(19)
`
`J
`
`
`
`Europaisches Patentamt
`European Patent Office
`Office europeen des brevets
`
`|||| ||| 1 1|| ||| ||| || ||| || || || ||| || || ||
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`(11)
`
`E P 0 8 7 2 9 8 7 A 2
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`(12)
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`EUROPEAN PATENT APPLICATION
`
`ition:
`(43) Date of publication:
`21.10.1998 Bulletin 1998/43
`
`(21) Application number: 98105893.6
`
`(22) Date of filing: 31.03.1998
`
`(51) |nt. ci.6: H04L 29/06, G06F 17/30
`
`(84) Designated Contracting States:
`AT BE CH DE DK ES Fl FR GB GR IE IT LI LU MC
`NL PT SE
`Designated Extension States:
`AL LT LV MK RO SI
`
`(71) Applicant: SONY CORPORATION
`Tokyo (JP)
`
`(72) Inventor: Seki, Yosuke
`Shinagawa-ku, Tokyo (JP)
`
`(30) Priority: 04.04.1997 J P 87067/97
`04.04.1997 JP 102465/97
`04.04. 1 997 J P 1 02466/97
`04.04.1 997 JP 87066/97
`
`(74) Representative:
`Melzer, Wolfgang, Dipl.-lng. et al
`Patentanwalte
`Mitscherlich & Partner,
`Sonnenstrasse 33
`80331 Munchen (DE)
`
`(54) Apparatus for providing information, method of providing information and computer-
`readable storage medium retaining a program for providing information
`(57) When making a request for providing informa-
`control request is sent from the WWW server 21 to a
`tion from a VOD server 11, a client uses a WWW
`server interface 23. The server interface 23 gives an
`browser 27 for accessing an HTML document including
`instruction to a server controller 22 for controlling the
`a control code for controlling the VOD server 11. If an
`VOD server 1 1 . Output data of the VOD server 1 1 (e.g.
`HTML document distributed from a WWW server 21
`AV data) is supplied to the client through a wide band-
`includes the control code, the client sends a request for
`width transmission line 1 9 different from the network 1 8.
`controlling the VOD server 11 to the WWW server 21
`via a network 18 (which may include the Internet). The
`12
`server computer
`(
`\
`s
`t
`server
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`234H
`interface ~~ *" server
`J v
`r, — '
`^
`HTML
`file
`disk ,
`
`21
`
`22-H
`
`\
`server
`controller J
`
`26-
`
`24
`
`V 17H
`VOD server
`
`19
`
`19
`
`FIG.1
`
`18
`
`client computer
`. PIO WWW1
`[controller IprowserJ
`rate
`converter! 14
`switcher •15
`
`27
`
`V3
`
`16
`
`display
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`Printed by Xerox (UK) Business Services
`2.16.3/3.4
`
`Charter Ex. 1006, Page 1
`
`

`

`1
`
`EP 0 872 987 A2
`
`2
`
`Description
`
`Background of the Invention
`
`Technical Field Pertinent to the Invention
`
`5
`
`tus for providing information and a method thereof and
`a computer-readable storage medium retaining a pro-
`gram for providing information, each for easily creating
`and customizing a user interface conforming to client's
`demands.
`
`SUMMARY OF THE INVENTION
`
`The present invention relates to an apparatus for
`providing specific information on demand and a method
`thereof and a computer-readable storage medium
`retaining a program for providing information.
`
`Prior Art
`
`A video on demand (VOD) system has been com-
`mercialized for distributing video data and audio data
`and so on from a server on a client's demand for obtain-
`ing a movie, a program, etc. In a conventional VOD sys-
`tem a client's side terminal unit uses dedicated software
`for communications with a server. The dedicated soft-
`ware provides a user interface, using a programming
`language such as the C language, which responds to
`demands of a client input at a client's side terminal unit.
`Furthermore the dedicated software is designed to con-
`form to sections for communicating with server control
`software.
`The VOD system may be used by various clients
`including a museum, a showroom, a small theater and a
`shop. It is therefore required to provide a client's side
`terminal unit with a user interface specifically designed
`for each user. Each user interface may dynamically
`change with time and seasons or with an exhibition at a
`museum and so on.
`However, customization of each user interface is
`not easily achieved for responding to each customer's
`demands in the method using the dedicated software in
`the client's side terminal unit for communications with
`the server. It is therefore difficult for the conventional
`VOD system to deal with frequent changes of a user
`interface and to support various clients with different
`specifications.
