US20120207455A1 - Playback device for optical recording medium. optical recording medium playback method, and playback program for optical recording medium - Google Patents

Abstract

To play back an optical disk requiring network connection, a playback device is provided, which has a function by which the network condition is evaluated before playing back a title. The playback device plays back the optical disk including programs connecting through the network to data-supplying sources; the playback device determines whether or not the network circuit is available; and when the network connection is not available depending on a network connection status or its memory amount, the playback device plays back with a non-network-ready mode.

Description

TECHNICAL FIELD
• This application is a Divisional of co-pending application Ser. No. 12/226,685, filed on Oct. 24, 2008, the entire contents of which are hereby incorporated by reference and for which priority is claimed under 35 U.S.C. §120.
• The present invention relates to playback devices that play back information recorded on an optical recording medium; it especially relates to a playback device for an optical recording medium on which a program realizing an interactive function is recorded to be executed in order that online network contents (data) can be downloaded.
BACKGROUND ART
• DVD standards have been known for devices that play back stream information recorded on optical disks. On the other hand, the devices that meet with the standards for next-generation optical disks such as BD (Blu-ray Disc standards) and HD-DVD standards cannot only play back stream information thereon, but also execute programs recorded on the optical disks. The programs are recorded to provide an interactive function, and the programs are executed so that new contents (data) can be downloaded through the network and played back in synchronization with the stream information.
• As an example of application programs using the network, a video-playback device has been known in which a file that updates the contents recorded on the optical disk can be downloaded (for example, refer to Patent document 1). According toPatent document 1, the network can be used, as a sub-channel, to download a language into which the contents are not dubbed. Therefore, even if there is a playback-only disk on which movie contents are recorded with Japanese voice only, English-dubbed voices are downloaded, upon playing the disk, to a local storage in the video-playback device so that videos in the optical disk can be played back in synchronization with the English-dubbed voices having been downloaded.
• There is also known a video-playback device (for example, refer to Patent document 2), in which when there exist Web contents that correspond to video scenes currently being played back an icon is displayed to show that there exist online network contents, so that users are notified that the video scenes link to the Web contents. This video-playback device holds history information about connecting to Web contents in the video-playback device; and when connecting to Web contents, the device displays or hides the icon described above by referring to the connection history. When there exists less possibility for connecting the network, the network connect icon is hidden, preventing its users from unnecessarily doing access operations.
• Patent Document 1: Japanese Patent Laid Open NO. 2005-159589 (page 4-5, FIG. 3)
• Patent Document 2: Japanese Patent Laid Open NO. 2000-207873 (page 2-5, FIG. 4)
DISCLOSURE OF INVENTION
• InPatent document 1, there is description about a video-playback device that can download an update file necessary to the contents recorded in the optical disk. However, it is not disclosed about how to deal with such cases when the network cannot be used (for example, “disconnection of the network cable”, “no destination content in the network”, and “an extremely slow communication speed due to heavy traffic on the network circuits”).
• As described above,Patent document 2 discloses a technique in which a playback device holds history information about connecting to Web contents and determines, on the basis of the information, whether or not a probability of successful connection to a destination content recorded in the connection history information is high. In the technique ofPatent Document 2, only the destinations recorded in the connection history information are taken into consideration for connection; however, new destinations with which the playback device has not communicated through the network are not taken into consideration. In addition, in the technique, such cases when a network circuit itself does not effectively function—for example, when the network cable is disconnected or when no setting operations are performed for the network connection—are not taken into consideration.
• The present invention is made to solve the problems described above, and aims to provide a playback device for an optical recording medium that has a function to determine a network condition, when playing back an optical recording medium with a network connection function, before playback of the title.
• According to the present invention, a playback device for an optical recording medium including a program that connects to a data-supplying source through the network comprises:
• a network-circuit-information acquiring unit that outputs a connection condition signal concerning connection condition between the network and the playback device for an optical recording medium;
• a system control unit that outputs, on the basis of the connection condition signal outputted from the network-circuit-information acquiring unit, a determination signal indicating whether or not to connect to the network; and
• a data playback unit that plays back data recorded in the optical recording medium in a network-ready mode in which playback is performed with reference to the data supplied from the data-supplying source, or in a non-network-ready mode in which playback is performed without reference to the data supplied from the data-supplying source;
• wherein, when the determination signal outputted from the system control unit indicates that the playback device of the optical recording medium does not connect to the data-supplying source, the data playback unit plays back data recorded in the optical recording medium in the non-network-ready mode.
