Abstract:
A reproduction apparatus and method for reproducing selected digital data reproduces digital data selected by a user, detects remaining power of a battery, and determines whether the selected digital data can be reproduced to the end or not based on the detected remaining power. Before the selected digital data is reproduced, if it is determined that there is sufficient battery power to reproduce the selected digital data to the end, then the selected digital data is reproduced. If not, a warning is provided and the user selects either a first reproduction mode or a second reproduction mode. If the first reproduction mode is selected, the selected digital data is reproduced. If the second reproduction mode is selected, summary data that includes a summary of the selected digital data is reproduced.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an apparatus for reproducing digital data such as video data and audio data, and more particularly, to a reproduction apparatus that carries out reproduction processing in consideration of remaining power of a battery. 
   BACKGROUND OF THE INVENTION 
   Portable devices such as a portable video player, portable audio player, notebook PC and PDA (Personal Digital Assistant) are driven by a battery and have the function of reproducing digital data such as video data and audio data. 
   However, conventional portable devices cannot carry out reproduction processing in consideration of remaining power of a battery. Thus, the conventional portable devices cannot decide before reproducing desired digital data whether the digital data can be reproduced to the end or not. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in consideration of the above situation, and has as its object to implement reproduction processing in consideration of the remaining power of the battery. 
   According to the present invention, the foregoing object is attained by providing a reproduction apparatus comprising: a prediction unit that predicts a reproducible time based on remaining power of a battery; and a decision unit that decides whether digital data selected by a user can be reproduced to the end or not based on the reproducible time, wherein when the digital data cannot be reproduced to the end, an alarm is issued indicating that the digital data cannot be reproduced to the end. 
   According to the present invention, the foregoing object is also attained by providing a control method comprising: predicting a reproducible time based on remaining power of a battery; deciding whether digital data selected by a user can be reproduced to the end or not based on the reproducible time; and warning when the digital data cannot be reproduced to the end that the digital data cannot be reproduced to the end. 
   Further, the foregoing object is also attained by providing a reproduction apparatus comprising: a detection unit that detects remaining power of a battery; and a decision unit that decides whether digital data selected by a user can be reproduced to the end or not based on the remaining power of the battery, wherein when the digital data cannot be reproduced to the end, an alarm is issued to indicate that the digital data cannot be reproduced to the end. 
   Furthermore, the foregoing object is also attained by providing a control method comprising: detecting remaining power of a battery; deciding whether digital data selected by a user can be reproduced to the end or not based on the remaining power of the battery; warning when the digital data cannot be reproduced to the end that the digital data cannot be reproduced to the end. 
   Still further, the foregoing object is attached by providing a reproduction apparatus comprising: a reproduction unit that reproduces digital data selected by a user; a detection unit that detects remaining power of a battery; and a determination unit that determines whether the selected digital data can be reproduced to the end or not based on the remaining power detected by the detection unit, before the reproduction unit starts reproducing the selected digital data, wherein if it is determined by the determination unit that the selected digital data can be reproduced to the end, the reproduction apparatus causes the reproduction unit to reproduce the selected digital data, and wherein if it is determined by the determination unit that the selected digital data cannot be reproduced to the end, the reproduction apparatus warns that the selected digital data cannot be reproduced to the end and causes the user to select one of first and second reproduction modes, if the first reproduction mode is selected by the user, the reproduction apparatus causes the reproduction unit to reproduce the selected digital data, and if the second reproduction mode is selected by the user, the reproduction apparatus causes the reproduction unit to reproduce summary data including a summary of the selected digital data. 
