CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     The present invention contains subject matter related to Japanese Patent Application JP 2004-263468 filed in the Japanese Patent Office on Sep. 10, 2004, and Japanese Patent Application JP 2005-220312 filed in the Japanese Patent Office on Jul. 29, 2005, 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 a method and a device for identifying a user when a plurality of users use the device, and an electronic apparatus and an electronic system incorporating the device.  
         [0004]     2. Description of the Related Art  
         [0005]     A plurality of users, such as a plurality of family members, often share a single electronic apparatus, and the setting and processes of the apparatus are switched on a per user basis. The electronic apparatuses used in such a manner are increasing in number.  
         [0006]     For example, a user enters a keyword on a digital versatile disk (DVD) player to automatically record a program corresponding to the keyword. A plurality of users can set their own keywords.  
         [0007]     For such an apparatus to identify each user, the user enters the user&#39;s own name and password on a menu screen displayed on one of a remote controller and the main unit of the apparatus.  
         [0008]     Japanese Unexamined Patent Application Publication No. 61-172239 discloses a method of an apparatus that identifies a user using a voice recognition technique. The apparatus identifies the user by the user&#39;s own voice when the user operates the apparatus.  
         [0009]     Japanese Unexamined Patent Application Publication No. 2003-228460 discloses a stylus of a mobile information terminal. The stylus includes a piezoelectric sounder. For example, the stylus is missing. A user claps the user&#39;s hands in a particular rhythm and a microphone in the stylus picks up the sound of hand claps of the user. The piezoelectric sounder activates the sound thereof.  
       SUMMARY OF THE INVENTION  
       [0010]     For an apparatus to identify a user, the user enters the user&#39;s own name and password on a menu screen of one of a remote controller of an apparatus and the main unit of the apparatus. Such an operation is inconvenient to the user.  
         [0011]     In a method of entering the user&#39;s own name and password to an apparatus by means of the user&#39;s own voice, the user vocalizes sound to the apparatus. Such an operation is not likely to be well accepted by most of the users. The human voice is easily buried in the environmental sound, and it is difficult to correctly determine the human voice.  
         [0012]     High level of individual authentication such as security check may be required if the apparatus is used by a large number of users. But if the same apparatus is shared by a limited number of users, such as family members, such a high level of individual authentication is not required.  
         [0013]     It is thus desirable to provide an apparatus that identifies the user easily and accurately by a simple operation.  
         [0014]     In accordance with one embodiment of the present invention, a method of identifying a user, includes steps of registering, in a memory, clapping patterns of clapping of a plurality of users with a user identification for identifying each user associated with a respective clapping pattern, picking up the sound of claps to acquire an input audio signal responsive to the clapping sound, processing the acquired input audio signal to detect a clapping pattern, and comparing the detected clapping pattern with the registered clapping pattern to determine whether any of the clapping patterns registered in the memory matches the detected clapping pattern and in the event of the presence of one of the registered clapping patterns matching the detected hand pattern, identifying the user by the user identification, registered in the memory, associated with the matching clapping pattern.  
         [0015]     In accordance with the user identification method, in a pattern unique to the user, the user can allow the apparatus to identify himself in a simple operation, for example, clapping his hands, striking a bell located close to the apparatus, or patting the edge of the casing of the apparatus.  
         [0016]     Unlike human voice, such a sound is not easily buried in the environment sound. The apparatus thus easily recognizes the sound pattern and identifies the user.  
