Abstract:
A method for network operators to control traffic between a server and a client so that client-induced traffic preemption may be prevented is provided. The method includes the processes of an operator determining a network status, the network in which a server is streaming content via a multi-media transmission system, in accordance with a status of the network, determining whether to modify meta data by considering a set of predetermined conditions, and transmitting to a terminal data reflecting the modification decision.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a U.S. National Stage application under 35 U.S.C. §371 of an International application filed on Dec. 5, 2012 and assigned application number PCT/KR2012/010482, which claimed the benefit of a Korean patent application filed on Dec. 6, 2011 in the Korean Intellectual Property Office and assigned Serial number 10-2011-0129916, the entire disclosure of which is hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a method and an apparatus for controlling traffic using adaptive streaming in a multimedia content transmission system. 
     BACKGROUND 
     In recent years, with an increase in the use of online content, smooth content transmission has become important. Accordingly, there is active discussion of adaptive streaming technology in which a bit rate of content is adaptively changed according to a usable transmission bandwidth or a change in an apparatus performance of a user. 
     There is a dynamic adaptive streaming over hypertext transfer protocol (HTTP) (DASH) which corresponds to a representative technology of adaptive streaming. The DASH is a technology related to a method of configuring content and a method of transmitting the configured content. Hereinafter, a broadcasting communication system using the DASH technology will be described with reference to  FIG. 1 . 
       FIG. 1  is a block diagram illustrating a broadcasting communication system using the DASH technology according to the related art. 
     Referring to  FIG. 1 , the broadcasting communication system includes a server  100  and a client  120 . The server  100  and the client  120  communicate with each other through a communication network  130 . For example, the server  100  may provide a DASH content  110  to a user, and the DASH content  110  is configured as follows. 
     The DASH content  110  includes a media segment belonging to a representation  110   a  and an adaptation set  110   b , and metadata  110   c . The representation  110   a  indicates a row of media segments having different image qualities, different resolutions, different bit rates, etc., and the adaptive set  110   b  is obtained by grouping a plurality of representations. Here, the number of the representations  110   a  and the number of the adaptive sets  110   b  may be larger than one. The metadata  110   c  includes information on a relation between the representation  110   a  and the adaptive set  110   b.    
     The client  120  receives metadata  110   c  and determines which adaptive set should be reproduced. Further, the client  120  selects one of the plurality of representations in the determined adaptive set, based on the network situation and the capability of a reproduction device in the client  120 . Next, the client  120  downloads the selected representations from the server  110  and reproduces the downloaded representations. 
       FIG. 2  illustrates an example where the DASH content is provided, in a broadcasting communication system according to the related art. 
     The DASH technology uses a client control streaming scheme in which streaming is controlled by the client, instead of a server control streaming scheme in which streaming is controlled by a server. 
     When the server control streaming scheme is used, a server  200  transmits optimal content according to each network situation for each client based on information on the client  210  connected thereto. However, as illustrated in  FIG. 2 , the server  200  is overloaded as the number of the clients increases. 
     Meanwhile, when the client control streaming scheme based on the DASH technology is used, the server  200  may generate a plurality of media segments and a plurality of pieces of metadata which can be used according to each network situation. Then, the client directly selects and reproduces content according to a current network situation, so as to download and reproduce optimal content according to the network situation without a load of the server  200 . 
     However, since all of the clients use maximal amount of traffic according to their own network situations, there is a problem in that an amount of network traffic increases even when there are a small number of clients. Further, implementation of a DASH client logic of the client is in a region of the reproduction device, and there is no control method which a communication network can use in order to decrease the amount of the network traffic. 
     Further, the server  200  merely provides the content, and has a difficulty to configure content for a specific communication network (as an example, a communication network having a large amount of traffic). The reason is that a plurality of different communication networks may exist between the clients, so that it is unreasonable that the content is configured only for a specific communication network. Further, there is a problem in that reconfiguring of the content according to a network situation does not comport with the original purpose of the DASH technology. 
     The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure. 
     SUMMARY 
     Aspects of the present disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide a method and an apparatus for controlling traffic using adaptive streaming in a multimedia content transmission system. 
     Another aspect of the present disclosure is to provide a method and an apparatus for preventing traffic reduction generated due to an excessive connection increase of clients in a multimedia content transmission system using Dynamic Adaptive Streaming over Hypertext Transfer Protocol (HTTP) (DASH) technology. 
