Abstract:
A radio communication apparatus having a videophone function and a usual phone function, according to the present invention, incorporates a camera for inputting an image to realize the videophone function, and an encoding section for encoding an image signal output from the camera. It also incorporates a decoding section for decoding a received image signal input via a radio section and displaying it on a display screen section. A controller limits the encoding of the image signal in the encoding section, when necessary, in order to limit the consumption of power, and also limits the decoding of the image signal in the decoding section. Thus, the invention provides a radio communication apparatus with a videophone function, capable of encoding and displaying, only when necessary during a videophone call, an image signal transmitted from another radio communication apparatus, thereby minimizing the consumption of power per unit of time.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-204101, filed Jul. 5, 2000, 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 radio communication apparatus having a videophone function for enabling videophone communication, and more particularly to the control processing for transmitting and receiving image data.  
           [0004]    2. Description of the Related Art  
           [0005]    In the field of a radio communication apparatus equipped with an image display such as a liquid crystal display, a radio communication apparatus having a videophone function for displaying not only still images such as characters or still pictures, etc., but also moving video images or moving pictures, etc., i.e. a so-called videophone, has been recently developed and come onto the market.  
           [0006]    When the radio communication apparatus having the videophone function executes videophone communication, an image transmitted from a person called is continuously displayed until the call finishes, even if the image does not have to be displayed for users. While such an image is being displayed, the circuits for decoding and displaying a received image signal have to be kept operating. The videophone communication in which the circuits for decoding and displaying the received image signal are kept operating consumes much more power than communication using only sound.  
           [0007]    In particular, when a radio communication apparatus using an isolated power section such as a battery executes a videophone call, the heavy consumption of power is a serious problem. Since the radio communication apparatuses use a battery as a power supply, its maximum call period and standby period may be very short.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    It is an object of the present invention to provide a radio communication apparatus having a videophone function and capable of decoding and displaying an image signal transmitted from a person called only when necessary during videophone communication, thereby reducing the consumption of power per unit of time.  
           [0009]    It is another object of the present invention to provide a radio communication apparatus having a videophone function and capable of stopping decoding a received image signal when a still image has been created by key operation.  
           [0010]    It is yet another object of the present invention to provide a compact radio communication apparatus having a videophone function and capable of controlling a received image signal decoding section so as to decode the signal within a necessary range, and stopping the received image signal decoding section during a usual signal receiving operation, thereby minimizing the amount of heat generated from the radio communication apparatus.  
           [0011]    According to a first aspect of the present invention, there is provided a radio communication apparatus comprising:  
           [0012]    receiving section configured to receive a radio signal containing a voice signal and an image signal and demodulate the voice signal and the image signal;  
           [0013]    converting section configured to receive the demodulated image signal from the receiving section and decode the demodulated image signal; and  
           [0014]    control section configured to stop decoding the demodulated image signal that is supplied from the receiving section to the converting section during communication.  
           [0015]    According to a second aspect of the invention, there is provided a radio communication apparatus comprising:  
           [0016]    receiving section configured to receive a radio signal containing a voice signal and an image signal and demodulate the voice signal and the image signal;  
           [0017]    converting section configured to receive the demodulated image signal from the receiving section and decode the demodulated image signal;  
           [0018]    control section configured to turn on and off the converting section so as to stop decoding the demodulated image signal that is supplied from the receiving section to the conversion section during communication;  
           [0019]    timer section configured to measure a predetermined period of time for which the image signal is output to the converting section, if the image signal is a moving picture signal; and  
           [0020]    memory section configured to store the image signal decoded by the converting section and prestore an image signal obtained beforehand.  
           [0021]    According to a third aspect of the invention, there is provided a radio communication apparatus comprising:  
           [0022]    receiving section configured to receive a radio signal containing a voice signal and an image signal and demodulate the voice signal and the image signal;  
           [0023]    converting section configured to receive the demodulated image signal from the receiving section and decode the demodulated image signal;  
           [0024]    control section configured to turn on and off the conversion section so as to stop decoding the demodulated image signal that is supplied from the receiving section to the converting section during communication; and  
           [0025]    memory section configured to store the image signal decoded by the converting section and prestore an image signal obtained beforehand.  
