JP2011248715A - Node device, node processing program and content deletion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a node device, node processing program and content deletion method capable of performing rapidly a reproduction output of a content constituting a compound content even if the content for constituting the compound content is deleted from a cache area for storing the content.SOLUTION: A node device stores at least one of a first content constituting a compound content and output in a time series, and a second content needed for controlling output of the first content. The node device deletes the first content preferentially of the contents constituting the compound content, in a case that it deletes the content stored.

Description

  The present invention relates to a technical field of a Peer to Peer (P2P) type distribution system including a plurality of node devices that can communicate with each other via a network.

  In recent years, in a peer-to-peer type distribution system, a distribution system is known in which each piece of divided content data obtained by dividing one piece of content data is distributed and stored in a plurality of node devices (see Patent Document 1). The data amount of one divided content data is, for example, several megabytes. Hereinafter, the content data is referred to as “content”. In the distribution system disclosed in Patent Document 1, a unique content ID is assigned to each divided content. Each node device can acquire divided content in units of divided content from other node devices based on the content ID of the divided content.

  In a peer-to-peer distribution system, content acquired by a node device is stored and stored in a predetermined cache area in a storage unit provided in the node device. Since the storage capacity of this cache area is limited, each node device, for example, deletes a part of content from the cache area when the total amount of stored content exceeds a certain amount. Is supposed to do.

JP 2008-047065 A

  By the way, in recent years, composite content that is configured by, for example, SWF (Shockwave Flash) or the like and can be played back by Flash Player is known. This composite content is composed of, for example, a resource file composed of moving images and the like, and a control file necessary for output control of the moving images registered in the resource file. When such composite content is input to a peer-to-peer distribution system, the resource file and the control file are stored in one of the node devices as one content. In this case, it is assumed that the control file is deleted from the cache area among the resource file and the control file constituting the composite content by the content deletion process.

  However, if the control file has been deleted from the cache area, the node device needs to acquire the control file from another node device when reproducing the corresponding resource file. In the reproduction of the resource file, the control file is first required in the composite content. Therefore, in a case where the node device acquires a control file from another node device during the reproduction of the resource file, there is a problem that it takes time to reproduce the resource file.

  Therefore, the present invention has been made in view of the above-described problems and the like, and even when the content constituting the composite content is deleted from the cache area for storing the content, the playback and output of the content constituting the composite content can be quickly performed. It is an object to provide a node device, a node processing program, and a content deletion method that can be performed.

  In order to solve the above-described problem, the invention described in claim 1 includes a plurality of node devices that can communicate with each other via a network, one or more contents are stored in one or more node devices, and each node device Is the node device in the distribution system configured to acquire the content stored in another node device based on unique identification information given to each of the content, and is configured from a plurality of content Storage means for storing at least one of the first content output in time series in the composite content and the second content necessary for output control of the first content, and the storage means When deleting the stored content, priority is given to the first content among the content constituting the composite content. Characterized in that it comprises a deletion means for deleting, the Te.

  According to a second aspect of the present invention, in the node device according to the first aspect, the storage unit includes any one of a plurality of the first content and the second content constituting the composite content. It is stored at least, and the deletion means preferentially deletes the first content having a large amount of data among the plurality of first contents.

  According to a third aspect of the present invention, in the node device according to the first or second aspect, the storage unit includes a content composed of a moving image and a content composed of a still image or text as the first content. Are stored, and the deleting unit deletes the content preferentially from the content composed of the moving image rather than the content composed of the still image or the text.

  According to a fourth aspect of the present invention, in the node device according to any one of the first to third aspects, the storage means includes the first content, the second content, and the second content constituting the composite content. And at least a third content in which identification information assigned to each content constituting the composite content, in which identification information for searching a plurality of contents distributed and stored in a plurality of node devices is described, is stored. The deleting means preferentially deletes the first content from among the contents constituting the composite content.

  According to a fifth aspect of the present invention, in the node device according to any one of the first to fourth aspects, the deletion unit deletes the second content that is not used for a predetermined time.

  According to a sixth aspect of the present invention, in the node device according to any one of the first to fifth aspects, the second content includes a file for controlling an output timing of the first content, and the first content. It is characterized by comprising at least one of files for performing display control for displaying content on a predetermined display.

  The invention according to claim 7 includes a plurality of node devices that can communicate with each other via a network, one or more contents are stored in one or more node devices, and each node device is assigned to each of the contents. Among the composite contents composed of a plurality of contents, the computer included in the node apparatus in the distribution system configured to acquire the content stored in another node apparatus based on the unique identification information. A step of storing at least one of the first content output in time series and the second content necessary for output control of the first content, and deleting the stored content And preferentially deleting the first content out of the contents constituting the composite content. A node processing program for execution.