     Another aspect of the present disclosure is to provide a method and an apparatus for controlling traffic between a content provider server and a client, by a communication network device, in a multimedia content transmission system using DASH technology. 
     In accordance with an aspect of the present disclosure, a method for controlling traffic by a communication network device in a multimedia content transmission system is provided. The method includes receiving, from a content providing server, metadata including information on representations having different qualities included in a same content, when an amount of the traffic in a network managed by the communication network device exceeds a threshold value, modulating the metadata to exclude information on at least one of the representations from the metadata, and transmitting the modulated metadata to clients located in the network. 
     In accordance with another aspect of the present disclosure, a method for controlling traffic by a client in a multimedia content transmission system is provided. The method includes receiving metadata including information on representations provided from a content providing server, included in a same content, and having different qualities, receiving information on a maximal bandwidth used for receiving the content from a communication network device, selecting at least one representation having a bandwidth equal to or smaller than the maximal bandwidth among the representations corresponding to the information included in the metadata, and transmitting a message for a request to provide the at least one selected representation, to the content providing server through the communication network device. 
     In accordance with another aspect of the present disclosure, a method of controlling traffic of a communication network device in a multimedia content transmission system is provided. The method includes determining whether an amount of the traffic in a network managed by the communication network device exceeds a threshold value, when the amount of the traffic exceeds the threshold value, transmitting information on a maximal bandwidth used for receiving content, to clients located in the network, transmitting, to the clients, content according to the maximal bandwidth provided from a content providing server according to a request of the clients. 
     In accordance with another aspect of the present disclosure, a communication network device in a multimedia content transmission system is provided. The communication network device includes a reception unit configured to receive, from a content providing server, metadata including information on representations included in the same content and different qualities, a controller configured to modulate the metadata to exclude information on at least one of the representations from the metadata when an amount of traffic in a network managed by the communication network device exceeds a threshold value, and a transmission unit configured to transmit the modulated metadata to clients located in the network. 
     In accordance with another aspect of the present disclosure, a client in a multimedia content transmission system is provided. The client includes a reception unit configured to receive metadata including information on representations provided from a content providing server, included in a same content, and having different qualities, and receives information on a maximal bandwidth used for receiving content from a communication network device, a controller configured to select at least one representation having a bandwidth equal to and smaller than the maximal bandwidth, among the representations corresponding to the information included in the metadata, and a transmission unit that configured to transmit a message for a request to provide the at least one selected representation, to the content providing server, through the communication network device. 
     In accordance with another aspect of the present disclosure, a communication network device in a multimedia content transmission system is provided. The communication network device includes a controller configured to determine whether an amount of traffic in a network managed by the communication network device exceeds a threshold value, and a transmission unit configured to transmit information on a maximal bandwidth used for receiving content when the amount of the traffic exceeds the threshold value, and to transmit the content according to the maximal bandwidth provided from a content providing server, to the clients, according to requests of the clients. 
     The present disclosure can mitigate traffic reduction generated due to an excessive connection increase of clients in a multimedia content transmission system using DASH technology. 
     Further, the present disclosure can mitigate traffic preoccupancy by a client in a multimedia content transmission system using DASH technology. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram illustrating a broadcasting communication system using the Dynamic Adaptive Streaming over Hypertext Transfer Protocol (HTTP) (DASH) technology according to the related art; 
         FIG. 2  illustrates an example where DASH content is provided, in a broadcasting communication system according to the related art; 
         FIG. 3  is a block diagram illustrating a multimedia content transmission system according to an embodiment of the present disclosure; 
         FIG. 4  illustrates nodes included in a communication network between a server and a client, in a multimedia content transmissions system, according to an embodiment of the present disclosure; 
         FIG. 5  is a flowchart illustrating a method of modulating metadata according to an embodiment of the present disclosure; 
         FIG. 6  illustrates a network configuration which can perform traffic control by a client according to an embodiment of the present disclosure; and 
         FIG. 7  is a signal flow diagram illustrating a traffic control process for an adaptive streaming service according to an embodiment of the present disclosure. 
     