• By configuring a playback device for an optical recording medium as described above, the device according to the present invention determines whether to be able to use the network circuit before playing back the optical recording medium including network connect functions; when the network cannot be used, the playback device performs playback in the non-network-ready mode. Thus, it is possible to reduce possibility of operations that are fundamentally unnecessary for the users.
BRIEF DESCRIPTION OF DRAWINGS
• FIG. 1 is a block diagram of a system configuration described inEmbodiment 1 according to the present invention;
• FIG. 2 is an external view of an optical disk used inEmbodiment 1 according to the present invention and shows an internal file data structure thereof;
• FIG. 3 shows a logical file structure of the optical disk used inEmbodiment 1 according to the present invention;
• FIG. 4 is a structural view of the stream that shows an internal data structure of a stream information file in the optical disk used inEmbodiment 1 according to the present invention;
• FIG. 5 shows data syntax in a playback-control-information file used inEmbodiment 1 according to the present invention;
• FIG. 6 shows data syntax in a program management file used inEmbodiment 1 according to the present invention;
• FIG. 7 shows a list of network circuit availability that are obtained by a network-circuit-information acquiring unit ofEmbodiment 1 according to the present invention;
• FIG. 8 is an example of an alarm screen that is displayed when playing back an optical disk requiring network connection in a situation where a coded-video playback device ofEmbodiment 1 according to the present invention cannot use a network circuit; and
• FIG. 9 is a flow chart of operations forEmbodiment 1 according to the present invention.
REFERENCE NUMERALS
• 100 playback device
• 101 system control unit
• 102 optical disk
• 103 playback drive unit
• 110 demultiplexer
• 111 video decoder
• 112 audio decoder
• 113 OSD generator
• 114 video mixer
• 115 display
• 120 memory
• 121 network interface unit
• 122 HDD
• 123 system register set
• 124 network-connection-necessity determining unit
• 125 network-circuit-information acquiring unit
• 126 effective memory volume determining unit
• 130 operation unit
• 140 decoding block
• 201 inner circumference side of the disk
• 202 outer circumference side of the disk
• 210 read-in area
• 211 file management information area
• 212 user data area
• 213 read-out area
• 220 playback-control-information area
• 221 playback-control-information file
• 222 program management file
• 230 stream information area
• 231 stream information file
• 240 program record area
• 241 program file
• 300 root directory
• 301 disk directory
• 302 stream management directory
• 303 program management directory
• 400 packet
• 401 header information
• 402 ID
• 501 Studio_ID
• 502 Disc_ID
• 503 num_of title
• 504 type_of title
• 505 ref_to_playlist_id
• 506 ref_to_program_id
• 507 playlist information
• 508 num_of_stream
• 509 stream filename
• 510 attribute information management table
• 511 access point management table
• 601 num_of_program
• 602 program_name
• 603 num_of_application
• 604 type_of_application
• 605 application_ID
• 701 connection availability status
• 702 connection-date-time information
• 703 communication speed information
• 801 ‘continue current playback mode’ button
• 802 ‘change to non-network-ready mode’ button
• 803 area for displaying the status of the network circuit
• 804 area for displaying download environment
BEST MODE FOR CARRYING OUT THEINVENTIONEmbodiment 1
• InEmbodiment 1, aplayback device100 will be explained, in which, when the playback device cannot use a network circuit but plays back an optical disk including a program having a function to connect to the network, the device notifies in advance its users that network contents cannot be used, so that the device can prevent them from operating actually unnecessary operations.
• Note that hereinafter, “being unable to use network contents” means a condition that “network circuits cannot be used normally”, for example, a condition that the network cable is broken, a condition that the network configuration of the playback device itself is not appropriately performed, a condition that the network load is extremely high, and a condition that there exists no destination content.
• FIG. 1 is a block diagram representing a system configuration ofEmbodiment 1 according to the present invention. In the figure, asystem control unit101 integrally controls theentire playback device100. In an optical recording medium102 (hereinafter, referred to as “an optical disk”), multiplexed stream information of coded screen images described later and playback control information for the stream information are recorded. Playing back files in theoptical disk102 is performed through aplayback drive unit103.
