Abstract:
In the case where metadata refers to relevant content on a network, since the relevant content on the network can not be necessarily permanently held, it is desirable that a time limit for making reference can be set. Besides, in order to provide relevant content which can be referred to only in a limited period for promoting sales, or in order to provide relevant content which can be referred to only in a limited period such as, for example, Christmas Day every year for raising the entertainingness of the metadata, it is desirable that a reference time limit of the relevant content can be set. Then, in order to set an effective time limit of an access unit, a flag to specify the effective time limit and the effective time limit are described in each access unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2004-226162, filed on 2, Aug. 2004; the entire contents of which are incorporated herein by reference. 
   TECHNICAL FIELD 
   The present invention relates to a method in which a moving image hypermedia is realized by combining moving image data existing in a client apparatus and metadata existing in the client apparatus or a server apparatus on a network, and a telop or a balloon is displayed on a moving image. In particular, the invention relates to a method in which an effective time limit can be specified in a telop or a balloon. 
   BACKGROUND OF THE INVENTION 
   A hypermedia is such that a connection called a hyperlink is defined between media such as moving images, still images, audios and texts, and reference can be made mutually or from one to another. For example, in a homepage described in HTML which can be browsed using the Internet, texts and still pictures are arranged, and links are defined throughout the texts and the still pictures. When the link is specified, relevant information as a link destination can be immediately displayed. When an interesting expression is directly specified, access can be made to relevant information, and therefore, the operation is easy and intuitive. 
   On the other hand, in a hypermedia in which moving images, not texts and still pictures, are main, there is defined a link from an object, such as a person or a thing, appearing on the moving image to relevant content, such as a text or a still picture, for explaining it, and when a viewer specifies this object, the relevant content is displayed. At this time, in order to define the link between a spatio-temporal region of the object appearing on the moving image and its relevant content, data (object area data) expressing the spatio-temporal region of the object in the moving image is required. 
   As the object area data, it is possible to use a mask image series having a value of a binary value or higher, arbitrary shape coding of MPEG-4, a method of describing a trajectory of a feature point of a figure explained in patent document 1 (JP-A-2000-285253), a method explained in patent document 2 (JP-A-2001-111996), and the like. In order to realize the hypermedia in which the moving image is main, in addition to this, data (operation information) describing an operation to display other relevant content when an object is specified, and the like are required. These data other than the moving image are called metadata. 
   As a method of providing a moving image and metadata to a viewer, first, there is a method of producing a recording medium (video CD, DVD, etc.) in which both the moving image and the metadata are recorded. Besides, in order to provide the metadata of the moving image which has already been owned as a video CD or a DVD, only the metadata may be downloaded from a network or delivered by streaming. Further, both data of the moving image and the metadata may be delivered through a network. At this time, it is desirable that the metadata has such a format as to be capable of efficiently using a buffer, to be suitable for random access, and to be resistant to data loss in the network. 
   In the case where switching of the moving image frequently occurs (for example, in the case where moving images taken in plural camera angles are prepared, and the viewer can freely select the camera angle, such as a multi-angle video of a DVD video), the metadata must be switched at high rate correspondingly to the switching of the moving image. 
   Further, in the case where the metadata refers to relevant content on a network, since the relevant content on the network can not be necessarily permanently held, it is desirable that a time limit for making reference can be set. Besides, in order to provide relevant content which can be referred to only in a limited period for promoting sales, or in order to provide relevant content which can be referred to in a specific limited period such as, for example, Christmas Day every year for raising the entertainingness of the metadata, it is desirable that a reference time limit of the relevant content can be set. 
   In the metadata relevant to a moving image owned by a viewer and delivered by streaming to the viewer through the network, or in the metadata owned by the viewer and reproduced, it is desirable that the effective time limit of the metadata can be set. 
   The invention has been made to solve the above problems. 
   BRIEF SUMMARY OF THE INVENTION 
   Metadata relevant to a moving image includes one or plural access units each being a data unit which can be independently processed. Here, the access unit (Vclick_AU of  FIG. 4 ) includes, as information relating to an effective period defined with respect to a time axis of the moving image, first data ( 402 ) to specify the effective period, object area data ( 400 ) describing a spatio-temporal region in the moving image, and second data ( 403 ) including at least one of data to specify a display method relevant to the spatio-temporal region and data to specify a processing to be performed when the spatio-temporal region is specified. 
   According to an embodiment of the invention, the metadata includes third data to specify an effective time limit which is expressed in absolute time and in which the metadata can be reproduced, and in a case where an instruction to reproduce the metadata is issued, when the absolute time is within the effective time limit specified by the third data, the metadata is reproduced. 
   Besides, each of the access units includes fourth data to specify an effective time limit which is expressed in absolute time and in which the access unit can be reproduced, and in a case where an instruction to reproduce the access unit is issued, when the absolute time is within the effective time limit specified by the fourth data, the access unit is reproduced. 
   Further, data to manage the metadata includes fifth data to express an effective time limit which is expressed in absolute time and in which the metadata can be reproduced, and in a case where an instruction to reproduce the metadata is issued, when the absolute time is within the effective time limit specified by the fifth data, the metadata is reproduced. 
   When the effective time limit of the metadata or the access unit can be specified, since the timing when the relevant content on the network is provided can be known, an access error does not occur. Besides, since the relevant content which can be referred to only in a limited period can be provided, the invention can be used for sales promotion in a limited period, and provision of metadata including an operation in a limited period and having high entertainingness. 
   Further, when the effective time limit can be specified in the metadata, the expiration time of all access units can be set at the same time, or a new Vclick stream can be made to be periodically downloaded. When the effective time limit can be specified in the access unit, selective setting of the effective time limit can be performed, for example, the effective time limit is specified in only the relevant content on the network, and the effective time limit is not set in the relevant content in the same storage medium as the moving image. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  are views for explaining a display example of a hypermedia according to an embodiment of the invention. 
       FIG. 2  is a block diagram showing a structural example of a system according to an embodiment of the invention. 
       FIG. 3  is a view for explaining a relation between an object area and object area data according to an embodiment of the invention. 
       FIG. 4  is a view for explaining an example of a data structure of an access unit of object metadata according to an embodiment of the invention. 
       FIG. 5  is a view for explaining a construction method of a Vclick stream according to an embodiment of the invention. 
       FIG. 6  is a view for explaining a structural example of a Vclick access table according to an embodiment of the invention. 
       FIG. 7  is a view for explaining a structural example of a transmission packet according to an embodiment of the invention. 
       FIG. 8  is a view for explaining another structural example of a transmission packet according to an embodiment of the invention. 
       FIG. 9  is a view for explaining an example of communication between a server and a client according to an embodiment of the invention. 
       FIG. 10  is a view for explaining another example of communication between a server and a client according to an embodiment of the invention. 
       FIG. 11  is a view for explaining an example of data elements of a header of a Vclick stream according to an embodiment of the invention. 
       FIG. 12  is a view for explaining an example of data elements of a header of a Vclick access unit (AU) according to an embodiment of the invention. 
       FIG. 13  is a view for explaining an example of data elements of a time stamp of the Vclick access unit (AU) according to an embodiment of the invention. 
       FIG. 14  is a view for explaining an example of data elements of a time stamp skip of the Vclick access unit (AU) according to an embodiment of the invention. 
       FIG. 15  is a view for explaining an example of data elements of object attribute information according to an embodiment of the invention. 
       FIG. 16  is a view for explaining an example of kinds of the object attribute information according to an embodiment of the invention. 
       FIG. 17  is a view for explaining an example of data elements of a name attribute of an object according to an embodiment of the invention. 
       FIG. 18  is a view for explaining an example of data elements of an action attribute of the object according to an embodiment of the invention. 
       FIG. 19  is a view for explaining an example of data elements of a contour attribute of the object according to an embodiment of the invention. 
       FIG. 20  is a view for explaining an example of data elements of a blinking area attribute of the object according to an embodiment of the invention. 
       FIG. 21  is a view for explaining an example of data elements of a mosaic area attribute of the object according to an embodiment of the invention. 
       FIG. 22  is a view for explaining an example of data elements of a filled-in area attribute of the object according to an embodiment of the invention. 
       FIG. 23  is a view for explaining an example of data elements of text information data of the object according to an embodiment of the invention. 
       FIG. 24  is a view for explaining an example of data elements of a text attribute of the object according to an embodiment of the invention. 
       FIG. 25  is a view for explaining an example of data elements of a text highlight effect attribute of the object according to an embodiment of the invention. 
       FIG. 26  is a view for explaining an example of data elements of an entry of the text highlight effect attribute of the object according to an embodiment of the invention. 
       FIG. 27  is a view for explaining an example of data elements of a text blinking effect attribute of the object according to an embodiment of the invention. 
       FIG. 28  is a view for explaining an example of data elements of an entry of the text blinking effect attribute of the object according to an embodiment of the invention. 
       FIG. 29  is a view for explaining an example of data elements of a text scroll effect attribute of the object according to an embodiment of the invention. 
       FIG. 30  is a view for explaining an example of data elements of a text karaoke effect attribute of the object according to an embodiment of the invention. 
       FIG. 31  is a view for explaining an example of data elements of an entry of the text karaoke effect attribute of the object according to an embodiment of the invention. 
       FIG. 32  is a view for explaining an example of data elements of layer attribute extension of the object according to an embodiment of the invention. 
       FIG. 33  is a view for explaining an example of data elements of an entry of the layer attribute extension of the object according to an embodiment of the invention. 
       FIG. 34  is a view for explaining an example of data elements of object area data of a Vclick access unit (AU) according to an embodiment of the invention. 
       FIG. 35  is a view for explaining an example of a structure of an enhanced DVD video disk according to an embodiment of the invention. 
       FIG. 36  is a view for explaining an example of a directory structure in the enhanced DVD video disk according to an embodiment of the invention. 
       FIG. 37  is a flowchart (in a case where Vclick data is in a server apparatus) showing a start processing procedure of normal reproduction according to an embodiment of the invention. 
       FIG. 38  is a flowchart (in a case where Vclick data is in a server apparatus) showing another start processing procedure of normal reproduction according to an embodiment of the invention. 
       FIG. 39  is a flowchart (in a case where Vclick data is in a server apparatus) showing an end processing procedure of normal reproduction according to an embodiment of the invention. 
       FIG. 40  is a flowchart (in a case where Vclick data is in a server apparatus) showing a start processing procedure of random access reproduction according to an embodiment of the invention. 
       FIG. 41  is a flowchart (in a case where Vclick data is in a server apparatus) showing another start processing procedure of random access reproduction according to an embodiment of the invention. 
       FIG. 42  is a flowchart (in a case where Vclick data is in a client apparatus) showing a start processing procedure of normal reproduction according to an embodiment of the invention. 
       FIG. 43  is a flowchart (in a case where Vclick data is in a client apparatus) showing a start processing procedure of random access reproduction according to an embodiment of the invention. 
       FIG. 44  is a view for explaining a display example of a hypermedia according to an embodiment of the invention. 
       FIG. 45  is a view for explaining an example in which an effective time limit is set in a Vclick access unit (AU) according to an embodiment of the invention. 
       FIG. 46  is a view for explaining an example of an effective time limit of a Vclick AU according to an embodiment of the invention. 
       FIG. 47  is a view for explaining a data structure of a Vclick stream in which an effective time limit can be set according to an embodiment of the invention. 
       FIG. 48  is a view for explaining an example of a data structure of an object effective time limit according to an embodiment of the invention. 
       FIG. 49  is a view for explaining an example of a data structure of a time limit attribute of an object effective time limit according to an embodiment of the invention. 
       FIG. 50  is a flowchart for explaining a procedure to judge an effective time limit of a Vclick AU according to an embodiment of the invention. 
       FIG. 51  is a view for explaining an example of a data structure of an effective time limit of a Vclcik stream according to an embodiment of the invention. 
       FIG. 52  is a view for explaining a procedure to judge an effective time limit of a Vclcik stream according to an embodiment of the invention. 
       FIG. 53  is a view for explaining a semantic structure of a time limit attribute of an effective time limit of a Vclick AU according to an embodiment of the invention. 
       FIG. 54  is a view showing an example of a Vclick information file of an effective time limit of a Vclick stream according to a second embodiment of the invention. 
       FIG. 55  is a view showing a structural example of a Vclick information file according to an embodiment of the invention. 
       FIG. 56  is a view showing a structural example of a Vclick information file according to an embodiment of the invention. 
       FIG. 57  is a view showing a structural example of a Vclick information file according to an embodiment of the invention. 
       FIG. 58  is a view showing a relation between a Vclick stream according to an embodiment of the invention and DVD video content. 
       FIG. 59  is a view showing another example of a Vclick information file according to an embodiment of the invention. 
       FIG. 60  is a view showing a still another example of a Vclick information file according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
   (1) Outline of Application 
     FIG. 1  shows a display example, on a screen, of an application (moving image hypermedia) realized by using object metadata of this embodiment together with a moving image. 
   Reference numeral  100  of  FIG. 1A  denotes a reproduction screen of a moving image; and  101 , a mouse cursor. Data of the moving image reproduced on the reproduction screen  100  of the moving image is recorded on a local moving image data recording medium. Reference numeral  102  denotes an area of an object appearing on the moving image. When the user moves the mouse cursor into the area of the object and selects the object by clicking or the like, a specified function is executed. For example, in  FIG. 1B , a document (information relating to the clicked object)  103  on the local disk and/or a network is displayed. In addition, it is possible to perform such functions as to jump to another scene of the moving image, as to reproduce another moving image file, and as to change a reproduction mode. 
