WO2008069032A1 - Dynamic image distribution system, dynamic image distribution device, and dynamic image distribution method - Google Patents

Abstract

It is possible to provide a technique to reduce a user wait time in a system for distributing a dynamic image content. A transmission device includes: means for transmitting head data in a content group as a reproduction candidate of a reception device; means for adjusting the quality of all the head data to be transmitted to the reception device to such a quality that the data can be transmitted during an initialization time indicating a period from specification of the reproduction candidate in the reception device to the completion of reception of the head data; and means for transmitting the subsequent data concerning the reproduction candidate content requested from the reception device. Moreover, the reception device includes means for representing reproduction candidates so as to be selected upon completion of the reception of the head data, requesting the transmission device for the data subsequent to the content selected from the reproduction candidates, and reproducing the head data in the content.

Description

 Specification

 Moving image distribution system, moving image distribution apparatus, and moving image distribution method

 Technical field

 [0001] The present invention relates to a technique for distributing content composed of moving image data, and more particularly to a technique for transmission control in the initial stage of distribution.

 Background art

 [0002] Unlike a system of analog television that demodulates and displays received radio waves, a system that transmits a moving image digital signal has a delay between reception of encoded data and reproduction. In view of the occurrence of this delay, the moving picture coding system defined by MPEG (Moving Picture Experts Group) etc. uses inter-frame prediction technology!

 [0003] Since the code amount of a frame differs from frame to frame, fluctuations occur in the reception time of frame data in a viewing environment where the band is limited. In the bidirectional inter-frame prediction technique, encoding is performed by changing the encoding order of frames, and therefore reception delay occurs in some frames. In addition, in the on-demand type in which only the content requested by the viewer is transmitted, there is a delay in the transmission time from when the viewer requests viewing to when data is received.

 [0004] In consideration of the occurrence of the delay as described above, in order to play back content immediately when playback is requested, or to play back multiple content without interruption, the head data of the content is prefetched. Techniques to do this have been proposed. As this type of technology, for example, there is one described in Patent Document 1 described later.

FIG. 5 schematically shows the system described in Patent Document 1. In the system 12 shown in the figure, when a content group of playback candidates is determined based on a predetermined program organization or a search result of a viewer, the transmission unit 10 starts from the content data in the storage unit 100 at the start data reproduction time 1100. The corresponding amount of head data 1000 is read and transmitted to the receiving unit 20. The receiving unit 20 stores the received head data in the storage unit 200. The viewer selects one desired content from the content group to be played. The receiving unit 20 reads out the top data of the selected content from the storage unit 200 and reproduces it. Transmitter 10 The subsequent data 1002 of the content is transmitted. The receiver 20 reproduces the subsequent data 1002 following the reproduction of the head data.

 Patent Document 1: Japanese Patent Laid-Open No. 2002-344399

 Disclosure of the invention

 Problems to be solved by the invention

 By the way, when providing a distribution service, it is not preferable that a large amount of waiting time is generated on the user side. For example, if it takes more than 7 seconds to display a Web page in the WWW service, the user is said to stop browsing that page.

 [0007] From the above viewpoint, at the initial stage of distribution in the system 1, all of the content groups are within the initialization time from when the content group of the reproduction candidates is designated by the receiving unit 20 until individual content can be selected. It is desirable to finish delivering the first data. In general, the above initialization time is determined at the time of designing the distribution system in consideration of user convenience.

 [0008] The receiving unit 20 presents the options of the content after receiving all the head data so that the head data can be reproduced immediately when the content is selected. Therefore

However, if the distribution of the head data is not completed within the initialization time, an extra waiting time occurs for the user waiting for the selection operation.

 [0009] In particular, as the number of contents in the content group increases, it becomes more difficult to finish distributing the head data within the initialization time. In addition, the transmission band between the transmission unit and the reception unit, the number and type of content groups to be reproduced, the initialization time, the reproduction delay, and the like differ for each distribution system. Therefore, when the transmission band is narrow or the reproduction delay is long, there is a possibility that all the head data cannot be distributed within the initialization time.