  The invention according to claim 8 includes a plurality of node devices that can communicate with each other via a network, wherein one or more contents are stored in one or more node devices, and each node device is assigned to each of the contents. A content deletion method in a distribution system configured to acquire the content stored in another node device based on the unique identification information, wherein the node device is composed of a plurality of contents And storing at least one of the first content output in time series and the second content necessary for output control of the first content, and the node device Among the contents constituting the composite content, the first content is deleted when the content is deleted. A step of deleting previously to, to include the features.

  According to the first, seventh, and eighth aspects of the present invention, when deleting the content constituting the composite content from the content cache area, the first content output in time series is preferentially deleted. The second content necessary for the output control of the first content can be left in the cache area. Therefore, it is possible to quickly reproduce and output a plurality of contents constituting the composite contents.

  According to the second aspect of the present invention, it is possible to store more content in the cache area by preferentially deleting from the first content having a large amount of data, so that the content cache area is effectively used. can do.

  According to the third aspect of the present invention, it is possible to store more content in the cache area by preferentially deleting from the content composed of moving images with a large amount of data. It can be used effectively.

  According to the fourth aspect of the present invention, the third content in which information for acquiring each content constituting the composite content is described can be left in the cache area. Accordingly, it is possible to quickly reproduce and output the content constituting the composite content.

  According to the fifth aspect of the present invention, the second content that has not been used for a predetermined period can be efficiently deleted.

It is a figure showing an example of outline composition of a contents distribution system concerning this embodiment. It is a block diagram which shows the example of a schematic structure of the node Nn. It is a conceptual diagram which shows the mode from injection | pouring of composite content to deletion. It is a flowchart which shows the process in the control part 11 of node N1.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described below is an embodiment when the present invention is applied to a content distribution system.

[ 1. Content distribution system configuration and operation overview ]
First, with reference to FIG. 1, the structure and operation | movement outline | summary of the content delivery system which concerns on this embodiment are demonstrated. FIG. 1 is a diagram illustrating a schematic configuration example of a content distribution system according to the present embodiment.

  As shown in FIG. 1, the content distribution system S according to the present embodiment includes a content management server MS and a plurality of node devices Nn (n = 1, 2, 3,... K). . The content management server MS and each node device Nn are connected to a network NW composed of the Internet or the like. The node device is hereinafter referred to as “node”. Each node Nn is assigned a node ID that is unique identification information. Further, the content management server MS manages the originals of all the contents that can be used in the content distribution system S.

  In the content distribution system S, an overlay network ON is formed. The overlay network ON is a logical network that forms a virtual link including a plurality of nodes Nn that can communicate with each other via the network NW. The overlay network ON is realized by a specific algorithm, for example, an algorithm using a distributed hash table. Hereinafter, the distributed hash table is referred to as “DHT (Distributed Hash Table)”. Note that a routing table using DHT is known in Japanese Patent Application Laid-Open No. 2006-197400 and the like, and thus detailed description thereof is omitted.

  Then, the content management server MS inputs the content uploaded from, for example, the content provider's terminal into the content distribution system S. Here, the input of content refers to saving new content in one or more nodes Nn participating in the overlay network ON. The node Nn that stores the content is hereinafter referred to as a “content holding node”. Each input content is given a content ID which is unique identification information. The content ID is for searching a plurality of contents distributed and stored in a plurality of nodes Nn. Each node Nn can acquire the content stored in the other node Nn via the overlay network ON based on the content ID. The content acquired in this way is stored in the node Nn. Thus, the content is distributed and stored in a plurality of content holding nodes in the overlay network ON.

  Further, in the content distribution system S according to the present embodiment, composite content composed of a plurality of contents may be input. The composite content is a plurality of contents collected into one file by archiving, for example. The input composite content is managed by the content management server MS. Content constituting the composite content includes first content output in time series and second content necessary for output control of the first content. In the following description, a resource file will be described as the first content, and a control file will be described as the second content.

  Here, examples of the resource file include a moving image file, an image file, an audio file, and a text file. The moving image file is content composed of moving images. Examples of the moving image file include an FLV file. An image file is content composed of still images. Examples of the image file include a BMP file, a JPEG file, and a GIF file. The audio file is content configured by audio. Examples of the audio file include an MP3 file. A text file is content composed of text. An example of the text file is an XML file. Further, the number of resource files constituting one composite content is not limited to one and may be plural.

The control file is composed of, for example, at least one of the following files (i) and (ii).
(I) A file for controlling the output timing of resources such as moving images registered in the resource file (ii) For performing display control for displaying resources such as images and text registered in the resource file on a predetermined display File Here, display control includes, for example, control of the display position of an image or text. The display control may include image enlargement / reduction control and image resolution control.