           [0026]    Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0027]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0028]    [0028]FIG. 1 is a conceptual view illustrating a system including radio communication apparatuses according to a first embodiment of the present invention;  
         [0029]    [0029]FIG. 2 is a block diagram illustrating the internal electrical structure of each radio communication apparatus of FIG. 1;  
         [0030]    [0030]FIG. 3 is a flowchart useful in explaining the operation of each of the radio communication apparatus described the first embodiment and a radio communication apparatuses according to a second embodiment, which is executed to decode and display an image signal received for a predetermined time period after the start of videophone communication, and to display an image stored in the apparatus after the predetermined time period elapses;  
         [0031]    [0031]FIG. 4 is a flowchart for illustrating in detail the process executed at step ST 6  shown in FIG. 3; and  
         [0032]    [0032]FIG. 5 is a flowchart useful in explaining the operation of a radio communication apparatus according to a third embodiment of the invention, which is executed to decode and display, during videophone communication, an image signal received as long as key input operation is executed for requesting the display of the image signal, and to display an image stored in the apparatus if there is no such key input operation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]    Radio communication apparatuses according to the embodiments of the present invention will be described with reference to the accompanying drawings.  
         [0034]    FIGS.  1 - 3  show radio communication apparatuses with a videophone function according to a first embodiment. FIG. 1 shows a communication system including the radio communication apparatuses with the videophone functions according to the first embodiment. As is seen from FIG. 1, radio communication apparatuses  50  and  51  having the videophone function are connected to a public network  54  via base stations  52  and  53 , respectively. The base stations  52  and  53  respectively provide the radio communication apparatuses  50  and  51  with respective service areas dedicated to the base stations  52  and  53 . In other words, the base station that is located closest to each radio communication apparatus  50  or  51  and hence can receive the radio waves of each radio communication apparatus in a best condition is designated as the base station  52  or  53 . The public network  54  is connected to a plurality of base stations located in various areas, and can communicate with a radio communication apparatus located even at a long distance via an appropriate base station.  
         [0035]    [0035]FIG. 2 is a block diagram illustrating the internal structure of each radio communication apparatus  50  or  51  with the videophone function according to the invention.  
         [0036]    As shown in FIG. 2, each of the radio communication apparatuses  50  and  51  has a radio section  2  for transmitting and receiving radio waves to and from a corresponding one of the base stations  52  and  53 . The radio section  2  is connected to an antenna  1  and receives radio waves through the antenna  1 . The antenna  1  converts a received radio wave into a received signal. The radio section  2  subjects the received signal to high frequency amplification and frequency conversion, thereby amplifying low noise contained in the signal. A controller  5  generates a designation signal for designating a frequency and supplies the designation signal to the radio section  2 . On the basis of the designation signal, the radio section  2  converts the received signal, by frequency conversion, into an intermediate-frequency signal or a baseband signal, and demodulates the converted signal into a digital signal.  
         [0037]    The controller  5  executes control for establishing a communication channel based on a communication protocol. Upon establishing the communication channel, the controller  5  generates a call sound generating signal. A sounder (not shown) outputs the call sound generating signal, thereby informing the user of an incoming call. The user can also be notified about the incoming call by vibrating a vibrator (not shown) or turning on an LED (not shown), instead of generating the call sound.  
         [0038]    A call control section (not shown) receives the received signal from the radio section  2  over the communication channel. When, after that, a prescribed key in a key section  14  has been pushed to establish communication, the call control section converts the demodulated signal into a speaker signal. A speaker section  12  receives the speaker signal and outputs a sound corresponding to the speaker signal.  
