JPWO2012011473A1 - TRANSMISSION DEVICE, TRANSMISSION METHOD, RECEPTION DEVICE, RECEPTION METHOD, COMMUNICATION SYSTEM, DATA STRUCTURE, PROGRAM, AND STORAGE MEDIUM - Google Patents

Abstract

When the video server (2) is requested to transmit content data from the video playback device (1), the video server (2) acquires each of a plurality of partial data constituting the content data from one or a plurality of storages (3). The receiving unit (21) completes the acquisition by associating each of the partial data acquired by the receiving unit (21) with the reproduction order designation information for specifying the reproduction order of the partial data. A transmission unit (26) for sequentially transmitting to the video reproduction device (1).

Description

  The present invention relates to a transmission apparatus and a transmission method for transmitting content data. The present invention also relates to a receiving device that receives content data transmitted from such a transmitting device, and a communication system that includes such a transmitting device and a receiving device.

  In recent years, with the rapid increase in demand for the Internet, not only users who view web pages composed of text and still images, but also users who want to view video content, audio content, etc. through streaming distribution are increasing. It is coming.

  In general, a user can obtain text data, still image data, and the like of a WEB page by accessing the WEB page with a browser. However, in this case, the text data and still image data can be obtained using the http (s) protocol. To be transmitted.

  On the other hand, video content, audio content, and the like are often distributed using an RTP protocol that is a protocol designed with emphasis on real-time characteristics.

  By the way, as a user's use of the Internet, there are overwhelmingly many uses of accessing a WEB page with a browser. For this reason, in general, a port used for communication of the http (s) protocol is opened in the firewall. On the other hand, communication such as the RTP protocol may be blocked by a firewall.

  For this reason, in order to meet the user's desire to view content such as video and audio anytime and anywhere, a technology for performing content communication using the http (s) protocol has been developed.

  In particular, there is a need for live streaming distribution in which events are simultaneously distributed to unspecified or specified numbers in real time by http communication. As a typical distribution method of such live streaming distribution, a distribution method by sequentially downloading an MPEG (Moving Picture Expert Group) MP4 file format (Patent Document 1), and a fragment video format of MPEG ISO Media File Format. And a distribution method using a plurality of TCP connections for divided image data obtained by further dividing moving image data divided into frame units (Patent Document 2).

Japanese Patent Publication “Japanese Patent Laid-Open No. 2005-110244 (published on April 21, 2005)” Japanese Patent Publication “JP 2007-173987 A (published July 5, 2007)” Japanese Patent Publication “Japanese Patent Laid-Open No. 2004-260668 (Released on September 16, 2004)”

  In video distribution using http (s), content data to be distributed is often divided and stored in a plurality of storages. In this case, video distribution from the video server to the video playback device is performed, for example, as shown in FIG.

  That is, when the video reproduction device 1 requests the video server 2 to transmit content data (step 30; hereinafter simply referred to as S30), the video server 2 determines that each of a plurality of partial data constituting the content data is included. The acquisition of the plurality of partial data is started from the plurality of stored storages 3a to 3b (S31, S32). Here, the content data is composed of two partial data, the first partial data (hereinafter referred to as partial data a) is stored in the storage 3a, and the second partial data (hereinafter referred to as “partial data a”). The case where the partial data b) is stored in the storage 3b will be described as an example.

  Here, when the acquisition of the partial data a from the storage 3a is completed without delay (S33), and the acquisition of the partial data b from the storage 3b is completed without delay (S34), the video server 2 stores the acquired plurality of partial data. Rearrangement is performed in the order of reproduction (S35), and the plurality of rearranged partial data content data are transmitted to the video reproduction apparatus 1 (S36).

  When the acquisition of the partial data a from the storage 3a is completed with a delay of 1 (S37), the video server 2 acquires the partial data a at the timing when the acquisition of all the partial data is completed, that is, in S37. Is completed, the obtained plurality of partial data is rearranged in the order of reproduction (S38), and the rearranged partial data is transmitted to the video reproduction apparatus 1 (S39). In this case, the video reproduction device 1 reproduces the video with a delay of delay 2 compared to the case where no delay has occurred (S40).

  However, such video distribution has two problems. First, after the video server 2 acquires all of the plurality of partial data, the video server 2 has a memory for storing all the partial data in order to perform a process of rearranging the plurality of partial data in the order of reproduction. Necessary.

  Second, since the video server 2 rearranges after acquiring all the partial data, there is a problem that the reproduction of the content data in the video reproduction apparatus 1 is delayed due to the delay in the acquisition of the partial data.

  Further, the transmission device described in Patent Document 3 described above is divided image data obtained by further dividing individual unit image data by using one frame or a plurality of frames of moving image data divided into frames for throughput improvement. The image data is transmitted to the receiving device through a plurality of TCP connections, and the receiving device performs processing for returning the divided image data received from the plurality of TCP connections to the original data. Here, the number of divisions of unit image data and the number of TCP connections are determined based on the throughput per TCP connection and the average bit rate of moving image data.

  However, in the above technique, when the amount of moving image data is large, the number of TCP connections becomes large, but the number of TCP connections of the transmission device is limited. In addition, since the moving image data stored in the data storage unit of the receiving device is stored in the order of frames, there is a possibility that reproduction of moving image data may be delayed if reception of a certain frame is delayed.

  The present invention has been made in view of the above-described problems, and its main object is a transmission apparatus that transmits content data so that the reproduction apparatus that has received the content data can reproduce the content without delay. To implement the device.

  In order to solve the above-described problem, when a transmission device according to the present invention is requested to transmit content data from another device, each of a plurality of partial data constituting the content data is transferred to one or a plurality of partial data. A partial data acquisition unit that acquires from a storage device; and the partial data acquisition unit that associates each of the plurality of partial data acquired by the partial data acquisition unit with reproduction order designation information that designates the reproduction order of the partial data. Comprises partial data transmission means for transmitting to the other devices in the order of completion of acquisition.

  The transmission method according to the present invention is a transmission method in which a transmission device transmits content data, and when a transmission of content data is requested from another device, a plurality of partial data constituting the content data is transmitted. A partial data acquisition step for acquiring each from one or a plurality of storage devices, and each of the plurality of partial data acquired in the partial data acquisition step, reproduction order designation information for designating the reproduction order of the partial data; And a partial data transmission step of transmitting to the other devices in the order in which acquisition is completed in the partial data acquisition step.

  According to the above configuration, the partial data constituting the content data requested by the other device is transmitted to the other device in the order obtained from the storage device, so that the partial data with the slow reproduction order is transmitted. Even in the case of the acquisition first, the partial data can be transmitted to another device without delay.

  As a result, the other apparatus can receive the partial data without delay, so that the waiting time due to not receiving the partial data at the start of reproduction can be reduced.

  In order to solve the above-described problem, a receiving apparatus according to the present invention includes a partial data receiving unit that receives a plurality of partial data constituting content data together with reproduction order designation information associated with each of the plurality of partial data. And a partial data rearranging means for rearranging the plurality of partial data received by the partial data receiving means in a reproduction order designated by the reproduction order designation information received by the partial data receiving means. It is characterized by.

  The receiving method according to the present invention is a receiving method in which a receiving apparatus receives content data, and a plurality of pieces of partial data constituting the content data are reproduced in order of designation information associated with each of the plurality of pieces of partial data. A partial data receiving step received together with the partial data received in the partial data receiving step, and the partial data rearranged in the reproduction order designated by the reproduction order designation information received in the partial data receiving step A sorting step.

  According to said structure, the content data transmitted from the transmitter mentioned above can be received without delay.

  Other objects, features, and advantages of the present invention will be fully understood from the following description. The advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

  The present invention has an effect of realizing a transmitting apparatus that transmits content data, and realizes a transmitting apparatus that allows the reproducing apparatus that has received the content data to reproduce the content without delay.

