Patent Publication Number: US-2010118180-A1

Title: Imaging device

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese patent application serial No. JP 2008-288907, filed on Nov. 11, 2008, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to an imaging device that takes a motion picture and uploads it to a Web server through the Internet. 
     (2) Description of the Related Art 
     In recent years, social networking services (hereinafter referred to as SNSs), Web logs (hereinafter referred to as blogs), and other similar services are widespread and available for users to post their diaries and movie content on the Internet. These services enable the users to easily post their content by entering text, motion pictures, and other content into a dedicated form on a Web browser and uploading such content to a Web server. Similarly, movie-sharing websites and other similar services are also widespread and available for the users to share motion pictures on the Web. These services make it possible to upload movie content to a server with a dedicated form on a Web browser or movie file upload software, and allow a large indefinite number of users to share the uploaded movie content. 
     To use movie content on the Web, it is first necessary to take a motion picture of a subject, for instance, with a digital still camera or video camera. To upload the obtained movie content to a Web server, it is necessary to copy the content from the camera to a PC (Personal Computer) or other device connectable to the Internet, and then upload the content from the PC or the like. To provide the users with increased convenience and labor savings, however, the users should be allowed to upload the content, which is imaged by the digital still camera or video camera, directly to a Web server without having to copy the content to the PC or the like beforehand. The following has been proposed as a communication procedure used when an image is transmitted from an imaging device having a wireless communication function directly to a server or the like. 
     The communication procedure disclosed in JP-A-2004-289619 is to be performed when a user traveling on a train or other vehicle intends to transmit a print order from a digital camera having a wireless communication function to a photo print shop&#39;s server. This procedure includes the steps of receiving service information via a communication link, cutting off the communication, generating order information, and transmitting the order information and image data when the user reaches a communicatable area. The disclosure also indicates that the digital camera includes detection means for detecting whether the digital camera is located within a communicatable area, switches to a power saving mode when the detection means starts a detection operation, and stays in the power saving mode while the detection means is performing the detection operation. 
     Disclosed in JP-A-2006-197214 is a digital camera that is used in combination with a separate communication adapter having communication means. As far as removable recording means for storing shot images is connected to the communication adapter and used to transmit stored images to a server, the digital camera can perform an imaging operation even when the communication adapter is communicating with the server. The disclosure also indicates that the communication adapter checks for a command file on the server after completion of image transmission and switches to a power saving mode if no command file is found. 
     SUMMARY OF THE INVENTION 
     The use of the technologies described in JPA-2004-289619 and JP-A-2006-197214 makes it possible to transmit a shot image from a camera or other imaging device to a desired server via a wireless LAN. Further, the devices disclosed in the above patent documents provide the communication means with a power saving mode to reduce the power consumption of the communication means. 
     However, the inventions disclosed in JP-A-2004-289619 and JP-A-2006-197214 assume that a still picture shot by a digital camera is transmitted to a server. When movie content, especially a motion picture shot at a full high definition 1920×1080 resolution, is transmitted to a server, an inadequate power saving effect is produced to cause a new problem. The reason is that it takes a long time to upload movie content as the file size of a motion picture is tremendously larger than that of a still picture. Therefore, the upload of a motion picture involves large power consumption, thereby imposing a great burden on a video camera which is battery-driven in most cases. 
     Further, if a transmission operation for uploading a motion picture file is interrupted due to power insufficiency, the transmitted file turns out to be incomplete. In such an instance, a third person may fail to download the file from the server and view it normally. 
     An object of the present invention is to provide an imaging device that reduces its power consumption and prevents an upload failure due to power insufficiency when it uploads movie content. 
     According to one aspect of the present invention, there is provided an imaging device for shooting a subject to generate picture content and transmitting the picture content to an external device, the imaging device including an imaging unit, a content storage unit, a display section, a communication module section, a power supply identification section, and a power saving mode setup section. The imaging unit shoots the subject and converts the obtained subject image to a video signal. The content storage unit stores the video signal as picture content in encoded stream format. The display section playbacks and displays the picture content. The communication module section transmits the picture content to the external device through the Internet. The power supply identification section determines whether a drive power supply is a battery or an AC power supply. The power saving mode setup section places the imaging device in a power saving mode to shut off the power supply to the communication module section when a battery is employed as the drive power supply. 