         [0039]    When the apparatus transmits radio waves containing voice information through the antenna  1 , the operation of the key section  14  incorporated in each radio communication apparatus  50  or  51  generates an ON signal for turning on the apparatus called ( 50  or  51 ). The controller  5  receives the ON signal and turns on the corresponding apparatus ( 50  or  51 ). After that, a phone number assigned to another radio communication apparatus to communicate with is input by operating the key section  14 , thereby generating a number signal corresponding to the phone number. The controller  5  receives the number signal and creates a radio control signal based on the number signal. The radio section  2  receives the radio control signal and encodes the phone number. Radio waves containing the encoded phone number are output through the antenna  1 . When the apparatus transmits a signal, the controller  5  controls the communication protocol to establish a communication channel. After that, incoming call radio waves are transmitted to the radio communication apparatus with the phone number via the base station  52 , the public network  54  and the base station  53 . In this state, the radio communication apparatuses  50  and  51  are communicable. In the communicable state, a voice input to a microphone  13  is converted into a voice signal and input to a call control section (not shown), where the input signal is digitally modulated.  
         [0040]    At the time of receiving image data, at first, the communication channel is established as described above. The controller  5  detects a received signal. If the received signal contains the image data, the controller  5  establishes an interface for processing image data. Upon establishing the interface, the controller  5  outputs a digital signal containing the image data to a received-image-signal decoding section  8  via a decoding switch  6 . The decoding switch  6  controls the output of an image signal from the controller  5  to the received-image-signal decoding section  8 . Specifically, if the decoding switch  6  is in the ON state, the output of the image signal to the received-image-signal decoding section  8  is permitted, while if the decoding switch  6  is in the OFF state, the output of the image signal to the section  8  is interrupted. This means that the decoding switch  6  has a function of interrupting the decoding of the image signal in the received-image-signal decoding section  8 . That is, if the decoding switch  6  is in the ON state, the received signal is decoded by the received-image-signal decoding section  8 , and if it is turned off, the decoding of the received signal by the section  8  is interrupted.  
         [0041]    The received-image-signal decoding section  8  decodes the image signal and then subjects the decoded image signal to D/A conversion, thereby converting the decoded image signal into an analog image signal. A display screen section  11  receives the analog image signal and displays an image based on the image data contained in the analog image signal.  
         [0042]    When the apparatus transmits image data, a camera  10  picks up an image and converts the image into an image signal. In place of the camera  10 , the image signal may be input to the apparatus via an image input terminal connected to an image input device such as a video recorder. A transmission image signal encoding section  9  encodes the image signal and converts the encoded image signal into a digital image signal containing the image data. The resultant signal is output to the controller  5  under the control of an encoding switch  7 . If the encoding switch  7  is in the ON state, the encoding of the image signal by the transmission image signal encoding section  9  is continued, and the output of the image signal to the controller  5  is permitted. On the other hand, if the encoding switch  7  is turned off, the encoding of the image signal by the section  9  and the output of the image signal to the controller  5  are both interrupted. The radio section  2  modulates the image signal and transmits the modulated image signal from the antenna  1 . On transmission, the communication channel is established as aforementioned. As aforementioned, the encoding switch  7  controls the transmission image signal encoding section  9 , by on or off switching, so as to reduce the power consumption of the section  9 .  
         [0043]    Each radio communication apparatus  50  or  51  includes a memory  4  for storing phone numbers, an incoming call history, image data and voice data, etc. Further, each radio communication apparatus  50  or  51  also includes a timer  3  for monitoring the time period for displaying a received image during the execution of the videophone function. An image signal received for a predetermined time period after the start of a call is decoded and the image corresponding to the decoded image signal is displayed on the display screen section  11 . After the predetermined time period elapses, an image stored in the memory  4  is displayed on the display screen section  11 . The image stored in the memory  4  can be selected, by the user&#39;s operation of the key section  14 , from image data transmitted, during the call, from the radio communication apparatus called. Further, any voluntarily selected images may be stored in the memory  4  beforehand and displayed when necessary. An image previously stored in the memory  4  may be displayed. Also, an image received from an image forming apparatus, such as a video recorder, a digital camera or a personal computer, connected to the input terminal (not shown) of the radio communication apparatus may be displayed. Moreover, the radio communication apparatus may be programmed such that if the key section  14  is operated during the call to request the display of an image signal that is now being received, the received image signal is decoded and displayed, while if the key section  14  is not operated, an image stored in the radio communication apparatus is displayed. Thus, the image to be displayed can be voluntarily selected by the user&#39;s operation of the key section  14 .  