It is a figure which shows the structural example of the communication system which concerns on this invention. It is a block diagram which shows the principal part structure of the video reproduction apparatus in the communication system of FIG. It is a block diagram which shows the principal part structure of the video server in the communication system of FIG. FIG. 2 is a block diagram showing a main configuration of storage in the communication system of FIG. 1. It is a figure which shows the structure of content data. 3 is a flowchart showing a flow of processing of a video playback device in content playback processing according to the first embodiment. 3 is a flowchart showing a flow of processing of a video server in content reproduction processing according to the first embodiment. It is a figure which shows an example of the HTTP message transmitted from a video reproduction apparatus, (a) is a figure which shows a request message, (b) is a figure which shows the request message containing a buffer size. It is a figure which shows an example of the HTTP message transmitted from a video server. 6 is a sequence diagram illustrating an example of a flow of content reproduction processing according to Embodiment 1. FIG. 6 is a diagram illustrating an example of a data flow in content reproduction processing according to Embodiment 1. FIG. FIG. 10 is a sequence diagram illustrating another example of the flow of content reproduction processing according to the first embodiment. It is a figure which shows the other example of the HTTP message transmitted from a video server. It is a figure which shows the other example of the flow of data in the content reproduction | regeneration processing of a communication system. FIG. 10 is a diagram illustrating a configuration of content data in content reproduction processing according to the second embodiment. 10 is a flowchart showing a flow of processing of a video server in content reproduction processing according to the second embodiment. 10 is a diagram illustrating an example of a data flow in content reproduction processing according to Embodiment 2. FIG. FIG. 10 is a diagram illustrating another example of the data flow in the content reproduction process according to the second embodiment. It is a figure which shows the example of the HTTP message transmitted from the video server of FIG. FIG. 10 is a diagram illustrating a configuration of content data in content reproduction processing according to the third embodiment. 10 is a flowchart showing a flow of processing of a video playback device in content playback processing according to Embodiment 3. 10 is a flowchart showing a flow of processing of a video server in content reproduction processing according to the third embodiment. It is a figure which shows the other example of the HTTP message transmitted from a video server. It is a sequence diagram which shows an example of the flow of the conventional content reproduction | regeneration processing.

  An embodiment of the present invention will be described below with reference to the drawings. In the following description, a video is exemplified as content to be reproduced, a video server is exemplified as a transmission device, and a video reproduction device is exemplified as a reproduction device (another device), but the present invention is limited to this. It is not a thing. In particular, video is merely an example of content, and the content includes all kinds of information such as moving images, still images, characters, and audio. The playback device may be any device that can play back the content transmitted from the transmission device.

[Content data structure]
First, the configuration of content data to be distributed in the present embodiment will be described with reference to FIG. FIG. 5 is a diagram illustrating a configuration of content data to be distributed in the present embodiment. FIG. 5 shows content data C including encoded data obtained by encoding video content as an example of content data to be distributed.

  The content (video) is composed of a plurality of frames, and is encoded for each frame. At the time of encoding, since the redundancy of the content is reduced by predictive encoding or the like, the data size of the encoded data is smaller than the data size of the content. In this embodiment, this encoded data is divided into one or a plurality of reproduction units (segments) U1, U2,... UM, and each reproduction unit Ui is further divided into one or a plurality of partial data (fragments) Fi1. , Fi2,..., FiN. For example, encoded data that requires one hour for reproduction is equally divided into 60 reproduction units U1, U2,..., U60, and each reproduction unit Ui that requires one minute for reproduction is further divided into 60 partial data Fi1. , Fi2,..., Fi60 can be equally divided and managed. In this case, the time required to reproduce each partial data Fij is 1 second. However, the division method for dividing the encoded data into reproduction units U1, U2,... UM and the division method for dividing each reproduction unit Ui into partial data Fi1, Fi2,. Is not to be done.

  In the content data C distributed from the video server to the video playback device, as shown in FIG. 5, a header H corresponding to the entire encoded data is arranged at the head of the content data C and corresponds to each partial data Fij. A header Hij is arranged at the beginning of the partial data, and a delimiter S indicating the end of each reproduction unit is arranged at the end of the reproduction unit. When the entire encoded data is managed as one reproduction unit, the content data includes a single delimiter S indicating the end of the entire encoded data. In this specification, the header H corresponding to the entire encoded data is referred to as an “overall header”, and the header Hij corresponding to each partial data is referred to as a “partial header” to distinguish them.

  Each divided data Fij is preferably reproducible without referring to other divided data Fi′j ′. For example, regarding the encoded data encoded according to H264 / AVC, it is desirable to divide the encoded data into partial data so that the encoded data constituting the same GOP (Group of Picture) is not divided.

[Outline of communication system]
An outline of a communication system according to the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration example of a communication system (content transmission system) 100.

  As shown in FIG. 1, the communication system 100 is a system for distributing content data, and includes a video playback device (another device, a receiving device) 1, a video server 2, and a plurality of storages 3. ing. Content data to be distributed is divided into a plurality of partial data, and is distributed and stored in a plurality of storages 3. The video playback device 1 is connected to a video server (transmission device) 2 via a network 1 (hereinafter “NW1”), and the video server 2 is connected to one or a plurality of storages (hereinafter “NW2”) via a network 2 (hereinafter “NW2”). Storage device) 3. NW1 and NW2 may be any devices that can communicate with each other, and may be a wired communication network or a wireless communication network.

  In the communication system 100, the video reproduction device 1 requests the video server 2 to transmit content data via the NW1. However, the request for content data is made for each reproduction unit (specific part) described above. Receiving this request, the video server 2 acquires each piece of partial data constituting the requested reproduction unit from the plurality of storages 3 via the NW 2 and transmits the partial data to the video reproduction device 1 in the order in which the acquisition is completed. The video reproduction device 1 receives these partial data, rearranges them, and decodes / reproduces them.

  In the present embodiment, a storage server connected to the video server 2 via the NW 2 is assumed as a storage device for storing partial data, but the present invention is not limited to this. For example, a configuration in which partial data is stored in a recording device such as an HDD (Hard Disk Drive Device) built in the video server 2 may be adopted. However, in the configuration in which the network (NW2) is interposed between the storage device (storage 3) for storing the partial data and the video server 2, and the delay of reading of the partial data from the storage device is likely to occur, the effect of the present invention. It goes without saying that it appears prominently.

  Hereinafter, the configurations of the video playback device 1, the video server 2, and the storage 3 constituting the communication system 100 of FIG. 1 will be described with reference to FIGS.

[Configuration of Video Playback Device 1]
The principal part structure of the video reproduction apparatus 1 is demonstrated using FIG. FIG. 2 is a block diagram showing a main configuration of the video playback apparatus 1.

  The video reproduction apparatus 1 includes a request generation unit 11, a transmission unit 12, a control unit 13, a decoding unit 14, a buffer 15, a rearrangement processing unit (partial data rearrangement unit) 16, a reception unit (partial data reception unit) 17, and a monitoring A unit 18 and a playback unit 19 are provided.

  The video playback device 1 further includes an input unit (not shown) that receives a user operation for designating content data to be played back. When the input unit accepts this user operation, the control unit 13 gives an instruction to the request generation unit 11 to generate a request message for requesting transmission of content data designated by the user operation.

  The request generation unit 11 generates a request message for requesting transmission of content data, for example, a GET message according to the HTTP protocol, in accordance with an instruction from the control unit 13. The request generator 11 supplies the generated request message to the transmitter 12.

  This request message requests transmission of content data for one reproduction unit, and includes reproduction unit designation information for designating a reproduction unit for which transmission is requested. When a URI (Uniform Resource Identifier) is given for each reproduction unit, the URI can be used as reproduction unit designation information. Also, when a URI is given for each content data, a combination of the URI and an identifier for identifying the requested reproduction unit from other reproduction units can be used as reproduction unit designation information. it can.

  The transmission unit 12 transmits the request message generated by the request generation unit 11 to the video server 2. The transmission unit 12 also functions as a means for transmitting a session disconnection notification, which will be described later, to the video server 2 in accordance with an instruction from the control unit 13.

  The receiving unit 17 receives content data transmitted from the video server 2 as a response to the request message. The content data received by the receiving unit 17 as a response to one request message is content data for one reproduction unit. As shown in FIG. 5, one whole header, a plurality of partial data, a plurality of partial headers, and One delimiter is included. The receiving unit 17 stores the received content data in the buffer 15 and supplies it to the monitoring unit 18.

  The monitoring unit 18 identifies the occurrence timing of various events by monitoring the content data received by the receiving unit 17. Examples of the timing specified by the monitoring unit 18 include timing at which reception of content data is started, timing at which each partial data is received, and timing at which reception of each reproduction unit is completed. These timings are specified by detecting the entire header, the partial header, and the delimiter in the content data received by the receiving unit 17. When content data is transmitted / received according to the HTTP protocol, the timing at which reception of content data is started can be specified by detecting a status line starting from “HTTP / 1.1” transmitted prior to the header. Good. The monitoring unit 18 notifies the control unit 13 of these timings.