     According to another aspect of the present invention, there is provided an imaging device for shooting a subject to generate picture content and transmitting the picture content to an external device, the imaging device including an imaging unit, a content storage unit, a display section, a communication module section, a power supply identification section, and a remaining battery power value acquisition section. The imaging unit shoots the subject and converts the obtained subject image to a video signal. The content storage unit stores the video signal as picture content in encoded stream format. The display section playbacks and displays the picture content. The communication module section transmits the picture content to the external device through the Internet. The power supply identification section determines whether a drive power supply is a battery or an AC power supply. The remaining battery power value acquisition section acquires a current remaining battery power value P to compare it against a predetermined value P 0  when a battery is employed as the drive power supply. When the current remaining battery power value P is less than the predetermined value P 0 , the picture content transmission operation by the communication module section is interrupted. 
     According to another aspect of the present invention, there is provided the imaging device, further including an interruption information storage section which stores the information about an interruption point of content to be interrupted when the transmission operation by the communication module section is to be interrupted. 
     According to another aspect of the present invention, there is provided the imaging device, wherein, when the information about interrupted content is stored in the interruption information storage section, the display section indicates the presence of the interrupted content; and wherein the communication module section resumes the transmission of the interrupted content from the interruption point. 
     According to still another aspect of the present invention, there is provided an imaging device for shooting a subject to generate picture content and transmitting the picture content to an external device, the imaging device including an imaging unit, a content storage unit, a display section, a communication module section, a power supply identification section, and a remaining battery power value prediction section. The imaging unit shoots the subject and converts the obtained subject image to a video signal. The content storage unit stores the video signal as picture content in encoded stream format. The display section playbacks and displays the picture content. The communication module section transmits the picture content to the external device through the Internet. The power supply identification section determines whether a drive power supply is a battery or an AC power supply. When a battery is employed as the drive power supply, the remaining battery power value prediction section predicts a remaining battery power value P′ prevailing upon completion of the picture content transmission and compares the predicted remaining battery power value P′ against a predetermined value P 0  before the beginning of picture content transmission. When the predicted remaining battery power value P′ is less than the predetermined value P 0 , the display section displays information indicating that the remaining battery power is not sufficient for transmission completion. 
     When shot movie content is to be uploaded to a Web server, the present invention makes it possible to reduce the power consumption and prevent an upload failure due to power insufficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features, objects, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a diagram illustrating the configuration of an exemplary content transmission system that uses an imaging device according to the present invention; 
         FIG. 2  is a diagram illustrating the configuration of an imaging device according to an embodiment of the present invention; 
         FIG. 3  is a flowchart illustrating a content upload process according to a first embodiment of the present invention; 
         FIG. 4  shows an example of a screen for selecting the file to be uploaded as indicated in  FIG. 3 ; 
         FIG. 5  shows an example of a warning screen to be opened in step S 310  of  FIG. 3 ; 
         FIG. 6  is a flowchart illustrating an upload process according to a second embodiment of the present invention; 
         FIG. 7  is a flowchart illustrating an upload interruption process which is performed in step S 608  of  FIG. 6 ; 
         FIG. 8  shows an example of an upload start screen, which opens as indicated in  FIG. 6 ; 
         FIG. 9  shows an example of an upload interruption screen which opens as indicated in  FIG. 7 ; 
         FIG. 10  is a flowchart illustrating an upload process according to a third embodiment of the present invention; 
         FIG. 11  shows an example of a warning screen which opens in step S 1004  of  FIG. 10 ; 
         FIG. 12  is a flowchart illustrating an upload resumption process according to a fourth embodiment of the present invention; and 
         FIG. 13  shows an example of an upload resumption screen which opens as indicated in  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will now be described with reference to the accompanying drawings. 