         [0017]     In accordance with embodiments of the present invention, a simple operation of the user allows the apparatus to easily identify the user. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  illustrates a user identification device and an electronic apparatus in accordance with one embodiment of the present invention;  
         [0019]      FIG. 2  illustrates the waveform of a registered hand-clapping pattern;  
         [0020]      FIG. 3  illustrates the waveform of a registered hand-clapping pattern;  
         [0021]      FIGS. 4A and 4B  illustrate the hand-clapping pattern;  
         [0022]      FIG. 5  illustrates the hand-clapping pattern of each user;  
         [0023]      FIG. 6  illustrates a hand-clapping pattern registration process;  
         [0024]      FIG. 7  illustrates the detection of a hand-clapping pattern during user identification;  
         [0025]      FIG. 8  illustrates a user identification process;  
         [0026]      FIGS. 9A-9C  illustrate the switching of setting of the device in response to the user identification;  
         [0027]      FIG. 10  illustrates a first system using a remote controller;  
         [0028]      FIG. 11  illustrates a second system using a remote controller;  
         [0029]      FIG. 12  illustrates a third system using a remote controller;  
         [0030]      FIG. 13  illustrates the remote controller of  FIG. 10 ;  
         [0031]      FIG. 14  illustrates a content recording and playback apparatus of  FIG. 10 ;  
         [0032]      FIG. 15  illustrates a user identification process performed by the remote controller of  FIG. 13 ;  
         [0033]      FIG. 16  illustrates a system that identifies a user using an application program of a personal computer; and  
         [0034]      FIGS. 17A and 17B  illustrate a waveform of a single hand clap sound. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
       [0035]      FIG. 1  illustrates a user identification device, and a content recording and playback apparatus  10 , as an electronic apparatus, including the user identification device.  
         [0036]     The content recording and playback apparatus  10  includes a central processing unit (CPU)  11 . A bus  12  of the CPU  11  connects to a read-only memory (ROM)  13  storing a variety of programs and data, and a random-access memory (RAM)  14  on which the program and data are expanded.  
         [0037]     A hard disk  15  is connected to the bus  12  via an input and output port  16 . A recording medium  17 , such as a compact disk (CD) or a digital versatile disk (DVD), is connected to the bus  12  via an input and output port  18 . A transceiver antenna  22  is connected to the bus  12  via a (radio frequency) RF interface  21  such as an RF transceiver circuit. The bus  12  connects to an external interface  23  for connection with the Internet  1 .  
         [0038]     The hard disk  15  and the recording medium  17  store contents such as video and music for playback. The RF interface  21  and the transceiver antenna  22  receive a content from the outside in a wireless fashion, and transmits a content to the outside. The external interface  23  receives a content from the outside via the Internet  1  and transmits a content to the outside via the Internet  1 .  
         [0039]     An operation unit  31 , composed of a variety of keys, is connected to the bus  12  via an interface  32 . A display  34 , such as a liquid-crystal display (LCD), is connected to the bus  12  via an interface  33 . A loudspeaker  38  is connected to the bus  12  via an input and output port  35 , a digital-to-analog (D/A) converter  36 , and an audio amplifier circuit  37 .  
         [0040]     The display  34  displays, on the screen thereof, video and images as contents, and a setting screen different from user to user to be discussed later. The loudspeaker  38  outputs music and sound as a content and an audio announcement.  
         [0041]     A microphone  41  is connected to the bus  12  via an audio amplifier  42 , an analog-to-digital (A/D) converter  43 , and an input and output port  44 . A non-volatile memory  45  is connected to the bus  12 .  
         [0042]     A hand-clap sound generated by a user is picked up by the microphone  41 , converted by the A/D converter  43  from an analog signal to a digital signal, and captured by the bus  12 . As previously discussed, the non-volatile memory  45  registers beforehand a hand-clapping pattern of the hand claps of each user.  
         [0043]     A user identification device  40  includes a hand-clapping sound input block (hand-clapping sound acquisition block), an arithmetic processing block (arithmetic controller), and the non-volatile memory  45 . The hand-clapping sound input block includes the microphone  41 , the audio amplifier  42 , the A/D converter  43 , and the input and output port  44 . The arithmetic processing block includes the CPU  11 , the ROM  13 , and the RAM  14 . The hand-clapping pattern can be registered in a portion of the hard disk  15  instead of the non-volatile memory  45 .  
