps every 50 s is also possible);zero signal range 10: V0=0 dB per second (the controller is passive; no control takes place and the control value is frozen).The regulation can additionally be carried out partially linearly, i.e. proportionally, to a control deviation from a setpoint value. For this purpose, a parallel linear PID controller 26 is shown in Fig. 1 using the coefficients P, I, and D. For the linear controller as well, a controller state variable 27 can be stored in the storage means 21 when the audio signal leaves and, when the same audio signal is selected again, can be read out again from the storage means 21 as a function of the identifier 25. The influence of the linear controller 26 on the entire control loop is adjusted by the weighting factor L (e.g. L=0.5). Instead of a parallel linear controller 26, linear controller components can also be obtained by linearly weighting the control deviations in the non-passive input ranges of the nonlinear controller 6 (and optionally also in the passive input range 12).The control method can also run through different time phases: the control time can be shortened in the initial phase (for example during the first selection of the new audio signal up to the time period of 1 minute) compared to the subsequent phase. The shortening of the control time can be effected by a time-dependent configuration of the control parameters V0, V1, V2, V3, P, I and L. In general, all parameters of the control can be a function of time.The above-described concept can be applied to multi-channel sources as well as single channel sources. In a special form, this also allows permanent differences between approximately the left or right channel to be compensated for. A source that is incorrectly switched on by the transmission station, for example (for example, if the right audio channel is switched on less than the left channel), can be selectively levelled out in order to achieve a balanced volume distribution.In principle, the control concept described in the application is not limited only to audio. Likewise, for example, the color components of a video signal can be levelled to a specific saturation range with this method.The concept can also be applied frequency-selectively, for example in order to transpose pieces of music into a desired sound profile (e.g. the bass component).The concept can be combined with all audio functions customary today, since these are typically applied after the source correction. Fading, sound regulations and the like are typically not affected by the method.The automatic control can be executed centrally (for example in central audio management) or decentrally (for example in a set-top box).In the embodiment shown in FIG. 1, two or more signals or signal sources are present at a single volume control device (the specific input into the controller is effected via a selector, not shown). The volume control device manages the volume information of the signals or signal sources by storing the volume information in the history.FIG. 3 shows an exemplary volume adjustment device for adjusting the volume of at least two audio signals 1, 100. It should be noted that the volume adjusting device shown in FIG. 3 does not belong to the invention, in addition to the description below. In this case, the automatic volume correction of a source (in this case of the audio signal 1) is compensated for by a controller-induced inverse influence of a central volume adjuster 110.The apparatus comprises a volume control 101 for automatically controlling the volume of the first audio signal 1. the volume control 101 can be used, for example, for a plurality of audio signals of different transmitters (for example, audio radio transmitters or TV transmitters), wherein the selection of the currently controlled transmitter is effected via a selector, not shown. The volume control 101 can preferably be used for all receivable transmitters of a service (e.g. audio radio or TV).It can be provided that the volume control 101 can also settle in the background (i.e. when the user is not currently listening to the audio signal 1). For the volume control 101, the volume control described in FIG. 1 can be used. The concept shown in FIG. 3 can therefore also be combined with the automatic volume control shown in FIG. 1. Signals and blocks in FIGS. 1 and 3 denoted by the same reference numerals correspond to each other. As already explained in connection with FIG. 1, the volume control 101 comprises a multiplier 2 which multiplies the first audio signal 1 by the volume control value 3 so that a volume-corrected audio signal 4 results. The remaining components of the volume control 101 are combined in a block 102.Furthermore, a central volume control 110 is provided, which is fed with an audio signal via a selector 112. The selector 112 selects the loudness corrected first audio signal 4 or the second audio signal 100 (which may optionally be corrected in a similar manner to the audio signal 4 loudness) depending on a selection signal 113. Further audio signals may be provided at the input of the selector 112 (not shown).The central volume control 110 comprises a multiplier 111 which serves for volume correction of the audio signal selected by the selector 112.The adjustment (here the multiplier of the multiplier 111) of the central volume controller comprises a manual adjustment component e m and an automatic adjustment component e a. In the example shown in FIG. 3, the total multiplication factor e g for the audio signal selected via the selector 112 is e g= e m · e a. When using logarithmic values, the