   The foregoing object is also attained by a method for controlling a reproduction apparatus having a reproduction unit that reproduces digital data selected by a user, the method comprising the steps of: detecting remaining power of a battery; determining whether the selected digital data can be reproduced to the end or not based on the remaining power detected in the detecting step, before the reproduction unit starts reproducing the selected digital data; if it is determined in the determining step that the selected digital data can be reproduced to the end, causing the reproduction unit to reproduce the selected digital data; if it is determined in the determining step that the selected digital data cannot be reproduced to the end, warning that the selected digital data cannot be reproduced to the end; if it is determined in the determining step that the selected digital data cannot be reproduced to the end, causing the user to select one of first and second reproduction modes; if the first reproduction mode is selected by the user, causing the reproduction unit to reproduce the selected digital data; and if the second reproduction mode is selected by the user, causing the reproduction unit to reproduce summary data including a summary of the selected digital data. 
   Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  is a block diagram showing a configuration example of a reproduction apparatus according to first and second embodiments; 
       FIG. 2  is a flow chart showing a processing procedure of the reproduction apparatus according to the first embodiment; 
       FIG. 3  is a flow chart showing a processing procedure of the reproduction apparatus according to the second embodiment; 
       FIG. 4  is a block diagram showing a configuration example of a reproduction apparatus according to third and fourth embodiments; 
       FIG. 5  is a flow chart showing a processing procedure of the reproduction apparatus according to the third embodiment of the present invention; and 
       FIG. 6  is a flow chart showing a processing procedure of the reproduction apparatus according to the fourth embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of the present invention will be described in detail in accordance with the accompanying drawings. 
   First Embodiment 
   With reference to  FIG. 1  and  FIG. 2 , a first embodiment of the present invention will be explained in detail below. 
   First, with reference to the block diagram in  FIG. 1 , a configuration example of a reproduction apparatus  10  according to a first embodiment will be explained. The reproduction apparatus  10  shown in  FIG. 1  is a portable device that is driven by a battery  100  and has the function of reproducing digital data stored in a storage medium  105 . The digital data that the reproduction apparatus  10  reproduces from the storage medium  105  may be video data, audio data, or video data with audio data. 
   As shown in  FIG. 1 , the reproduction apparatus  10  includes the battery  100 , a detection section  101 , a prediction section  102 , a reproduction control section  103 , a UI section  104 , a storage medium  105 , a display section  106  and a speaker section  107 . 
   The detection section  101  has the function of detecting the remaining power of the battery  100 . The prediction section  102  has the function of predicting an reproducible time using the remaining power of the battery  100 . The reproduction control section  103  has the function of reproducing the digital data selected by the user from the storage medium  105 . The user interface section (UI section)  104  has the function of notifying the reproduction control section  103  of the user&#39;s instructions. The display section  106  displays video data in the digital data reproduced from the storage medium  105 . The speaker section  107  outputs the audio data in the digital data reproduced from the storage medium  105 . 
   Next, the processing procedure of the reproduction apparatus  10  according to the first embodiment will be explained with reference to the flow chart in  FIG. 2 . 
   In step S 201 , the UI section  104  prompts the user to select digital data to be reproduced. 
   In step S 202 , the reproduction control section  103  calculates a total reproduction time Tt which is a time required to reproduce all the digital data selected by the user (hereinafter referred to as “selected data”). 
   In step S 203 , the reproduction control section  103  makes the detection section  101  detect the current remaining power of the battery  100  and makes the prediction section  102  predict the current reproducible time Ta. At this time, the detection section  101  detects the current remaining power of the battery  100  and notifies it to the prediction section  102 . In turn, the prediction section  102  predicts the current reproducible time Ta using the current remaining power of the battery  100  and notifies it to the reproduction control section  103 . 
   In step S 204 , the reproduction control section  103  decides whether the current reproducible time Ta is longer than the total reproduction time Tt or not. This decision corresponds to a decision as to whether the selected data can be reproduced to the end or not. 
   When the current reproducible time Ta is longer than the total reproduction time Tt (YES in step S 204 ), the selected data can be reproduced to the end. In this case, the process moves on to step S 205  and the reproduction control section  103  starts reproduction of the selected data without creating any summary of the selected data. 
