JP2008109188A - Content distribution system, peer, and center server - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a content distribution system that enables a user to view a selected high-quality content immediately when desiring to view it. <P>SOLUTION: Each of peers P1 stores a plurality of head files which correspond to portions of the whole file composed of data from a head to the end of a content and data within a predetermined range from the head of the content. A peer P1 starts the reproducing of the content C1 selected by the user. Since the peer P1 stores only the head file of the content C1, the peer P1 acquires the remaining portion file of the content C1 from a peer P3 which holds the whole file of the content C1 during the reproduction of the content C1 on the basis of content information about the location of the whole file of the content. Acquired data are reproduced one after another. Consequently, the user of the peer P1 can view the desired content C1 immediately and to the end without any break. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a content distribution system, a peer, and a center server, and more specifically, a peer-to-peer type content distribution system including a plurality of peers that can be connected to each other and a center server connected to the plurality of peers. And a peer and a center server used therefor.

  Many systems for distributing contents such as music and movies on the Internet have appeared. In particular, in a peer-to-peer type content distribution system that has recently been flourishing, file transfer loads are distributed to each peer in order to distribute content between peers. Therefore, content can be distributed to far more peers than a client server type content distribution system.

  By the way, there are a streaming method and a download method as content distribution methods. In the streaming method, each peer plays while receiving streaming distribution of the content, so that the user can view the content immediately when he / she wants to view it. However, since the streaming method is limited in bandwidth between peers, high-quality content cannot be distributed.

  On the other hand, since the download method generally reproduces the content after downloading all the data from the beginning to the end of the content, the high-quality content can be viewed without being restricted by the bandwidth between the peers.

However, in the download method, it is necessary to download in advance the entire file that is data from the beginning to the end of the content. Therefore, if there is no entire file in the peer, the user cannot view the content immediately when it wants to view and download You have to wait for it to complete. If all data of a plurality of contents on the system is downloaded to the peer in advance, any contents can be viewed immediately, but it is unrealistic due to the capacity of the hard disk drive in the peer.
JP 2006-72432 A

  An object of the present invention is to provide a content distribution system that can be immediately viewed when it is desired to view selected high-definition content.

Means for Solving the Problems and Effects of the Invention

  The content distribution system according to the present invention is a peer-to-peer type, and includes a plurality of peers connected to each other and a center server connected to the plurality of peers. The peer includes peer storage means for storing a plurality of entire files of content and a plurality of head part files. Each of the plurality of whole files is composed of all data from the beginning to the end of the content. The head partial file corresponds to a part of the entire file stored in the other peer, and is data from the head of the content to a predetermined range. The center server includes server storage means for storing content information including the locations of a plurality of entire files. The peer further includes a head part obtaining unit, a reproducing unit, and a remaining part obtaining unit. Based on the content information, the head part acquisition unit acquires the head part file from the entire content file that is not stored in itself and is stored in the other peer, and stores it in the peer storage unit. The playback means starts playback of content selected from the plurality of contents stored in the peer storage means. The remaining portion acquisition means uses the data excluding the head portion file of the selected content during the playback of the content when the entire portion file of the selected content is not accumulated but the beginning portion file is accumulated. A remaining file is acquired from the other peer that accumulates the entire file of the selected content. Here, the content refers to, for example, a moving image or sound.

  In the content distribution system according to the present invention, the peer accumulates a plurality of head partial files corresponding to a part of the entire content file. Even if the peer does not have the entire file in advance, the user can view the desired high-quality content immediately if the first partial file is stored. Further, when the content of the first partial file is reproduced, the peer acquires the remaining file during the reproduction of the content and continues the reproduction. Therefore, the user can view desired high-quality content immediately and to the end.

  Preferably, the content information further includes a content reproduction time and a data size of the entire content file. The server storage unit further stores transfer rate information related to the transfer rate between the peers. The center server further includes a specifying unit, a head part size determining unit, and a registering unit. The specifying unit specifies, as a transfer source peer, a peer that stores the entire file of the predetermined content based on the location of the entire file in the content information. The head part size determining means is configured so that, based on the content information and the transfer rate information, the time for the transfer destination peer to acquire the remaining file of the predetermined content from the transfer source peer is shorter than the playback time of the predetermined content. The data size of the first partial file of the predetermined content is determined. The registration unit registers in the server storage unit the first partial file information in which the determined data size of the first partial file is associated with the transfer source peer and the transfer destination peer. The first part obtaining unit obtains the first part file from the transfer source peer based on the first part file information, and the remaining part acquisition unit obtains the remaining file from the transfer source peer.