  The monitoring unit 18 also functions as a means for determining whether or not the receiving unit 17 is in a delayed state every time it receives partial data and notifying the control unit 13 of the timing of transition to the delayed state. The determination of whether or not there is a delay state is made by comparing the time t at which each partial data is received with the decoding time (time at which decoding should be started) t ′ of the partial data (t ′ <t If it is, it is determined that the state is delayed). When the decode time t ′ is described in the partial header, the monitoring unit 18 determines whether or not the delay time is in reference to the decode time t ′ described in the partial header. If the presentation time (the time at which the first frame decoded from the partial data is to be displayed) t ″ is described in the partial header instead of the decoding time t ′, the monitoring unit 18 starts from the presentation time t ″. The decoding time t ′ = t ″ −Δt is calculated by subtracting the fixed amount Δt.

  The rearrangement processing unit 16 refers to the partial data for one reproduction unit stored in the buffer 15 according to the instruction of the control unit 13 with reference to the partial header (reproduction order designation information) corresponding to each of these partial data. By rearranging, encoded data that can be decoded in order from the top is generated. When the rearrangement of the partial data for one playback unit is completed, the rearrangement processing unit 16 stores the generated encoded data in the buffer 15 and notifies the control unit 13 that the rearrangement is completed.

  The decoding unit 14 decodes content from the encoded data generated by the rearrangement processing unit 16 in accordance with instructions from the control unit 13. The decryption unit 14 supplies the decrypted content to the playback unit 19. Further, the playback unit 19 displays the content supplied from the decryption unit 14 on a display or the like.

  The control unit 13 controls each unit of the video reproduction device 1. Specifically, the following control is performed. (1) When a user operation specifying content data to be reproduced is detected, the request generation unit 11 is instructed to generate a request message for requesting the first reproduction unit of the content data. (2) Upon receiving notification from the monitoring unit 18 that reception of each playback unit has been completed, (2a) rearrangement of the partial data stored in the buffer 15 (partial data constituting the playback unit for which reception has been completed). The rearrangement processing unit 16 is instructed, and (2b) the request generation unit 11 is instructed to generate a request message for requesting the next reproduction unit of the reproduction unit that has been received. (3) Upon receiving a notification from the rearrangement processing unit 16 that the rearrangement of the partial data stored in the buffer 15 has been completed, the decoding unit 14 is instructed to decode the encoded data generated by the rearrangement processing unit 16 To do. (4) Upon receiving notification from the monitoring unit 18 that the state has changed to the delay state, (4a) partial data reception interruption (partial data reception interruption is hereinafter also referred to as “session interruption”). 17, (4b) instruct the transmission unit 12 to transmit a session disconnection notification, and (4c) instruct the rearrangement processing unit 16 to rearrange the partial data stored in the buffer 15.

[Configuration of Video Server 2]
Next, the configuration of the main part of the video server 2 will be described with reference to FIG. FIG. 3 is a block diagram showing a main configuration of the video server 2.

  The video server 2 includes a reception unit (partial data acquisition unit) 21, a monitoring unit 22, a response generation unit 23, a header generation unit 24, a footer generation unit 25, a transmission unit (partial data transmission unit) 26, a request generation unit 27, and The management table storage unit 28 is provided.

  The receiving unit 21 receives a request message (content data request) from the video playback device 1 that requests transmission of content data for one playback unit, and generates a request and a request for the received request message (content data request). To the unit 27. In addition, the receiving unit 21 acquires partial data constituting the playback unit requested from the video playback device 1 from the storage 3 and supplies the acquired partial data to the response generation unit 23. Further, the receiving unit 21 receives a session disconnection notification from the video playback device 1 and supplies the received session disconnection notification to the monitoring unit 22.

  The monitoring unit 22 monitors the received data received by the receiving unit 21, the timing at which the receiving unit 21 receives a request message (content data request) from the video playback device 1, and the receiving unit 21 receives a response (partial) from the storage 3. Data) and the timing at which the receiving unit 21 receives the session disconnection notification from the video reproduction device 1. When the monitoring unit 22 confirms that the request message (content data request) from the video playback device 1 has been received, the monitoring unit 22 requests the storage 3 to provide each partial data that constitutes the requested playback unit ( The request generation unit 27 is instructed to generate (partial data request). Further, every time it is confirmed that the response (partial data) from the storage 3 is acquired, the response generation unit 23 is instructed to transmit the acquired partial data. In particular, when it is confirmed that the reception unit 21 has acquired the first partial data, the response generation unit 23 is instructed to transmit the entire header, and when the reception unit 21 has confirmed that the last partial data has been received, The response instruction generation unit 23 is instructed to transmit the symbol. Further, when the reception unit 21 confirms that the session disconnection notification has been received, the transmission unit 26 is instructed to stop transmission of partial data.

  The management table storage unit 28 stores a management table indicating in which storage 3 each partial data constituting the reproduction unit is stored for each reproduction unit of the content data that can be distributed by the video server 2. . This management table includes, for example, reproduction unit designation information for designating each reproduction unit (for example, the URI of the reproduction unit) and storage designation information for designating the storage 3 in which each partial data constituting the reproduction unit is stored ( For example, it is realized by recording a list composed of the IP address or MAC address of the storage 3 in association with each other.

  The request generator 27 generates a request message (partial data request) for requesting provision of the partial data to the storage 3 in which the partial data is stored for each partial data constituting the requested reproduction unit. . The storage 3 in which each partial data constituting the requested reproduction unit is stored refers to the management table stored in the management table storage unit 28, so that the request message (contents) received by the reception unit 21 is stored. It can be specified from the reproduction unit designation information included in the data request. The request message (partial data request) generated by the request generation unit 27 includes an identifier for identifying the partial data to be acquired from other partial data. The request generation unit 27 supplies the generated request message (partial data request) to the transmission unit 26 together with storage designation information for designating the storage 3 that is the transmission destination of the request message (partial data request). Further, the request generation unit 27 supplies the header generation unit 24 with the entire transmission device (in this case, the video server 2) that supplies partial data to the video reproduction device 1.

  The response generation unit 23 generates a response message for the request message (content data request) from the video reproduction device 1 in accordance with the instruction from the monitoring unit 22. Specifically, (1) When the acquisition of the first partial data is confirmed, the header generation unit 24 generates a whole header and a partial header corresponding to the first partial data, and following those headers, The first partial data is transmitted to the transmission unit 26. Thereafter, (2) every time the acquisition of partial data is confirmed, the header generation unit 24 generates a partial header corresponding to the partial data, and the partial data is transmitted to the transmission unit 26 following the partial header. . (3) After the last partial data is transmitted to the transmission unit 26, the delimiter symbol is generated by the header generation unit 24, and the delimiter symbol is transmitted to the transmission unit 26. The whole header, partial header, partial data, and delimiter transmitted from the transmission unit 26 in this way constitute a response message to the request message (content data request) from the video reproduction device 1.

  The header generation unit 24 generates an overall header and a partial header according to instructions from the response generation unit 23. The whole header and the partial header generated by the header generation unit 24 are transmitted to the video reproduction device 1 via the transmission unit 26. Each partial header includes reproduction order designation information that designates the reproduction order of the corresponding partial data, as will be described later. The footer generation unit 25 creates a delimiter indicating the end of the playback unit in accordance with the instruction from the response generation unit 23. The delimiter generated by the footer generation unit 25 is also transmitted to the video reproduction device 1 via the transmission unit 26.

  When the receiving unit 21 receives the request message (content data request) from the video reproduction device 1, the transmitting unit 26 transmits each of the plurality of request messages (partial data request) generated by the request generating unit 27 to each of the request messages. The request message (partial data request) is transmitted to the storage 3 that is the transmission destination. Thereby, acquisition of each partial data is started simultaneously and in parallel. Further, the transmission unit 26 transmits the response message generated by the response generation unit 23 to the video reproduction device 1. When the reception unit 21 receives a session disconnection notification, the transmission unit 26 interrupts transmission of the response message generated by the response generation unit 23, that is, transmission of partial data.

  Note that the video server 2 may be a reverse proxy server. In this case, access to the storage 3 is restricted in response to a request message (content data request) from an unspecified number of video playback devices 1 or the video playback device 1 is prevented from being directly connected to the storage 3. The security of the storage 3 can be increased.

[Configuration of storage 3]
The configuration of the main part of the storage 3 will be described with reference to FIG. FIG. 4 is a block diagram showing a main configuration of the storage 3.

  The storage 3 includes a monitoring unit 31, a read processing unit 32, a storage medium 33, a transmission unit 34, a response generation unit 35, and a reception unit 36.

  The receiving unit 36 receives a request message (partial data request) from the video server 2 and supplies the received request message (partial data request) to the monitoring unit 31 and the read processing unit 32.

  The monitoring unit 31 determines whether the message supplied from the receiving unit 36 is a request message (partial data request). If the message is a request message (partial data request), the monitoring unit 31 changes the request message (partial data request). The read processing unit 32 is instructed to read partial data identified by this identifier from the included identifier.