   On the other hand, if the current reproducible time Ta is not longer than the total reproduction time Tt (NO in step S 204 ), the battery  100  will be exhausted during reproduction of the selected data, and therefore the selected data will not be reproduced to the end. In this case, the process moves on to step S 206  and the reproduction control section  103  displays a message or icon on the display section  106  indicating that the selected data cannot be reproduced to the end and warns the user of it. At this time, the reproduction control section  103  can also display the total reproduction time Tt, reproducible time Ta and their difference on the display section  106 . 
   In step S 207 , the UI section  104  prompts the user to select a normal reproduction mode or summary reproduction mode. When the user selects the normal reproduction mode, the process in step S 205  is executed. On the other hand, if the user selects the summary reproduction mode, the process in step S 208  is executed. 
   In step S 208 , the UI section  104  prompts the user to select one of summary schemes. 
   In step S 209 , the reproduction control section  103  generates summary data which is a summary of the selected data based on the summary scheme selected by the user. At this time, the reproduction control section  103  makes sure that the total reproduction time of the summary data is shorter than a current reproducible time Ta. It should be noted that if the time taken to generate the summary is long, the remaining power of the battery  100  may reduce drastically causing the reproducible time to be shortened. Thus, upon creating summary data the reproduction apparatus  10  according to the first embodiment re-predicts a reproducible time at predetermined intervals and compares it with the total reproduction time. 
   After the reproduction of the summary data is started, operations such as fast rewind, fast forward and pause may reduce the remaining power of the battery  100  drastically, causing the battery  100  to be exhausted during the reproduction of the summary data. Therefore, the UI section  104  starts the reproduction of the summary and then disables operations other than stop (fast rewind, fast forward, pause, etc.) in step S 210 . This function prevents the reproduction of the summary data from being interrupted midway. 
   In step S 211 , the reproduction control section  103  starts to reproduce the summary data. If video data is found in the summary data, the reproduction control section  103  processes it and supplies it to the display section  106  and if audio data is found in the summary data, the reproduction control section  103  processes it and supplies it to the speaker section  107 . 
   As described above, the reproduction apparatus  10  according to the first embodiment can perform reproduction processing in consideration of the remaining power of the battery  100 . Furthermore, when the remaining power of the battery  100  is too small to reproduce the digital data selected by the user to the end, the reproduction apparatus  10  according to the first embodiment can warn the user of it. 
   Next, the summary scheme that can be selected in step S 208  will be explained. 
   (1) Summary Scheme 1 
   In this scheme, the reproduction control section  103  automatically generates summary data of the selected data. 
   (2) Summary Scheme 2 
   This scheme allows the user to select portions to be reproduced and gathers the portions selected by the user to generate summary data of the selected data. 
   (3) Summary System 3 
   In this scheme, the reproduction control section  103  automatically generates summary data of the selected data based on user preference information which is information on the user&#39;s preferences. As the user&#39;s preference information, it is possible to use information specified by the MPEG-7 standard. 
   (4) Summary System 4 
   This scheme allows the user to select portions to be reproduced from among portions automatically selected by the reproduction control section  103  based on the user&#39;s preference information and gathers the portions selected by the user to generate summary data of the selected data. 
   Second Embodiment 
   With reference to  FIG. 1  and  FIG. 3 , a second embodiment of the present invention will be explained in detail below. 
   With reference to the flow chart in  FIG. 3 , a processing procedure of the reproduction apparatus  10  according to the second embodiment will be explained. 
   In step S 301 , the UT section  104  prompts the user to select digital data to be reproduced. 
   In step S 302 , the reproduction control section  103  calculates a total reproduction time Tt, which is a time necessary to reproduce all digital data selected by the user (hereinafter referred to as “selected data”). 
   In step S 303 , the reproduction control section  103  makes the detection section  101  detect the current remaining power of the battery  100  and makes the prediction section  102  predict the current reproducible time Ta. At this time, the detection section  101  detects the current remaining power of the battery  100  and notifies it to the prediction section  102 . In turn, the prediction section  102  predicts the current reproducible time Ta using the current remaining power of the battery  100  and notifies it to the reproduction control section  103 . 
