Patent Publication Number: US-2012033942-A1

Title: Enhanced navigation system using digital information medium

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present continuation application claims the benefit of priority under 35 U.S.C. 120 to application Ser. No. 10/372,899, filed Feb. 26, 2003, and claims the benefit of priority under 35 U.S.C. 119 from Japanese Patent Application No. 2002-049749 filed Feb. 26, 2002, the entire contents of both of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an enhanced navigation system that uses a digital information medium complying with the DVD-Video standard. 
     More specifically, the present invention relates to a DVD video playback system which acquires navigation information from the recorded contents on a DVD video disc and/or the Internet or the like, and allows diversified playback using the acquired navigation information compared to conventional DVD-Video. 
     2. Description of the Related Art 
     Currently, as package media of digital video, DVD-Video has become increasingly prevalent. The DVD-Video is specified by [DVD Specifications for Read-Only Disc: Part 3: VIDEO SPECIFICATIONS: Version 1.0 (CONFIDENTIAL)] issued August 1996 from the DVD forum. 
     The DVD-Video standard specifies presentation data that records actual video•audio (or AV) data, and navigation data used to manage such data. In this standard, presentation data (playback information) that contain video (moving image/still image) data, audio data, sub-picture data, and the like are multiplexed according to the specifications of a program stream (2048 bytes). The navigation data (management information) describes program chains (PGC) and cells which set the time configuration and playback order of video•audio data to be played back, thus implementing functions such as multi-angle playback, multi-story playback, and parental control (access control for children and the like). 
     However, a conventional DVD-Video player based on the DVD-Video standard (version 1.0) can play back only an MPEG2 program stream recorded on a DVD video disc (information recording medium). For this reason, even when information other than the MPEG2 program stream is recorded on the DVD video disc, existing DVD-Video players cannot play back information other than the MPEG2 program stream. 
     As the prior art that can store information (Hypertext information/HTML, programs, script macros, and the like) other than an MPEG2 program stream (DVD-Video contents) on a storage medium such as a DVD or the like, and can play back information other than the MPEG2 program stream, for example, “Data Storage Method for Storage Media, and Interactive Video Playback Apparatus” disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-136314 is known. This reference discloses an interactive video playback method and apparatus that play back multimedia information from package media such as optical discs and the like, and network media such as network servers and the like. In this reference, a recording medium stores specific condition playback data (program, script macro, and the like). 
     However, this reference does not have any concrete disclosure about a method of incorporating information (HTML, script, and the like) other than the current DVD-Video standard in the data structure of the current DVD-Video standard (version 1.0). Hence, there is no assurance that a DVD disc that includes the technique of this reference is compatible to the current DVD-Video standard. (This reference merely quotes “DVD” as an example of recording media, and does not take compatibility to the current DVD-Video standard into account.) Nevertheless, if the compatibility to the current DVD-Video standard (version 1.0) is not taken into consideration, the aforementioned problem “the conventional DVD-Video player cannot play back information other than the MPEG2 program stream” can be solved. That is, a conventional personal computer with a DVD-ROM/DVD-RAM drive can play back information other than the MPEG2 program stream, e.g., a computer program (not MPEG-encoded) recorded on a DVD-ROM. 
     Also, the current DVD-Video standard (version 1.0) can assure some interactive features with the user such as multi-angle playback, multi-story playback, and the like. However, such interactive features are fixed to some extent after contents production of a DVD video disc, and it is difficult to add a wide variety of interactive features to a DVD video disc that has undergone contents production. 
     As a method of adding a wide variety of interactive features after contents production, a method of importing information (playback control information described in a markup language, script language, or the like, data that this playback control information refers to, and so forth) used to add interactive features from the Internet or the like to a DVD-Video player may be used. A disclosure in Jpn. Pat. Appln. KOKAI Publication No. 10-136314 above is close to this concept (this reference describes an interactive video playback method for playing back multimedia information from network media). 
     However, upon acquiring multimedia information from network media and adding a wide variety of interactive features by the playback method of a DVD video disc, since the invention of the above reference does not practically take the compatibility to the current DVD-Video standard (version 1.0) into account, how to control the playback contents (video contents) of an actual DVD video disc cannot be specifically recognized upon interactively controlling the actual DVD video disc (not a DVD-ROM that records computer data and the like but a DVD video disc) using information imported from the Internet or the like. 
     As another reference related to the aforementioned parent publication, “Data Synchronous Playback Apparatus for a Plurality of media” disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-98467 is known. In this reference, a required image downloaded from the Internet is stored in an internal storage unit, disc information and external medium information are synchronously mixed and displayed on the basis of the stored image, and timing data and a layout signal stored in an internal disc. 
     With the invention of this reference, information in the internal disk, and information acquired from the Internet can be synchronously displayed. However, this invention has no function of selecting various display methods as needed, e.g., a method of displaying disc information alone, a method of displaying Internet acquired information alone, and a method of displaying those pieces of information at different timings. Especially, Jpn. Pat. Appln. KOKAI Publication No. 11-98467 has no disclosure about control for Internet acquired information in accordance with the playback state of a DVD disc. Also, this invention does not have any function of giving the switching timings of these various display methods in accordance with a user&#39;s instruction or playback control information recorded in advance on a disc (or playback control information downloaded from the Internet). 
     Furthermore, since the invention of this reference does not practically take the compatibility to the current DVD-Video standard (version 1.0) into account, how to control the playback contents (video contents) of an actual DVD video disc (more specifically, the types and timings of control signals, and their sources and destinations) upon interactively controlling the actual DVD video disc using information downloaded from the Internet or the like is not apparent. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention has its object to provide an enhanced navigation system that can add a wide variety of interactive features to playback of AV (video and/or audio) contents after production while assuring the compatibility (at least upward compatibility) to the current or legacy DVD-Video (and/or Audio) standard. 
     In order to achieve the above object, an information medium (optical disc, hard disc, etc.) according to an aspect of the present invention, which can be used to form the aforementioned system, may have a lead-in area, volume space, and lead-out area, and the volume space, includes a volume/file structure information area, video area, and/or another recording area. In this information medium, the video area includes AV contents complying with the DVD-Video (or Audio) standard, and the other recording area can include navigation contents which can be played back in association with the contents (menus, chapters) of the video contents. The navigation contents have contents that control to play back the AV contents in connection, combination, and/or synchronism with playback of the navigation contents. 
     An apparatus according to an aspect of the present invention, which forms the aforementioned system, may comprise a player unit, a video playback engine, and a navigation engine. The player unit is configured to play back recorded contents, that contents may include AV contents and navigation contents which can be played back in association with the playback contents (menus, chapters) of the video contents, from a digital video (or audio) disc. This disc may have a volume space complying with the DVD-Video (or Audio) standard. The video playback engine is configured to play back the AV contents of the recorded contents on the disc. The navigation engine is configured to play back the navigation contents of the disc, and is configured to control playback of the navigation contents in connection with the AV contents according to the navigation contents. 
     In an apparatus according to another aspect of the present invention, which forms the aforementioned system, the navigation engine has a first interface configured to receive the navigation contents from a digital video disc having a volume space complying with the DVD-Video (or Audio) standard, and a second interface configured to acquire other navigation contents via a communication line (such as Internet). 
     Assume that a state in which the digital video disc is loaded to the player unit, and the second interface is disconnected from the communication line (net disconnected) is an off-line mode. Also, a state in which the digital video disc is ejected from the player unit, and the second interface is connected to the communication line (net connected) is assumed to be an on-line mode. Furthermore, a state in which the digital video disc is loaded to the player unit, and the second interface is connected to the communication line (net connected) is assumed to be a mixed mode. Then, upon detection of a predetermined switch trigger (a trigger generated in response to insertion/ejection of a disc or connection/disconnection of a net; corresponding to mode switch events), mode transition is automatically made among the off-line mode, on-line mode, and mixed mode in accordance with a predetermined transition rule. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a block diagram for explaining an example of the arrangement of a “DVD-Video player incorporating an enhanced navigation system (ENAV system)” according to an embodiment of the present invention; 
         FIGS. 2A-2C  are views for explaining a display example upon outputting a playback video on the DVD-Video contents side and that on the ENAV contents side as a multi-frame output in the arrangement shown in  FIG. 1 ; 
         FIGS. 3A-3C  are views for explaining a display example upon outputting a playback video on the DVD-Video contents side and that on the ENAV contents side on multi-windows (overlapping windows) in the arrangement shown in  FIG. 1 ; 
         FIGS. 4A-4E  are views for explaining an example upon mixing a playback audio on the DVD-Video contents side and that on the ENAV contents side in the arrangement shown in  FIG. 1 ; 
         FIG. 5  is a view for explaining an example of changes in DVD video playback output (DVD video menu) and ENAV playback output (ENAV menu) in correspondence with an internal command; 
         FIG. 6  is a flow chart for explaining an example of the processes of a DVD-Video playback engine and ENAV engine in association with menu call by a command; 
         FIG. 7  is a view for explaining a menu display example (full video mode) on the video contents side; 
         FIG. 8  is a view for explaining a menu display example (full ENAV mode) on the ENAV contents side; 
         FIG. 9  is a view for explaining an example of changes in DVD video playback output 
       (DVD video chapter playback) and ENAV playback output (ENAV contents playback) in correspondence with an internal command; 
         FIG. 10  is a flow chart for explaining an example of the processes of the DVD-Video playback engine and ENAV engine in association with chapter playback; 
         FIG. 11  is a view for explaining a display example (mixed frame mode) of a mixed menu of the video and ENAV contents; 
         FIG. 12  is a view for explaining a display example (mixed frame mode) of a mixed video of the video and ENAV contents; 
         FIG. 13  is a view for explaining an example of changes in DVD video playback output (DVD video menu) and ENAV playback output (ENAV menu) in correspondence with user&#39;s operation (user event); 
         FIG. 14  is a flow chart for explaining an example of the processes of the DVD-Video playback engine and ENAV engine in association with menu call by the user; 
         FIG. 15  is a view for explaining an example of changes in DVD video playback output (DVD video menu or playback pause) and ENAV playback output (ENAV menu) in correspondence with user&#39;s operation (user event); 
         FIG. 16  is a flow chart for explaining an example (first half) of the processes of the DVD-Video playback engine and ENAV engine in association with menu call or playback pause by the user; 
         FIG. 17  is a flow chart for explaining an example (second half) of the processes of the DVD-Video playback engine and ENAV engine in association with menu call or playback pause by the user; 
         FIGS. 18A-18C  are views for explaining a case wherein ENAV content  1  is played back before playback of chapter 1, and ENAV content  2  is played back in synchronism with playback of chapters 1 and 2 when the DVD-Video playback engine successively plays back chapters 1 to 4; 
         FIG. 19  is a view for explaining a case (case 1) wherein the DVD-Video playback engine outputs a PTT event with a chapter number as a DVD event at the beginning of each chapter, and the ENAV engine begins to play back corresponding ENAV contents; 
         FIG. 20  is a view for explaining a case (case 2) wherein the DVD-Video playback engine exchanges event/status data with the ENAV engine, and the ENAV engine plays back ENAV contents on the basis of the exchange result; 
         FIG. 21  is a view for explaining another case (case 3) wherein the DVD-Video playback engine outputs a PTT event with a chapter number as a DVD event at the beginning of each chapter, and the ENAV engine begins to play back corresponding ENAV contents; 
         FIG. 22  is a flow chart for explaining an operation example of the DVD-Video playback engine, an event generation•command/property processor, and an ENAV interpreter in correspondence with the case of  FIG. 19  (case 1); 
         FIG. 23  is a flow chart for explaining an operation example of the DVD-Video playback engine, event generation•command/property processor, and ENAV interpreter in correspondence with the case of  FIG. 20  (case 2); 
         FIG. 24  is a flow chart for explaining an operation example of the DVD-Video playback engine, event generation•command/property processor, and ENAV interpreter in correspondence with the case of  FIG. 21  (case 3); 
         FIG. 25  is a view for explaining selectable paths among a plurality of modes (off-line mode, on-line mode, mixed mode) in the system arrangement of  FIG. 1 ; 
         FIG. 26  is a flow chart for explaining an example of which one of the plurality of modes shown in  FIG. 25  is set first; 
         FIG. 27  is a flow chart for explaining an example of the processing contents in the current mode (one of the plurality of modes shown in  FIG. 25 ); 
         FIG. 28  is a flow chart for explaining a processing example when the current mode automatically transits to another mode depending on whether or not a DVD disc is inserted in a DVD-Video player, whether or not an Internet connection unit is connected to the Internet, and the like, which are determined in the state check steps in the process shown in  FIG. 27 ; 
         FIG. 29  is a view for explaining an example of a transition rule which is referred to upon determining the mode transition destination in the process shown in  FIG. 28 ; 
         FIG. 30  is a view for explaining an example of a DVD video disc which can be played back by the DVD-Video player in  FIG. 1 , and in which ENAV contents  30  are stored in an area other than a DVD-Video area; 
         FIG. 31  is a view for explaining an example of a DVD video disc which can be played back by the DVD-Video player in  FIG. 1 , and in which ENAV contents  30  are stored in a DVD-Video area; 
         FIG. 32  is a view for explaining a video output result on the basis of a layout control signal shown in  FIG. 1 ; 
         FIG. 33  is a view for explaining an audio output result on the basis of a layout control signal shown in  FIG. 1 ; and 
         FIG. 34  is a flow chart for explaining an example of recording processes of information on an information medium such as a DVD-Video disc, DVD-Audio disc, a hard disc, or the like. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An “enhanced navigation system using a digital information medium” according to various embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. The following explanation will be given under the condition, for example, that this system is applied to a playback apparatus and method of a DVD video disc complying with the DVD-Video standard. 
     The data structure of a disc that takes the compatibility with the existing DVD-Video standard (version 1.0) into account will be described first. 
       FIG. 30  shows an example of the data structure of DVD video disc  1  which can be played back by DVD-Video player  100  in  FIG. 1  (to be described later). In this example, DVD-Video contents  10  (having an MPEG2 program stream structure) with the same data structure as the conventional DVD-Video standard (version 1.0) are stored in a DVD-Video area. Also, enhanced navigation (to be abbreviated as ENAV hereinafter) contents  30 , which allow diversified playback of video contents (or AV contents)  10 , can be recorded in another recording area, the presence of which is officially recognized in the DVD-Video standard. 
     Since the contents of the DVD-Video area are conventionally known (to those who are skilled in the art such as the manufacturers of DVD-Video players and the like), they will be briefly explained below. 
     More specifically, the recording area of DVD video disc  1  includes a lead-in area, volume space, and lead-out area in turn from the inner periphery. The volume space includes a volume/file structure information area, and DVD-Video area (DVD-Video zone), and can also include another recording area (DVD-Other zone) as an option. 
     The volume/file structure information area is assigned for the UDF (Universal Disk Format) bridge structure. The volume of the UDF bridge format is recognized in accordance with ISO/IEC13346 Part 2. A space that recognizes this volume consists of successive sectors, and starts from the first logical sector of the volume space in  FIG. 30 . First 16 logical sectors are reserved for system use specified by ISO9660. In order to assure the compatibility to the existing DVD-Video standard (version 1.0), the volume/file structure information area with such contents is required. 
     The DVD-Video area records management information called video manager VMG and one or more video contents (or AV contents) called video title sets VTS (VTS# 1  to VTS#n). VMG is management information for all VTSs present in the DVD-Video area, and contains control data VMGI, VMG menu data VMGM_VOBS (option), and VMG backup data (none of them are shown). Each VTS contains control data VTSI of that VTS, VTS menu data VTSM_VOBS (option), data VTSTT_VOBS of the contents (movie or the like) of that VTS (title), and VTSI backup data (none of them are shown). To assure the compatibility to the existing DVD-Video standard (version 1.0), the DVD-Video area with such contents is also required. 
     A playback select menu or the like of each title (VTS# 1  to VTS#n) is given in advance by a provider (the producer of DVD video disc  1 ) using VMG, and a playback chapter select menu, the playback order of recorded contents (cells), and the like in a specific title (e.g., VTS# 1 ) are given in advance by the provider using VTSI. Therefore, the viewer of disc  1  (the user of the DVD-Video player) can enjoy the recorded contents of that disc  1  in accordance with menus of VMG/VTSI prepared in advance by the provider and playback control information (program chain information PGCI) in VTSI. However, with the conventional DVD-Video standard (version 1.0), the viewer (user) cannot play back the contents (movie or music) of each VTS by a method different from VMG/VTSI prepared by the provider. 
     ENAV contents (or ENAV content)  30  in  FIG. 30  are prepared as a mechanism that allows the user to play back the contents (movie or music) of each VTS by a method different from VMG/VTSI prepared by the provider, and to play back while adding contents different from VMG/VTSI prepared by the provider. ENAV contents  30  cannot be accessed by a DVD-Video player which is manufactured on the basis of the conventional DVD-Video standard (version 1.0) (even if ENAV contents  30  can be accessed, their contents cannot be used). However, a DVD-Video player (player  100  in  FIG. 1  or the like) can access ENAV contents  30 , and can use their playback contents. 
     Logically, ENAV contents  30  can be classified into ENAV playback information, and the data body of ENAV contents. The data body of ENAV contents contains audio data, still image data, text data, moving image data, and the like. The ENAV playback information contains a markup language, script language, or the like, which describes playback methods (display method, playback order, playback switch sequence, selection of data to be played back, and the like) of the ENAV contents data body and/or DVD-Video contents  10 . For example, as a language used as the playback control information, markup languages such as HTML (Hyper Text Markup Language)/XHTML (eXtensible Hyper Text Markup Language), SMIL (Synchronized Multimedia Integration Language), and the like, script languages such as ECMA (European Computer Manufacturers Association) Script, JavaScript, and the like, and so forth can be used in combination. The description contents of the ENAV playback information described in these languages are parsed by ENAV interpreter  330  in  FIG. 1  to interpret the parsed contents. 
     More specifically, the ENAV playback information can contain file information of the ENAV contents (information of a file to be referred to, and information of a file to be referred to instead if the file to be referred to is not present or if a player does not have a function of decoding the file if that file is present), layout information (the coordinate position of an object to be displayed on a display screen, and information indicating the depth ordering if that object overlaps another object), size information (information indicating the size of each object to be displayed), synchronization information (information used to control to play back the DVD-Video contents in connection or combination with that of the ENAV contents at a predetermined timing), and duration information (information indicating the display time range or timing range of the ENAV contents). 
     Using the ENAV playback information, for example, output methods menu, video, and/or audio data contained in video contents  10  or ENAV contents  30  can be described (see  FIGS. 7 ,  8 , and  11  to be described later for an example of a menu output method; see  FIGS. 2 ,  3 , and  12  to be described later for an example of a video output method; see  FIGS. 4A-4E  to be described later for an example of an audio output method). 
     In DVD video disc  1  in  FIG. 30 , since the contents other than the other recording area comply with the current DVD-Video standard (version 1.0), video contents  10  recorded on the DVD-Video area can be played back using the conventional DVD-Video player (i.e., the compatibility to the conventional player can be assured). 