  In this case, the data size of the first partial file is determined for each peer. Since the remaining file acquisition time is shorter than the content reproduction time, it is possible to prevent the content reproduction from being interrupted.

  Preferably, the content information further includes meta information of the content, and the server accumulating unit further accumulates selection condition information regarding the content selection condition acquired by each peer. The center server further includes priority list creation means. Based on the content information and the selection condition information, the priority list creating means creates a priority list that lists the priorities of contents from which each peer should acquire the first partial file, and registers it in the server storage means. The peer further comprises free capacity determining means for obtaining the free capacity of the peer storage means, and the head part obtaining means obtains the file head part in order of priority based on the priority list and the free capacity. Here, the meta information is information relating to details of the content, and specifically, for example, a title, a cast, a genre, a singer name, and the like.

  Since the capacity of the peer storage means is finite, it is difficult for each peer to hold the first partial file of all the contents existing on the content distribution system. By accumulating the first partial file in accordance with the priority list created based on the content selection condition, it is possible to store content that is likely to be selected in the peer.

  Preferably, the content information further includes content publication period information. The peer further includes a public period acquisition unit and a deletion unit. The public period acquisition unit acquires the public period information of the content stored in the peer storage unit from the center server. The deletion unit deletes the entire file and the first partial file of the content that has passed the release period based on the release period information.

  By sequentially deleting the contents that have passed the publication period, the peer can sequentially accumulate the first partial file or the entire file of the new contents.

  The peer according to the present invention is a peer used in the above-described content distribution system, and the center server according to the present invention is a center server used in the above-described content distribution system.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[overall structure]
Referring to FIG. 1, a content distribution system 1 includes peers (clients) P1 to P3 that can be connected to each other, and a center server 10 that can be connected to peers P1 to P3 (hereinafter also referred to as peers Pn). . That is, the content distribution system 1 is a hybrid peer-to-peer system. Each peer Pn can acquire content from other peers Pn. In FIG. 1, the number of peers Pn is three, but may be two, or may be three or more.

[Overview]
Referring to FIG. 2, a plurality of contents (the contents here are moving images composed of a plurality of frames) are stored in a hard disk drive (hereinafter referred to as HDD) 23 of each peer Pn. The accumulated content is divided into two types depending on the type of data. One is an entire file including all data (frames) from the beginning to the end of the content. The other one is data corresponding to the head portion of the entire file, that is, a head portion file composed of frames from the head of the content to a predetermined range. Each file (entire file and head part file) is a file having different contents. In general, the first partial file has a smaller data size than the entire file. Since each peer Pn has a plurality of head part files, it can hold more contents in advance than when all the contents are held as a whole file.

  The center server 10 accumulates content information related to the location of the content and selection condition information related to the selection condition of the content acquired by each peer, and based on these information, determines the priority order of the content to be acquired by each peer. Create an enumerated priority list.

  Based on the priority list created by the center server 10, the peer Pn acquires the first partial file from another peer Pn that stores the entire content file and registers it in the HDD 23.

  When the user of the peer P1 selects the desired content C1 and instructs the peer P1 to play back, the peer P1 immediately starts playing back the content C1 based on the first partial file of the content C1. That is, the user can view the content C1 immediately.

  Further, the peer P1 starts playing the top part file, and obtains data after the head part (hereinafter referred to as the remaining part file) from the other peers Pn (peer 3 in FIG. 2) in the entire content file. Play sequentially.

  As described above, since each peer Pn has in advance a head portion file of a plurality of contents that are likely to be selected by the user, the high-quality content selected by the user can be immediately viewed. Furthermore, since the remaining files are acquired during playback and sequentially played back, the content can be viewed to the end without interruption. Hereinafter, details of each component of the content distribution system 1 will be described.

[Center server]
The center server 10 manages content information and creates a priority list. Referring to FIG. 1, the center server 10 includes a CPU (Central Processing Unit) 11, a memory 12, and a hard disk drive (HDD) 13.