         [0044]    Referring now to the flowchart of FIG. 3, a description will be given, which is the operation of decoding and displaying, under the control of the controller  5 , an image signal received for a predetermined time period after the start of the execution of the videophone function, and displaying an image stored in the radio communication apparatus after the predetermined period elapses.  
         [0045]    First, when the radio communication apparatus  50  or  51  is waiting for to-be-received radio waves, the time period for displaying an image received during a videophone call is set in the timer  3  shown in FIG. 2, using the key section  14  shown in FIG. 2 (step ST 1  in FIG. 3). Subsequently, the key section  14  is operated to input a phone number into the radio communication apparatus  50  or  51 . As a result, a videophone call origination is generated (step ST 2  in FIG. 3). Then, the radio communication apparatus  50  or  51  waits for a response from the radio communication apparatus called (step ST 3  in FIG. 3).  
         [0046]    When starting communication between apparatuses, the switches  6  and  7  shown in FIG. 2 are turned on, thereby operating the received-image-signal decoding section  8  and the transmission image signal encoding section  9 . As a result, videophone communication for transmitting and receiving image and voice signals starts (step ST 4  in FIG. 3). After that, the timer  3  shown in FIG. 2 is operated to monitor the predetermined time period for displaying the image signal received during the execution of the videophone function (step ST 5  in FIG. 3).  
         [0047]    A still image is extracted from the received image signal and stored in the memory  4  shown in FIG. 2, under the control of the controller  5  (step ST 6  in FIG. 3). Subsequently, it is determined whether or not the predetermined time period for displaying a received image during the videophone call has elapsed (step ST 7  in FIG. 3). The predetermined time was set while the radio communication apparatus was in the standby state. After the predetermined time period elapses, the switch  6  shown in FIG. 2 is turned off to thereby stop the operation of the received-image-signal decoding section  8  (step ST 8  in FIG. 3). At this time, a still image extracted from the received image stored in the memory  4  shown in FIG. 2 is displayed on the display screen section  11  (step ST 9  in FIG. 3).  
         [0048]    After a still image is displayed by operating the radio communication apparatus  50  or  51  as described above, the current consumption of the received-image-signal decoding section  8  is reduced, thereby minimizing a reduction in the capacity of the battery due to the decoding of the received image signal. Furthermore, since a still image is displayed while image decoding is being stopped, the user does not have to worry about whether or not the decoding function is a breakdown when the image decoding is stopped. It is sufficient if the to-be-displayed image is any one of the images stored in the radio communication apparatus, and is not necessarily an image extracted from a received image signal. For example, a prestored picture of a person to communicate with may be displayed, using an address book function. Alternatively, a particular icon or a message indicating that a videophone call is now being executed may be displayed, or an illustration preselected by the user may be displayed. Thus, the to-be-displayed image can be voluntarily selected and is not limited to the above.  
         [0049]    Referring then to FIGS. 3 and 4, a second embodiment of the invention will be described. FIG. 4 is a flowchart useful in explaining in detail the step ST 6  shown in FIG. 3.  
         [0050]    A description of a method, employed in the step ST 6  of FIG. 3, for creating a still image from a received image signal will be given. There is a method for creating a still image from a received image signal at random. However, in this method, it is possible that a desired image will not be obtained. For example, a still image may be extracted when the face of a person called is offscreen. In this case, the face of a person is not included in the still image.  
         [0051]    To avoid such a case, there is a method for enabling the user to create a desired still image. This method is illustrated in FIG. 4.  
         [0052]    In the flowchart of FIG. 4, at first, a received image signal is decoded (step ST 1  in FIG. 4), and a standby state for waiting for a key input operation to request the creation of a still image is maintained (step ST 2  in FIG. 4). In this standby state, if the key input operation is detected, a still image is created. Accordingly, it become rare that when the face of a person called is offscreen, a still image on the screen is extracted (step ST 3  in FIG. 4). Further, the timer  3  for monitoring the time period for displaying a receiving image signal during a videophone call may be set to stop its time measuring when the key for requesting a still image has been pushed, so as to stop the decoding of the receiving image signal when a still image has been created as a result of the key input operation.  