         [0044]     The content recording and playback apparatus  10  is used by a plurality of users. Each user records and plays back the user&#39;s own preferred program.  
         [0045]     Each user claps the user&#39;s hands to register beforehand the hand-clapping pattern unique to the user onto the non-volatile memory  45 .  
         [0046]      FIGS. 2 and 3  illustrate four users having respectively user identifiers U 1 , U 2 , U 3 , and U 4 , and waveforms of the registered hand-clapping patterns.  
         [0047]     To register the hand-clapping pattern, the user claps the user&#39;s hands for a plurality of times more than predetermined N times. The hand-clapping pattern is changed from user to user. The right-hand portion of  FIGS. 2 and 3  illustrate rhythm charts approximating the hand-clapping pattern.  
         [0048]     The arithmetic processing block, composed of the CPU  11 , the ROM  13 , and the RAM  14 , processes an input audio signal of a hand-clapping sound, and detects as a hand clap a point where the hand-clapping sound sharply rises in sound pressure level and reaches a predetermined threshold. The arithmetic processing block detects the hand-clapping pattern from the detection results.  
         [0049]     As shown in  FIG. 4A , the hand-clapping sound is detected as a hand clap when the sound level thereof reaches the threshold value at time t(i) (i=1, 2, 3, . . . , n) within a predetermined period of time D(input) from an input start point t( 0 ). A time interval d(i) between two hand claps adjacent to each other in time sequence represented by equation (1) shown in  FIG. 4B  is detected.  
         [0050]     When a predetermined mute period of time D(end) has elapsed since the detection of last hand clap of the predetermined N or more hand claps, the detection of the hand claps ends. The hand claps of N times or more are detected because the hand-clapping pattern is difficult to be detected with a smaller number of hand claps.  
         [0051]     If no sound is picked up within a predetermined period of time D(start) from the input start point t( 0 ) or within a predetermined period of time D(input) from the input start point t( 0 ), an input error is triggered. The user is requested to hand his claps again, or a predetermined state resumes for example, a menu screen is displayed. If hand claps last to sound even after the predetermined period of time D(input) from the input start point t( 0 ), an input error is triggered.  
         [0052]     If no input error is triggered, an overall length of time for picking up the hand claps d(sum), namely, a period of time from time t( 1 ) to time(n) is calculated using equation (2) of  FIG. 4B . As represented by equation (3) of  FIG. 4B , the time interval d(i) is divided by the overall length of time d(sum) to result in normalized time interval d′(i). Herein, i of the normalized time interval d′(i) ranges from 2 to n.  
         [0053]     The number of hand claps n, the normalized time interval d′(i), and the overall length of time d(sum) are stored onto the non-volatile memory  45  as a hand-clapping pattern of the user with the user identification ID of the user associated therewith.  
         [0054]      FIG. 5  lists the registered hand-clapping pattern of each user, namely, the number of hand claps n, the normalized time interval d′(i), and the overall length of time d(sum), in response to the waveforms of the hand claps of the users shown in  FIGS. 2 and 3 .  
         [0055]      FIG. 6  illustrates a hand-clapping pattern registration process  50  performed by the CPU  11  in the content recording and playback apparatus  10 . In the hand-clapping pattern registration process  50 , the user selects himself as a user to be registered. More specifically, a user who desires to register his own hand-clapping pattern operates the operation unit  31  to enter his own name. The CPU  11  sets a user ID corresponding to the input user name.  
         [0056]     In step  52 , the CPU  11  displays a message, for example, reading “Clap hands” on the display  34 . The CPU  11  also outputs an audio announcement “Clap hands” from the loudspeaker  38 . In this way, the user is requested to clap his hands. In response, the user claps his hands.  