    
    
     Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. 
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     The present disclosure proposes a method of adjusting traffic between a server and a client by a network provider in order to mitigate traffic preoccupancy by the client. 
       FIG. 3  is a block diagram illustrating a multimedia content transmission system according to an embodiment of the present disclosure. 
     Referring to  FIG. 3 , a multimedia content transmission system includes a server  300 , a plurality of clients  330  which receives dynamic adaptive streaming over hypertext transfer protocol (HTTP) (DASH) content from the server  300  through a first communication network  310 , and a plurality of clients  340  which receives DASH content from the server  300  through a second communication network  320 . 
     When an amount of traffic of each of the corresponding networks exceeds a predetermined value, the first communication network  310  and the second communication network  320  modulate metadata provided from the server  300  to provide, to the plurality of clients  340 , information on a part of an entire adaptation set and a representation which the client can select. For example,  FIG. 3  illustrates metadata modulated such that the second communication network  320  includes information on a part of adaptation sets and the representation  350 . 
     Meanwhile, the metadata can be modulated as long as the server  300  does not require separate integrity, and the modulated metadata may be configured in various forms in which compatibility for a DASH standard is secured. 
     Each of the plurality of clients  340  detects information on the adaptive set and the representation from the metadata received from the second communication network  320 , and reproduces a media segment corresponding to the detected information. That is, each of the plurality of clients  340  reproduces the media segment based on less than the entire adaptive set and the entire representation, which are provided from the server  300 . Thus, a bandwidth, which each client can use, is adjusted, so that traffic control can be performed. 
     Next, each of the nodes included in a communication network according to an embodiment of the present disclosure will be described with reference to  FIG. 4 . 
       FIG. 4  illustrates nodes included in a communication network between a server and a client, in a multimedia content transmissions system, according to an embodiment of the present disclosure. 
     Referring to  FIG. 4 , a content delivery network (CDN)  420 , a cache server  430 , and an end node  440  may be included between a server  410  providing content and a plurality of clients  450  reproducing the content. 
     The CDN  420  is used such that the server  410  smoothly provides the content. The CDN  420  rapidly provides data according to the content requirement by storing a plurality of pieces of the content received from the server  410  in a plurality of data servers. 
     The cache server  430  is used for a processing requirement repeated several times for the same content. For example, when different clients require the same content, the cache server  430  can provide, to the client, data according to the corresponding content, without transmitting a content request to the CDN  420  or the server  410 . 
     The end node  440  can be directly connected to the client  450 , and can monitor a traffic situation of each client and an entire traffic situation. Further, the end node  440  can perform traffic control by transmitting the monitoring result for the traffic situation to the cache server  430 . That is, the end node  440  transmits information on whether the amount of the traffic exceeds a threshold value (or, information on the amount of the traffic), to the cache server  430 . 
     Then, the cache server  430  determines whether the amount of the traffic exceeds the threshold value based on the information received from the end node  440 . When the amount of the traffic exceeds the threshold value, the cache server  430  modulates metadata stored therein, or metadata of the server  410  received from the CDN  420 , to transmit information on the entire adaptive set and a part of the representation, to the client  450 . When the amount of the traffic does not exceed the threshold value, the cache server  430  modulates metadata stored therein, or metadata of the server  410  received from the CDN  420 , to transmit information on the entire adaptive set and the representation, to the client  450 . 
     Next, a process of modulating metadata by the cache server  430  will be described as an example in consideration of a case where a plurality of nodes exist in a communication network as illustrated in  FIG. 4 . 
       FIG. 5  is a flowchart illustrating a method of modulating metadata according to an embodiment of the present disclosure. 
     Referring to  FIG. 5 , in operation  501 , the cache server  430  receives, from the end node  440 , a traffic monitoring result of the network. Here, the traffic monitoring result may include information on an amount of traffic in the corresponding network, information on whether the amount of the traffic exceeds a threshold value, etc. 