     ENAV contents  30  recorded in the other recording area cannot be played back (or cannot be used) by the conventional DVD-Video player, but can be played back and used by the DVD-Video player ( FIG. 1 ) according to an embodiment of the present invention. Therefore, when ENAV contents  30  are played back using the DVD-Video player according to an embodiment of the present invention, various video playback processes can be made without being limited by only the contents of VMG/VTSI prepared in advance by the provider (examples of such various video playback processes will be explained later with reference to  FIGS. 1 to 29  as needed). 
     In the arrangement of  FIG. 30 , the aforementioned ENAV playback information can be physically recorded on disc  1  together with the ENAV contents data body or independently. 
     As a method for the former allocation, ENAV dedicated packs ENV_PCK may be assured at, e.g., the head of an access unit (corresponding to video object unit VOBU in the current DVD-Video standard) (or after navigation pack NV_PCK located at the head in VOBU), and the ENAV playback information may be recorded in these packs ENV_PCK while being repacked into smaller sizes. 
     As a method for the latter allocation, an area independent from the ENAV contents data body may be assured like VMG (or VTSI) in the DVD-Video area, and the ENAV playback information may be recorded in this area. With this method, the DVD-Video player ( FIG. 1 ) according to an embodiment of the present invention preferably reads the ENAV playback information prior to the ENAV contents data body (if an ENAV playback control method is read and stored in a memory in advance, a process of the ENAV contents data body can be started without any delay when the ENAV contents data body is read). 
     To summarize, disc  1  in  FIG. 30  can be considered as an information medium with the following arrangement. That is, this information medium has a lead-in area, volume space, and lead-out area, and the volume space includes a volume/file structure information area, video area, and another recording area in conformity to the DVD-Video standard. The video area includes video contents  10  complying with the DVD-Video standard, and the other recording area includes navigation contents  30  which can be played back in association with the contents (menus, chapters, and the like) of video contents  10  (see  FIGS. 5 ,  9 , and the like to be described later). Navigation contents  30  have contents that control to play back video contents  10  in connection, combination, or synchronism with playback of navigation contents  30  (see broken arrows in  FIGS. 21 to 23 ). 
       FIG. 31  shows another example of the data structure of DVD video disc  1  that can be played back by DVD-Video player  100  in  FIG. 1  (to be described later). In this example, DVD-Video contents  10  (having an MPEG2 program stream structure) having the same data structure as the conventional DVD-Video standard (version 1.0) are stored in a DVD-Video area, and ENAV contents  30  that can diversify playback of video contents  10  can be recorded on the end side of this DVD-Video area (after the recording end position of video contents  10 ). 
     Alternatively, ENAV contents  30  that cannot be accessed by the conventional DVD player but can be accessed by the DVD player according to an embodiment of the present invention can be recorded between a given video title set (VTS#i) and another video title set (VTS#j≠VTS#i) although not shown. As an example of a practical method of inhibiting the conventional DVD player from accessing contents  30 , ENAV contents  30  may be allowed to be accessed using only commands (e.g., a Jump command, GoTo command, and the like having special operation codes) which are not specified by the conventional DVD-Video standard (version 1.0). 
     If VMG or VTSI described above with reference to  FIG. 30  is described to refer to only the recorded area (addresses) of DVD-Video contents  10 , the conventional DVD-Video player never accesses ENAV contents  30  with reference to VMG or VTSI. On the other hand, in the DVD-Video player according to an embodiment of the present invention, an ENAV mode that activates ENAV may be prepared, and access to the end of the DVD-Video area may be allowed in this ENAV mode. In this way, the DVD-Video player ( FIG. 1 ) according to an embodiment of the present invention can access ENAV contents  30  recorded on the end side of the DVD-Video area, and can use their contents. 
     To summarize, disc  1  in  FIG. 31  can be considered as an information medium with the following arrangement. That is, this information medium has a lead-in area, volume space, and lead-out area, and the volume space includes a volume/file structure information area and video area. The video area includes video contents  10  complying with the DVD-Video standard, and navigation contents  30  which can be played back in association with the contents (menus, chapters, and the like) of video contents  10 . Navigation contents  30  have contents that control to play back video contents  10  in connection, combination, or synchronism with playback of navigation contents  30 . 
     As practical methods of playing back ENAV contents  30  recorded on disc  1  in  FIG. 30  or  31 , for example, a method of providing a select button of ENAV contents  30  to a DVD menu (VMG menu or VTS menu), and allowing the user to select the ENAV contents button by operating cursor keys and an enter key, and a method of automatically accessing ENAV contents  30  based on internal commands (navigation commands such as a GoTo command, Jump command, and the like) of the DVD-Video player are available. 
     When the select button of the former method is used, for example, the following process may be done. That is, the user selects (selection) and determines (action) a button (ENAV contents select button in this case) displayed on a menu, thereby playing back contents (ENAV contents  30  in this case) corresponding to that button. This method is the same as that adopted in existing DVD-Video players. 
     When the internal commands of the latter method are used, for example, a GoTo command consists of an operation code, reserved area, and GoTo operand. This command format remains the same to maintain the compatibility to the conventional DVD-Video standard (version 1.0), but the contents of the operation code and operand can be changed according to an embodiment of the present invention. For example, since operation codes “0000h” to “0003h” have contents that have already been specified by the DVD-Video standard (version 1.0), an embodiment of the present invention specifies a new operation code “0004h” that makes the control go to ENAV contents  30 . Information indicating the recorded location of ENAV contents  30  can be written in the operand of that GoTo command. 
     A Jump command consists of an operation code, Jump operand, and reserved area. This command format remains the same to maintain the compatibility to the conventional DVD-Video standard (version 1.0), but the contents of the operation code and operand can be changed according to an embodiment of the present invention. For example, since operation codes “3001h” to “3008h” have contents that have already been specified by the DVD-Video standard (version 1.0), an embodiment of the present invention specifies a new operation code “3009h” that make the control jump to ENAV contents  30  as an operation code of the Jump command. Information indicating the recorded location of ENAV contents  30  can be written in the operand of that Jump command. 
     Note that DVD-Video contents  10  of DVD video disc  1  exemplified in  FIG. 30  or  31  are not limited to a movie, multi-story drama, music program with multi-angle video data, and the like, and may contain software such as a computer game which is required to have high interactive features. 
       FIG. 1  is a block diagram for explaining an example of the arrangement of “DVD-Video player  100  that incorporates the enhanced navigation system (ENAV system) according to an embodiment of the present invention. This DVD-Video player  100  plays back and processes the recorded contents (DVD-Video contents  10  and/or ENAV contents  30 ) from enhanced DVD video disc  1  “compatible to the conventional DVD-Video standard (version 1.0)” shown in  FIG. 30  or  31 , and imports and processes ENAV contents (a kind of Web contents)  30 W from a communication line such as the Internet or the like. 
     In the block arrangement shown in  FIG. 1 , DVD-Video playback controller  220 , user event controller  310 , event generation•command/property processor  320 , ENAV interpreter  330 , and the like can be implemented by a microcomputer (and/or hardware logic) which serves the functions of respective blocks based on an embedded program (firmware) (not shown). More specifically, the processes of the flow charts shown in  FIG. 6  and the like can be implemented by a microcomputer (not shown) that executes the firmware. A work area used upon executing the firmware can be assured using a semiconductor memory (not shown) (and a hard disc as needed) in the block arrangement. 
     Disc  1  to be played back by player  100  in  FIG. 1  records DVD-Video contents  10  having an MPEG2 program stream structure, and ENAV contents  30  that contain information (video information such as a moving image, still image, animation, and the like, audio information, text information, and the like) other than the MPEG2 program stream structure. Web contents such as video information, audio information, text information, and the like, which are acquired from the Internet or the like are downloaded to player  100  as ENAV contents  30 W. 
     In this embodiment, all kinds of video•audio•text information other than the MPEG2 program stream recorded on disc  1  will be referred to as “ENAV contents (Enhanced Navigation contents)”. The ENAV contents contain information (ENAV playback information) that controls to play back such video•audio•text information in synchronism (or connection or combination) with DVD-Video contents  10 , in addition to the video•audio•text information. 
     DVD-Video player  100  in  FIG. 1  comprises DVD-Video playback engine  200  for playing back and processing the MPEG2 program stream (DVD-Video contents  10 ) recorded on disc  1 , and ENAV engine  300  for playing back and processing ENAV contents  30  (and/or  30 W). This player  100  further comprises a disc unit (normally configured as a DVD disc drive: since this unit can be configured by the prior art, a detailed arrangement thereof is not shown) for reading out DVD-Video contents  10  and/or ENAV contents  30  recorded on disc  1 , a user operation unit (a control panel of player  100  and/or remote controller: a detailed arrangement thereof is not shown) for transmitting user&#39;s inputs (user&#39;s operation  40 ), and an Internet connection unit for connecting a communication line such as the Internet or the like. 
     DVD-Video playback engine  200  is a device for playing back DVD-Video contents  10  on the basis of the existing DVD-Video standard (version 1.0), and includes decoder unit  210  for decoding DVD-Video contents  10  read by the disc unit, and DVD-Video playback controller  220  for controlling playback of DVD-Video contents  10 . 
     Decoder unit  210  has a function of decoding video data, audio data, and sub-picture data based on the existing DVD-Video standard, and outputting decoded video•audio data D 210 . With this function, DVD-Video playback engine  200  has the same function as that of a playback engine of a normal DVD-Video player, which is manufactured on the basis of the existing DVD-Video standard (version 1.0). That is, player  100  of  FIG. 1  can play back video data, audio data, and the like having the MPEG2 program stream structure in the same manner as a normal DVD-Video player and, hence, can play back existing DVD video discs (discs complying with the DVD-Video standard version 1.0). 
     In addition, DVD-Video playback controller  220  can control playback of DVD-Video contents  10  in accordance with a “DVD control signal” output from ENAV engine  300 . More specifically, when a given event (e.g., menu call or title jump) has occurred during DVD-Video playback, DVD-Video playback controller  220  can output a “DVD event signal” indicating the playback condition of DVD-Video contents  10  to ENAV engine  300 . In this case (simultaneously with output of the DVD event signal or an appropriate timing before or after that output timing), DVD-Video playback controller  220  can output a “DVD status signal” indicating property information (e.g., an audio language, sub-picture caption language, playback operation, playback position information, time information, the contents of disc  1 , and the like set in player  100 ) of DVD-Video player  100  to ENAV engine  300 . 
     ENAV engine  300  includes user event controller  310 , event generation•command/property processor  320 , ENAV interpreter  330 , element decoder  340 , and video•audio output unit  350 . 
     User event controller  310  makes control based on user&#39;s operations  40 . Controller  310  receives user events corresponding to user&#39;s operations (menu call, title jump, playback start, playback stop, playback pause, and so forth) from the user operation unit, or receives a user event control signal from event generation•command/property processor  320 , and generates user events (A) to (C) corresponding to the contents of user&#39;s operations or the user event control signal. 
     In the arrangement in  FIG. 1 , based on the “user event control signal” output from event generation•command/property processor  320 , user event controller  310   
     transmits a user event signal transmitted based on user&#39;s operation  40  to DVD-Video playback controller  220  (user event signal (A)), 
     inhibits transmission (“X”) (user event signal (B)), or 
     transmits the user vent signal to event generation•command/property processor  320  (user event signal (C)). 
     At this time, a user event signal undergoes the following transmission control. 
     Upon outputting video data D 210  of DVD-Video playback engine  200  (full video mode), user event signal (A) is directly output to DVD-Video playback engine  200 . This is because user&#39;s operation  40  in the full video mode is the same as that in normal DVD-Video playback. 
     Upon outputting video data D 340  of ENAV engine  300  (full ENAV mode) or upon simultaneously outputting video data D 210  of DVD-Video playback engine  200  and video data D 340  of ENAV engine  300  by mixing them (mixed frame mode), the following control is made. 
     When a user event signal is output to event generation•command/property processor  320  (user event signal (C)), event generation•command/property processor  320  outputs as a DVD control signal a function call corresponding to that event (menu call or the like) to DVD-Video playback controller  220  of DVD-Video playback engine  200 . 
     A user event is simultaneously output to both DVD-Video playback engine  200  and event generation•command/property processor  320  (user event signals (A) and (C)). 
     When DVD-video playback that the system does not intend (for example, a playback method incompatible to currently running DVD-Video playback engine  200  or operation inhibited by user&#39;s operation control UOP specified by the current DVD standard) is more likely to be made, transmission of a user event signal is blocked (inhibited or deterred) (“X” of user event signal (B)). 
     Note that the contents of user event signal (C) transmitted to event generation•command/property processor  320  may be sent to ENAV interpreter  330  in the form of an ENAV event (and/or ENAV property) as needed. Then, ENAV interpreter  330  can generate a layout control signal with reference to the contents of user event signal (C). 
     For example, in  FIG. 3C  (to be described later), when the user has changed the window size of contents  10  or  30  or has shifted its display position using cursor keys of a remote controller (not shown), this operation is sent as user event signal (C) from user event controller  310  to event generation•command/property processor  320 . Processor  320  can convert that user event signal into a corresponding ENAV event (window size change event or the like) and/or ENAV property (a variable/parameter or the like indicating the window size after change), then convert the converted event and/or property into a corresponding layout control signal, and send the converted signal to video output controller  352 . 
     A further explanation of user event signals (A) to (C) will be given later with reference to the flow charts in  FIG. 14  and subsequent figures as needed. 
     Event generation•command/property processor  320  exchanges a DVD status signal, DVD event signal, and/or DVD control signal with DVD-Video playback controller  220 , or exchanges a user event and/or user event control signal with user event controller  310 . Furthermore, event generation•command/property processor  320  exchanges an ENAV event, ENAV property, and/or ENAV command with ENAV interpreter  330 . That is, event generation•command/property processor  320  serves as an interface between DVD-Video playback engine  200  and ENAV engine  300  by outputting an input DVD status signal as an ENAV property, outputting an input DVD event signal as an ENAV event signal, or converting an input ENAV command into a corresponding DVD control signal and outputting the DVD control signal. Event generation•command/property processor  320  sends a signal that controls the output state of video data and/or audio data to video•audio output unit  350  in accordance with the contents of the DVD status signal and DVD event signal from DVD-Video controller  220 , the user event from user event controller  310 , and/or the ENAV command from ENAV interpreter  330 . 
     In other words, event generation•command/property processor  320  is configured to exchange a first signal (DVD control signal, DVD event signal, DVD status signal) that pertains to the playback condition of DVD video disc  1  with DVD-Video playback controller  220 , and to exchange a second signal (ENAV event, ENAV command, ENAV property) that pertains to the contents (script) of ENAV contents  30  (and/or  30 W) with ENAV interpreter  330 , on the basis of the contents (command) interpreted by ENAV interpreter  330  or the user event from an input device, and controls the signal output state of video•audio output unit  350  on the basis of at least one of the exchanged first and second signals. 
     Put differently, event generation•command/property processor  320  interprets ENAV contents  30  ( 30 W), and then converts a control signal and the like between DVD-Video playback engine  200  and ENAV engine  300 . More specifically, processor  320  makes, e.g., the following signal output/signal conversion: 
     &lt;A&gt; Processor  320  interprets ENAV contents  30  ( 30 W), and then outputs (a) a “user event control signal” used to control a user event corresponding to user&#39;s operation  40  input from the user operation unit, (b) a “DVD control signal” used to control playback of DVD-Video contents  10  in DVD-Video playback engine  200 , and/or (c) a “video•audio output control signal” used to switch between the video•audio output from DVD-Video playback engine  200  and that from ENAV engine  300 . 
     &lt;B&gt; Processor  320  interprets the contents (indicating if an event is menu call, title jump, or the like) of a “DVD event signal” which is sent from DVD-Video playback engine  200  and indicates the playback condition of DVD-Video contents  10 , and converts the contents of the interpreted DVD event signal into a corresponding event signal specified in ENAV contents  30  ( 30 W) (e.g., converts a DVD event signal of menu call into an event signal of menu call in ENAV). 
     &lt;C&gt; Processor  320  interprets the contents (indicating the current audio language, if the disc playback operation is now being done, and so forth) of a “DVD status signal” which is sent from DVD-Video playback engine  200  and indicates the property of DVD-Video player  100 , and converts the contents of the interpreted DVD status signal into a corresponding property signal specified in ENAV contents  30  ( 30 W) (e.g., converts a DVD status signal which indicates that the current audio language is Japanese into a property signal that designates Japanese as a language used by ENAV). 
     Generally speaking, ENAV interpreter  330  has a function of parsing and interpreting playback control information (ENAV playback information) contained in ENAV contents  30  acquired from DVD video disc  1  or ENAV contents  30 W acquired from the Internet or the like, and controlling ENAV engine  300 . As a script language used in ENAV playback information, the aforementioned markup languages such as HTML/XHTML, SMIL, and the like may be used, or script languages such as ECMAScript and the like may be used together with the aforementioned markup languages. 
     As a practical method of parsing and interpreting markups and scripts, the same method as the parsing &amp; interpretation method in the state-of-the-art techniques such as HTML, XHTML, and SMIL, or ECMAScript and JavaScript may be used (hardware to be used is the microcomputer mentioned at the beginning of the description of  FIG. 1 ). The ENAV playback information used upon practicing the present invention uses unique commands and variables associated with playback of the DVD video disc and/or ENAV contents. For example, a command that switches the playback contents of the DVD-Video or ENAV contents in response to a given event is unique to markups or scripts in the ENAV playback information. 
     As other examples of commands and variables unique to markups or scripts in the ENAV playback information, a command and variable for changing the size of a video from DVD-Video playback engine  200  and/or ENAV engine  300  (a command that instructs size change, and a variable that designates the size after change), and a command and variable for changing the position of the video (a command that instructs to change the display position, and a variable that designates a coordinate position after change: when objects to be displayed overlap each other on the screen, as shown in  FIG. 3C  (to be described later), a variable that designates the depth ordering of the overlapping objects is added) are used. Also, a command and variable which are sent from DVD-Video playback engine  200  and/or ENAV engine  300  and are used to change an audio level (a command that instructs to change an audio level, and a variable that designates an audio level after change), and a command and variable used to select an audio language to be used (a command that instructs to change an audio language to be used, and a variable that designates the type of language after change) are used. Furthermore, a command and variable that control a user event in user event controller  310  (those used to switch among user event signals (A), (B), and (C)) are used. 
     ENAV interpreter  330  sends a “layout control signal” that controls the layout on the screen of video data (video data D 352 ) to be displayed on an external monitor or the like (not shown), the size of video data, the output timing of video data, and the output duration of video data, and/or the tone volume level of audio data (audio data D 354 ) to be output from an external loudspeaker (not shown), the output timing of audio data, and the output duration of audio data to the video•audio output unit  350  on the basis of the commands/variables of markups and scripts of the ENAV playback information exemplified above. 