   The data of the area  102  of the object, the operation data of a client apparatus in the case where this area is specified by clicking or the like, and the like will be collectively referred to as object metadata or Vclick data. The Vclick data may be recorded, together with the moving image data, on a local moving image data recording medium (optical disk, hard disk, semiconductor memory, etc.), or may be stored in a server on a network and transmitted to a client through the network. 
     FIG. 44  shows a display example, on a screen different from  FIG. 1 , of an application (moving image hypermedia) realized by using the Vclick data of this embodiment together with the moving image. In  FIG. 1 , windows on which the moving image and the relevant information are displayed are separate from each other, however, in  FIG. 44 , a moving image A 02  and a relevant information A 03  are displayed on one window A 01 . As the relevant information, not only a text, but also a still picture A 04  and a moving image different from A 02  can be displayed. 
   Hereinafter, a detailed description will be given to how to realize the application. 
   (2) System Structure 
     FIG. 2  is a view showing a rough structure of a streaming apparatus (network-capable disk player) according to an embodiment of the invention. Functions of respective structural elements will be described by use of  FIG. 2 . 
   Reference numeral  200  denotes a client apparatus;  201 , a server apparatus; and  221 , a network connecting the server apparatus and the client apparatus. The client apparatus  200  includes a motion picture reproduction engine  203 , a Vclick engine  202 , a disk device  230 , a user interface  240 , a network manager  208 , and a disk device manager  213 . Reference numerals  204  to  206  denote devices included in the motion picture reproduction engine;  207 ,  209  to  212 , and  214  to  218 , devices included in the Vclick engine; and  219  and  220 , devices included in the server apparatus. The client apparatus  200  can reproduce moving image data existing in the disk device  230 , and display documents described in markup language such as HTML. It is also possible to display documents in HTML or the like existing on the network. With respect to the Vclick data relating to the moving image data recorded on a moving image data recording medium  231 , there is a case where the data, together with the moving image data, is recorded on the moving image data recording medium  231 , and there is a case where the data is recorded on a metadata recording medium  219  of the server apparatus  201 . In the case where the Vclick data exists in the server apparatus  201 , the client apparatus  200  can perform reproduction using the Vclick data and the moving image data in the disk device  230  in a manner as described below. First, in response to a request from the client apparatus  200 , the server apparatus  201  transmits media data M 1  including the Vclick data to the client apparatus  200  through the network  221 . The client apparatus  200  processes the transmitted Vclick data in synchronization with the reproduction of the moving image, and realizes additional functions such as a hypermedia. 
   The motion picture reproduction engine  203  is an engine for reproducing the moving image data existing in the disk device  230 , and includes the devices  204 ,  205  and  206 . Reference numeral  231  denotes a moving image data recording medium, and specifically denotes a DVD, a video CD, a video tape, a hard disk, a semiconductor memory or the like. Digital and/or analog moving image data are recorded on the moving image data recording medium  231 . There is also a case where metadata relating to the moving image data, together with the moving image data, is recorded on the moving image data recording medium  231 . Reference numeral  205  denotes a controller for moving image reproduction control and is constructed so as to be capable of controlling reproduction of video/audio/sub-video data D 1  from the moving image data recording medium  231  according to a “control” signal outputted from the interface handler  207  of the Vclick engine  202 . 
   Specifically, at the time of reproduction of the moving image, according to the “control” signal transmitted from the interface handler  207  when an event (for example, menu call or title jump by user instructions) occurs, the moving image reproduction controller  205  can output a “trigger” signal indicating the reproduction state of the video/audio/sub-video data D 1  to the interface handler  207 . At that time (simultaneously with the output of the trigger signal, or at a suitable timing before or after that), the moving image reproduction controller  205  can output a “status” signal indicating property information (for example, audio language set in a player, sub-video subtitle language, reproduction operation, reproduction position, various time information, content of a disk, etc.) to the interface handler  207 . By the transmission/reception of these signals, it becomes possible to start and stop readout of the moving image data and to access a desired position in the moving image data. 
   The AV decoder  206  has functions to decode the video data, audio data and sub-video data recorded on the moving image data recording medium  231 , and to output the decoded video data (obtained by synthesizing the foregoing video data and the foregoing sub-video data) and the audio data, respectively. By this, the motion picture reproduction engine  203  has the same function as a reproduction engine of a normal DVD video player manufactured based on existing DVD video standards. That is, the client apparatus  200  of  FIG. 2  can reproduce data, such as video and audio, of an MPEG 2 program stream structure similarly to a normal DVD video player, and by this, it becomes possible to reproduce an existing DVD video disk (disk in conformity with the conventional DVD video standards) (reproduction compatibility with existing DVD software is guaranteed). 
   The interface handler  207  performs interface control between modules such as the motion picture reproduction engine  203 , the disk device manager  213 , the network manager  208 , the metadata manager  210 , the buffer manager  211 , the script interpreter  212 , the media decoder  216  (including the metadata decoder  217 ), the layout manager  215 , and the AV render  218 . Besides, an input event by a user operation (operation to an input device such as a mouse, touch panel, or a keyboard) is received from the user interface  240 , and the event is transmitted to a suitable module. 
   The interface handler  207  includes an access table parser to interpret a Vclick access table (described later), an information file parser to interpret a Vclick information file (described later), a property buffer to record properties managed by the Vclick engine, a system clock of the Vclick engine, a moving image clock in which a clock of the moving image clock  204  in the motion picture reproduction engine is copied, and the like. 
   The network manager  208  has a function to acquire documents in HTML or the like and data such as still pictures and audios into the buffer  209  through the network, and controls the operation of an internet connection part  222 . When instructions of connection or disconnection to the network are issued by the user operation or by the interface handler  207  receiving a request from the metadata manager  210 , the network manager  208  switches between connection and disconnection of the internet connection part  222 . Besides, when the network is established between the server apparatus  201  and the internet connection part  222 , transmission/reception of the media data such as control data and Vclick data is performed. The media data includes the Vclick data, documents in HTML or the like, still picture and moving image data accompanying this, and the like. 
   Data transmitted from the client apparatus  200  to the server apparatus  201  include a request for session configuration, a request for session end, a request for transmission of metadata such as Vclick data, and status information such as an OK or an error. Besides, transmission of the state information of the client apparatus may be performed. On the other hand, data transmitted from the server apparatus to the client apparatus include the metadata such as the Vclick data, and the status information such as an OK or an error. 
   The disk device manager  213  has a function to acquire documents in HTML or the like and data such as still pictures and audios into the buffer  209 , and a function to transmit the video/audio/sub-video data D 1  to the motion picture reproduction engine  203 . The disk device manager  213  performs data transmission processing in accordance with the instructions from the metadata manager  210 . 
   The buffer  209  temporarily stores the media data M 1  such as the Vclick data transmitted from the server apparatus  201  through the network (via the network manager). Also in the case where media data M 2  is recorded on the moving image data recording medium  231 , the media data M 2  is similarly stored in the buffer  209  through the disk device manager. 
   In the case where the media data M 2  is recorded on the moving image data recording medium  231 , before the video/audio/sub-video data D 1  is reproduced, the media data M 2  is previously read out of the moving image data recording medium  231  and may be stored in the buffer  209 . This becomes a measure to avoid a following disadvantage. That is, since a data storage position of the media data M 2  on the moving image data recording medium  231  is different from that of the video/audio/sub-video data D 1 , in the case where normal reproduction is performed, a seek or the like of the disk occurs and seamless reproduction can not be ensured. 
   As stated above, the media data M 1  such as the Vclick data downloaded from the server apparatus  201  is also stored in the buffer  209  similarly to the media data M 2  such as the Vclick data recorded on the moving image data storage medium  231 , so that it becomes possible to read and reproduce the video/audio/sub-video data D 1  and the media data simultaneously. 
   Incidentally, the storage capacity of the buffer  209  has a limit. That is, the data size of the media data M 1  and M 2  which can be stored in the buffer  209  is limited. Thus, unnecessary data may be erased by the control (buffer control) of the metadata manager  210  and/or the buffer manager  211 . 
   The metadata manager  210  manages the metadata stored in the buffer  209 , and receives a suitable timing (“moving image clock” signal) synchronous to the reproduction of the moving image from the interface handler  207  and transfers the metadata having a pertinent time stamp from the buffer  209  to the media decoder  216 . 
   Incidentally, in the case where the Vclick data having the pertinent time stamp does not exist in the buffer  209 , transfer to the media decoder  216  may not be performed. The metadata manager  210  performs control to read data with a size of the Vclick data transmitted from the buffer  209  or an arbitrary size from the server apparatus  201  or the disk device  230  to the buffer  209 . As a specific processing, the metadata manager  210  issues an acquisition request for Vclick data with a specified size to the network manager  208  or the disk device manager  213  via the interface handler  207 . The network manager  208  or the disk device manager  213  reads the Vclick data with the specified size into the buffer  209 , and notifies, via the interface handler  207 , the metadata manager  210  that the Vclick data has been acquired. 
   The buffer manager  211  manages data (documents in HTML or the like, still picture and moving image data accompanying this, etc.) other than the Vclick data stored in the buffer  209 , receives a suitable timing (“moving image clock” signal) synchronous to the reproduction of moving images from the interface handler  207 , and transmits the data other than the Vclick data stored in the buffer  209  to the parser  214  or the media decoder  216 . The buffer manager  211  may delete data which becomes unnecessary from the buffer  209 . 
   The parser  214  performs parsing of documents written in markup language such as HTML, transmits a script to the script interpreter  212  and transmits information relating to a layout to the layout manager  215 . 
   The script interpreter  212  interprets the script inputted from the parser  214  and executes it. In the execution of the script, an event inputted from the interface handler  207  and information of properties can also be used. In the case where an object in the moving image is specified by the user, the script is inputted from the metadata decoder  217  to the script interpreter  212 . 
   The AV renderer  218  has a function to control video/audio/text output. Specifically, according to a “layout control” signal outputted from the layout manager  215 , the AV renderer  218  controls, for example, a display position and a display size of video and text (in addition to these, a display timing and a display time may be included), and the loudness of an audio (in addition to this, an output timing and an output time may be included), and according to the kind of the specified motor and/or the kind of the video to be displayed, pixel conversion of the video is performed. The video/audio/text output as the object of the control is the output from the motion picture reproduction engine  203  and the media decoder  216 . Further, the AV renderer  218  has a function to control mixing and switching of the video/audio data inputted from the motion picture reproduction engine  203  and the video/audio/text data inputted from the media decoder in accordance with an “AV output control” signal outputted from the interface handler  207 . 
   The layout manager  215  outputs the “layout control” signal to the AV renderer  218 . The “layout control” signal includes information relating to the size and position of the motion picture/still picture/text to be outputted (information relating to a display time such as a display start/end/continuation may be included), and is information to instruct the AV renderer  218  on the selection of a layout in which a display is carried out. Besides, with respect to the input information, such as clicking by the user, inputted from the interface handler  207 , it is judged which object has been specified, and an instruction is given to the metadata decoder  217  to extract an operation instruction, such as displaying of relevant information, defined for the specified object. The extracted operation instruction is transmitted to the script interpreter  212  and is executed. 
   The media decoder  216  (including the metadata decoder) decodes the motion picture/still picture/text data. The decoded video data and text image data are transmitted from the media decoder  216  to the AV renderer  218 . Besides, the decode data are decoded by the instruction of the “media control” signal from the interface handler  202 , and are decoded in synchronization with the “timing” signal from the interface handler  202 . 
   Reference numeral  219  denotes the metadata recording medium of the server apparatus, and is a hard disk, a semiconductor memory, a magnetic tape or the like on which the Vclick data to be transmitted to the client apparatus  200  is recorded. The Vclick data is the metadata relating to the moving image data recorded on the moving image data recording medium  231 . The Vclick data includes object metadata described later. Reference numeral  220  denotes the network manager of the server, and performs transmission/reception of data to/from the client apparatus  200  through the network  221 . 
   (3) EDVD Data Structure and IFO File 
     FIG. 35  is a view showing an example of a data structure at a time when an enhanced DVD video disk is used as the moving image data recording medium  231 . A DVD video area of the enhanced DVD video disk stores DVD video content (having an MPEG2 program stream structure) of the same data structure as DVD video standards. Further, an other recording area of the enhanced DVD video disk stores enhanced navigation (hereinafter abbreviated to ENAV) content which can enrich the reproduction of the video content. Incidentally, the existence of the above recording area is also accepted in the DVD video standards. 
   Here, the basic data structure of the DVD video disk will be described. That is, the recording area of the DVD video disk includes a lead-in area, a volume space and a lead-out area in sequence from the inner periphery. The volume space includes a volume/file structure information area and the DVD video area (DVD video zone), and can further include the other recording areas (DVD other zone) optionally. 
   The volume/file structure information area  2  is an area assigned for a UDF (Universal Disk Format) bridge structure. A volume of a UDF bridge format is recognized in accordance with part  2  of ISO/IEC13346. A space in which the volume is recognized is made up of continuous sectors, and starts from the first logical sector of the volume space of  FIG. 35 . The first 16 logical sectors are preserved for system use regulated by ISO9660. In order to guarantee the compatibility with the conventional DVD video standards, the volume/file structure information area with such contents becomes necessary. 
   Besides, management information called a video manager VMG, and at least one video content called video title set VTS (VTS#1 to VTS#n) are recorded in the DVD video area. The VMG is the management information for all video title sets VTS existing in the DVD video area, and includes control data VMG 1 , VMG menu data VMGM_VOBS (option) and backup data of VMG. Besides, each video title set VTS includes control data VTSI of the VTS, VTS menu data VTSM_VOMS (option), data VTSTT_VOBS of content (movie, etc.) of the VTS (title), and backup data of the VTSI. In order to guarantee the compatibility with the conventional DVD video standards, the DVD video area with such contents also becomes necessary. 
