Storage medium unit controlled by downloaded programs

A storage medium unit is used as a part of a system for providing information-on-demanding service. The storage medium unit has a storage device for storing information data including video data and/or audio data to be retrieved therefrom and transmitted to end user devices of the information-on-demand service, a memory controller for controlling the storage device, and a memory device for storing software program. The software program is downloaded from a system manager of said system into said memory device. The memory controller controls operation of the storage device according to the downloaded software program.

Conventional cable tv systems deliver video data from a distribution
 company through a cable to a number of monitors of viewers. Although
 nowadays many programs are distributed through many channels by each cable
 tv company, the user or viewer has to wait until the desired program is
 started and transmitted through a selected channel.
 Recently, also interactive video systems have been proposed. In such
 interactive video systems a viewer can choose a desired movie to be
 displayed on a monitor. In such video-on-demand system a direct connection
 to the monitor or end device of a user is established, whereafter a
 demanded movie can be viewed by the end user.
 In this known system it is however virtually impossible to upscale the
 system after it has been established e.g. at a distribution company. When
 the number of members for such a system increases and the number of
 demanded videos is increased, a new interactive video system has to be
 built.
 The present invention provides a storage medium unit, comprising:
 storage means for storing information data;
 control means for controlling the storage means;
 memory means for memorizing program-data-, said memory means and/or storage
 medium unit being connected to a service system in such a way that program
 data are downloaded in said memory means by said service system,
 wherein said control means control operation of the storage means according
 to said down-loaded program data.
 The storage medium unit according to the present invention makes it
 possible to upscale the system by connecting one or more additional
 storage medium units to the system. The interface provides for
 standardization of the information data and routing information in the
 form of one or more packets, so that the storage means of the storage
 medium unit according to the present invention may comprise all sorts of
 storage media, such as one or more hard discs, one or more magnetical
 optical discs, video tapes and/or other media.
 Preferably said program data are down-loaded from the interactive system,
 so that only a minimum amount of software has to be included in the
 storage medium unit.
 Preferably said information data are video and/or audio data although the
 present invention is not limited to this application. The storage medium
 unit according to the present invention may also comprise application for
 video games, library function and databanks, although first promising
 application fields relates to video-on-demand services.
 Preferably said interface comprises an ATM interface. The basics and
 standards of ATM (Asynchronous Transfer Mode) are laid down in
 recommendations I.150 and I.327 as published in March 1993 by the
 International Telecommunication Union). ATM is generally used for
 addressing a specific packet-oriented transfer mode which uses
 asynchronous time division multiplexing techniques. The multiplexed
 information flow is organized into blocks of fixed size called cells. A
 cell consists of an information filed and a header. The primary role of
 the header is to identify cells belonging to the same virtual channel
 within the asynchronous time division multiplex.
 Preferably the storage medium unit according to the present invention
 provides for still mode operation, fast forward mode operation, reverse
 mode operation and mosaic mode operation as in a video cassette recorder
 (VCR).

The following description in which reference is made to the figures,
 describes a combination of hardware and software; it should be understood
 that some hardware components may be combined into a single hardware
 component such as a CPU where functions are time multiplexed. It should
 also be understood that connections between logic (software) units can be
 more complex than is shown schematically in the figures.
 FIG. 1 shows an entire configuration of a preferred embodiment of an
 interactive communication system according to the present invention,
 comprising,: an ATM switch 1 (as example only: ForeRunner.TM. ASX-200 of
 Fore Systems Inc., Warrendale, Pa., USA); storage medium units 20 (SMU);
 end devices 40; a system manager 60 and navigation devices 30. ATM switch
 1 connects the storage medium units 20, the end devices 40, the system
 manager 60 and the navigation devices 30 to each other, selectively, by
 using virtual channel connections and data is transferred to and from
 these components in a form of ATM packets consisting of a 5 byte cell
 header including routing information and a 48 byte information field
 through ATM user/network interfaces provided between each device and ATM
 switch 1. ATM switch 1 has a conversion table of routing information such
 as Virtual Channel Identifier and by changing the routing information of
 each incoming ATM packet to the routing information designating the output
 virtual channel, the ATM packet can be transferred to the correct
 destination. ATM switches are known and further explanation is omitted
 here.
 The interactive communication system will be explained below, specifically
 referring to the embodiment, where video-on-demand (VOD) service is
 supplied to users. It should, however, be noted here that other
 applications, such as teleshopping, games and other types of information
 exchange, are equally possible. Such services can be referred to as
 information-on-demand services in general.
 In the interactive communication system shown in FIG. 1 video signals
 and/or audio signals are stored in SMU's 20. Several embodiments of a SMU
 20 will be described below in detail.