values are added.The automatic setting component e a is selected such that it compensates at least partially or even completely for the volume correction of the first audio signal 1 by the volume control 101. For example, the automatic setting component e a can be determined in the form e a= f(x)=1 / x as a function of the volume control value 3 of the automatic volume control 101 in a block 120. Here, x describes the volume control value 3 of the automatic volume control 101. When using logarithmic values, 2 dB more in the automatic volume control results in -2 dB in the central volume control.If the volume correction of the automatic volume control 101 is compensated by the automatic setting component e a of the central volume control 110, the perceived volume does not change for the listener in the case of an activity of the volume control 101. When listening to the first audio signal 1, the listener will increase the volume of the first audio signal 1-if this is too quiet-by means of the manual setting component e m of the central volume regulator 110 (just as if there were no adjustment). However, the automatic control 101 operates in the background, the slow volume increase of which is compensated by the automatic setting component e a of the central volume control 110. When switching to the second (loud) audio signal 100 via the selector 112, the jump in volume is lower compared to a realization without regulation and without compensation of the regulation in the central volume regulator, since when switching, in addition to the manual setting e m the automatic setting e a in the central volume regulator 110 is also maintained. The volume jump then corresponds approximately to the difference between the volume of the second audio signal 100 and the volume of the volume-corrected first audio signal 4. If the second audio signal 100 already corresponds to the setpoint volume and the first audio signal has also been corrected to the setpoint volume by means of the automatic regulation after a sufficient adaptation time, no volume jump occurs when switching from the first to the second audio signal.In contrast to a conventional volume control without compensation in the central volume control, the listener does not notice nothing of the control in the approach and does not have to manually recorrect the volume with the central volume control 110 continuously during the control process.The volume setting is illustrated below using three tables.The first table 1 shows a conventional scenario from the prior art, in which a conventional central volume control is used, which is optionally used for setting the first audio signal 1 (e.g. the signal of a TV module) or the second audio signal 100 (e.g. the signal of a CD player). In Table 1, it is assumed that both audio signals 1 and 100 have a nominal loudness (here 50) and are of equal loudness. In contrast to FIG. 3, however, no automatic gain control is present. Furthermore, the central volume control element has only one manual adjustment possibility here; the automatic adjustment component e a at the central volume control element 110 is therefore not present here.The first three columns in Table 1 indicate the time (for example, in seconds), the respective volume of the second audio signal 100, and the respective volume of the first audio signal 1, respectively. The fourth column ("selected audio signal") indicates which audio signal is selected in each case at the respective point in time via the selector 112 (0:audio signal 100; 1:audio signal 1). The fifth column ("autom. Intervention") of Table 1 indicates the dB value of the central volume actuator automatic intervention (similar to e a in FIG. 3 ). This value is sent to the central volume control and added there with the user intervention (here an addition is used since these are dB values). Here, since no automatic intervention is provided in the case of Table 1, the values in the fifth column are zero. The sixth column ("We have. Intervention") indicates the manual intervention of the central volume control in dB (similar to e m in FIG. 3 ). This corresponds to the manual volume change which the user makes at the central volume control; this manual intervention is zero in Table 1, since the user-as discussed below-is compatible with the actual volume. The seventh column ("w. Volume") indicates the volume that the user actually wants to hear. This is an arbitrary value. The eighth column ("actual volume") indicates the actual volume of the signal output by the audio system, which results from the volume of the selected source and an arbitrarily selected factor (here 0.815). The ninth column ("Diff.") indicates the difference between the ninth and eighth columns.According to Table 1, the user does not manually change the volume at the central volume control since the desired volume and the actual volume coincide. At the time t=6, the first audio signal 1 is switched over. However, since both audio signals 1 and 100 have the same volume, no volume jump occurs during the switching. Table 1 Table 115050000414102505000041410350500004141045050000414105505000041410650501004141075050100414108505010041410950501004141010505010041410Table 2 again shows a scenario from the prior art without volume control. In contrast to the scenario shown in Table 1, in Table 2 both audio signal sources have a different basic volume. At the time t=6, the loud second audio signal 100 is switched over to the quiet first audio signal 1. At this time, since the desired volume is significantly lower than the actual volume, the user increases the volume