  The read processing unit 32 reads partial data identified by the identifier included in the request message (partial data request) from the storage medium 33 in accordance with an instruction from the monitoring unit 31. The read processing unit 32 supplies the read partial data to the response generation unit 35.

  The storage medium 33 is a memory in which partial data constituting content data is stored.

  The response generation unit 35 supplies the partial data supplied from the read processing unit 32 to the transmission unit 34. At this time, the response generation unit 35 may process the partial data into a form matching the communication protocol between the storage 3 and the video server 2 and supply the processed data to the transmission unit 34. For example, when the storage 3 and the video server 2 communicate with each other using HTTP, the partial data may be processed into a form that can be communicated with HTTP and supplied to the transmission unit 34.

  The transmission unit 34 transmits the partial data supplied from the response generation unit 35 to the video server 2.

  The configuration of the storage 3 has been described by taking the case where the storage 3 and the video server 2 are connected via the NW 2 as an example. However, the video server 2 may be connected directly to the storage medium 33 of the storage 3. Good. In this case, the monitoring unit 31, the read processing unit 32, the transmission unit 34, the response generation unit 35, and the reception unit 36 described above may be included in the video server 2.

<Embodiment 1>
[Processing of video playback device]
The processing of the video reproduction device 1 will be described with reference to FIG. FIG. 6 is a flowchart showing a processing flow of the video playback device 1 in the content playback processing of the present embodiment. The process shown in FIG. 6 is a process for reproducing content data for one reproduction unit, and the video reproduction apparatus 1 reproduces the entire content data by repeating the process shown in FIG. 6 for each reproduction unit. Is realized.

  The transmission unit 12 of the video reproduction apparatus 1 transmits a request message generated based on a user operation to the video server 2 (step S1, hereinafter simply referred to as S1).

  After transmitting the request message, the monitoring unit 18 waits for a response from the video server 2. That is, until the response from the video server 2 is confirmed (Yes in S2), the process of determining whether or not there is a response from the video server 2 (S2) is repeated. Note that the process of determining whether or not there is a response from the video server 2 is performed by detecting a status line starting from “HTTP / 1.1” or an entire header, for example.

  When the response from the video server 2 is confirmed (Yes in S2), the reception unit 17 receives (one) partial header and (one corresponding to the partial header) transmitted from the video server 2. The process (S3) and the process (S4) for storing the received (one) partial header and the partial data (one corresponding to the partial header) in the buffer 15 are the reception of content data for one playback unit. The process is repeated until the process is completed (YES in S5) or a delay state is reached (No in S6). Here, completion of reception of content data for one playback unit indicates completion of reception of all partial data constituting the playback unit.

  By repeating S3 to S4, a plurality of partial data constituting the requested reproduction unit is accumulated in the buffer 15. However, when the reception of the partial data is interrupted by the delay state (Yes in S6), the partial data stored in the buffer 15 is not all of the partial data constituting the reproduction unit, It becomes a part of a plurality of partial data constituting a reproduction unit. If reception of partial data is interrupted (Yes in S6), the transmission unit 12 notifies the video server 2 of session disconnection (partial data reception interrupt) (S7).

  Whether or not reception of content data for one playback unit has been completed (S5) is determined by the monitoring unit 18 detecting the delimiter received by the receiving unit 17 as described above. When it is confirmed that the reception of the content data is completed (Yes in S5), the monitoring unit 18 instructs the rearrangement processing unit 16 to rearrange the contents stored in the buffer 15.

  In addition, as described above, the monitoring unit 18 compares the time t at which the partial data is received with the time t ′ at which the partial data should be decoded, as described above. Is done. If it is not in the delay state (S6: No), the reception of the partial data is continued without starting the decoding / reproduction process. If it is in the delay state (S6: Yes), the reception of the partial data is interrupted and the decoding / reproduction process is started. To start.

  When reception of content data for one playback unit is completed (Yes in S5) or interrupted (No in S6), the rearrangement processing unit 16 corresponds the partial data stored in the buffer 15 to each partial data. By rearranging with reference to the partial header (including reproduction order designation information), encoded data that can be decoded in order from the top is generated (S8). Thereafter, the decoding unit 14 decodes the content from the encoded data generated by the rearrangement processing unit 14, and the reproduction unit 19 displays the content decoded by the decoding unit 14 (S9).

[Video server processing]
Next, the processing of the video server 2 will be described with reference to FIG. FIG. 7 is a flowchart showing a processing flow of the video server 2 in the content reproduction processing of the present embodiment. Note that the process shown in FIG. 7 is a process for transmitting content data for one playback unit, and the video server 2 transmits the entire content data by repeating the process shown in FIG. 7 for each playback unit. Realize.

  The monitoring unit 22 of the video server 2 waits for a request message (content data request) from the video playback device 1. That is, the process (S10) for determining whether or not there is a request from the video reproduction device 1 is repeated until a request message from the video reproduction device 1 is confirmed. Note that the process of confirming the presence / absence of a request message from the video reproduction device 1 is performed, for example, by detecting a request line starting from “GET” in the received data received by the receiving unit 21.

  When the request message (content data request) from the video reproduction device 1 is confirmed (Yes in S10), the monitoring unit 22 instructs the request generation unit 27 to generate a request message (partial data request). Upon receiving this instruction, the request generation unit 27 refers to the management table stored in the management table storage unit 28, and stores a plurality of partial data constituting the content data for one playback unit requested from the video playback device 1. The storage 3 in which each is stored is specified (S11). Then, the request generation unit 27 requests the storage 3 in which the partial data is provided for each of the plurality of partial data constituting the playback unit requested from the video playback device 1. Request message (partial data request) to be generated.

  The transmission unit 26 performs processing (S12) of transmitting each request message (partial data request) generated by the request generation unit 27, and transmits all the request messages (partial data request) generated by the request generation unit 27. Repeat until completion (Yes in S13). By sending a request message (partial data request) requesting provision of partial data to the storage 3, an acquisition process for acquiring the partial data from the storage 3 is started. Here, the process of transmitting each request message (partial data request) is executed without waiting for a response to another request message (partial data request). Therefore, the process of acquiring each partial data is performed simultaneously and in parallel.

  When it is confirmed that the transmission unit 26 has transmitted all the request messages (partial data request) (Yes in S13), the monitoring unit 22 receives the request message (partial data request) transmitted in S12 from the storage 3. Wait for the first response. That is, until the receiving unit 21 receives the first response from the storage 3, the process of determining whether or not the receiving unit 21 has received the response from the storage 3 (S14) is repeated.

  When it is confirmed that the reception unit 21 has acquired the first response (partial data) from the storage 3 (Yes in S14), the monitoring unit 22 instructs the response generation unit 23 to transmit the entire header. Upon receiving this instruction, the response generation unit 23 instructs the header generation unit 24 to generate the entire header and also instructs the transmission unit 26 to transmit the entire header. Upon receiving this instruction, the transmission unit 26 transmits the entire header generated by the header generation unit to the video reproduction device 1 (S15).

  When the transmitting unit 26 confirms that the transmission of the entire header has been completed, the monitoring unit 22 instructs the response generating unit 23 to transmit the first acquired partial data. Upon receiving this instruction, the response generation unit 23 instructs the header generation unit 24 to generate a partial header corresponding to the first acquired partial data, and also instructs the transmission unit 26 to transmit the first acquired partial data. Upon receiving this instruction, the transmitting unit 26 transmits the first acquired partial data to the video reproduction device 1 together with the partial header generated by the header generating unit 24 (first time S16).

  Thereafter, the monitoring unit 22 instructs the response generation unit 23 to transmit the acquired partial data each time the receiving unit 21 acquires a response (partial data) from the storage 3 (Yes in S18). Upon receiving this instruction, the response generation unit 23 instructs the header generation unit 24 to generate a partial header corresponding to the acquired partial data, and also instructs the transmission unit 26 to transmit the acquired partial data. Each time the transmission unit 26 receives this instruction, the transmission unit 26 transmits the partial data acquired by the reception unit 21 to the video reproduction device 1 together with the partial header generated by the header generation unit 24 (second and subsequent S16). The transmission process (S16) of the partial data by the transmission unit 26 is repeated until all the partial data constituting the reproduction unit is obtained from the storage 3 (Yes in S17). As a result, all the partial data constituting the content data for one playback unit can be transmitted to the video playback device 1 in the order obtained from the storage 3.