     Element decoder  340  decodes audio data, still image data, text data, moving image data, and the like contained in the ENAV contents, and includes an audio decoder, still image decoder, text decoder, and moving image decoder in correspondence with data to be decoded. For example, audio data in the ENAV contents encoded by, e.g., MPEG1 is decoded by the audio data and is converted into decompressed audio data. Still image data encoded by MPEG or JPEG is decoded by the still image decoder and is converted into decompressed image data. Likewise, moving image data encoded by, e.g., MPEG2 is decoded by the moving image decoder and is converted into decompressed moving image data. Also, text data contained in the ENAV contents is decoded by the text decoder, and is converted into text image data, which can be superimposed onto a moving or still image. Video-audio data D 340  which contains the decoded audio, image, moving image, and text image data is sent from element decoder  340  to video•audio output unit  350 . 
     Video•audio output unit  350  selects one of video•audio data D 340  decoded by element decoder  340  and video•audio data D 210  output from DVD-Video playback engine  200 , or mixes these data (D 340  and D 210 ) as needed. Unit  350  includes video output controller  352  and audio output controller  354 . 
     Video output controller  352  has a function of selecting video data (video part of D 210 ) from DVD-Video playback engine  200  or video data (video part of D 340 ) from ENAV engine  300 , and a function of changing the sizes of these video data (D 210  and D 340 ) and/or moving their positions, and simultaneously outputting both the video data (D 210  and D 340 ) (as video data D 352 ). More specifically, controller  352  can be formed by a digital video mixer, switcher, and the like. 
     Video output controller  352  in ENAV engine  300  is configured to output video data D 210  from DVD-Video playback engine  200  (full video mode), to output video data D 340  from ENAV engine  300  (full ENAV mode), or to mix and output both video data D 210  from DVD-Video playback engine  200  and video data D 340  from ENAV engine  300  (mixed frame mode) on the basis of a “video•audio output control signal” output from event generation•command/property processor  320  and/or a “layout control signal” output from ENAV interpreter  330 . 
     Also, video output controller  352  has a function of: (1) selecting video output D 210  of DVD-Video playback engine  200  as video data D 352  of DVD-Video player  100  when video data D 210  is output from only DVD-Video playback engine  200  but video data D 340  of ENAV engine  300  is not output; (2) selecting video output D 340  of ENAV engine  300  as video data D 352  of DVD-Video player  100  when video data D 340  is output from only ENAV engine  300  but video data D 210  of DVD-Video playback engine  200  is not output; and (3) switching and selecting video output D 210  of DVD-Video playback engine  200  and/or video output D 340  of ENAV engine  300  in accordance with an output method of user&#39;s choice from the user operation unit. 
     Furthermore, controller  352  can start/end video output at the designated timing, can continue to output video data for only the designated duration, or can output video data from the designated position (e.g., a chapter number or time information) on the basis of the layout control signal. 
       FIG. 32  shows an example wherein video data of the DVD-Video contents which include three chapters are output in accordance with the ENAV playback information of the ENAV contents on the basis of the layout control signal. In this example, a part of video data of chapter 1 is played back first, a part of video data of chapter 3 is played back, moving image data, still image data, and/or text data of the ENAV contents are/is played back, and video data of chapter 2, and moving image data and the like of the ENAV contents are mixed and played back finally. 
     Audio output controller  354  has a function of selecting audio data (audio part of D 210 ) from DVD-Video playback engine  200  or audio data (audio part of D 340 ) from ENAV engine  300 , and a function of changing the tone volume levels of these audio data (D 210  and D 340 ) and/or mixing these data, and outputting mixed audio data of both the audio data (D 210  and D 340 ) (as audio data D 354 ). More specifically, controller  354  can be formed by a digital audio mixer, switcher, and the like. 
     Audio output controller  354  in ENAV engine  300  is configured to output audio output D 210  from DVD-Video playback engine  200 , to output audio output D 340  from ENAV engine  300 , or to mix and output both audio data D 210  from DVD-Video playback engine  200  and audio data D 340  from ENAV engine  300  on the basis of a “video•audio output control signal” output from event generation•command/property processor  320  and/or a “layout control signal” output from ENAV interpreter  330 . For example, when audio output controller  354  mixes and outputs both audio data D 210  from DVD-Video playback engine  200  and audio data D 340  from ENAV engine  300 , it adjusts the levels of respective audio data (audio data part of D 210  and that of D 340 ), mixes these data, and outputs audio data D 354 . 
     Also, audio output controller  354  has a function of: (1) selecting audio output D 210  of DVD-Video playback engine  200  as audio data D 354  of DVD-Video player  100  when audio data D 210  is output from only DVD-Video playback engine  200  but audio data D 340  of ENAV engine  300  is not output; (2) selecting audio output D 340  of ENAV engine  300  as audio data D 354  of DVD-Video player  100  when audio data D 340  is output from only ENAV engine  300  but audio data D 210  of DVD-Video playback engine  200  is not output; and (3) switching and selecting audio output D 210  of DVD-Video playback engine  200  and/or audio output D 340  of ENAV engine  300  in accordance with an output method of user&#39;s choice from the user operation unit. 
     Furthermore, controller  354  can start/end audio output at the designated timing, can continue to output audio data for only the designated duration, or can output audio data from the designated position (e.g., a chapter number or time information) on the basis of the layout control signal. 
       FIG. 33  shows an example wherein audio data of the DVD-video contents which include one chapter is output in accordance with the ENAV playback information of the ENAV contents on the basis of the layout control signal. In this example, a part of audio data of chapter 1 is played back first, a part of audio data of chapter 1, and audio data of the ENAV contents are mixed and played back after a given silent period, and audio data of the ENAV contents is then played back. 
     Note that ENAV engine  300  in DVD-Video player  100  in  FIG. 1  comprises interface  400  for sending the ENAV playback information in ENAV contents  30  read from DVD video disc  1  to ENAV interpreter  330 , and interface  400 * for sending data bodies (audio data, still image data, text data, moving image data, and the like) in read ENAV contents  30  to element decoder  340 . These interfaces  400  and  400 * form an interface (first interface) independently of an interface connection unit in  FIG. 1 . 
     DVD-video player  100  in  FIG. 1  comprises interface  400 W for receiving ENAV contents  30 W from a communication line such as the Internet or the like, and sending ENAV playback information in received contents  30 W to ENAV interpreter  330 , and interface  400 W* for sending data bodies (audio data, still image data, text data, moving image data, and the like) in received ENAV contents  30 W to element decoder  340 . These interfaces  400 W and  400 W* form the interface connection unit (second interface) of  FIG. 1 . 
     In order words, the building components of ENAV engine  300  in  FIG. 1  can be summarized as follows. That is, ENAV engine  300  comprises 
     language interpreter (ENAV interpreter)  330  for parsing and interpreting the contents of playback control information (ENAV playback information) contained in ENAV contents  30  (or  30 W), 
     information processor (event generation•command/property processor)  320  for executing a command (ENAV command) contained in the playback control information (ENAV playback information) that has been parsed and interpreted by ENAV interpreter  330 , 
     element decoder  340  for generating video•audio data D 340  corresponding to other contents (audio data, still image data, text data, moving image data, and the like) contained in ENAV contents  30  (or  30 W), 
     output unit (video•audio output unit)  350  for mixing video•audio data D 340  generated by element decoder  340  with video•audio data D 210  played back by DVD-Video playback engine  200  and outputting the mixed data, or selecting one of video•audio data D 210  and video•audio data D 340  and outputting the selected data, on the basis of the execution result of the ENAV command in information processor  320 , and 
     user event controller  310  for generating a user event corresponding to user&#39;s operation  40  of the DVD-Video player. 
     Note that information processor  320  is configured to execute a process corresponding to the user event generated by user event controller  310  (e.g., ST 92  to ST 116  and the like in  FIG. 14  to be described later). Output unit  350  is configured•to mix video•audio data D 340  generated by element decoder  340  with video•audio data D 210  played back by DVD-Video playback engine  200  and output the mixed data, or to selectively output one of video•audio data D 210  and video•audio data D 340 , on the basis of the execution result of the process corresponding to the user event. 
       FIGS. 2A-2C  are views for explaining a display example upon outputting a playback video on the DVD-Video contents side and that on the ENAV contents side as a multi-frame output in the arrangement shown in  FIG. 1 . 
     Decoder unit  210  in DVD-Video playback engine  200  in  FIG. 1  has a mechanism of decoding and outputting moving image information, audio information, sub-picture information, and the like in DVD-Video contents  1  from DVD video disc  1  as in a decoder unit in the conventional DVD-Video player.  FIG. 2A  exemplifies a moving image and/or sub-picture part (D 210 ) in DVD-Video contents  10 . 
     Element decoder  340  in ENAV engine  300  has a function of decoding and outputting moving image information (including animation), still image information, audio information, and text information in ENAV contents  30  recorded on DVD video disc  1  in  FIG. 30  (or  FIG. 31 ) and/or ENAV contents (Web contents)  30 W acquired from the Internet or the like. FIG.  2 B exemplifies a plurality of moving image and/or still image parts  30 A to  30 C (D 340 ) contained in ENAV contents  30  (or  30 W). 
     When DVD-Video contents image  10  in  FIG. 2A  and ENAV contents images  30 A to  30 C in  FIG. 2B  are to be mixed and output, video output controller  352  in  FIG. 1  receives a layout control signal from ENAV interpreter  330 , and adjusts (reduces in this case) the window size of DVD-Video contents  10  on the basis of the received layout control signal. More specifically, pixels of DVD-Video contents  10  in  FIG. 2A  can be decimated to fall within the vertical and horizontal pixel sizes of a blank area (an area where none of ENAV contents images  30 A to  30 C are displayed) in  FIG. 2B . 
     When video output controller  352  executes an operation for fitting (video-mixing) contents  10  obtained after the window size of DVD-Video contents  10  has been adjusted (reduced) into the blank area in  FIG. 2B , multi-frame video output D 352  that mixes the DVD video contents playback image and ENAV contents playback images is obtained, as shown in  FIG. 2C . 
       FIGS. 3A-3C  are views for explaining a display example upon outputting a playback video on the DVD-Video contents side and that on the ENAV contents side on multi-windows (overlapping windows) in the arrangement shown in  FIG. 1 . 
     A method of outputting both video data D 210  from DVD-Video playback engine  200  and video data D 340  from ENAV engine  300  is not limited to the above method that adjusts the respective image sizes and outputs these video data onto split frame areas as a multi-frame output, as shown in  FIG. 2C , in accordance with the description of the ENAV playback information in ENAV contents  30  (or  30 W). That is, the sizes of images of DVD-Video contents  10  ( FIG. 3A ) and ENAV contents  30  ( FIG. 3B ) may be adjusted in accordance with the description of the ENAV playback information, and the size-adjusted contents images  10  and  30  may be output on overlapping windows (multi-windows), as shown in  FIG. 3C . Display of such overlapping windows (multi-windows) can be implemented by exploiting the state-of-the-art technique in a personal computer. 
       FIGS. 4A-4E  are views for explaining an example upon mixing a playback audio on the DVD-Video contents side and that on the ENAV contents side in the arrangement shown in  FIG. 1 . 
     Assume that audio output D 210  from DVD-Video playback engine  200  has an analog waveform shown in  FIG. 4A , and audio output D 340  has an analog waveform shown in  FIG. 4C . In this case, since the tone volume level of DVD-Video audio data D 210  is different from that of ENAV audio data D 340 , audio data with a smaller tone volume level can hardly be caught if these data are mixed intact. For this reason, audio output controller  354  in  FIG. 1  executes tone volume level adjustment, so that the average tone volume level of DVD-Video audio data D 210  becomes equivalent to that of ENAV audio data D 340  (level adjustment of digital data can be attained by shifting the bits of audio data; that of analog data can be attained using a known automatic volume adjustment circuit in an analog tape recorder or the like). 
     As a result of the tone volume level adjustment, audio output D 210  in  FIG. 4A  is adjusted, as shown in  FIG. 4B , and audio output D 340  in  FIG. 4C  is adjusted, as shown in  FIG. 4D . When the DVD-video playback audio data ( FIG. 4B ) and ENAV contents playback audio data ( FIG. 4D ) that have undergone the tone volume level adjustment are mixed, audio output D 354  with a waveform shown in  FIG. 4E  is obtained. 
     As the effect of the example of  FIG. 4 , if one (e.g., D 210 ) of audio data to be mixed is declamation or the like without music, the other audio data (D 340 ) can be used as background music (BGM). 
     Note that the tone volume level of DVD-Video playback audio data D 210  in  FIG. 4A  can be adjusted by multiplying predetermined attenuation coefficient ATT- 1  (=0 to 1), and that of ENAV contents playback audio data D 340  in  FIG. 4C  can be adjusted by multiplying predetermined attenuation coefficient ATT- 2  (=0 to 1). Attenuation coefficient ATT- 1  and/or attenuation coefficient ATT- 2  can be given as variables of a “tone volume change command” specified in the ENAV playback information. 
       FIG. 5  is a view for explaining an example of changes in DVD video playback output (DVD video menu) and ENAV playback output (ENAV menu) in correspondence with an internal command.  FIG. 6  is a flow chart for explaining an example of a processes of the DVD-Video playback engine and ENAV engine in association with menu call by a command.  FIG. 7  is a view for explaining a menu display example (full video mode) on the video contents side.  FIG. 8  is a view for explaining a menu display example (full ENAV mode) on the ENAV contents side.  FIG. 11  is a view for explaining a display example (mixed frame mode (mixed mode)) of a mixed menu of the video and ENAV contents. 
     Assume that execution of menu call is set as a post-command at the end of a given title (e.g., VTS# 1  in  FIG. 30  or  31 ) contained in DVD-Video contents  10 . In this case, DVD-Video playback engine  200  executes menu call at the end of playback of that title, and outputs a DVD event signal indicating that menu call will be executed (or menu call was executed) to ENAV engine  300 . At this time, upon receiving the DVD event signal sent from DVD-Video playback engine  200 , ENAV engine  300  in a wait state executes an ENAV engine operation in accordance with the ENAV playback information in ENAV contents  30 . 
     The aforementioned ENAV playback information describes ENAV contents (ENAV menu) to be executed upon receiving the DVD event signal that means menu call execution, and switching of a mode (full frame mode/full video mode, full ENAV mode, or mixed frame mode) at that time. 
     An example of an operation associated with menu call (by an internal command of the DVD-Video player) in DVD-Video player  100  in  FIG. 1  will be described in detail below with reference to  FIGS. 5 to 8 , and  FIG. 11 . A case will be exemplified below wherein menu call is executed by an internal command (pre-command, post-command, or the like) of player  100 . 
     On the DVD-Video playback engine  200  side, a given title is played back (step ST 10 , NO in step ST 12 ; corresponding to “DVD-Video playback” in the uppermost column of  FIG. 5 ). Upon completion of title playback (YES in step ST 12 ), menu call is executed by a post-command (internal command of player  100 ) (step ST 14 ; corresponding to “downward arrow” of the uppermost column of  FIG. 5 ). Then, DVD-Video playback controller  220  sends a DVD event signal indicating menu call to event generation•command/property processor  320  (step ST 16 ), and video output controller  352  sends menu video data D 352  to a TV monitor (not shown). Then, a menu shown in, e.g.,  FIG. 7  is displayed on the display screen of the TV monitor (step ST 18 ; corresponding to “DVD-Video menu display” in the uppermost column of  FIG. 5 ). 
     On the ENAV engine  300  side, after ENAV interpreter  330  fetches ENAV contents  30  (step ST 20 ), and is ready to exchange command/event/property with event generation•command/property processor  320 , it waits for some event (step ST 22 , NO in step ST 24 ; corresponding to “event wait” in the second column of  FIG. 5 ). If the “DVD event signal indicating menu call” is output in step ST 16 , and event generation•command/property processor  320  receives this DVD event signal (YES in step ST 24 ; corresponding to “downward arrow” of the second column of  FIG. 5 ), ENAV interpreter  330  checks if fetched ENAV contents  30  include ENAV menu contents. 
     If ENAV contents  30  do no include any ENAV menu contents (NO in step ST 26 ), event generation•command/property processor  320  outputs a video•audio output control signal as a “full video mode that means output of video and audio data of the DVD-Video playback engine” (step ST 28 ). Then, video•audio output unit  350  outputs video•audio data of DVD-Video playback engine  200  as a video•audio output (D 352 , D 354 ). ENAV engine  300  returns to an event wait state (step ST 30 ). 
     On the other hand, if ENAV contents  30  include ENAV menu contents (YES in step ST 26 ), event generation•command/property processor  320  executes an ENAV menu process in accordance with an ENAV command from ENAV interpreter  330  (step ST 32 ). At this time, event generation•command/property processor  320  outputs a video•audio output control signal as a “full ENAV mode that means output of video and audio data of the ENAV engine” (step ST 34 ). Then, video•audio output unit  350  outputs video (ENAV menu)•audio data of ENAV engine  300  as a video•audio output (D 352 , D 354 ). 
     The ENAV menu in ENAV contents  30  is defined by moving image data (including animation), still image data, audio data, and text data, as shown in, e.g.,  FIG. 8 . These data are sent to and decoded by the corresponding decoder in element decoder  340 . The decoded data are sent as video data D 352  to a monitor TV (not shown) and are displayed as the ENAV menu on the display screen of the monitor TV (step ST 36 ; corresponding to “ENAV menu display” in the second column of  FIG. 5 ). ENAV engine  300  then returns to a wait state (step ST 30 ). 
     When DVD-Video playback engine  200  outputs DVD-Video menu data D 210 , and ENAV engine  300  outputs ENAV menu data D 340 , ENAV engine  300  can select one of the following two processes in accordance with device setups, user&#39;s operation, ENAV playback information, and the like (see lower two columns in  FIG. 5 ) upon switching a video output in accordance with the video•audio output control signal from event generation•command/property processor  320  (corresponding to “downward arrow” in the third column of  FIG. 5 ): 
     (1) ENAV menu display in full ENAV mode from DVD-Video playback in full video mode; and 
     (2) DVD-Video menu display in full video mode from DVD-Video playback in full video mode. 
     Also, when DVD-Video playback engine  200  outputs DVD-Video menu data D 210 , and ENAV engine  300  outputs ENAV menu data D 340 , a menu defined by both DVD-Video contents (moving image or the like)  10  and ENAV contents (moving image or the like)  30  may be displayed in the mixed frame mode in the processes in steps ST 32  to ST 36 .  FIG. 11  shows a display example in this case. 
     Although the DVD-Video menu ( FIG. 7 ) can display only one moving image, the ENAV menu ( FIG. 8 ) can use moving images (including animation) for respective menu windows and select buttons. Furthermore, using video output D 210  of DVD-Video playback engine  200  and video output D 340  of ENAV engine  300 , the ENAV menu ( FIG. 11 ) which contains not only the moving image of DVD-Video contents  10  but also those of the ENAV contents can be displayed. 
     The process in  FIG. 6  can be summarized as follows. That is, in a system for playing back recorded contents that include DVD-Video contents  10  and ENAV contents  30  from a DVD video disc ( 1  in  FIG. 30  or  31 ) having a volume space complying with the DVD-Video standard, DVD-Video contents  10  of the recorded contents played back from DVD video disc  1  are acquired (step ST 10 ). Then, ENAV contents  30  of the recorded contents played back from DVD video disc  1  are acquired (step ST 20 ), and the contents of acquired ENAV contents  30  are executed in accordance with a predetermined event (step ST 16 ) corresponding to the contents of acquired DVD-Video contents  10  (step ST 32 ). 