`Another problem of the VOD system for use by var-
`ious clients is the difficulty in creating a renewed user
`interface conforming to the client's demands. That is, for
`introducing the VOD system, it is required to newly cre-
`ate a means for communications between a client's side
`terminal unit and a server in a physical form as well as
`in a form of software. On the server's side, server con-
`trol software dedicated to the VOD system is required
`for controlling the server. On the other hand, it is
`required for the client's side terminal unit to communi-
`cate with the server control software on the server's
`side through client software operating on the terminal
`unit for requesting the server control software for repro-
`ducing image data or audio data and so on.
`Although a VOD system has been described so far,
`the foregoing problems apply to any system for provid-
`ing information on a client's demand.
`It is an object of the invention to provide an appara-
`
`10
`
`15
`
`20
`
`25
`
`An apparatus of the invention for providing informa-
`tion comprises a means for receiving a demand for pro-
`viding information from a client through a network, using
`a world wide web as a system for providing a link to
`information on an Internet, and a means for sending
`information to the client through a transmission line dif-
`ferent from the network in response to the demand for
`providing information from the client received by the
`means for receiving a demand.
`A method of the invention for providing information
`comprises the steps of receiving a demand for providing
`information from a client through a network, using the
`world wide web as a system for providing a link to infor-
`mation on the Internet, and sending information to the
`client through a transmission line different from the net-
`work in response to the received demand for providing
`information from the client.
`A computer-readable storage medium according to
`the invention stores a program for providing information
`which allows a computer to implement a function of
`receiving a demand for providing information from a cli-
`30 ent through a network, using the world wide web as a
`system for providing a link to information on the Internet,
`and a function of sending information to the client
`through a transmission line different from the network in
`response to the demand for providing information from
`the client received by the function of receiving a
`demand.
`
`35
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`40
`
`45
`
`Fig. 1 is a block diagram illustrating a main part of a
`VOD system including an information providing appara-
`tus of an embodiment of the invention.
`Fig. 2 is a block diagram illustrating an overall con-
`figuration of the VOD system of the embodiment of the
`invention.
`Fig. 3 is a block diagram illustrating an example of a
`computer used as a server computer and a client com-
`puter in Fig. 1 .
`Fig. 4 is a block diagram illustrating an example of a
`so VOD server in Fig. 1 .
`Fig. 5 is a table for showing an example of a rela-
`tionship table stored in the server computer in Fig. 1 .
`Fig. 6 is a chart for illustrating an operation of the
`VOD system of the embodiment of the invention.
`Fig. 7 illustrates a relationship between a frame out-
`putted from the client computer and a frame shown on a
`display.
`Fig. 8 illustrates the VOD system of the embodi-
`
`55
`
`2
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`Charter Ex. 1006, Page 2
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`

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`3
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`EP 0 872 987 A2
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`4
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`ment connected to an external Internet.
`Fig. 9 illustrates the client computer of the embodi-
`ment connected to a plurality of server computers for
`VOD server control.
`Fig. 10 illustrates an example of a CATV system.
`Fig. 1 1 is a block diagram illustrating a modification
`of the VOD server of the embodiment of the invention.
`Fig. 12 illustrates an application of the invention to
`an auto-changer system using disk players.
`Fig. 13 illustrates an application of the invention to 10
`10
`an auto-changer system using video cassette record-
`ers.
`
`s
`
`Detailed Description of Certain Preferred Embodi-
`ments
`
`15
`
`A preferred embodiment of the invention will now be
`described in detail with reference to the accompanying
`drawings.
`Fig. 1 is a block diagram illustrating a main part of a 20
`VOD system including an apparatus for providing infor-
`mation of an embodiment of the invention. The VOD
`system is a system for providing specific video informa-
`tion and audio information through a plurality of chan-
`nels on demands of a plurality of clients for providing 25
`information. The VOD system comprises: a VOD server
`1 1 for storing information to be provided for clients and
`sending out a specific piece of information in response
`to instructions; a server computer 12 for controlling the
`VOD server 11; a client computer 13 for sending a 30
`request for providing information to the server computer
`12; a rate converter 14 for converting video signals out-
`putted from the client computer 13 into video signals for
`display on a display 16; a switcher 15 for switching
`between video signals sent from the VOD server 1 1 via 35
`a high bandwidth, independent link 19 and video signals
`outputted from the rate converter 14 for output to the
`display 1 6 for displaying a video image. The apparatus
`for providing information of the embodiment is made up
`of the VOD server 1 1 and the server computer 1 2.