   Reproduction selection menu and the like of each title (VTS#1 to VTS#n) is previously given using the VMG by a provider (producer of the DVD video disk). A reproduction chapter selection menu in a specific title (for example, VTS#1), a reproduction procedure of recording content (cell) and the like are previously given using the VTSI by the provider. Accordingly, a viewer (user of the DVD video player) of the disk can enjoy the recorded content of the disk  1  in accordance with the menu of the VMG/VTSI previously prepared by the provider and the reproduction control information (program chain information PGCI) in the VTSI. However, in the DVD video standards, the viewer (user) can not reproduce the content (movie or music) of the VTS by a method different from the VMG/VTSI prepared by the provider. 
   The enhanced DVD video disk of  FIG. 35  is prepared for such contrivance as to enable the reproduction of the content (movie or music) of the VTS by a method different from the VMG/VTSI prepared by the provider and as to enable addition and reproduction of content different from the VMG/VTSI prepared by the provider. The ENAV content included in this disk can not be accessed by the DVD video player manufactured on the basis of the DVD video standards (even if it is accessed, the content can not be used), however, it can be accessed by the DVD video player according to the embodiment of the invention, and the reproduced content can be used. 
   The ENAV content is constructed to include data such as an audio, still picture, font and text, motion picture, animation and Vclick data, and an ENAV document (this is described in Markup/Script language) as information to control the reproduction of these. In the information to control the reproduction, a reproduction method (display method, reproduction procedure, reproduction switching procedure, selection of reproduction object, etc.) of the ENAV content (including audio, still picture, font/text, motion picture, animation, Vclick data and the like) and/or the DVD video content is described in markup language or Script language. For example, HTML (Hyper Text Markup Language)/XHTML (extensible Hyper Text Markup language) or SMIL (Synchronized Multimedia Integration Language) as the Markup language, and ECMA (European Computer Manufactures Association) Script or Java Scrip as the Script language can be used while they are combined. 
   Here, in the enhanced DVD video disk of  FIG. 35 , since the content other than that of the other recording area complies with the DVD video standards, even if an already popular DVD video player is used, the video content recorded in the DVD video area can be reproduced (that is, it is compatible with a conventional DVD video disk). Although the ENAV content recorded in the other recording area can not be reproduced by the conventional DVD video player (or can not be used), it can be reproduced and used by the DVD video player according to the embodiment of the invention. Accordingly, when the DVD video player according to the embodiment of the invention is used and the ENAV content is reproduced, the video reproduction rich in variety becomes possible without being limited only to the content of the VMG/VTSI previously prepared by the provider. 
   Especially, as shown in  FIG. 35 , the ENAV content includes the Vclick data, and the Vclick data is constructed to include a Vclick information file (Vclick info), a Vclick access table, a Vclick stream, a Vclick information file backup (Vclick info backup), and a Vclick access table backup. 
   The Vclick information file is data indicating that an after-mentioned Vclick stream is added to which part of the DVD video content (for example, the whole title of the DVD video content, the whole chapter, or a part thereof). The Vclick access table exists for each of the after-mentioned Vclick streams, and is a table for accessing the Vclick stream. The Vclick stream is a stream including position information of an object in a moving image and data such as an operation description at a time when the object is clicked. The Vclick information file backup is the backup of the foregoing Vclick information file, and always has the same content as the Vclick information file. The Vclick access table backup is the backup of the foregoing Vclick access table, and always has the same content as the Vclick access table. In the example of  FIG. 35 , the Vclick data is recorded on the enhanced DVD video disk. However, as described before, there is also a case where the Vclick data is placed in the server apparatus on the network. 
     FIG. 36  shows an example of files constituting the Vclick information file, the Vclick access table, the Vclick stream, the Vclick information file backup, and the Vclick access table backup. The file (VCKINDEX.IFO) constituting the Vclick information file is described in XML (Extensible Markup Language) language, and the Vclick stream and position information (VTS number, title number, PGC number, etc.) of the DVD video content to which the Vclick stream is added are described. The Vclick access table is constructed of one or more files (VCKSTR01.IFO to VCKSTR99.IFO, or arbitrary file names), and one access table file corresponds to one Vclick stream. 
   The relation between position information (relative byte size from the head of a file) of the Vclick stream and time information (time stamp of the corresponding moving image or relative time information from the head of the file) is described in the Vclick stream file, and a reproduction start position corresponding to a given time can be retrieved. 
   The Vclick stream is constructed of one or more files (VCKSTR01.VCK to VCKSTR99.VCK or arbitrary file names) and can be reproduced, together with the added DVD video content, by referring to the description of the Vclick information file. In the case where plural attributes exist (for example, Vclick data for Japanese and Vclick data for English, etc.), it is also possible to construct the Vclick stream different for each of the attributes, that is, different files. Further, the respective attributes are multiplexed, and one Vclick stream, that is, one file can be constructed. Incidentally, in the case of the former (the different attributes are constructed of the plural Vclick streams), buffer occupation capacity at the time when it is once stored in a reproducing apparatus (player) can be decreased. In the case of the latter (the different attributes are constructed of one Vclick stream), when the attribute is switched, since the one file may be kept being reproduced without switching the file, the switching rate can be made high. 
   Here, the association of the Vclick stream and the Vclick access table can be performed by, for example, the file name. In the foregoing example, one Vclick access table (VCKSTRXX.IFO, XX is 01 to 99) is assigned to one Vclick stream (VCKSTRXX.VCK, XX OS 01 TO  99 ), and when the file names except extensions are made identical to each other, the association of the Vclick stream and the Vclick access table becomes recognizable. 
   In addition to this, when the association of the Vclick stream and the Vclick access table is described in the Vclick information file (described in parallel), the association of the Vclick stream and the Vclick access table becomes recognizable. 
   The Vclick information file backup is constructed of a VCKINDEX.BUP file, and has quite the same content as the Vclick information file (VCKINDEX.IFO). In the case where the VCKINDEX.IFO can not be read because of some reason (because of scratch, dust or the like of the disk), the VCKINDEX.BUP is read instead, so that a desired procedure can be performed. The Vclick access table backup is constructed of VCKSTR01.BUP to VCKSTR99.BUP files, and has quite the same content as the Vclick access table (VCKSTR01.IFO to VCKSTR99.IFO). One Vclick access table backup (VCKSTRXX.BUP, XX is 01 to 99) is assigned to one Vclick access table (VCKSTRXX.IFO, XX is 01 to 99), and when the file names except the extensions are identical to each other, the association of the Vclick access table and the Vclick access table backup becomes recognizable. In the case where the VCKSTRXX.IFO can not be read because of some reason (because of scratch, dust or the like of the disk), the VCKSTRXX.BUP is read instead, so that a desired procedure can be performed. 
   (4) Structural Example of Vclick Information File 
     FIGS. 55 to 57  show a structural example of a Vclick information file. 
   The Vclick information file is written in XML language, and at first, it is declared that the language is the XML language, and next, it is declared that this is the Vclick information file written in the XML language. Further, the contents of the Vclick information file are described using a &lt;vclickinfo&gt; tag. 
   The area of &lt;vclickinfo&gt; includes 0 or 1&lt;vmg&gt; tag, and 0 or 1 or more &lt;vts&gt; tag. The area of &lt;vmg&gt; expresses a VMG space in DVD video, and it is expressed that a Vclick stream described in the area of &lt;vmg&gt; is added to the DVD video data of the VMG space. Besides, the area of &lt;vts&gt; expresses a VTS space in the DVD video, and the number of the VTS space is specified by adding a num attribute into the &lt;vts&gt; tag. For example, &lt;vts num=“n”&gt; indicates an nth VTS space. It is expressed that a Vclick stream described in the area of &lt;vts num=“n”&gt; is added to the DVD video data constituting the nth VTS space. 
   The area of &lt;vmg&gt; includes 0 or 1 or more &lt;vmgm&gt; tag. The area of &lt;vmgm&gt; expresses a VMG menu domain in the VMG space, and the number of the VMG menu domain is specified by adding a num attribute into the &lt;vmgm&gt; tag. For example, &lt;vmgm num=“n”&gt; indicates the nth VMG menu domain. It is expressed that a Vclick stream described in the area of &lt;vmgm num=“n”&gt; is added to the DVD video data constituting the nth VMG menu domain. 
   Further, the area of &lt;vmgm&gt; includes 0 or 1 or more &lt;pgc&gt; tag. The area of &lt;pgc&gt; denotes PGC (Program Chain) in the VMG menu domain, and the number of PGC is specified by adding a num attribute into the &lt;pgc&gt; tag. For example, &lt;pgc num=“n”&gt; indicates an nth PGC. It is expressed that a Vclick stream described in the area of &lt;pgc num=“n”&gt; is added to the DVD video data constituting the nth PGC. 
   Next, the area of &lt;vts&gt; includes 0 or 1 or more &lt;vts_tt&gt; tag, and 0 or 1 or more &lt;vtsm&gt; tag. The area of &lt;vts_tt&gt; expresses a title domain in the VTS space, and the number of the title domain is specified by adding a num attribute into the &lt;vts_tt&gt; tag. For example, &lt;vts_tt num=“n”&gt; indicates an nth title domain. It is expressed that a Vclick stream described in the area of &lt;vts_tt num=“n”&gt; is added to the DVD video data constituting the nth title domain. 
   The area of &lt;vtsm&gt; expresses a VTS menu domain in the VTS space, and the number of the VTS menu domain is specified by adding a num attribute into the &lt;vtsm&gt; tag. For example, &lt;vtsm num=“n”&gt; indicates an nth VTS menu domain. It is expressed that a Vclick stream described in the area of &lt;vtsm num=“n”&gt; is added to the DVD video data constituting the nth VTS menu domain. 
   Further, the area of &lt;vts_tt&gt; or &lt;vtsm&gt; include 0 or 1 or more &lt;pgc&gt; tag. The area of &lt;pgc&gt; expresses a PGC (Program Chain) in the title domain or the VTS menu domain, and the number of the PGC is specified by adding a num attribute into the &lt;pgc&gt; tag. For example, &lt;pgc num=“n”&gt; denotes an nth PGC. It is expressed that a Vclick stream described in the area of &lt;pgc num=“n”&gt; is added to the DVD video data constituting the nth PGC. 
   In the examples of  FIGS. 55 to 57 , six Vclick streams are added to the DVD video content. For example, the first Vclick stream is specified in &lt;pgm num=“1”&gt; of &lt;vmgm num=“1”&gt; in &lt;vmg&gt; by using the &lt;object&gt; tag. This indicates that the Vclick stream specified by the &lt;object&gt; tag is added to the first PGC of the first VMG menu domain in the VMG space. 
   In the &lt;object&gt; tag, a place where a Vclick stream exists is indicated by using a “data” attribute. For example, in an embodiment of the invention, the place where the Vclick stream exists is specified in “file://DVDrom:/DVD_enav/vclick1.vck”. Here, “file://DVDrom:/” indicates that the Vclick stream exists in the enhanced DVD disk, and further, “DVD_enav/” indicates that it exists under a “DVD_ENAV” directory in the disk, and “vclic1.vck” indicates a file name of the Vclick stream. Besides, by describing both an &lt;object&gt; tag describing the Vclick stream and an &lt;object&gt; tag describing a Vclick access table, information of the Vclick access table corresponding to the Vclick stream can be described. A place where the Vclick access table exists is indicated by using a “data” attribute in the &lt;object&gt; tag. For example, in the embodiment of the invention, the place where the Vclick access table exists is specified in “file://DVDrom:/DVD_enav/vclick1.ifo”. Here, “file://DVDrom:/” indicates that the Vclick access table exists in the enhanced DVD disk, and further, “DVD_enav/” indicates that it exists under a “DVD_ENAV” director in the disk, and “vclick1.ifo” indicates a file name of the Vclick access table. 
   A next Vclick stream is specified by using the &lt;object&gt; tag in &lt;vmgm num=“n”&gt; in &lt;vmg&gt;. This indicates that the Vclick stream specified by the &lt;object&gt; tag is added to the first whole VMG menu domain in the VMG space. In the &lt;object&gt; tag, a place where a Vclick stream exists is indicated by using a “data” attribute. For example, in the embodiment of the invention, the place where the Vclick stream exists is specified in “http//www.vclick.com/DVD_enav/vclick2.vck”. Here, “http//www.vclick.com/DVD_enav/” indicates that the Vclick stream exists in an external server, and “vclick2.vck” indicates a file name of the Vclick stream. 
   Also with respect to the Vclick access table, similarly, a place where the Vclick access table exists is indicated by using a “data” attribute in the &lt;object&gt; tag. For example, in the embodiment of the invention, the place where the Vclick access table exists is specified in “http//www.vclick.com/DVD_enav/vclick2. ifo”. Here, “http//www.vclick.com/DVD_enav/” denotes that the Vclick access table exists in an external server, and “vclick2.ifo” indicates a file name of the Vclick access table. 
   A third Vclick stream is specified by using an &lt;object&gt; tag in &lt;pgc num=“1”&gt; of &lt;vts_tt num=“1”&gt; in &lt;vts num=“1”&gt;. This indicates that the Vclick stream specified by the &lt;object&gt; tag is added to the first PGC of the first title domain in the first VTS space. In the &lt;object&gt; tag, a place where the Vclick stream exists is indicated by using a “data” attribute. For example, in the embodiment of the invention, the place where the Vclick stream exists is specified in “file://DVDrom:/DVD_enav/vclick3.vck”. Here, “file://DVDrom:/DVD_enav/” indicates that the Vclick stream exists under the “DVD_ENAV” directory in the disk, and “vclick3.vck” indicates a file name of the Vclick stream. 