• Theplayback drive unit103 sequentially reads stream information files, described later, and then ademultiplexer110 separates a stream to extract a video stream or an audio stream which is coded and compressed; avideo decoder111 decodes to a video signal the video stream that is separated by thedemultiplexer110 but still coded in such as MPEG-2; anaudio decoder112 decodes to an audio output signal the audio stream that is separated by thedemultiplexer110 but still coded in such as AC-3; an OSD (On Screen Display)generator113 generates signals for the display images that thesystem control unit101 creates as alarm screens, device operation status screens, function selection screens and the like; avideo mixer114 superimposes into the video signal generated by thevideo decoder111 the video signals generated by theOSD generator113 and outputs as a video output signal; and the decoded video output signal and the audio output signal outputted from theaudio decoder112 are converted to be watched and listened to through adisplay115.
• Amemory120 temporarily stores the playback control information of the stream information recorded in theoptical disk102 so that thesystem control unit101 can quickly access the playback control information. In the playback control information, there included is information such as attribute information about video and audio in the coded video stream separated from the stream information recorded in theoptical disk102 and information indicating a correspondence relation between playback start time information and playback start position information on a stream information access basis (typically, by GOP unit). Anetwork interface unit121 connects theplayback device100 to the network; an HDD (local storage)122 records information downloaded from the network. TheHDD122 can serve its purpose as long as it is a nonvolatile recording medium, such as a SmartMedia and a memory card. In addition, it is not necessarily placed inside and may be detachable.
• A system register set123 includes a plurality of registers that can store system parameters which define operating conditions of theplayback device100. The system parameters include information representing playback state such as a title number and a playlist number that are being currently played back, video/audio playback compatibility, and readiness for accessing the network (as defined as a profile). Here, the system parameter about its readiness for accessing the network indicates whether or not theplayback device100 itself has a function to access the network, and never indicates whether the network communication is available.
• To play back theoptical disk102, two playback paths are provided—a network-ready mode and a non-network-ready mode, and theplayback device100 typically uses an optical disk title method in which thedevice100 determines the playback path on the basis of the system parameter representing its ability to access the network.
• A network-connection-necessity determining unit124 determines whether each program recorded in theoptical disk102 needs to connect to the network. The network-connection-necessity determining unit124 outputs a detection signal indicating whether or not each of the programs recorded in theoptical disk102 needs to connect to the network. A network-circuit-information acquiring unit125 determines whether thenetwork interface unit121 can normally communicate with the external network circuit. At power-on of theplayback device100 or at the start of playing back theoptical disk102, the network-circuit-information acquiring unit125 determines whether the network is in a normal condition to be used. In addition, the acquiring unit may have a function to measure the execution speed of the network at the same time when it determines whether the network can be used. The network-circuit-information acquiring unit125 outputs a detection signal that represents a connection condition between theplayback device100 and the external network circuit.
• An effective memoryvolume determining unit126 determines whether the amount of files to be downloaded from the network is the one that anHDD122—a medium recording download files—can store. The figure exemplifies the network-connection-necessity determining unit124, the network-circuit-information acquiring unit125, and the effective memoryvolume determining unit126 which are configured with firmware or the like in thesystem control unit101; however, they may be outside of thesystem control unit101 and may be hardware having corresponding functions. The effective memoryvolume determining unit126 outputs a volume detection signal representing a data amount supplied from a data-supplying source described later.
• From anoperation unit130, a user or the like sends commands to theplayback device100. Generally, theoperation unit130 is an operation panel that is placed at a front panel of theplayback device100 or a remote control unit. Theplayback device100 interprets a command requested from theoperation unit130, and controls a decoding block (data playback unit)140 to play back arbitrary stream information.
• For example, when the user commands theoperation unit130 to play back an arbitrary program title, the command is transmitted to thesystem control unit101. Then, thesystem control unit101 reads out from playback control information stored in thememory120 the playlist information, which is described later, constituting that program title. The playlist information is composed of one or more playing back sections called play items, and the control unit obtains a physical address in theoptical disk102 at which a file of stream information specified by each play item is recorded. Then, the stream information read out from its corresponding address is played back at theplayback drive unit103, and sequentially sent through thedemultiplexer110 and the decoders to output video/audio information at thedisplay115.
• When connecting to the network, the program title described above has been linked to a program, which is executed to access a URL site (data-supplying source) in the network that is specified in the program.