 In FIG. 1 end devices 40 are set top boxes, each of which can communicate
 with the navigation devices 30, the system manager 60 and can decode video
 data. (preferably compressed according to the MPEG-2 standard) and/or
 audio data from a SMU 20, and supply decoded video signal and/or audio
 signal to a monitor 43 and/or a speaker system 42. Each set top box or end
 device 40 has an input device 44, for example a keyboard or remote
 control, connected thereto. Preferably a set top box is provided with a
 graphical processor unit 49 for generating graphical data to monitor 43 to
 facilitate interaction with the user. Preferably the data for the
 graphical processing unit is supplied by the system manager through the
 ATM packets. A viewer can input instructions through the keyboard 44 or
 other suitable input device through the set top box 40. An embodiment of a
 set top box 40 will be described below in detail.
 Navigation devices 30 can provide information on available video programs
 to any one of the set top boxes 40. Such information can be represented on
 the monitor 43 of the set top box 40 in a graphical way or by text, or by
 a combination thereof. Available video programs are video programs which
 can be selected by a viewer. Such requestable information will hereinafter
 be referred to as service items. An embodiment of a navigation device 30
 is described below in more detail.
 The system manager 60 manages operation of the interactive communication
 system by managing the operation of the ATM switch 1. An embodiment of the
 system manager 60 will be described below in more detail.
 A major feature of an interactive communication system according to this
 preferred embodiment of the present invention is, that there are no
 restrictions on the hardware used or the operating system installed. Each
 set of communication operations is preceded by transmission of a control
 software program dedicated to such set of operations to a receiving and/or
 transmitting component, so that the receiving and/or transmitting
 component can optimally handle the incoming and/or outgoing communication
 following this down-load of said control software program.
 In the embodiment of FIG. 1, at least one of the SMU's 20 is an archive
 SMU. In this embodiment the other SMU's 20 are delivery SMU's. The archive
 SMU stores many kinds of control software programs, video data and/or
 audio data. An archive SMU may comprise as memory means a tape or MO disc,
 while a delivery SMU preferably comprises an agile hard disc or MO disc as
 memory means. A MO disc is less agile than a hard disc but more agile than
 a tape. Each of the delivery SMU's stores separate parts of the data of
 the archive SMU. While the archive SMU may also be used as a SMU for
 delivery purposes, the delivery SMU's are used for VOD service. The system
 manager 60 downloads control software program to the archive SMU and the
 delivery SMU for a copy operation from the archive SMU to one of the
 delivery SMU's at the beginning of or in advance of a video on demand
 service. The installation of a delivery SMU by the archive SMU is shown in
 more detail in FIG. 18. The delivery SMU stores necessary video data from
 the archive SMU according to a command for the copy operation from the
 system manager 60, and in particular from the storage medium manager 62.
 When the system manager 60 receives the demand data from an end device 40,
 the system manager 60 outputs to the ATM switch 1 distribution control
 data including information of virtual channels for the selected video data
 produced from the received demand data and an address of the end device
 40. Next, the delivery SMU outputs the selected video data with the
 routing information for this end device 40. A software program for
 write-in operation is down-loaded from the system manager 60 to the RAM 24
 of the SMU 20 before copy operation of the video data is performed. The
 CPU 22 of the SMU 20 controls write-in operation of the physical storage
 medium, 21 according to the software program for write-in operation stored
 in the RAM 24. Then the software program for write-in operation in the RAM
 24 is replaced with a software program for read-out operation by down-load
 from the system manager 60 before video service starts. The CPU 22
 controls read-out operation of the physical storage medium 21 according to
 the software program for read-out operation in video service.
 The interactive communication system preferably comprises a plurality of
 (delivery) SMU's. In the system, the necessary video and/or audio data of
 a particular video and/or audio program is only copied from the archive
 SMU to one of the delivery SMU's, if the number of end devices 40 with the
 possibility to select the particular video and/or audio program is smaller
 than a predetermined number. On the other hand, the necessary video and/or
 audio data is also copied from the archive SMU or from the above delivery
 SMU to one or more of the other delivery SMU's, if more than the
 predetermined number of end devices have the possibility to select the
 particular video or audio program. The predetermined number can be
 determined based on certain statistics or real time monitoring of the
 number of end devices 40 requesting the particular video and/or audio
 program at a specific point in time.
 The preferred embodiment of the present invention provides for the
 possibility that the number of end users is monitored in run time and that
 the configuration will dynamically change to prevent the system from
 overloading. When the number of end users increases, a new delivery SMU
 can be loaded from the archive SMU or another delivery SMU.
 The system manager 60 preferably outputs backup control data, for the
 situation in which one of the-delivery SMU's malfunctions. Selected video
 and/or audio data is then output by another delivery SMU, which is not
 malfunctioning and is selected according to said backup control data. The
 conversion table of virtual channels in the ATM switch 1 is updated by the
 system manager 60 so that the input virtual channel of a possibly
 malfunctioning delivery SMU is changed to the virtual channel of another
 delivery SMU to provide the same video and/or audio data from the second
 SMU.