through the manual operation. At the time t=11, the actual volume corresponds to the desired volume. At the time t=14, the user switches back to the second audio signal 100 again. Because it is too loud after the switch, the user manually adjusts again until the actual volume corresponds to the desired volume. Table 2 Table 215025000414102502500041410350250004141045025000414105502500041410650251004120-21750251054124-178502510104129-129502510154133-810502510204137-41150251025414101250251025414101350251025414101450250025416120155025002541612016502500204157161750250015415312185025001041498195025005414542050250004141021502500041410Table 3 shows an exemplary scenario with automatic volume control for the first audio signal 1 (e.g. for the audio signal of the TV module) and opposite automatic intervention in the central volume control 110 (see also FIG. 3 ). According to Table 3, it is assumed that both audio signal sources 1 and 100 have different basic loudness. In Table 3, instead of the audio signal 1, the volume-corrected first audio signal 4 (on the output side of the control) is shown.At the time t=1 the controller for the quiet first audio signal 4 (for example the controller of the TV module) determines that the volume is too low and slowly controls the volume high. This control process preferably takes place in the background, i.e. without the user actually having to have selected the first audio signal 4 (this takes place only later in this example, namely at the time t=6). However, it should be noted here that an automatic intervention in the central volume control 110 (see the fifth column) preferably takes place only when the first audio signal 4 has also actually been selected.At the time t=6, the user switches to the first audio signal 4. Since the volume control has not yet settled at this point in time, the first audio signal 4 is still 20 dB too quiet. Therefore, the user now starts to manually readjust via the central volume control 110. It can be seen from Table 3 that the automatic intervention in the automatic volume control element 110, which is in the opposite direction to the automatic regulation of the first audio signal 4, preferably only becomes active after selection of the first audio signal 4. Therefore, only the additional change in the volume of the first audio signal 4 that has taken place from the selection (i.e. only at the time t=6) of the first audio signal 4 is compensated for by the automatic intervention in the automatic volume control 110.At the time t=11, the actual volume corresponds to the desired volume. In contrast to Table 2, in Table 3 the user has not to change the volume manually to the greatest extent (cf. 23.75 in Table 3 with 25 in Table 2). This is due to the automatic volume increase until the time of the switching to the first audio signal 4 (the volume increase after the switching is, on the other hand, compensated by the automatic intervention in the central volume controller 110). As can be seen from Table 3, starting from the time t=12, the actual volume no longer changes despite an automatic increase in the volume of the first audio signal, since this increase is compensated by the central volume controller 110; the control process of the automatic volume control is therefore not audible to the user.At the time t=17, the system is switched over again to the second audio signal 100. With the switching, the automatic intervention in the central volume control 110 no longer changes, since the first audio signal 4 is no longer active. Nevertheless, the volume of the first audio signal 4 continues to change automatically. When switching to the second audio signal 100 at the time t=17, the actual volume is greater than the desired volume. In contrast to the changeover to the second audio signal 100 in table 2 (see time t=14 in table 2), the jump in volume in table 3 and the amount of the deviation from the desired volume are smaller (cf. 17 in table 3 versus 20 in table 2). This has two reasons: on the one hand, when switching from the first audio signal 4 to the second audio signal 100, in addition to the manual setting, the automatic intervention (here -2.5 in table 3) in the central volume controller is also maintained, so that the volume is thereby reduced. On the other hand, unlike Table 2 in Table 3, the user does not have to change the volume manually quite as strongly beforehand (cf. 23.75 in Table 3 with 25 in Table 2), whereby the volume jump is additionally reduced. However, since the volume after the switch is still too loud, the user manually adjusts and reduces the value of the manual intervention.At the time t=23, the actual volume again corresponds to the desired volume. Nevertheless, in the background (the user currently hears the second audio signal 100), the automatic volume control further increases the volume of the first audio signal 4 and thus decreases the difference from the volume of the second audio signal 100.At the time t=27, the user switches back to the first audio signal 4. the amount of the difference between the actual volume and the desired volume is significantly less at 37% at this time than at the time t=6. At the time t=28, it is assumed that the user does not compensate for the difference manually because the user desires a lower volume from this time on. Although in the background the automatic volume control further increases the volume of the first audio signal 4, the actual volume delivered does not change, since the automatic adjustment component compensates for the additional change in the volume of the first audio signal that has