     Modes (a video mode that uses the DVD-Video contents and/or an interactive mode using the ENAV contents) and display modes used in the system arrangement of  FIG. 1  will be explained below. The display mode in the video mode includes only the full video mode ( FIG. 7  and the like), but the display mode in the interactive mode includes three different modes, i.e., the full video mode ( FIG. 7  and the like), full ENAV mode ( FIG. 8  and the like), and mixed frame mode ( FIG. 11  and the like). For example, these display modes can be selectively used as follows. 
     That is, when DVD-Video playback alone is purely done in the video mode, the full video mode is used. 
     On the other hand, in the interactive mode, when only DVD-Video is displayed (but the ENAV engine is running as its background), the full video mode is used. Also, when the ENAV contents are displayed (but DVD-Video playback is done as its background), full ENAV mode (full navigation mode) is used. Furthermore, when DVD-Video playback is made while the ENAV engine is running, and when a DVD-Video playback image and ENAV contents playback image are displayed together, the mixed frame mode (mixed mode) is used. 
       FIG. 9  is a view for explaining an example of changes in DVD video playback output (DVD video chapter playback) and ENAV playback output (ENAV contents playback) in correspondence with an internal command.  FIG. 10  is a flow chart for explaining an example of the processes of the DVD-Video playback engine and ENAV engine in association with chapter playback.  FIG. 12  is a view for explaining a display example (mixed frame mode) of a mixed video of the video and ENAV contents. 
     Assume that execution of title jump is set as a post-command at the end of chapter A (e.g., given part of title PTT contained in one of VTS# 1  to VTS#n in  FIG. 30  or  31  is assumed to be this chapter A) of DVD-Video contents  10 . In this case, DVD-Video playback engine  200  executes title jump to another chapter X upon completion of playback of chapter A, and outputs a DVD event signal indicating that title jump will be executed (or title jump was executed) to ENAV engine  300 . Upon receiving the DVD event signal sent from DVD-Video playback engine  200 , ENAV engine  300  in a wait state executes an ENAV engine operation in accordance with the ENAV playback information in ENAV contents  30 . 
     The ENAV playback information describes ENAV contents to be executed upon receiving the DVD event signal that means title jump execution, and switching of a mode (full frame mode/full video mode, full ENAV mode, or mixed frame mode) at that time. 
     An example of the operation associated with title jump/chapter switching (by an internal command of the DVD-Video player) in DVD-Video player  100  in  FIG. 1  will be described in detail below with reference to  FIGS. 9 to 12 . A case will be exemplified below wherein title jump is executed by an internal command (pre-command, post-command, or the like) of player  100 . 
     On the DVD-Video playback engine  200  side, chapter A in a given title is played back (step ST 40 , NO in step ST 42 ; corresponding to “DVD-Video playback (chapter A)” in the uppermost column of  FIG. 9 ). Upon completion of playback of chapter A of that title (YES in step ST 42 ), title jump is executed by a post-command (internal command of player  100 ) (step ST 44 ; corresponding to “downward arrow” of the uppermost column of  FIG. 9 ). Then, DVD-Video playback controller  220  sends a DVD event signal indicating title jump to event generation•command/property processor  320  (step ST 46 ), and video output controller  352  sends video data D 352  of chapter X of a jump destination title to a TV monitor (not shown). Then, a video of that chapter X is displayed on the display screen of the TV monitor (step ST 48 ; corresponding to “DVD-Video playback (chapter X)” in the uppermost column of  FIG. 9 ). 
     On the ENAV engine  300  side, after ENAV interpreter  330  fetches ENAV contents  30  (step ST 50 ), and is ready to exchange command/event/property with event generation•command/property processor  320 , it waits for some event (step ST 52 , NO in step ST 54 ; corresponding to “event wait” in the second column of  FIG. 9 ). If the “DVD event signal indicating title jump” is output in step ST 46 , and event generation•command/property processor  320  receives this DVD event signal (YES in step ST 54 ; corresponding to “downward arrow” of the second column of  FIG. 9 ), ENAV interpreter  330  checks if fetched ENAV contents  30  include ENAV menu contents. 
     If ENAV contents  30  do no include any contents corresponding to “title jump” (NO in step ST 56 ), event generation•command/property processor  320  outputs a video•audio output control signal as a “full video mode that means output of video and audio data of the DVD-Video playback engine” (step ST 58 ). Then, video•audio output unit  350  outputs video•audio data of chapter X from DVD-Video playback engine  200  as a video•audio output (D 352 , D 354 ) ENAV engine  300  returns to an event wait state (step ST 60 ). 
     On the other hand, if ENAV contents  30  include contents corresponding to “title jump” (YES in step ST 56 ), event generation•command/property processor  320  executes a process of the contents corresponding to “title jump” (e.g., a process for displaying, if chapter X is a given scene of drama, scenario text of that scene) in accordance with an ENAV command from ENAV interpreter  330  (step ST 62 ). At this time, event generation•command/property processor  320  outputs a video•audio output control signal as a “full ENAV mode that means output of video and audio data of the ENAV engine” (step ST 64 ). Then, video•audio output unit  350  outputs video (scenario text or the like in the above example)•audio (e.g., the audible comment of a director or scenario writer who produced that drama) data of ENAV engine  300  as a video•audio output (D 352 , D 354 ). 
     Respective data in ENAV contents  30  include video information (text, still image, moving image, or animation)  30 A, storyboard (still image)  30 B, scenario (text)  30 C, and other data (audio data and the like), as shown in, e.g.,  FIG. 12 . These data are sent to and decoded by the corresponding decoders in element decoder  340 . The decoded data are sent as video data D 352  to a monitor TV (not shown) and are displayed as ENAV contents  30 A to  30 C on the display screen of the monitor TV (step ST 66 ; corresponding to “ENAV contents playback” in the second column of  FIG. 9 ). ENAV engine  300  then returns to a wait state (step ST 60 ). 
     When DVD-Video playback engine  200  outputs DVD-Video chapter X playback data D 210 , and ENAV engine  300  outputs ENAV contents playback data D 340 , ENAV engine  300  can select one of the following two processes in accordance with device setups, user&#39;s operation, ENAV playback information, and the like (see lower two columns in  FIG. 9 ) upon switching a video output in accordance with the video•audio output control signal from event generation•command/property processor  320  (corresponding to “downward arrow” in the third column of  FIG. 9 ): 
     (1) ENAV contents playback in full ENAV mode from DVD-Video (chapter A) playback in full video mode; and 
     (2) DVD-Video (chapter X) playback in full video mode from DVD-Video (chapter A) playback in full video mode. 
     Also, when DVD-Video playback engine  200  outputs DVD-Video (chapter X) playback data D 210 , and ENAV engine  300  outputs ENAV contents playback data D 340  (corresponding to chapter X), a display frame defined by both DVD-Video contents (moving image or the like)  10  and ENAV contents (moving image or the like)  30  may be displayed in the mixed frame mode in the processes in steps ST 62  to ST 66 .  FIG. 12  shows a display example in this case. In  FIG. 12 , a DVD-Video playback image (one scene of a movie or drama, or the like) is displayed at a position corresponding to DVD-Video contents  10  in  FIG. 2C , and movie information  30 A, storyboard  30 B, and scenario  30 C are displayed as various ENAV contents at positions corresponding to ENAV contents  30 A to  30 C in  FIG. 2C . 
     Upon display in the mixed frame mode in  FIG. 12  (mixed mode), a scenario, storyboard, information of a movie, information of the casts, and the like are switched and displayed in synchronism (or connection or combination) with a change in contents (change in scene) of DVD-Video contents  10 , while playing back a scene of a movie or drama as DVD-Video contents  10 . These pieces of information (information of the scenario and the like to be displayed in synchronism, connection, or combination with the playback video of DVD-Video) can use not only ENAV contents  30  recorded on DVD video disc  1  but also ENAV contents  30 W externally acquired using the Internet or the like. 
     That is, the ENAV contents, which can variously change in combination, connection, or synchronism with the contents playback of DVD video disc  1 , are not limited to ENAV contents  30  played back from that disc  1 , but can use ENAV contents (Web contents)  30 W acquired from an external system (Internet or the like). Furthermore, the playback method of DVD-Video contents  10  can be diversified by using ENAV contents  30  from disc  1  and/or ENAV contents  30 W acquired from the external system together as needed. 
     If the menu process in  FIG. 6  is combined with the title jump process in  FIG. 10 , a DVD-video/ENAV mixed menu shown in  FIG. 11  can be displayed on a portion (e.g., a display area of video contents  10 A) of the display area in  FIG. 12 , in step ST 64  in  FIG. 10 . 
     ENAV contents  30  corresponding to title jump that has been explained with reference to  FIG. 10  can be formed of moving image (including animation) data, still image data, audio data, and text data. These data are sent to and decoded by the corresponding decoders of element decoder  340 . The decoded contents are then displayed as ENAV contents on the display screen of the TV monitor (not shown). 
     At this time, if the ENAV playback information in ENAV contents  30  contains a description which instructs to form a frame using, e.g., DVD-Video contents  10  and ENAV contents  30 , event generation•command/property processor  320  outputs a video•audio output control signal as the mixed frame mode to video•audio output unit  350 . Then, video and audio output controllers  352  and  354  output video data D 352  and audio data D 354  obtained by mixing video•audio data D 210  from DVD-Video playback engine  200 , and video•audio data D 340  from ENAV engine  300 . In this case, video output controller  352  adjusts the sizes/positions of frames of video data D 210  and D 340  and outputs these data as a multi-frame output ( FIG. 2C  or  FIG. 12 ) or outputs them on multi-windows ( FIG. 3C ) in accordance with the ENAV playback information in ENAV contents  30 . Also, audio output controller  354  appropriately mixes and outputs audio data D 210  and D 340  after it adjusts their levels. 
     The process in  FIG. 10  can be summarized as follows. That is, in a system for playing back recorded contents that include DVD-Video contents  10  and ENAV contents  30  from a DVD video disc ( 1  in  FIG. 30  or  31 ) having a volume space complying with the DVD-Video standard, DVD-Video contents  10  of the recorded contents played back from DVD video disc  1  are acquired (step ST 40 ). Then, ENAV contents  30  of the recorded contents played back from DVD video disc  1  are acquired (step ST 50 ), and the contents of acquired ENAV contents  30  are executed in accordance with a predetermined event (step ST 46 ) corresponding to the contents of acquired DVD-Video contents  10  (step ST 62 ). 
       FIG. 13  is a view for explaining an example of changes in DVD video playback output (DVD video menu) and ENAV playback output (ENAV menu) in correspondence with user&#39;s operation (user event).  FIG. 14  is a flow chart for explaining an example of the processes of the DVD-Video playback engine and ENAV engine in association with menu call by the user. 
     The operation associated with menu call (issued in response to a user&#39;s request) in DVD-Video player  100  in  FIG. 1  will be explained below with reference to  FIGS. 13 and 14 . In this embodiment, a processing example executed when the user of DVD-Video player  100  in  FIG. 1  presses a menu button on a remote controller (not shown) or a front panel (not shown) of DVD-Video player  100  to display a menu, and presses the menu button again to execute resume playback (when the menu button has been pressed during playback of DVD video disc  1 , video playback is paused, and playback automatically restarts from the playback paused position upon completion of a menu operation) will be explained. 
     On the DVD-Video playback engine  200  side, a title of a given movie is played back (step ST 70 ; NO in step ST 72 ; corresponding to “first DVD-Video playback” in the uppermost and third columns in  FIG. 13 ). When the user issues menu call during title playback, that user event signal (A) is sent to DVD-Video playback controller  220  (YES in step ST 72 ; corresponding to “first downward arrow” of the uppermost column in  FIG. 13 ). Then, DVD-video playback controller  220  temporarily stores information of the playback time (or address) of the title playback position paused by this menu call, and then executes a process corresponding to menu call (step ST 74 ). As a result, a DVD-Video menu (not shown) that contains an audio select button and caption language select button is displayed on the screen of a monitor TV (not shown) (step ST 76 ; corresponding to “DVD-Video menu playback” in the uppermost column of  FIG. 13 ). This menu display continues (NO in step ST 78 ) until the user makes the next operation (selection of audio/caption, selection of a title play button, or the like). 
     Assume that the user has selected, e.g., an English audio and Japanese caption from the displayed menu, and pressed the menu button on the remote controller (or the title play button in the displayed menu). Then, user event signal (A) corresponding to this user&#39;s operation is sent to DVD-Video playback controller  220  (YES in step ST 78 ; corresponding to “second downward arrow” of the uppermost column of  FIG. 13 ). DVD-Video playback controller  220  executes a resume process on the basis of the temporarily stored playback time information (or time information) in response to this user event (step ST 80 ). As a result, playback of DVD video disc  1  is automatically restarted from a scene immediately before menu call of the title that has been paused so far (step ST 82 ; corresponding to “second DVD-Video playback” in the uppermost and third columns of  FIG. 13 ). 
     On the ENAV engine  300  side, after ENAV interpreter  330  fetches ENAV contents  30 , and is ready to exchange command/event/property with event generation•command/property processor  320 , it waits for some event (step ST 92 , NO in step ST 94 ; corresponding to “first event wait” in the second column of  FIG. 13 ). 
     If the user has pressed the menu button on the nearby remote controller (not shown) (YES in step ST 94 ; corresponding to “first downward arrow” of the second column of  FIG. 13 ), user event controller  310  outputs user event signals (A) and (C) of menu call (step ST 96 ). DVD-Video playback controller  220  receives user event signal (A) of menu call (YES in step ST 72 ), and event generation•command/property processor  320  receives user event signal (C) of menu call. 
     If ENAV contents  30  (and/or  30 W) that have been fetched before step ST 92  do not contain any ENAV menu (NO in step ST 98 ), event generation•command/property processor  320  outputs a video•audio output control signal as a “full video mode that means output of video and audio data of the DVD-Video playback engine” (step ST 100 ). Then, video•audio output unit  350  outputs video•audio data of DVD-Video playback engine  200  as a video•audio output (D 352 , D 354 ) ENAV engine  300  returns to an event wait state (step ST 102 ). 
     On the other hand, if ENAV contents  30  (and/or  30 W) include ENAV menu contents (YES in step ST 98 ), event generation•command/property processor  320  executes a process of the ENAV menu in accordance with an ENAV command from ENAV interpreter  330  (step ST 104 ). At this time, event generation•command/property processor  320  outputs a video•audio output control signal as a “full ENAV mode that means output of video and audio data of the ENAV engine” (step ST 106 ). Then, video•audio output unit  350  outputs video (ENAV menu)•audio data of ENAV engine  300  as a video•audio output (D 352 , D 354 ). 
     The ENAV menu in ENAV contents  30  (and/or  30 W) is defined by moving image data (including animation), still image data, audio data, and text data, as shown in, e.g.,  FIG. 8 . These data are sent to and decoded by the corresponding decoder in element decoder  340 . The decoded data are sent as video data D 352  to a monitor TV (not shown) and are displayed as a menu on the display screen of the monitor TV (step ST 108 ; corresponding to “ENAV menu playback” in the second and third columns of  FIG. 13 ). ENAV engine  300  then returns to a wait state (step ST 102 ). In this state, ENAV engine  300  waits for the next event (user&#39;s remote-controller operation or the like in this case) (NO in step ST 110 ; corresponding to “second event wait” in the second column of  FIG. 13 ). 
     If the user has pressed the menu button of the nearby remote controller (not shown) (YES in step ST 110 ; corresponding to “second downward arrow” of the second column of  FIG. 13 ), user event controller  310  outputs user event signals (A) and (C) of resume (step ST 112 ). DVD-Video playback controller  220  receives user event signal (A) of resume (YES in step ST 78 ), and event generation•command/property processor  320  receives user event signal (C) of resume. 
     Then, event generation•command/property processor  320  outputs a video•audio output control signal as a “full video mode that means output of video and audio data of the DVD-Video playback engine” (step ST 114 ). Then, video•audio output unit  350  outputs video•audio data of DVD-Video playback engine  200  as a video•audio output (D 352 , D 354 ) (step ST 82 ; this process corresponds to “second DVD-Video playback” in the third column of  FIG. 13 ). 
     The process in  FIG. 14  can be summarized as follows. That is, when the user has pressed the menu button on the user operation unit (a remote controller or front panel of DVD-Video player  100 ; not shown) (YES in step ST 94 ) during title playback of DVD-Video contents  10  (step ST 70 ), user event controller  310  in ENAV engine  300  receives this menu button operation signal (YES in step ST 72 ). User event controller  310  outputs this signal as user event signal (A) to DVD-Video playback controller  220  and as user event signal (C) to event generation•command/property processor  320  (step ST 96 ). 
     DVD-Video playback engine  200  receives user event signal (A) that means menu call, and plays back a DVD-Video menu (step ST 76 ). 
     Upon receiving user event signal (C) that means menu call (step ST 96 ), ENAV engine  300  in the wait state (step ST 92 ) executes an operation in accordance with the playback control information (markups, scripts) in ENAV contents  30  (and/or  30 W). This playback control information describes, e.g., “ENAV contents (ENAV menu)” to be executed upon receiving user event signal (C) that means execution of menu call, and “switching of modes (full frame mode/full ENAV mode or mixed frame mode)” at that time. 
     The ENAV menu in ENAV contents  30  (and/or  30 W) is defined by moving image data (including animation), still image data, audio data, and text data. These data are sent to and decoded by the corresponding decoder in element decoder  340 , and are displayed as an ENAV menu (step ST 108 ). At this time, event generation•command/property processor  320  outputs a video•audio control signal as a full ENAV mode that means output of video•audio data of the ENAV engine. In response to this signal, video•audio output unit  350  outputs video•audio data (D 340 ) of ENAV engine  300  as a video•audio output (D 352 , D 354 ). If ENAV contents  30  (and/or  30 W) does not include any ENAV menu contents (NO in step ST 98 ), event generation•command/property processor  320  outputs a video•audio output control signal as a full video mode that means output of video and audio data of the DVD-Video playback engine. Then, video•audio output unit  350  outputs video•audio data (D 210 ) of DVD-Video playback engine  200  as a video•audio output (D 352 , D 354 ). ENAV engine  300  returns to an event wait state again (step ST 102 ). 
     If the user has pressed the menu button of the user operation unit (a remote controller or front panel of DVD-Video player  100 ; not shown) (YES in step ST 110 ) during menu playback (step ST 76 , ST 108 ; the DVD-Video menu is displayed in the full video mode, or the ENAV menu is displayed in the full ENAV mode), user event controller  310  of ENAV engine  300  receives this signal. User event controller  310  outputs this signal as user event signal (A) to DVD-Video playback controller  220 , and as user event signal (C) to event generation•command/property processor  320  (step ST 112 ). 
     As a result, DVD-Video playback engine  200  receives user event signal (A) that means resume, and resumes playback of the DVD-Video title that was played back previously (steps ST 80  to ST 82 ). 