`The VOD server 1 1 has output channels for a plu-
`rality of video data and audio data (referred to as AV
`data in the following description). The VOD server 11
`and the server computer 12 are connected to each
`other through a serial transmission line 17 utilizing a 45
`serial interface such as an RS232C. The server compu-
`ter 1 2 and the client computer 1 3 are connected to each
`other through a network 18, such as an Internet, using
`an Ethernet, for example. Although the one client com-
`puter 13 is shown in Fig. 1 , a plurality of client comput-
`ers 13 each receiving information from the VOD server
`1 1 are connectable to the network 1 8 and a separate
`channel or link 19. Each switcher 15 corresponding to
`one of the client computers 13 is connected to one of
`the plurality of output channels of the VOD server 1 1 55
`through the separate transmission line 19.
`In the embodiment the VOD server 11 and the
`server computer 12 are called a server's side. The client
`
`40
`
`so
`
`computer 13, the rate converter 14, the switcher 15 and
`the display 16 are called a client's side.
`The server computer 12 comprises: a world wide
`web (WWW) server 21 for management and distribution
`and so on of information carried on the Internet using a
`WWW as a system for allowing a link to information on
`the Internet; a server controller 22 for controlling the
`VOD server 1 1 by giving a command to the VOD server
`11 through the serial transmission line 17; a server
`interface 23 for interfacing between the WWW server 21
`and the server controller 22; and a hypertext markup
`language (HTML) file disk 24 for storing an HTML docu-
`ment written in the HTML as a hypertext language. The
`HTML file disk 24 is accessible from either the WWW
`server 21 or the server controller 22. The WWW server
`21, the server controller 22 and the server interface 23
`are each implemented by reloadable software (pro-
`grams). The HTML file disk 24 is implemented by a hard
`disk in the server computer 12.
`The server computer 12 shown in Fig. 1 corre-
`sponds to a means for receiving a demand (a function of
`receiving a demand), a means for generating informa-
`tion indicating sending (a function of generating infor-
`mation indicating sending) and a means for sending a
`program (a function of sending a program). The VOD
`server 1 1 corresponds to a means for sending informa-
`tion (a function for sending information).
`The server computer 1 2 uses Windows NT® (a reg-
`istered trademark of Microsoft Corporation), for exam-
`ple, for an operating system. The WWW server 21 is
`implemented through installing software such as Micro-
`soft-Internet information server (IIS™, a trademark of
`Microsoft Corporation). The server interface 23 is, for
`example, implemented by software designed in compli-
`ance with an Internet server application programming
`interface (ISAPI) as additional software for providing
`extensions for the WWW server implemented by the IIS.
`The client computer 13 comprises: a parallel
`input/output (PIO) controller 26 for controlling parallel
`inputs and outputs and a WWW browser 27 for access-
`ing a WWW server on the Internet using the WWW. A
`suitable browser might be the commercially available
`Internet Explorer™ (a trademark of Microsoft Corpora-
`tion) or Netscape Navigator® (a registered trademark of
`Netscape Communications Corporation). The PIO con-
`troller 26 and the WWW browser 27 are each imple-
`mented by software (a program). The PIO controller 26
`has a function of controlling the switcher 15 at com-
`mands from the WWW server 21 .
`HTML documents are stored on the HTML file disk
`24 in the server computer 12. The HTML documents
`include control codes for implementing a user interface
`using the WWW browser 27. The control codes
`included in the HTML documents include control codes
`for controlling the VOD server 1 1 . The WWW browser
`27 sends a request via the network 1 8 for controlling the
`VOD server 1 1 to the WWW server 21 when a control
`code for controlling the VOD server 1 1 is included in an
`
`3
`
`Charter Ex. 1006, Page 3
`
`

`

`5
`
`EP 0 872 987 A2
`
`6
`
`is
`
`HTML document distributed via the network 1 8 from the
`WWW server 21 . The control request is sent from the
`WWW server 21 to the server interface 23. The server
`interface 23 gives an instruction to the server controller
`22 for executing control at the control request. On 5
`receiving the instruction, the server controller 22 gives a
`command to the VOD server 1 1 through the serial trans-
`mission line 1 7 to control the VOD server 1 1 .