taken place from the selection of the first audio signal by an additional change in the opposite direction.At time t=32, the user switches back to the second audio signal 100. The user had not previously compensated manually, i.e. he was satisfied with the volume. Thus, starting from t=33, it is assumed that this actual volume corresponds to the desired volume (the user's request is thus now 40). At the time t=34, the first audio signal 4 is switched over again. As was to be expected, the return now fails too quietly. The user therefore starts to manually readjust. At time t=37, the actual volume agrees with the desired volume and no longer changes, although the automatic gain control further increases the level of the first audio signal 4.From the time t=110, the level of the first audio signal 4 has settled. At the time t=12, the user switches back to the second audio signal 100, which was still substantially louder than the first audio signal 4 at the time t=1. However, the user no longer detects a jump in volume during the changeover. Even when switching to the first audio signal later at the time t=15, the user will not take a jump in volume because the levels are the same.As can be seen from Table 3, in the concept illustrated here, the user is not disturbed by a successive volume change of the automatic volume control, although the automatic volume control works in an audible manner for the user. The user does not notice that the loudness control is operating, because either the first audio signal 4 is not selected or because the loudness change is compensated in the central loudness controller 110. The user manually adjusts the desired volume and this volume is also obtained by the user; i.e., there is no slow volume drift. Table 3 Table 3150250004141025025,250004141035025,50004141045025,7500041410550260004141065026,251004121-2075026,51-0,2554125-1685026,751-0,5104130-11950271-0,75154134-7105027,251-1204138-3115027,51-1,2523,7541410125027,751-1,523,75414101350281-1,7523,7541410145028,251-223,7541410155028,51-2,2523,7541410165028,751-2,523,75414101750290-2,523,75415817185029,250-2,523,75415817195029,50-2,515415110205029,750-2,510414762150300-2,52,541410225030,250-2,52,541410235030,50-2,52,541410245030,750-2,52,5414102550310-2,52,541410265031,250-2,52,541410275031,51-2,52,54126-15285031,751-2,752,5262602950321-32,526260305032,251-3,252,526260315032,51-3,52,526260325032,750-3,52,52640143350330-3,52,540400345033,251-3,52,54026-14355033,51-3,75104032-8365033,751-4154036-43750341-4,2519,2540400385034,251-4,519,2540400395034,51-4,7519,2540400405034,751-519,25404004150351-5,2519,2540400425035,251-5,519,2540400435035,51-5,7519,2540400445035,751-619,25404004550361-6,2519,2540400465036,251-6,519,2540400475036,51-6,7519,2540400485036,751-719,25404004950371-7,2519,2540400505037,251-7,519,2540400515037,51-7,7519,2540400525037,751-819,25404005350381-8,2519,2540400545038,251-8,519,2540400555038,51-8,7519,2540400565038,751-919,25404005750391-9,2519,2540400585039,251-9,519,2540400595039,51-9,7519,2540400605039,751-1019,25404006150401-10,2519,2540400625040,251-10,519,2540400635040,51-10,7519,2540400645040,751-1119,25404006550411-11,2519,2540400665041,251-11,519,2540400675041,51-11,7519,2540400685041,751-1219,25404006950421-12,2519,2540400705042,251-12,519,2540400715042,51-12,7519,2540400725042,751-1319,25404007350431-13,2519,2540400745043,251-13,519,2540400755043,51-13,7519,2540400765043,751-1419,25404007750441-14,2519,2540400785044,251-14,519,2540400795044,51-14,7519,2540400805044,751-1519,25404008150451-15,2519,2540400825045,251-15,519,2540400835045,51-15,7519,2540400845045,751-1619,25404008550461-16,2519,2540400865046,251-16,519,2540400875046,51-16,7519,2540400885046,751-1719,25404008950471-17,2519,2540400905047,251-17,519,2540400915047,51-17,7519,2540400925047,751-1819,25404009350481-18,2519,2540400945048,251-18,519,2540400955048,51-18,7519,2540400965048,751-1919,25404009750491-19,2519,2540400985049,251-19,519,2540400995049,51-19,7519,25404001005049,751-2019,254040010150501-20,2519,254040010250500-20,2519,254040010350500-20,2519,254040010450500-20,2519,254040010550501-20,2519,254040010650501-20,2519,254040010750500-20,2519,254040010850500-20,2519,2540400FIG. 4 shows the time curves of the variables shown in Table 3 in graphical form. With regard to the profile of the selected audio signal, it should be noted that, at a logic high level, the first audio signal 4 is selected and, at a logic low level, the second audio signal 100 is selected.As described above, the invention solves the problem of large and permanent volume differences of different audio signals, for example in the motor vehicle. Systematic deviations in the audio signal can be compensated for by the invention; instantaneous content-specific deviations are preferably hardly compensated for or not compensated for at all. A source-selective adaptive configuration allows a uniform sound level / image to be achieved after a settling time. This results in high ease of use. As discussed in connection with FIG. 3, the control can be designed such that it operates completely unnoticed by the user.Finally, it is noted that the concepts have been explained above with reference to an automatic volume control with feedback loop. Instead of automatic gain control with feedback loop, however, automatic gain control with feedforward can also be used (feed-forward control). In this case, the volume control variable for volume correction is typically determined on the basis of a level measurement (for example peak value measurement) of the audio signal which has not been corrected for volumes.