   In step S 304 , the reproduction control section  103  decides whether the current reproducible time Ta is longer than the total reproduction time Tt or not. This decision corresponds to a decision as to whether the selected data can be reproduced to the end or not. 
   When the current reproducible time Ta is longer than the total reproduction time Tt (YES in step S 304 ), the selected data can be reproduced to the end. In this case, the process moves on to step S 305  and the reproduction control section  103  starts reproduction of the selected data without creating any summary of the selected data. 
   In step S 306 , the reproduction control section  103  decides whether the reproduction of the selected data is completed or not. 
   If the reproduction of the selected data is not completed (NO in step S 306 ), in step S 307 , the reproduction control section  103  calculates the remaining reproduction time Tr of the selected data. 
   In step S 308 , the reproduction control section  103  makes the detection section  101  redetect the current remaining power of the battery  100  and makes the prediction section  102  predict the current reproducible time Ta. At this time, the detection section  101  detects the current remaining power of the battery  100  and notifies it to the prediction section  102 . In turn, the prediction section  102  predicts the current reproducible time Ta using the current remaining power of the battery  100  and notifies it to the reproduction control section  103 . 
   In step S 309 , the reproduction control section  103  decides whether the current reproducible time Ta is longer than the remaining reproduction time Tr or not. This decision corresponds to a decision as to whether the selected data can be reproduced to the end or not. If the reproducible time Ta is longer than the remaining reproduction time Tr (YES in step S 309 ), the process moves back to step S 306  and the reproduction control section  103  continues to reproduce the selected data. 
   When the current reproducible time Ta is not longer than the reproduction time Tr (NO in step S 309 ), the selected data cannot be reproduced to the end. In this case, the process moves on to step S 310  and the reproduction control section  103  decides whether a normal reproduction mode is selected or not. If the normal reproduction mode is selected, the reproduction control section  103  continues to reproduce the selected data without generating any summary. 
   After the determination of step S 304 , when the current reproducible time Ta is not longer than the total reproduction time Tt (NO in step S 304 ) or when the normal reproduction mode is not selected in step S 310 , the battery  100  will be exhausted during reproduction of the selected data, and therefore the selected data will not be reproduced to the end. In this case, the process moves on to step S 311 , the reproduction control section  103  displays a message or icon on the display section  106  indicating that the selected data cannot be reproduced to the end and warns the user of it. At this time, the reproduction control section  103  may also display the total reproduction time Tt, reproducible time Ta and their difference on the display section  106 . 
   In step S 312 , the UI section  104  prompts the user to select a normal reproduction mode or summary reproduction mode. When the user selects the normal reproduction mode, the process in step S 305  is executed. On the other hand, if the user selects the summary reproduction mode, the process in step S 313  is executed. 
   If the summary reproduction mode is selected, the UI section  104  prompts the user to select one of summary schemes in step S 313 . In step S 313 , for example, the summary scheme can be selected from the summary schemes 1 to 4 explained in the above-described first embodiment. 
   In step S 314 , the reproduction control section  103  generates summary data which is a summary of the selected data based on the summary scheme selected by the user. At this time, the reproduction control section  103  makes sure that the total reproduction time of the summary data is shorter than the current reproducible time Ta. If the time taken to generate the summary is long, the remaining power of the battery  100  may reduce drastically causing the reproducible time to be shortened. Thus, upon creating summary data the reproduction apparatus  10  according to the second embodiment re-predicts a reproducible time at predetermined intervals and compares it with the total reproduction time. 
   In step S 315 , the reproduction control section  103  starts to reproduce the summary data. Unlike the reproduction apparatus  10  according to the first embodiment, the reproduction apparatus  10  according to the second embodiment does not restrict operations such as fast rewind, fast forward, pause except a stop operation after the reproduction of the summary data is started. Therefore, if these operations are performed during reproduction, the remaining power of the battery may be too small to reproduce all summary data. Operations in and after step S 316  will be carried out to handle such a case. 