       FIG. 1  is a diagram illustrating the configuration of an exemplary content transmission system that uses an imaging device according to the present invention. The system includes an imaging device  100  having a communication function, the Internet  103 , a Web server  104 , and an external device. 
     A user (movie shooter)  110  shoots a subject with the imaging device  100 . The shot movie is subjected as needed to content processing. A communication function is exercised to upload the processed content data  105  to a Web server  104  (blog server or SNS server). The upload of the content data  105  is carried out by transmitting the content data  105  to the Web server  104  on the Internet  103  through an access point/router  102  in a LAN environment  101  and storing the content data  105  in the Web server  104 . The LAN environment  101  may be either a wired LAN or a wireless LAN. When a wired LAN environment is used, the connection to the Internet  103  is established through a router. When, on the other hand, a wireless LAN is used, the connection to the Internet  103  is established through an access point. A user (movie viewer)  111  at a remote location accesses the Web server  104  from a PC  106 , a mobile phone  107 , a DTV (Digital Television) set  108 , or other external device (terminal) on which a Web browser is installed. The user (movie viewer)  111  can then view the content data  105  stored in the Web server  104 . 
       FIG. 2  is a diagram illustrating the configuration of an imaging device according to an embodiment of the present invention. 
     The imaging device  200  ( 100 ) includes an imaging unit which has a lens  201 , an imaging element  202 , a camera DSP (Digital Signal Processor)  203 , and a microphone  204 . To process content, the imaging device  200  ( 100 ) includes an encoding/decoding circuit  205 , a CPU (Central Processing Unit)  206 , a memory (RAM)  207 , a content storage unit  208 , a graphics circuit  209 , a display section  210 , and a ROM (Read Only Memory)  214 . The imaging device  200  ( 100 ) also includes a power supply circuit  211 , a power supply  212 , and a communication module  213 . These component elements are interconnected by a bus  215  and allowed to transfer data between them. 
     An optical signal from a subject passes through the lens  201  and is converted to an electrical signal (digital video signal) by the imaging element  202 . The camera DSP  203  converts the video signal into a form acceptable to the encoding/decoding circuit  205 . An audio signal from the microphone  204  passes through the bus  215  and enters the encoding/decoding circuit  205 . The encoding/decoding circuit  205  generates an encoded stream in a predetermined format from the input video signal and audio signal. The content storage unit  208  stores the generated stream. The memory  207  is used as a work area for an encoding process. A hard disk drive, optical disk, semiconductor memory, or the like is employed as the content storage unit  208 . 
     When a shot image is to be playbacked, the encoded stream stored in the content storage unit  208  is loaded into the memory  207 . The encoding/decoding circuit  205  reads the stream from the memory  207  and subjects it to a decoding process. The decoded image data is passed to the graphics circuit  209  so that the display section  210  displays a playbacked image. 
     The communication module section  213  connects to the Internet  103  through the access point/router  102  and transmits (uploads) the image data to the Web server  104 . If necessary, the stored encoded stream may be further processed before being transmitted as the image data. The data to be transmitted also includes various file transfer protocol commands. 
     The ROM  214  stores a program for performing the above operations. The CPU  206  controls the operations of various sections in accordance with the program. Either a battery or AC power supply may be employed as the power supply  212 . The power supply circuit  211  controls the supply of power in the imaging device. 
     When a battery is employed as the power supply  212 , the present embodiment monitors the remaining battery power to limit the power consumption. This prevents an upload failure due to insufficient power supply to the communication module section  213  during an upload. To implement the above functionality, the ROM  214  stores the following software sections. The functions of the following software sections may alternatively be implemented by hardware. 
     A power saving mode setup section  221  stores the information about a mode chosen by a user who places a power saving switch in either a “normal mode” or a “power saving mode”. In the “power saving mode”, a battery-powered upload is prevented to save battery power. 
     A power supply identification section  222  determines whether a battery or an AC power supply (AC adapter) is employed as a drive power supply. If a battery is employed as the drive power supply, the supply of power is limited. 
     A remaining battery power value acquisition section  223  acquires a current remaining battery power value P to compare it against a predetermined value P 0 . When the remaining battery power value P is less than the predetermined value P 0 , an upload operation is interrupted. 