• FIG. 2 illustrates the exterior appearance of theoptical disk102 and a data structure of internal files thereof. In the figure, file data on theoptical disk102 is recorded from theinner circumference side201 of thedisk102 toward theouter circumference side202 thereof Start information, physical characteristics and the like of theoptical disk102 are written in a read-inarea210; file system information of theoptical disk102 is stored in a filemanagement information area211; a content supplier can in advance record information in auser data area212; and disk terminal information is written in a read-outarea213.
• Theuser data area212 consists of a playback-control-information area220, astream information area230, and aprogram record area240. In thestream information area230 recorded are one or more stream information files231 which contain series of streams multiplexed and compressed. A video stream and an audio stream are multiplexed to be contained in the stream information files231, from which thedemultiplexer110 separates them for generating a video stream and an audio stream. For further explanation, it is assumed that video streams are stream information coded in a compression unit such as a GOP (Group of Picture) defined in the MPEG-2 ES (elementary stream) standards.
• In theprogram record area240, a plurality of program files241 is recorded. Eachprogram file241 is an executable file written in a programming language such as JAVA (trademark) to enhance an interactive function such as accessing an arbitrary Web site. The program files241 may be executed in synchronization with the stream information file231 or may be executed independently. In addition, if a disk does not require network connection, it is not necessary to record the program files241 therein.
• In the playback-control-information area220, a single playback-control-information file221 and a singleprogram management file222 are recorded. In the playback-control-information file221, written are playback section information and playback sequence information of program titles, content information of the stream information file231 and the like. As for each of access points (generally, GOPs) composing the stream information file231, also described are a start address, display start time information and the like. In addition, the access point may be composed of a plurality of GOPs. Theprogram management file222 contains management information for the program files241, such as attribution information of the programs and information indicating a stream information file231 to be played back in synchronization with each program.
• InEmbodiment 1, explanation is made for a case where there are a single playback-control-information file221 and a singleprogram management file222; however, each of the information may be subdivided into a plurality of files to be managed. This configuration shows an example in which the playback-control-information file221 contains all of the program title information and the playlist information recorded in theoptical disk102; however, the information file may be divided to be stored on an information basis.
• FIG. 3 illustrates a logical file structure of theoptical disk102 ofEmbodiment 1 according to the present invention. Aroot directory300 is the highest directory structure in a file structure in which files are configured logically and hierarchically; adisk directory301 is a directory structure hierarchically subordinate to theroot directory300. Thedisk directory301 is configured with the playback-control-information file221 that is the disk content management information recorded in theoptical disk102, theprogram management file222, astream management directory302 that is a folder storing all the stream information files231 together, and aprogram management directory303 that is a folder storing all the program files241 together.
• In the figure, it is assumed for explanation that the stream information files231 and the program files241 are recorded with five-digit filenames. For the filenames, any five-digit numbers are applicable and they need not be serial numbers. As an example, the stream information files231 and the program files241 are arranged in the separate directories; however, they may be arranged in the same directory or directly arranged in theroot directory300. It has been exemplified that the stream information files231 and the program files241 are each created as individual files corresponding to a certain management unit; however, they may be recorded to a single file each.
• FIG. 4 is a stream structure view showing an internal data structure of astream information file231. The stream information file231 is composed of fixed-length data units each called apacket400. Video data, audio data, and stream management data are divided intopackets400, and then multiplexed to create thestream information file231. At the top of eachpacket400, there isheader information401 which contains an ID (Identification)402 for identifying a type of data in thepacket400. By using theIDs402, thedemultiplexer110 sorts out packets into video data, audio data, stream management data and the like.
• FIG. 5 is a diagram to explain the syntax of the playback-control-information file221. “General disk information” is provided to identify the disk and contains a Studio_ID501—a number to identify a producer of theoptical disk102—and aDisc_ID502—a number to identify the contents in theoptical disk102. That is, by the Studio_ID501 and theDisc_ID502, the contents recorded in theoptical disk102 are identified among all disks distributed in the market. The Studio_ID501 and theDisc_ID502 are also used to identify an update file to be downloaded.