         [0057]     In step  53 , after the detection of the hand claps, the CPU  11  determines whether a mute period lasting over the predetermined period of time D(end) has elapsed. If no sound is picked up within the predetermined period of time D(start) from the input start point t( 0 ), an input error is triggered.  FIG. 6  illustrates an operation example when a predetermined number of hand claps are generated with no input error triggered.  
         [0058]     If the predetermined mute period of time D(end) has elapsed since the detection of the hand claps, the CPU  11  proceeds from step  53  to step  54 . The CPU  11  detects the hand-clapping pattern by processing the input audio signal as previously discussed. Processing proceeds to step  55  to determine whether the user accepts the registration.  
         [0059]     In the registration acceptance procedure, the CPU  11  controls the display  34  to display a message, for example, reading “Are you satisfied with your current hand claps?”, and the loudspeaker  38  to output an audio announcement stating “Are you satisfied with your current hand claps?”. Alternatively, a detected hand clap sound is converted into a drum sound using a musical instrument digital interface (MIDI) and then output from the loudspeaker  38  for user determination. In response, the user replies acceptance or rejection using the operation unit  31 .  
         [0060]     In step  56 , the CPU  11  determines whether the user has accepted the registration. If the CPU  11  determines the user has not accept the registration, processing returns to step  52  to request the user to claps his hands again.  
         [0061]     If the CPU  11  determines that the user has accepted the registration, processing proceeds from step  56  to step  57 . The CPU  11  stores, onto the non-volatile memory  45 , the hand-clapping pattern detected in step  54  with the user name, and the set user ID shown in  FIG. 5  associated therewith.  
         [0062]     After the registration, the user causes the content recording and playback apparatus  10  to identify the user. For example, each user searches for a program recorded on one of the hard disk  15  and the recording medium  17  in the content recording and playback apparatus  10 , and claps his hands to play back a searched program in the same manner as in the hand clapping registration process.  
         [0063]     The arithmetic processing block including the CPU  11 , the ROM  13 , and the RAM  14  processes the input audio signal as the hand clap sound in the same way as in the registration. The arithmetic processing block detects as a hand clap a point where the hand-clapping sound sharply rises in sound pressure level and reaches a predetermined threshold. The arithmetic processing block detects the hand-clapping pattern from the detection results.  
         [0064]     As previously described with reference to  FIG. 4A , the hand-clapping sound is detected as a hand clap when the sound level reaches the threshold value at time t(i) within a predetermined period of time D(input) from the input start point t( 0 ) as shown in  FIG. 4A . A time interval e(i) between two hand claps adjacent to each other in time sequence represented by equation (11) shown in  FIG. 7  is detected.  
         [0065]     In the similar way as in the hand-clapping pattern registration, hand claps of the predetermined number N are detected. The detection of hand clapping ends when a mute period subsequent to the detection of last hand clap becomes longer than the predetermined time (D).  
         [0066]     In the similar way as in the hand-clapping pattern registration, an input error is triggered if no sound is picked up within a predetermined period of time D(start) from the input start point t( 0 ) or within a predetermined period of time D(input) from the input start point t( 0 ). The user is requested to hand his claps again, or a predetermined state resumes for example, a menu screen is displayed. If hand claps last to sound even after the predetermined period of time D(input) from the input start point t( 0 ), an input error is also triggered.  
         [0067]     If no input error is triggered, an overall length of time for picking up the hand claps e(sum), namely, a period of time from time t( 1 ) to time(n) is calculated using equation (12) of  FIG. 7 . As represented by equation (13) of  FIG. 7 , the time interval e(i) is divided by the overall length of time e(sum) to result in normalized time interval e′(i). Herein, i of the normalized time interval e′(i) ranges from 2 to n.  
         [0068]     During user identification, the following steps are performed in the following order to identify each user. As shown in  FIG. 5 , the CPU  11  searches for, as an identified user candidate, a user having a predetermined number of hand claps matching the number of hand claps detected in the user identification from a table of the hand-clapping pattern registered in the non-volatile memory  45 . As listed in the table of  FIG. 5 , if the number of hand claps detected in the user determination is “5”, “Takeshi” having the user ID U 2  and “Mami” having the user ID U 3  become user candidates for identification.  