  A specific example of the control file is a SWF file. In the SWF file, a script for controlling output of a resource such as a moving image is described in a language called Action Script. With this script, it is possible to control the output timing of resources such as moving images registered in the resource file. In other words, the output timing indicates the reproduction start position of each moving image or the like. The playback start position is, for example, the time that has elapsed since the start of the output of the moving image registered in the resource file. The time at which playback for each video is started may be registered in the resource file. If the resource is an image or text, the display position on the screen can be controlled by this script. In other words, the control file may include information indicating the display position of the image or text on the display screen. Furthermore, the control file may include information indicating the output timing of the image or text, or the reproduction start position described above. If the resource is an image, enlargement or reduction of the image can be controlled by the script. If the resource is an image, the resolution of the image can be controlled by the above script. In other words, the control file may include information indicating the enlargement or reduction of the image or the resolution of the image. Further, the control file may include information related to a user interface for performing output control of the resource file in accordance with a user operation instruction. Further, the number of control files constituting one composite content is not limited to one, and there may be a plurality of control files. However, in the case of the SWF file, there is only one main SWF file, and the other SWF files are sub SWF files. The sub SWF file is called and used by a script described in the main SWF file. The resource file can also be stored in the SWF file. The resource file may have a small file size and can be stored in the SWF file.

  Content other than composite content is made up of resource files. The content other than the composite content is hereinafter referred to as “normal content”. The normal content includes a WMV file.

  A unique content ID is assigned to each of the resource file and the control file constituting the composite content. For example, the content ID is described in the header of the resource file and the control file. Thus, the resource file and the control file to which the content ID is assigned are input into the content distribution system S as one content.

  By the way, the content ID and the file name of each file constituting the composite content are described in, for example, a meta file of the composite content. The composite content metafile is a file for searching and acquiring each file constituting the composite content via the overlay network ON. Further, the content ID of the composite content is assigned to the composite content metafile. The meta file of the composite content to which the content ID is assigned is input into the content distribution system S as one content. Note that the composite content metafile can be positioned as one file constituting the composite content, similar to the resource file and the control file.

  Information indicating the location of the content is stored as index information in the node Nn that manages the location of the content. As this content, each file mentioned above also corresponds. The node Nn that manages the location of the content is hereinafter referred to as a “root node”. This index information includes a set of the node information of the content holding node storing the content and the content ID of the content. The node information includes the IP address, port number, and node ID of the content holding node. For example, the root node is determined to be the node Nn to which the node ID closest to the content ID is assigned. The node ID closest to the content ID is, for example, the node ID with the highest number of upper digits that match.

  When acquiring the composite content, the node Nn first acquires the metafile of the composite content from the content holding node via the overlay network ON based on the content ID of the composite content. Next, the node Nn acquires each file from the content holding node via the overlay network ON based on each content ID described in the acquired composite content metafile. Note that the node Nn can also acquire each file constituting the composite content from the content management server MS. The metafile, resource file, and control file acquired as described above are stored and saved in a content cache area provided in a storage unit provided in the node Nn. In this embodiment, when a file is deleted from the content cache area, the node Nn preferentially deletes the resource file among these files.

[ 2. Configuration and function of node Nn ]
Next, the configuration and function of the node Nn will be described with reference to FIG.

  FIG. 2 is a block diagram illustrating a schematic configuration example of the node Nn.

  As shown in FIG. 2, the node Nn includes a control unit 11, a storage unit 12, a buffer memory 13, a decoder unit 14, a video processing unit 15, a display unit 16, an audio processing unit 17, a speaker 18, a communication unit 19, and an input. The unit 19a is provided. The control unit 11, the storage unit 12, the buffer memory 13, the decoder unit 14, the video processing unit 15, the display unit 16, the audio processing unit 17, the communication unit 19, and the input unit 19a are connected to each other via a bus 19b. Yes. As the node Nn, a personal computer, an STB (Set Top Box), a TV receiver, a karaoke device, or the like is applicable.

  The storage unit 12 is composed of, for example, a hard disk drive. The storage unit 12 stores an operating system, a P2P program, a Flash program (Flash Player), and the like. Further, content acquired from a content holding node or the like is stored and saved in a content cache area provided in the storage unit 12. Note that acquisition date information indicating the date when the content was acquired from a content holding node or the like is added to the content in the content cache area. Furthermore, usage date information indicating the date when the content is used by the user is added to the content in the content cache area. “The content is used by the user” means that the content is reproduced and output in accordance with a reproduction instruction from the user. The date information may include year and month and time.

  The storage unit 12 of the node Nn participating in the overlay network ON stores content catalog information, a routing table using DHT, and the like.

  Here, the content catalog information includes a record of each content that can be used in the content distribution system S. In the content record, a content ID, a content name, a file size of the content, a keyword, and the like are described. The content file size is information indicating the data amount of the content. In the case of composite content, the content catalog information includes a record of composite content. The content record is generated when the content is input into the content distribution system S. The content catalog information including the generated record is distributed from the content management server MS to each node Nn. Note that information described in the composite content metafile may be described in the composite content record. In this case, there is no need to input the meta file of the composite content into the content distribution system S.