`The server controller 22 has data of a table indicat-
`ing a relationship between the output channels and 10
`Internet addresses (IP addresses), that is, addresses
`on the network 18 of the plurality of client computers 13.
`Fig. 5 shows an example of such a relationship table.
`The relationship table is made by an administrator of the
`VOD system. When the client computer 13 makes a
`request for providing information, the server controller
`22 refers to the relationship table to determine the out-
`put channel corresponding to the Internet address of
`the client computer 13 that made the request. The
`server controller 22 then controls the VOD server 1 1 so 20
`that the requested information is sent through the corre-
`sponding separate link 19 to the client computer 13 that
`made the request for providing the information.
`Fig. 2 is a block diagram illustrating an overall con-
`figuration of the VOD system of the embodiment. The 25
`VOD system shown comprises: the server computer 12
`connected to the network 1 8; the VOD server 1 1 whose
`operation is controlled by the server computer 12; and
`four terminal units 31 to 34 of the client's side each con-
`nected to the network 18. In this example the VOD 30
`server 11 has six output channels ch1 to ch6 for AV
`data. The terminal units 31 to 34 receive AV data from
`the respective output channels ch1 to ch4 of the VOD
`server 11 via the separate links 19. In Fig. 2 V and A
`each represent video data and audio data, respectively. 35
`The terminal unit 31 has a configuration similar to
`that of the client's side in Fig. 1. The terminal unit 31
`comprises: a client computer 13 connected to the net-
`work 1 8; a rate converter 1 4 for converting video signals
`outputted from the client computer 1 3 into video signals 40
`for display on a display 1 6; a switcher 1 5 for switching
`between video signals sent from the VOD server 1 1 and
`video signals outputted from the rate converter 14 for
`output; and a display 16 for receiving video signals out-
`putted from the switcher 15 and displaying a video 45
`image. Besides switching video signals, the switcher 15
`in this example further has a function of switching
`between audio signals sent from the VOD server 1 1 and
`audio signals outputted from the client computer 13.
`The terminal unit 31 further comprises active speakers
`36 and headphones 37 for receiving audio signals out-
`putted from the switcher 15 for audio output; and a
`trackball 38 connected to the client computer 13. In the
`example the client computer 13 has a function of receiv-
`ing video signals from an external source for manipula-
`tion. Video signals sent from the VOD server 11 are
`inputted to the client computer 13 as well.
`The terminal unit 32 comprises two head-mount
`
`so
`
`ss
`
`displays 39 instead of the display 1 6, the active speak-
`ers 36 and the headphones 37 in the terminal unit 31.
`The head-mount displays 39 each incorporate speakers
`and receive video and audio signals outputted from the
`switcher 1 5 for image display and audio output.
`The terminal unit 33 comprises: a client computer
`13 connected to the network 18; a touch monitor 41 for
`displaying video signals outputted from the client com-
`puter 13 and for functioning as a touch panel used for
`giving instructions to the client computer 13; active
`speakers 42 and headphones 43 for receiving audio sig-
`nals outputted from the VOD server 1 1 and audio sig-
`nals outputted from the client computer 13 for audio
`output. The client computer 13 in the terminal unit 33
`has a function of receiving video signals from an exter-
`nal source for manipulation. Video signals sent from the
`VOD server 1 1 are inputted to the client computer 1 3 as
`well. The client computer 13 further has a function for
`overlaying an image made of video signals sent from
`the VOD server 1 1 on a frame created by the client com-
`puter 13 on the touch monitor 41. Another function of
`the client computer 13 is controlling the overlay display
`at commands from the WWW server 21 .
`The terminal unit 34 comprises: a client computer
`1 3 connected to the network 1 8; a touch panel 44 for
`displaying video signals outputted from the client com-
`puter 13 and for giving instructions to the client compu-
`ter 13; a display 45 for receiving video signals sent from
`the VOD server 11 for video image display; and an
`audio system 46 for receiving audio signals outputted
`from the VOD server 1 1 for audio output.