 A user selects the desired navigation service and connects the end device
 40 to a navigation device 30 providing the desired navigation service.
 Navigation data including a software program for displaying a menu of
 service items and identification data corresponding to each service item
 is downloaded preferably beforehand from at least one navigation device 30
 selected by the end device 40. The monitor 43 of end device 40 displays
 such a menu of the available service items and, if necessary,
 corresponding identification data thereof. A menu from navigation device
 may comprise video and/or audio information and control data, either in
 graphical form, textual format or a combination thereof, to facilitate the
 choice for the end user.
 If a user selects a video and/or audio program through the input device 44
 from the menu by pointing the desired video program with a pointer in the
 monitor 43 or by entering the identification data corresponding to the
 desired program, if displayed on the monitor 43, the identification data
 is supplied to the system manager 60 by the end device 40 via ATM switch
 1. Such identification data may be a public address in case that the
 system manager 60 is connected to public ATM network. The navigation data
 may further include video data obtained from SMU 20 or navigation device
 30. The navigation data down-loaded from a navigation device 30 can also
 contain information on other selectable navigation devices 30.
 In a not shown embodiment an end device 40 can be connected to a navigation
 device through a public ATM switch, in which case such a navigation device
 can be selected through a public address. Through such a public navigation
 device it would also be possible to choose other navigation devices via
 the first publication navigation device.
 The system manager 60 down-loads a VOD-software program for end devices 40
 corresponding to a selected video program to the end device 40, after the
 system manager 60 receives identification data from the set top box 40.
 The system manager 60 also downloads a VOD-software program for the SMU's
 20 corresponding to the selected video program to the SMU 20 via the ATM
 switch 1, before VOD service starts. The system manager 60 selects the SMU
 20 and the most appropriate service items according to data representing
 video program allocation, for example in the form of a table, in the SMU's
 20 and provides distribution control data including the information of the
 channel and the routing information corresponding to the selected video
 program to the selected SMU 20 so that the SMU 20 operates to reproduce
 the selected video program.
 A controller 26 in the SMU 20 controls the physical storage medium 21, so
 that the physical storage medium 21 reproduces selected video data in a
 play mode selected by the end device 40 as described below in more detail.
 The reproduced video and/or audio data is supplied to ATM interface 29.
 As explained earlier the physical storage medium may comprise a hard disc,
 a MO disc or tape on which a video movie is recorded.
 An ATM interface 29 combines the reproduced video and/or audio data
 preferably divided into cells each containing 48 bytes with the routing
 information stored in the memory of the SMU 20 in the form of ATM packets
 and outputs the same to the ATM switch 1.
 Control data from the controller 26 such as control information for the end
 device 40 is supplied to the end device via the ATM interface 29 and the
 ATM switch 1. Control data from the end device 40 such as a required play
 mode is received through the ATM switch 1 and the ATM interface 29.
 The ATM switch 1 routes the ATM packets between the end devices 40, the
 SMU's 20 and the system manager 60 according to the routing information
 attached to the ATM packets. The conversion table of the private ATM
 switch 1 is updated by the system manager 60.
 In the not shown embodiment wherein a public ATM switch is used in
 combination with the private ATM switch, the virtual channel connection of
 the public ATM switch is established by using a public address at the
 start of the service.
 In VOD operation, an end device 40 outputs control data requesting a play
 mode, such as normal play, fast forward play, reversed play, fast reversed
 play, still picture mode or more vague mode, to the ATM switch 1 through
 an ATM interface 41 according to the mode selection on the input device 44
 by the user. The ATM switch 1 then routes the control data to the system
 manager 60. The system manager 60 outputs control data requesting the
 selected play mode to the ATM switch 1 through the ATM interface. SMU 20
 reproduces the selected video data in the selected play mode. As a
 variation, the control data requesting a play mode can be routed from the
 end device 40 directly to the SMU 20.
 In case of VCR options, the physical storage medium is preferably a hard
 disc, as such hard disc is more agile than the other mentioned physical
 storage mediums. As an alternative an MO-disk can be used, on which
 information is recorded in a staggered fashion, which will be described
 hereinafter.
 The system manager 60 functionally comprises one or more storage medium
 managers 62, a storage medium group 63 including one or more service item
 groups 64 and one or more service item providers 65, a service routing
 manager 66 and a program manager 67. Each storage medium manager 62 may
 contain static data and/or dynamic data with respect to each SMU 20 under
 its control. The static data may comprise for example type, costs or
 recording capacity of each storing medium unit 20. The dynamic data may
 for example include status information such as whether or not the SMU is
 occupied by video and/or audio data and whether or not it is being in use,
 or whether or not it is malfunctioning.