         [0069]     For each user candidate found in the search, an error Cost represented in equation (14) of  FIG. 7  is calculated. An error having a minimum error Cost is identified as a user and the user ID of that user is detected. Herein, w 1  and w 2  in equation (14) of  FIG. 7  are predetermined weights.  
         [0070]     The setting and process of the content recording and playback apparatus  10  are switched in response to the user identified by the detected user ID.  
         [0071]      FIG. 8  illustrates the user identification process  60  performed by the CPU  11  in the content recording and playback apparatus  10 . In the user identification screen  60 , the CPU  11  starts the user identification process with a screen prompting the user to clap his hands as shown in  FIG. 9A  displayed on the display  34 . In step  61 , the CPU  11  determines whether an audio input is detected. If the CPU  11  determines that an audio input is detected, processing proceeds to step  62 . The CPU  11  processes the input audio signal to detect the hand-clapping pattern. The CPU  11  determines in step  63  whether any hand-clapping pattern matching the detected hand-clapping pattern is registered in the non-volatile memory  45 .  
         [0072]     The “hand-clapping pattern matching the detected hand-clapping pattern” refers to, from among the hand-clapping patterns registered in the non-volatile memory  45 , one hand-clapping pattern having the number of hand claps equal to the number of hand claps detected in step  62 , and providing a minimum error Cost represented in equation (14) of  FIG. 7 .  
         [0073]     The “hand-clapping pattern matching the detected hand-clapping pattern” in the above content may not be registered in the non-volatile memory  45 . More specifically, if none of the hand-clapping patterns registered in the non-volatile memory  45  matches the hand-clapping pattern detected in step  62  in terms of the number of hand claps, processing proceeds from step  63  to step  64  to perform an error process. Processing then returns to step  61 .  
         [0074]     The error process in step  64  is to prompt the user to clap his hands again.  
         [0075]     If the “hand-clapping pattern matching the detected hand-clapping pattern” in the above content is registered in the non-volatile memory  45 , processing proceeds from step  63  to step  65 . The CPU  11  calls user setting corresponding to the user ID having the matching hand-clapping pattern.  
         [0076]     For example, with the screen of  FIG. 9A  displayed on the display  34 , “Takeshi” claps his hands and the user is identified as “Takeshi”. In such a case, a screen configured for “Takeshi” is displayed as shown in  FIG. 9B . For example, with the screen of  FIG. 9A  displayed on the display  34 , “Mami” claps her hands and the user is identified as “Mami”. In such a case, a screen configured for “Mami” is displayed as shown in  FIG. 9C .  
       Second Embodiment  
       [0077]     As shown in  FIG. 1 , the content recording and playback apparatus  10 , including the entire user identification device  40 , is provided with all user identification functions. Part or whole of the user identification device and the user identification function can be transferred to a remote controller that controls a content recording and playback apparatus.  
         [0078]      FIG. 10  illustrates such a content recording and playback system. The content recording and playback system includes a content recording and playback apparatus  19  and a remote controller  70 . The remote controller  70 , including the microphone  41 , forms the user identification device  40 . The remote controller  70  performs the hand-clapping pattern registration process and the user identification process, and transmits a user ID identifying a user to the content recording and playback apparatus  19 .  
         [0079]     One of an infrared communication link, a wireless local area network (LAN), and a wired LAN is used for communications between the remote controller  70  and the content recording and playback apparatus  19 .  
         [0080]      FIG. 11  illustrates another recording and playback system. The recording and playback system includes the content recording and playback apparatus  19  and the remote controller  70 . The remote controller  70 , including the microphone  41 , transmits one of a digital audio signal and an analog audio signal responsive to a hand-clapping sound, generated by the user and picked up by the microphone  41 , to the content recording and playback apparatus  19 . The content recording and playback apparatus  19  performs the hand-clapping pattern registration process and the user identification process.  