     Upon receiving user event signal (C) that means resume, in ENAV engine  300  which is playing back the ENAV menu, event generation•command/property processor  320  outputs a video•audio output control signal as a full video mode in accordance with the playback control information (markups, scripts) in ENAV contents  30  (and/or  30 W), and video•audio output unit  350  outputs video•audio data (D 210 ) of DVD-Video playback engine  200  as a video•audio output (step ST 114 ) At this time, ENAV engine  300  itself returns to a wait state (step ST 116 ). That is, DVD-Video player  100  which has displayed the ENAV menu resumes playback of the DVD-Video title (resume). 
       FIG. 15  is a view for explaining an example of changes in DVD video playback output (DVD video menu or playback pause) and ENAV playback output (ENAV menu) in correspondence with user&#39;s operation (user event).  FIGS. 16 and 17  are flow charts for explaining an example of the processes of the DVD-Video playback engine and ENAV engine in association with menu call or playback pause by the user. 
     Another example of the operation associated with menu call (issued in response to a user&#39;s request) in DVD-Video player  100  in  FIG. 1  will be explained below with reference to  FIGS. 15 to 17 . In this embodiment, a processing example executed when the user of DVD-Video player  100  presses a menu button on a remote controller (not shown) or a front panel (not shown) of DVD-Video player  100  to display a menu, and presses the menu button again to restart playback (when the menu button has been pressed during playback of DVD video disc  1 , video playback is paused, and playback automatically restarts from the playback paused position upon completion of a menu operation) will be explained. 
     On the DVD-Video playback engine  200  side, a title of a given movie is played back (step ST 120 , NO in step ST 122  in  FIG. 16 ; corresponding to “first DVD-Video playback” in the uppermost and third columns in  FIG. 15 ). When the user has made menu call operation during title playback, a DVD control signal corresponding to that operation is sent from ENAV engine  300  to DVD-Video playback controller  220  (YES in step ST 122 ; corresponding to “first downward arrow” of the uppermost column in  FIG. 15 ). Then, DVD-video playback controller  220  pauses title playback in response to this DVD control signal that means menu call or pause ON, and then executes a process corresponding to menu call or pause ON (step ST 124 ). As a result, a DVD-Video menu (not shown) is displayed on the screen of a monitor TV (not shown) or a still image at the moment of pausing playback is displayed on the screen (step ST 126  in  FIG. 17 ; corresponding to “DVD-Video menu playback &lt;pause or menu&gt;” in the uppermost column of  FIG. 15 ). This menu display or still playback continues (NO in step ST 128 ) until the user makes the next operation (menu button operation, pause button operation, or the like). 
     If the user has pressed the menu button on the remote controller (not shown), a DVD control signal corresponding to this user operation is sent from ENAV engine  300  to DVD-Video playback controller  220  (YES in step ST 128 ; corresponding to “second downward arrow” of the uppermost column of  FIG. 15 ). Then, DVD-Video playback controller  220  cancels the paused state (paused playback) or executes the aforementioned resume process ( FIG. 14 ) (step ST 130 ) on the basis of the DVD control signal (which means resume if menu display is executed in step ST 124  or means pause OFF if pause ON is executed in step ST 124 ) corresponding to this user event. As a result, playback of DVD video disc  1  is automatically restarted from a scene corresponding to the paused playback position (step ST 132 ; corresponding to “second DVD-Video playback” in the uppermost and third columns of  FIG. 15 ). 
     On the ENAV engine  300  side, after ENAV interpreter  330  fetches ENAV contents  30 , and is ready to exchange command/event/property with event generation•command/property processor  320 , it waits for some event (step ST 142 , NO in step ST 144  in  FIG. 16 ; corresponding to “first event wait” in the second column of  FIG. 15 ). 
     If the user has pressed the menu button on the nearby remote controller (not shown) (YES in step ST 144 ; corresponding to “first downward arrow” of the second column of  FIG. 15 ), ENAV interpreter  330  checks if the ENAV playback information in ENAV contents  30  (and/or  30 W) contains a script corresponding to menu call (step ST 146 ). If the ENAV playback information does not contain any script corresponding to menu call (NO in step ST 146 ), ENAV interpreter  330  sends a message indicating this to event generation•command/property processor  320 . In response to this message, event generation•command/property processor  320  also sends that message to user event controller  310 . Then, user event controller  310  outputs user event signal (B) that blocks (deters) the user event at that time (when the ENAV playback information does not contain any script corresponding to menu call) (signal “X” output from user vent controller  310  in  FIG. 1 ; step ST 148 ), and returns to an event wait state. 
     On the other hand, if the ENAV playback information in ENAV contents  30  (and/or  30 W) contains a script corresponding to menu call (YES in step ST 146 ), event generation•command/property processor  320  converts an ENAV command (menu call corresponding command in the ENAV playback information) received from ENAV interpreter  330  into a DVD control signal that instructs shift from menu call to pause ON/menu display (step ST 150 ). The DVD control signal for “pause ON/menu” is output from event generation•command/property processor  320  to DVD-Video playback controller  220  (step ST 152 ). 
     If ENAV contents  30  (and/or  30 W) that have been fetched before step ST 142  do not contain any ENAV menu (NO in step ST 154 ), event generation•command/property processor  320  outputs a video•audio output control signal as a “full video mode that means output of video and audio data of the DVD-Video playback engine” (step ST 156 ). Then, video•audio output unit  350  outputs video•audio data of DVD-Video playback engine  200  as a video•audio output (D 352 , D 354 ). ENAV engine  300  returns to an event wait state (step ST 158  in  FIG. 17 ). 
     On the other hand, if ENAV contents  30  (and/or  30 W) include ENAV menu contents (YES in step ST 154  in  FIG. 16 ), event generation•command/property processor  320  executes a process of the ENAV menu in accordance with an ENAV command from ENAV interpreter  330  (step ST 160 ). At this time, event generation•command/property processor  320  outputs a video•audio output control signal as a “full ENAV mode that means output of video and audio data of the ENAV engine” (step ST 162 ). Then, video•audio output unit  350  outputs video (ENAV menu)•audio data of ENAV engine  300  as a video•audio output (D 352 , D 354 ). 
     The ENAV menu in ENAV contents  30  (and/or  30 W) is defined by moving image data (including animation), still image data, audio data, and text data, as described above. These data are sent to and decoded by the corresponding decoder in element decoder  340 . The decoded data are sent as video data D 352  to a monitor TV (not shown) and are displayed as a ENAV menu on the display screen of the monitor TV (step ST 164 ; corresponding to “ENAV menu playback” in the second and third columns of  FIG. 15 ). ENAV engine  300  then returns to a wait state (step ST 158 ). In this state, ENAV engine  300  waits for the next event (user&#39;s remote-controller operation or the like in this case) (NO in step ST 166 ; corresponding to “second event wait” in the second column of  FIG. 15 ). 
     If the user has pressed the menu button of the nearby remote controller (not shown) again (YES in step ST 166 ; corresponding to “second downward arrow” of the second column of  FIG. 15 ), ENAV interpreter  330  checks if the ENAV playback information in ENAV contents  30  (and/or  30 W) contains a script corresponding to resume (step ST 168 ). If the ENAV playback information does not contain any script corresponding to resume (NO in step ST 168 ), ENAV interpreter  330  sends a message indicating this to event generation•command/property processor  320 . In response to this message, event generation•command/property processor  320  also sends that message to user event controller  310 . Then, user event controller  310  outputs user event signal (B) that blocks (deters) the user event at that time (when the ENAV playback information does not contain any script corresponding to resume) (signal “X” output from user vent controller  310  in  FIG. 1 ; step ST  170 ), and returns to an event wait state. 
     On the other hand, if the ENAV playback information in ENAV contents  30  (and/or  30 W) contains a script corresponding to menu call (YES in step ST 168 ), event generation•command/property processor  320  converts an ENAV command (resume corresponding command in the ENAV playback information) received from ENAV interpreter  330  into a DVD control signal that instructs shift from the menu call state to pause OFF/resume playback (step ST 172 ). The DVD control signal for “pause OFF/resume playback” is output from event generation•command/property processor  320  to DVD-Video playback controller  220  (step ST 174 ). 
     At this time, event generation•command/property processor  320  outputs a video•audio output control signal as a “full video mode that means output of video and audio data of the DVD-Video playback engine” (step ST 176 ). Then, video•audio output unit  350  outputs video•audio data of DVD-Video playback engine  200  as a video•audio output (D 352 , D 354 ). ENAV engine  300  returns to an event wait state (step ST 178 ). 
     The process in  FIGS. 16 and 17  can be summarized as follows. That is, when the user has pressed the menu button on the user operation unit (a remote controller or front panel of DVD-Video player  100 ; not shown) (YES in step ST 144 ) during title playback of DVD-Video contents  10  (step ST 120 ), user event controller  310  in ENAV engine  300  receives this signal. At this time, when user&#39;s operation  40  which is not expected as any user event is executed at the user operation unit (NO in step S 146 ), event generation•command/property processor  320  outputs a user event control signal (user event signal (B)) that “blocks a user event corresponding to user&#39;s operation at that time” (step ST 148 ). In this manner, user event controller  310  can inhibit “a specific event from being transmitted according to a script described in the ENAV contents”. 
     That is, since the process in step S 148  in  FIG. 16  or step ST 170  in  FIG. 17  is provided as needed, even when the description of a given script in the ENAV playback information in ENAV contents  30  (or  30 W) is grammatically correct but it includes contents (command, parameter, and the like) that “currently running” DVD-Video playback engine  200  cannot cope with”, an event corresponding to the description of that script can be clocked (deterred). 
     The script can describe, e.g., ENAV contents (ENAV menu) to be executed upon receiving user event signal (C) that means execution of menu call, switching of modes (full frame mode/full ENAV mode or mixed frame mode)” at that time, and control for outputting a “pause ON” (or “menu”) command as a DVD control signal to DVD-Video playback controller  220  of DVD-Video playback engine  200 . 
     The ENAV menu in ENAV contents  30  (and/or  30 W) is defined by moving image data (including animation), still image data, audio data, and text data, as described above. These data are sent to and decoded by the corresponding decoder in element decoder  340 , and are displayed as an ENAV menu. At this time, event generation•command/property processor  320  outputs a video•audio control signal as a full ENAV mode that means output of video•audio data of the ENAV engine, and video•audio output unit  350  outputs video•audio data (D 340 ) of ENAV engine  300  as a video•audio output (D 352 , D 354 ) (step ST 162 ). If ENAV contents  30  (and/or  30 W) does not include any ENAV menu contents (NO in step ST 154 ), a video•audio output control signal is output as a full video mode that means output of video and audio data of DVD-Video playback engine  200 , and video•audio data (D 210 ) of DVD-Video playback engine  200  is output as a video•audio output (D 352 , D 354 ) (step ST 156 ). ENAV engine  300  returns to an event wait state again (step ST 158 ). 
     On the other hand, upon receiving the “pause ON” (or “menu”) command as the DVD control signal (YES in step ST 122 ), DVD-Video playback engine  200  pauses playback (step ST 120 ) of DVD-Video contents  10  (step ST 124 ). (If the “menu” command is received in step ST 122 , a DVD-Video menu is displayed in step S 124 .) 
     If the user has pressed the menu button of the user operation unit (a remote controller or front panel of DVD-Video player  100 ; not shown) again (YES in step ST 166 ) during menu playback (step ST 126 , ST 164 ; the DVD-Video menu is displayed in the full video mode, or the ENAV menu is displayed in the full ENAV mode), user event controller  310  of ENAV engine  300  receives this signal. Then, user event controller  310  outputs this signal as user event signal (C) to event generation•command/property processor  320 . 
     Note that the script in ENAV contents  30  (and/or  30 W) describes, e.g., “control for making ENAV engine  300  return to a wait state upon receiving user event signal (C) that means resume”, switching of modes (full frame mode/full ENAV mode or mixed frame mode) at that time, and control for outputting a “pause OFF” command (“resume” command when the “menu” command is output) as a DVD control signal to DVD-Video playback controller  220  of DVD-Video playback engine  200 . 
     That is, upon receiving user event signal (C) that means resume, ENAV engine  300  can stop execution of menu display, and return to a wait state (step ST 178 ), while DVD-Video playback engine  200  can resume title playback (step ST 132 ). Since event generation•command/property processor  320  outputs a video•audio output control signal that means a full video mode, video•audio data (D 210 ) of DVD-Video playback engine  200  is output as a video•audio output (D 352 , D 354 ). 
       FIGS. 18A-18C  are views for explaining a case wherein ENAV content  1  is played back before playback of chapter 1, ENAV content  2  is played back in synchronism with playback of chapters 1 and 2, and ENAV content  3  is played back in synchronism with playback of chapters 3 and 4, when the DVD-Video playback engine successively plays back chapters 1 to 4. An example of synchronization (or connection or combination) between playback of ENAV contents  30  (or  30 W) and playback of the video contents (chapters) will be explained below with reference to  FIGS. 18A-18C . 
     A system model of an apparatus (DVD-Video player  100 ) that executes the aforementioned process will be briefly explained first. 
     &lt;System Model&gt; 
     Interactive DVD-Video player  100  which has been explained with reference to  FIG. 1  comprises DVD-Video playback engine  200  that plays back DVD-Video contents  10 , and ENAV engine  300  that plays back ENAV contents  30  (and/or  30 W). DVD-Video playback engine  200  outputs “DVD event” and “DVD status” signals to an event/command handler (corresponding to the event generation•command/property processor)  320  so as to notify an event or property in DVD-Video playback engine  200 . 
     Event/command handler  320  in ENAV engine  300  outputs an “ENAV event” and “ENAV property” to ENAV interpreter (corresponding to the ENAV interpreter)  330  so as to notify an event and property in response to the “DVD event” and “DVD status”. 
     ENAV interpreter  330  outputs an “ENAV command” to event/command handler  320  to control some functions (video•audio output unit  350  and the like) in ENAV engine  300  and DVD-Video playback. When the “ENAV command” is a command for DVD-Video playback control, event/command handler  320  outputs a “DVD control” signal to DVD-Video playback engine  200  so as to control DVD-Video playback. 
     &lt;Premises&gt; 
     This example is premised on that DVD-Video playback engine  200  successively plays back chapters 1, 2, 3, and 4 (from DVD video disc  1 ). On the other hand, ENAV contents  30  ( 30 W) are premised on that the contents include ENAV contents  1 ,  2 , and  3 . Note that each chapter created by the video contents provider is handled as Part of Title (PTT) in DVD-Video. 
     Under these premises, in this example, ENAV engine  300  plays back ENAV content  1  before playback of chapter 1 ( FIG. 18A ), plays back ENAV contents  2  in synchronism with playback of chapters 1 and 2 ( FIG. 18B ), and plays back ENAV content  3  in synchronism with playback of chapters 3 and 4 ( FIG. 18C ). 
     That is, in this example, ENAV content  1  has an event description that instructs to jump to ENAV content  2  at the beginning of chapter 1 (see t 10 , t 11 , t 14  in  FIG. 19 ). Also, ENAV content  3  has an event description that instructs to jump to ENAV content  3  at the beginning of chapter 3 (see t 30 , t 31 , t 34  in  FIG. 19 ). However, ENAV content  3  has no event description. 
     On the other hand, a “DVD event” signal from DVD-Video playback engine  200  is held in event/command handler  320  until ENAV interpreter  330  checks a corresponding ENAV event. If ENAV playback information in the ENAV content includes an event description, ENAV interpreter  330  periodically checks such event (see t 15  to t 17 , t 25  to t 26  in  FIG. 19 ). 
     When ENAV interpreter  330  checks an ENAV event, if a corresponding event is held in event/command handler  320 , ENAV interpreter  330  reads that event as an “ENAV event”. Then, the event in event/command handler  320  is cleared (deleted or erased) by ENAV interpreter  330 . 
       FIG. 19  is a view for explaining a case (case 1) wherein the DVD-Video playback engine outputs a PTT event with a chapter number as a DVD event at the beginning of each chapter, and the ENAV engine begins to play back corresponding ENAV contents. 
     &lt;Case 1&gt; 
     In this case, DVD-Video playback engine  200  outputs, as a DVD event, a PTT event (PTT Event(1) to PTT Event(4)) with a chapter number at the beginning (t 10 , t 20 , t 30 , t 40 , . . . ) of each chapter. Upon receiving this DVD event, event/command handler  320  holds the event with the chapter number as an ENAV event. ENAV interpreter  330  checks an ENAV event for PTT (chapter) and the number held in event/command handler  320  (t 11 , t 21 , t 31 , . . . ). If the checked number is “1” or “3”, ENAV engine  300  begins to play back an ENAV content (ENAV contents  2  and  3  in the example in  FIG. 19 ) corresponding to that number (t 14 , t 34 ), and that event (held in event/command handler  320 ) is cleared. 
     Note that  FIG. 19  exemplifies a case wherein playback of ENAV content  2  starts in response to PTT Event(1), playback of ENAV content  2  continues in response to PTT Event(2), playback of ENAV content  3  starts in response to PTT Event(3), and playback of ENAV content  3  continues in response to PTT Event(4) (not to start playback of ENAV content  4 ). However, such case is merely a descriptive example. There are many playback patterns of ENAV content m in response to PTT Event(n). 
       FIG. 22  is a flow chart for explaining an operation example of the DVD-Video playback engine, event generation•command/property processor, and ENAV interpreter in correspondence with the case of  FIG. 19  (case 1). 
     Assume that DVD-Video playback engine  200  in DVD-Video player  100  loaded with DVD video disc  1  with the format shown in  FIG. 30  or  31  starts playback of chapter n (initially, n=1) in a given video title set (VTS) recorded on the DVD-Video area (step ST 180 ). Then, DVD-Video playback engine  200  outputs PTT event (1) to event/command handler  320  at the beginning (t 10 ) of chapter 1 (PTT Event(n)=PTT Event(1); step ST 182 ), and starts playback of chapter 1 (step ST 184 ). During this interval, event/command handler  320  waits for an event (step ST 192 , NO in step ST 194 ). Note that PTT event (1) is one argument that describes chapter number “1”. 
     Upon receiving PTT event (1) (YES in step ST 194 ), event/command handler (event generation•command/property processor)  320 , which has waited for an event so far (step ST 192 , NO in step ST 194 ), holds a PTT event (ENAVPTT event) with chapter number “1” as an ENAV event (step ST 196 ). Event/command handler  320  maintains this event holding state while ENAV interpreter  330  does not read any event (NO in step ST 198 ). 
     When event/command handler  320  holds the ENAVPTT event with chapter number “1” (t 11  in  FIG. 19 ), ENAV interpreter  330  can read that event as an ENAV event (step ST 216  to be described later). When ENAV interpreter  330  reads an event (YES in step ST 198 ), event/command handler  320  clears the held event (step ST 200 ), and returns to an event wait state (step ST 202 ). 
     On the other hand, ENAV interpreter  330  checks the held event contents (ENAV event for PTT and its chapter number) of event/command handler  320  periodically (e.g., t 15 , t 16 , t 17 , . . . in  FIG. 19 ) (ST 212 ) while playback of given ENAV content m (e.g., ENAV content m=2 in  FIG. 19 ) is underway (step ST 210 ). Upon this event check, if event/command handler  320  does not held any event (NO in step ST 214 ), periodic event check is repeated. 