   A fourth Vclick stream is specified by using an &lt;object&gt; tag in &lt;vts_tt num=“n”&gt; in &lt;vts num=“1”&gt;. This indicates that the Vclick stream specified by the &lt;object&gt; tag is added in the nth title domain in the first VTS space. In the &lt;object&gt; tag, a place where the Vclick stream exists is indicated by using a “data” attribute. For example, in the embodiment of the invention, the place where the Vclick stream exists is specified in “file://DVDrom:/DVD_enav/vclick4.vck”. Here, “file://DVDrom:/DVD_enav/” indicates that the Vclick stream exists under the “DVD_ENAV” directory in the disk, and “vclick4. vck” indicates a file name of the Vclick stream. 
   A fifth Vclick stream is specified by using an &lt;object&gt; tag in &lt;vtsm num=“1”&gt; in &lt;vts num=“1”&gt;. This indicates that the Vclick stream specified by the &lt;object&gt; tag is added in the first VTS menu domain in the first VTS space. In the &lt;object&gt; tag, a place where the Vclick stream exists is indicated by using a “data” attribute. For example, in the embodiment of the invention, the place where the Vclick stream exists is specified in “file://DVDrom:/DVD_enav/vclick5.vck”. Here, “file://DVDrom:/DVD_enav/” indicates that the Vclick stream exists under the “DVD_ENAV” directory in the disk, and “vclick5. vck” indicates a file name of the Vclick stream. 
   A sixth Vclick stream is specified by using an &lt;object&gt; tag in &lt;pgc num=“1”&gt; of &lt;vtsm num=“1”&gt; in &lt;vts num=“1”&gt;. This indicates that the Vclick stream specified by the &lt;object&gt; tag is added to the first PGC of the first VTS menu domain in the first VTS space. In the &lt;object&gt; tag, a place where the Vclick stream exists is indicated by using a “data” attribute. For example, in the embodiment of the invention, the place where the Vclick stream exists is specified in “file://DVDrom:/DVD_enav/vclick6.vck”. Here, “file://DVDrom:/DVD_enav/” indicates that the Vclick stream exists under the “DVD_ENAV” directory in the disk, and “vclick6. vck” indicates a file name of the Vclick stream. 
     FIG. 58  is a view showing the relation between the Vclick streams described in the description example of the Vclick info and the DVD video content. Here, it is understood that the fifth Vclick stream and the sixth Vclick stream are added to the first PGC of the first VTS menu domain in the first VTS space. This expresses that the two Vclick streams are added to the DVD video content, and can be switched by, for example, a user or a content provider (content author). 
   In the case where the switching is performed by the user, a “Vclick switch button” for switching a Vclick stream is provided in a remote controller (not shown), and by this, two or more Vclick streams can be freely changed. In the case where the switching is performed by the content provider, a command (“changeVclick( )”) for Vclick switching is described in the Markup language, and the command is issued at a timing specified in the Markup language by the content provider, and the two or more Vclick streams can be freely changed. 
   (5) Other Description Examples of Vclick Information File 
     FIGS. 59 to 60  indicates two other description examples of a Vclick information file. 
   (5-1) First Description Example 
   In a first example ( FIG. 59 ), two Vclick streams (Vclick stream #1, Vclick stream #2) recorded on a disk are added to one PGC (PGC#2). Here, an “audio” attribute in an &lt;object&gt; tag corresponds to an audio stream number, and in this example, it is indicated that in the case where an audio stream #1 of the DVD video content is reproduced, the Vclick stream #1 (Vclick1.vck) is synchronously reproduced, and in the case where an audio stream #2 is reproduced, the Vclick stream #2 (Vclick2.vck) is synchronously reproduced. 
   For example, in the case where the audio stream #1 of the video content includes Japanese audio, and the audio stream #2 includes English audio, the Vclick stream #1 is constructed in Japanese (that is, the display of explanation of the Vclick object is described in Japanese, or an access destination after the Vclick object is clicked is a site or a page constructed in Japanese), and the Vclick stream #2 is constructed in English (that is, the display of explanation of the Vclick object is described in English, or an access destination after the Vclick object is clicked is a site or a page constructed in Japanese). As a result, the language of the audio of the DVD content can be made to be coincident with the language of the Vclick stream. Actually, a reproduction apparatus refers to SPRM (1) (audio stream number) as a system parameter in the reproduction apparatus, searches the Vclick information file for the Vclick stream corresponding thereto, and reproduces it. 
   (5-2) Second Description Example 
   In a next example ( FIG. 60 ), two Vclick streams (Vclick stream #1, Vclick stream #2) recorded on a disk are added to one PGC (PGC #4). Here, an “angle” attribute in the &lt;object&gt; tag corresponds to an angle number, and in this example, it is indicated that in the case where an angle #1 of the video content is reproduced, the Vclick stream #1 (Vclick1.vck) is synchronously reproduced, in the case where an angle #3 is reproduced, the Vclick stream #2 (Vclick2.vck) is synchronously reproduced, and in the case where an angle #2 is reproduced, the Vclick stream is not reproduced. In general, in the case where an angle is different, since a position of an object to which a Vclick object is added, such as a person, is different, it is necessary to construct a Vclick stream for each angle. (Respective Vclick object data may be multiplexed in one Vclick stream). Actually, the reproduction apparatus refers to SPRM (3) (angle number) as a system parameter in the reproduction apparatus, searches the Vclick information file for the Vclick stream corresponding thereto, and reproduces it. 
   The reproduction apparatus (enhanced DVD player) according to an embodiment of the invention previously reads the Vclick information file before reproducing the DVD video content, or suitably refers thereto, so that it becomes possible to sequentially change the Vclick stream file to be added according to the reproduction state of the DVD video content. By this, when the Vclick stream is constructed, the degree of freedom can be ensured, and it becomes possible to reduce the authoring load. 
   Besides, by increasing the number of files (the number of streams) of one Vclick content and reducing the file size, it becomes possible to reduce an area (buffer) for storing the Vclick stream. 
   Besides, although the file size becomes large, by reducing the number of files (that is, one stream is made to include plural Vclick data), it becomes possible to smoothly switch the Vclick data in the case where the reproduction state of the DVD video content is changed. 
   (6) Outline of Data Structure and Access Table 
   The Vclick stream includes data relating to an area of an object, such as a person or a thing, appearing on a moving image recorded on the moving image data recording medium  231 , and data of a display method of an object in the client apparatus  200  and an operation to be performed by the client apparatus when the object is specified. Hereinafter, the structure of the Vclick data and the outline of its structural element will be described. 
   First, the object area data as the data relating to the area of the object, such as the person or the thing, appearing on the moving image will be described. 
     FIG. 3  is a view for explaining a structure of the object area data. Reference numeral  300  denotes a trajectory drawn by one object and expressed in three-dimensional coordinates of X (coordinate value of the video in the horizontal direction), Y (coordinate value of the video in the vertical direction), and T (time of the video). The object area is converted into the object area data at intervals of a time within a previously determined range (for example, from 0.5 second to 1.0 second, or from 2 seconds to 5 seconds). In  FIG. 3 , one object area  300  is converted into five object area data  301  to  305 , and these object area data are stored in separate Vclick access units (AU) (described later). As a conversion method at this time, for example, MPEG-4 shape coding or MPEG-7 spatio-temporal locator can be used. Since the MPEG-4 shape coding or the MPEG-7 spatio-temporal locator is a system in which the data amount is reduced by using a temporal correlation of the object area, there is a problem that data can not be decoded from the middle, and in the case where data at a certain time is lost, data around the time can not also be decoded. As shown in  FIG. 3 , the area of the object appearing on the moving image continuously for a long time is divided in the time direction and is converted into data, so that random access can be made easy, and an influence of a dropout of partial data can be reduced. Each Vclick_AU is effective only in a specific time section in the moving image. The time section in which the Vclick_AU is effective is called an effective period (lifetime) of the Vclick_AU. 
     FIG. 4  shows a structure of one unit (Vclick_AU) which can be independently accessed in the Vclick stream used in the embodiment of this invention. Reference numeral  400  denotes object area data. As described in  FIG. 3 , here, the trajectory in a certain continuous time section of one object area is converted into data. The time section in which this object area is described is called an active period (active time) of the Vclick_AU. In general, the active period of the Vclick_AU is the same as the effective period of the Vclick_AU. However, it is also possible to make the active period of the Vclick_AU a part of the effective period of the Vclick_AU. 
   Reference numeral  401  denotes a header of the Vclick_AU. The header  401  includes an ID for identifying the Vclick_AU, and data for specifying the data size of the AU. Reference numeral  402  denotes a time stamp, and denotes the time stamp of an effective period start of the Vclick_AU. In general, since the active period of the Vclick_AU and the effective period thereof are equal to each other, it also indicates that the object area described in the object area data  400  corresponds to which time in the moving image. As shown in  FIG. 3 , since the object area extends over a time range, in general, the time of the head of the object area is written in the time stamp  402 . Of course, the time interval of the object area described in the object area data and the time of the end of the object area may also be described. Reference numeral  403  denotes object attribute information, and includes, for example, a name of the object, an operation description at a time when the object is specified, a display attribute of the object, and the like. Data in the Vclick_AU will be described later in detail. It is better to sequentially arrange and record the Vclick_AU in the order of the time stamp so that it can be processed from the head. 
     FIG. 5  is a view for explaining a method in which plural AUs are arranged in the order of the time stamp and the Vclick stream is generated. In this drawing, there are two camera angles, that is, a camera angle 1 and a camera angle 2, and it is assumed that when the camera angle is switched in the client apparatus, the moving image to be displayed is also switched. Besides, it is assumed that the selectable language mode includes two kinds, that is, Japanese and English, and separate Vclick data are prepared for the respective languages. 
   In  FIG. 5 , Vclick_AUs  500 ,  501  and  502  are for the camera angle 1 and for Japanese, and Vclick AU  503  is for the camera angle 2 and for Japanese. Vclick AUs  504  and  505  are for English. Each of the Vclick_AUs  500  to  505  is data corresponding to one object in the moving image. That is, as described in  FIGS. 3 and 4 , metadata relating to one object is constructed of one or plural Vclick_AUs (in  FIG. 5 , one rectangle denotes one AU). The horizontal axis in this drawing corresponds to the time in the moving image, and the Vclick_AUs  500  to  505  are expressed correspondingly to the appearance time of the object. 
   Although the temporal separator of each Vclick_AU may be arbitrary, as exemplified in  FIG. 5 , when the separators of the Vclick_AUs are aligned for all objects, the management of data becomes easy. Reference numeral  506  denotes a Vclick stream constructed of these Vclick_AUs ( 500  to  705 ). The Vclick stream is constructed by arranging the Vclick_AUs in the order of the time stamp subsequently to the header part  507 . 
   Since there is a high possibility that the selected camera angle is changed by the user during viewing, it is better to form the Vclick stream by multiplexing the Vclick_AUs with different camera angles in the Vclick stream. This is because display switching at high speed can be performed in the client apparatus. For example, when the Vclick data is placed in the server apparatus  201 , and when the Vclick stream including the Vclick_AUs of the plural camera angles are transmitted to the client apparatus as it is, since the Vclick_AU corresponding to the camera angle during viewing is always sent to the client apparatus, switching of the cameral angle can be instantaneously performed. Of course, setting information of the client apparatus  200  is sent to the server apparatus  201 , and only necessary Vclick_AU is selected from the Vclick stream and can be transmitted. However, in this case, since it is necessary to perform communication with the server, the processing becomes somewhat slow (however, when a high speed measure such as an optical fiber is used for the communication, the problem of the processing delay can be solved). 
   On the other hand, since the attributes such as the moving image title, PGC of DVD video, an aspect ratio of the moving image, and a viewing region have a low frequency of change, when they are prepared as separate Vclick streams, the processing of the client apparatus becomes light, and the load of the network also becomes light. In the case where plural Vclick streams exist, as described before, by referring to the Vclick information file, it is possible to determine which Vclick stream should be selected. 
   In the case where the Vclick data exists in the server apparatus  201 , and in the case where the moving image is reproduced from the head, the server apparatus  201  has only to deliver the Vclick stream in sequence from the head to the client apparatus. However, in the case where random access occurs, it is necessary to deliver the data from the middle of the Vclick stream. At this time, in order to access a desired position in the Vclick stream at high speed, it becomes necessary to provide a Vclick access table. 
     FIG. 6  shows an example of the Vclick access table. This table is previously prepared and is recorded together with the Vclick stream. The table can also be made the same file as the Vclick information file. Reference numeral  600  denotes an arrangement of time stamps, and the time stamps of the moving image are listed. Reference numeral  601  denotes an arrangement of access points, and offset values of the Vclick stream corresponding to the time stamps of the moving image from the head are listed. In the case where a value corresponding to the time stamp of the random access destination of the moving image does not exist in the Vclick access table, reference is made to an access point of a time stamp of a close value, and the transmission start place is searched while referring to the time stamp in the Vclick stream in the vicinity of the access point. Alternatively, a time stamp at a time before the time stamp of the random access destination of the moving image is searched from the Vclick access table, and the Vclick stream is transmitted from the access point corresponding to the time stamp. 
   The Vclick access table is stored in the server apparatus, and is provided to help the server apparatus to retrieve the Vclick data to be transmitted according to the random access from the client. However, the Vclick access table stored in the server apparatus is downloaded to the client apparatus, and the client apparatus may be made to search the Vclick stream. Especially, in the case where the Vclick stream is downloaded from the server apparatus to the client apparatus at once, the Vclick access table is also downloaded from the server apparatus to the client apparatus at once. 