  When the reception unit 21 has received all the partial data constituting the content data for one playback unit (Yes in S17), the monitoring unit 22 instructs the response generation unit 23 to transmit a delimiter. Upon receiving this instruction, the response generation unit 23 instructs the footer generation unit 25 to generate a delimiter, and also instructs the transmission unit 26 to transmit the delimiter generated by the footer generation unit 25. Upon receiving this instruction, the transmission unit 26 transmits the delimiter generated by the footer generation unit 25 to the video reproduction device 1 (S19).

[Communication system operation example 1]
Next, an operation example of the communication system 100 will be described with reference to FIG. FIG. 10 is a sequence diagram illustrating an operation example of the communication system 100. The operation example in FIG. 10 is an example in which the video server 2 can acquire all the partial data constituting the content data for one playback unit without delay.

  In FIG. 10, the reproduction unit is composed of two partial data, the first partial data (hereinafter referred to as partial data a) is stored in the storage 3a, and the second partial data (hereinafter referred to as partial data a). , Described as partial data b) is stored in the storage 3b as an example. Also, the processing performed by the video playback device 1 and the processing performed by the video server 2 are the same as those in FIGS. 6 and 7, respectively, and therefore are given the same numbers and are not described here.

  First, the video playback device 1 requests the video server 2 to transmit content data for one playback unit (S101). Next, the video server 2 requests the storage 3a and the storage 3b to provide the partial data a and the partial data b constituting the requested reproduction unit (S102, S103).

  When the video server 2 completes the acquisition of the partial data b from the storage 3b (S104), the video server 2 transmits the entire header to the video playback device (S105). Further, the acquired partial data b is transmitted to the video reproduction apparatus 1 together with the partial header (2 ') corresponding to the partial data b (S106).

  The video server 2 transmits the remaining partial data a to the video reproduction device 1 together with the partial header (1 ′) corresponding to the partial data a when the acquisition from the storage 3a (S107) is completed (S108). ).

  When the video server 2 finishes transmitting all the partial data constituting the content data for one playback unit to the video playback device 1, the video server 2 transmits a delimiter indicating the end of the playback unit to the video playback device 1 (S109). When receiving the delimiter from the video server 2, the video playback device 1 rearranges (S8), decodes and plays back the partial data ab received so far (S9).

  In this way, the video server 2 transmits the partial data constituting each playback unit to the video playback device 1 in order from the acquisition of the partial data. However, since the video server 2 transmits each partial data constituting each playback unit to the video playback device 1 together with a partial header including playback order specification information, the video playback device 1 refers to this playback order specification information. Thus, the received partial data can be rearranged and reproduced.

  This point will be described in more detail with reference to FIG. Here, it is assumed that a reproduction unit is composed of three partial data, and the reproduction order is partial data a, partial data b, and partial data c.

  When the video server 2 acquires these three partial data a to c from the storages 3 a to 3 c in the order of the partial data a, the partial data c, and the partial data b, the three partial data a to c are converted to the partial data a. , Partial data c, and partial data b are transmitted to the video reproduction apparatus 1 in this order. For this reason, the transmission order in which the video server 2 transmits the partial data ac to the video reproduction device 1, that is, the reception order in which the video reproduction device 1 receives the partial data ac from the video server 2 is the partial data a to c. It is not the reproduction order of c, but the acquisition order in which the video server 2 acquires the partial data ac from the storages 3a to 3c.

  However, the video server 2 transmits the partial header (1 ') including the playback order designation information for designating the playback order (first) of the partial data a to the video playback device 1 together with the partial data a. Similarly, the partial header (3 ′) including the reproduction order designation information for designating the reproduction order (third) of the partial data c is transmitted to the video reproduction apparatus 1 together with the partial data c, and the reproduction order (2 of the partial data b is selected). The partial header (2 ′) including the reproduction order designation information designating the (th) is transmitted to the video reproduction apparatus 1 together with the partial data b. For this reason, the video reproduction apparatus 1 refers to these three partial headers (1 ′) to (3 ′) to convert the three partial data ac to the reproduction order (partial data a, partial data b, partial The data can be rearranged in the order of data c).

[Operation example 2 of communication system]
Next, another operation example of the communication system 100 will be described with reference to FIG. FIG. 12 is a sequence diagram illustrating another operation example of the communication system 100. The example shown in FIG. 12 is an example in a case where the video server 2 cannot acquire some partial data constituting the content data for one playback unit without delay.

  Note that FIG. 12 will be described by taking as an example a case where the content data is composed of two partial data as in FIG. Since the processing performed by the video playback device 1 and the processing performed by the video server 2 are the same as those in FIGS. 6 and 7, respectively, the same reference numerals are given and description thereof is omitted. The same processes as those in FIG. 10 are also given the same numbers.

  First, the video reproduction device 1 requests the video server 2 to transmit content data designated by the user (S101). Next, the video server 2 requests the storage 3a and the storage 3b to provide the partial data a and the partial data b constituting the requested content data (S102, S103).

  When the video server 2 completes the acquisition of the partial data b from the storage 3b (S104), the video server 2 transmits the entire header to the video playback device (S105). In addition, the video server 2 transmits the acquired partial data b together with the partial header (2 ') corresponding to the partial data b to the video playback device 1 (S106).

  In the example shown in FIG. 12, since the reception of the partial data b has been delayed, the video reproduction device 1 notifies the video server 2 that the session has been disconnected (partial data reception is interrupted) (S110). When the notification of session disconnection is received, the video server 2 stops transmission of the remaining partial data a. On the other hand, when notifying that the session is disconnected, the video reproduction device 1 rearranges (S8), decodes, and reproduces the partial data received so far (S9). However, in this example, since the partial data received so far is only the partial data a, the video reproduction device 1 decodes and reproduces the received partial data a without rearranging (S9).

[Specific example of request message]
Next, details of the request message used in the sequence diagrams of FIGS. 10 and 12 will be described with reference to FIG. FIG. 8A shows an HTTP message which is an example of a request message (content data request) transmitted from the video reproduction device 1 to the video server 2 in FIGS. 10 and 12.

  As shown in FIG. 8A, the request message includes a request line and an “Accept” field. “HTTP / 1.1” indicating that this message is an HTTP message is described at the end of the request line, and “GET” indicating that this message is an acquisition method (request message) is described at the top of the request line. Is described. Also, between these, reproduction unit designation information (/ content1 / 4000000/1) for designating a reproduction unit to be acquired is described. The “Accept” field is a field that indicates a data format that can be processed by the video reproduction device 1, and here, fragmented MPEG4 transmitted in a multipart format is designated.

[Specific example of response message]
Next, details of the response message (content data for one playback unit) used in the sequence diagrams of FIGS. 10 and 12 will be described with reference to FIG. FIG. 9 is a diagram illustrating an HTTP message that is an example of a response message (content data for one playback unit) transmitted from the video server 2 to the video playback device 1 in FIGS. 10 and 12.

  As shown in FIG. 9, the HTTP message transmitted from the video server 2 to the video playback device 1 includes a status line, overall header information, partial header, partial data, and a delimiter.

  In the status line, “HTTP / 1.1” indicating that this message is an HTTP message and a status number “200” indicating that the request has been normally received are described.

  The overall header includes information (Content-Location) indicating the location of the playback unit (media segment) transmitted in this response message, and the playback unit transmitted in this response message is the number of playback units in the content data. ("X-Media-Fragment-Index") indicating whether or not.

  The partial header includes a time stamp (X-timestamp) indicating the presentation time of the corresponding partial data, information (X-Bitrate) indicating the bit rate indicating the corresponding partial data, and the like. In this example, this time stamp is used as reproduction order designation information for designating what number the corresponding partial data is to be reproduced.

  The partial data is binary data (movie fragment) obtained by dividing the encoded data. The part of “{binary-data: movie fragment t}” (t = 0,1,2, ...) is a simplified description of the binary data of each partial data. It does not mean that the text data “{binary-data:…}” is included.

  A delimiter is included at the end of each playback unit. In this example, a command (“X-ProcessCommand: sort”) for instructing the video reproduction apparatus 1 to execute partial data rearrangement is used as a delimiter. The delimiter is not limited to this and may be a character string that can be identified as a delimiter. For example, in FIG. 13, a character string “0” is used as a delimiter.

  FIG. 13 is another example of the response message transmitted from the video server 2 to the video playback device 1 in FIGS. 10 and 12. In FIG. 13, chunk transfer in HTTP is used.

  The entire header of FIG. 13 describes “Transfer-Encoding: chunked” indicating chunk transfer. In this response message, as described above, “0” is used as a delimiter.