   In step S 316 , the reproduction control section  103  decides whether the reproduction of the summary data is completed or not. 
   If the reproduction of the summary data is not completed (NO in step S 316 ), the process moves on to step S 317  and the reproduction control section  103  calculates a remaining reproduction time Trs of the remaining summary data. 
   In step S 318 , the reproduction control section  103  makes the detection section  101  detect the current remaining power of the battery  100  and makes the prediction section  102  predict the current reproducible time Ta. At this time, the detection section  101  detects the current remaining power of the battery  100  and notifies it to the prediction section  102 . In turn, the prediction section  102  predicts the current reproducible time Ta using the current remaining power of the battery  100  and notifies it to the reproduction control section  103 . 
   In step S 319 , the reproduction control section  103  decides whether the reproducible time Ta is longer than the remaining reproduction time Trs or not. This decision corresponds to a decision as to whether the summary data can be reproduced to the end or not. When the reproducible time Ta is longer than the remaining reproduction time Trs (YES in step S 319 ), the process moves back to step S 316  and the reproduction control section  103  continues to reproduce the summary data. 
   When the reproducible time Ta is not longer than the remaining reproduction time Trs (NO in step S 319 ), the summary data cannot be reproduced to the end. In this case, the process moves on to step S 320  and the reproduction control section  103  changes the content of the summary data. Then, after changing the content of the summary data, the reproduction control section  103  starts to reproduce the changed summary data. If video data is found in the summary data, the reproduction control section  103  processes it and supplies it to the display section  106  and if audio data is found in the summary data, the reproduction control section  103  processes it and supplies it to the speaker section  107 . 
   As described above, the reproduction apparatus  10  according to the second embodiment can perform reproduction processing in consideration of the remaining power of the battery  100 . Furthermore, when the remaining power of the battery  100  is too small to reproduce the digital data selected by the user to the end, the reproduction apparatus  10  according to the second embodiment can warn the user of it. Furthermore, the reproduction apparatus  10  according to the second embodiment need not restrict operations such as fast rewind, fast forward, pause even in a summary reproduction mode. 
   Third Embodiment 
   With reference to  FIG. 4  and  FIG. 5 , a third embodiment of the present invention will be explained in detail below. 
   First, with reference to the block diagram in  FIG. 4 , a configuration example of a reproduction apparatus  40 , according to a third embodiment will be explained. The reproduction apparatus  4  shown in  FIG. 4  is a portable device that is driven by a battery  400  and has the function of reproducing digital data stored in a storage medium  405 . The digital data that the reproduction apparatus  40  reproduces from the storage medium  405  may be video data, audio data, or video data with audio data. 
   As shown in  FIG. 4 , the reproduction apparatus  40  includes the battery  400 , a detection section  401 , a prediction section  402 , a reproduction control section  403 , a UI section  404 , a storage medium  405 , a display section  406  and a speaker section  407 . 
   The detection section  401  has the function of detecting the remaining power of the battery  400 . The prediction section  402  has the function of predicting an reproducible time using the remaining power of the battery  400 . The reproduction control section  403  has the function of reproducing the digital data selected by the user from the storage medium  405 . The user interface section (UI section)  404  has the function of notifying the reproduction control section  403  of the user&#39;s instructions. The display section  406  displays video data in the digital data reproduced from the storage medium  405 . The speaker section  407  outputs the audio data in the digital data reproduced from the storage medium  405 . 
   Next, the processing procedure of the reproduction apparatus  40  according to the third embodiment will be explained with reference to the flow chart in  FIG. 5 . 
   In step S 401 , the UI section  404  prompts the user to select digital data to be reproduced 
   In step S 402 , the reproduction control section  403  makes the prediction section  402  to predict total power consumption Pt which is power consumption required to reproduce all the digital data selected by the user (hereinafter referred to as “selected data”). The prediction section  402  predicts the current total power consumption Pt and notifies it to the reproduction control section  403 . 