   On the other hand, there is also a case where the Vclick stream is recorded on a moving image recording medium such as a DVD and is provided. Also in this case, in order to retrieve data to be used according to the random access of reproduction content, it is effective that the client apparatus uses the Vclick access table. In this case, similarly to the Vclick stream, the Vclick access table is recorded on the moving image recording medium, and the client apparatus reads the Vclick access table from the moving image recording medium into the inner main storage or the like and uses it. 
   The random reproduction of the Vclick stream which is produced in connection with the random reproduction of the moving image, is processed by the metadata decoder  217 . In the Vclick access table of  FIG. 6 , the time stamp “time” is time information having a format of the time stamp of the moving image recorded on the moving image recording medium. For example, when the moving image is compressed by MPEG-2 and is recorded, the time stamp “time” has a format of PTS of MPEG-2. Further, in the case where the moving image has a navigation structure such as a title and a program chain as in, for example, a DVD, parameters (TTN, VTS_TTN, TT_PGCN, PTTN, etc.) expressing them are included in the format of the time stamp “time”. Values of the time stamps are arranged in ascending order or descending order. For example, in the case where the PTS is used for the time stamp, they can be arranged in the order of time. Also with respect to the time stamp including parameters of the DVD, since the sequence relation can be defined in accordance with a natural reproduction sequence of the DVD, it is possible to arrange the time stamps in sequence. 
   In the Vclick access table of  FIG. 6 , an access point “offset” indicates a position on the Vclick stream. For example, the Vclick stream is a file, and the access point “offset” indicates the value of a file pointer of the file. The relation of the access point “offset” paired with the time stamp “time” is as follows: 
   i) The position indicated by “offset” is a head position of a certain Vclick_AU. 
   ii) The value of a time stamp of the certain AU is not larger than a value of the time stamp “time”. 
   iii) The value of the time stamp of an AU one before the certain AU is truly smaller than the time stamp “time”. 
   The arrangement intervals of the time stamps “time” in the Vclick access table may be arbitrary, and are not required to be uniform. However, in view of convenience of retrieval or the like, they may be made uniform. 
   (7) Protocol Between Server Apparatus and Client Apparatus 
   Next, a protocol between the server apparatus and the client apparatus will be described. 
   As the protocol used when the Vclick data is transmitted from the server apparatus  201  to the client apparatus  200 , there is, for example, an RTP (Real-time Transport Protocol). The RTP is compatible with UDP/IP, and importance is attached to real-time properties, so that there is a possibility that a packet is lost. When the RTP is used, the Vclick stream is divided into transmission packets (RTP packets) and is transmitted. Here, an example of a storage method of the Vclick stream into the transmission packet will be described. 
     FIGS. 7 and 8  are views for explaining a transmission packet construction method in a case where the data size of a Vclick_AU is small and that in a case where the data size thereof is large. Reference numeral  700  of  FIG. 7  denotes a Vclick stream. The transmission packet includes a packet header  701  and a payload. The packet header  701  includes a serial number of the packet, a transmission time, specific information of a transmission origin and the like. The payload is a data area for storing transmission data. Vclick_AU ( 702 ) extracted in sequence from the Vclick_AU  700  is stored in the payload. In the case where a next Vclick_AU can not be received in the payload, padding data  703  is inserted into a remaining portion. The padding data is dummy data for adjusting the size of data, and is, for example, the continuation of 0 values. In the case where the size of the payload can be made equal to the size of one or plural Vclick_AUs, the padding data is unnecessary. 
   On the other hand,  FIG. 8  shows a construction method of a transmission packet in a case where one Vclick_AU can not be received in a payload. First, only a portion ( 802 ) of a Vclick_AU ( 800 ) which can be fitted into a payload of a first transmission packet is stored in the payload. Remaining data ( 804 ) is stored in a payload of a second transmission packet, and when a surplus occurs in the storage size of the payload, it is embedded with padding data  805 . A similar method applies to a case where one Vclick_AU is divided into three or more packets. 
   As a protocol other than the RTP, HTTP (Hypertext Transport Protocol) or HTTPS can be used. The HTTP is compatible with TCP/IP, and in this case, since missing data is retransmitted, highly reliable data communication can be performed. However, in the case where a throughput of the network is low, there is a fear that a data delay occurs. Since data is not dropped in the HTTP, it is not necessary to consider how the Vclick stream is divided into packets and is stored. 
   (8) Reproduction Procedure in a Case where Vclick Data Exists in the Server Apparatus 
   Next, a procedure of a reproduction processing in a case where a Vclick stream exists in the server apparatus  201  will be described. 
   (8-1) First Reproduction Procedure 
     FIG. 37  is a flowchart expressing a reproduction start processing procedure from user&#39;s instruction of a reproduction start to the reproduction start. First, at step S 3700 , the instruction of the reproduction start is inputted by the user. The interface handler  207  receives this input, and issues an instruction of a moving image reproduction preparation to the moving image reproduction controller  205 . Next, as a branch processing step S 3701 , it is judged whether or not a session with the server apparatus  201  has already been configured. When the session is not configured yet, the processing proceeds to step S 3702 , and when the session is already configured, it proceeds to step S 3703 . At step S 3702 , the processing of configuring the session between the server and the client is performed. 
     FIG. 9  shows an example of a communication procedure from the session configuration to the session disconnect in the case where RTP is used for the communication protocol between the server and the client. Although it is necessary to perform a negotiation between the server and the client at the start of the session, in the case of the RTP, RTSP (Real Time Streaming Protocol) is often used. However, since high reliability is required for the communication of the RTSP, it is preferable that the communication is performed by TCP/IP in the RTSP and by UDP/IP in the RTP. First, in order to configure the session, the client apparatus ( 200  in the example of  FIG. 2 ) requests the server apparatus ( 201  in the example of  FIG. 2 ) to provide information relating to the Vclick data to be subjected to streaming (DESCRIBE method of RTSP). 
   Here, it is assumed that the address of the server to deliver data corresponding to the moving image to be reproduced is previously known to the client by a method of, for example, recording the address information on the moving image data recording medium. In response to this, the server apparatus sends the information of the Vclick data to the client apparatus. Specifically, information such as a protocol version of the session, session owner, session name, connection information, time information of the session, metadata name, and metadata attribute is sent to the client apparatus. As an information description method of these, for example, SDP (Session Description Protocol) is used. Next, the client apparatus requests the server apparatus to configure the session (SETUP method of RTSP). The server apparatus prepares the streaming, and returns a session ID to the client apparatus. The processing up to this point is the processing of step S 3702  in the case where the RTP is used. 
   The communication procedure in the case where the HTTP, not the RTP, is used is performed as shown in, for example,  FIG. 10 . First, session configuration (3 way handshake) at TCP as a layer lower than the HTTP is performed. Here, similarly to the above, it is assumed that an address of the server to deliver data corresponding to the moving image to be reproduced is previously known to the client. Thereafter, a processing of transmitting a state of the client apparatus (for example, manufacture country, language, selection state of various parameters, etc.) to the server apparatus by using SDP or the like may be performed. The processing up to this point is the processing of step S 3702  in the case of the HTTP. 
   At step S 3703 , in a state where a session between the server apparatus and the client apparatus is configured, the processing of requesting the server to transmit the Vclick data is performed. This is performed in such a way that the interface handler issues an instruction to the network manager  208 , and the network manager  208  issues a request to the server. In the case of the RTP, the network manager  208  sends a PLAY method of RTSP to the server, and requests the Vclick data transmission. The server apparatus refers to the information received from the client up to now and the Vclick info existing in the server apparatus, and specifies the Vclick stream to be transmitted. Further, the server apparatus uses time stamp information of the reproduction start position included in the Vclick data transmission request and the Vclick access table existing in the server apparatus to specify the transmission start position in the Vclick stream, divides the Vclick stream into packets, and sends them to the client apparatus by the RTP. 
   On the other hand, in the case of the HTTP, the network manager  208  transmits the GET method of the HTTP, and requests Vclick data transmission. This request may include information of the time stamp of the reproduction start position of the moving image. The server apparatus specifies the Vclick stream to be transmitted and the transmission start position in the stream by a similar method to the time of the RTP, and sends the Vclick stream to the client apparatus by the HTTP. 
   Next, at step S 3704 , a processing of buffering the Vclick stream sent from the server into the buffer  209  is performed. This is performed to avoid such a state that the Vclick stream transmission from the server becomes insufficient during the reproduction of the Vclick stream, and the buffer becomes empty. When it is notified from the metadata manager  210  to the interface handler that the sufficient Vclick stream is stored in the buffer, the processing proceeds to step S 3705 . At step S 3705 , the interface handler issues a reproduction start instruction of the moving image to the controller  205 , and instructs the metadata manager  210  to start the transmission of the Vclick stream to the metadata decoder  217 . 
   (8-2) Second Reproduction Procedure 
     FIG. 38  is a flowchart for explaining a reproduction start processing procedure different from  FIG. 37 . In the processing explained in the flowchart of  FIG. 37 , according to the state of the network and the processing capacity of the server and the client apparatus, there is a case where it takes much time to perform the processing of buffering a fixed amount of Vclick stream at step S 3704 . That is, there is a case where it takes much time from user&#39;s instruction of reproduction to the start of the actual reproduction. In the processing procedure of  FIG. 38 , when the user instructs the reproduction start at step S 3800 , the reproduction of the moving image is immediately started at next step S 3801 . That is, the interface handler  207  receiving the reproduction start instruction from the user immediately issues the reproduction start instruction to the controller  205 . By this, the user is not kept waiting until the moving image can be viewed after the instruction of the reproduction. Processings from next step S 3802  to step S 3805  are the same as the processings from step S 3701  to step S 3704  of  FIG. 37 . 
   At step S 3806 , the processing of decoding the Vclick stream in synchronization with the moving image during reproduction is performed. That is, when receiving from the metadata manager  210  the notification that a fixed amount of Vclick stream is stored in the buffer, the interface handler  207  instructs the metadata manager  210  to start the transmission of the Vclick stream to the metadata decoder. The metadata manager  210  receives the time stamp of the moving image during reproduction from the interface handler, specifies the Vclick_AU corresponding to the time stamp from the data stored in the buffer, and transmits it to the metadata decoder. 
   In the processing procedure of  FIG. 38 , although the user is not kept waiting until the moving image can be viewed after the instruction of the reproduction, there is a problem that since decoding of the Vclick stream is not performed immediately after the reproduction start, the display concerning the object is not performed, or even if the object is clicked, any operation does not occur. 
   During the reproduction of the moving image, the network manager  208  of the client apparatus receives the Vclick stream sequentially sent from the server apparatus, and stores it in the buffer  209 . The stored object metadata is sent to the metadata decoder  217  at a suitable timing. That is, the metadata manager  208  refers to the time stamp of the moving image during reproduction sent from the metadata manager  210 , specifies the Vclick_AU corresponding to the time stamp from the data stored in the buffer  209 , and sends the specified object metadata to the metadata decoder  217  in AU units. The metadata decoder  217  decodes the received data. However, data for a camera angle different from a camera angle presently selected by the client apparatus may be made not to be decoded. In the case where it is known that the Vclick_AU corresponding to the time stamp of the moving image during reproduction exists in the metadata decoder  217 , the object metadata may be made not to be sent to the metadata decoder. 
   The time stamp of the moving image during reproduction is sequentially sent from the interface handler to the metadata decoder  217 . The metadata decoder decodes the Vclick_AU in synchronization with the time stamp, and sends necessary data to the AV renderer  218 . For example, in the case where the display of the object area is instructed by the attribute information described in the Vclick_AU, a mask image and a contour of the object area are created, and are sent to the AV renderer  218  in synchronization with the time stamp of the moving image during reproduction. Besides, the metadata decoder compares the time stamp of the moving image during reproduction with the effective time of the Vclick_AU to judge old object metadata which is unnecessary, and deletes the data. 
   (8-3) Procedure of Reproduction Stop Processing 
     FIG. 39  is a flowchart for explaining a procedure of a reproduction stop processing. At step S 3900 , the user instructs a reproduction stop during the reproduction of the moving image. Next, at step S 3901 , a processing of stopping the reproduction of the moving image is performed. This is performed in such a way that the interface handler  207  issues the stop instruction to the controller  205 . At the same time, the interface handler instructs the metadata manager  210  to stop the transmission of the object metadata to the metadata decoder. 
   Step S 3902  is a processing to disconnect the session with the server. In the case where the RTP is used, as shown in  FIG. 9 , TEARDOWN method of RTSP is sent to the server. When receiving the message of TEARDOWN, the server apparatus stops the data transmission, ends the session, and sends a confirmation message to the client apparatus. By this processing, a session ID used for the session becomes invalid. On the other hand, in the case where the HTTP is used, as shown in  FIG. 10 , Close method of the HTTP is sent to the server, and the session is ended. 
   (9) Random Access Procedure in a Case where Vclick Data Exists in the Server Apparatus 
   Next, a procedure of random access reproduction in a case where the Vclick stream exists in the server apparatus  201  will be described. 
   (9-1) First Procedure 
     FIG. 40  is a flowchart showing a processing procedure from user&#39;s instruction of a start of random access reproduction to the start of the reproduction. First, at step S 4000 , the start instruction of the random access reproduction is inputted by the user. As a method of the input, there is a method in which the user makes selection from a list of accessible positions such as a chapter, a method in which the user specifies one point from a slide bar corresponding to the time stamps of the moving image, or a method in which the time stamp of the moving image is directly inputted. The interface handler  207  receives the inputted time stamp, and issues an instruction of a moving image reproduction preparation to the moving image reproduction controller  205 . In case the moving image is already being reproduced, the reproduction stop of the moving image during the reproduction is instructed, and the instruction of the moving image reproduction preparation is issued. Next, as a branch processing step S 4001 , it is judged whether or not the session with the server apparatus  201  has already been configured. In the case where the session has already been configured as in, for example, the case where the moving image is being reproduced, a session disconnect processing of step S 4002  is performed. When the session is not configured yet, the processing of step S 4002  is not performed, and the processing proceeds to step S 4003 . At step S 4003 , a processing of configuring the session between the sever and the client is performed. This processing is the same processing as step S 3702  of  FIG. 37 . 