  In FIG. 11, the last partial data (partial data transmitted from the video server 2 to the video playback device 1 at the end of the partial data constituting the playback unit) is transferred from the video server 2 to the video playback device 1. Although the configuration in which the delimiter is transmitted after being transmitted is shown, the method of transmitting the delimiter is not limited to this. For example, the delimiter may be described in the partial header corresponding to the last partial data.

  This point will be described in more detail with reference to FIG. Here again, it is assumed that the reproduction unit is composed of three partial data, and the reproduction order is partial data a, partial data b, and partial data c.

  The video server 2 first completes the acquisition of the partial data a and the partial header (1) corresponding to the partial data a stored in the storage 3a, and then the partial data c and the partial header corresponding to the partial data c ( 3) is acquired second, and the partial data b and the partial header (2) corresponding to the partial data b are finally acquired.

  Since the video server 2 transmits each partial data to the video playback device 1 in the order received, regardless of the playback order specified by each partial header, the video playback device 1 stores the partial data a and the partial data c. Partial data is transmitted in order. After the partial data c is transmitted, the video server 2 describes a delimiter in the partial header (2 ') corresponding to the partial data b, and then transmits the partial data b to the video reproduction device 1.

  In addition, the delimiter may be transmitted when there is only one partial data constituting the content data, or may not be transmitted.

<Embodiment 2>
A second embodiment of the present invention will be described below with reference to FIGS.

  As described above, the communication system according to the first embodiment has a configuration in which the video reproduction apparatus 1 rearranges content data for each reproduction unit. For this reason, in the video reproduction device 1 in which the size of the buffer 15 (hereinafter also referred to as “buffer size”) is smaller than the data size of the reproduction unit, content data for one reproduction unit cannot be stored in the buffer. This will hinder the sorting of content data.

  Therefore, in the present embodiment, the content data rearrangement in the video playback device 1 is not performed for each playback unit, but is performed for each small playback unit set according to the buffer size of the video playback device 1. adopt. As a result, any video playback apparatus 1 that receives content data supplied from the video server 2 does not interfere with the rearrangement of the content data.

  FIG. 15 shows the configuration of content data distributed to the video playback device 1 whose buffer size is X. As shown in FIG. 15, in the content data distributed to the video reproduction device 1 whose buffer size is X, each reproduction unit Ui is a small reproduction unit (data size smaller than the buffer size X of the video reproduction device 1). Divided into small parts).

[Video server processing]
Next, processing of the video server 2 of the present embodiment will be described with reference to FIG. FIG. 16 is a flowchart showing the flow of processing in the video server 2 of the present embodiment. Among these, the processes of S10 to S19 are the same as the processes shown in FIG. However, the request message (content data request) from the video playback device 1 includes buffer size information (X-Accept-Buffer-Size) indicating the buffer size of the video playback device 1, as shown in FIG. 8B. Become a request message.

  Since the processes of S10 to S19 are the same as the processes shown in FIG. 7, the process executed by the request generation unit 27 in S20 will be mainly described here.

  The request generation unit 27 stores the partial data included in each small playback unit in the buffer size information included in the request message (content data request) from the video playback device 1 and the management table storage unit 28. Identify by referring to the management table. At this time, the total data size (described in the management table) of the partial data included in the small playback unit is set to be smaller than the buffer size (described in the request message) of the video playback device 1. For example, when the buffer size specified by the buffer size specification information is 8M bits and the data size of each partial data is 1M bits, the first partial playback of the 8 partial data from the beginning of the requested playback unit Specify as partial data to be included in the unit.

  Further, the request generation unit 27 specifies the storage 3 storing the partial data to be included in each small reproduction unit with reference to the management table stored in the management table storage unit 28, and specifies the specified storage 3 ( More precisely, a storage list including storage specification information for specifying the specified storage is generated. Then, the request generator 27 generates a request message (partial data request) for requesting provision of partial data to each storage 3 included in the storage list.

  Thus, when the transmission of the partial data included in each small reproduction unit is completed (Yes in S17), the delimiter is transmitted (S19). The video server 2 completes the transmission of content data for one playback unit by repeating such transmission processing for each small playback unit.

[Operation example of communication system]
Next, an operation example of the communication system 100 according to the present embodiment will be described with reference to FIG. FIG. 17 is a diagram illustrating the operation of the communication system 100 according to the flow of content data in the communication system 100.

  In the example shown in FIG. 17, the reproduction unit is composed of six partial data. Assuming that the buffer size of the video reproduction apparatus 1 is X, the data size of the partial data a is Sa, the data size of the partial data b is Sb,..., And the data size of the partial data f is Sf, The video server 2 constitutes the first small reproduction unit by the three partial data a to c. Since Sd <Sd + Se <Sd + Se + Sf <X holds, the video server 2 forms the second small reproduction unit by the remaining three partial data d to f.

  First, the video server 2 acquires from the storages 3a to 3c three partial data a to c constituting the first small reproduction unit constituting the first small reproduction unit. When the three partial data a to c constituting the first small reproduction unit are acquired from the storage 3a, the storage 3c, and the storage 3b in the order of the partial data a, the partial data c, and the partial data b, the video server 2 Two pieces of partial data a to c are transmitted to the video reproduction apparatus 1 in the order of partial data a, partial data c, and partial data b. When the transmission of these three partial data a to c is completed, the video server 2 transmits a delimiter to the video playback device 1. On the other hand, when the video reproducing apparatus 1 receives this delimiter, it executes a rearrangement process on the partial data stored in the buffer 15, that is, the three partial data a to c constituting the first small reproduction unit. To do.

  Next, the video server 2 acquires from the storages 3d to 3f three pieces of partial data d to f constituting the second small reproduction unit. When the three partial data d to f constituting the second small reproduction unit are acquired from the storage 3e, the storage 3d, and the storage 3f in the order of the partial data e, the partial data d, and the partial data f, the video server 2 The three partial data d to f are transmitted to the video reproduction device 1 in the order of partial data e, partial data d, and partial data f. When the transmission of these three partial data ef is completed, the video server 2 transmits a delimiter to the video playback device 1. On the other hand, when the video reproducing apparatus 1 receives this delimiter, the video reproducing apparatus 1 performs a rearrangement process on the partial data stored in the buffer 15, that is, the three partial data a to c constituting the second small reproduction unit. Run.

  As described above, the video server 2 of the present embodiment transmits a delimiter to the video playback device 1 every time transmission of partial data constituting each small playback unit is completed. On the other hand, the video reproduction apparatus 1 of the present embodiment rearranges the partial data stored in the buffer 15 every time a delimiter is received. For this reason, the total data size of the partial data waiting for the rearrangement process can be suppressed to be equal to or smaller than the buffer size of the video reproduction device 1.

  Note that the video server 2 starts acquiring the partial data d to f constituting the second small reproduction unit (acquisition from the storages 3d to 3f) because the partial data ac constituting the first small reproduction unit is started. Acquisition (acquisition from the storages 3a to 3c) is completed or interrupted. That is, before the transmission of the partial data a to c constituting the first small reproduction unit (transmission to the video reproduction device 1) is completed or interrupted, the partial data df constituting the second small reproduction unit is completed. Transmission (transmission to the video reproduction apparatus 1) is not started. Therefore, the total data size of the partial data waiting for the rearrangement process does not exceed the buffer size of the video reproduction device 1.

  Note that FIG. 17 shows a configuration in which the delimiter is transmitted after the last partial data (the partial data constituting each small playback unit is the last in the acquisition order). It is not limited to this. For example, as shown in FIG. 18, a configuration in which a symbol is described in a partial header corresponding to the last partial data may be adopted.

  FIG. 19 shows a configuration example of a response message corresponding to the transmission method shown in FIG. Of the two partial headers included in the response message shown in FIG. 19, the upper partial header is a partial header in which no delimiter is described, and the lower partial header is a partial header in which a delimiter is described. It is. In this implementation, a command (“X-ProcessCommand: sort”) that instructs the video playback device 1 to execute rearrangement of partial data is described as a delimiter in the lower partial header.

<Embodiment 3>
A third embodiment of the present invention will be described below with reference to FIGS.

  As described above, the communication system according to the first embodiment employs a configuration in which each fragment obtained by dividing encoded data is transmitted as partial data to the video reproduction apparatus 1. Accordingly, when certain partial data is lost, the video reproduction device 1 hinders decoding of a reproduction unit including the partial data.

  Therefore, in the present embodiment, a packet is generated by adding an erasure correction code such as an FEC (Forward Error Correction) code to each fragment obtained by dividing the encoded data, and a packet group including a plurality of packets. Is adopted as a partial data to be transmitted to the video reproduction apparatus 1. Thereby, even if some partial data is lost, the video reproduction device 1 can decode the reproduction unit from the remaining partial data.