  The buffer memory 13 buffers content received via the communication unit 13. The decoder unit 14 performs decoding processing such as data expansion and decoding of video data and audio data included in the content. In the case of composite content, the resource file is the target of decoding processing. The video processing unit 15 performs a predetermined drawing process on the video data decoded by the decoder unit 14 and reproduces and outputs it as a video signal. The display unit 16 displays a video or the like on the display based on the video signal reproduced and output from the video processing unit 15. The display unit 16 displays the image decoded by the decoder unit 14. The audio processing unit 17 performs D (Digital) / A (Analog) conversion of the audio data decoded by the decoder unit 14 into an analog audio signal, and then amplifies this by an amplifier and outputs it. The speaker 18 outputs the sound signal output from the sound processing unit 17 as a sound wave.

  The communication unit 19 controls communication of information between the content management server MS and other nodes Nn through the network NW.

  The control unit 11 includes a CPU having a calculation function, a working RAM, a ROM, and the like. And the control part 11 performs the process mentioned later, when CPU reads and runs the P2P program memorize | stored in the memory | storage part 12 grade | etc.,. The control unit 11 has a clock function. The control unit 11 is an example of a deletion unit in the present invention.

[ 3. Operation of Content Distribution System S ]
Next, the operation of the content distribution system S according to the present embodiment will be described with reference to FIGS. FIG. 3 is a conceptual diagram showing a state from input to deletion of composite content. FIG. 4 is a flowchart showing processing in the control unit 11 of the node N1. In the following operation example, it is assumed that each file constituting the composite content input into the content distribution system S is already stored in the node N1, as shown in FIG. The storage capacity of the content cache area is set in advance.

  The process shown in FIG. 4 is started when, for example, a request for acquiring content designated by the user via the input unit 19a is made. When the process shown in FIG. 4 is started, the control unit 11 of the node N1 acquires the content ID of the designated content (step S1). For example, the content ID is acquired from a tag described in a Web page transmitted from the content providing site to the node N1. Alternatively, the content ID may be acquired by keyword search from content catalog information stored in the node Nn.

  Next, the control unit 11 sets the file size of the content corresponding to the content ID acquired in step S1 as a threshold (step S2). Here, the file size of the content corresponding to the content ID is acquired from content catalog information, for example. When the content corresponding to the content ID is composite content, the sum of the file sizes of the files constituting the composite content is set as a threshold value.

  Next, the control unit 11 determines whether or not an empty area equal to or larger than the threshold set in step S2 is in the content cache area in the storage unit 12 (step S3). If the control unit 11 determines that there is no free area equal to or greater than the threshold in the content cache area (step S3: NO), the process proceeds to step S4. On the other hand, if the control unit 11 determines that there is a free area equal to or larger than the threshold in the content cache area (step S3: YES), the control unit 11 proceeds to step S31.

  In step S4, the control unit 11 initializes the deletion candidate list. This deletion candidate list is a list in which file names of files that are deletion candidates are registered. By this initialization, the file name is not registered in the deletion candidate list.

  Next, the control unit 11 determines whether a moving image file is stored in the content cache area (step S5). Whether or not the file is a moving image file can be determined by, for example, the extension of the file. For example, when the extension is “AVI”, “FLV”, or “WMV”, it is determined that the file is a moving image file. A moving image file may be a part of composite content or a normal content. In addition, the normal content may be composed of a file including a moving image file. In these cases, it is determined that the file is a moving image file. When the control unit 11 determines that the moving image file is stored in the content cache area (step S5: YES), the control unit 11 proceeds to step S6. On the other hand, when determining that the moving image file is not stored in the content cache area (step S5: NO), the control unit 11 proceeds to step S11.

  In step S6, the control unit 11 registers the file name of the moving image file stored in the content cache area in the deletion candidate list. In this way, by registering the file name of the moving image file in the deletion candidate list, it is possible to delete the moving image file preferentially over the resource file, metafile, and control file other than the moving image file.

  Here, for example, the file names of all moving image files stored in the content cache area are registered in the deletion candidate list.

  Alternatively, the deletion candidate list may be configured to register the file names of the moving image files acquired before the time point that is a predetermined period after the current time point. Whether or not the movie file is acquired before the time point that is a predetermined period after the current time is determined by the acquisition date information added to the movie file. The “predetermined period” can be arbitrarily set by the user of the node N1, for example, via the input unit 19a. By setting such a predetermined period, an old moving image file can be preferentially deleted.

  Alternatively, the deletion candidate list may be configured so that the file name of the moving image file used by the user before the time point that is traced back for a predetermined period from the present time is registered. Whether or not it is a moving image file used by the user before a time point that is a predetermined period later than the present time is determined based on usage date information added to the moving image file. The “predetermined period” can be arbitrarily set by the user of the node N1, for example, via the input unit 19a. By setting such a predetermined period, it is possible to efficiently and preferentially delete a moving image file that has not been used for a predetermined period.