 The storage medium group 63 outputs a request for assignment of a SMU 20 to
 the storage medium manager 62 on basis of the requirements from the end
 devices 40. Such requirement can be specified by the statistical
 information, such as potential number of the end devices 40 that can
 request service in a certain time frame or length of video program. Other
 possible requirements may be whether or not any end device 40 has a
 possibility to select the more complex play mode such as mentioned above
 and including fast forward, fast reverse etc. The storage medium manager
 62 proposes a suitable SMU 20 or suitable storage medium in the SMU 20 to
 a storage medium group 63 for the video service to the end device 40,
 according to static data and/or dynamic data with respect to each SMU 20
 contained therein, e.g. table means, and the request from the storage
 medium group 63. Further, storage medium group 63 controls down-load
 operation of software programs to one of the end devices 40 in response to
 a request from this end device 40.
 In case of a plurality of storage medium managers 62, each storage medium
 manager 62 may propose a suitable SMU 20 belonging to each storage medium
 manager 62 for the video service to the storage medium group 63. A storage
 medium manager 62 will ask another storage medium manager 62 to propose a
 suitable SMU 20, requested by the storage medium group 63, if said storage
 medium manager 62 can not satisfy the request of the storage medium group
 63. More specifically, the service item providers 65 request assignment of
 one of the SMU 20 to the storage medium manager 62 via the service item
 group 65. The service item group 65 also control the down-load operation
 of control software programs originally provided from the program manager
 67, which manages all control software programs to be used in the system
 and delivers each devices updated, suitable, and effective programs.
 The service item group 65 can down-load a suitable down-loadable software
 program to the set top box according to the table therein representing
 relationship between service item identification and service item
 provider. When the request is provided from the service item provider, the
 service item group 65 can decide which down-loadable software is suitable
 for subsequent operation of the set top box according to the table in the
 service item group.
 Even if the storage medium manager 62 is malfunctioning, the malfunctioning
 storage medium manager 62 may be restored while the SMU 20 outputs video
 and/or audio data, as reproduced video and/or audio data is directly
 output to the ATM switch 1 without routing by the storage medium manager
 62.
 Next, full VCR functions, for example fast forward, reverse, fast reverse
 and still play mode will be explained. In the full VCR function, an agile
 storage medium, for example a hard disc, is used. The agile storage medium
 is installed in one or more of the SMU's. At the beginning of the video on
 demand service, the video and/or audio data of the selected video program
 or video program with possibilities of VCR functions from end device 40,
 is copied from the archive SMU or a delivery SMU to this agile storage
 medium. The agile storage medium outputs video and/or audio data in the
 play mode required by a set top box 40 under control of the system manager
 60. The system manager 60 provides for changing the virtual channel, if
 the full VCR function is requested by the end user, so that such end user
 is connected to an SMU with a hard disc enabling the full VCR function
 through the virtual channel. In the case, where an end device 40 is
 supplied with information from an MO-disc on which this information is
 recorded in a staggered fashion, and the end device for example request a
 fast forward or fast reverse play mode, a separate SMU containing an agile
 hard disc can be employed. This may be advantageous, when time will lapse
 between the request and the moment another virtual channel delivering this
 play mode becomes available. When the agile disc is employed
 intermediately, this agile hard disc can be engaged at a time pointer,
 corresponding to the time pointer of the virtual channel in use at the
 time of the request, can be speeded up or slowed down, and can
 consequently be disengaged, when the time pointer and speed of the agile
 disc correspond to that of another virtual channel delivering information
 in the selected play mode from an MO-disc containing information recorded
 in a forward or reverse staggered fashion.
 When a set top box 40 requires simple VCR functions such as stepwise fast
 forward mode or stepwise fast reverse mode, these simple VCR functions can
 be performed by another delivery SMU 20. In this case, the delivery SMU
 which does not include an agile storage medium, for example outputs video
 and/or audio data recorded in a certain format which will be described
 hereinafter in a number of virtual channels through the ATM interface with
 respective time delays between the virtual channels. ATM switch 1 then
 provides the video and/or audio data in the required play mode to the set
 top box 40 by changing the relationship between input virtual channels and
 output virtual channels under control by the system manager 60.
 Some examples of communications established between the end devices 40, the
 system manager 60 and the SMU's 20 by using the table data shown in FIG.
 11 will be explained hereafter. If the end device 40 (STB-2) requests a
 selected movie by calling the identification number 678901 corresponding
 to the movie and provided from one of the navigation devices 30 at time
 0:09, one of the service item providers 64 (SIP-1) is designated by the
 identification number.