  The HDD 13 includes a content information management database (hereinafter referred to as DB) 131, a peer information management DB 132, and a head partial file information DB 133.

  As shown in FIG. 3, the content information management DB 131 registers information (content information) CI1 to CIm (m is a natural number) related to the content accumulated by the peers P1 to P3 in the content distribution system 1.

  Each content information CIm includes a field for registering a content ID for identifying the content Cm, a field for registering the data size of the entire file of the content Cm, and a field for registering the reproduction time of the content Cm. And have.

  The content information CIm further has a field for registering details of the content, that is, meta information of the content. The meta information is, for example, a title, cast, genre (action, comedy, horror, etc.), a keyword related to the content, and the like. The content information CIm further includes a field for registering the publication period information (publication start date and time and publication end date and time) regarding the content publication period, and identification of a peer that stores the entire file of the content as information indicating the location of the content And a field for registering information (P1, P2, etc.).

  The center server 10 updates the content information management DB 131 when new content is registered in the content distribution system 1 from the outside, or when each peer Pn acquires an entire file of new content.

  As shown in FIG. 4, information (peer information) PI <b> 1 to PI <b> 3 related to each peer in the content distribution system 1 is registered in the peer information management DB 132. Each peer information PI includes a peer ID (P1 to P3) for identifying the peer, a user name using the peer, a content ID of the content in which the entire file is stored, and a content ID of the content in which the first partial file is stored. Content ID.

  The peer information PI further includes selection condition information related to selection conditions of contents to be acquired by the peer PI. Specifically, the selection condition information includes a user's favorite genre, a disliked genre, and a free keyword. These pieces of selection condition information determine the priority order of the contents from which the first partial file is acquired.

The peer information PI further includes transfer rate information between the peers Pn. For example, the peer information PI1 includes transfer rate information between the peers P1 and P2 and transfer rate information between the peers P1 and P3. The transfer rate is obtained, for example, by each peer Pn periodically sending and receiving a ping to the other peer Pn.
As shown in FIG. 5, the first partial file information DB 133 includes the data size of the first partial file of each content C1 to Cm to be acquired by the peer serving as the transfer destination, and the peer ID of the peer Pn serving as the content transfer source. Is registered with the first partial file information associated with the transfer destination peer. For example, in the case of the content C1, the top partial file to be acquired by the peer P1 is 100 Mbytes from the top, and the transfer source peer is the peer P3. The data size of each head part file is calculated based on the playback time of the content Cm, the data size of the entire file of the content Cm, and the transfer rate with the transfer source peer so that the playback of the content Cm is not interrupted. Is done.

  The HDD 13 further stores a priority list for each peer Pn. As illustrated in FIG. 6, the priority list lists contents for which the peer Pn should acquire the first partial file in order of priority. The priority list is created based on the content information CIm and the selection condition information in the peer information PIn.

  The HDD 13 further stores a center server application 134. When the center server application 134 is loaded into the memory 12 and executed by the CPU 11, the center server 10 executes the operations described later.

[Peer]
Referring again to FIG. 1, each peer Pn includes a CPU 21, a memory 22, and an HDD 23. The HDD 23 stores a content DB 231 and a peer application 232.

  A plurality of contents are registered in the content DB 231. More specifically, a plurality of whole files and a plurality of head partial files are registered.

  The peer Pn loads the peer application 232 into the memory 22 and executes it by the CPU 21, thereby acquiring the first partial file and the remaining file from the other peer Pn, and distributing those files to the other peer Pn. . Also, new content is taken in from outside the other peers Pn.

  The HDD 23 further stores content information CIm and head portion file information of the content Cm (whole file and head portion file) registered in the content DB 231.

[Operation]
[Priority list creation process]
First, priority list creation processing by the center server 10 will be described. Referring to FIG. 7, for example, when an entire file of new content C10 that is not on content distribution system 1 is stored in peer P3, peer P3 creates content information CI10, and the created content information CI10, Peer information PI3 in which the content C10 is newly registered as the entire held file is transmitted to the center server 10. At this time, the center server 10 registers the transmitted content information CI10 in the content information management DB and registers the peer information PI3 in the peer information management DB 132.