     An interruption information storage section  224  stores the information about a point of content interruption when an upload operation is interrupted. The information about the point of interruption includes, for instance, the size of a transmitted file and the timestamp of a transmitted stream. The use of the interruption information makes it possible to smoothly resume an interrupted upload from where it has been left off (from the middle of a file). 
     A remaining battery power value prediction section  225  predicts a remaining battery power value prevailing upon completion of an upload before the beginning of the upload. The remaining battery power value is predicted by performing calculations on the time required for uploading the file to be transmitted and the hourly power consumption of the communication module section  213 . When the predicted remaining battery power value P′ is less than the predetermined value P 0 , the imaging device does not start the upload, but displays a warning to indicate that the remaining battery power will be insufficient. 
     First Embodiment  
     A content upload process according to a first embodiment of the present invention will now be described in detail. In the first embodiment, the “power saving mode” is used to save battery power. Therefore, when the imaging device is battery-driven, it prevents an upload to save battery power. 
       FIG. 3  is a flowchart (S 300 ) illustrating an exemplary content upload process according to the first embodiment. It is assumed that the content storage unit  208  stores files containing image data (content) shot by a user in encoded stream format. 
     In step S 301 , the user places the power saving switch in either the “normal mode” or the “power saving mode”. The power saving mode setup section  221  then stores the information about the selected mode. 
     When an upload command is received from the user, step S 302  is performed to switch to an upload mode. The command for switching to the upload mode is issued, for instance, by pressing an upload button or by selecting a content upload command from a GUI menu displayed on the display section  210 . 
     In step S 303 , the display section  210  displays a group of uploadable content files ( FIG. 4 ). 
     In step S 304 , the user views the group of content files, and then selects the content file to be uploaded. 
     In step S 305 , the power supply identification section  222  determines the type of drive power supply (battery or AC power supply). When a battery is employed as the drive power supply, the imaging device proceeds to step S 306 . When, on the other hand, an AC power supply is employed, the imaging device proceeds to step S 307 . 
     In step S 306 , the power saving mode setup section  221  judges whether the power saving mode or normal mode prevails. When the power saving mode prevails, the imaging device proceeds to step S 310 . When, on the other hand, the normal mode prevails, the imaging device proceeds to step S 307 . 
     In step S 307 , the power supply circuit  211  supplies power to the communication module section  213 . 
     In step S 308 , the content to be transmitted is read from the content storage unit  208 , and uploaded (transmitted) from the communication module section  213  to the Web server. 
     In step S 309 , the power supply to the communication module section  213  is shut off upon completion of the upload. 
     In step S 310 , the process terminates with a warning screen ( FIG. 5 ) opened to indicate that the upload cannot be performed. 
       FIG. 4  shows an example of an upload file selection screen  400  which is used in steps S 303  and S 304  of  FIG. 3 . 
     A message  401  appears in the screen  400  to prompt the user to select the file to be uploaded. The screen  400  displays thumbnails  402  of pieces of content stored in the content storage unit  208 . The user moves a selection border  403  to select the content file to be uploaded.  FIG. 4  indicates that “file 004 ” is chosen. To close the upload file selection screen, the user chooses a Cancel button  404 . 
       FIG. 5  shows an example of a warning screen  500 , which opens in step S 310  of  FIG. 3 . 
     A message  501  appears in the screen  500  to indicate that the upload cannot be performed. The message also prompts the user to switch from the power saving mode to the normal mode or use an AC power supply (AC adapter). A Change Mode button  502  is used to switch between the power saving mode and the normal mode. To close the warning screen, the user chooses a Cancel button  503 . 
     As described above, the first embodiment makes it possible to enter the power saving mode. When the imaging device is battery-powered in the power saving mode, it saves battery power by halting the operation of the communication module section  213 , which consumes a large amount of power. Therefore, the power saving mode makes it possible to prevent an upload failure due to insufficient power supply to the communication module section  213  during an upload. The user can choose the power saving mode in consideration of shooting conditions. Further, the first embodiment makes it possible to reduce the power consumption by supplying power to the communication module section  213  only during the beginning of a content upload and shutting off the power supply to the communication module section  213  during the other period (e.g., during a shooting period). 