   In step S 403 , the reproduction control section  403  makes the detection section  401  detect the current remaining power Pb of the battery  400 . The detection section  401  detects the current remaining power Pb of the battery  400  and notifies it to the reproduction control section  403 . 
   In step S 404 , the reproduction control section  403  decides whether the current remaining power Pb of the battery  400  is greater than the total power consumption Pt or not. This decision corresponds to a decision as to whether the selected data can be reproduced to the end or not. 
   When the current remaining power Pb of the battery  400  is greater than the total power consumption Pt (YES in step S 404 ), the selected data can be reproduced to the end. In this case, the process moves on to step S 405  and the reproduction control section  403  starts to reproduce the selected data without generating any summary of the selected data. 
   On the other hand, when the current remaining power Pb of the battery  400  is not greater than the total power consumption Pt (NO in step S 404 ), the battery  400  will be exhausted during reproduction of the selected data and the selected data will not be reproduced to the end. In this case, the process moves on to step S 406 , the reproduction control section  403  displays a message or icon on the display section  406  indicating that the selected data cannot be reproduced to the end and warns the user of it. At this time, the reproduction control section  403  can also display the current remaining power Pb of the battery  400 , total power consumption Pt and the difference thereof on the display section  406 . 
   In step S 407 , the UI section  404  prompts the user to select a normal reproduction mode or summary reproduction mode. When the user selects the normal reproduction mode, the process in step S 405  is executed. On the other hand, if the user selects the summary reproduction mode, the process in step S 408  is executed. 
   In step S 408 , the UI section  404  prompts the user to select one of the summary schemes. In step S 408 , for example, the summary scheme can be selected from the summary schemes 1 to 4 explained in the above-described first embodiment. 
   In step S 409 , the reproduction control section  403  generates summary data which is a summary of the selected data based on the summary scheme selected by the user. At this time, the reproduction control section  403  makes sure that the total power consumption of the summary data is smaller than the current remaining power Pb of the battery  400 . If the time taken to generate the summary is long, the remaining power of the battery  400  may reduce drastically. Thus, upon creating summary data the reproduction apparatus  40  according to this third embodiment re-detects the remaining power of the battery  400  at predetermined intervals and compares it with the total power consumption of the summary data. 
   After the reproduction of the summary data is started, operations such as fast rewind, fast forward and pause may reduce the remaining power of the battery  400  drastically, causing the battery  400  to be exhausted during the reproduction of the summary data. Therefore, the UI section  404  starts the reproduction of the summary and then disables operations other than stop (fast rewind, fast forward, pause, etc.) in step S 410 . This function prevents the reproduction of the summary data from being interrupted midway. 
   In step S 411 , the reproduction control section  403  starts to reproduce summary data. If video data is found in the summary data, the reproduction control section  403  processes it and supplies it to the display section  406  and if audio data is found in the summary data, the reproduction control section  403  processes it and supplies it to the speaker section  407 . 
   As described above, the reproduction apparatus  40  according to the third embodiment can perform reproduction processing in consideration of the remaining power of the battery  400 . Furthermore, when the remaining power of the battery  400  is not enough to reproduce the digital data selected by the user to the end, the reproduction apparatus  40  according to the third embodiment can warn the user of it. 
   Fourth Embodiment 
   With reference to  FIG. 4  and  FIG. 6 , the fourth embodiment of the present invention will be explained in detail below. The operation carried out by the prediction section  402  is the same as the operation explained in the above-described third embodiment. 
   With reference to the flow chart in  FIG. 6 , the processing procedure of the reproduction apparatus  40  according to the fourth embodiment will be explained. 
   In step S 501 , the UI section  404  prompts the user to select digital data to be reproduced. 
   In step S 502 , the reproduction control section  403  makes the prediction section  402  predict total power consumption Pt which is power consumption necessary to reproduce all digital data selected by the user (hereinafter referred to as “selected data”). The prediction section  402  predicts the total power consumption Pt of the selected data and notifies it to the reproduction control section  403 . 