  When it is determined that the content information management DB has been updated due to the registration of the new content information CI10 (YES in S101), the center server 10 determines the data size of the head portion file of the new content C10 (S102: head portion). File size determination process). As described above, with respect to the content Cm that the peer Pn intends to reproduce, when the peer Pn possesses only the first partial file of the content Cm, the peer Pn reproduces the remaining portion from the other peers Pn while reproducing the content Cm. Get the file. At this time, even when the reproduction of the first partial file is completed, the peer Pn sequentially reproduces data (frames) already acquired from the remaining files, thereby preventing interruption of the content Cm being reproduced. In order to realize such a reproduction method, the data size of the first partial file is determined by the following method.

  The head partial file size determination process is executed for each content Cm newly registered in the content distribution system 1. Referring to FIG. 8, the center server 10 first sets a peer to be calculated as a peer P1 (S1021). Subsequently, the center server 10 refers to the peer information management DB 132 and confirms that the peer P1 does not have the entire file of the content C10 (NO in S1022).

  Next, based on the peer information management DB 132, the center server 10 is a peer that holds the entire file of the content C10 and identifies a transfer source peer that distributes the file to the peer P1 (S1023 to S1025). The center server 10 first determines whether there are a plurality of peers that hold the entire file of the content C10 (S1023). Here, since the new content C10 is held only by the peer P3 (NO in S1023), the center server 10 identifies the peer P3 as the transfer source peer (S1025).

  The center server 10 reads the transfer rate α (Mbps) when data is distributed from the transfer source peer P3 to the peer P1 based on the transfer rate information in the peer information PI1 (S1026). Subsequently, the center server 10 calculates the data size of the first partial file of the content C10 to be stored by the peer P1 (S1027). At this time, the center server 10 reads the data size TS (Total Size) of the entire file of the content C10 and the reproduction time B (sec) of the content C10 from the content information CI10.

  When the peer P1 reproduces the content C10, in order to reproduce the content C10 without interruption, the remaining file obtained by removing the first part file from the entire file of the content C10 is downloaded at least within the reproduction time of the content C10. There is a need. That is, if the download time of the first partial file is D (sec) and the download time of the entire file is C (sec), the remaining file download time C-D (sec) must satisfy the following formula (1). There is.

CD (sec) <content C10 playback time B (sec) (1)
Here, the download time C of the entire file of the content C10 is calculated by the following equation (2).

C (sec) = Overall file data size TS (Mbytes) x 8 / α (2)
From the above, the center server 10 determines the download time D (sec) of the first partial file so as to satisfy Expression (1), and determines the data size (Mbytes) of the first partial file based on Expression (3). .

First partial data amount (Mbytes) = D (sec) x α / 8 (3)
If the data size of the first partial file is determined based on Expression (3), the content C10 is reproduced while the remaining file is being acquired during reproduction when the peer P1 starts to reproduce the first partial file of the content C10. When this is done, the content C10 can be reproduced to the end without interruption. After determining the data size of the first partial file, the center server 10 uses the determined first partial file data size and the transfer source peer (here, peer P3) as the first partial file information associated with the transfer destination peer P1. It is registered in the head partial file information DB 133 (S1028).

  After registration, the peer ID = P1 is incremented to P2 (S1029), the process proceeds to step S1022 (NO in S1030), and the data size of the first partial file of the content C10 for the peer P2 is determined.

  When the peer P2 is incremented to become the peer P3 (S1029), the center server 10 determines in step S1022 that the peer P3 stores the entire file of the content C10 (YES in S1022), and the process proceeds to step S1029. move on.

  When the center server 10 determines in step S1030 that the process has been executed for all the peers P1 to P3 on the content distribution system 1 (YES in S1030), the head partial file size determination process for the content C10 is terminated.

  If the content C10 is stored in advance in a plurality of peers (for example, peers P2 and P3), the center server 10 recognizes that there are a plurality of peers that accumulate the content C10 in step S1023 (YES in S1023). In this case, the center server 10 further selects one peer from a plurality of peers (P2 and P3) authorized in step S1023 (S1024), and specifies the selected peer as a transfer source peer. At this time, the center server 10 may select a higher transfer rate with the peer P1 or may select it at random.

  With the above method, the center server 10 calculates the data size of the first partial file and updates the first partial file information DB 133.