  An example of a method for generating such partial data is shown in FIG. In the example shown in the figure, the encoded data is divided into a plurality of reproduction units U1, U2,..., UM, and four partial data Uia, Uib, Uic, Uid are generated from each reproduction unit Ui. . At this time, even if any one of the four partial data Uia, Uib, Uic, Uid is missing in the four partial data Uia, Uib, Uic, Uid generated from each reproduction unit, the reproduction unit Redundancy is added so that Ui can be reproduced.

  Here, a configuration is shown in which four partial data are generated from each reproduction unit, and the reproduction unit can be reproduced from three partial data of these four partial data. However, the present invention is not limited to this. . That is, M partial data (M is a natural number of 2 or more) is generated from each reproduction unit, and the reproduction unit can be reproduced from N partial data (N is a natural number smaller than M) among these M partial data. Can be generalized to

  For example, if the four partial data Uia, Uib, Uic, Uid generated from each reproduction unit Ui are distributed and accumulated in the four storages 3a to 3d, among these four storages 3a to 3d, Even if a failure occurs in any one of them and the reading is delayed, it is possible to construct a content distribution system that does not hinder video playback in the video playback device 1.

  Examples of FEC codes that can add such redundancy include Reed-Solomon codes, LDPC (Low Density Parity Check) codes, and Raptor FEC. Note that a technique for generating a erasure-correctable packet group from encoded data using an FEC (Forward Error Correction) code is a technique that has already been put into practical use in the video distribution field such as VOD. Detailed explanation is omitted.

[Processing of video playback device]
Next, the flow of processing in the video playback apparatus 1 of this embodiment will be described with reference to FIG. FIG. 21 is a flowchart showing the flow of processing in the video reproduction apparatus 1 of the present embodiment. Among these, the process of S1-S9 is the same as the process which attached | subjected the same referential mark and was shown in FIG.

  However, as described later, the video server 2 according to the present embodiment has completed transmission of all the partial data (four partial data Uia, Uib, Uic, Uid in the example of FIG. 20) constituting each playback unit. The transmission of the partial data necessary for restoring each reproduction unit (any three of the four partial data Uia, Uib, Uic, Uid in FIG. 20) is completed. Send the delimiter at the stage you did. Therefore, it is determined that the video playback apparatus 1 has received the partial data for one playback unit (Yes in S5), not the time when the reception of all the partial data constituting the playback unit is completed, This is the time when the reception of the partial data necessary for restoring the reproduction unit is completed.

  When the reception of the partial data necessary for restoring each reproduction unit is completed (Yes in S5), the rearrangement processing unit 16 converts the partial data stored in the buffer 15 into partial headers corresponding to the partial data ( Reordering is performed with reference to (including reproduction order designation information) (S8), and the decoding unit 14 further performs FEC decoding on the partial data rearranged by the rearrangement processing unit 16, thereby restoring the encoded data ( S22). Thereafter, the decoding unit 14 decodes the content from the restored encoded data, and the reproduction unit 19 displays the content decoded by the decoding unit 14 (S9).

[Video server processing]
Next, the flow of processing in the video server 2 of this embodiment will be described with reference to FIG. FIG. 22 is a flowchart showing the flow of processing in the video server 2 of the present embodiment. Among these, the process of S11-S19 is the same as the process which attached | subjected the same referential mark and was shown in FIG.

  The flowchart shown in FIG. 22 is a modification of the flowchart shown in FIG. 7 so that the delimiter is transmitted after the transmission of the partial data required for restoring each reproduction unit is completed. That is, steps S23 to S25 described below are added to the flowchart shown in FIG. 7, and the value of the counter indicating the number of transmitted partial data reaches the number of partial data necessary to restore the reproduction unit. Thus, the delimiter transmission process S19 is executed.

  The process S23 is a process of clearing a counter indicating the number of transmitted partial data after completing the entire header transmission process S15. Specifically, this is a process of initializing the counter value to zero. The process S24 is a process of updating the counter value described above every time the transmission process S16 of each partial data is completed. Specifically, this is a process of incrementing the counter value by one. The process S25 is a process for determining whether or not the updated counter value is smaller than the threshold value every time the above-described counter update process S24 is completed. When the updated counter value reaches the number of partial data necessary to restore the reproduction unit, a delimiter transmission process S19 is executed. The threshold is a value set in advance as the number of partial data necessary to restore each reproduction unit, and the FEC coding rate to be used (the size of the original coded data and the size of the erasure correction code). Ratio).

[Specific example of response message]
FIG. 23 is a diagram exemplifying a response message (content data for one playback unit) transmitted from the video server 2 that performs the processing of FIG. 22 to the video playback device 1. The response message shown in FIG. 23 is configured as a multipart HTTP message, and includes a status line, whole header information, a partial header, partial data, and a delimiter.

  A characteristic feature of this response message is that encoding method specification information (“Content-Encoding”) for specifying the encoding method of content data is described in the header, and an FEC code (Raptor FEC) is used as the encoding method. It is a specified point. Further, a command (“X-ProcessCommand: sort, raptor_dec”) for instructing the video playback apparatus 1 to execute the partial data rearrangement process and the FEC decoding is used as a delimiter indicating the end of each playback unit. It is a point.

  Note that the command used as a delimiter is not limited to the example shown in FIG. 23 as long as it specifies a process to be executed by the video reproduction apparatus 1 when the delimiter is received. For example, the example shown in FIG. 23 explicitly instructs execution of these two processes when the rearrangement process and the FEC decoding process are implemented as separate processes. Is implemented as part of the FEC decoding process, the description “sort” that instructs execution of the rearrangement process becomes unnecessary.

  In the present embodiment, the response message transmitted from the video server 2 to the video playback device 1 may also be a response message using chunk transfer as described with reference to FIG. The delimiter may be described in the partial header corresponding to the last partial data as described with reference to FIG.

<Application Examples of Embodiments 1, 2, and 3>
In each of the above-described embodiments, an example in which the request and transmission of content data is performed using an HTTP message has been described. However, the present invention is not limited to this example, and any message used for requesting and transmitting content data can be applied.

  In each of the above embodiments, the video server 2 registers a request message (partial data request) for requesting provision of each partial data in the management table in advance as one storage (storage storing the partial data). 1 is used, but the present invention is not limited to this. For example, the video server 2 may adopt a configuration in which a request message (partial data request) for requesting provision of each partial data is transmitted to N storages (N ≧ 2). That is, a configuration in which each partial data is acquired in parallel from N storages may be employed. As a case where such a configuration is suitable, there is a case where each partial data constituting the content data is accumulated in at least one (preferably two or more) of the N storages. In this case, when the partial data is provided from any one of the N storages, the video server 2 (without waiting for provision of partial data from the other N-1 storages). It is desirable to transmit the provided partial data to the video reproduction apparatus 1. As a result, the provision of the content data to the video reproduction device 1 can be executed more smoothly. In addition, a request message may be transmitted by selecting a storage with sufficient processing capacity.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  Finally, each block of the video reproduction device 1, the video server 2, and the storage 3, especially the control unit 13, the monitoring unit 18, the monitoring unit 22, and the monitoring unit 31, are logical circuits formed on an integrated circuit (IC chip). May be realized in hardware, or may be realized in software using a CPU (Central Processing Unit).

  In the latter case, the video playback device 1, the video server 2, and the storage 3 include a CPU that executes instructions of a program that realizes each function, a ROM (Read Only Memory) that stores the program, and a RAM ( Random Access Memory) and a storage device (recording medium) such as a memory for storing the program and various data. An object of the present invention is to provide program codes (execution format program, intermediate code program, source program) of control programs for the video playback apparatus 1, video server 2, and storage 3 which are software for realizing the above-described functions. By supplying the readable recording medium to the video reproduction apparatus 1, the video server 2, and the storage 3, the computer (or CPU or MPU) reads and executes the program code recorded on the recording medium. Is also achievable.

  Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, and disks including optical disks such as CD-ROM / MO / MD / DVD / CD-R. IC cards (including memory cards) / optical cards, semiconductor memories such as mask ROM / EPROM / EEPROM / flash ROM, PLD (Programmable logic device), FPGA (Field Programmable Gate Array), etc. Logic circuits can be used.