 The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for reducing a user's waiting time in a system that distributes moving image content. Means for solving the problem

[0011] A moving image distribution system according to the present invention includes a transmitting device that transmits moving image data constituting content, and a receiving device that reproduces moving image data received from the transmitting device. Each head data in the content group that is a playback candidate of the receiving device Initialization of the means for transmitting data to the receiving device and the quality of all the head data to be transmitted to the receiving device, indicating the period from the specification of the reproduction candidate in the receiving device to the completion of reception of the head data. Means for adjusting to a quality that can be transmitted in time, and means for transmitting the subsequent data requested by the receiving device regarding the content of the reproduction candidate, and the receiving device receives the reproduction candidate upon completion of reception of the head data. And a means for requesting the transmitting device for subsequent data of the content selected from the reproduction candidates and reproducing the head data of the content.

 The invention's effect

 [0012] According to the present invention, since the transmission device adjusts the quality of the top data of the reproduction candidate so that it can be transmitted within the initial time, it is flexible with respect to distribution conditions such as transmission band and content type. Can deal with. As a result, the user of the receiving device can comfortably view the content in various environments.

 Brief Description of Drawings

 FIG. 1 is a block diagram showing a system configuration of an embodiment of the present invention.

 FIG. 2 is a sequence diagram showing a system operation of the embodiment.

 FIG. 3 is a flowchart showing a detailed procedure of a transmission unit in the embodiment.

 FIG. 4 is a block diagram showing a system configuration according to another embodiment of the present invention.

 FIG. 5 is a block diagram showing a conventional system configuration.

 Explanation of symbols

[0014] 11, 12 system

 10 Transmitter

 20 Receiver

 100,200 storage unit

 101 First data reading section

 102 Subsequent data reading section

 110 Lead data quality adjustment section

 201 Playback section

1001 First data 1002 Subsequent data

 1100 First data playback time

 1101 Initialization information

 1102: Leading data quality information

 BEST MODE FOR CARRYING OUT THE INVENTION

 FIG. 1 shows a system configuration of an embodiment of the present invention. The distribution system 11 according to the present embodiment is a system that distributes moving image data content, and includes a transmission unit 10 that distributes content and a reception unit 20 that receives content. The transmission unit 10 is a component corresponding to the moving image distribution device according to the present invention, and specifically, for example, is a server device of a business operator that operates a distribution service. The receiving unit 20 is a client device such as a portable information terminal having a moving image playback function.

 [0016] The transmission unit 10 stores the moving image data of the content, the head data reading unit 101 that reads the head data of the content from the storage unit 100 and transmits the data, and plays back the head data of the content. The subsequent data reading unit 102 that reads and transmits the subsequent data to be transmitted from the storage unit 100, and the first data quality adjustment unit 110 that generates first data quality information 1102 to be described later regarding the quality of the first data.

 The content held in the storage unit 100 is classified by genre, and is classified into a content group including one or more contents. In addition, the moving image data of each content is hierarchically encoded. Hierarchically encoded image data is image data in which a hierarchy is formed in elements such as resolution. For example, when the hierarchy is formed based on the resolution, the lower the hierarchy, the lower the resolution. By selecting a hierarchy for such a hierarchical structure, one or more of image time (frame rate), space (resolution), and image quality (bit rate) can be arbitrarily adjusted.

The reception unit 20 includes a storage unit 200 and a playback unit 201. The playback unit 201 makes the content group content selectable when all the top data transmitted from the transmission unit 10 regarding the content group specified by the user is stored in the storage unit 200. The state in which the content can be selected is, for example, displaying content choices on the screen or outputting the choices by voice. When content is selected by the user, the playback unit 201 Of the top data stored in the memory unit 200, the content is reproduced. At the same time, the playback unit 201 requests the transmitter 10 for subsequent data of the content. Subsequently to the reproduction of the head data, the received subsequent data is reproduced.

 The operation of the distribution system 11 will be described with reference to the sequence shown in FIG. The receiving unit 20 notifies the transmitting unit 10 of information indicating which content group the user has designated (Sl). This content group is a playback candidate of the receiving unit 20, and is specified from, for example, a specific program organization program, a search result in the receiving unit 20, the contents of a web page organized by the user, a list in which a plurality of web pages are aggregated, etc. Is done.

 [0020] When the transmission unit 10 recognizes the reproduction candidate notified from the reception unit 20 (S2), the head data reading unit 101 transmits the head data of each content constituting the content group to the reception unit 20. (S3). The leading data transmitted at this time is read from the storage unit 100 based on the leading data quality information 1102 generated by the leading data quality adjustment unit 110.