  Next, the control unit 11 selects one or more operation files that have not been selected from the moving image files whose file names are registered in the deletion candidate list (step S7). In the deletion candidate list, a selected flag indicating the selected state is registered in association with the file name of the selected moving image file.

  Here, when a plurality of file names of moving image files are registered, for example, an operation file having the largest file size is selected. As a result, it is possible to preferentially delete an operation file having a large file size. Therefore, the content cache area can be used effectively.

  Alternatively, when a plurality of file names of moving image files are registered, for example, a moving image file having the oldest acquired date and time may be selected. Thereby, the acquired date and time can be preferentially deleted from the moving image file with the oldest date. Whether or not the acquired date and time is the oldest moving image file is determined by the acquisition date information added to the moving image file.

  Alternatively, when a plurality of moving image file names are registered, for example, a moving image file having the oldest date and time used by the user may be selected. Thereby, it is possible to preferentially delete the used date and time from the moving image file. Whether or not the date and time of use is the oldest moving image file is determined based on the usage date information added to the moving image file.

  Next, the control unit 11 calculates the total file size of the selected moving image files (step S8). Here, the “total file size of moving image files” is the total file size of the moving image files selected in step S7 during the loop of steps S7 to S10.

  Next, the control unit 11 determines whether or not the sum of the file sizes calculated in step S8 is larger than the threshold set in step S2 (step S9). If the control unit 11 determines that the total file size is not larger than the threshold (step S9: NO), the control unit 11 proceeds to step S10. On the other hand, if the control unit 11 determines that the sum of the file sizes is larger than the threshold (step S9: YES), the control unit 11 proceeds to step S30. When the sum of the file sizes is larger than the threshold value, it is possible to secure a free area in the content cache area for storing the content corresponding to the content ID acquired in step S1.

  In step S10, the control unit 11 determines whether there is a moving image file that has not been selected in the deletion candidate list. In this determination, the selected flag is referred to. If the control unit 11 determines that there is a video file that has not yet been selected (step S10: YES), the control unit 11 returns to step S7. On the other hand, when the control unit 11 determines that there is no moving image file not yet selected (step S10: NO), the control unit 11 proceeds to step S11.

  In step S11, the control unit 11 determines whether a resource file other than the moving image file is stored in the content cache area. The resource file other than the moving image file is at least one of an image file, an audio file, and a text file. Whether it is a resource file other than a moving image file can be determined by, for example, the extension of the file. If the control unit 11 determines that a resource file other than the moving image file is stored in the content cache area (step S11: YES), the control unit 11 proceeds to step S12. On the other hand, if the control unit 11 determines that no resource file other than the moving image file is stored in the content cache area (step S11: NO), the process proceeds to step S17.

  In step S12, the control unit 11 registers the file names of resource files other than the moving image file stored in the content cache area in the deletion candidate list. In this way, by registering the file names of resource files other than moving image files in the deletion candidate list, resource files other than moving image files can be deleted preferentially over metafiles and control files.

  Here, in the deletion candidate list, for example, file names of all resource files other than the moving image file among the resource files stored in the content cache area are registered.

  Alternatively, as in step S6, the deletion candidate list may be configured to register the file names of all resource files other than the moving image file that were acquired before the time point that is a predetermined period after the current time point. Thereby, the resource file which became old can be deleted preferentially. Alternatively, as in step S6 above, the deletion candidate list may be configured to register the file names of all resource files other than the video file that were used by the user before a time point that is a predetermined period after the current time. good. As a result, resource files that have not been used for a predetermined period can be efficiently deleted with priority.

  Next, the control unit 11 selects one or more resource files that have not been selected from resource files whose file names are registered in the deletion candidate list (step S13). In the deletion candidate list, a selected flag indicating registered is registered in association with the file name of the selected resource file.

  Here, when a plurality of file names of resource files other than the moving image file are registered, the resource file having the largest file size is selected as in step S7. Or you may comprise so that the resource file with the oldest acquired date may be selected similarly to said step S7. Or you may comprise so that the resource file with the oldest date and time utilized by the user may be selected similarly to said step S7.

  Next, the control unit 11 calculates the sum of the file sizes of the selected file (step S14). Here, the “total file size of files” is selected in step S13 during the loop of steps S13 to S16 and the file size of the moving image file selected in step S7 during the loop of steps S7 to S10. This is the total file size of all resource files.

  Next, the control unit 11 determines whether or not the sum of the file sizes calculated in step S14 is larger than the threshold set in step S2 (step S15). If the control unit 11 determines that the sum of the file sizes is not larger than the threshold (step S15: NO), the control unit 11 proceeds to step S16. On the other hand, if the control unit 11 determines that the total file size is larger than the threshold (step S15: YES), the control unit 11 proceeds to step S30.