   In step S 503 , the reproduction control section  403  makes the detection section  401  detect the current remaining power of the battery  400 . The detection section  401  detects the current remaining power Pb of the battery  400  and notifies it to the reproduction control section  403 . 
   In step S 504 , the reproduction control section  403  decides whether the current remaining power Pb of the battery  400  is greater than the total power consumption Pt or not. This decision corresponds to a decision as to whether the selected data can be reproduced to the end or not. 
   If the current remaining power Pb of the battery  400  is greater than the total power consumption Pt (YES in step S 504 ), the selected data can be reproduced to the end. In this case, the process moves on to step S 505  and the reproduction control section  403  starts to reproduce the selected data without generating any summary of the selected data. 
   In step S 506 , the reproduction control section  403  decides whether the reproduction of the selected data is completed or not. 
   If the reproduction of the selected data is not completed (NO in step S 506 ), in step S 507 , the reproduction control section  403  makes the prediction section  402  predict power consumption Pr of the unreproduced portion of the selected data. The prediction section  402  predicts the power consumption Pr of the unreproduced portion and notifies it to the reproduction control section  403 . 
   In step S 508 , the reproduction control section  403  makes the detection section  401  re-detect the current remaining power Pb of the battery  400 . The detection section  401  detects the current remaining power Pb of the battery  400  and notifies it to the reproduction control section  403 . 
   In step S 509 , the reproduction control section  403  decides whether the current remaining power Pb of the battery  400  is greater than the power consumption Pr or not. This decision corresponds to a decision as to whether the selected data can be reproduced to the end or not. If the current remaining power Pb of the battery  400  is greater than the power consumption Pr (YES in step S 509 ), the process moves back to step S 506  and the reproduction control section  403  continues to reproduce the selected data. 
   If the current remaining power Pb of the battery  400  is not greater than the power consumption Pr (NO in step S 509 ), the selected data cannot be reproduced to the end. In this case, the process moves on to step S 510  and the reproduction control section  403  decides whether the normal reproduction mode is selected or not. If the normal reproduction mode is selected, the reproduction control section  403  continues to reproduce the selected data without creating any summary. 
   Furthermore, as a result of the decision in step S 504 , if the current remaining power Pb of the battery  400  is not greater than the power consumption Pt (NO in step S 504 ) or if the normal reproduction mode is not selected in step S 510 , the battery  400  will be exhausted during reproduction of the selected data, and therefore the selected data will not be reproduced to the end. In this case, the process moves on to step S 511  and the reproduction control section  403  displays a message or icon on the display section  406  indicating that the selected data cannot be reproduced to the end and warns the user of it. At this time, the reproduction control section  403  may also display the current remaining power Pb of the battery  400 , power consumption Pt or Pr of the unreproduced portion and the difference thereof on the display section  406 . 
   In step S 512 , the UI section  404  prompts the user to select a normal reproduction mode or summary reproduction mode. If the user selects the normal reproduction mode, the process in step S 505  is executed. On the other hand, if the user selects the summary reproduction mode, the process in step S 513  is executed. 
   If the summary reproduction mode is selected, the UI section  404  prompts the user to select one of summary schemes in step S 513 . In step S 513 , for example, the summary scheme can be selected from the summary systems 1 to 4 explained in the above-described first embodiment. 
   In step S 514 , the reproduction control section  403  generates summary data which is a summary of the selected data based on the summary scheme selected by the user. At this time, the reproduction control section  403  makes sure that the total power consumption of the summary data is smaller than the current remaining power Pb of the battery  400 . If the time taken to generate the summary data is long, the remaining power of the battery  400  may reduce drastically. Thus, upon generating the summary data, the reproduction apparatus  40  according to the fourth embodiment re-detects the remaining power of the battery  400  at predetermined intervals and compares it with the total power consumption of the summary data. 