 The service item provider 64 (SIP-1) then checks the present time and
 obtains from the table therein the next available time point 0:10 as the
 starting time of the movie, distribution control data including the number
 "2" designating the SMU 20 storing the video and/or audio data if the
 movie and the number "2" designating one of the service item streams (SIS)
 from the SMU 20 making the movie available from the beginning at the time
 point 0:10, and the virtual channel number "21" for this stream, and
 supplies the SMU 20 designated by the end number "2" with the SIS number
 "2", virtual channel number "21" and the end device number "STB-2".
 The service item provider 64 (SIP-1) up-dates the conversion table in the
 ATM switch 1 according to another table data available in the service item
 provider 64 (SIP-1) so that the relationship between input virtual channel
 number "21", for the service item stream (SIS) and the output virtual
 channel number "21" for the end device 40 (STB-2) is established.
 Therefore, the data stream of the requested movie is provided to the end
 device 40 (STB-2) from the beginning at time 0:10.
 If the end device 40 (STB-2) requests one of the service item providers 64
 (SIP-1) for full VCR function, the service item provider 64 (SIP-1)
 obtains from the table therein distribution control data including the
 number "4" designating the SMU 20 having full VCR function capability and
 the number "1" designating one of the service item streams (SIS) from the
 SMU 20 designated by the number "4" with the SIS number "1", virtual
 channel number "28" and the end device number "STB-1".
 The service item provider 64 (SIP-1) up-dates the conversion table in the
 ATM switch 1 according to another table data available in the service item
 provider 64 (SIP-1) so that the relationship between input virtual channel
 number "28" for the service item stream (SIS) and the output virtual
 channel 11711 for the end device 40 (STB-1) is established. Therefore, the
 data stream of the requested movie is provided to the end device 40
 (STB-1) with full VCR function.
 Such an interactive communication system as outlined above is suitable to
 be used as a platform for a plurality of server-owners, navigation device
 owners, system manager owners and users simultaneously, where one party
 can for example exploit one or several SMU's 20, as well as a system
 manager 60 and/or one or several navigation devices 30.
 In FIG. 1 the entire system is configured around a single ATM switch 1.
 Application of more than one private ATM switch and/or public ATM network
 is equally possible.
 Furthermore, another type of transmission network can be used. The network
 with one or more ATM switches, however, is considered to be the most
 suitable network configuration for the applications envisaged.
 Next, details of each device will be explained.
 FIG. 2 shows a configuration of a SMU 20. Each SMU contains a physical
 storage medium 21, for example an Magneto Optical (MO) disc and a
 corresponding driver or one or more hard discs and the corresponding
 drivers thereof, an ATM interface 29 as part of the SMU 20 or located
 outside such unit 20, a memory 25, for example for storing a table, and a
 controller 26 formed by a CPU 22, a RAM 24, a ROM 23, and a bus 27.
 CPU 22 of controller 26 controls the storage medium 21 and other operations
 of the SMU 20 according to software programs stored in ROM 23 and an
 additional control software program downloaded into RAM 24 and table data
 stored in this memory of the SMU 20.
 The physical storage medium 21 primarily contains service items, but can
 also contain control software program to be down-loaded to the end device
 40 or one or more of the SMU's 20 when required.
 ROM 23 of the SMU 20 preferably contains a microkernel operating system and
 a storage medium interface resident software such as an ATM drive, an MO
 disc driver. The microkernel operating system functions as a basic set of
 instructions, capable only of the most elementary of communication
 operations, e.g. down-load of control software specifically tailored for
 subsequent communications to be performed by the SMU 20. The ATM driver is
 used for establishing communications through the ATM interface 29. The MO
 disc driver is responsible for the mode in which the physical storage
 medium 21 functions which will be described hereinafter. The controller 26
 also contains a table 25, in which relationships between virtual channels
 and end devices 40 are established.
 The ATM interface 29 may communicate with the ATM switch 1 in a full duplex
 mode, where the ATM interface 29 can simultaneously handle incoming and
 outgoing ATM packets 28. In FIG. 2 such an ATM packet 20 is shown to
 contain a header portion A, usually comprising five bytes, and an
 information field portion B, usually comprising forty-eight bytes.
 RAM 24 contains executable code in ROM 23, a down-loadable module for
 optimum functionality as a server, and a buffer.
 FIG. 3 shows a SMU 20, where bus 27 is divided into a separate control bus
 and a separate data bus to provide a high throughput.
 FIG. 4 shows a schematic representation of control and data flow in the SMU
 20 shown in FIG. 3. Here distinction is made between incoming and outgoing
 video and/or audio data and incoming and outgoing control data and
 incoming control software program to be down-loaded. Respective packets of
 video and/or audio data, control data and software program, even if these
 packets are transferred to same SMU 20 or same end device 40, should have
 different routing information in the header to be distinguishable from
 each other.
 FIG. 5 shows a third embodiment of the SMU 20, where an ATM switch 1 and
 the ATM interface 29 of the SMU 20 are incorporated. As a result
 connections can be established from the SMU 20 directly through ATM
 interfaces 41 to the end devices 40. In this case, the system manager 60
 may be connected to the ATM switch 1 or the controller 26 may replace the
 function of the system manager 60.