         [0081]     One of infrared communication link, a wireless local area network, and a wired LAN is used for communications between the remote controller  70  and the content recording and playback apparatus  19  in the same way as in the system of  FIG. 10 .  
         [0082]      FIG. 12  illustrates another recording and playback system. As shown in  FIG. 10 , the remote controller  70 , including the user identification device  40 , performs the hand-clapping pattern registration process and the user identification process. A user ID identifying the user is transmitted to the content recording and playback apparatus  19  via a LAN  101 , an access point  100 , and a LAN  102 . The LAN&#39;s  101  and  102  are wireless LAN&#39;s or wired LAN&#39;s.  
         [0083]      FIGS. 13 and 14  respectively illustrate the remote controller  70  and the content recording and playback apparatus  19  in the system of  FIG. 10  with the infrared communication link used.  
         [0084]     The content recording and playback apparatus  19  of FIG.  13  includes a CPU  71 . A bus  72  of the CPU  71  connects to a ROM  73  storing a variety of programs and data, and a RAM  74  onto which the programs and data are expanded.  
         [0085]     The microphone  41  is connected to the bus  72  via the audio amplifier  42 , the A/D converter  43 , and the input and output port  44 . The non-volatile memory  45  is also connected to the bus  72 .  
         [0086]     The user identification device  40  includes the microphone  41 , the audio amplifier  42 , the A/D converter  43 , the input and output port  44 , the non-volatile memory  45 , the CPU  71 , the ROM  73 , and the RAM  74 .  
         [0087]     An operation unit  81  composed of a variety of keys is connected to the bus  72  via an interface  82 . A display  84 , such as a liquid-crystal display, is connected to the bus  72  via an interface  83 . A loudspeaker  88  is connected to the bus  72  via an input and output port  85 , a D/A converter  86  and an audio amplifier  87 .  
         [0088]     An operation screen and a setting screen are displayed on the display  84 . An audio announcement is output from the loudspeaker  88 .  
         [0089]     An infrared light emission unit  93  is connected to the bus  72  via an input and output port  91  and a transmitter circuit  92 .  
         [0090]     The infrared light emission unit  93  transmits, as infrared light signals, a user ID identifying the user as described below, and a variety of remote control signals.  
         [0091]     The content recording and playback apparatus  19  of  FIG. 14  is different from the content recording and playback apparatus  10  of  FIG. 1  in that the content recording and playback apparatus  19  is without the microphone  41 . Instead, the content recording and playback apparatus  19  includes an infrared light receiving unit  28  connected to the bus  12  via an input and output port  26  and a receiver circuit  27 . The remaining portion of the content recording and playback apparatus  19  is identical to the content recording and playback apparatus  10 .  
         [0092]     An infrared signal transmitted from the infrared light emission device  93  in the remote controller  70  of  FIG. 13  is transmitted and then received by the infrared light receiving unit  28 . The received infrared signal is then transferred to the bus  12  as a remote control signal.  
         [0093]     The hand-clapping pattern registration process of the remote controller  70  of  FIG. 13  is identical to the hand-clapping pattern of the content recording and playback apparatus  10  of  FIG. 1 . More specifically, each user claps beforehand his hands in a pattern unique to the user. The hand-clapping pattern is then stored in the non-volatile memory  45  in the remote controller  70  with the name of the user and the user ID associated therewith.  
         [0094]     In the hand-clapping pattern registration process  50  of  FIG. 6 , the hand clapping request in step  52  and the registration acceptance confirmation in step  55  are performed when the display  84  of the remote controller  70  displays the message and when the loudspeaker  88  outputs one of the audio announcement and the drum sound.  