  The program code may be supplied to the video reproduction device 1, the video server 2, and the storage 3 via a communication network. The communication network is not particularly limited as long as it can transmit the program code. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication network, and the like can be used. The transmission medium constituting the communication network may be any medium that can transmit the program code, and is not limited to a specific configuration or type. For example, even with wired lines such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, and ADSL (Asymmetric Digital Subscriber Line) line, infrared rays such as IrDA and remote control, Bluetooth (registered trademark), IEEE 802.11 wireless, HDR ( It can also be used by radio such as High Data Rate (NFC), Near Field Communication (NFC), Digital Living Network Alliance (DLNA), mobile phone network, satellite line, and digital terrestrial network.

(Preferred form of the present invention)
In the transmission apparatus according to the present invention, when the partial data acquisition unit is requested to transmit the specific part of the content data from the other apparatus, the partial data belonging to the specific part is parallelly transmitted to the one or more partial data. The partial data transmission means obtains from the storage device, and the partial data transmission means transmits the partial data belonging to the specific part after the transmission to the other device or the last of the partial data belonging to the specific part. It is preferable that information indicating that transmission of the specific part is completed is transmitted to the other device in association with the partial data to be transmitted.

  According to the above configuration, another device can receive the partial data constituting each part (specific part) constituting the content data without delay.

  In the transmission apparatus according to the present invention, when the partial data acquisition unit is requested to transmit the specific part of the content data from the other apparatus, the partial data acquisition unit belongs to each small part obtained by dividing the specific part. The partial data is acquired from the one or more storage devices in parallel, and the partial data transmitting means transmits the partial data belonging to each small portion to the other device each time or after the transmission. It is preferable that information indicating that the transmission of the small part is completed is transmitted to the other device in association with the partial data to be transmitted last among the partial data belonging to the part.

  According to said structure, the other apparatus can rearrange the partial data which comprises each part (specific part) which comprises content data for every small part. Therefore, the above configuration is advantageous when the size of the buffer for storing the partial data to be rearranged is small.

  In the transmission device according to the present invention, the request from the other device includes buffer size designation information indicating the buffer size of the other device, and the partial data acquisition means includes a portion belonging to each small portion. It is preferable that the specific portion is divided so that the total data size of the data is smaller than the buffer size specified by the buffer size specifying information.

  According to the above configuration, regardless of the size of the buffer that stores the partial data to be rearranged, other devices can rearrange the partial data without any problem.

  In the transmission apparatus according to the present invention, when the partial data acquisition unit is requested to transmit the specific part of the content data from the other apparatus, the M parts obtained by encoding the specific part M pieces of partial data that can be restored from the N pieces (N <M) of partial data by erasure correction are acquired from the one or more storage devices in parallel. The partial data transmission means is for transmitting the N partial data acquired previously from the M partial data acquired by the partial data acquisition means to the other apparatus in the order in which the acquisition has been completed. After the transmission of the N partial data to the other device, or in association with the last partial data to be transmitted among the N partial data, the transmission of the specific part is completed. information To send to the other device, it is preferable.

  According to said structure, when content data is encoded so that erasure | elimination correction | amendment is possible, content data can be transmitted more efficiently.

  In the transmission device according to the present invention, the partial data transmission means transmits the partial data constituting the specific part and information indicating that the transmission of the partial data is completed as a multipart HTTP message. It is preferable.

  According to said structure, the some partial data transmitted with respect to one request | requirement can be transmitted as one HTTP message.

  Note that a communication system including the above-described transmission device and reception device is also included in the scope of the present invention.

  Further, the data structure of the content data transmitted from the transmission device described above (that is, a plurality of partial data constituting the content data, and reproduction order designation information associated with each of the plurality of partial data, The data structure of the content data characterized by including reproduction order designation information for designating the reproduction order of the data is also included in the category of the present invention.

  Furthermore, a program for operating a computer as the above-described transmitting device, a program for operating the computer as the above-described receiving device, and a computer-readable recording medium on which these programs are recorded are also within the scope of the present invention. included.

  The present invention can be used for an apparatus that transmits or receives content data via a communication network.

DESCRIPTION OF SYMBOLS 100 Communication system 1 Video | video reproduction apparatus 11 Request production | generation part 12 Transmission part 13 Control part 14 Decoding part 15 Buffer 16 Rearrangement process part (partial data rearrangement means)
17 Receiving part (partial data receiving means)
18 Monitoring unit 19 Playback unit 2 Video server 21 Receiving unit (partial data acquisition means)
22 monitoring unit 23 response generation unit 24 header generation unit 25 footer generation unit 26 transmission unit (partial data transmission means)
27 Request generation unit 28 Management table storage unit 3 Storage 3a to 3f Storage 31 Monitoring unit 32 Read processing unit 33 Storage medium (storage device)
34 transmitter 35 response generator 36 receiver

Claims (14)

Partial data acquisition means for acquiring each of a plurality of partial data constituting the content data from one or a plurality of storage devices when transmission of the content data is requested from another device;
Each of the plurality of partial data acquired by the partial data acquisition unit is associated with reproduction order designation information for designating the reproduction order of the partial data, and is transmitted to the other device in the order in which the partial data acquisition unit completes acquisition. A partial data transmission means for transmitting,
A transmission apparatus characterized by the above. The partial data acquisition means acquires partial data belonging to the specific part from the one or more storage devices in parallel when the transmission of the specific part of the content data is requested from the other device. ,
The partial data transmitting means is configured to transmit the partial data belonging to the specific part after the transmission to the other device or in association with the partial data to be transmitted last among the partial data belonging to the specific part. Sending information indicating that the transmission of the part is completed to the other device,
The transmission apparatus according to claim 1, wherein: When the partial data acquisition means is requested to transmit the specific part of the content data from the other device, the partial data acquisition means reads the partial data belonging to each small part obtained by dividing the specific part in parallel with the 1 Or obtained from a plurality of storage devices,
The partial data transmitting means transmits the partial data belonging to each small part every time it completes transmission to the other apparatus or in association with the partial data to be transmitted last among the partial data belonging to the small part. Information indicating that the transmission of the part is completed is transmitted to the other device.
The transmission apparatus according to claim 1, wherein: The request from the other device includes buffer size designation information indicating the buffer size of the other device,
The partial data acquisition means divides the specific portion so that the total data size of the partial data belonging to each small portion is smaller than the buffer size specified by the buffer size specification information.
The transmission apparatus according to claim 3. When the partial data acquisition unit is requested by the other device to transmit a specific part of the content data, the partial data acquisition unit is M partial data obtained by encoding the specific part, Acquiring M partial data capable of restoring the specific part from N (N <M) partial data in parallel from the one or more storage devices,
The partial data transmission means transmits N partial data acquired previously among the M partial data acquired by the partial data acquisition means to the other device in the order of completion of acquisition. After the transmission of the N partial data to the other device, or in association with the partial data to be transmitted last among the N partial data, the transmission of the specific part is completed. Send information to the other device,
The transmission apparatus according to claim 1, wherein:   3. The partial data transmission means transmits partial data constituting the specific part and information indicating that transmission of the partial data is completed as a multipart HTTP message. The transmission device according to any one of? Partial data receiving means for receiving a plurality of partial data constituting the content data together with reproduction order designation information associated with each of the plurality of partial data;
Partial data rearranging means for rearranging the plurality of partial data received by the partial data receiving means in the reproduction order specified by the reproduction order designation information received by the partial data receiving means;
A receiving apparatus comprising:   A communication system comprising: the transmission device according to any one of claims 1 to 6; and the reception device according to claim 7. A transmission method in which a transmission device transmits content data,
A partial data acquisition step of acquiring each of a plurality of partial data constituting the content data from one or a plurality of storage devices when transmission of the content data is requested from another device;
Each of the plurality of partial data acquired in the partial data acquisition step is associated with reproduction order designation information for specifying the reproduction order of the partial data, and the other data is acquired in the order in which acquisition is completed in the partial data acquisition step. A partial data transmission step for transmitting to the device,
A transmission method characterized by the above. A receiving method in which a receiving device receives content data,
A partial data receiving step of receiving a plurality of partial data constituting the content data together with reproduction order designation information associated with each of the plurality of partial data;
A partial data rearrangement step of rearranging the plurality of partial data received in the partial data reception step in a reproduction order designated by the reproduction order designation information received in the partial data reception step. ,
And a receiving method. In the data structure of content data,
A plurality of partial data constituting the content data;
Reproduction order designation information associated with each of the plurality of partial data, including reproduction order designation information for designating the reproduction order of the partial data.
A data structure of content data characterized by the above.   A program for causing a computer to operate as the transmission device according to any one of claims 1 to 6, wherein the program causes the computer to function as each unit included in the transmission device.   A program for causing a computer to operate as the receiving device according to claim 7, wherein the program functions as each of the means included in the receiving device.   A computer-readable recording medium on which the program according to claim 12 or 13 is recorded.

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