• In the information file, a “num_of title503″is recorded to show the total number of program titles recorded in theoptical disk102, and the next loop statement repeats statements (below “for” statement) as many times as those indicated by the “num_of_title503”. A “type_of_title504” holds information to distinguish the type of the program title. As for the program title, there exist two types of titles: one is a “normal title”, which is played back according to playlist information; and the other is a “program title”, which is played back by executing a program. The type is identified with its “type_of_title504”. When the “type_of_title504” indicates the normal title, a “ref_to_playlist_id505” is recorded as information to specify playlist information described later. When the “type_of_title504” indicates the program title, a “ref_to_program_id506” is recorded as information to specify a program described later.
• In the file, “playlist information507” is also recorded. The “playlist information507” contains information about all the playlists, which is configuration information for a program; that is, it contains playback section information (the filename of a stream information file to be played back, and its playback start time and playback end time) for each playlist. On the basis of its playback section information, theplayback device100 can determine which section in a stream information file231 is to be played back.
• In the information file, a “num_of_stream508” is recorded to show the total number of stream information files231 recorded in theoptical disk102, and the next loop statement repeats statements (below “for” statement) as many times as those indicated by the “num_of_stream508”. Astream filename509 is five-digit figure information representing the name of thestream information file231. An attribute information management table510 contains attribution information of video information and audio information used in thestream information file231. Furthermore, each of video information and audio information that configure a stream contains packet IDs and the like, and thedemultiplexer110 separates video data, audio data, stream management data and the like, using the packet IDs.
• An access point management table511 is a list of information on which a stream read-out position and playback start time are recorded for each access point; by using the information, random-access playback that is needed for such as a search operation and special playback operations can be performed. For example, when video data are encoded into an MPEG-2 video stream, the beginning of a GOP (Group of Picture) corresponds to an access point; for each GOP, information of playback start time and a playback start address (a relative position from the beginning of its stream file) is written in the table. Theplayback device100 calculates the playback start address of the stream information file231 from its playback start time information to perform random-access playback.
• FIG. 6 is a diagram for explaining the syntax of theprogram management file222. In the management file, a “num_of_program601” is recorded to show the total number of program files241 recorded in theoptical disk102, and the next loop statement repeats statements (below “for” statement) as many times as those indicated by the “num_of_program601”. A “program name602” is five-digit figure information representing the name of theprogram file241, so that the information specifies theprogram file241. As for program general information, recorded are its general information such as programming date and operational restrictions.
• A program is composed of a plurality of applications, and the total number of the applications is recorded in a “num_of_application603”. The next loop statement repeats statements (below “for” statement) as many times as those indicated by the “num_of_application603”. A “type_of_application604” is information that indicates whether or not the application is to be connected to the network. In an “application_ID605”, recorded is a unique ID number that identifies an application. In general information of an application, which is shown in the figure, recorded is general information such as information that specifies a stream information file231 to be played back in synchronization with the application, and restrictions on operations of the application.
• According to the present invention, when a program is executed, all applications composing the program are checked on the basis of the “type_of_application604” whether or not the program contains an application connecting to the network. In addition, when anoptical disk102 contains no attribution information such as the “type_of_application604” in theprogram management file222, information in the referringprogram file241 may be directly analyzed to determine whether or not to connect to the network.
• FIG. 7 is a list of network circuit availability that the network-circuit-information acquiring unit125 obtains (hereinafter, referred to as “a circuit-condition history list”). The circuit-condition history list is composed ofconnection availability status701, connection-date-time information702, andcommunication speed information703. In theconnection availability status701, recorded is information about whether connection is successfully performed; in the figure, “‘OK’ means successful connection”, and “‘NG’ means connection failure”. In the connection-date-time information702, recorded is time when the device has tried to establish a network connection. The time information may be obtained from a time information acquisition unit that is not illustrated in the figures, or may be obtained when connected to the network (only when connected successfully). In thecommunication speed information703, recorded is a circuit speed when connected to the network. The circuit-condition history list is made by the network-circuit-information acquiring unit125 upon an instruction from thesystem control unit101. The circuit-condition history list is recorded in thememory120 or theHDD122 for quick access.
• It is only necessary for the circuit-condition history list to contain as minimum information the latestconnection availability status701; the connection-date-time information702 and thecommunication speed information703 are not inevitably needed. However, by listing theconnection availability statuses701, the connection-date-time information702, and thecommunication speed information703, the user can see at a glance time slots during which its circuit speed is fast.