  Returning to FIG. 7, after executing the head part file size determination process, the center server 10 updates the priority list of each peer Pn (S104 and step S105). Hereinafter, the update of the priority list of the peer P1 will be described, but the priority list is similarly updated for the other peers (P2 and P3).

  First, the center server 10 reads selection condition information in the peer information PI1 of the peer P1. Subsequently, based on the selection condition information and the meta information in the content information CIm, the priority order of the contents to be downloaded from the head partial file is determined. For example, content whose meta information includes a keyword in the selection condition and whose genre included in the meta information matches the favorite genre in the selection condition is given top priority, and then the content whose meta information includes the keyword The contents are listed in the order of the contents in which the genre in the meta information matches the favorite genre in the selection condition, and the priority list is updated. The updated priority list is stored in the HDD 13 (S105).

  With the above operation, each time new content is registered in the content distribution system 1, the center server 10 determines the data size of the first partial file of the newly registered content and updates the priority list.

  On the other hand, when the user of the peer Pn changes the selection condition, the peer Pn transmits peer information PIn including the updated selection condition information to the center server 10. The center server 10 updates the peer information PIn in the peer information management DB 132 (YES in S103). At this time, the center server 10 updates the priority list of the peers Pn of the updated peer information PIn (S104 and S105). In short, even when the user changes the selection condition, the priority list is updated.

[First partial file acquisition processing]
The peer Pn executes a content deletion process, which will be described later, and then executes a head partial file acquisition process. Hereinafter, the process of acquiring the first partial file in the peer P1 will be described. Referring to FIG. 9, peer P1 first detects the free capacity of its own HDD 23 (S201). The detected free space information is stored in the memory 22.

  Subsequently, the peer P1 requests and acquires the first partial file information (corresponding to 100 in FIG. 5) having the transfer destination as the peer P1 among the first partial file information (S202). Subsequently, the peer P1 requests and acquires the disclosure period information of the contents C1 to Cm in the content information management DB 131 from the center server 10 (S203). The peer P1 further acquires a priority list of the peer P1 from the center server 10 (S204). The information acquired in steps S202 to S204 is stored in the memory 22.

  After acquiring the above-described information from the center server 10, the peer P1 acquires the first partial file of the content not registered in the content DB 231 (S205 to S212). The peer P1 resets the priority number counter j so that j = 1 (S205). Subsequently, the peer P1 refers to the priority order list, specifies the content ID (C1 in FIG. 6) with the priority number j (= 1), and executes the download process (S220).

  In the download process, first, based on the publication period information, it is determined whether or not the content is currently being published (S206). If the current time (that is, when the first partial file acquisition process is executed) is outside the public period (NO in S206), the peer Pn increments the priority number counter j without downloading the first partial file, and j = 1 (S212), and return to step S206 (NO in S213). On the other hand, when the current time is within the publication period (YES in S206), the peer Pn further determines whether the preceding partial file or the entire file of the content with the priority number j has already been registered in the content DB 231 (S207). . If it has already been registered (NO in S207), it is not necessary to download, so the process proceeds to step S212.

  As a result of the determination in step S206, if the first partial file and the entire file of the content are not registered (YES in S207), the peer Pn uses the content ID of the priority number j (= 1) from the first partial file information acquired in step S202. The data size (= 100 Mbytes) of the preceding partial file corresponding to (= C1) is read (S208), and it is determined whether or not the read data size satisfies the following expression (4) (S209).

Data size of first partial file <Free space of HDD 23−γ (4)
Here, γ is a predetermined capacity (mbytes), and is preferably larger than at least the average data size of the entire content file.

  If Expression (4) is not satisfied (NO in S209), the process proceeds to step S212 without downloading the first partial file. On the other hand, when the expression (4) is satisfied, the peer Pn downloads the first partial file corresponding to the corresponding data size (= 100 Mbytes) in the first partial file from the transfer source peer (= peer P3) in the first partial file information. (S210). When the head part file of the content C1 is downloaded, the peer P1 acquires the content information of the content C1 from the center server and stores it in the HDD 23 (S211). At this time, the publication period information of the content C1 is also stored. In addition, information regarding the transfer source peer (peer P3) of the content C1 among the head partial file information acquired in step S202 is also stored.