 Here, with reference to the flowchart of FIG. 3, the processing of the transmission unit 10 regarding the transmission of the head data (FIG. 2: S3) will be described in detail. The head data quality adjustment unit 110 refers to the head data reproduction time 1100 and the initialization information 1101 and generates head data quality information 1102 for each content in the content group (S01).

 [0022] The head data playback time 1100 is a time required for playback of head data in the receiving unit 20, and is a parameter determined by the transmission environment of the distribution system. In order to make it possible to play back one piece of content without delay, the start data playback time 1100 is the playback delay time from when the receiver 20 requests subsequent data to the transmitter 10 until it can be played back. Set longer.

 [0023] The reproduction delay time is a transmission delay time from when the receiving unit 20 transmits a request for subsequent data to the transmitting unit 10 until it is received, and an amount by which the content can be reproduced without fluctuation after starting to receive the subsequent data. This is determined by one or both of the buffering delay times for accumulating subsequent data.

The transmission delay time can be measured by sending a predetermined signal from the receiving unit 20 to the transmitting unit 10. As an example of the transmission delay time, there is a round trip time calculated by a retransmission timeout procedure of TCP (Transmission Control Protocol). Transmission delay time and It is then, in addition, transfer control protocol such as RTCP (RTP Control Protocol), transmission unit 10, from send information Sender_R indicia ort about the stream to the receiver 20, information Recei _Ve about the reception quality from the reception section 20 The time to receive r_R mark ort can be used.

 [0025] The nofering delay time is determined by the picture reference structure of the moving image data constituting the content and the code amount of each picture.

 On the other hand, the initialization information 1101 includes an initialization time, which is a time from when a reproduction candidate is designated and input by the reception unit 20 until content can be selected, and between the transmission unit 10 and the reception unit 20. It is set based on the transmission band. The initialization time is a parameter that determines the quality of service of the distribution system, and refers to the time from when the receiving unit 20 accesses the distribution service until the content can actually be played back by the receiving unit 20. This initialization time is set in advance in the transmission unit 10 as an allowable value of the waiting time when viewing the user-powered S content.

 The head data quality adjustment unit 110 uses the initialization information 1101 to calculate an allowable transmission amount << that is the maximum amount of data that can be transmitted within the initialization time (FIG. 3: SOU). Also, the head data quality adjustment unit 110 refers to the storage unit 100, recognizes data corresponding to the head data playback time 1100 for each playback candidate content, and obtains the data amount. The data corresponding to the start data reproduction time 1100 corresponds to the start data of the content. The head data quality adjustment unit 110 further calculates the sum of the above data amounts obtained for all contents, that is, the total amount / 3 of the top data of the content group (S01_2), and calculates the total amount / 3 as It is compared with the allowable transmission amount α of the initialization time described above (S01_3).

 [0028] As a result of the comparison, if the total amount 13 of the head data is less than the allowable transmission amount α of the initialization time (S01_3: Yes), the head data quality adjustment unit 110 adjusts each head data to be transmitted. First data quality information 1102 indicating not to be applied is generated (S01_4). When the head data quality information 1102 is applied, the head data is read from the storage unit 100 with the original quality and transmitted to the receiving unit 20. As described above, the data in the storage unit 100 is hierarchically encoded. Therefore, when the default value of quality is, for example, the highest level in the hierarchical structure, the top data corresponding to the highest quality is read from the storage unit 100.

[0029] Further, when the total amount 13 of the head data exceeds the allowable transmission amount α of the initialization time (S01_3: No), the head data quality adjustment unit 110 generates head data quality information 1102 indicating that the quality of each head data is reduced (S01_5). This head data quality information 1102 is information for reducing the quality of each head data so that the total amount of head data / 3 falls within the allowable transmission amount α of the initialization time. In order to reduce the quality of the top data, a layer lower than the default layer may be applied to one or more of the frame rate, spatial resolution, and bit rate of the top data. Therefore, the head data quality information 1102 in this case is layer index information indicating which layer is applied to the head data to be transmitted.

