Abstract:
The present invention provides an audio outputting apparatus, including an audio reproducing section configured to reproduce an audio signal from an input signal, setting sections configured to set a limitation level for the audio signal reproduced by the audio reproducing section, a detecting section configured to detect that a level of the audio signal reproduced by the audio reproducing section exceeds a limitation level set by the setting sections, and a limiting section configured to apply the limitation processing to a portion of the audio signal reproduced by the audio reproducing section exceeding the limitation level based on a detection result of the detecting section.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-400891, filed Nov. 28, 2003, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an audio outputting apparatus and an audio outputting method of restoring an audio signal from an input signal and outputting the audio signal.  
         [0004]     2. Description of the Related Art  
         [0005]     As is well known, for example, during watching a television broadcast program, an audio volume is rapidly increased due to a sound effect or when a program content is switched from a main story into a commercial and a TV audience may be forced to decrease an audio volume immediately.  
         [0006]     With respect to this problem, Jpn. Pat. Appln. KOKAI Publication No. 5-226953 discloses a configuration to reduce an output audio level with respect to a high level of audio input by a compressor having an input and output property of nonlinear and control an audio volume within a predetermined scope.  
         [0007]     However, according to this configuration disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-226953, all levels of the input audio are controlled by the compressor and a small level of the input audio is further controlled into a smaller level, so that this configuration is not suitable for practical use.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     According to one aspect of the present invention, there is provided an audio outputting apparatus, comprising: an audio reproducing section configured to reproduce an audio signal from an input signal; setting sections configured to set a limitation level for the audio signal reproduced by the audio reproducing section a detecting section configured to detect that a level of the audio signal reproduced by the audio reproducing section exceeds a limitation level set by the setting sections; and a limiting section configured to apply the limitation processing to a portion of the audio signal reproduced by the audio reproducing section exceeding the limitation level based on a detection result of the detecting section.  
         [0009]     According to another aspect of the present invention, there is provided an audio outputting method, comprising: a first step of reproducing an audio signal from an input signal; second steps of setting a limitation level for the audio signal reproduced by the first step; a third step of detecting that a level of the audio signal reproduced by the first step exceeds a limitation level set by the second steps; and a fourth step of applying the limitation processing to a portion of the audio signal reproduced by the first step exceeding the limitation level based on a detection result of the third step. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0010]      FIG. 1  is a block diagram showing a digital television broadcast receiver according to an embodiment of the present invention;  
         [0011]      FIG. 2  is an outside drawing showing a remote controller of the digital television broadcast receiver according to the embodiment;  
         [0012]      FIG. 3  shows an example of an audio control selection menu displayed by the digital television broadcast receiver according to the embodiment;  
         [0013]      FIG. 4  shows an example of an audio setting menu displayed by the digital television broadcast receiver according to the embodiment;  
         [0014]      FIG. 5  shows an example of a state that an audio volume is set on an audio setting menu displayed by the digital television broadcast receiver according to the embodiment;  
         [0015]      FIG. 6  shows a limitation of an amplitude level of an analog audio signal carried out by the digital television broadcast receiver according to the embodiment;  
         [0016]      FIG. 7  is a flow chart showing main operation carried out by the digital television broadcast receiver according to the embodiment;  
         [0017]      FIG. 8  is a characteristic diagram showing a relationship between an audio volume of the digital television broadcast receiver and a digital audio signal according to the embodiment; and  
         [0018]      FIG. 9  shows a limitation of a level of a digital audio signal carried out by the digital television broadcast receiver according to the embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     An embodiment of the present invention will be described in detail below.  FIG. 1  shows a digital television broadcast receiver described in this embodiment. In other words, a digital television signal received by an antenna  11  is supplied to a tuner  12  and a signal of a specific channel is selected.  
         [0020]     A broadcast signal selected by this tuner  12  is supplied to a signal processing section  13 . This signal processing section  13  applies error correction processing, scramble release processing and TS (Transport Stream) packet conversion processing to the input broadcast signal. Then, this signal processing section  13  outputs an image signal for each packet to an MPEG (Moving Picture Experts Group) image reproducing section  14  and outputs an audio signal for each packet to an MPEG audio reproducing section  15 .  