 FIG. 6 shows a SMU 20 corresponding to the embodiment of FIG. 2, where the
 method for reading and outputting data segments from a physical storage
 medium, e.g. a disc is shown. As an example data groups are output via
 three virtual channels, which channels could also be formed by separate
 physical channels. In this figure the principle of reproducing staggered
 recording data, which will be further described hereinafter, is shown. The
 SMU 20 shown here contains a buffer 210 and a timer 211, where the buffer
 210 is preferably a part of the ATM interface 29. The video data is
 divided in a predetermined number T of sentences, where T corresponds to
 the number of channels and equals three in case of FIG. 6. Each sentence
 is divided in a predetermined number N of data groups and N equals four in
 case of FIG. 6. The video data are recorded in the storage medium 21 after
 the order of the data groups is changed in such a way that n-th (where
 n=1, 2, 3, 4 . . . N) data group of the first sentence is followed by n-th
 data group of the Tth, T-1th, . . . , and T-(T-2)th sentences
 sequentially, as n is sequentially increased, as shown in the upper left
 side of FIG. 6.
 The video data recorded in the above manner is sequentially and cyclically
 reproduced from the storage medium 21. The n-th data groups of the
 respective T sentences are sequentially stored in the buffer 210 and
 output to respective different virtual channels through the ATM interface
 29. After respective N data groups of T sentences are output, the virtual
 channels are switched over in the next and following cycles as shown in
 FIG. 7, so that N.times.T data groups are continuously reproduced via each
 virtual channel with a time difference of one sentence from each other as
 shown in the right hand side of FIG. 6.
 FIG. 8 shows a configuration of a navigation device 30. Navigation device
 30 preferably comprises: a controller 36, formed by a CPU 32, a ROM 33, a
 RAM 34 also for navigation software programs to be down-loaded to the end
 devices 40 and a bus 37; a table 35 for available video programs and
 identification data, for example a public address of available video
 programs, and also an ATM interface 31. The controller 36 controls
 operation of the navigation device 30 according to programs stored in ROM
 33 and RAM 34. The navigation device 30 down-loads navigation software
 programs to the set top box 40, when the set top box 40 requires a
 navigation operation to the navigation device 30. The navigation device 30
 then provides information relating to available video programs and
 identification data thereof to the set top box 40. Public addresses can be
 used when a public network is used in the interactive communication
 system. Many kinds and versions of the navigation menu can be provided, if
 the interactive communication system has a plurality of navigation devices
 30, which handle for example a Japanese version, an English version, three
 dimensional graphical version etc.
 FIG. 9 shows the configuration of an end device, here a set top box 40. The
 set top box 40 may comprise a CPU 45, a RAM 46, a ROM 47 and an MPEG
 decoder 48. CPU 45 controls operation of the set top box 40 according to
 programs stored in ROM 47 and RAM 46. Said programs may be down-loaded
 from the system manager 60, a SMU 20 or a navigation device 30. The MPEG
 decoder 48 decodes compressed video data and/or audio data, supplied via
 the ATM switch 1 and supplies video data, if necessary combined with data
 from a graphic processor 49 through a video RAM memory 50 to the monitor
 43 and supplies audio data via an amplifier 51 to the speaker system 42.
 The CPU 45 produces demand data according to instruction data input
 through the keyboard 44 or a similar device by the user. Such demand data
 is output via the ATM interface 41.
 FIG. 10 shows a configuration of the system manager 60. The system manager
 60 contains a CPU 68, a ROM 69, a RAM 70, and here a memory for various
 VOD software programs to be down-loaded to the set top boxes 40 and/or the
 SMU's 20, an ATM interface 61 and memory 71, e.g. in the form of table
 means. The CPU 68 controls operation of the system manager 60. The system
 manager 60 provides operation software to SMU's 20 and set top boxes 40
 and updates tables for data representing a relationship between input
 virtual channels and output virtual channels in the ATM switch 1. Such a
 system manager 60 can perform all functions described above relating to
 the storage medium manager 62, the program manager 67, the service item
 providers 64, the service item group 65 and the server routing manager 66.
 FIG. 11 shows a sequence of scenes, where said sequence can be accomplished
 by displaying video data on various transmission channels. In this example
 twelve (virtual) transmission channels are employed as T=12, though from
 channels 4 to 12 are omitted from the drawing for simplification. Data
 groups are reproduced from a physical storage medium 21 containing the
 staggered recording data and output via these virtual channels in a
 similar manner to FIG. 6 and 7. As shown in FIG. 11, the sequence of
 scenes can be altered by switching from channel to channel for input of
 video data comprising such a scene so that a simple VCR function can be
 realized. For example, by switching from channel 1 to channel 2 while the
 scene `2` is displayed, the scene `4` can be displayed, thereby skipping
 scene `3` as fast forward mode. Similarly, by switching from channel 3 to
 channel 1 while the scene `6` is displayed, the scene `5` will next be
 displayed thereby creating a reverse mode. Such switching between virtual
 channels can be done by updating the conversion table of the ATM switch 1
 under control of the system manager 60 according to the control data from
 the end device 40. When switching between channels is not performed, the
 natural sequence of scenes will be followed, as this is the sequence in
 which video data occurs on a single channel.