 The head data reading unit 101 reads head data from the storage unit 100 in accordance with the head data quality information 1102 for each content i in the content group that is a reproduction candidate, and transmits it to the receiving unit 20 (S02). The head data reading unit 101 executes the head data reading process for all contents in the content group (S03).

 Returning to the sequence of FIG. 2, the subsequent processing in the distribution system 11 will be described.

 The transmitting unit 10 terminates the distribution service if there is no access from the receiving unit 20 within a predetermined period after transmitting the top data (S4: Yes).

 [0032] On the other hand, when the receiving unit 20 has received all the head data of the content group transmitted from the transmitting unit 10 (S5), the content of the content group is presented to the user in a selectable manner (S6). . When one content is selected from the presented content group, the receiving unit 20 requests subsequent data of the content from the transmitting unit 10 (S7). At the same time, the receiving unit 20 starts reproduction of the top data of the selected content (S8).

 [0033] When transmitting unit 10 detects a request from receiving unit 20 regarding subsequent data (S9: Yes), subsequent data reading unit 102 transmits subsequent data of the content to receiving unit 20 (S10). The subsequent data transmitted at this time is the subsequent data 1002 read from the storage unit 100 based on the head data reproduction time 1100, and the quality is the original quality.

[0034] The receiving unit 20 buffers the subsequent data from the transmitting unit 10 and sequentially reproduces the subsequent data following the reproduction of the head data (Sll, S12). Each time a new content is specified from the content group, the transmission unit 10 and the reception unit 20 perform the above processing. [0035] As described above, in the above embodiment, when the transmission unit 10 transmits the top data of the reproduction candidates, the quality of the top data is adjusted so that they can be transmitted within the initial time. . As a result, it is possible to realize a moving image distribution system that is not easily restricted by the transmission band, content type, and the like. In addition, the user of the receiving device can comfortably view the content in various environments.

 [0036] Note that, regarding the transmission of subsequent data, the transmission is performed with the original quality in the above embodiment, but instead, the subsequent data reading unit 102 refers to the head data quality information 1102 to determine the quality of the head data. The subsequent data may be transmitted while improving the quality step by step.

[0037] Further, regarding content reproduction, the present invention is not limited to application to normal reproduction, but can also be applied to special reproduction such as fast-forwarding or slow reproduction. For example, in fast forward playback, the number of image frames corresponding to the initial data playback time (1100) is greater than that in normal playback. That is, the amount of head data for fast-forward playback increases compared to normal playback. In this case as well, as described in the above embodiment, the quality of the head data is lowered when the head data amount is larger than the allowable transmission amount (α) of the initialization time. As a result, transmission of the head data can be completed within the initialization time.

 [0038] In the above embodiment, content data is hierarchically encoded. However, the present invention can also handle content data that is not hierarchically structured. Figure 4 shows the system configuration in that case. The head data re-encoding unit 103 of the transmission unit 10 has a function of converting the quality of the head data not hierarchized into the required quality.

 In the distribution system 12 shown in the figure, the content data held in the storage unit 100 of the transmission unit 10 is original quality data that is not hierarchically encoded. The head data reading unit 101 reads data having a data amount corresponding to the head data reproduction time 1100 from the storage unit 100. Then, the head data re-encoding unit 103 re-encodes the read data according to the head data quality information 1102 from the head data quality adjusting unit 110. Thereby, the head data to be transmitted to the receiving unit 20 can be obtained.

[0040] In the above embodiment, the content data is stored in the storage unit 100 of the transmission unit 10. However, instead of this, the content data is stored in a device external to the transmission unit 10. It may be. In that case, each time the content is distributed, the transmission unit 10 accesses an external device and acquires necessary data.

 In the above embodiment, the initialization time is set uniformly for all contents targeted for the distribution service. However, the initialization time may be changed according to the specified content group. For example, a value that is different for each importance level of the content group is set in the transmission unit 10 as an allowable value of the waiting time of the user, and this is used as the initialization time. In this case, the head data quality adjustment unit 110 generates the head data quality information 1102 so that the head data can be transmitted within the initialization time, similarly to the operation in the above-described embodiment.