     Second Embodiment  
     A second embodiment of the present invention will now be described. The second embodiment monitors the amount of remaining battery power during an upload. When the amount of remaining battery power is less than a predetermined value, the second embodiment performs an upload interruption process. 
       FIG. 6  is a flowchart (S 600 ) illustrating an upload process according to the second embodiment. The upload process, which corresponds to the upload process (step S 308 ) according to the first embodiment ( FIG. 3 ), will now be described in detail. The other steps are the same as those of  FIG. 3  and will therefore not be described here. 
     In step S 601 , a screen opens to ask whether the user wants to upload a selected content file ( FIG. 8 ). 
     In step S 602 , the communication module section  213  searches for an access point  102  that is present within the range of a wireless LAN. When such an access point  102  is located, the communication module section  213  connects to a Web server  104  at a transmission destination through the Internet  103 . 
     In step S 603 , the selected content file is read from the content storage unit  208 . A file transfer protocol is then used to start transmitting the file to the Web server  104 . 
     In step S 604 , the imaging device judges whether a cancel command has been received from the user during an upload. When such a cancel command has been received, the imaging device proceeds to step S 608  and performs an upload interruption process. When, on the other hand, no such cancel command has been received, the imaging device proceeds to step S 605 . 
     In step S 605 , the power supply identification section  222  determines the type of drive power supply (battery or AC power supply). When a battery is employed as the drive power supply, the imaging device proceeds to step S 606 . When, on the other hand, an AC power supply is employed, the imaging device proceeds to step S 607 . 
     In step S 606 , the remaining battery power value acquisition section  223  acquires a current remaining battery power value P and compares it against a predetermined value P 0 . It is assumed that the predetermined value P 0  represents a minimum amount of power required for performing the upload interruption process in step S 608 . More specifically, it is assumed that the predetermined value P 0  denotes the amount of power required for smooth execution of a series of upload interruption steps (interruption point recording, file close process, Web server disconnection, and interruption information display process) shown in  FIG. 7 . When the remaining battery power value P is equal to or greater than the predetermined value P 0 , the imaging device proceeds to step S 607 . When, on the other hand, the remaining battery power value P is less than the predetermined value P 0 , the imaging device concludes that the remaining battery power is not sufficient for the completion of a content upload, proceeds to step S 608 , and performs the upload interruption process. 
     In step S 607 , the imaging device judges whether the file to be transmitted is completely read. When the file has not been completely read, the imaging device returns to step S 603  and continues to read and transmit the file. After the file is completely read, the upload process terminates. 
     In step S 608 , the file transmission is halted to perform the upload interruption process by closing the content file. The upload interruption process will be described in detail with reference to  FIG. 7 . 
       FIG. 7  is a flowchart (S 700 ) illustrating the upload interruption process, which is performed in step S 608  of  FIG. 6 . 
     In step S 701 , the interruption information storage section  224  records the information about an interruption point of the content that has been uploaded. The information about the interruption point includes, for instance, the size of a transmitted file and the timestamp of a transmitted stream. 
     In step S 702 , a process is performed to close the content file that has been uploaded. 
     In step S 703 , the communication module section  213  breaks a network connection with the Web server  104 . 
     In step S 704 , the display section  210  opens a screen to indicate that the upload is interrupted ( FIG. 9 ). 
       FIG. 8  shows an example of an upload start screen  800  which opens in step S 601  of  FIG. 6 . A final confirmation message  801  appears in the screen  800  to ask whether the user wants to start an upload. In the example shown in  FIG. 8 , the message  801  asks whether the user wants to upload “file 004 ”, with a thumbnail  802  of the file displayed. The user can perform an upload process by choosing an Upload button  803  or cancel the upload process by choosing a Cancel button  804 . 