  After downloading, the priority number counter j is incremented to j = 2, and the download process (S220) is executed for all the contents registered in the priority order list. When the download process (S220) is executed for all contents registered in the priority list (YES in S213), the top partial file acquisition process is terminated.

  Through the above operation, each peer P1 obtains the first partial file of new content as needed based on the free capacity of the HDD 23, and prepares for the user's reproduction instruction.

[Playback processing]
A reproduction process in the case where content is reproduced by the peer Pn will be described. When a reproduction instruction for a desired content is received from the user and the entire file of the content for which the reproduction instruction has been received is not accumulated, but only the first partial file is accumulated, the peer Pn The content playback is started based on the above. The peer Pn further downloads the remaining files after the first partial file during the reproduction of the content. At this time, the remaining files are downloaded and new frames are sequentially stored in the content DB 231 while the stored frames are sequentially reproduced. Hereinafter, although the reproduction process of the content C1 at the peer P1 will be described, the other peers P2 and P3 perform the same operation.

  Referring to FIG. 10, first, peer P1 displays a list of contents (contents of the entire file and contents of the first partial file) stored in HDD 23 on a display (not shown) (S301). When the user selects the desired content C1 in the content list and inputs a playback instruction for the selected content C1, the peer P1 identifies the selected content C1 (S302) and executes playback of the content C1 (S302). S303 to S311).

  The peer P1 specifies the data size stored in the content DB 231 for the specified content C1, stores the start position of the stored data (frame) in the memory 22 as a playback point, and The end position is stored in the memory 22 as a write pointer (S303). After storing the playback pointer and the write pointer, the peer P1 starts playback (S304). That is, the stored data (frame) is sequentially read out to the memory 22 and reproduction is started from the first frame. Each time the peer P1 plays a frame, it shifts the playback pointer.

  When reproduction is started, the peer P1 determines whether or not the write pointer is positioned before the end position of the data size of the entire file (S305). Here, the end position of the entire file is determined based on the data size of the entire file in the content information (stored in S211) of the content C1 stored in the HDD.

  When the write pointer is before the end position of the entire file (YES in S305), the content C1 is not the entire file but the head partial file. Therefore, the peer P1 specifies the transfer source peer of the remaining file of the selected content as the peer P3 based on the transfer source peer information stored in step S211, and requests the transfer source peer P3 to distribute the remaining file. The acquisition of the remaining file is started (S306). At this time, the peer P1 requests the peer P2 to deliver from the frame arranged next to the frame indicated by the write pointer based on the write pointer. The peer P2 delivers the remaining files sequentially from the requested frame. Each time the peer P1 registers a new frame in the content DB 231, the newly registered frame position is stored in the memory 22 as a write pointer.

  Subsequently, the peer P1 determines whether or not the playback pointer is in front of the write pointer (that is, the playback pointer is positioned between the head frame position and the write pointer position) (S307). If it is in front (YES in S307), the peer P1 sequentially reads the content frames from the content DB 231 to the memory 22 and continues the reproduction (YES in S308).

  During playback, the peer P1 monitors whether or not the playback pointer is before the end position of the entire file (S310). If it is in the foreground (YES in step S310), the content has not been reproduced to the end, so the process returns to step S307, and the reproduction is continued while downloading.

  When the playback pointer reaches the end position of the entire file in step S310 (NO in S310), the peer P1 completes playback. At this time, since the peer P1 stores the entire file of the content that has been reproduced in the content DB 231, the peer information PI1 in which the content in which the entire file has been stored is updated is transmitted to the center server 10 (S311).

  If the playback pointer has passed the light pointer during playback (NO in S307), the peer P1 stops playback because there is insufficient data to be played back (S312). For example, such a situation may occur when the download of the remaining file is delayed due to the trouble of the transfer source peer P3. After the reproduction is stopped once, as a result of acquiring a new frame by downloading, when the reproduction pointer is in front of the write pointer (YES in S307), the reproduction is started (NO in S308, step S309).

  If the write pointer is the same as the end position of all data in step S305 (NO in S305), since the peer P1 stores the entire file of the specified content, the download of the content can be started without starting the download. Continue playback.