`Fig. 3 is a block diagram illustrating an example of a
`computer used as the server computer 12 and the client
`computer 13 in Fig. 1. The computer comprises: a cen-
`tral processing unit (CPU) 51 ; read only memory (ROM)
`52; random access memory (RAM) 53; an interface
`(shown as in l/F in the Figure) 54 for a display; an inter-
`face 60 for connection with the network 1 8; and a bus 50
`for connecting the constituents. The computer further
`comprises: a hard disk 62; a CD-ROM drive 63; a floppy
`disk drive 64; a keyboard 65; and a mouse 66, each
`connected to the bus 50 through separate interfaces 55
`to 59, respectively.
`In the computer shown in Fig. 3, the CPU 51 exe-
`cutes an application program stored in any of the hard
`disk 62, a CD-ROM driven by the CD-ROM drive 63 and
`a floppy disk driven by the floppy disk drive 64, with the
`RAM 53 as a work area. In the server computer 12, a
`program for implementing the WWW server 21, the
`server controller 22 and the server interface 23 corre-
`sponds to a program for sending information of the
`embodiment. Consequently, a CD-ROM or a floppy disk
`corresponds to a computer-readable storage medium
`retaining a program for sending information when a pro-
`gram for implementing the WWW server 21 , the server
`controller 22 and the server interface 23 in the server
`computer 12 is stored on either the CD-ROM driven by
`the CD-ROM drive 63 or the floppy disk driven by the
`
`4
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`Charter Ex. 1006, Page 4
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`EP 0 872 987 A2
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`8
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`floppy disk drive 64 and the program stored thereon is
`then installed on the hard disk 62.
`Fig. 4 is a block diagram illustrating an example of
`the VOD server in Fig. 1 . The VOD server 1 1 shown
`comprises a storage section 71 and a control section
`72. The storage section 71 has a plurality of hard disk
`drives (HDDs) 73 each for driving a hard disk. AV data
`to be provided for a client is stored on a hard disk driven
`by each HDD 73.
`The control section 72 has: a main CPU 74; a HDD 10
`interface (shown as HDD l/F) 75; AV data output sec-
`tions 76 for every output channel connected to a sepa-
`rate link 19; and an internal bus 77 for interconnecting
`the constituents. The HDD interface 75 is connected to
`the HDDs 73 in the storage section 71 . Each AV data
`output section 76 outputs AV data retrieved from the
`hard disk in the storage section 71 through the HDD
`interface 75 to a transmission line 19 in Fig. 1 through a
`corresponding channel 76. The main CPU 74 has a
`communication section 78 for communicating with the 20
`server computer 12 through the serial transmission line
`1 7 in Fig. 1 and an AV data interface (shown as AV data
`l/F) 79 for receiving AV data to be stored in the storage
`section 71 from an encoder not shown. The communi-
`cation section 78 and the AV data interface 79 are 25
`implemented through software. The main CPU 74
`receives commands sent from the server computer 1 2
`through the serial transmission line 17 at the communi-
`cation section 78. In accordance with the commands
`the main CPU 74 controls the HDD 73 in the storage 30
`section 71 for retrieving desired AV data. The retrieved
`AV data is then outputted through the AV data output
`section 76 in accordance with the commands.
`The operations of the VOD system shown in Fig. 1
`will now be described, including operations of the VOD 35
`server 1 1 and the server computer 1 2 as an apparatus
`for providing information of the embodiment. The follow-
`ing description serves for a method of providing infor-
`mation of the embodiment and a program for providing
`information stored in a computer-readable storage 40
`medium of the embodiment as well.
`As previously mentioned, the HTML file disk 24 in
`the server computer 1 2 stores HTML documents includ-
`ing control codes for implementing a user interface
`using the WWW browser 27. The control codes 45
`included in the HTML documents include control codes
`for controlling the VOD server 1 1 . When a request is
`made on the client's side for control of the VOD server
`1 1 , such as a request for providing information, that is,
`for replaying AV data, the WWW browser 27 is used for
`accessing the HTML document including a control code
`for controlling the VOD server 11. The WWW browser
`27 gives a request for controlling the VOD server 1 1 to
`the WWW server 21 when control codes for controlling
`the VOD server 1 1 are included in an HTML document
`distributed from the WWW server 21. The control
`request is sent from the WWW server 21 in the server
`computer 12 to the server interface 23. The server inter-
`
`so
`
`ss
`
`5
`
`face 23 gives an instruction to the server controller 22
`for executing control at the control request. On receiving
`the instruction the server controller 22 gives commands
`to the VOD server 1 1 through the serial transmission
`line 17 to control the VOD server 1 1 .