• FIG. 8 shows an example of an alarm screen that is displayed, when network connection is necessary to play back theoptical disk102 but theplayback device100 cannot use the network circuit. On the alarm screen, a ‘continue current playback mode’button801 and a ‘change to non-network-ready mode’button802 are provided; through theoperation unit130, the user selects and pushes one of these buttons to change its playback mode that specify whether or not theplayback device100 connects to the network.
• As auxiliary relevant information, whether or not the communication through the network is in good condition may be displayed in anarea803 for displaying the status of the network circuit. Criteria (threshold value) for determining whether the network circuit is in a good condition may be set on an initial setting screen by the user. The figure shows an example in which the threshold value is set as 500 kbps while the current communication speed is 400 kbps. Because the current communication speed is lower than the threshold value, it can be determined that the communication quality is bad. Communication quality may be subdivided by setting multi-level threshold values. Because such information is displayed, the user can know in detail and in advance whether a lot of time is needed for downloading due to its slow network communication speed, which makes the user feel less irritated or less inconvenient against a long time to complete downloading.
• The condition of the network communication may be obtained by directly confirming whether to access the network upon playback of theoptical disk102 or by determining from the latest connection record in the circuit-condition history list described above.
• When the circuit-condition history list is used, thesystem control unit101 reads out the information stored in advance in thememory120 as described above, so that the system control unit can quickly grasp without sequentially accessing theoptical disk102 whether the network circuit is available. In addition, the information displayed in thearea803 for displaying the status of the network circuit does not always need to be displayed in the alarm screen shown inFIG. 8; the circuit state may be indicated by a display tube, an LED or the like that is not shown in the figure but provided for theplayback device100; there may be provided with a function by which the circuit state is displayed on an initial setting screen in theplayback device100 or on another screen appearing by a special key. Provided with a user interface that simply and quickly displays such information, the user can grasp at a glance whether the network connection can be performed. Because such information is displayed, the user can use it to determine whether network cable breaking exists, and to immediately know the speed of the network circuit.
• Furthermore, as another auxiliary relevant information, such information as whether the amount of downloading memory is larger than a specific size may be displayed in anarea804 for displaying download environment. From such information, the user can estimate and know whether theplayback device100 has enough recording area to contain the information when it is downloaded through the network. In addition, the specific size may be set by the user in the initial setting screen or the like, or may be set as a possible maximum size to be downloaded when theoptical disk102 is inserted. From the information, the user can know in advance and in detail about a recording amount necessary for downloading or a recordable area in theplayback device100; therefore, a malfunction that all of the recording area is consumed during download to abort the downloading can be prevented from occurring.
• FIG. 9 shows the operation flow ofEmbodiment 1. A typical operation of theplayback device100 shown inFIG. 1 will be explained in detail, usingFIG. 9 (referring toFIG. 1 toFIG. 8, when necessary). When anoptical disk102 is inserted in theplayback drive unit103, thesystem control unit101 reads out file system information stored in the filemanagement information area211 in theoptical disk102. From the file system information, a logical directory structure shown in theFIG. 3 can be developed; then, the playback-control-information file221, theprogram management file222, and all program files241 that are recorded in theoptical disk102 are read into thememory120 according to instructions from the system control unit101 (S101).
• Then, the network-circuit-information acquiring unit125 in thesystem control unit101 checks whether a network destination is ready, by using the ping command that is a basic command to check whether IP packets can reach to a destination in a TCP/IP network (S102). Because it is possible to measure an arrival time from the destination by the ping command, the circuit speed of the network can be calculated. Although an example in which the ping command is used is described in the present embodiment, a similar command may be used to check its network connection.
• The information obtained above is outputted from the network-circuit-information acquiring unit125 as a connection condition signal, and stored in thememory120 or the HDD122 (the information is referred to as “a network circuit information analysis result”) as the circuit-condition history list shown inFIG. 7. Since the circuit-condition history list is contained in thememory120, whether or not the network circuit is available is immediately known by accessing the list, even if theoptical disk102 is not inserted. Obtaining the network circuit information (the network availability and the circuit speed calculation) is not limited to a time when the disk is inserted or before its title is played back; the information may be obtained when turning on the power for theplayback device100 before playing back the title, or obtained by measuring at fixed intervals (poling). The device may be configured so that the user can change on the initial setting screen or the like, the methods and frequencies of obtaining the network circuit information. By configuring in such a way, thesystem control unit101 does not perform unnecessarily a lot of communication controls, so that the load of the entire system can be curbed.