 As the above-mentioned importance, for example, a numerical value such as a search order or a reproduction frequency of the content group or a degree of attention can be considered. The content group with such a high degree of importance is more likely to match the user's preferences, and it is considered that the user wants to view it immediately. Therefore, the correspondence relationship between the importance level and the allowable value of the waiting time is set in advance so that the user waiting time becomes shorter as the content group has a higher importance level. Then, when the content group is actually specified, the allowable waiting time value corresponding to the importance level of the content group may be recognized as the initialization time. This further enhances user convenience.

 The present invention is suitable for a moving image data distribution service on the Internet, for example. By applying the present invention, it is possible to realize immediate playback of Web content without being restricted by the transmission band, the number and type of content groups, initialization time, playback delay, and the like.

 [0044] This application claims priority based on Japanese Patent Application No. 2006-320122 filed on Nov. 28, 2006, the entire disclosure of which is incorporated herein.

Claims

The scope of the claims  [1] a transmission device that transmits moving image data constituting content;  A receiving device for reproducing moving image data received from the transmitting device;  With  The transmitter is  Means for transmitting each head data in the content group as a reproduction candidate of the receiving device to the receiving device;  Means for adjusting the quality of all the head data to be transmitted to the receiving device to a quality that can be transmitted at an initialization time indicating a period until completion of reception of the head data of the reproduction candidate in the receiving device;  Means for transmitting subsequent data requested from the receiving device with respect to the content of the reproduction candidate;  Have  The receiving device is:  Means for presenting the playback candidate so as to be selectable upon completion of reception of the head data, requesting the transmitting device for subsequent data of the content selected from the playback candidate, and playing back the head data of the content  A moving image distribution system comprising:  [2] When the transmission device adjusts the quality of the head data, the allowable transmission amount of the initialization time defined by the transmission band between the own device and the reception device and the total amount of the head data of the reproduction candidate The moving image according to claim 1, wherein if the total amount exceeds an allowable transmission amount, a quality lower than the original quality is applied to each head data to be transmitted to the receiving device. Distribution system.  [3] The moving image distribution system according to claim 1 or 2, wherein the transmission device includes a storage device that holds the hierarchically encoded moving image data as moving image data of content. [4] The transmitting device generates hierarchical index information indicating a hierarchy corresponding to the quality of each head data to be transmitted to the receiving device, and stores the storage based on the hierarchical index information. 4. The moving image distribution system according to claim 3, wherein each head data is read from the device and transmitted.  [5] The transmission device includes a storage device that holds the moving image data of the content with an original quality, reads out data of a data amount corresponding to the reproduction time of the head data in the reception device from the storage device, 3. The moving image distribution system according to claim 1, wherein the read data is converted into data having a quality lower than the original quality, and the data is transmitted as head data to the receiving device.  6. The moving image distribution system according to any one of claims 1 to 5, wherein the transmission device adjusts the quality of the top data stepwise.  7. The moving image distribution system according to any one of claims 1 to 6, wherein the transmission device changes an initialization time according to the importance of a content group as a reproduction candidate.  [8] A moving image distribution device connected to a receiving device that reproduces moving image data constituting content,  Means for transmitting each head data in the content group as a reproduction candidate of the receiving device to the receiving device;  Means for adjusting the quality of all the head data to be transmitted to the receiving device to a quality that can be transmitted at an initialization time indicating a period until completion of reception of the head data of the reproduction candidate in the receiving device;  Means for transmitting subsequent data requested from the receiving device with respect to the content of the reproduction candidate;  A moving image distribution apparatus comprising: [9] When adjusting the quality of the top data, the allowable transmission amount of the initialization time defined by the transmission band between the own device and the receiving device is compared with the total amount of the top data of the reproduction candidates. 9. The moving image distribution apparatus according to claim 8, wherein when the total amount exceeds an allowable transmission amount, a lower quality than the original quality is applied to each head data to be transmitted to the receiving device. 10. The moving image distribution device according to claim 8, further comprising a storage device that holds the hierarchically encoded moving image data as moving image data of the content. [11] Hierarchical index information indicating a hierarchy corresponding to the quality of each head data to be transmitted to the receiving device is generated, and each head data is read from the storage device and transmitted based on the layer index information. The moving image distribution apparatus according to claim 10, wherein: [12] A storage device that holds the moving image data of the content with original quality is provided, and the amount of data corresponding to the reproduction time of the head data in the reception device is read from the storage device, and the read data 10. The moving image distribution apparatus according to claim 8 or 9, wherein the data is converted into data of lower quality than the original quality and the data is transmitted to the receiving apparatus as head data. [13] The moving image distribution apparatus according to any one of [8] to [12], wherein the quality of the top data is adjusted so as to be increased stepwise. 