         [0095]     The system can be modified so that the display  34  and the loudspeaker  38  in the content recording and playback apparatus  19  performs respectively the message displaying and the audio outputting to request hand clapping and registration confirmation in response to commands from the remote controller  70 .  
         [0096]     The user identification process subsequent the hand-clapping pattern registration is identical to the user identification of the content recording and playback apparatus  10  of  FIG. 1  except that the user ID identifying the user is transmitted from the remote controller  70  to the content recording and playback apparatus  19 .  
         [0097]      FIG. 15  illustrates the user identification process  110  performed by the CPU  71  of the remote controller  70 . In the user identification process  110 , the CPU  71  starts the user identification operation with a screen prompting the user to clap his hands displayed on the display  84 . In step  111 , the CPU  71  determines whether an audio input is detected. If the CPU  71  determines that an audio input is detected, processing proceeds to step  112 . The CPU  71  determines whether any hand-clapping pattern matching the detected in step  113  hand-clapping pattern is registered in the non-volatile memory  45 .  
         [0098]     The meaning of the “hand-clapping pattern matching the detected hand-clapping pattern” has been previously discussed. The “hand-clapping pattern matching the detected hand-clapping pattern” may not be registered in the non-volatile memory  45 . More specifically, if none of the hand-clapping patterns registered in the non-volatile memory  45  matches the hand-clapping pattern detected in step  112  in terms of the number of hand claps, processing proceeds from step  113  to step  114  to perform an error process. After performing the error process, processing then returns to step  111 .  
         [0099]     If the “hand-clapping pattern matching the detected hand-clapping pattern” is registered in the non-volatile memory  45 , processing proceeds from step  113  to step  115 . The CPU  71  calls user setting corresponding to the user ID having the matching hand-clapping pattern. The user ID is then transmitted to the content recording and playback apparatus  19  via the transmitter circuit  92  and the infrared light emission device  93 .  
         [0100]     The content recording and playback apparatus  19  receive the user ID with the infrared light receiving unit  28  and the receiver circuit  27  and calls the user setting corresponding to the user ID.  
         [0101]     The system can be modified so that the request to prompt the user to clap his hands is performed by one of the display  34  and the loudspeaker  38  in the content recording and playback apparatus  19  in response to a command from the remote controller  70 .  
       Third Embodiment  
       [0102]     In accordance with a third embodiment of the present invention, the hand-clapping pattern registration process and the user identification process are performed by an application program of a personal computer rather than by the hardware structure and the software structure of the remote controller.  
         [0103]      FIG. 16  illustrates such a system. In this system, a personal computer  120  is connected to the content recording and playback apparatus  19  via a LAN  155 . The LAN  155  is one of a wireless LAN and a wired LAN.  
         [0104]     The personal computer  120  is one of widely available personal computers except that the personal computer  120  is loaded with application programs for the hand-clapping pattern registration process and the user identification process.  
         [0105]     The personal computer  120  includes a CPU  121 . A bus  122  of the CPU  121  connects to a memory  123 . A hard disk  125  is connected to the bus  122  via an input and output port  126 . A recording medium  127  is connected to the bus  122  via an input and output port  128 .  
         [0106]     An operation unit  131 , composed of a keyboard and a pointing device, is connected to the bus  122  via an interface  132 . A display  134 , such as a liquid-crystal display, is connected to the bus  122  via an interface  133 . A loudspeaker  138  is connected to the bus  122  via an input and output port  135 , a D/A converter  136 , and an audio amplifier  137 . A microphone  141  is connected to the bus  122  via an audio amplifier  142 , an A/D converter  143 , and an input and output port  144 .  
         [0107]     The microphone  141 , the audio amplifier  142 , the A/D converter  143 , and the input and output port  144  are general-purpose audio input elements rather than elements that are particularly arranged to form a user identification device, and are used to perform the hand-clapping pattern registration process and the user identification process.  