       FIG. 9  shows an example of an upload interruption screen  900  which opens in step S 704  of  FIG. 7 . The screen  900  displays a message  901 , a thumbnail  902  of an interruption point  902 , a remaining battery power indicator  903 , and an OK button  905 . The message  901  indicates that an upload is interrupted because the amount of remaining battery power is small. The remaining battery power indicator  903  shows the amount of current remaining battery power  904 . The user chooses the OK button  905  to recognize that the upload is interrupted. The screen  900  informs the user of an upload interruption and the reason therefor. 
     The second embodiment monitors the amount of remaining battery power during an upload. When the amount of remaining battery power is less than the predetermined value, the second embodiment performs the upload interruption process. This prevents the power supply to the content storage unit in the imaging device from being suddenly shut off, thereby avoiding the risk of damaging a currently accessed file. Meanwhile, a third person is allowed to unfailingly access and view the content transmitted to the Web server as far as a transmission termination process is performed normally. 
     Further, the second embodiment provides increased user-friendliness because it displays the information about an upload interruption to inform the user that specified content is not completely uploaded. Moreover, the second embodiment memorizes the point of upload interruption. Therefore, it is possible to ensure the integrity of a file that is incompletely uploaded to the Web server. This feature provides effective support for resuming an interrupted upload. The second embodiment is useful when movie content is to be hastily uploaded as long as battery capacity allows. 
     Third Embodiment  
     A third embodiment of the present invention will now be described. The third embodiment estimates the amount of battery power remaining upon completion of a content upload to a Web server before the start of the content upload to perform the upload with increased certainty. 
       FIG. 10  is a flowchart (S 1000 ) illustrating an upload process according to the third embodiment. 
     In step S 1001 , the power supply identification section  222  determines the type of drive power supply (battery or AC power supply). When a battery is employed as the drive power supply, the imaging device proceeds to step S 1002 . When, on the other hand, an AC power supply is employed, the imaging device proceeds to step S 600  of  FIG. 6  and starts performing the upload process. 
     In step S 1002 , the remaining battery power value prediction section  225  estimates the amount of battery power remaining upon completion of an upload. The amount of remaining battery power can be estimated by determining upload time from a content transfer rate and the size of the file to be uploaded and performing a calculation on the hourly power consumption of the communication module section  213 . 
     In step S 1003 , the predicted remaining battery power value P′ is compared against a predetermined value P 0 . It is also assumed that the predetermined value P 0  includes the amount of power required for the upload interruption process. When the predicted remaining battery power value P is equal to or greater than the predetermined value P 0 , the imaging device proceeds to step S 600  and starts performing the upload process. When, on the other hand, the predicted remaining battery power value P is less than the predetermined value P 0 , the imaging device proceeds to step S 1004 . 
     In step S 1004 , the imaging device does not start performing the upload process, but opens a warning screen ( FIG. 11 ) to warn the user that the predicted battery power remaining upon completion of an upload is insufficient. 
     In step S 1005 , the imaging device receives a user&#39;s response to the warning. When the user instructs the imaging device to cancel the upload, the imaging device terminates its operation without performing the upload process. When, on other hand, the user reinstructs the imaging device to perform the upload process although the predicted remaining battery power is insufficient, the imaging device is forced to perform the upload process in step S 600 . 
     In the upload process (step S 600 ) shown in  FIG. 6 , the current remaining battery power is monitored (step S 606 ) even after the start of an upload to perform the upload interruption process if the amount of remaining battery power is too small. Therefore, the upload process will be completed without fail. 
       FIG. 11  shows an example of a warning screen  1100 , which opens in step S 1004  of  FIG. 10 . The screen  1100  displays a warning message  1101 , a remaining battery power indicator  1102  for indicating battery usage, an Upload button  1104 , and a Cancel button  1105 . The warning message  1101  indicates that the amount of remaining battery power is insufficient for completing the upload of the selected content. The warning message  1101  also prompts the user to connect an AC power supply (AC adapter) as an alternative power supply. The remaining battery power indicator  1102  shows the amount of predicted remaining battery power  1103 , thereby permitting the user to grasp the predicted power consumption of the battery. When the user chooses the Cancel button  1105 , the imaging device terminates its operation without performing the upload. When, on other hand, the user chooses the Upload button  1104 , the imaging device is forced to perform the upload no matter whether the remaining battery power is insufficient for the completion of the upload. 