  In step S16, the control unit 11 determines whether there is a resource file that has not yet been selected in the deletion candidate list. If the control unit 11 determines that there is a resource file that has not yet been selected (step S16: YES), the control unit 11 returns to step S13. On the other hand, if the control unit 11 determines that there is no resource file that has not been selected yet (step S16: NO), the control unit 11 proceeds to step S17.

  In step S17, the control unit 11 determines whether a metafile is stored in the content cache area. Whether it is a metafile or not can be determined by, for example, the extension of the file. If the control unit 11 determines that the metafile is stored in the content cache area (step S17: YES), the control unit 11 proceeds to step S18. On the other hand, when determining that the metafile is not stored in the content cache area (step S17: NO), the control unit 11 proceeds to step S23.

  In step S18, the control unit 11 registers the file name of the metafile stored in the content cache area in the deletion candidate list. Thus, by registering the metafile in the deletion candidate list, the metafile can be left in the content cache area even after the resource file is deleted.

  Here, in the deletion candidate list, for example, file names of all metafiles stored in the content cache area are registered.

  Alternatively, as in step S6, the deletion candidate list may be configured to register the file names of the metafiles acquired before the time point that is a predetermined period back from the current time. This makes it possible to preferentially delete the metafile that has become old. Alternatively, as in step S6, the deletion candidate list may be configured to register the file name of the metafile used by the user before the time point that is a predetermined period back from the current time. As a result, metafiles that are not used for a predetermined period can be efficiently deleted with priority.

  Next, the control unit 11 selects one or more metafiles that have not been selected from metafiles whose file names are registered in the deletion candidate list (step S19). In the deletion candidate list, a selected flag indicating the selected state is registered in association with the file name of the selected metafile.

  If a plurality of metafile file names are registered, the metafile having the largest file size is selected as in step S7. Or you may comprise so that the metafile with the oldest acquired date may be selected similarly to said step S7. Or you may comprise so that the metafile with the oldest date and time utilized by the user may be selected similarly to said step S7.

  Next, the control unit 11 calculates the sum of the file sizes of the selected files (step S20). Here, the “total file size of files” is selected in step S13 during the loop of steps S13 to S16 and the file size of the moving image file selected in step S7 during the loop of steps S7 to S10. The sum of the file size of the resource file and the file size of the metafile selected in step S19 during the loop of steps S19 to S22.

  Next, the control unit 11 determines whether or not the sum of the file sizes calculated in step S20 is larger than the threshold set in step S2 (step S21). If the control unit 11 determines that the sum of the file sizes is not larger than the threshold (step S21: NO), the control unit 11 proceeds to step S22. On the other hand, if the control unit 11 determines that the total file size is larger than the threshold (step S21: YES), the control unit 11 proceeds to step S30.

  In step S22, the control unit 11 determines whether there is a metafile that has not yet been selected in the deletion candidate list. If the control unit 11 determines that there is a metafile that has not yet been selected (step S22: YES), the control unit 11 returns to step S19. On the other hand, if the control unit 11 determines that there is no metafile not yet selected (step S22: NO), the control unit 11 proceeds to step S23.

  In step S23, the control unit 11 determines whether or not a control file is stored in the content cache area. Whether or not the file is a control file can be determined by, for example, the extension of the file. When the control unit 11 determines that the control file is stored in the content cache area (step S23: YES), the control unit 11 proceeds to step S24. On the other hand, if the control unit 11 determines that the control file is not stored in the content cache area (step S23: NO), the control unit 11 proceeds to step S29.

  In step S24, the control unit 11 registers the file name of the control file stored in the content cache area in the deletion candidate list. Thus, by registering the control file in the deletion candidate list lastly, the control file can be left in the content cache area to the end.

  Here, for example, the file names of all control files stored in the content cache area are registered in the deletion candidate list.

  Alternatively, as in step S6, the deletion candidate list may be configured to register the file name of the control file acquired before the time point that is a predetermined period back from the current time point. Thereby, the control file which became old can be deleted preferentially. Alternatively, as in step S6, the deletion candidate list may be configured such that the file name of the control file used by the user before the time point that is a predetermined period back from the current time is registered. As a result, it is possible to efficiently and preferentially delete control files that are not used for a predetermined period.

  Next, the control unit 11 selects one or more control files that have not been selected from the control files whose file names are registered in the deletion candidate list (step S25). In the deletion candidate list, a selected flag indicating registered is registered in association with the file name of the selected control file.

  Here, when a plurality of control file names are registered, the control file having the largest file size is selected as in step S7. Or you may comprise so that the control file with the oldest acquired date may be selected similarly to said step S7. Or you may comprise so that the control file with the oldest date used by the user may be selected similarly to said step S7.