 Scene 5 appeared after scene 6 by switching from channel 3 to channel 1.
 Thus reverse skip play is performed.
 FIG. 12 shows an example of a mosaic function to be performed by an end
 device 40, whereby selected scenes taken from a sequence are displayed on
 monitor 43. A user can in this way select a starting point, other than the
 beginning of a film, by issuing a corresponding demand through the input
 device 44. Such a mosaic function can of course also be used for
 visualizing a menu of service items selectable through one or several
 navigation devices 3, e.g. title frames of several selectable video
 programs, where such selected scenes for mosaic function can be displayed
 by switching the virtual channels on a real time basis and storing these
 into the video RAM 50 simultaneously or by reproducing the video data
 previously stored in the SMU 20 as mosaic video data. Next, recording
 formats of video data on a physical storage medium 21 will be explained,
 referring to FIGS. 13-15.
 In FIG. 13 a physical storage medium 21 is shown, where a head 90 is
 attached to an arm 91, movable to and from the center of the physical
 storage medium 21. Here, the physical storage medium 21 is formed by a MO
 disc. Data tracks of the MO disc 21 contain data groups in the staggered
 recording sequence 92 shown in this FIG. 13 above the physical storage
 medium 21. The arrows above and beneath this representation of sequence 92
 denote the order, in which head 90 reads the data groups from the physical
 storage medium 21. As shown here, reproducing head 90 skips data groups on
 the outbound pass over the physical storage medium 21, where the skipped
 data groups are read during the inbound pass over the physical storage
 medium 21. In this way no time loss occurs between the end and start of a
 sequence of data groups, to be sent to the controller 26 of the SMU 20
 (see FIG. 6) and a continuous flow of data groups in the order, required
 by the controller 26 of the SMU 20 is ensured. Because of the continuous
 flow of data groups a buffer memory of only a small size is required.
 Video data, which is to be recorded in a storage medium with a format
 described above, is reproduced from said storage medium 21, and output
 from the SMU 20 to the ATM switch 1 through the ATM interface 29 as three
 virtual channels.
 In FIG. 14 first and second video data with the same content but opposite
 time lines are recorded on the disc. In this case the data groups of the
 first video data and the data groups of the second video data are
 interleaved. The first video data is used, when the set top box requires
 normal forward, fast forward, or stepwise fast forward play mode. On the
 other hand, second video data is used when the set top box requires
 reverse play mode. Furthermore it is possible for the data groups of the
 first video data to be recorded on every other track of the disc. The data
 groups of the second video data are stored in remaining tracks of the
 disc. Then the recorded first video data is reproduced from every other
 track of the disc by moving a reproducing head in a first direction.
 Recorded second video data is reproduced from the remaining tracks of the
 disc by moving the reproducing head in this first direction. It is also
 possible to reproduce the second video data in the reverse if the first
 direction after the first video data are reproduced so that similar
 effects to the recording format shown in FIG. 13 is obtained.
 In the first and second video data are encoded in accordance with MPEG
 standard, the second video data should be encoded in the reverse manner of
 the first video data. In such a case, it may not be possible to reproduce
 the second video data in the reverse direction as explained above. In the
 example of FIG. 14A also the distance of head movement is minimized, both
 for forward and reverse play, as the forward data groups (1F, 2F, 3F, 4F
 etc.) are recorded in every fourth track in a similar manner to FIG. 13,
 while the reverse data groups (12R, 11R, 10R, 9R, etc.) are recorded
 before 2F, 3F, 4F etc. respectively, also in every fourth track. Also the
 distance of the head movement is minimized at the edges of the disc as
 will become clear from the sequences of 6F, 7F and 8F and 7R, 6R and 5R at
 the inside edge, and 12F, 1F and 2F, and 1R, 12R and 11R, respectively.
 FIG. 15 shows a diagram of a sequence of video data displayed on a monitor,
 where the sequence is obtained by using the recording format and reading
 sequence shown in FIG. 14, and by receiving from and sending to different
 virtual channels, respectively in order to obtain forward and/or reverse
 play modes, for which purpose data are recorded in the staggered fashion,
 described referring to FIGS. 13, 14 and 14A as examples.