         [0053]    The above embodiment can be modified so that transmission of image data to a radio communication apparatus as a destination is stopped, in addition to the stoppage of the decoding of the received image signal, after the predetermined time period for displaying a received image signal during a videophone call elapses. Specifically, the transmission of an image signal can be also stopped by turning off, at the step ST 9  in FIG. 3, the encoding switch  7  for controlling the operation of the transmission image signal encoding section  9  shown in FIG. 2. As a result, the radio communication apparatus as the destination can further reduce its current consumption, although the apparatus shows no images on the screen. Further, if the radio communication apparatus as the destination employs a memory as described above, it can display a still image stored in the memory  4 .  
         [0054]    Referring to FIG. 5, a third embodiment of the present invention will be described. FIG. 5 is a flowchart useful in explaining the operation of decoding and displaying a received image signal only while the key input operation of requesting display of a received image signal is being executed during a videophone call, and displaying an image stored in the apparatus if there is no key input operation.  
         [0055]    First, when the radio communication apparatus  50  or  51  is waiting for to-be-received radio waves, a phone number is input to generate a videophone call origination (step ST 1  in FIG. 5). Then, the radio communication apparatus  50  or  51  waits for a response to the call from a radio communication apparatus as a destination (step ST 2  in FIG. 5). When starting communication, the switch  7  shown in FIG. 2 is turned on, thereby operating the transmission image signal encoding section  9 . As a result, an image is transmitted to the radio communication apparatus as the destination and videophone communication starts (step ST 3  in FIG. 5). Further, an image stored in the apparatus is displayed on the display screen section  11  shown in FIG. 2 (step ST 4  in FIG. 5). In this state, the key input operation for requesting display of a receiving image is waited for (step ST 5  in FIG. 5).  
         [0056]    When the key input operation has been executed, the switch  6  shown in FIG. 2 is turned on, thereby operating the received-image-signal decoding section  8 , thereby decoding a signal received and displaying an image of the decoded signal on the display screen section  11  (step ST 6  in FIG. 5). After that, termination of the key input operation of requesting the display of a received image is waited for (step ST 7  in FIG. 5). After the key input operation is terminated, the switch  6  is turned off to stop the received-image-signal decoding section  8 , followed by the program returning to the step ST 4  (step ST 8  in FIG. 5).  
         [0057]    The above-described operations enable a received image to be displayed only when a request for displaying the received image has been issued, and enable the received-image-signal decoding section  8  to be stopped if there is no such request. Accordingly, when there is no such request, the received-image-signal decoding section  8  does not consume power, and hence less power is consumed from the battery of the radio communication apparatus  50  or  51 . Furthermore, when no received image is displayed, an image stored in the apparatus is displayed. Accordingly, the user does not have to worry about whether or not the decoding function is a breakdown when the image decoding is stopped.  
         [0058]    This embodiment can be also modified such that an image can be displayed for a predetermined time period after a key input operation is executed. If the above-described two methods are combined, the current consumption of the radio communication apparatus can be further reduced.  
         [0059]    The present invention can be modified in various ways without deviation from the gist. For example, the invention may be modified such that the manner of communication can be switched between videophone communication and usual phone communication using only sound by pushing one key repeatedly.  
         [0060]    As described above, in the embodiments, a circuit for decoding a received image signal is operated when necessary during a videophone call, thereby decoding and displaying the received image signal. When the circuit is not operated, it does not consume power. Accordingly, the power consumption of the entire apparatus is less than that of an apparatus in which a received image signal is always decoded and displayed.  
         [0061]    If this structure is employed in a radio communication apparatus to be operated by a battery, such as a mobile phone, the power consumption of the battery can be suppressed since a received image is displayed only for a necessary period during a videophone call. This means that the duration of a call and the duration of standby obtained by one battery charge can be lengthened.  
         [0062]    Moreover, since image decoding is not executed more than necessary and hence the operation of the circuit for decoding images is minimized, the heat generated from the radio communication apparatus can be reduced and the apparatus can be made compact.  
         [0063]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.