  As described above, the peer Pn stores in advance the top partial files of a plurality of contents. Therefore, the peer Pn can immediately reproduce the content Cm selected by the user. In addition, during the reproduction, the remaining file is received and sequentially registered in the content DB 231 and the registered frames are sequentially reproduced. Therefore, the content can be reproduced to the end without interruption.

[Content deletion processing]
Of the contents (entire file and head part file) stored in the contents DB 231 of each peer Pn, contents that have passed the public period are deleted. As a result, the first partial file of the new content and the remaining file of the content that has received the reproduction instruction can be sequentially stored in the content DB 231. Hereinafter, the content deletion process will be described.

  Referring to FIG. 11, peer Pn creates a list of content registered in content DB 231 and stores it in memory 22 (S401). The created content list is shown in FIG. The content list includes a content number and a content ID.

  The peer Pn sets the counter i = 1 (S402), and specifies the content ID (= C3) of the content number 1. Subsequently, the peer Pn refers to the disclosure period information in the content information CI3 of the specified content C3, and determines whether or not the current time (that is, when the content deletion process is executed) has passed the disclosure period. (S403). Note that the disclosure period information is stored in the HDD 23 in S211 in FIG. If it has passed (YES in S403), the corresponding content file (entire file or head part file) is deleted (S404). If NO in step S403 and after step S404, the counter i is incremented to i = 2 (S405), and the process proceeds to step S403 to execute the same processing for the content with content number 2. In short, the operations after step S403 are executed for all contents in the content list. After all the contents are executed (YES in S406), the peer information PIn in which the information related to the registered contents is updated is transmitted to the center server 10 (S407).

  While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

It is a functional block diagram which shows the whole structure of the content delivery system by embodiment of this invention. It is the schematic which shows the operation | movement outline | summary of the content delivery system shown in FIG. It is a figure which shows the data structure of the content information management database which the center server shown in FIG. 1 accumulate | stores. It is a figure which shows the data structure of the peer information management database which the center server shown in FIG. 1 accumulate | stores. It is a figure which shows the data structure of the head part file information database which the center server shown in FIG. 1 accumulate | stores. It is a figure which shows the priority list | wrist which the center server shown in FIG. 1 accumulate | stores. It is a flowchart which shows the detail of the priority list creation process by the center server shown in FIG. It is a flowchart which shows the detail of operation | movement of step S102 in FIG. It is a flowchart which shows the detail of the head part file acquisition process by the peer shown in FIG. It is a flowchart which shows the detail of the reproduction | regeneration processing by the peer shown in FIG. It is a flowchart which shows the detail of the content deletion process by the peer shown in FIG. It is a figure which shows the content list produced by step S401 in FIG.

Explanation of symbols

1 Content Distribution System 10 Center Server 131 Content Information Management Database 132 Peer Information Management Database 133 First Partial File Information Database 231 Content Database Pn Peer

Claims (9)