     The cache server  430  may determine the threshold value (which may be used as a criterion for estimating an optimal amount of the traffic in the network) for the amount of the traffic for each end node. Accordingly, in operation  503 , the cache server  430  determines whether the amount of the traffic exceeds the threshold value based on the received traffic monitoring result. When it is determined in operation  505  that the amount of the traffic exceeds the threshold value, the cache server  430  proceeds to operation  513  to determine whether DASH content is transmitted to the client  450  or not. 
     When the DASH content is being transmitted, in operation  515 , the cache server  430  disables the representations of the adaptive set in order, starting from the representation having the largest influence on an increase in the amount of the traffic. Here, disabling of the representation implies an operation of excluding information on the corresponding representation from the metadata. Further, the cache server  430  can identify the representation having the largest influence on the increase in the amount of the traffic among the representations included in the corresponding adaptive set, based on the size of the bandwidth, etc. Thereafter, the cache server  430  returns to operation  503 . 
     Meanwhile, when the DASH content is not transmitted in operation  513 , the cache server  430  proceeds to operation  517  to perform other processes. 
     When it is determined in operation  507  that the amount of the traffic is smaller than the threshold value, in operation  509 , the cache server  430  determines whether there is the modulated metadata. Further, when there is the modulated metadata, the cache server  430  proceeds to operation  511  to enable the disabled representations in order from the representation having the smallest influence on the increase in the amount of the traffic. Here, enabling of the representations implies an operation of including the information on the corresponding representation in the metadata. Further, the cache server  430  can identify the representation having the smallest influence on the increase in the amount of the traffic, among the representations included in the corresponding adaptive set, based on the size of the bandwidth, etc. 
     Meanwhile, when there is no modulated metadata, the cache server  430  returns to operation  503 . 
     As a result, when the amount of the traffic exceeds the threshold value, the cache server  430  may disable the representations in order from the representation having the large influence on the increase in the amount of the traffic until the amount of the traffic becomes equal to the threshold value. Further, when the amount of the traffic is smaller than the threshold value, the cache server  430  may enable the disabled representations in order starting from the representation having the smallest influence on the increase in the amount of the traffic until the amount of the traffic becomes equal to the threshold value. 
     Next, a scheme of modulating metadata for traffic control according to an embodiment of the present disclosure will be described. The scheme of modulating the metadata for the traffic control may include a scheme of modulating the metadata while maintaining context of the DASH content, and a scheme of modulating the metadata while not maintaining the context of the DASH content. 
     First of the two schemes, the scheme of modulating the metadata while maintaining the context of the DASH content will be described. 
     The metadata may include information on a period, an adaptive set, a representation, etc. 
     Elements of the content provided in the same time period are included for each adaptive set under the period information. 
     A row of the media segments having different qualities, for one element of the content provided to the same context, is included as the representation under the adaptive set. 
     Thus, the representations included in one adaptive set have different qualities while maintaining the context of the DASH content. Thus, the representations may be disabled and enabled for modulating the metadata for maintaining the context of the DASH content. 
     The representations include a property such as a bandwidth which is mandatory, and properties such as quality ranking (for example, indicating high quality as the quality ranking value is small), a width, a height, a frame-rate, a scan-type, etc. which are optional. 
     The bandwidth property among the aforementioned properties may be used for identifying the representation having the largest influence on the increase in the amount of the traffic. That is, the representations having the large influence on the increase in the amount of the traffic can be identified in order, starting from the representation having the large bandwidth. When there are the representations having the same bandwidth, the representations having the large influence on the increase in the amount of the traffic can be identified in order by using at least one of the optional properties. 
     Meanwhile, in order to disable the representations, names of the elements of the metadata configured by an extensible markup language (XML) may be changed or annotated. 
     For example, the names of the elements of the metadata may be changed as follows in order to disable &lt;/Representation&gt; which is an end tag of the &lt;Representation&gt; in the metadata. That is, the term “&lt;/Representation&gt;” which is not used in the DASH technology may be changed as described in Table 1. 
     