• Then, when a program title number to be played back is inputted from theoperation unit130, thesystem control unit101 reads its program title information (504,505, and506) corresponding to the program title number from the playback-control-information file221 developed in thememory120. And then, thesystem control unit101 determines from the “type_of_title504” whether the type of the program title is “a normal title” or “a program title”. If its type is a “program title”, theprogram management file222 specifies a program to be executed on the basis of the information in the “ref_to_program_id506”. When the program is specified, the information in the “program_name602” can specify itsprogram file241 to be executed.
• The network-connection-necessity determining unit124 in thesystem control unit101 reads out each “type_of_application604”, which shows its network connection necessity, for all applications that compose theprogram file241, and outputs it as a detection signal, which is stored into thememory120 or theHDD122 with an “application_ID605” that is an ID number specifying its application (S103) (the stored information is referred to as “network-connection-requirement indication information”; the “type_of_application604” and the “application_ID605” may be included in the detection signal).
• The present embodiment exemplifies that the information (the “type_of_application604”) stored in theprogram management file222 is used to determine whether theprogram file241 needs “network connection”; however, theactual program file241 itself may be analyzed to directly obtain information whether it needs network connection.
• Next, the effective memoryvolume determining unit126 in thesystem control unit101 obtains size information of contents to be downloaded for each application described above (S104). Explanations will be made under an assumption that the size information about the contents to be downloaded is stored in theexecution program file241. The effective memoryvolume determining unit126 appropriately obtains a free-space amount of theHDD122—that is a storage for downloading and provided in theplayback device100, outputs its free-space amount information as a volume detection signal, which is recorded into thememory120 or theHDD122 with the size information of the contents to be downloaded (the information is referred to as “size information of the download contents”).
• Then, thesystem control unit101 determines, according to the “network circuit information analysis result” (that is, the connection condition signal), the “network-connection-requirement indication information” (that is, the detection signal), and the “size information of the download contents” (that is, the volume detection signal) obtained in the steps S102, S103, and S104, whether to display the alarm screen shown inFIG. 7 and outputs its determination result as a determination signal (S105). More specifically, on the basis of the “network-connection-requirement indication information” (detection signal), it is checked whether the insertedoptical disk102 includes contents requiring the network connection. When it is confirmed that theoptical disk102 does not need the network connection, there is no need to display the alarm screen shown inFIG. 7, which makes a transition to a normal playback step (S108). Furthermore, even when the “network-connection-requirement indication information” (detection signal) indicates that the insertedoptical disk102 requires the network connection, but if the “network circuit information analysis result” (connection condition signal) guarantees enough circuit speed for downloading and if the “size information of the download contents” (volume detection signal) indicates that there is enough free space in the HDD for downloading, there is no need to display the alarm screen shown inFIG. 7, which makes a transition to a normal playback step (S108).
• On the other hand, when the “network-connection-requirement indication information” (detection signal) indicates that the network connection is necessary, and if the “network circuit information analysis result” (connection condition signal) indicates that the downloading itself cannot be performed or there is not enough circuit speed for downloading, the alarm screen shown inFIG. 7 is displayed (S106). Furthermore, when the “network-connection-requirement indication information” (detection signal) indicates that the network connection is necessary, and if the “size information of the download contents” (volume detection signal) indicates that there is not enough free space in the HDD, the alarm screen shown inFIG. 7 is displayed (S106).
• Displaying the alarm screen can let the user renew his awareness that the network is not ready. Theplayback device100 may also be configured to display the reasons (slow network circuit speed, shortage of memory for downloading or the like) that the network is not ready.
• Even when it is determined that theplayback device100 is not physically connected to the network circuit—such as disconnection of the circuit and unplugging of its connecting plug, they are displayed as reasons why the network is not ready. When no connection setting is performed for theplayback device100, such setting situation is displayed.
• There may be a high probability to display the alarm screen shown inFIG. 8 every time when theoptical disk102 is played back. To cope with such cases, the initial setting screen and the like may be set so that the alarm screen itself is prevented from being displayed. Even in such cases, the alarm screen may be displayed only at the first normal access after the network-circuit-information acquiring unit125 has become able to normally access the network.
• By selecting and pushing down a ‘continue current playback mode’button801 or a ‘change to non-network ready mode’button802 on the alarm screen, it is determined whether to change to the non-network playback mode (S107).