         [0021]     Among these sections, the MPEG image reproducing section  14  may apply the decoding processing corresponding to the compression coding processing to the input image signal and may reproduce an analog image signal, and may output it to an OSD (On Screen Display) section  16 . This OSD section  16  superimposes a specific OSD signal on the input image signal, outputs it to a display section  17  composed of a CRT (Cathode Ray Tube) or the like to display the image thereon.  
         [0022]     In addition, the above-described MPEG audio reproducing section  15  may apply the decode processing corresponding to the compression coding processing to the input audio signal and may reproduce an analog audio signal, and may output it to an audio controlling section  18 .  
         [0023]     When a level of the input audio signal is higher than a limitation level that has been set in advance by a user, this audio controlling section  18  may control a voice signal exceeding the limitation level to suppress a level thereof. Then, an audio signal to be output from this audio controlling section  18  is supplied to a speaker  19  and audio is reproduced. Thereby, the audio volume is prevented from being larger than the predetermined audio volume.  
         [0024]     In this case, in this digital television broadcast receiver, all operations including the above-described operations are generally controlled by a CPU (Central Processing Unit)  20 . This CPU  20  may receive the operation information transmitted from a remote controller  21  via a receiving section  22  and may control each section so that the operation content is reflected.  
         [0025]     In this case, the CPU  20  uses a memory section  23 . In other words, this memory section  23  may include a read only memory having a control program executed by the CPU  20  stored therein, a read and write memory of providing an operation area to the CPU  20 , and an in volatile memory or the like having various set information and control information or the like therein.  
         [0026]      FIG. 2  shows the outline of the remote controller  21 . In this remote controller  21 , a power supply key  24 , a one-touch select key group  25 , a receiving mode switch key group  26 , a channel up down key  27 , an audio volume adjusting key  28 , a return key  29 , an end key  30 , a shift key  31 , a decision key  32 , and a menu key  33  or the like are mainly set.  
         [0027]     In this case, the user can select whether the level control of the audio signal is carried out. In other words, by operating the menu key  33  of the remote controller  21  and sequentially selecting a predetermined item from the menu displayed on the display section  17 , the user may display an audio control select menu.  
         [0028]     This audio control select menu, as shown in  FIG. 3 , displays an item  34  of “control audio” and an item  35  of “no control audio”. By operating the shift key  31  of the remote controller  21 , the user may select any of the items  34  and  35  and by operating the predetermined decision key  32 , the user can select whether the level control of the audio signal is controlled by the audio controlling section  18 .  
         [0029]     In addition, if the item  34  of “control audio” is selected by the audio control select menu, the CPU  20  may display the audio volume set menu on the display section  17 . As shown in  FIG. 4 , this audio volume set menu displays a bar item  36  that a state of “0” of the audio volume corresponds to one end and a state of “the maximum” of the audio volume corresponds to many ends, and an index  37  moving along an item  36  corresponding to the audio volume, so that the audio volume can be grasped visually.  
         [0030]     Then, the user may operate the audio volume adjusting key  28  while hearing the audio of the television broadcast program practically, and when acquiring the audio volume, which the user judges preferable, the user may operate the decision key  32 . As a result, as shown in  FIG. 5 , an audio set index  38  is displayed on the item  36 , and in this time, an audio volume of which level should be controlled is set.  
         [0031]     Thus, if the audio volume of which level should be controlled is set, the CPU  20  may calculate an amplitude level of the audio signal corresponding to the set audio volume, and the CPU  20  may make the in volatile memory or the like of the memory section  23  to hold the calculation result as a limitation level.  
         [0032]     Then, as shown in  FIG. 6 , the audio controlling section  18  may compare the amplitude level of the input audio signal with the limitation level and may control the audio signal having the amplitude level exceeding the limitation level substantially not to be output by clipping it to the limitation level.  
         [0033]     In the meantime, under the state that the item  35  of “no control audio” is selected by the audio control select menu, that is to say, under the state that the audio controlling section  18  is set so as not to carry out the level control of the audio signal, the audio controlling section  18  may operate so as to pass the input audio signal as it is.  
         [0034]      FIG. 7  is a flow chart including main operations of the above-described digital television broadcast program. At first, if the processing is started (step S 1 ), the CPU  20  may determine whether the audio control is set to be done in step S 2 .  