     The third embodiment determines whether or not to start a process by estimating the amount of battery power remaining upon completion of an upload before its start. Therefore, the third embodiment can perform the upload with increased certainty without encountering a situation where the available power becomes suddenly insufficient during the upload. Further, the third embodiment displays the information about battery power insufficiency beforehand, thereby allowing the user to form an appropriate judgment as to whether the user, depending on the prevailing situation, should switch to the AC power supply or force the imaging device to initiate the upload process. This feature provides increased user-friendliness. 
     Moreover, using the third embodiment in conjunction with the second embodiment makes it possible to prevent an upload failure even if the imaging device is forced to initiate the upload process when the amount of predicted remaining battery power is less than the predetermined value. The reason is that the imaging device can interrupt the upload process and display the information about the upload interruption when the amount of battery power remaining during the upload process is close to the predetermined value. 
     Fourth Embodiment  
     A fourth embodiment of the present invention will now be described. The fourth embodiment properly resumes an interrupted content upload when performing an upload start process subsequently to upload interruption by the second embodiment. It should be noted that the upload interruption process (S 700 ) is performed as shown in  FIG. 7  to record, in the interruption information storage section  224 , the information about an interruption point of content. 
       FIG. 12  is a flowchart (S 1200 ) illustrating an upload resumption process that is performed on content whose upload has been interrupted. 
     In step S 1201 , an upload command is received from the user. 
     In step S 1202 , the information about content whose upload has been interrupted is read from the interruption information storage section  224 . 
     In step S 1203 , the read information is used to judge whether there is interrupted content. When there is interrupted content, the imaging device proceeds to step S 1204 . When, on the other hand, there is no interrupted content, the imaging device performs a normal upload process. More specifically, the imaging device proceeds to step S 303  of  FIG. 3 , displays stored content files for selection, and uploads a selected content file. 
     In step S 1204 , the imaging device displays a thumbnail of interrupted content ( FIG. 13 ). When there are a plurality of pieces of interrupted content, the imaging device displays a list of their thumbnails. 
     In step S 1205 , the user is prompted to select the content whose upload is to be resumed. When the user cancels the upload resumption process, the imaging device terminates its operation without performing anything. When, on the other hand, the user chooses to resume the upload, the imaging device proceeds to step S 1206 . 
     In step S 1206 , the communication module section  213  resumes the upload of interrupted content from the point of interruption. Here, the upload process is performed in the same manner as that in steps S 305  and beyond of  FIG. 3 . 
     Step S 1207  is performed upon completion of the upload process to delete the information about the interrupted content from the interruption information storage section  224 . 
       FIG. 13  shows an example of an upload resumption screen  1300  which opens in step S 1204  of  FIG. 12 . The screen  1300  displays a resumption message  1301 , a thumbnail  1302  of a resumption point, a remaining battery power indicator  1303 , the amount of current remaining battery power  1304 , a Resume button  1305 , and a Cancel button  1306 . The message  1301  informs the user that there is content whose upload has been interrupted, and prompts the user to resume its upload. The user chooses the Resume button  1305  to resume the upload or chooses the Cancel button  1406  to cancel the upload. 
     When there is any content whose upload has been interrupted, the fourth embodiment automatically informs the user of it and prompts for the resumption of its upload. Therefore, even when the user is not aware of content whose upload has been interrupted, the fourth embodiment enables the user to resume its upload unfailingly and smoothly. 
     The configurations and processes of the above-described embodiments are merely illustrative. Further, the features provided by the individual embodiments can be combined as needed. 
     While we have shown and described several embodiments in accordance with our invention, it should be understood that disclosed embodiments are susceptible of changes and modifications without departing from the scope of the invention. Therefore, we do not intend to be bound by the details shown and described herein but intend to cover all such changes and modifications that fall within the ambit of the appended claims.