Claims

Volume control device for controlling the volume of various audio signals (1), comprising: - a volume control for automatically controlling the volume for a respectively selected audio signal (1); and - a storage means (21) for storing volume control information (22, 27, 3) per audio signal, wherein the volume control information (22, 27, 3) comprises - a state variable (22, 27) of a state of the volume control resulting within the framework of the automatic control process or - a volume control variable (3) automatically set by the volume control within the framework of the automatic control process, wherein - the volume control device is configured such that, when an audio signal (1) is selected, the current state variable (22, 27) or current volume control variable is stored in the storage means (21) as volume control information (3) for the previously selected audio signal (1), and - when an audio signal (1) is selected, the volume control information (22, 27, 3) stored in the storage means (21) for the audio signal (1) is used for controlling or setting the volume of the audio signal (1).Volume control device according to claim 1, wherein each audio signal (1) is assigned its own identifier (25), and the storage means (21) is configured to store the volume control information (22, 27, 3) and the associated identifier (25) per audio signal (1).Volume control device according to one of the preceding claims, wherein the volume control comprises a non-linear controller (6).Volume control device according to claim 3, wherein - the non-linear controller (6) is a controller which distinguishes between at least three input ranges for the input signal of the controller, namely a first input range (11), an overlying second input range (12) and a third input range (13) overlying the second input range; - the controller causes an increase in the volume when the input signal (7) of the controller (6) lies in the first input range (11), - the controller (6) causes a decrease in the volume when the input signal (7) of the controller (6) lies in the third input range (13), and - the controller (6) keeps the volume constant when the input signal (7) of the controller (6) lies in the second input range (12).Volume control device according to claim 4, wherein the size of the three input areas (11, 12, 13) is time dependent, and the size of the second input area (12) increases with increasing time after the first selection of the respective audio signal (1) and the size of the first (11) and / or third (13) input area decreases with increasing time after the first selection of the respective audio signal.Volume control device according to one of the preceding claims, wherein the volume control comprises a controller (6) and the controller (6) is configured such that substantially no control takes place for input signal values (7) of the controller (6) within a specific input range, namely for input signal values (7) less than or less than or equal to a zero signal threshold (S0).Volume control device according to one of Claims 4 - 5 or according to Claim 6 which relates back to Claim 4, wherein the control speed is smaller in terms of absolute value in the first input region (11) than in the third input region (13).The volume control apparatus according to any preceding claim, wherein the volume control information further indicates how long the audio signal has already been selected.Audio or audio / video reproduction device for a motor vehicle, which - is configured to reproduce different audio signals (1), and - comprises a volume control device according to one of the preceding claims.Audio or audio / video playback device according to claim 9, comprising at least two radio broadcast receivers, in particular two radio broadcast receivers or two radio broadcast receivers or one radio broadcast receiver and one radio broadcast receiver, wherein - the first radio receiver is used for playback of a selected transmitter and - the second radio receiver in the background is used for adjusting the volume of at least one other transmitter by means of the volume control device, and when the other transmitter is played back, the volume control information (22, 27, 3) stored in the storage means is used for controlling or adjusting the volume of the other transmitter.Method for regulating the volume of various audio signals, wherein - the volume for a selected audio signal (1) is automatically regulated with an automatic volume regulation; - when the previously selected audio signal (1) is selected, a current state variable (22, 27) of the state of the automatic volume regulation resulting within the scope of the automatic regulation process or the current volume manipulated variable (3) automatically set by the volume regulation within the scope of the automatic regulation process is stored in a storage means (21) as volume regulation information (22, 27, 3); and - when this audio signal (1) is selected, the volume regulation information (22, 27, 3) stored in the storage means (21) for the audio signal (1) is used for regulating or setting the volume of the audio signal (1).Method according to Claim 11, wherein - the volume for different audio signals (1) is successively automatically controlled in the background by means of automatic volume control; and - the respectively present state variable (22, 27) of the automatic volume control or the present volume manipulated variable (3) is stored in a storage means (21) as volume control information (22, 27, 3) for the respective audio signal.

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