14. The moving image distribution apparatus according to any one of claims 8 to 13, wherein the initialization time is changed in accordance with the importance of the content group of reproduction candidates. [15] A program that causes a computer to function as the moving image distribution device according to any one of claims 8 to 14. [16] In a system including a transmitting device that transmits moving image data constituting content and a receiving device that reproduces moving image data received from the transmitting device,  The transmitting device transmitting to the receiving device each head data in a content group that is a reproduction candidate of the receiving device;  The transmitter adjusts the quality of all the head data to be transmitted to the receiver to a quality that can be transmitted in the initialization time that indicates the period from the specification of the reproduction candidate in the receiver to the completion of reception of the head data. And steps to  The receiving device presents the reproduction candidate to be selectable when reception of the head data is completed. Requesting subsequent data of the content selected from the reproduction candidates to the transmitting device and reproducing the top data of the content;  The transmitting device transmitting subsequent data requested from the receiving device regarding the content of the reproduction candidate;  A moving image distribution method comprising: [17] When the transmitting device adjusts the quality of the head data, the transmitting device and the receiving device The allowable transmission amount of the initialization time specified by the transmission band between the data and the total amount of the head data of the reproduction candidate is compared, and if the total amount exceeds the allowable transmission amount, it is transmitted to the receiving device. 17. The moving image distribution method according to claim 16, wherein a lower quality than the original quality is applied to each head data. 18. The moving image distribution method according to claim 16 or 17, wherein the transmission device holds the hierarchically encoded moving image data as content moving image data in a storage device. [19] The transmitting device generates hierarchical index information indicating a hierarchy corresponding to the quality of each leading data to be transmitted to the receiving device, and reads each leading data from the storage device based on the hierarchical index information. 19. The moving image distribution method according to claim 18, wherein the transmission is performed.  [20] The transmitting device holds the moving image data of the content in the storage device with the original quality, and reads out the data of the data amount corresponding to the reproduction time of the head data in the receiving device from the storage device 18. The moving image distribution method according to claim 16, wherein the data is converted into data having a quality lower than the original quality, and the data is transmitted as head data to the receiving device.  21. The moving image distribution method according to any one of claims 16 to 20, wherein the transmission device adjusts the quality of the top data stepwise.  [22] The moving image data having a data amount corresponding to a reproduction delay time indicating a period from when the transmission device requests subsequent data of the content at the reception device to reception and reproduction of the subsequent data. The moving image distribution method according to any one of claims 16 to 21, wherein the moving image distribution method is recognized as data.  [23] A transmission delay time indicating a period from when the transmission device requests subsequent data of the content at the reception device to reception of the subsequent data, and reception of the subsequent data at the reception device starts. 23. The moving image distribution method according to claim 22, wherein the reproduction delay time is recognized as one or both of a buffering delay time indicating a period from when the image is accumulated to when it is accumulated. [24] The transmission device may use a retransmission timeout protocol by TCP (Transmission Control Protocol). 24. The moving image distribution method according to claim 23, wherein a round trip time calculated in the following is recognized as the transmission delay time. [25] The transmission device recognizes, as the transmission delay time, a period from transmission of information on a transmission stream to the reception device by RTCP (RTP Control Protocol) until reception of information on reception quality from the reception device. 24. The moving image distribution method according to claim 23.  26. The moving image distribution method according to claim 23, wherein the transmission device determines the buffering delay time based on a picture reference structure of subsequent data.  27. The moving image distribution method according to any one of claims 16 to 26, wherein the transmission device changes an initialization time in accordance with the importance of a content group as a reproduction candidate.  [28] A moving image distribution device connected to a receiving device that reproduces moving image data constituting the content,  Transmitting each head data in the content group as a reproduction candidate of the receiving device to the receiving device;  Adjusting the quality of all the head data to be transmitted to the receiving device to a quality that can be transmitted in the initialization time indicating the period until the completion of the reception of the head data of the reproduction candidate in the receiving device;  Transmitting subsequent data requested from the receiving device regarding the content of the reproduction candidate.