• When the ‘continue current playback mode’button801 is pushed through theoperation unit130, operations are changed into a playback step in the normal playback mode (S108). Then, thesystem control unit101 executes the program files241 that is developed in thememory120 for playing back. If there exist stream information files231 linked from the program files241, the stream information files231 that have been coded/compressed are decoded to be video/audio-outputted to thedisplay115.
• When the ‘change to non-network-ready mode’button802 is pushed through theoperation unit130, a network readiness flag contained in the system register set123 is changed to OFF (network is not ready) (S109). After that, playback operations similar to those described above are performed in the non-network-ready mode (S110).
• As described above, by changing the network readiness flag in the system parameters to OFF (the network is not ready) for playing back, theoptical disk102 can be played back while a playback path independent of network connection is selected.
• AlthoughEmbodiment 1 exemplifies that the alarm screen is displayed before a program title is played back, the screen may be displayed when inserting theoptical disk102 or just before executing an application that requires network connection. Whether or not the alarm screen is displayed may be determined only by the evaluation of the “network circuit information analysis result” (connection condition signal) (S102) shown inFIG. 9, without the evaluation of the “network-connection-requirement indication information” (detection signal) (S103) and the “size information of the download contents” (volume detection signal) (S104) shown inFIG. 9; whether or not to display the alarm screen may be determined according to a combination of some of those signals. In addition, by setting on the initial setting screen the options to be selected in S107, the options may be automatically selected without displaying the alarm screen shownFIG. 8.
• If configuring the device according toEmbodiment 1, whether the optical disk needs network connection is checked before the program title is played back, so that its check results can be automatically displayed on the display. Therefore, the user can quickly see at a glance whether an optical disk needs network connection, or in advance whether the environment is not in a network-ready state. Furthermore, when the playback mode of theplayback device100 is changed to the non-network-ready mode on the alarm screen, the device has an effect that the user can continue to watch the program title at ease without interruption of playback of the title due to such a reason that downloading cannot be performed during playback of the optical disk.
• That is, before playing back the optical recording medium that needs network connection, the playback device determines whether the network circuit can be used; and when it cannot be used, the device shows the fact on the alarm display or the like so that the user can easily confirm them. The user can see at a glance and in advance whether its contents need network connection and the reasons why the network is not ready. Thus, it is possible to reduce possibility of operations that are fundamentally unnecessary for users.
• Furthermore, because the device is configured so that the device can recognize in advance the amount of free space in a storage provided in the device to record downloaded contents and the amount of information to be downloaded, the device can prevent a malfunction, such as a download halt due to shortage of the amount of free space in the storage, from occurring.
• When the network circuit is not ready for the playback device but playback is performed with respect to an optical disk including programs requiring network connection, the device can automatically change its mode to the one independent of the network. The device can play back the optical disk according to a playback path that does not connect to the network; therefore, the device does not unnecessarily access network resources every time when the optical disk is played back.
• Information that correlates the network readiness flags to the optical disks having been played back may be stored in the playback device100 (for example, the HDD122). Thereby, when the optical disk that has been once played back is played back again, the mode can be determined by referring to what mode it was played back in.
• Furthermore, theplayback device100 may be configured in such a way that after playing back the contents the device restores the network readiness flag, which has been modified in S109, from OFF to ON.

Claims (1)

1. A playback device that, when playing back an MPEG-2 compressed and coded video stream recorded on a recording medium, obtains data necessary for the playback through a network, the playback device comprising:

a network-connection-necessity determining unit that, when the video stream is played back, determines whether it is necessary to obtain the data through the network;

a network-circuit-information acquiring unit acquires network circuit information, which is information used as a basis for determining the necessity of obtaining the data through the network;

a system control unit that determines whether or not to connect to the network on the basis of an analysis result of the network circuit information outputted from the network-circuit-information acquiring unit and network-connection-requirement indication information outputted from the network-connection-necessity determining unit; and

a video decoder that, according to a determination signal from the system control unit, plays back the video stream using the data obtained through the network or plays back the video stream without obtaining the data,

wherein the video stream is an elementary stream composed of packets and to be accessed in units of GOPs, and

the video decoder performs random-access playback by connecting to a server through the network based on the determination signal and obtaining playback control information from the server.

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