     The description will revert to t 10  in  FIG. 19 . After ENAV interpreter  330  reads an event (ENAVPTT event “1”) (t 11 ), ENAV engine  300  starts playback of a corresponding ENAV content (ENAV content  2  in this case) (t 14  and subsequent timings). 
     On the other hand, DVD-Video playback engine  200  continues to play back chapter 1 (n=1) (step ST 184 , NO in step ST 186 ). Upon completion of playback of chapter 1 (n=1) (YES in step ST 186 ), playback of chapter 2 (n+1=2) starts (step ST 188 ). As a result, the process of DVD-Video playback engine  200  returns to step ST 180  (except that chapter number n has been incremented by 1). 
     DVD-Video playback engine  200  outputs PTT event (2) at the beginning (t 20  in  FIG. 19 ) of chapter 2 (step ST 182 ). Then, ENAV interpreter  330  reads an ENAVPTT event with number “2” from event/command handler  320  (t 21 ; step ST 216 ). However, in this example, since ENAV content  2  has no event description associated with chapter 2, ENAV interpreter  330  ignores that event (ENAVPTT event with number “2”) (this process is included in a process executed when NO is determined in step ST 198 ). 
     DVD-Video playback engine  200  outputs PTT event (3) at the beginning (t 30  in  FIG. 19 ) of chapter 3 (step ST 182 ). Then, ENAV interpreter  330  reads an ENAVPTT event with number “3” from event/command handler  320  (t 31 ; step ST 216 ). In this example, since ENAV content  3  has an event description associated with chapter 3, ENAV interpreter  330  starts playback of that event (ENAVPTT event with number “3”) (step ST 220 ). 
     DVD-Video playback engine  200  outputs PTT event (4) at the beginning (t 40  in  FIG. 19 ) of chapter 4 (step ST 182 ). Then, event/command handler  320  holds an ENAVPTT event with number “4” (step ST 196 ). However, since this example assumes a case wherein ENAV content  3  has no event description, ENAV interpreter  330  skips event check (this process is included in a process executed when the process of ENAV interpreter  330  stays in the loop of NO in step ST 214 ). 
     Generally speaking, if event/command handler  320  holds an event (YES in step ST 214 ) upon event check, that event (ENAVPTT event with number “n”) is read (step ST 216 ). At this time, if ENAV contents  30  (and/or  30 W) do not include any ENAV content “m+1” corresponding to that event (ENAVPTT event “n”) (NO in step ST 218 ), the control returns to event check (step ST 212 ). During this interval, contents to be played back by ENAV engine  300  are ENAV content “m” in this example. On the other hand, if a script in the ENAV playback information describes ENAV content “m+1” at the read timing of ENAVPTT event “n” (YES in step ST 218 ), that ENAV content “m+1” is played back (step ST 220 ). 
     The process in  FIG. 22  can be summarized as follows. That is, in the process for playing back recorded contents that include DVD-Video contents  10  and ENAV contents  30  from DVD video disc  1  having a volume space complying with the DVD-Video standard, DVD-Video contents  10  of the recorded contents played back from DVD video disc  1  are acquired (step ST 180 ), and ENAV contents  30  of the recorded contents played back from DVD video disc  1  are acquired (step ST 210 ). Then, the contents of acquired ENAV contents  30  are executed (steps ST 194  to ST 220 ) in accordance with a predetermined event (step ST 182 ) corresponding to the contents of acquired DVD-Video contents  10 . 
     Note that ENAV engine  300  plays back ENAV contents  30  of the recorded contents on DVD video disc  1 , and controls playback of ENAV contents  30  in connection with that of DVD-Video contents  10  in accordance with the contents of ENAV contents  30  (broken arrows in  FIG. 22 ). This ENAV engine  300  is configured so that the contents of ENAV contents  30  change in combination, connection, or synchronism with a change in playback condition of DVD-Video contents  10  in the volume space complying with the DVD-Video standard (ENAV contents  1  to  3  change in combination with a change in chapters 1 to 3 of DVD-Video in  FIGS. 19 to 21 ; in other words, synchronization between DVD-Video playback and ENAV contents). 
       FIG. 20  is a view for explaining a case (case 2) wherein the DVD-Video playback engine exchanges event/status data with the ENAV engine, and the ENAV engine plays back ENAV contents on the basis of the exchange result. 
     &lt;Case 2&gt; 
     In this case, DVD-Video playback engine  200  outputs a PTT event to event/command handler  320  at the beginning (t 10 , t 20 , t 30 , t 40 , . . . ) of each chapter. After reception of the PTT event, event/command handler  320  holds this event as an ENAV event. ENAV interpreter  330  checks the ENAV event (ENAVPTT event) held in event/command handler  320 . If that ENAV event is a corresponding event (to an ENAV content which is ready to be played back at that time), ENAV interpreter  330  reads that event, and clears that event (held in event/command handler  320 ). 
     After that, ENAV interpreter  330  outputs ENAV read status (t 12 , t 22 , t 32 ) as an ENAV command in accordance with the description in the ENAV content (corresponding to that event). Then, event/command handler  320  outputs read status as a DVD control signal (t 12 , t 22 , t 32 ) to detect a chapter number upon playback. 
     Upon receiving the DVD control signal, DVD-Video playback engine  200  returns the chapter number as return status to event/command handler  320  (t 13 , t 23 , t 33 ). Then, event/command handler  320  returns the returned chapter number to ENAV interpreter  330  as ENAV return status (t 13 , t 23 , t 33 ). 
     In the example in  FIG. 20 , if the chapter number in ENAV return status is “1” or “3”, ENAV engine  300  begins to play back a corresponding ENAV content (ENAV content  2  or  3  in the example in  FIG. 20 ) (t 14 , t 34 ). If the chapter number in ENAV return status is neither “1” nor “3”, ENAV engine  300  does not start playback of another ENAV content (in the example of  FIG. 20 , if the ENAV content whose playback is underway is “2”, playback of that ENAV content  2  continues). 
     In the arrangement of  FIG. 1 , DVD-Video playback engine  200  can include DVD-Video controller  220  which controls playback of DVD video disc  1 , and has the following arrangement. That is, DVD-Video playback controller  220  outputs a DVD event signal associated with the playback condition (menu call, title jump, chapter jump, or the like) of DVD video disc  1  to event generation•command/property processor  320 , and also a DVD status signal associated with the property (audio language, sub-picture caption language, playback operation (play, stop, pause, fastforward, rewind, or the like), contents of the disc, and the like set in the player unit) of DVD video disc  1  to event generation•command/property processor  320 . 
     Note that event generation•command/property processor  320  can execute control of video•audio output unit  350  based on ENAV playback information contained in ENAV contents ( 30  or  30 W) in accordance with the DVD event signal (e.g., PTT event at t 10  in  FIG. 20 ) and/or DVD status signal (e.g., return status at t 13  in  FIG. 20 ). 
     The ENAV contents ( 30  or  30 W) can include first navigation contents ( 30 ) played back from DVD video disc  1 , and second navigation contents ( 30 W) acquired from an external system via a communication line (Internet or the like). 
     In this case, the control by event generation•command/property processor  320  in accordance with the DVD event signal and/or DVD status signal can be executed for the control processes based on both the first and second navigation contents ( 30 ,  30 W). 
     The DVD event signal is configured to be generated in correspondence with menu call that calls a menu recorded on DVD video disc  1 , title jump that switches a title to be played back from DVD video disc  1 , or chapter (PTT) jump that switches a chapter to be played back from DVD video disc  1 . 
       FIG. 23  is a flow chart for explaining an operation example of the DVD-Video playback engine, event generation•command/property processor, and ENAV interpreter in correspondence with the case of  FIG. 20  (case 2). 
     Assume that DVD-Video playback engine  200  in DVD-Video player  100  in  FIG. 1  loaded with DVD video disc  1  with the format shown in  FIG. 30  or  31  starts playback of chapter n (initially, n=1) in a given video title set (VTS) recorded on the DVD-Video area (step ST 230 ). Then, DVD-Video playback engine  200  outputs a PTT event to event/command handler  320  at the beginning (t 10 ) of chapter 1 (step ST 232 ), and starts playback of chapter 1 (step ST 234 ). During this interval, event/command handler  320  waits for an event (step ST 252 , NO in step ST 254 ). 
     Upon receiving the PTT event (YES in step ST 254 ), event/command handler  320  holds this PTT event as an ENAV event (step ST 256 ). During this interval, ENAV interpreter  330  plays back ENAV content m (step ST 280 ). 
     ENAV interpreter  330  periodically checks an ENAV event for PTT (ENAVPTT event) during playback of ENAV content m (t 15 , t 16 , t 17 , and the like in  FIG. 20 , although timings before t 10  are not shown; step ST 282 , NO in step ST 284 ). If event/command handler  320  holds an ENAVPTT event (YES in step ST 284 ), ENAV interpreter  330  reads that held ENAVPTT event as an ENAV event (t 10  to t 11 , t 20  to t 21 , t 30  to t 31 , and the like; step ST 286 ). 
     Event/command handler  320  waits (NO in step ST 258 ) until ENAV interpreter  330  reads the held ENAVPTT event. If ENAV interpreter  330  reads the held ENAVPTT event (t 11 , t 21 , t 31 , and the like; YES in step ST 258 ), the event held in event/command handler  320  is cleared (step ST 260 ). 
     After the ENAVPTT event is read, ENAV interpreter  330  outputs ENAV read status as an ENAV command (t 12 , t 22 , t 32 , and the like; step ST 288 ). 
     Event/command handler  320  waits (NO in step ST 262 ) until ENAV interpreter  330  outputs the ENAV command of read status. Upon receiving the ENAV command of read status from ENAV interpreter  330  (YES in step ST 262 ), event/command handler  330  outputs the read status command as a DVD control signal (t 12 , t 22 , t 32 , and the like; step ST 264 ). 
     Upon receiving the read status command (DVD control signal) (YES in step ST 236 ), DVD-Video playback engine  200  reads chapter number n (n=1 in this case) whose playback is now underway (step ST 238 ), and returns chapter number “1” as return status to event/command handler  320  (t 13 , t 23 , t 33 , and the like; step ST 240 ). If no read status command is received (NO in step ST 236 ), the processes in steps ST 238  and ST 240  are skipped. 
     After event/command handler  320  outputs the read status command, it waits for return status from DVD-Video playback engine  200  (step ST 266 , NO in step ST 268 ). Upon receiving return status from DVD-Video playback engine  200  (t 13 , t 23 , t 33 , and the like; YES in step ST 268 ), event/command handler  320  returns chapter number “1” as ENAV return status to ENAV interpreter  330  (t 13  in this case; step ST 270 ), and then waits for the next event (step ST 272 ). 
     ENAV interpreter  330  waits for ENAV return status from event/command handler  320  after it outputs ENAV read status (step ST 290 , NO in step ST 292 ). Upon receiving ENAV return status from event/command handler  320  (t 13 , t 23 , t 33 , and the like; YES in step ST 292 ), ENAV interpreter  330  reads chapter number n (n=1 in this case) that DVD-Video playback engine  200  is currently playing back (t 13  in this case; step ST 294 ). ENAV interpreter  330  checks if the ENAV playback information which is being executed includes a script of ENAV content “m+1” (“m+1”=2 if ENAV content m which is now being played back is “m=1”) corresponding to the event (ENAVPTT event) read in step S 286  (step ST 296 ). 
     In the example of  FIG. 20 , ENAV content  1  whose playback is now underway has an event description for a PTT event of chapter 1 (YES in step ST 296 ). With this event description, ENAV engine  300  begins to play back ENAV content  2  (t 14 ; step ST 298 ). 
     On the other hand, while no read status is output from event/command handler  320  (NO in step ST 236 ), or if DVD-Video playback engine  200  outputs return status to event/command handler  320  (step ST 240 ) after read status is output from event/command handler  320  (YES in step ST 236 ), DVD-video playback engine  200  continues the processes in steps ST 234  to ST 240  until playback of chapter n (initially, n=1) which is currently being played back comes to an end (NO in step ST 242 ). Upon completion of playback of that chapter n (=1) (YES in step ST 236 ), DVD-Video playback engine  200  begins to play back next chapter n+1 (=2) (t 20 ; step ST 244 ). 
     After completion of playback of chapter 1, DVD-Video playback engine  200  outputs a PTT event at the beginning (t 20 ) of chapter 2 (step ST 232 ). Then, event/command handler  320  holds this PTT event as an ENAV event (step ST 256 ). ENAV interpreter  330  checks this ENAV event for PTT (step ST 282 ), reads it as an ENAV event (t 21 ; ST 286 ), and then clears the event held in event/command handler  320  (step ST 260 ). 
     ENAV interpreter  330  sends a command (ENAV read status) to DVD-Video playback engine  200  to read a chapter number (which is currently being played back) via an ENAV command and DVD control signal (t 22 ; step ST 288 ). Then, ENAV interpreter  330  reads number “2” (as the number of the chapter which is currently being played back) from DVD-Video playback engine  200  via a DVD status signal and ENAV property (t 23 ; step ST 294 ). If ENAV content  2  does not include any event description for chapter 2 (NO in step ST 296 ), ENAV interpreter  330  continues to play back ENAV content  2  (t 23  to t 34 ). During this interval, DVD-Video playback engine  200  continues to play back chapter 2 (t 20  to t 30 ). 
     After completion of playback of chapter 2, DVD-Video playback engine  200  outputs a PTT engine at the beginning (t 30 ) of chapter 3 (step ST 232 ). Then, event/command handler  320  holds this PTT event as an ENAV event (step ST 256 ). ENAV interpreter  330  checks this ENAV event for PTT (step ST 282 ), reads it as an ENAV event (t 21 ; ST 286 ), and then clears the event held in event/command handler  320  (step ST 260 ). 
     ENAV interpreter  330  sends a command (ENAV read status) to DVD-Video playback engine  200  to read a chapter number (which is currently being played back) via an ENAV command and DVD control signal (t 32 ; step ST 288 ). Then, ENAV interpreter  330  reads number “3” (as the number of the chapter which is currently being played back) from DVD-Video playback engine  200  via a DVD status signal and ENAV property (t 33 ; step ST 294 ). In this case, since ENAV content  2  includes an event description for chapter 3, ENAV interpreter  330  starts playback of ENAV content  3  (t 34 ; step ST 298 ). 
     After completion of playback of chapter 3, DVD-Video playback engine  200  outputs a PTT engine at the beginning (t 40 ) of chapter 4 (step ST 232 ). Then, event/command handler  320  holds this PTT event as an ENAV event (step ST 256 ). If ENAV content  3  has no event description (NO in step ST 284 ), ENAV interpreter  330  skips event check (step ST 282 ) (or if it formally checks, no process is done in response to that check result). As a result, event/command handler  320  maintains the event held so far (step ST 256 , NO in step ST 258 ). 
     The process in  FIG. 23  can be summarized as follows. That is, in the process for playing back recorded contents that include DVD-Video contents  10  and ENAV contents  30  from DVD video disc  1  having a volume space complying with the DVD-Video standard, DVD-Video contents  10  of the recorded contents played back from DVD video disc  1  are acquired (step ST 230 ), and ENAV contents  30  of the recorded contents played back from DVD video disc  1  are acquired (step ST 280 ). Then, the contents of acquired ENAV contents  30  are executed (steps ST 254  to ST 298 ) in accordance with a predetermined event (step ST 232 ) corresponding to the contents of acquired DVD-Video contents  10 . 
     Note that ENAV engine  300  plays back ENAV contents  30  of the recorded contents on DVD video disc  1 , and controls playback of ENAV contents  30  in connection with that of DVD-Video contents  10  in accordance with the contents of ENAV contents  30  (broken arrows in  FIG. 23 ). This ENAV engine  300  is configured so that the contents of ENAV contents  30  change in combination, connection, or synchronism with a change in playback condition of DVD-Video contents  10  in the volume space complying with the DVD-Video standard (ENAV contents  1  to  3  change in combination with a change in chapters 1 to 3 of DVD-Video in  FIGS. 19 to 21 ; in other words, synchronization between DVD-Video playback and ENAV contents). 
       FIG. 21  is a view for explaining another case (case 3) wherein the DVD-Video playback engine outputs a PTT event with a chapter number as a DVD event at the beginning of each chapter, and the ENAV engine begins to play back corresponding ENAV contents. 
     &lt;Case 3&gt; 
     In this case, ENAV interpreter  330  outputs an enable PTT number for a PTT event in advance to event/command handler  320  (t 01  in  FIG. 21 ). As a result, an output request of only a corresponding ENAVPTT event (to the enable PTT number output in advance) is issued. 
     DVD-Video playback engine  200  outputs, as a DVD event signal, a PTT event with a chapter number at the beginning (t 10 , t 20 , t 30 , t 40 ) of each chapter. Event/command handler  320  checks if this DVD event signal is for PTT for a requested chapter (by the enable PTT number output in advance). If this DVD event signal is the requested one, event/command handler  320  holds the ENAVPTT event with the chapter number (t 11 , t 31 , and the like). Otherwise, this DVD event signal for PTT is not held in event/command handler  320 . 
     ENAV interpreter  330  checks the ENAV event held in the event/command handler  320  (t 11 , t 15 , t 16 , t 17 , . . . ). If the checked ENAV event is a corresponding event (to the enable PTT number output in advance) (check result at, e.g., t 11 ), ENAV interpreter  330  reads that event (e.g., ENAVPTT event with number “1”), and then clears that event held in event/command handler  320 . After that, ENAV engine  300  begins to play back a corresponding ENAV content (ENAV content  2  in the example of  FIG. 21 ) (t 14 ). 
     Note that the requested PTT event (corresponding to the enable PTT number output in advance) can be selected on the DVD-Video playback engine  200  side. As a result, the “requested PTT event” can be sent from DVD-Video playback engine  200  to only event/command handler  320 . 
       FIG. 24  is a flow chart for explaining an operation example of the DVD-Video playback engine, event generation•command/property processor, and ENAV interpreter in correspondence with the case of  FIG. 21  (case 3). 
     Assume that DVD-Video playback engine  200  in DVD-Video player  100  loaded with DVD video disc  1  with the format shown in  FIG. 30  or  31  starts playback of chapter n (initially, n=1) in a given video title set (VTS) recorded on the DVD-Video area (step ST 300 ). Then, DVD-Video playback engine  200  outputs a PTT event (n=1) to event/command handler  320  at the beginning (t 10 ) of chapter 1 (step ST 302 ), and starts playback of chapter 1 (step ST 304 ). Playback of this chapter continues until it comes to an end. Upon completion of playback of that chapter (n=1) (t 20 ; YES in step ST 306 ), playback of the next chapter (n+1=2) starts (step ST 308 ). 
     During this interval, event/command handler  320  waits for an event (step ST 312 , NO In step ST 318 ). Also, during this interval, ENAV interpreter  330  waits until a description of an event request appears in ENAV playback information in ENAV content m (initially, m=1) (NO in step ST 332 ), while it plays back ENAV content m (ST 330 ). 