`A specific example will now be given for the control
`code for controlling the VOD server 1 1 included in an
`HTML document. In general, addition of application
`software to the WWW server 21 allows translation of an
`HTML document and a database search and so on.
`Using this function the embodiment of the invention
`achieves communications with the server controller 22
`for controlling the VOD server 1 1 , instead of performing
`translation of an HTML document and so on. Therefore
`a general-purpose code is used for the control code
`added to an HTML document. For example, the follow-
`ing code is used in practice for controlling the VOD
`server 1 1 using an HTML document:
`
`(HTML)
`(BODY)
`(A
`HREF=http://www.addres/script/dll/VSRSI.dll?play
`?1&/home/play 1.html) Play Clip 1 </A)
`(/BODY)
`(/HTML)
`
`In the above code, "Play Clip 1" is indicated on the
`display 16 on the client's side to which the HTML docu-
`ment is distributed including the above code. If "Play
`Clip 1" is selected (or clicked, for example) on a frame
`shown on the display 16 on the client's side, the WWW
`browser 27 sends the URL address:
`"http://www.addres/scrips/dll/VSRSI.dll?play?1&/home/
`play1.html" in the code to the WWW server 21.
`"VSRSI.dll?play?1 &/home/play1 .html" is a command for
`starting up software implementing the server interface
`23. VSRSI is a name of the software implementing the
`server interface 23. The address and directory of the
`"VSRSI.dll"
`is
`located
`is
`server where
`"http://www.addres/script/dll". The server interface 23 is
`thus
`started
`and
`In
`the
`code
`operated.
`"play?1&/home/play1.html" is a parameter for control-
`ling the VOD server 1 1 , such as a number of a clip (an
`AV program). In the example clip number 1 is desig-
`nated
`for
`Furthermore
`replay.
`a
`homepage
`(7home/play1 .html") is designated to be displayed dur-
`ing replay of the clip.
`The server interface 23 started as described above
`also sends the Internet address of the client computer
`13 having made the request to the server controller 22
`in addition to the parameter. The server controller 22
`analyzes the parameter and gives a command to the
`VOD server 1 1 through the transmission line 1 7 for con-
`trolling the VOD server 1 1 . The server controller 22 des-
`ignates the output channel corresponding to the
`Internet address, referring to the table indicating the
`relationship between the Internet addresses and the
`
`Charter Ex. 1006, Page 5
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`output channels. When the server controller 22 gives
`the VOD server 1 1 a command for a time-consuming
`operation such as a replay of an image, the server con-
`troller 22 creates a virtual image file (referred to as a vir-
`tual image in the following description) in an HTML 5
`directory in the HTML file disk 24 under control of the
`WWW server 21 if the command is correctly received by
`the VOD server 1 1 . The virtual image indicates that the
`replay is under way. The server controller 22 informs the
`client computer 1 3 of the start of the replay and the ter- w
`mination of the replay request as well. If necessary,
`commands for switching video signals, such as switch-
`ing of the switcher 15 and control of an overlay display,
`are sent to the client computer 13. The virtual image is
`created for each client.
`The server controller 22 periodically detects
`whether replay is terminated at the VOD server 11
`through sensing a status of the VOD server 1 1 . When a
`15-minute clip is replayed, for example, intermittent
`detection is performed for 15 minutes. On detection of 20
`termination of replay, the server controller 22 deletes
`the virtual image. If a viewer requests that the replay be
`stopped, the server controller 22 controls the VOD
`server 11 so that the replay is stopped as well as
`deletes the virtual image.
`On receiving the start of replay, the client computer
`13 controls switching of video signals, if necessary, in
`accordance with the command. The client computer 13
`then periodically accesses the virtual image in the
`server computer 12 through the use of the WWW 30
`browser 27. When the virtual image is deleted, the client
`computer 13 determines that the replay is terminated
`and controls switching of video signals, if necessary, to
`display a frame provided from the client computer 1 3 on
`the display 16.
`For allowing periodical access of the client compu-
`ter 1 3 to the virtual image, a Java™ applet (Java™ is a
`trademark of Sun Microsystems, Inc.), a small program
`written in the Java™ language is used, for example.
`Specifically, an applet may be included in an HTML doc- 40
`ument sent from the WWW server 21 to the WWW
`browser 27 so that the WWW browser 27 calls the
`applet out of the HTML document for execution. The
`applet periodically accesses the virtual image and
`determines that a replay