A peer-to-peer type content distribution system comprising a plurality of peers connected to each other and a center server connected to the plurality of peers,
The peer is
A plurality of entire files each consisting of all data from the beginning to the end of the content, and each corresponding to a part of the entire file stored in the other peer, data from the beginning of the content to a predetermined range Comprising a peer storage means for storing a plurality of first partial files,
The center server is
Server storage means for storing content information including the locations of the plurality of whole files;
The peer further includes
Based on the content information, a head part obtaining unit that obtains a head part file from a whole file of contents that are not stored by itself and is stored in the other peer and stores the head part file in the peer storing unit;
Playback means for starting playback of content selected from a plurality of contents stored in the peer storage means;
When the entire file of the selected content is not accumulated and the first partial file is accumulated, the remaining portion that is data excluding the first partial file among the entire file of the selected content during the reproduction of the content A content distribution system comprising: a remaining portion acquisition unit configured to acquire a file from the other peer that accumulates the entire file of the selected content. The content distribution system according to claim 1,
The content information further includes a playback time of the content and a data size of the entire file of the content,
The server storage means further includes
Storing transfer rate information relating to the transfer rate between the peers;
The center server further includes
Identifying means for identifying, as a transfer source peer, a peer that accumulates the entire file of the predetermined content based on the location of the entire file in the content information;
Based on the content information and transfer rate information, the time for the peer serving as a transfer destination to acquire the remaining file of the predetermined content from the transfer source peer is shorter than the playback time of the predetermined content. Start part size determining means for determining the data size of the start part file of the predetermined content;
Registering means for registering in the server storage means head part file information associating the determined data size of the head part file with the transfer source peer and the transfer destination peer;
The head part acquisition means acquires the head part file from the transfer source peer based on the head part file information,
The content distribution system, wherein the remaining part acquisition unit acquires the remaining file from the transfer source peer. The content distribution system according to claim 1 or 2,
The content information further includes meta information of content,
The server storage means further includes
Accumulate selection condition information on the selection conditions of content acquired by each peer,
The center server further includes
Based on the content information and the selection condition information, a priority list creating unit that creates a priority list that enumerates the priorities of the contents from which each peer should acquire the first partial file and registers the priority list in the server storage unit With
The peer further includes
Free space determining means for determining the free capacity of the peer storage means;
The content distribution system according to claim 1, wherein the head part acquisition means acquires the file head part in order of priority based on the priority list and the free space. The content distribution system according to any one of claims 1 to 3,
The content information further includes content publication period information,
The peer further includes
Publication period acquisition means for acquiring the publication period information of the content stored in the peer storage means from the center server;
A content distribution system comprising: deletion means for deleting an entire file and a head part file of content that has passed the publication period based on the publication period information. The peer in a peer-to-peer type content distribution system comprising a plurality of peers connected to each other and a center server connected to the plurality of peers,
A plurality of entire files each consisting of all data from the beginning to the end of the content, and each corresponding to a part of the entire file stored in the other peer, data from the beginning of the content to a predetermined range Peer accumulation means for accumulating a plurality of first partial files,
Based on the content information stored in the center server, which is information related to the location of the entire files of the plurality of contents, from the entire files of the contents that have not been stored and that have been stored in the other peers A head part acquisition means for acquiring a head part file and storing it in the peer storage means;
Playback means for starting playback of content selected from a plurality of contents stored in the peer storage means;
When the entire file of the selected content is not accumulated but the first partial file is accumulated, the remaining portion that is data excluding the first partial file among the entire file of the selected content during the reproduction of the content A remaining portion acquiring unit that acquires a file from the other peer that accumulates the entire file of the selected content. The peer according to claim 5, wherein
The content information further includes meta information of content,
The peer further includes
Free space determining means for determining the free capacity of the peer storage means;
The head portion acquisition means is created by the center server based on the content information accumulated by the center server and selection condition information on the content selection conditions acquired by each peer, and each peer stores a head portion file. A peer characterized in that a file head portion is acquired in order of priority based on a priority list that lists priorities of contents to be acquired. A peer according to claim 5 or claim 6,
The content information further includes content publication period information,
The peer further includes
Publication period acquisition means for acquiring the publication period information of the content stored in the peer storage means from the center server;
A peer comprising: deletion means for deleting an entire file and a first partial file of content that has passed the publication period based on the publication period information. A plurality of entire files each consisting of all data from the beginning to the end of the content, and each corresponding to a part of the entire file stored in the other peer, data from the beginning of the content to a predetermined range A center server in a peer-to-peer type content distribution system comprising a plurality of peers for storing a plurality of head part files and a center server connected to the plurality of peers,
Server storage means for storing content information including the location of the plurality of whole files, the reproduction time of the content, and the data size of the whole file of the content, and transfer rate information regarding the transfer rate between the peers;
Identifying means for identifying a transfer source peer that accumulates the entire file of the predetermined content based on the location of the entire file in the content information;
Based on the content information and the transfer rate information, the time when the peer as the transfer destination acquires the remaining file from the entire file of the predetermined content excluding the head part file from the transfer source peer is Head portion size determining means for determining the data size of the head portion file of the predetermined content so as to be shorter than the reproduction time of
Information for the peer to acquire the head part file, the head part file information associating the determined data size of the head part file with the transfer source peer and the transfer destination peer. A center server comprising registration means for registering in the server storage means. The center server according to claim 8, wherein
The content information further includes meta information of content,
The server storage means further includes
Accumulate selection condition information on the selection conditions of content acquired by each peer,
The center server further includes
Based on the content information and the selection condition information, a priority list creating unit that creates a priority list that enumerates the priorities of the contents from which each peer should acquire the first partial file and registers the priority list in the server storage unit A center server comprising:

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