     If the ENAV content has a description of an event request (YES in step ST 322 ), ENAV interpreter  330  outputs an enable PTT event with enable PTT number “1” for a PTT event to event/command handler  320  at an appropriate timing (t 01 ; step ST 334 ). This output timing is preferably set before DVD-Video playback engine  200  outputs PTT event (1). Upon issuing this event request with the enable PTT number (YES in step ST 314 ), the event request (enable PTT event (1)) is held in event/command handler  320  (step ST 316 ). Event/command handler  320  waits until it receives a PTT event from DVD-Video playback engine  200 . 
     DVD-Video playback engine  200  outputs PTT event (1) to event/command handler  320  at the beginning (t 10 ) of chapter 1 (step S 302 ). Note that PTT event (1) is one argument that describes chapter number “1”. 
     Upon receiving PTT event (1) (YES in step ST 318 ), since that event is the “requested PTT event (enable PTT event (1)) (YES in step ST 320 ), event/command handler  320  holds the PTT event with chapter number “1” as an ENAV event (step ST 322 ). 
     ENAV interpreter  330  checks the ENAV event for PTT and its chapter number (step ST 336 ). At this time, since event/command handler  320  holds ENAVPTT event (1) with chapter number “1” (YES in step ST 338 ), ENAV interpreter  330  reads that event as an ENAV event (step ST 340 ). After ENAVPTT event (1) is read by ENAV interpreter  330  (YES in step ST 334 ), event/command handler  320  clears the held event (step ST 326 ), and then waits for the next event (step ST 328 ). 
     After ENAVPTT event (1) is read (step ST 340 ), if an ENAV content (m+1=2) corresponding to the read event is included in ENAV playback information at that time (YES in step ST 342 ), ENAV interpreter  330  begins to play back ENAV content  2  (t 14 ; step ST 344 ). 
     Likewise, ENAV interpreter  330  outputs enable PTT number “3” for a PTT event to event/command handler  320  (t 03 ; step ST 334 ). 
     After completion of playback of chapter 1 (YES in step ST 306 ), DVD-Video playback engine  200  outputs PTT event (2) to event/command handler  320  at the beginning (t 20 ) of chapter 2 (step ST 302 ). However, in this example, since ENAV interpreter  330  does not request an ENAVPTT event with chapter number “2” (NO in step ST 320 ), event/command handler  320  does not hold that event (PTT event (2)). After completion of playback of chapter 2 (YES in step ST 306 ), if DVD-Video playback engine  200  outputs PTT event (3) to event/command handler  320  (step ST 302 ) at the beginning (t 30 ; step ST 308 ) of chapter 3, event/command handler  320  holds a PTT event with chapter number “3” (step ST 322 ). Then, ENAV interpreter  330  checks the ENAV event for PTT and its number (step ST 336 ). After that, ENAV interpreter  330  reads that (checked) event as an ENAV event (step ST 340 ). After the event is read (YES in step ST 324 ), the event held in event/command handler  320  is cleared (step ST 326 ). If an ENAV content (ENAV content  3  in this case) corresponding to the read event is described in ENAV playback information (YES in step ST 342 ), ENAV engine  300  starts playback of that ENAV content  3 . (t 34 ; step ST 344 ). 
     After completion of playback of chapter 3 (YES in step ST 306 ), DVD-Video playback engine  200  outputs PTT event (4) to event/command handler  320  at the beginning (t 40 ; step ST 308 ) of chapter 4 (step ST 302 ). However, event/command handler  320  does not hold a PTT event with chapter number “4”. This is because ENAV interpreter  330  does not request any ENAVPTT event with chapter number “4” in this example (NO in step ST 320 ). 
     The process in  FIG. 24  can be summarized as follows. That is, in the process for playing back recorded contents that include DVD-Video contents  10  and ENAV contents  30  from DVD video disc  1  having a volume space complying with the DVD-Video standard, DVD-Video contents  10  of the recorded contents played back from DVD video disc  1  are acquired (step ST 300 ), and ENAV contents  30  of the recorded contents played back from DVD video disc  1  are acquired (step ST 330 ). Then, the contents of acquired ENAV contents  30  are executed (steps ST 314  to ST 344 ) in accordance with a predetermined event (output or the like of step ST 302 ) corresponding to the contents of acquired DVD-Video contents  10 . 
     Note that ENAV engine  300  plays back ENAV contents  30  of the recorded contents on DVD video disc  1 , and controls playback of ENAV contents  30  in connection with that of DVD-Video contents  10  in accordance with the contents of ENAV contents  30  (broken arrows in  FIG. 24 ). This ENAV engine  300  is configured so that the contents of ENAV contents  30  change in combination, connection, or synchronism with a change in playback condition of DVD-Video contents  10  in the volume space complying with the DVD-Video standard (ENAV contents  1  to  3  change in combination with a change in chapters 1 to 3 of DVD-Video in  FIGS. 19 to 21 ; in other words, synchronization between DVD-Video playback and ENAV contents). 
     DVD-Video player  100  of  FIG. 1 , which has the functions/arrangement that have been explained using  FIGS. 2 to 24 , can have the following operation mode and display mode. That is, this player  100  has a video mode (an inactive or event wait state of ENAV engine  300 ) and interactive mode (an active state of ENAV engine  300 ) in association with its operation, and has a full video mode ( FIG. 7  and the like), full navigation mode ( FIG. 8  and the like), and mixed mode ( FIGS. 2 ,  3 ,  11 ,  12 , and the like) in association with its display. 
     When DVD-Video playback engine  200  plays back DVD video contents  10  in the video mode (e.g., ST 10  to ST 18  in  FIG. 6 , or ST 40  to ST 48  in  FIG. 10 ), the full video mode is used to display the playback video. 
     When ENAV engine  300  plays back ENAV contents  30  (and/or  30 W) in the interactive mode (e.g., ST 20  to ST 36  in  FIG. 6 ), the full navigation mode is used to display the playback video (ST 34  to ST 36  in  FIG. 6 ). 
     Or when DVD-Video playback engine  200  plays back DVD video contents  10  and ENAV engine  300  plays back ENAV contents  30  (and/or  30 W) in the interactive mode (e.g., ST 50  to ST 66  in  FIG. 10 ), the mixed mode is used to display the playback video of DVD video contents  10  and that of ENAV contents  30  (and/or  30 W) (ST 64  to ST 66  in  FIG. 10 ). 
     In the mixed mode, the video contents of DVD video contents  10  and those of ENAV contents  30  (and/or  30 W) can be displayed together ( FIGS. 3 ,  3 ,  11 , and  12 ). 
     Furthermore, when DVD-Video playback engine  200  plays back DVD video contents  10  in the interactive mode (e.g., ST 10  to ST 18  in  FIG. 6 , or ST 40  to ST 48  in  FIG. 10 ), the full video mode is used to display the playback video. 
     The embodiment of the present invention implements a new contents providing method that integrates package media such as DVD-Video and the like, and on-line media which exploit the Internet and the like. This “new contents providing method” especially relates to switching of the start and end operations of synchronization (or, connection or combination) between off- and on-line contents. 
     Upon displaying off- and on-line contents on the user interface (on the display screen), there are roughly the following three modes: 
     (1) an off-line mode that displays using an off-line contents dedicated layout; 
     (2) an on-line mode that displays using an on-line contents dedicated layout; and 
     (3) a mixed mode that displays using a mixed layout of these contents. 
     Furthermore, since each mode has normal and abnormal display states, the states are classified as follows. 
     (1) In the off-line mode, 
     [1-1] normal display; and 
     [1-2] abnormal display off-line contents data is illegal or cannot be input due to some transmission error. 
     (2) In the on-line mode, 
     [2-1] normal display; and 
     [2-2] abnormal display . . . on-line contents data is illegal or cannot be input due to some transmission error. 
     (3) In the mixed mode, 
     [3-1] normal display (synchronous or simultaneous display); and 
     [3-2] abnormal display . . . off- or on-line contents data is illegal or cannot be input due to some transmission error. 
     Note that, for example, off-line contents data cannot be normally displayed when 
     [1-2-1] a disc is not normally loaded, 
     [1-2-2] information written on a disc cannot be normally read out due to defects or the like, and so forth. 
     Also, on-line contents data cannot be normally displayed when 
     [2-2-1] an on-line state is not established (net connection is not established), 
     [2-2-2] on-line information cannot be normally received due to communication errors or the like, and so forth. 
     Note that abnormalities in the off-line/on-line mixed mode occur due to combinations of individual causes. 
       FIG. 25  is a view for explaining selectable paths among a plurality of modes (off-line mode, on-line mode, mixed mode) in the system arrangement of  FIG. 1 . In this embodiment, an outline of processes in the respective modes, i.e., the off-line mode, on-line mode, and mixed mode, and transitions among these modes will be explained. 
     Actual transitions along selectable paths exemplified in  FIG. 25  can be made by the user setups. For example, when DVD video disc  1  is ejected from a disc drive (not shown) equipped in DVD-Video player  100  in  FIG. 1  in off-line mode M 1  (switch event E 02 ), the control can transit to on-line mode M 2  and can display on-line information. Or in off-line mode M 1 , internal display information (an on-screen display (to be abbreviated as OSD hereinafter) used to set operation parameters of the player itself, and the like) of player  100  can be displayed independently of disc  1  and net (communication line). 
     From on-line mode M 2 , the control can transit to off-line mode M 2  or mixed mode M 3  upon detection of loading of disc  1  (switch event E 01  or E 03 ). If such mode transition function is disabled (by, e.g., user&#39;s operation via the OSD of the player itself), display can be continued in on-line mode M 2 , even when the aforementioned switch event has occurred. 
     In general, since the information can be read out from DVD video disc  1  loaded in DVD-Video player  100  faster than information exchange via the net such as the Internet or the like, off-line contents playback (DVD-Video playback) can improve the quality of displayed images (information can be read out at a rate of 10 Mbps or higher in DVD-Video playback). 
     In the interactive mode (M 3 ) in  FIG. 25 , display exemplified in  FIG. 2 ,  3 ,  11 , or  12  can be made. In this case, the ENAV contents can be downloaded not only from disc  1  but also from the Internet. 
     If free transitions are allowed among various modes, as shown in  FIG. 25 , the appeal of the entire contents can be improved by combining the off-line contents (DVD-Video contents  10 ) and latest information (Web contents  30 W) on the net (as an example that can improve the appeal of the entire contents using mixed mode M 3 , an on-line battle game is known). 
     For this reason, transition from on-line mode M 2  to mixed mode M 3  upon loading of disc  1  (switch event E 03 ) brings some advantages to the user. The same applies to transition from off-line mode M 1  to mixed mode M 3  upon detection of net connection (switch event E 05 ). By contrast, when disc  1  is ejected in mixed mode M 3  (switch event E 04 ), the control can transit to on-line mode M 2  or can continue a process in a processing routine determined in mixed mode M 3 . When net disconnection is detected (switch event E 06 ) in mixed mode M 3 , the control can automatically return to off-line mode M 1 . 
     The aforementioned mode transitions can be made according to a method (e.g., transition rule  1  in  FIG. 29  to be described later) determined in advance in player  100 , or a user&#39;s request. 
     Since the mode transition takes time, a problem about screen display during that time is posed. In this embodiment, this problem can be solved by executing the following process before the screen display of the transition destination is ready, upon making mode transition. That is, a still image (stored in a video RAM (not shown) in video output controller  352  in  FIG. 1 ) immediately before transition of a video (irrespective of a moving or still image) displayed on the screen so far is frozen and displayed on the screen. When the screen display of the transition destination is ready, the frozen image (still image) displayed on the screen so far is seamlessly switched to a screen display image of the transition destination. Or upon making mode transition, a blueback video (that may include an OSD image of the player as needed) is displayed on the screen before the screen display of the transition destination is ready. Then, when the screen display of the transition destination is ready, the blueback video displayed on the screen so far is switched to a screen display image of the transition destination. 
       FIG. 26  is a flow chart for explaining an example of which one of the plurality of modes shown in  FIG. 25  is set first. The process of this flow chart can be written in a program ROM (not shown) as an initial setup program (a part of firmware) of DVD-Video player  100  in  FIG. 1 . When the user has pressed, e.g., a setup menu button (not shown) of a remote controller (not shown), a mode select menu is displayed as, an on-screen display (OSD), on the display screen of an external monitor TV (not shown) connected to video output controller  352  (step ST 400 ). 
     This mode select menu includes select buttons of off-line mode M 1 , on-line mode M 2 , and mixed mode M 3 , and an OK button, although not shown. If the user has selected one of the select buttons of off-line mode M 1 , on-line mode M 2 , and mixed mode M 3 , and has pressed the OK key by operating cursor keys and the OK key of the remote controller (not shown) (YES in step ST 410 ), the selected mode (e.g., mixed mode M 3 ) is set in player  100  of  FIG. 1  (step ST 420 ). For example, even when off-line mode M 1  is a default mode, if the user selects none of these modes (NO in step ST 410 ), the default mode (off-line mode M 1  in this example) is set in player  100  of  FIG. 1  (step ST 430 ). Upon completion of the setup of the mode selected by the user or as the default mode (step ST 500 ), the process in  FIG. 26  ends, and player  100  of  FIG. 1  is ready to operate in the set mode (step ST 440 ). 
       FIG. 27  is a flow chart for explaining an example of the processing contents in the current mode (the default mode or the mode of user&#39;s choice set in step ST 500  in  FIG. 26 ) in one of the plurality of modes shown in  FIG. 25 . The process of this flow chart can also be written in a program ROM (not shown) as an initial setup program of DVD-Video player  100  in  FIG. 1 . 
     It is checked if a normal process can be done using the mode (M 1 , M 2 , or M 3 ) set by the mode setup process (step ST 500 ) in  FIG. 26  as the current mode (step ST 510 ). If a normal process can be done (e.g., a normal DVD video disc playback in on-line mode/interactive mode M 2 ) (YES in step ST 510 ), that process is executed (step ST 520 ). During this process, the processing program in  FIG. 27  repeats status check (the loading state of disc  1 , the playback operation state of disc  1 , the connection state of a communication line such as the Internet or the like, the presence/absence of switching among modes M 1  to M 3 , and the like) (step ST 530 ). For example, if the user has operated the remote controller to switch the current mode from mode M 2  to mode M 3 , that mode switch operation is executed (step ST 540 ). Or if the user has changed the chapter number of a DVD-Video work, playback of which is underway, the chapter switch operation is executed in response to that user event, and the ENAV content playback switch operation in, e.g., steps ST 194  to ST 220  in  FIG. 22 , can be made (step ST 540 ). 
     If a normal process cannot be done in the current mode (NO in step ST 510 ), the control starts an abnormal process (step ST 550 ). For example, if a disc tray (not shown) of player  100  is not closed when the user has pressed a play start button of the remote controller (not shown) in mode M 2 , a process for closing the disc tray is executed (step ST 550 , NO in step ST 560 ), and a normal process is executed in current mode M 2  (YES in step ST 510 ). If disc  1  set on the disc tray suffers serious scratches, and its lead-in area, volume/file structure information area, or management information (VMG or the like in  FIG. 30 ) cannot be read (NO in step ST 510 ), since the abnormal process limit has been exceeded (YES in step ST 560 ), the system of player  100  terminates abnormally (step ST 570 ). 
     In the above description, on-line mode/interactive mode M 2  has been exemplified. The flow of the process in  FIG. 27  remains the same irrespective of whether the mode in  FIG. 27  is off-line mode/video mode M 1  or mixed mode/interactive mode M 3  (except for their processing contents). For example, when a communication partner on the net has disconnected communication connection (this state can be determined by the status check process in step ST 530 ), the system terminates abnormally (step ST 570 ). 
       FIG. 28  is a flow chart for explaining the contents of the status check process (step ST 530 ) in the processing shown in  FIG. 27 . In this case, a processing example executed when the control automatically transits to a mode different from the current mode depending on whether or not DVD disc  1  is inserted in DVD-Video player  100 , and whether or not the Internet connection unit ( 400 W,  400 W*) is connected to the Internet or the like will be explained. The process of this flow chart can also be written in a program ROM (not shown) as an initial setup program of DVD-Video player  100  in  FIG. 1 . 
     When the control enters this status check process (step ST 530 ), the loading state of disc  1  is checked first (step ST 532 ). This check process can include additional check processes for checking whether or not the disc tray of the disc drive (not shown) is open, whether or not a disc is normally set on the disc tray if the disc tray is closed, whether or not the disc is one readable by player  100  if the disc is normally set (i.e., whether or not that disc complies with the DVD standard), and whether or not that disc is a defective one which suffers scratches, warps, and/or cracks. 
     If this check process finds an irreparable problem such as an unreadable disc, the system terminates abnormally (step ST 570  in  FIG. 27 ). However, if an error found is reparable (e.g., normal disc  1  is set, but the disc tray is not closed), the process for removing that error is executed (step ST 550  in  FIG. 27 ), and the flow returns to the status check process (step ST 530 ). 
     Upon completion of the check process of the loaded state of disc  1 , the connection state of a communication line such as the Internet or the like is checked (step ST 534 ). This check process can include additional check processes for checking whether or not the Internet connection unit ( 400 W,  400 W*) in  FIG. 1  is both physically and logically normally connected to a communication modem, whether or not modem hardware or TCP/IP software suffers any operation abnormality, and whether or not net connection with a communication partner has been established (check net connection/disconnection). 
     If this check process finds an irreparable problem such as any communication modem error or the like, the system terminates abnormally (step ST 570  in  FIG. 27 ). On the other hand, if the process finds a reparable, temporary problem (e.g., the power switch of an external modem is OFF, but it is turned on later), the process for logically connecting the modem to the Internet connection unit in  FIG. 1  or the like is executed (step ST 550  in  FIG. 27 ), and the flow then return to the status check process (step ST 530 ). 
     Upon completion of the status check processes of the loaded state of disc  1  (step ST 532 ) and the net connection state (step ST 534 ), the transition destination of the mode is determined (step ST 536 ) on the basis of a predetermined transition rule in accordance with the check result (corresponding to, e.g., one of switch events E 01  to E 06  in  FIG. 25 ). After the check results of the loaded state of disc  1  (step ST 532 ) and net connection state (step ST 534 ) are temporarily stored in a memory (not shown), the control jumps to a process (its processing contents are shown in  FIG. 27 ) of the determined mode (step ST 538 ). 
     Note that mode transition by means of jump in step ST 538  can be made according to a method (transition rule) determined in advance in the system of player  100  or user&#39;s request. As a method of making mode transition according to the user&#39;s request, for example, the control enters the mode select process (step ST 400 ) in  FIG. 26  in response to depression of a menu button on the remote controller (not shown), and the control transits to a mode of user&#39;s choice in step ST 420  in that process. On the other hand, the following method of making mode transition according to the method (transition rule) determined in advance in the system of player  100  may be used. 
       FIG. 29  is a view for explaining an example of transition rule (transition rule  1 ) which is to be referred to upon determining the mode transition destination in the process in  FIG. 28 . In this case, assume that modes that allow mutual transition are modes M 1  to M 3  shown in  FIG. 25 . That is, in a rule, the current mode is mode M 1 , M 2 , or M 3 , switch events are uniquely assigned to each mode, and a mode as the transition destination is determined in correspondence with that switch event. 