  Next, the control unit 11 calculates the sum of the file sizes of the selected files (step S26). Here, the “total file size of files” is selected in step S13 during the loop of steps S13 to S16 and the file size of the moving image file selected in step S7 during the loop of steps S7 to S10. The file size of the resource file, the file size of the metafile selected in step S19 during the loop of steps S19 to S22, and the file size of the control file selected in step S25 during the loop of steps S25 to S28. And the sum of

  Next, the control unit 11 determines whether or not the sum of the file sizes calculated in step S26 is larger than the threshold set in step S2 (step S27). If the control unit 11 determines that the sum of the file sizes is not greater than the threshold (step S27: NO), the control unit 11 proceeds to step S28. On the other hand, if the control unit 11 determines that the total file size is larger than the threshold (step S27: YES), the control unit 11 proceeds to step S30.

  In step S28, the control unit 11 determines whether there is a control file that has not yet been selected in the deletion candidate list. If the control unit 11 determines that there is a control file that has not yet been selected (step S28: YES), the control unit 11 returns to step S25. On the other hand, when the control unit 11 determines that there is no control file not yet selected (step S28: NO), the control unit 11 proceeds to step S29.

  In step S29, the control unit 11 executes error processing. In this error processing, for example, a message indicating that a free area for storing content cannot be secured in the content cache area is displayed on the display unit 16.

  Note that, as described above, there are cases where only the file names of files acquired before the time point that is traced back for a predetermined period from the current time are registered in the deletion candidate list. Alternatively, only the file name of a file used by the user before a time point that has been traced a predetermined period from the current time may be registered in the deletion candidate list. In these cases, in the error processing shown in step S29, a message that prompts the user to shorten the predetermined period may be displayed on the display unit 16. The user who has confirmed this message changes the setting to shorten the “predetermined period” via the input unit 19a. When the setting is changed, the control unit 11 returns to step S5 and repeats the process. For example, when the predetermined period is changed from 30 days to 10 days, the number of files registered in the deletion candidate list increases. Therefore, it is possible to secure a free area for storing content in the content cache area.

  Next, in step S30, the control unit 11 executes content deletion processing. This content deletion processing is processing for deleting content from the content cache area. Specifically, the control unit 11 deletes the file corresponding to the file name associated with the selected flag from the content cache area among the file names registered in the deletion candidate list. As a result, a free area for storing content is secured in the content cache area.

  Here, when the content deletion process in step S30 is executed by the transition from step S9, as shown in FIG. 3B, among the files constituting the composite content, the moving image file is changed to another file. Deleted with priority.

  On the other hand, when the content deletion process in step S30 is executed by the transition from step S15, the resource file is deleted in preference to the metafile and the control file. In this case, when there is no moving image file to be deleted, for example, an image file is deleted as shown in FIG.

  On the other hand, when the content deletion process in step S30 is executed by the transition from step S21, the resource file and the metafile are deleted in preference to the control file. In this case, when there is no resource file to be deleted, for example, a metafile is deleted as shown in FIG. Thus, the control file remains in the content cache area until the end.

  In the above processing, the metafile is preferentially deleted over the control file, but the control file may be preferentially deleted over the metafile. In this case, in step S18, the file name of the control file is registered in the deletion candidate list instead of the metafile stored in the content cache area. Then, the processing from step S19 to step S22 is performed on the control file. On the other hand, in this case, in step S24, the file name of the metafile is registered in the deletion candidate list instead of the control file stored in the content cache area. Then, the processing from step S25 to step S28 is performed on the metafile.

  Next, in step S31, the control unit 11 executes content acquisition processing. This content acquisition process is a process of searching and acquiring content via the overlay network ON based on the content ID. Specifically, the control unit 11 first generates a content location inquiry message. The content location inquiry message is a message for inquiring the location of the content to the root node. The content location inquiry message includes the IP address and port number of the node N1 and the content ID of the content. The control unit 11 transmits the generated content location inquiry message to the content root node by DHT routing. The DHT routing is known in, for example, Japanese Patent Application Laid-Open No. 2007-053662, and detailed description thereof is omitted.

  The root node that has received the content location inquiry message acquires index information corresponding to the content ID included in the content location inquiry message. The root node returns the acquired index information to the node N1 that is the transmission source of the content location inquiry message. The index information returned in this way includes the IP address of the content holding node storing the content. Thus, the control unit 11 of the node N1 receives the index information from the root node. Then, the control unit 11 accesses the content holding node, for example, based on the IP address of the content holding node included in the received index information. Then, the control unit 11 downloads content from the content holding node. Here, the downloaded content may be a composite content metafile. In this case, the control unit 11 executes content search and acquisition processing in the same manner as described above based on each content ID described in the metafile. By this content search and acquisition process, the control unit 11 of the node N1 downloads a resource file and a control file constituting the composite content from, for example, a content holding node.

  Next, the control unit 11 stores and saves the content downloaded and accumulated in the buffer memory 13 in the content cache area (step S32). In the case of composite content, the downloaded resource file, control file, and metafile are stored and saved in the content cache area as content. When the content is stored in this way, the control unit 11 transmits a publish message to the root node according to the routing table using DHT. This publish message is a message for disclosing to other nodes Nn that the content is stored. Since the publish message is known in Japanese Patent Application Laid-Open No. 2007-053452 and the like, detailed description thereof is omitted.