   Next, at step S 4004 , in the state where the session between the server apparatus and the client apparatus is configured, the time stamp of the reproduction start position is specified for the server, and a processing to request Vclick data transmission is performed. This is performed in such a manner that the interface handler issues the instruction to the network manager  208 , and the network manager  208  issues the request to the server. In the case of the RTP, the network manager  208  sends the PLAY method of the RTSP to the server, and requests the Vclick data transmission. At this time, the time stamp to specify the reproduction start position is also sent to the server by a method of using a Range description. The server apparatus refers to the information received from the client up to now and the Vclick info existing in the server apparatus, and specifies the object metadata stream to be transmitted. Further, the server apparatus uses the time stamp information of the reproduction start position included in the Vclick data transmission request and the Vclick access table existing in the server apparatus to specify the transmission start position in the Vclick stream, divides the Vclick stream into packets, and sends them to the client apparatus by the RTP. 
   On the other hand, in the case of the HTTP, the network manager  208  transmits the GET method of the HTTP, and requests the Vclick data transmission. This request includes information of the time stamp of the reproduction start position of the moving image. Similarly to the RTP, the server apparatus refers to the Vclick information file to specify the Vclick stream to be transmitted, and further uses the time stamp information and the Vclick access table existing in the server apparatus to specify the transmission start position in the Vclick stream, and sends the Vclick stream to the client apparatus by the HTTP. 
   Next, at step S 4005 , a processing of buffering the Vclick stream sent from the server into the buffer  209  is performed. This is performed in order to avoid such a state that the Vclick stream transmission from the server becomes insufficient during the reproduction of the Vclick stream, and the buffer becomes empty. When it is notified to the interface handler from the metadata manager  210  that the sufficient Vclick stream is stored in the buffer, the processing proceeds to step S 4006 . At step S 4006 , the interface handler issues the reproduction start instruction of the moving image to the controller  205 , and further issues the instruction to the metadata manager  210  to start the transmission of the Vclick stream to the metadata decoder. 
   (9-2) Second Procedure 
     FIG. 41  is a flowchart for explaining a procedure of a random access reproduction start processing different from  FIG. 40 . 
   In the processing explained in the flowchart of  FIG. 40 , according to the state of the network and the processing capacity of the server and the client apparatus, there is a case where it takes much time to perform the processing of buffering a fixed amount of Vclick stream at step S 4005 . That is, there is a case where it takes much time from user&#39;s instruction of reproduction to the start of the actual reproduction. 
   On the other hand, in the processing procedure of  FIG. 41 , at step S 4100 , when the user instructs the reproduction start, the reproduction of the moving image is immediately started at step S 4101 . That is, the interface handler  207  receiving the reproduction start instruction from the user immediately issues the random access reproduction start instruction to the controller  205 . By this, the user is not kept waiting until the moving image can be viewed after the instruction of the reproduction. Processings from next step S 4102  to step S 4106  are the same as the processings from step S 4001  to step S 4005  of  FIG. 40 . 
   At step S 4107 , a processing of decoding the Vclick stream is performed in synchronization with the moving image during reproduction. That is, when receiving from the metadata manager  210  a notification that a fixed amount of Vclick stream is stored in the buffer, the interface handler  207  instructs the metadata manager  210  to start the transmission of the Vclick stream to the metadata decoder. The metadata manager  210  receives the time stamp of the moving image under reproduction from the interface handler, specifies the Vclick_AU corresponding to this time stamp from the data stored in the buffer, and transmits it to the metadata decoder. 
   In the processing procedure of  FIG. 41 , although the user is not kept waiting until the moving image can be viewed after the instruction of the reproduction, since the decoding of the Vclick stream is not performed immediately after the reproduction start, there is a problem that the display concerning the object is not performed, or even if the object is clicked, any operation does not occur. 
   Incidentally, since the processing during the reproduction of the moving image and the moving image stop processing are the same as the case of the normal reproduction processing, their explanation will be omitted. 
   (10) Reproduction Procedure in a Case where Vclick Data Exists in the Client Apparatus 
   Next, a procedure of a reproduction processing in a case where the Vclick stream exists in the moving image data recording medium  231  will be described. 
     FIG. 42  is a flowchart showing a reproduction start processing procedure from user&#39;s instruction of a reproduction start to the reproduction start. First, at step S 4200 , the instruction of the reproduction start is inputted by the user. The interface handler  207  receives this input and issues an instruction of a moving image reproduction preparation to the moving image reproduction controller  205 . Next, at step S 4201 , a processing of specifying a Vclick stream to be used is performed. At this processing, the interface handler refers to the Vclick information file on the moving image data recording medium  231 , and specifies the Vclick stream corresponding to the moving image whose reproduction is instructed by the user. 
   At step S 4202 , a processing of storing the Vclick stream in the buffer is performed. In order to perform this processing, the interface handler  207  first instructs the metadata manager  210  to allocate the buffer. Although the size of the buffer to be allocated is determined to be a sufficient size to store the specified Vclick stream, in general, a buffer initializing document describing this size is recorded on the moving image data recording medium  231 . In the case where there is no initializing document, a previously determined size is applied. When the allocating of the buffer is completed, the interface handler  207  issues an instruction to the controller  205  to read the specified Vclick stream and to store it in the buffer. 
   When the Vclick stream is stored in the buffer, the reproduction start processing at step S 4203  is next performed. At this processing, the interface handler  207  issues an reproduction instruction of a moving image to the moving image reproduction controller  205 , and simultaneously issues an instruction to the metadata manager  210  to start the transmission of the Vclick stream to the metadata decoder. 
   During the reproduction of the moving image, the Vclick_AU read from the moving image data recording medium  231  is stored in the buffer  209 . The stored Vclick stream is sent to the metadata decoder  217  at a suitable timing. That is, the metadata manager  208  refers to the time stamp of the moving image during reproduction sent from the metadata manager  210 , specifies the Vclick_AU corresponding to the time stamp from the data stored in the buffer  209 , and sends this specified Vclick_AU to the metadata decoder  217 . The metadata decoder  217  decodes the received data. However, the data for a camera angle different from a camera angle presently selected by the client apparatus may not be decoded. In the case where it is known that the Vclick_AU corresponding to the time stamp of the moving image during reproduction already exists in the metadata decoder  217 , the Vclick stream may not be sent to the metadata decoder. 
   The time stamp of the moving image during reproduction is sequentially sent from the interface handler to the metadata decoder  217 . The metadata decoder decodes the Vclick_AU in synchronization with the time stamp, and sends necessary data to the AV renderer  218 . For example, in the case where the display of an object area is instructed by attribute information described in the AU of the object metadata, a mask image and a contour of the object area are created and are sent to the AV renderer  218  in synchronization with the time stamp of the moving image during reproduction. Besides, the metadata decoder compares the time stamp of the moving image during reproduction with the effective time of the Vclick_AU, judges old Vclick_AU which is unnecessary, and deletes the data. 
   When a reproduction stop is instructed by the user during the reproduction of the moving image, the interface handler  207  issues the stop instruction of the moving image reproduction and the stop instruction of the readout of the Vclick stream to the controller  205 . By the instructions, the reproduction of the moving image is ended. 
   (11) Random Access Procedure in a Case where Vclick Data Exists in the Client Apparatus 
   Next, a processing procedure of random access reproduction in a case where a Vclick stream is on the moving image data recording medium  231  will be described. 
     FIG. 43  is a flowchart showing a processing procedure from user&#39;s instruction of a start of random access reproduction to the start of the reproduction. First, at step S 4300 , the instruction of the random access reproduction start is inputted by the user. As a method of the input, there is a method in which the user makes selection from a list of accessible positions such as a chapter, a method in which the user specifies one point from a slide bar made to correspond to the time stamps of the moving image, or a method in which the time stamp of the moving image is directly inputted. The interface handler  207  receives the inputted time stamp, and issues an instruction of a random access reproduction preparation of the moving image to the moving image reproduction controller  205 . 
   Next, at step S 4301 , a processing of specifying a Vclick stream to be used is performed. At this processing, the interface handler refers to the Vclick information file on the moving image data recording medium  231 , and specifies the Vclick stream corresponding to the moving image whose reproduction is instructed by the user. Further, the interface handler refers to the Vclick access table on the moving image data recording medium  231  or the Vclick access table read onto the memory, and specifies the access point in the Vclick stream corresponding to the random access destination of the moving image. 
   Step S 4302  is a branch processing, and it is judged whether the specified Vclick stream is read in the buffer  209  at present. In the case where it is not read in the buffer, after the processing of step S 4303  is performed, the processing proceeds to step S 4304 . In the case where it is read in the buffer at present, the processing of step S 4303  is not performed, and the processing proceeds to step S 4304 . At step S 4304 , the random access reproduction of the moving image is started, and the decoding of the Vclick stream is started. At this processing, the interface handler  207  issues the random access reproduction instruction of the moving image to the moving image reproduction controller  205 , and simultaneously issues the instruction to the metadata manager  210  to start the transmission of the Vclick stream to the metadata decoder. Thereafter, the decoding processing of the Vclick stream is performed in synchronization with the reproduction of the moving image. Since the processing during the moving image reproduction and the moving image reproduction stop processing are the same as the case of the normal reproduction processing, their explanation will be omitted. 
   (12) Procedure from Click to Display of Relevant Information 
   Next, an operation of the client apparatus in a case where the user uses a pointing device such as a mouse to click an object area will be described. When the user clicks, a clicked coordinate position on the moving image is inputted to the interface handler  207 . The interface handler sends the time stamp and the coordinate of the moving image at the time of the click to the metadata decoder  217 . From the time stamp and the coordinate, the metadata decoder performs a processing to identify an object indicated by the user. 
   The metadata decoder decodes the Vclick stream in synchronization with the reproduction of the moving image. Accordingly, since the area of the object of the time stamp at the time of the click is produced, this processing can be easily performed. In the case where plural object areas exist at the clicked coordinate, reference is made to layer information included in the Vclick_AU, and the most forward object is identified. 
   When the object specified by the user is identified, the metadata decoder  217  sends an action description (script to indicate an operation) described in the object attribute information  403  to the script interpreter  212 . The script interpreter having received the action description interprets the operation content and executes it. For example, the specified HTML file is displayed, or the reproduction of the specified moving image is started. The HTML file and the moving image data may be recorded in the client apparatus  200 , may be sent from the server apparatus  201  through the network, or may exist in another server on the network. 
   (13) Details of Data Structure 
   Next, a more specific structural example of a data structure will be described. As described in  FIG. 5 , the Vclick stream  506  includes the header of the Vclick stream and the plural Vclick AUs.  FIG. 11  shows an example of the data structure of the header of the Vclick stream. The meaning of each of data elements is as follows:
         “vclick_version” denotes the start of the header of the Vclick stream, and specifies a version of a format; and   “vclick_length” denotes, in bytes, the data length of a portion after “vclick_length” in the Vclick stream.       

   Next, the detailed data structure of the Vclick AU will be described. The rough data structure of the Vclick AU is as described in  FIG. 4 . 
     FIG. 12  shows an example of the data structure of the header  401  of the Vclick AU. The meaning of each of data elements is as follows:
         “vau_start_code” denotes the start of each of the Vclick_AUs;   “vau_length” denotes, in bytes, the data length of a portion after “vau_length” in the header of the Vclick_AU;   “vau_id” denotes an identification ID of the Vclick_AU, and it is judged by parameters expressing the state of the client apparatus and this ID whether the Vclick_AU should be decoded;   “object_id” denotes an identification number of an object described in the Vclick data, and in the case where the same value of “object_id” is used in two Vclick_AUs, both semantically denote data for the same object;   “object_subid” denotes semantic continuity of the object, and in the case where both “object_id” and “object_subid” are the same in two Vclick_AUs, it is meant that both are continuous (appearing on the same scene and identical) objects;   “continue flag” denotes a flag (In the case where the first one bit is “1”, it indicates that the object area described in the Vclick_AU is continuous with the object area described in the former Vclick_AU having the same object_id. In the case of not, this flag becomes “0”. Similarly, the second bit indicates the continuity of the object area described in the Vclick_AU and the object area described in the next Vclick_AU and having the same “object_id”); and   “layer” denotes a layer value of an object. When the layer value is large (or small), it is meant that the object is positioned forward on the screen. In the case where plural objects exist in the clicked place, it is judged that the object having the largest (or smallest) layer value is clicked.       
     FIG. 13  shows an example of a data structure of the time stamp  402  of the Vclick_AU. In this example, it is assumed that a DVD is used as the moving image data recording medium  204 . By using a following time stamp, it becomes possible to specify an arbitrary time of a moving image on the DVD, and the synchronization of the moving image and the Vclick data can be realized. The meaning of each of data elements is as follows:
         “time_type” denotes the start of the time stamp for the DVD;   “VTSN” denotes a VTS (Video Title Set) number of the DVD video;   “TTN” denotes a title number in a title domain of the DVD video, and corresponds to a value stored in a system parameter SPRM (4) of the DVD player;   “VTS_TTN” denotes a VTS title number in the title domain of the DVD video, and corresponds to a value stored in a system parameter SPRM (5) of the DVD player;   “ITT_PGCN” indicates a title PGC (Program Chain) number in the title domain of the DVD video, and corresponds to a value stored in a system parameter SPRM (6) of the DVD player;   “PTTN” denotes a partial title (Part_of_Title) number of the DVD video, and corresponds to a value stored in a system parameter SPRM (7) of the DVD player;   “CN” denotes a cell number of the DVD video;   “AGLN” denote an angle number of the DVD video; and   “PTS[s . . . e]” denotes data from an sth bit to an eth bit in the display time stamp of the DVD video.       