         [0035]     Then, when it is determined that the audio control is not performed (NO), the CPU  20  may control the audio controlling section  18 , and making the audio controlling section  18  to output the audio signal in step S 10 , the CPU  20  may terminate the processing (step S 11 ).  
         [0036]     In addition, if it is determined that the audio control should be done in the step S 2  (YES), the CPU  20  may determine whether the limitation level is set in step S 3 .  
         [0037]     Then, if it is determined that the limitation level is not set (NO), the CPU  20  may make the audio volume set menu to be displayed on the display section  17  in step S 4 , and if the audio volume is set in step S 5  by the user, the CPU  20  may calculate the amplitude level of the audio signal corresponding to the set audio volume, namely, the limitation level in step S 6  and may make the in volatile memory or the like of the memory section  23  to hold it.  
         [0038]     After the step S 6 , or in the case of judging that the limitation level is set in the step S 3  (YES), the CPU  20  may instruct the audio controlling section  18  to perform the level control operation in step S 7 . Thereby, the audio controlling section  18  may judge whether the amplitude level of the input audio signal substantially exceeds the limitation level in step S 8 .  
         [0039]     Then, when it is judged that the amplitude level of the input audio signal substantially exceeds the limitation level (YES), the audio controlling section  18  may clip the audio signal having the amplitude level substantially exceeding the limitation level to the limitation level in step S 9 .  
         [0040]     After the step S 9 , or when it is judged that the amplitude level of the input audio signal substantially does not exceed the limitation level (NO) in the step S 8 , the audio controlling section  18  may output an audio signal in the step S 10  and the CPU  20  may terminate the processing (step S 11 ).  
         [0041]     According to the above-described embodiment, comparing the amplitude level of the audio signal with the predetermined limitation level, the audio signal having the amplitude level substantially exceeding the limitation level is clipped to the limitation level. Therefore, it is possible to effectively suppress rapid increase of the audio volume.  
         [0042]     In addition, since the audio signal having the amplitude level substantially exceeding the limitation level is clipped to the limitation level, the audio signal of the amplitude level not exceeding the limitation level substantially is provided for reproduction of the audio as it is without being provided with any level control, so that this audio signal can be sufficiently suitable for practical use.  
         [0043]     In the meantime, according to the above-described embodiment, the audio signal having the amplitude level substantially exceeding the limitation level is clipped to the limitation level, however, other than clipping, the audio signal having the amplitude level substantially exceeding the limitation level may be muted.  
         [0044]     In addition, according to the above-described embodiment, the level control of the analog audio signal is described, however, for example, even when the digital audio signal is output from the above-described MPEG audio reproducing section  15 , it is possible to perform the level control processing to that digital audio signal.  
         [0045]     For example, as shown in  FIG. 8 , it is assumed that from “0” of the audio volume to “the maximum” thereof are set so as to correspond to 16 bit digital audio signal of “0000000000000000” to “1111111111111111”.  
         [0046]     In this case, as shown in  FIG. 9 , if the limitation level is set, for example, at “0000111000011101” or the like, it is possible to attenuate the digital audio signal having a value substantially exceeding this limitation level by an attenuator.  
         [0047]     In addition, it is also possible to lower the audio volume by adding a signal of the inversed phase of a portion of the digital audio signal exceeding the set value substantially to this portion by using a device of converting the original output audio waveform into an inversed phase other than the attenuator.  
         [0048]     Further, according to the above-described embodiment, the case of adopting the present invention to the digital television broadcast receiver is described, however, not limited to this, for example, it is possible to widely adopt the present invention to various devices to reproduce the audio signal recorded in a recording medium such as a tape, a semiconductor memory, and a disk or the like and a device to receive the audio broadcast or the like.  
         [0049]     In the meantime, the present invention is not limited to the above-described embodiment as it is, and in the practice stage, various modifications of can be used within a scope of a spirit of the present invention. In addition, by composing a plurality of constituent elements disclosed in the above-described embodiment, various inventions are available. For example, from among all constituent elements of the embodiment, some of them may be deleted. Further, the constituent elements of the different embodiments may be combined appropriately.