         [0108]     An external interface  151  for connection with the Internet  1  and a LAN communication unit  153  are connected to the bus  122 . The LAN communication unit  153  is connected to the content recording and playback apparatus  19  via a LAN  155 . A single interface can be shared by the external interface  151  and the LAN communication unit  153 .  
         [0109]     The content recording and playback apparatus  19  is connected to the LAN communication unit  153 , which replaces the input and output port  26 , the receiver circuit  27 , and the infrared light receiving unit  28  shown in  FIG. 14 .  
         [0110]     The application program of the personal computer  120  performing the hand-clapping pattern registration process and the user identification process is stored in the hard disk  125 , and expanded onto the memory  123  during the hand-clapping pattern registration and the user identification.  
         [0111]     The hand-clapping pattern registration process of the application program of the personal computer  120  is identical to each of the hand-clapping pattern registration process of the content recording and playback apparatus  10  of  FIG. 1 , and the hand-clapping pattern registration process of the remote controller  70  of  FIG. 13 . The hand-clapping pattern registration process of the personal computer  120  is thus shown as the hand-clapping pattern registration process  50  in  FIG. 6 .  
         [0112]     The table of  FIG. 5  that associates the hand-clapping pattern of each user with the user name and the user ID is generated on the memory  123  during the registration process, and is then stored on the hard disk  125 .  
         [0113]     The user identification process of the application program of the personal computer  120  is identical to user identification program of the remote controller  70  of  FIG. 13 , and is thus shown as the user identification process  110  in  FIG. 15 .  
         [0114]     In the system, the user ID having the matching hand-clapping pattern is transmitted from the LAN communication unit  153  in the personal computer  120  to the content recording and playback apparatus  19 . The content recording and playback apparatus  19  calls the user setting corresponding to the user ID.  
       Other Embodiments  
       [0115]     In the above-referenced embodiments, the user claps his hands successively several times. Alternatively, the user may claps his hands one time only.  FIGS. 17A and 17B  illustrates a hand-clapping pattern of a single hand clapping.  
         [0116]     In the single hand-clapping sound, one of Fast Fourier Transform (FFT) technique and wavelet transform technique is used to perform pattern matching between a registered hand-clapping pattern and a hand-clapping pattern detected during the user identification.  
         [0117]     The single hand-clapping pattern varies in amplitude from pattern to pattern, and is lower in recognition accuracy than the multi hand-clapping pattern. However, the single hand-clapping pattern can identify the user within a short period of time.  
         [0118]     Instate of hand clapping, the user can tap one of a bell arranged close to the apparatus and the edge of the apparatus.  
         [0119]     One of the electronic apparatus identifying the user and the electronic apparatus to which the user ID of the user identified by the remote controller or the personal computer is transmitted may be a recording and playback apparatus. Alternatively, the electronic apparatus can be one of an air-conditioning apparatus, a robot, an illumination apparatus, a television receiver, and a personal computer.  
         [0120]     For example, in the air-conditioning apparatus, the air-conditioning state is automatically shifted to a predetermined setting adapted to a particular user. In the case of the robot, the movement of the robot is automatically set to a predetermined setting adapted to a particular user. In the illumination apparatus, the illumination state is automatically switched to a predetermined setting adapted to a particular user. In the television receiver, the volume control level of a receiving channel is automatically shifted in response to one of the channel and state adapted to a particular user.  
         [0121]     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
A method of identifying a user, includes steps of registering, in a memory, clapping patterns of clapping of a plurality of users with a user identification for identifying each user associated with a respective clapping pattern, picking up the sound of claps to acquire an input audio signal responsive to the clapping sound, processing the acquired input audio signal to detect a clapping pattern, and comparing the detected clapping pattern with the registered clapping pattern to determine whether any of the clapping patterns registered in the memory matches the detected clapping pattern and in the event of the presence of one of the registered clapping patterns matching the detected hand pattern, identifying the user by the user identification, registered in the memory, associated with the matching clapping pattern.