  In addition, you may comprise so that the process of said step S3-S30 may be periodically performed in the preset time interval irrespective of acquisition of a content. In this case, the process of step S3 is started when a preset time arrives. The “threshold value” in step S3 is set in advance to, for example, about 10% of the maximum storage capacity of the content cache area.

  As described above, according to the above-described embodiment, when deleting the content stored in the content cache area, the node Nn preferentially deletes the video file among the files constituting the composite content. Configured. Therefore, the metafile and the control file that are first required when reproducing the composite content can be left in the content cache area even after the resource file is deleted. Accordingly, it is possible to avoid wasting time until the resource file constituting the composite content is reproduced, and the resource file can be reproduced and output quickly.

  Moreover, in the said embodiment, it comprised so that it might delete preferentially from a resource file with a large file size among several resource files. Therefore, more content can be stored in the content cache area, and the content cache area can be used effectively. In the above embodiment, the operation file having a larger data amount than the image file and the text file is preferentially deleted. Therefore, more content can be stored in the content cache area, and the content cache area can be used effectively. Note that when an operation file and an image file or text file are stored in the node Nn, the node Nn may be configured to delete the image file or text file with priority over the operation file. By deleting content such as an image file or a text file having a data amount smaller than that of the operation file first, content having a small data size does not take download time and can be obtained immediately.

  Further, in the above embodiment, the content may be deleted from the content cache area periodically based on the usage status of each content in the content cache area at a preset time interval. Specifically, when the preset time arrives, the control unit 11 refers to the use date information added to each content stored in the content cache area and is used for a predetermined period. It is determined whether there is content that has not been received. Then, when it is determined that there is content that has not been used for a predetermined period, the control unit 11 deletes the content that has not been used for a predetermined period from the content cache area. According to this configuration, it is possible to efficiently delete contents with low usage frequency. Therefore, the content cache area can be used effectively.

  In the above embodiment, the peer-to-peer network using DHT is applied to the overlay network ON. However, the present invention is not limited to this. For example, a system using another overlay network may be applied. As a peer-to-peer system that does not use DHT, for example, there is a hybrid peer-to-peer system.

DESCRIPTION OF SYMBOLS 11 Control part 12 Storage part 13 Buffer memory 19 Communication part MS Content management server Nn node NW network ON Overlay network S Content delivery system

Claims (8)

A plurality of node devices that can communicate with each other via a network, one or more contents are stored in one or more node devices, and each node device is based on unique identification information assigned to each content. The node device in the distribution system configured to acquire the content stored in the node device,
Storage means for storing at least one of first content output in time series and second content necessary for output control of the first content among the composite content composed of a plurality of contents When,
A deletion unit that preferentially deletes the first content out of the contents constituting the composite content when the content stored in the storage unit is deleted;
A node device comprising: The storage means stores at least one of a plurality of the first content and the second content constituting the composite content,
The node device according to claim 1, wherein the deleting unit preferentially deletes the first content having a large amount of data among the plurality of first contents. The storage means stores at least a content composed of a moving image and a content composed of a still image or text as the first content,
3. The node device according to claim 1, wherein the deleting unit preferentially deletes the content made up of the moving image over the content made up of a still image or text. 4. The storage means includes identification information assigned to each of the first content, the second content, and the content constituting the composite content that constitutes the composite content, and is distributed to a plurality of node devices. At least a third content in which identification information for searching a plurality of stored content is described is stored;
The node device according to any one of claims 1 to 3, wherein the deletion unit preferentially deletes the first content from among the content constituting the composite content.   5. The node device according to claim 1, wherein the deletion unit deletes the second content that has not been used for a predetermined time.   The second content includes at least one of a file for controlling the output timing of the first content and a file for performing display control for displaying the first content on a predetermined display. The node device according to claim 1, wherein the node device is characterized in that: A plurality of node devices that can communicate with each other via a network, one or more contents are stored in one or more node devices, and each node device is based on unique identification information assigned to each content. A computer included in the node device in a distribution system configured to acquire the content stored in the node device;
A step of storing at least one of a first content output in a time series in a composite content composed of a plurality of contents and a second content necessary for output control of the first content; ,
A step of preferentially deleting the first content out of the content constituting the composite content when deleting the stored content;
Node processing program to execute. A plurality of node devices that can communicate with each other via a network, one or more contents are stored in one or more node devices, and each node device is based on unique identification information assigned to each content. A content deletion method in a distribution system configured to acquire the content stored in the node device of
The node device selects any one of the first content output in time series and the second content necessary for output control of the first content from among the composite content composed of a plurality of contents. At least a memorizing step;
When the node device deletes the stored content, the step of deleting the first content preferentially from the content constituting the composite content;
A content deletion method comprising:

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