     More specifically, when the current mode is off-line mode (video mode) M 1 , if switch event E 02  (disc ejection) is detected, transition to on-line mode (interactive mode) M 2  is designated; if switch event E 05  (net connection) is detected, transition to mixed mode (interactive mode) M 3  is designated. If two switch events E 02  and E 05  have occurred at the same time, this example preferentially selects switch event E 05  (net connection) (priority: E 05 &gt;E 02 ). When switch event E 02  has occurred prior to switch event E 05 , mode transition corresponding to the event that has occurred earlier is designated irrespective of the priority (mode transition corresponding to the event that has occurred later is designated after the first mode transition). 
     When the current mode is on-line mode (interactive mode) M 2 , if switch event E 01  (disc insertion/loading) is detected, transition to off-line mode (video mode) M 1  is designated; if switch event E 03  (disc insertion/loading) is detected, transition to mixed mode (interactive mode) M 3  is designated. These two switch events E 01  and E 03  are switch triggers which have been generated due to an identical cause (disc insertion/loading), but this example preferentially select switch event E 03  (priority: E 03 &gt;E 01 ). These priority levels may be reversed by the user setup (priority: E 03 &lt;E 01 ). Or one of switch events E 01  and E 03  may be disabled in advance. 
     When transition from mode M 2  to mode M 1  is to be effected in response to the switch trigger “disc insertion/loading”, the user may select mode M 1  in step ST 420  in  FIG. 26 . At this time, this user selection has a higher priority level than transition rule  1  in  FIG. 29 . 
     Likewise, when the current mode is mixed mode (interactive mode) M 3 , if switch event E 06  (net disconnection) is detected, transition to off-line mode (video mode) M 1  is designated; if switch event E 04  (disc ejection) is detected, transition to on-line mode (interactive mode) M 2  is designated. If two switch events E 06  and E 04  have occurred at the same time, this example preferentially selected switch event E 06  (net disconnection) (priority: E 06 &gt;E 04 ). When switch event E 04  has occurred prior to switch event E 06 , mode transition corresponding to the event that has occurred earlier is designated irrespective of the priority (mode transition corresponding to the event that has occurred later is designated after the first mode transition). 
       FIG. 29  shows an example of transition rule  1  upon making automatic mode transition from a given mode to another mode. A plurality of kinds of transition rules may be used in this case. For example, as transition rule  2  which is used together with transition rule  1  in  FIG. 29  as needed, a second transition rule [“event generated by the system upon occurrence of abnormal circumstances”&gt;“user event”&gt;“ENAV event”] may be applied. 
     Note that examples of the abnormal circumstances include an error that has occurred during execution of a system program which controls the operation of the overall apparatus in  FIG. 1 , a computer virus that has been found upon downloading Web contents from the Internet, and so forth. 
     The relationship between the mode transition and DVD-Video player  100  explained using  FIG. 1  can be summarized as follows. That is, ENAV engine  300  in  FIG. 1  has a first interface ( 400 ,  400 *) for receiving ENAV contents  30  from DVD video disc  1  which has a volume space complying with the DVD-Video standard, and a second interface ( 400 W,  400 W*) for acquiring other ENAV contents (Web contents  30 W) from a communication line (Internet). 
     Assume that a state wherein DVD video disc  1  is loaded in DVD-Video player  100 , and the second interface ( 400 W,  400 W*) is disconnected from the communication line (net disconnection) is off-line mode M 1 , a state wherein DVD video disc  1  is ejected from DVD-Video player  100 , and the second interface ( 400 W,  400 W*) is disconnected from the communication line (net disconnection) is on-line mode M 2 , and a state wherein DVD video disc  1  is loaded in DVD-Video player  100 , and the second interface ( 400 W,  400 W*) is connected to the communication line (net connection) is mixed mode M 3 . Then, if a switch trigger (a trigger due to disc insertion/ejection or net connection/disconnection; corresponding to switch events E 01  to E 06 ) is detected, mode transition is automatically made among off-line mode M 1 , on-line mode M 2 , and mixed mode M 3  (in accordance with a predetermined transition rule exemplified in  FIG. 29 ). 
     Note that the present invention is not limited to the aforementioned embodiments, and various modifications and changes may be made without departing from the scope of the invention when it is practiced. The respective embodiments may be combined as needed as long as possible, and combined effects can be obtained in such case. 
     For example, the ENAV engine of the present invention can be incorporated in a Hi-vision compatible DVD-Video system (a semi-Hi-Vision system using 650-nm laser or a full-Hi-Vision system using 405-nm laser), which will be realized in the near future, without disturbing system compatibility. 
     The functions of the player in  FIG. 1  can be implemented by software using a personal computer which comprises a DVD disc drive and high-speed CPU/MPU. That is, DVD player  100  corresponding to  FIG. 1  can be virtually created on a high-performance personal computer (such virtual DVD player on the personal computer is implemented in commercially available personal computers and some game machines). In this case, the present invention can be practiced in the form of novel software, which utilizes hardware, i.e., an existing personal computer, and is installed in that personal computer. 
     Furthermore, the embodiments include inventions of various stages, and various inventions can be extracted by appropriately combining a plurality of required constituent elements disclosed in this application. For example, if at least one of the effect of the present invention or an effect upon practicing the present invention is obtained even when one or a plurality of required constituent elements are omitted from all the required constituent elements in the embodiments, the arrangement from which constituent elements are omitted can be extracted as the invention. 
       FIG. 34  is a flow chart for explaining an example of recording processes of information on an information medium such as a DVD-Video disc, DVD-Audio disc, a hard disc, or the like. 
     As shown in  FIG. 34 , AV contents of DVD-Video (e.g., DVD-Video contents  10  in  FIG. 2 ) are recorded in a specific portion (DVD-Video Area in  FIG. 30  or  31 ) of the volume space (step ST 602 ). Then, navigation contents (e.g., any of ENAV contents  30 A- 30 C in  FIG. 2 ) are recorded in a given portion (Other Recording Area in  FIG. 30  or part of DVD-Video Area in  FIG. 31 ) (step ST 604 ). Incidentally, an order of recording steps ST 602  and ST 604  may be exchanged. 
     &lt;Summary of ENAV System&gt; 
     An ENAV (Enhanced NAVigation) specification, applied to the embodiment of the present invention, enables a DVD player to realize advanced interactively, and new content defined in the ENAV specification is called “ENAV content.” The ENAV content can be recorded with DVD-Video content on a DVD-Video disc and some of ENAV content can be recorded on (or sent via) a web server. Also, the current DVD-Video specification itself is not affected by the ENAV specification, that is, the ENAV specification is just “extension” of the DVD-Video specification. The ENAV specification defines ENAV content and also defines a mechanism to communicate between DVD-Video and ENAV playback. 
     ENAV content consists of (or comprises) following elements, called “ENAV elements”: 
     Markup Language (XHTML, SMIL); 
     Script Language (ECMAScript) with particular APIs for DVD; 
     Cascading Style Sheet (CSS); 
     Image (JPEG, PNG); 
     Audio (AC-3 (Trademark), MPEG audio, DTS (Trademark), SDDS (Trademark)); 
     Animation (MNG, XSS, Macromedia Flash (Trademark)); and 
     Text/Font. 
     As for Markup Language, XHTML document controls a display layout, display size and display/output timing and also controls synchronization to display/output above Image data, Audio data, Animation data and Text/Font data in conjunction with DVD-Video content. Meanwhile, SMIL controls only display of SVG animation. 
     ENAV content can exist not only in a disc but in a server. But, at least DVDINDEX.HTM file, XHTML document for start-up may be recorded under DVD_ENAV directory on a disc. Also, Files of ENAV content are delivered from a server via Internet after authorization between an Enhanced DVD player and the server by means of the disc ID of Enhanced DVD disc and/or player ID of Enhanced DVD player. After the completion of authorization, if an Enhanced DVD disc is ejected, deliver of ENAV content from the server can be stopped and/or the playback of ENAV content can be stopped. 
     Enhanced DVD player, which has capability to play back ENAV content, has two modes; one is Video mode, the other is Enhanced Navigation mode. 
     In Video mode, DVD-Video content is played back according to Navigation Information in DVD-Video content, and ENAV content is not played back even if it is recorded on a disc. So, in this mode, behavior of a player is as same as a legacy DVD-Video player, that is, First Play PGC (FP_PGC) may be played back at first. In Video mode, only one Screen display exists: Full Video Screen. 
     Enhanced Navigation mode has two Screen displays: Full Screen display and Mixed Screen display. In Full Screen display, a player plays back both DVD-Video content and ENAV content simultaneously. In Mixed Screen display, a player also plays back both DVD-Video content and ENAV content, and both contents are displayed simultaneously. 
     Note: User operation and ‘looks and feels’ might be different in Full Screen Display from Full Video Screen because playback and user operations are handled by ENAV content. 
     In Enhanced Navigation mode, between Full Screen display and Mixed Screen Display, it is possible to switch Screen display as a function of ENAV content or a player&#39;s function (i.e., from Full Screen display to Mixed Screen display/from Mixed Screen display to Full Screen display). But it is prohibited to switch between modes (Video Mode and Enhanced Navigation Mode) during a mode being activated. 
     In Enhanced Navigation mode, a player may ignore FP_PGC and may play back DVDINDEX.HTM file for startup in ENAV content on a disc firstly, and then plays back according to the instruction of ENAV content. 
     The system model for Enhanced DVD player is introduced in this specification. It consists of (or comprises) two engines, one is DVD-Video playback engine to play back DVD-Video content and the other is ENAV engine to play back ENAV content and also to control DVD-Video playback engine. This means the player is extended one from a legacy DVD-Video player. 
     DVD-Video playback engine consists of (or comprises) a legacy DVD-Video playback engine and the following additional functions, which are utilized by ENAV content to control DVD-Video playback; 
     Function to control DVD-Video playback in response to “DVD control” from ENAV engine; 
     Function to inform “DVD trigger” to ENAV engine, which are some events required by ENAV content; and 
     Function to inform “DVD status”, which are some of properties, such as player status/latest playback status etc, in response to the request from ENAV engine. 
     ENAV engine includes ENAV Buffer, XHTML+SMIL/CSS Parser, XHTML/CSS Layout Manager, ECMAScript Interpreter &amp; DOM manipulator, SMIL Timing Engine, ENAV Interface Handler, Element Decoders, AV Renderer, Buffer Manager, and Network Manager. 
     # ENAV Buffer 
     ENAV content on both a disc and a server is loaded to the buffer for continuous/seamless playback of DVD-Video content, and the buffer can be managed by Buffer Manager via Buffer control. ENAV Buffer consists of (or comprises) ENAV-Unit Buffer (for XHTML document, Image, Non-synchronized audio with DVD-Video and Animation), Synchronized Audio Buffer and Font Buffer. The ENAV-Unit Buffer and the Synchronized Audio Buffer consist of (or comprises) two buffers respectively. One buffer is for playback and the other buffer is for download, each role changes by turns. The two-buffer can be used as one-buffer, for instance, in case that all of ENAV elements are read to the buffer before playback of ENAV content. 
     ENAV-Unit Buffer is the buffers to store ENAV-Unit, which is composed of (or may be formed of) at lest one XHTML document, Image, Non-synchronized audio and Animation. 
     Before starting playback of DVD-Video synchronized with ENAV contents, at least one ENAV-Unit is preloaded from a disc or a server. When another ENAV-Unit is loaded from a disc during the playback of DVD-Video, seamless playback of DVD-Video is not guaranteed. When another ENAV-Unit is downloaded from a server during the playback of DVD-Video, seamless playback of DVD-Video is guaranteed by means of the downloading information, which includes name/location/size/content type of ENAV elements. 
     # XHTML+SMIL/CSS Parser 
     XHTML document, composed of text information, some inline style, ECMAScript and CSS (Cascading Style Sheet) is read into XHTML parser. The XHTML parser verifies and parses the document into internal forms of objects, DOM-tree, based on definition of DOM (Document Object Model). 
     CSS parser verifies and parses CSS style sheet grammar and builds @rules and style rule sets list. CSS parser receives inline style information from XHTML parser or external CSS style sheet indicated by XHTML parser&#39;s style sheet link information. 
     # XHTML/CSS Layout Manager 
     XHTML/CSS Layout Manager generates layout information, which includes box dimension and position of it, by means of DOM-tree from XHTML+SMIL/CSS Parser. 
     # ECMAScript Interpreter &amp; DOM manipulator 
     ECMAScript interpreter verifies and parses ECMAScript and executes codes indicated by parsed one. 
     DOM manipulator parses DOM-tree with style information from XHTML+SMIL/CSS Parser, and DOM manipulator registers events defined in this specification. ENAV event from DVD-Video playback engine or user interaction via ENAV Interface Handler is notified to ECMAScript Interpreter &amp; DOM manipulator. Then the registered event handler is called. 
     An event takes role of a trigger for activating ECMAScript functions controlling objects, which is called as ENAV command. Meanwhile, ECMAScript Interpreter &amp; DOM manipulator knows DVD-Video playback status by reading values in Property Buffer of ENAV Interface Handler via ENAV property. 
     # SMIL Timing Engine 
     SMIL Timing Engine verifies and parses SMIL tags in XHTML document for control of SVG animation. Then SMIL Timing Engine provide timing and synchronization information for display of SVG animation. 
     # ENAV Interface Handler 
     ENAV Interface Handler has functionalities of translation from/to DVD-Video playback engine to/from ECMAScript Interpreter or SMIL Timing Engine as follows. Also, ENAV Interface Handler receives user trigger and translates each event for ECMAScript Interpreter and DOM manipulator. 
     “DVD trigger” from DVD-Video playback engine or “User trigger” from User Interaction is translated to “ENAV event”. 
     “DVD status” from DVD-Video playback engine is translated to “ENAV property”. The DVD status information is stored in Property Buffer in ENAV Interface Handler. 
     According to “ENAV command”, ENAV Interface Handler controls DVD-Video playback engine, Element Decoders, AV Renderer and Buffer Manager. 
     “ENAV control” from SMIL Timing Engine is translated to “DVD control” 
     # Element Decoder 
     Element Decoders decodes Audio, Image, Animation and Text/Font data, which are controlled by ECMAScript Interpreter &amp; DOM manipulator and SMIL Timing Engine via Element control. All elements except audio data synchronized with DVD-Video refer ENAV timing information provided by ENAV System Clock, but synchronized audio data refers DVD timing information provided by ENAV Interface Handler. 
     # AV Renderer 
     AV Renderer renders XHTML document and decoded ENAV elements from Element Decoder with layout information from XHTML/CSS Layout Manager. That is, AV Renderer has functionality to convert pixel aspect ratio of ENAV element, to re-size the ENAV element and to layout ENAV elements, according to the layout information. As for audio, AV Renderer mixes (or switches) ENAV audio with the audio in DVD-Video content. 
     Also, AV Renderer switches Screen Display between Full Screen Display and Mixed Screen Display in Enhanced Navigation Mode, according to AV output control from ENAV Interface Handler. 
     # Buffer Manager 
     Buffer Manager manages ENAV content in ENAV Buffer according to Buffer control from ENAV Interface Handler. For instance, Buffer Manager loads or discards ENAV content on both a disc and a server to/from the buffer. The information for buffer management is described in XHTML document or other file as download information. 
     # Network Manager 
     Network Manager has a function to control connection/disconnection to network, and also to measure bandwidth and response time from a server. 
     [Event Generation] 
     As an example, in the system model, an event from DVD-Video playback is executed in following process. 
     1. DVD-Video playback engine outputs “DVD trigger” to ENAV Interface Handler when an event happens. 
     2. ENAV Interface Handler reads status information of DVD-Video playback engine in response to the “DVD trigger”, if ENAV Interface Handler needs the status value for “DVD trigger”. 
     3. ENAV Interface Handler stores the associated value. 
     4. ENAV Interface Handler outputs “ENAV event” with the associated value. 
     [Reading Status] 
     As an example, in the system model, reading property is executed in following process. 
     1. DVD-Video playback engine inform status information (“DVD status”) to Property Buffer in ENAV Interface Handler when status changes and keep latest status information in the buffer. Regarding how much size is necessary for the buffer, how long the status information is stored and when the status information is updated. 
     2. ECMAScript Interpreter/SMIL Timing Engine requests status information to ENAV Interface Handler. 
     3. ENAV Interface Handler returns status information to ECMAScript Interpreter/SMIL Timing Engine. (“ENAV property”) 
     [Command Execution] 
     As an example, in the system model, a command is executed in following process: 
     1. ECMAScript Interpreter outputs ENAV command to ENAV Interface Handler. (“ENAV command”) 
     2. ENAV Interface Handler outputs DVD control to DVD-Video playback engine. (“DVD control”) 
     3. DVD-Video playback engine returns the associated value to ENAV Interface Handler in response to DVD control. 
     4. ENAV Interface Handler returns the associated value to ECMAScript Interpreter. 
     Summary of Embodiments 
     As a mechanism that maintains compatibility to the existing DVD-Video standard allows a wide variety of video playback, ENAV contents  30  are recorded on disc  1  which includes the configuration according to the existing DVD-Video standard. ENAV contents  30  need not be played back by a conventional DVD-Video player according to the DVD-Video standard, but can be played back by DVD-Video player  100  according to an embodiment of the present invention (see embodiments shown in  FIGS. 30 and 31 ). 
     DVD-Video player  100  according to an embodiment of the present invention can use not only ENAV contents  30  recorded on disc  1 , but also similar ENAV contents (Web contents)  30 W that can be downloaded from the communication line such as the Internet or the like (see an embodiment shown in  FIG. 1 ). 
     AV information contained in DVD-Video contents  10  recorded on disc  1 , and that contained in ENAV contents  30  (and/or ENAV contents  30 W) can be played back in synchronism, connection, or combination with each other in accordance with a predetermined sequence (ENAV playback information described in markups or scripts) (see embodiments shown in  FIGS. 2 to 24 ). 
     In order to allow the user to freely switch playback of DVD-Video contents  10  and/or that of ENAV contents  30  (Web contents  30 W), off-line mode (a mode for playing back DVD-Video intact) M 1 , on-line mode (a mode for playing back more interactive video via a communication by means of the Internet or the like) M 2 , and mixed mode (a mode that can attain more interactive playback using the Internet or the like while playing back DVD-Video) M 3  of the on-line and off-line modes, can be used as needed (see embodiments of  FIGS. 25 to 28 ). 
     Mode transition can be automatically made among a plurality of modes, i.e., on-line mode M 1 , off-line mode M 2 , and mixed mode M 3  in accordance with a predetermined rule (see an embodiment of  FIG. 29 ). 
     In DVD-Video player  100  according to an embodiment of the present invention, event generation•command/property processor  320  operates upon receiving a DVD event signal and/or DVD status signal from DVD-Video playback controller  220 . For this reason, unlike an arrangement that sends a DVD control signal from processor  320  to controller  220 , ENAV control according to playback (event/status) of the DVD disc can be implemented (see embodiments of  FIGS. 1 and 20 ). 
     According to the present invention, a wide variety of interactive features can be added to DVD-Video contents playback while assuring compatibility (at least upward compatibility) to the current DVD-Video (and/or Audio) standard (version 1.0).