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Disabling method 
                 Changing content (Example) 
               
               
                   
               
             
             
               
                 Annotation 
                 &lt;!−resentation&gt; . . . &lt;/resentation---&gt;) 
               
               
                 (Use annotation signs “!-”  
                   
               
               
                 and “---”) 
                   
               
               
                 Substitution 
                 &lt;_epresentattion&gt; . . . &lt;/_epresentation&gt; 
               
               
                 (Change some characters of  
                 → However, the changed names should 
               
               
                 the Representation into other  
                 correspond to name not used in the 
               
               
                 Alphabets or Signs) 
                 DASH technology 
               
               
                   
               
             
          
         
       
     
     Meanwhile, a method of restoring the names of the annotated or substituted elements to their original names may be used for the enabling operation. 
     Next, a scheme of modulating the metadata while not maintaining the context of the DASH content will be described. 
     The adaptive set of the elements of the DASH content provides one media component (e.g., audio or video) and a role descriptor. The role descriptor may have a value of a main (used when other information is not provided) or a value of an alternative (having the same media component type as that of the main and used as a substitution for the main), and may instruct a role for whether specific audio and specific video are used as the main or the alternative. 
     Thus, when the values of the main and the alternative are provided through the role descriptor, all of the representations having the values of the main and the alternative should be disabled. 
     The reason is that the client reproduces one of the representations having the values of the main and the alternative, so that when the representations are disabled without distinction of the values of the main and the alternative, a traffic control effect according to the metadata modulation cannot be obtained. Further, the reason is that other contexts are provided to the client so that a result which both the communication network and the client do not want may occur. 
     When the metadata is modulated by identifying all of the values of the role descriptor of the same media component, one of the video and the audio may not be reproduced. Such a situation may occur when a network speed is lowered, due to characteristics of the DASH technology, so that the client may perform the modulated operation without a special functional problem. 
     Meanwhile, when different DASH contents are provided, the network provider may determine which DASH content is modulated. 
     In a situation where traffic control is needed, although the end node may modulate all of the DASH contents, the traffic is not immediately lowered even when the DASH contents are modulated. 
     Thus, it is proper to select the DASH contents to be modulated, in an order starting from the DASH content having a short minimumUpdatePeriod, by identifying minimumUpdatePeriod information in the metadata. 
     The reason is that, when the minimumUpdatePeriod is short, the time during which the client updates the metadata is shortened, so that a probability to influence a client operation through the modulation of the metadata increases by an amount corresponding to the shortened time. 
     When there is no minimumUpdatePeriod information in the metadata, the client may not update the previously downloaded metadata until the reproduction is completed. In this case, even when the metadata is changed in the communication network, an operation of the client is not influenced. 
     Hereinabove, the method of performing the traffic control through the metadata modulation in the communication network has been described. Hereinafter, a method of performing traffic control by the client will be described. 
       FIG. 6  illustrates a network configuration that can perform traffic control by a client according to an embodiment of the present disclosure. 
     Referring to  FIG. 6 , a client  600  includes a network operation device  610  for performing device management for the client, a CDN  620  for transmitting a metadata/media segment, a streaming server  630  for providing content, and a metadata server  640  for providing metadata  650 . 
     The client  600  receives complete metadata (metadata including the entire adaptive set and the representation)  650  for the corresponding content service. Further, the network operation device  610  determines a traffic situation in the network, and when traffic control is required, transmits a message for the traffic control, to the client  650 . The message for the traffic control corresponds to a message for instruction to use a part of the representation in the entire adaptive set included in the metadata. 
     Hereinafter, a method of controlling traffic in a network configured in this way will be described in detail with reference to  FIG. 7 . 
       FIG. 7  is a signal flow diagram illustrating a traffic control process for an adaptive streaming service according to an embodiment of the present disclosure. 
     Referring to  FIG. 7 , a client  600  selects content to be reproduced, through a server such as a portal of a provider, and in operation  701 , requests a metadata server  640  to transmit media presentation description (MPD) information as metadata. Further, in operation  703 , the client  600  receives the MPD from the metadata server  640 . Here, the MPD is not changed, and includes an entire adaptive set and a representation. 
     The client  600  selects media segment of the representation to be received, based on the received MPD, and in operation  705 , requests a streaming server  630  to provide the selected media segment. Next, the client  600  receives the requested media segment from the streaming server  630  in operation  707 , and in operation  709  reproduces the corresponding content. Operations  701  to  709  are the same as that of a general adaptive streaming scheme. 
     Meanwhile, when traffic is overloaded in the network while the client  600  receives the content, a DM server  650  corresponding to a network operation device  610  determines whether traffic control is needed, in operation  711 . 
     When it is determined that the traffic control is needed, the DM server  650  transmits a message including information on a maximal bandwidth to the client  600  in order to perform the traffic control, in operation  713 . At this time, the DM server  650  transmits the message to all of the clients in the network. 
     Then, the client  600  receives the message to detect the information on the maximal bandwidth, and processes the metadata, in operation  715 . That is, the client  600  identifies the representation having a bandwidth smaller than the maximal bandwidth based on the metadata, and then in operation  717 , the client  600  receives and reproduces a media segment for the identified representation. 
     While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.