 Multi-cast functions will be explained, referring to FIG. 16. In the
 multi-cast function the system manager 60 as shown in FIG. 1 also manages
 distribution of video data. If the system manager 60 receives a demand
 data from one or more of the end devices 40, even in the course of
 service, asking to provide a same video and/or audio data as transmitted
 from one of SMU 20 to or requested from other end devices 40, the system
 manager 60 outputs to the ATM switch 1 distribution control data including
 information of the input virtual channel of the selected video data from
 the SMU 20 and the output virtual channel of the end device 40 requesting
 the video and/or audio data which are generated in response to the
 received demand data. For example, if an end device STB-3 requests same
 video data "video 1", "video 2", and "video3" as requested by and
 transmitted to another end device STB-1 from the SMU 20 through an input
 virtual channel "vc 1" and an output virtual channel "vc7", the system
 manager 60 outputs the updated conversion table to the ATM switch 1, so
 that the header of the ATM packets transmitting "video 1", "video 2" and
 "video 3" are replaced in the ATM switch 1 with not only the header
 corresponding to an output virtual channel "vc7" but also the header
 corresponding an output virtual channel "vc8" designated by the end device
 STB-3. Therefore, the ATM packets containing "video 1", "video 2" and
 "video 3" are supplied to both of the end devices 40 STB-1 and STB-3
 simultaneously.
 The sequence of communication, shown in FIG. 17, represents a method in
 which flow of video data from a SMU to a set top box 40 is established.
 First, in step 1, a user informs a set top box 40, denoted by STB, through
 his input device 44, that he wishes to gain access to the system. The set
 top box 40 replies by asking the user in step 2 what kind of service, like
 video-on-demand, games or just television, the user wishes to select. Such
 selectable options may be stored in memory of the set top box 40. Next, in
 step 3, the user enters his choice through his input device 44 to the set
 top box 40, which then involves the navigation device 30, in this figure
 denoted by Navi. Description below will relate to the case, where the user
 has selected a video-on-demand service menu, for which one or several
 navigation devices 30 are suitable. Nevertheless, only one navigation
 device 30 is represented in this figure for clarity.
 In step 5 navigation device 30 provides set top box 40 with a menu of
 selectable video services, to which the navigation device 30 can gain
 access. In said menu options can also be included, referring the set top
 box 40 to another navigation device 30, which can gain access to other
 video services. In the next step 6 set top box 40 passes the menu on to
 the user by display thereof on monitor 43. In step 7 the user enters his
 choice through his input device 44, which in this case is a request for a
 further menu. This request is relayed to navigation device 30 in step 8,
 whereupon navigation device 30 supplies a new menu of selections to set
 top box 40 in step 9. Steps 7-10 can be repeated a number of times, until,
 as is the case in step 10, a menu displayed on monitor 43 by set top box
 40 contains an option for a video program the user wishes to select, which
 is represented by step 11. Set top box 40 in step 12 requests service item
 provider 64, denoted by SIP, to provide for a video stream to a top set
 box with a given public address, corresponding to the address of the
 service item provider 64. In step 13 service item provider 64 first
 request service item group 65, denoted by SIG, to provide set top box 40
 with control data necessary for optimum handling by the set top box 40 of
 the video stream to be established, which control software is down-loaded
 into the set top box 40 in step 14. Now, set top box 40 is capable of
 issuing commands relating to VCR functions, where in step 15 the first
 play command is issued to the service item provider 64. In step 16 service
 item provider 64 locates the first available video stream for the request,
 which in this case originates from storage medium unit 40, denoted here by
 SMU1, and sets ATM switch 1, denoted by ATM SW to connect said storage
 medium unit 20 and set top box 40 by re-writing the virtual channel table
 in the ATM switch 1. In steps 17 and 18 the requested video stream is
 routed through ATM switch 1 to set top box 40, where the requested video
 program can now be displayed on monitor 43.
 In FIG. 18 dynamic reconfiguration of the system is clarified. In this
 timing chart on line 13 the service items group (SIG) creates a new
 instance of a SMU installer and provides the number of the source SMU, of
 the destination SMU and other parameters. In line 14 the SMU installer
 executes a download operation to SMU1 as destination and leaves SMU1
 waiting for data. In line 15 the SMU installer requests SMU2 as source to
 start providing data to SMU1 as destination. In line 16 the requested data
 is transferred from SMU2 to SMU1. In line 17 SMU2 reports to the SMU
 installer that the data transfer is completed. In line 18 the SMU
 installer informs the SIG that SMU1 is ready to serve data, whereafter the
 SMU installer disappears. In line b19 the SIG requests SMU1 to start
 serving data to a certain virtual channel, so that such data can be served
 to end users.
 In the foregoing description a number of characteristics and details have
 been described with reference to preferred embodiments. It should however
 be understood that the present invention is not limited to the above
 description of such preferred embodiment. The requested rights are defined
 by the following claims.