   In step S 515 , the reproduction control section  403  starts to reproduce the summary data. Unlike the reproduction apparatus  40  of the third embodiment, the reproduction apparatus  40  of the fourth embodiment does not restrict operations other than stop (fast rewind, fast forward, pause, etc.) after reproduction of the summary data is started. Thus, if these operations are carried out during reproduction, the remaining power of the battery may be not enough to reproduce all summary data. Operations in and after step S 516  will be carried out to handle such a case. 
   In step S 516 , the reproduction control section  403  decides whether the reproduction of the summary data is completed or not. 
   If the reproduction of the summary data is not completed (NO in step S 516 ), the process moves on to step S 517  and the reproduction control section  403  makes the prediction section  402  predict power consumption Prs of the unreproduced portion of the summary data. The prediction section  402  predicts the power consumption Prs of the unreproduced portion and notifies it to the reproduction control section  403 . 
   In step S 518 , the reproduction control section  403  makes the detection section  401  detect the current remaining power Pb of the battery  400 . The detection section  401  detects the current remaining power Pb of the battery  400  and notifies it to the reproduction control section  403 . 
   In step S 519 , the reproduction control section  403  decides whether the current remaining power Pb of the battery  400  is greater than the power consumption Prs or not. This decision corresponds to a decision as to whether the summary data can be reproduced to the end or not. If the current remaining power Pb of the battery  400  is greater than the power consumption Prs (YES in step S 519 ), the process moves back to step S 516  and the reproduction control section  403  continues to reproduce the summary data. 
   If the current remaining power Pb of the battery  400  is not greater than the power consumption Prs (NO in step S 519 ), the summary data cannot be reproduced to the end. In this case, the process moves on to step S 520  and the reproduction control section  403  changes the content of the summary data. Then, after changing the content of the summary data, the reproduction control section  403  starts to reproduce the changed summary data. If video data is found in the summary data, the reproduction control section  403  processes it and supplies it to the display section  406  and if audio data is found in the summary data, the reproduction control section  403  processes it and supplies it to the speaker section  407 . 
   As described above, the reproduction apparatus  40  according to the fourth embodiment can perform reproduction processing in consideration of the remaining power of the battery  400 . Furthermore, when the remaining power of the battery  400  is not enough to reproduce the digital data selected by the user to the end, the reproduction apparatus  40  according to the fourth embodiment can warn the user of it. In accordance with the reproduction apparatus  40  according to the fourth embodiment, there is no need to restrict operations such as fast rewind, fast forward, pause even in the summary reproduction mode. 
   Other Embodiment 
   Further, the object of the present invention can also be achieved by providing a storage medium storing program codes for performing the aforesaid processes to a computer system or apparatus (e.g., a personal computer), reading the program codes, by a CPU or MPU of the computer system or apparatus, from the storage medium, then executing the program. 
   In this case, the program codes read from the storage medium realize the functions according to the embodiments, and the storage medium storing the program codes constitutes the invention. 
   Further, the storage medium, such as a floppy disk, a hard disk, an optical disk, a magneto-optical disk, CD-ROM, CD-R, a magnetic tape, a non-volatile type memory card, and ROM, and computer network, such as LAN (local area network) and WAN (wide area network), can be used for providing the program codes. 
   Furthermore, besides aforesaid functions according to the above embodiments are realized by executing the program codes which are read by a computer, the present invention includes a case where an OS (operating system) or the like working on the computer performs a part or entire processes in accordance with designations of the program codes and realizes functions according to the above embodiments. 
   Furthermore, the present invention also includes a case where, after the program codes read from the storage medium are written in a function expansion card which is inserted into the computer or in a memory provided in a function expansion unit which is connected to the computer, CPU or the like contained in the function expansion card or unit performs a part or entire process in accordance with designations of the program codes and realizes functions of the above embodiments. 
   In a case where the present invention is applied to the aforesaid storage medium, the storage medium stores program codes corresponding to the flowchart shown in any one of  FIGS. 2 ,  3 ,  5  and  6  described in the embodiments. 
   The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore to apprise the public of the scope of the present invention, the following claims are made.