     FIG. 14  shows an example of a data structure of a time stamp skip of the Vclick_AU. In the case where the time stamp skip is described in the Vclick_AU instead of the time stamp, it is meant that the time stamp of the Vclick_AU is the same as the time stamp of the Vclick_AU just before. The meaning of each data element is as follows:
         “time_type” denotes a start of the time stamp skip.       
     FIG. 15  shows an example of a data structure of the object attribute information  403  of the Vclick_AU. The meaning of each of data elements is as follows:
         “attribute_length” denotes, in bytes, the data length of a portion after “attribute_length” in the object attribute information; and   “data_bytes” denotes a data part of the object attribute information. One or plural attribute data shown in  FIG. 16  are described in this portion. An example of the maximum number of data which can be described in one Vclick_AU with respect to each attribute is indicated in a column of “maximum value” of  FIG. 16 . A data element “attribute_id” denotes an ID included in each attribute data, and denotes data for distinguishing the kinds of attributes. A “name” attribute indicates information for specifying a name of an object. In an “action” attribute, it is described what action should be performed when an object area in a moving image is clicked. A “contour” attribute indicates an attribute how to display a contour of an object. A “blinking area” attribute specifies a blinking color at a time when an object area is blinked and displayed. In a “mosaic area” attribute, a way of forming a mosaic at a time when an object area is mosaicked and displayed is described. A “filled-in area” attribute specifies a color at a time when an object area is colored and displayed.       
   An attribute belonging to a “text” category defines an attribute relating to a character to be displayed when the character is desired to be displayed on a moving image. A text to be displayed is described in “text information”. A “text attribute” specifies attributes of a color, a font and the like of a text to be displayed. A “highlight effect” attribute specifies what character is highlight-displayed in what way when part of or all of the text is highlight-displayed. A “blinking effect” attribute specifies what character is blink-displayed in what way when part of or all of the text is blink-displayed. In a “scroll effect” attribute, it is described in which direction and at what speed scrolling is performed when a text to be displayed is scrolled. In a “karaoke effect” attribute, it is specified that when a color of a text is sequentially changed, a color of which character should be changed at what timing. Finally, a “layer extension” attribute is used to define a timing of a change of a layer value and its value in a case where the layer value of an object is changed in the Vclick_AU. The data structures of the above attributes will be respectively described below. 
     FIG. 17  shows an example of the data structure of the name attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes a type of attribute data, and this value is made 00h with respect to the name attribute;   “data_length” denotes, in bytes, a data length after “data_length” of the name attribute data;   “language” denotes a language used for description of following elements (name and annotation), and ISO-639 ┌code for the representation of names of languages┘ is used for specifying the language;   “name_length” denotes, in bytes, a data length of a “name” element;   “name” denotes a character string, and expresses the name of the object described in this Vclick_AU;   “annotation_length” denotes a data length of an “annotation” element; and   “annotation” denotes a character string, and expresses an annotation relating to the object described in the Vclick_AU.       
     FIG. 18  shows an example of the data structure of the action attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes a type of attribute data, and this value is made 01h with respect to the “action” attribute;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in the action attribute data;   “script_language” denotes a kind of a script language described in a “script” element;   “script_length” denotes a data length of a “script” element in byte units; and   “script” denotes a character string, and an action to be executed in the case where an object described in the Vclick_AU is specified by the user is described in the script language specified by “script_language”.       
     FIG. 19  shows an example of the data structure of the contour attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes a type of an attribute, and this value is made 02h with respect to the contour attribute;   “data_length” denotes a data length of a portion after “data_length” in the contour attribute data;   “color_r”, “color_g”, “color_b” and “color_a” denote display colors of a contour of an object described in the object metadata AU;   “color_r”, “color_g” and “color_b” respectively denote values of red, green, and blue in an RGB expression of colors, and “color_a” denotes transparency;   “line_type” denotes the kind (solid line, broken line, etc.) of a contour of an object described in the Vclick_AU; and   “thickness” denotes the thickness of a contour of an object described in the Vclick_AU.       
     FIG. 20  shows an example of the data structure of the blinking area attribute of an object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 03h with respect to the blinking area attribute data;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in the blinking area attribute data;   “color_r”, “color_g”, “color_b” and “color_a” denote display colors of an area of the object described in the Vclick_AU (“color_r”, “color_g”, “color_b” respectively denotes values of red, green and blue in the RGB expression of colors. On the other hand, “color_a” denotes transparency. Blinking of the object area is realized by alternately displaying the color specified in the filled-in area attribute and the color specified by this attribute); and   “interval” denotes a time interval of blinking.       
     FIG. 21  shows an example of the data structure of the mosaic area attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 04h with respect to mosaic area attribute data;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in mosaic area attribute data;   “mosaic_size” denotes the size of a mosaic block in pixel units; and   “randomness” denotes the degree of random exchange in a case where positions of mosaicked blocks are exchanged.       
     FIG. 22  shows an example of the data structure of the mosaic area attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 05h with respect to the filled-in area attribute data;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in the filled-in attribute data; and   “color_r”, “color_g”, “color_b” and “color_a” denote display colors of an object area described in the Vclick_AU, and “color_r”, “color_g” and “color_b” respectively denote values of red, green and blue in the RGB expression of colors, and on the other hand, “color_a” denotes transparency.       
     FIG. 23  shows an example of the data structure of the text information of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 06h with respect to the text information of the object;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in the text information of the object;   “language” denotes a language of a described text, and as a designation method of the language, for example, ISO-639 “code for the representation of names of languages” can be used;   “char_code” denotes the code kind of a text, and for example, UTF-8, UTF-16, ASCII or Shift JIS is specified;   “direction” denotes a left direction, a right direction, a lower direction, or an upper direction as a direction in which characters are arranged (For example, in English or French, characters are normally arranged in the left direction. On the other hand, in Arabic, characters are arranged in the right direction, and in Japanese, they are arranged in the left direction or the lower direction. However, a direction other than the arrange direction determined for each language may be specified. Besides, an oblique direction may be specified):   “text_length” denotes, in bytes, a length of “timed text”; and   “text” denotes a character string, and denotes a text described using the character code specified by “char_code”.       
     FIG. 24  shows an example of the data structure of the text attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 07h with respect to the text attribute of the object;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in the text attribute of the object;   “font_length” denotes a description length of a font in byte units;   “font” denotes a character string, and specifies a font used when a text is displayed; and   “color_r”, “color_g”, “color_b” and “color_a” denote display colors used when a text is displayed. A color is expressed by RGB, and “color_r”, “color_g” and “color_b” respectively denote values of red, green and blue, and “color_a” denotes transparency.       
     FIG. 25  shows an example of the data structure of the text highlight effect attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 08h with respect to the text highlight effect attribute data of the object;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in the text highlight effect attribute data of the object;   “entry” denotes the number of “highlight_effect_entry” in the text highlight effect attribute data; and   “highlight_entries” includes an “entry” number of “highlight_effect_entry”.       
   The specification of “highlight_effect_entry” will be described next. 
     FIG. 26  shows an example of the data structure of an entry of the text highlight effect attribute of the object. The meaning of each of data elements is as follows:
         “start_position” denotes a start position of a character to be emphasized by the number of characters from the head to the character;   “end_position” denotes an end position of the character to be emphasized by the number of characters from the head to the character; and   “color_r”, “color_g”, “color_b” and “color_a” denote display colors of the character after emphasis. A color is expressed by RGB. Besides, “color_r”, “color_g” and “color_b” respectively denote values of red, green and blue, and “color_a” denotes transparency.       
     FIG. 27  shows an example of the data structure of the text blinking effect attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 09h with respect to the blinking effect attribute data of the object;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in the text blinking effect attribute data;   “entry” denotes the number of “blink_effect_entry” in the text blinking effect attribute data; and   “blink_entries” includes an “entry” number of “blink_effect_entry”.       
   The specification of “blink_effect_entry” will be described below. 
     FIG. 28  shows an example of the data structure of the text blinking effect attribute of the object. The meaning of each of data elements is as follows:
         “start_position” denotes a start position of a character to be blinked by the number of characters from the head to the character;   “end_position” denotes an end position of the character to be blinked by the number of characters from the head to the character;   “color_r”, “color_g”, “color_b” and “color_a” denote display colors of a blinking character (A color is expressed by RGB. Besides, “color_r”, “color_g” and “color_b” respectively denote values of red, green and blue, and “color_a” denote transparency. The color specified here and the color specified by the text attribute are alternately displayed so that the character is blinked): and   “interval” denotes a time interval of blinking.       
     FIG. 29  shows an example of the data structure of an entry of the text scroll effect attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 0ah with respect to the text scroll effect attribute data of the object;   “data_length” denotes a data length of a portion after “data_length” in the text scroll effect attribute data in byte units;   “direction” denotes a direction in which characters are scrolled, and for example, 0 denotes a direction from right to left, 1 denotes a direction from left to right, 2 denotes a direction from upper to down, and 3 denotes a direction from lower to upper; and   “delay” denotes a scrolling speed expressed by a time difference between the display of a first character to be displayed and the display of a final character.       
     FIG. 30  shows an example of the data structure of an entry of the text karaoke effect attribute of the object. The meaning of each of data elements is as follows:
         “attribute_id” denotes the type of attribute data, and this value is made 0bh with respect to the text karaoke effect attribute data of the object;   “data_length” denotes a data length of a portion after “data_length” in the text karaoke effect attribute data in byte units;   “start_time” denotes a change start time of a character color of a character string specified by the first “karaoke_effect_entry” included in “data_bytes” of the attribute data;   “entry” indicates the number of “karaoke_effect_entry” in the text karaoke effect attribute data; and   “karaoke_entries” includes an “entry” number of “karaoke_effect_entry”.       
   The specification of “karaoke_effect_entry” will be described next. 
     FIG. 31  shows an example of the data structure of an entry (“karaoke_effect_entry”) of the text karaoke effect attribute of the object. The meaning of each of data elements is as follows:
         “end_time” denotes a change end time of a character color of a character string specified by this entry, and in the case where there is an entry subsequent to this entry, it also denotes a change start time of a character color of a character string specified by the next entry;   “start_position” denotes a position of a first character of a character string in which a character color is to be changed by the number of characters from the head to the character; and   “end_position” denotes a position of a final character of the character string in which the character color is to be changed by the number of characters from the head to the character.       
     FIG. 32  shows an example of the data structure of the layer attribute extension of the object. The meaning of each of data elements is as follows.
         “attribute_id” denotes the type of attribute data, and this value is made 0ch with respect to the layer attribute extension data of the object;   “data_length” denotes a data length of a portion after “data_length” in the layer attribute extension data in byte units;   “start_time” denotes a start time when a layer value specified by the first “layer_extension_entry” included in “data_bytes” of the attribute data becomes effective;   “entry” denotes the number of “layer extension entry” included in the layer attribute extension data; and   “layer_entries” includes an “entry” number of “layer_extension_entry”.       
   The specification of “layer_extension_entry” will be described next. 
     FIG. 33  shows an example of the data structure of an entry (layer_extension_entry) of the layer attribute extension of the object. The meaning of each of data elements is as follows:
         “end_time” denotes a time when a layer value specified by “layer_extension_entry” becomes ineffective, and in the case where there is also an entry next to this entry, it also simultaneously denotes a time when a layer value specified by the next entry becomes effective; and   “layer” denotes a layer value of the object.       
     FIG. 34  shows an example of the data structure of the object area data  400  of the AU of the object metadata. The meaning of each of data elements is as follows:
         “vcr_start_code” denotes a start of object area data;   “data_length” denotes, in bytes, a data length of a portion after “data_length” in the object area data; and   “data_bytes” denotes a data part in which the object area is described. For example, a binary format of “SpatioTemporalLocator” of MPEG-7 can be used for the description of the object area.
 
(14) Effective Time Limit of Vclick AU
       
   Next, a data structure in which an effective time limit is set in a Vclick AU will be described. 
   The “effective time” limit here is a time limit defined with respect to an axis of absolute time indicated by a date of the Christian Era and a time, and is different from the effective period defined with respect to the time axis of a moving image. For example, in the case where relevant content on a network is deleted without causing an access error, the effective time limit (for example, 0:00 AM, Aug. 31, 2004) is required. 
   (14-1) Outline of Operation 
     FIG. 45  is a view for explaining the outline of an operation in the case where the effective time limit is set in the Vclick AU. 
   Reference numerals  4500 ,  4501  and  4502  denote objects described in the Vclick AU, and similarly to  FIG. 5 , the width of a square indicates an effective period along the time axis of a moving image. It is assumed that when the object  4500  is specified, an HTML document in a DVD  4503  in which the moving image is stored is exhibited, and the object  4501  and the object  4502  exhibit HTML documents on a network  4504 . Here, it is assumed that the effective time limit is not set in the object  4500 . It is assumed that the effective time limit from Jul. 1, 2004 is set in the object  4501 . It is assumed that the effective time limit till Jul. 31, 2004 and the effective time limit from Jan. 1, 2005 to Jan. 31, 2005, that is, the two effective time limits are set in the object  4502 . 
   (14-2) Explanation of Effective Time Limit 
     FIG. 46  is a view for explaining the effective time limits of the objects  4500  to  4502 . 
   The horizontal axis indicates the time axis, and  4600  to  4602  denote the effective time limits corresponding to the objects  4500  to  4502 , respectively. The jagged end of the effective time limit indicates that the effective time limit is not set. For example, before Jun. 30, 2004, from Aug. 1, 2004 to Dec. 31, 2004, and after Feb. 1, 2005, only the object  4500  and the object  4502  are reproduced. From Jul. 1, 2004 to Jul. 31, 2004, and from Jan. 1, 2005 to Jan. 31, 2005, all the objects are reproduced. 
   (14-3) Data Structure 
     FIG. 47  shows an example of a data structure to realize a Vclick AU with an effective time limit. 
   Reference numerals  400  to  403  are similar to those of  FIG. 4 , and  4700  denoting the effective time limit is added to these. The effective time limit  4700  can store plural effective time limits. 
     FIG. 48  shows an example of a data structure of the effective time limit  4700  of the Vclick AU. The meaning of each data element is as follows:
         “period_length” denotes the number of effective time limits stored; and   “data_bytes” denotes a data part of the object effective time limit.       
   The effective time limit stored in “data_bytes” is expressed by a pair of a start and an end of the effective time limit, and “period_length” denotes the number of the pairs. For example, when the object  4502  of  FIG. 46  is used as an example, since there are two effective time limits, that is, the effective time limit before Jul. 31, 2004 and the effective time limit from Jan. 1, 2005 to Jan. 31, 2005, “period_length” becomes 2. In the object  4501 , since the one effective time limit is set, “period_length” becomes 1. In the object  4500 , since the effective time limit is not set, “period_length” becomes 0. 
   “Data_bytes” denotes the data part of the effective time limit. In the case where the effective time limit is set, time limit attribute data described later in  FIG. 49  is stored in this portion. In the case where the effective time limit is not set, the size of “data_bytes” becomes 0. 
   (14-4) Data Structure of Time Limit Attribute of Object Effective Time Limit 
     FIG. 49  shows an example of a data structure of a time limit attribute of an object effective time limit. In this data structure, the effective time limit of repetition can also be expressed. Further, a combination of effective time limits, such as the fifth of each month from Jan. 1, 2005 to Dec. 31, 2005, can also be expressed. The meaning of each data element is as follows:
         “period_type” denotes a flag to express whether effective time limits are combined, and in a case where an effective time limit does not depend on another effective time limit, 00h is input, and in a case where it is combined with another effective time limit, 01h is input;   “begin_date” denotes a start date of the effective time limit with numerals of 8 characters, and the numerical characters are enumerated in order of year, month, and day, for example, Jun. 25, 2004 is “20040625”;   “begin_time” denotes a start time of the effective time limit with numerals of 6 characters, and the numerical characters are enumerated in order of hour, minute and second, for example, 20:59:45 is “205945”;   “end_date” similarly denotes an end date of the effective time limit; and “end_time” denotes an end time of the effective time limit. In the case where only the start of the effective time limit is expressed, null characters are stored in “end_date” and “end_time”. Similarly, in the case where only the end of the effective time limit is expressed, null characters are stored in “begin_date” and “begin_time”.       
   A repetition such as the fifth of each month is expressed such that “period_type” is 00h, “begin_date” is “****05”, “begin_time” is “000000”, “end_date” is “****05”, and “end_time” is “235959”. As stated above, a wild card is input to a portion which is not limited. 
   In the case where the combination of the effective time limits is expressed, plural time limit attributes are used, and in the value of “period_length”, the time limit attribute of the combination is also counted as one. That is, in this case, “period_length” becomes 2. For example, in the case where the fifth of each month from Jan. 1, 2005 to Dec. 31, 2005 is expressed, two time limit attributes are used, the effective time limit from Jan. 1, 2005 to Dec. 31, 2005 is set in the first time limit attribute, and the effective time limit of the fifth of each month is set in the second time limit attribute by using the wild card. In the first time limit attribute, “period_type” is set to 01h in order to indicate that the time limit attribute of the combination follows thereafter, and 00h is set in the second time limit attribute in order to indicate that a time limit attribute does not continue thereafter. 
   Specifically, the first time limit attribute becomes as follows: “period_type”=01h, “begin_date”=“20050101”, “begin_time”=“000000”, “end_date”=“20051231”, and “end_time”=“235959”. 
   The second time limit attribute becomes as follows: “period_type”=00h, “begin_date”=“******05”, “begin_time”=“000000”, “end_date”=******05, and “end_time”=“235959”. 
   In the combination of the effective time limits described here, although plural time limit attributes such as, for example, the fifth and fifteenth of each month from Jan. 1, 2005 to Dec. 31, 2005, can not be handled in one time limit attribute, when they are individually described, there is no problem. 
   (14-5) Correspondence Between Semantic Structure of Time Limit Attribute and Arrangement in Data_Bytes 
     FIG. 53  shows an example of the correspondence between the semantic structure of time limit attributes and the arrangement in “data_bytes” shown in  FIG. 48 . 
   A circle denotes one time limit attribute, a numeral in the circle denotes a value of “period_type”, an arrow of a solid line connecting the circles denotes a semantic relation of the time limit attributes, and squares at the lower part denote the arrangement in “data_bytes”. In this example, there are eight time limit attributes from 5300 to 5307, and time limit attributes of from the time limit attribute  5301  to the time limit attribute  5303 , and from the time limit attribute  5305  to the time limit attribute  5306  are combination time limit attributes. For example, there is expressed the relation of the time limit attribute  5305  denoting the period from Jan. 1, 2005 to Dec. 31, 2005 and the time limit attribute  5306  denoting the fifth of each month. As stated above, in the case where a time limit attribute follows, “period_type” is set to 01h, and when not so, it is set to 00h. In these time limit attributes, as shown in the drawing, in the case where there are time limit attributes of a combination, they are given priority and are stored in “data_bytes”. 
   (14-6) Procedure to Judge Inside and Outside of Effective Time Limit 
     FIG. 50  is a flowchart showing a procedure to judge the inside and outside of an effective time limit when a user specifies the exhibition of relevant content. 
   First, “period_length” is read and is stored in a variable $count, 01h is stored in a variable $prev_type to store “period_type” of a time limit attribute one before, and initialization is performed (step S 5000 ). 
   When the $count is positive, the procedure proceeds to step S 5002  and the processing continues, and when not so, the processing is ended (step S 5001 ). 
   At step S 5002 , TRUE is stored in a flag variable $result of a logical value to indicate the inside or outside of a time limit and initialization is performed (step  5002 ). This is used for an operation of subsequent step S 5006  when a time limit attribute of a combination appears first. 
   Subsequently, a next effective time limit attribute is read (step S 5003 ), and the $count is decremented (step S 5004 ). 
   It is checked whether the variable $prev_type is 01h (step S 5005 ), and in the case of 01h, that is, in the case where the time limit attribute of the combination continues, the logical product of a previous judgment result and this judgment result is stored in $result, and the procedure proceeds to step S 5008  (step S 5006 ). When not so, this judgment result is overwritten on the $result and is stored, and the procedure proceeds to step S 5008  (step S 5007 ). 
   At step S 5008 , the read “period_type” is stored in $pref_type (step  5008 ). In the case where the time limit attribute continues thereafter, and the present time is within the effective time limit, that is, in the case where “period_type” is 01h and $result is TRUE, the procedure returns to step S 5003 , and the operation of the time limit attribute of the combination is repeated. When not so, the procedure proceeds to step S 5010  (step S 5009 ). 
   At step S 5010 , in order to judge whether the present time is within the effective time limit, in the case where $result is TRUE, the procedure is ended, and when not so, the procedure returns to step S 5002 , and the time limit attribute is read (step S 5010 ). 
   With respect to a final judgment as to whether the present time is within the effective time limit, when the value of $result at the time when these steps are ended is TRUE, it is within the effective time limit, and when not so, it is judged to be outside the effective time limit. 
   (15) Modified Example of Vclick AU Effective Time Limit 
   In the above embodiment, although the metadata is stored in the DVD in which the moving image is stored, and the relevant content on the network is exhibited, the invention is not limited to this, and the effective time limit may be set in relevant content stored in the DVD. 
   In the above embodiment, although the effective time limit of the Vclick AU is set, the intention is not limited to this, and the effective time limit may be set in specific object attribute information. For example, in the case where a contour line attribute and an action attribute are set, the effective time limit is set in only the action attribute, and the contour line may be displayed also in a period other than the effective time limit. In this case, an element to specify the object attribute has only to be added to the time limit attribute of the object effective time limit. 
   In the above embodiment, in the case where the object is outside the effective time limit, the object is made invalid, however, the invention is not limited to this, and an invalid object is previously detected, and newest metadata may be downloaded. 
   (16) Effective Time Limit of Vclick Stream 
   Next, a data structure in which an effective time limit is set in a Vclick stream will be described. Similarly to the effective time limit of the Vclick AU, the effective time limit here is a time limit defined with respect to an axis of absolute time such as a date of the Christian Era and a time, and is different from the effective period defined with respect to the time axis of the moving image. For example, in the case where the effective time limit is set in the whole hypermedia included in the Vclick stream at the same time, it is required. 
   A description will be given below to an example in which in a case where a moving image is stored in a DVD, and a Vclick stream is previously downloaded from a network and is stored in a reproduction apparatus, an effective time limit of the Vclick stream is judged. 
     FIG. 51  shows an example of a data structure to realize a Vclick stream with an effective time limit, and is another embodiment of the Vclick stream denoted by  507  of  FIG. 5 . The data structure is such that an effective time limit of a Vclick AU similar to  FIG. 48  is added to the header of the Vclick stream of  FIG. 11 . The meanings of respective data elements are such that “period_length” denotes the number of effective time limits stored, and “data_bytes” denotes a data part of the effective time limit of the Vclick stream. 
     FIG. 52  is a flowchart showing a procedure to judge the inside and outside of the effective time limit of the stored Vclick stream when a user issues an instruction to start reproduction. First, when the instruction to start the reproduction is input from the user (step S 5100 ), it is judged whether the Vclick stream is within the effective time limit (step S 5101 ), and when it is within the effective time limit, the currently stored Vclick stream is used as it is, and when not, the Vclick stream is downloaded from the network (step S 5102 ). Further, in order to judge whether the downloaded Vclick stream is within the effective time limit, it is judged whether the Vclick stream is within the effective time limit (step S 5103 ), and when it is within the effective time limit, the Vclick stream is replaced by a newly downloaded one (step S 5104 ), and when not so, the Vclick stream is deleted. 
   According to the above embodiment, an expiration date can be set in a Vclick stream, and for example, an effective time limit of the Vclick stream is set to one year, and a new Vclick stream is made to be downloaded periodically. 
   (17) Modified Example of Effective Time Limit of Vclick Stream 
   In the above embodiment, although the new Vclick stream is downloaded in the case where the Vclick stream is outside the effective time limit, the invention is not limited to this, and when it is outside the effective time limit, the Vclick stream may be immediately deleted. 
   Also in the case where the Vclick stream exists in the same recording medium as the DVD or the like storing the moving image, a similar processing can be performed. However, since the Vclick stream existing in the recording medium can not be deleted, at step S 5105 , it may be made invalid instead of being deleted. 
   Also in the case where the download of the Vclick stream ends in failure, it may be judged that the Vclick stream is outside the effective time limit. 
   (18) Second Embodiment of Effective Time Limit of Vclick Stream 
   Next, a method of describing an effective time limit of a Vclick stream in a Vclick information file will be described.  FIG. 54  shows an example of the Vclick information file describing the effective time limit of the Vclick stream. 
   In  FIG. 54 , two Vclick streams (Vclick stream #1, Vclick stream #2) are added to one PGC (PGC #5). In the example of  FIG. 54 , although the two Vclick streams are recorded in the local disk, they may be recorded on a server. Here, a “begin_date” attribute in an &lt;object&gt; tag expresses a start date of an effective time limit, and has the same meaning as “begin_date” explained by use of  FIG. 49 . Similarly, “begin_time”, “end_date”, and “end_time” of  FIG. 54  also correspond to audio stream numbers of  FIG. 49 , and in this example, they have the same meaning as “begin_time”, “end_date”, and “end_time” of the DVD video content, respectively. In the description of  FIG. 54 , the effective time limit of the Vclick stream #1 (Vclick1.vck) is till Jul. 31, 2004 and from Jan. 1, 2005 to Jan. 31, 2005. On the other hand, the Vclick stream #2 (Vclick2.vck) is effective from Aug. 1, 2004 to Dec. 31, 2004. There is no effective Vclick stream after Feb. 1, 2005. 
   As shown in  FIG. 51 , in the case where the effective time limit data is embedded in the header of the Vclick stream, with respect to Vclick streams as candidates for reproduction, it is necessary to analyze all effective time limit data to select a suitable Vclick stream. However, in the method of describing the effective time limit in the Vclick information file, it becomes possible to select the suitable Vclick stream without analyzing the header of the Vclick stream. 
   (19) Modified Example 
   Incidentally, the present invention is not strictly limited to the foregoing embodiments, and at a practical stage, the structural elements can be variously modified and can be embodied within the scope not departing from the gist of the invention. 
   For example, the invention can be applied to not only a DVD-ROM video popular on a global scale at present, but also a recordable/reproducible DVD-VR (video recorder) whose demand is rapidly increased in recent years. Further, the invention can also be applied to a reproduction system or a recording/reproduction system of a next generation HD-DVD which appears to become popular in near future. 
   Besides, by suitably combining the plural structural elements disclosed in the embodiment, various inventions can be structured. For example, some structural elements may be deleted from all structural elements disclosed in the embodiment. Further, structural elements of different embodiments may be suitably combined.