KR20050115498A - P2p based video service system and method for providing vod service using the same - Google Patents

Abstract

The present invention provides a server for indexing and storing video data in units of blocks divided into predetermined sizes, and managing information related to a user group including a user terminal currently connected to a video service; And a plurality of user terminals connected via a server and the Internet and currently receiving video services, wherein the user group includes one or more master user terminals, wherein the master user terminal is added / deleted to a group of other user terminals. Group information is updated and updated user group information is provided to the master user terminal of another group and the user terminal and server belonging to the group. When the server receives a video data transmission request from the user terminal, the user terminal requests Determining a subject of transmission of the video data of the block, wherein the user group includes a first group for receiving video data from the server, and a second group for receiving the buffered video data to a user terminal in the first group, each group The user terminal of receives a portion of the video data stream from the parent group By handover to the video data stream received from the user terminal and parent groups in the same group being provided for the entire video stream, and reproduces the video data on a block basis with the same index.

Description

P2P based video service system and method for providing video service using same {P2P based video service system and method for providing VOD service using the same}

The present invention relates to video on demand (VoD), and more particularly, to an on-demand video service system and method thereof based on a peer-to-peer (P2P) data transmission scheme.

On-demand video services are typically provided on a unicast-based server-client, which is accomplished by the server establishing a session when a user requests a video service and sending the video data to the requesting client. For example, when transmitting video data at a streaming rate of 400kb / s from a server having a bandwidth of 100Mb / s, the server may provide a service to up to 250 users.

Since the server-client type video service system needs to use high bandwidth for smooth service provision, the number of accessible users is limited according to the current server resources. For this reason, if the demand for on-demand video service increases, the service provider must expand the server or expand the transmission bandwidth.

However, such expansion of servers or expansion of transmission bandwidth may be inefficient and inefficient in light of the current situation in which demand for on-demand video services is increasing. This is because requests for video services are not always constant. That is, even if the system resources are sufficiently prepared in response to the expected demand, if the demand for the on-demand video service is small, the system resources are inefficiently used, and if the demand demand increases, the system may be down.

In order to overcome this problem, a first technique using a network resource instead of a server resource and a second technique using a resource of a user terminal have been proposed.

The first technology is a technology in which an intermediate router replicates stream data sent by a server using IP multicast and delivers the data to a plurality of user terminals. This first technology is very efficient because the bandwidth of the server can be kept constant no matter how many users request the video service. However, current technical support for IP multicast is not provided properly on the Internet. In addition, it is not easy for a server to monopolize an IP multicast address for streaming video data, and there is no technology to limit the packets that can be sent to an IP multicast address. Charging technology is not being presented. As the current IP multicast technology has many challenges to be solved, it is inappropriate to apply the IP multicast technology to commercial on-demand video services provided in the Internet.

The second technology introduces the concept of P2P, and instead of transmitting the video stream data directly to the user terminal, the server transmits the same video stream data to the user terminal that requested the video service. do. That is, since the second technology increases the number of user terminals that can transmit video data to other user terminals as the number of user terminals that are playing video data increases, the number of users requesting video service increases. You can keep or reduce your bandwidth usage.

However, the second technologies proposed so far have a problem that if a user stops playing a video, it has a fatal effect on the video playback at the user terminal receiving video data from the specific user terminal and the user terminal must use a high upload bandwidth. I have a problem.

Accordingly, the present invention is to solve the above problems of the prior art, the on-demand video service that can use a minimum transmission bandwidth of the server and the user terminal while providing a stable on-demand video service to a plurality of user terminals using P2P technology It is an object of the present invention to provide a system and a method thereof.

A system according to the present invention for achieving the above object, the video file is indexed and stored in each block of the video data divided into a predetermined size, the user including at least one user terminal connected to the current video service A server managing information related to the group; And a plurality of user terminals connected to the server via the Internet and currently receiving video services, wherein the user group includes at least one master user terminal, and the master user terminal is connected to a group of other user terminals. Responsible for addition / deletion, updating the user group information, and providing the updated user group information to a master user terminal of another group and a user terminal and a server belonging to a group of the other, wherein the server is an arbitrary user terminal. When the video data transmission request of a specific block is received from the mobile station, a transmission entity capable of providing the video data of the requested block by the user terminal is determined, and the user group receives the video data of the block unit directly from the server. A block stage buffered in a first group and a user terminal in the first group And of a second group to receive the video data transmission, the user terminal in each group it is characterized in that for reproducing the video data on a block basis with the same index.

In addition, the video service method according to the present invention for achieving the above object, the video file is indexed and stored in each of the video data of the block unit divided into a predetermined size, and at least one user terminal currently connected to the video service A server for managing information related to a user group including a server, and a user terminal connected to the server through the Internet belong to one user group, and each user group is a master terminal that is in charge of adding / deleting a group of other user terminals. In the video service method in the existing system, when the server receives a video data transmission request of a specific block from an arbitrary user terminal, the server checks the index of the video data block requested by the user terminal, and the current video service. New user group that is receiving A first step of search for the existence of the group of users that can be included in the user terminal; A second step of providing master terminal information of the user group found in the first step to the user terminal requesting the new service; If the user group to include the user terminal requesting the new service is not found in the first step, the video data block requested by the user to the user terminal requesting the new service without having a child group among the already created groups Searching for whether there is a group capable of providing a third step; If the user group for the conditions in the third step of the search, to create a new group to the user terminal a request for the new service to the master terminal, is more than the new and notifies the generated group information to the retrieved user groups A fourth step of making the created group a child group of the searched user group; A fifth step of checking whether the current free bandwidth is a bandwidth capable of transmitting the requested video data block if there is no user group capable of delivering the requested video data block to the newly requested user terminal in the third step; ; A sixth step of transmitting the requested video data block directly to the user terminal that has requested the new service if there is available bandwidth that can be transmitted in the fifth step; And a seventh step of notifying that the service cannot be provided if there is no free bandwidth in the fifth step.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a P2P based video service system according to the present invention. As shown in FIG. 1, the system of the present invention includes a server 10 for providing a video file at the request of a user terminal.

The server 10 processes and manages a video file to be provided as a service, as shown in FIG. 2, for transmission of a P2P based video file. 2 is a format diagram of a video file managed by a server according to an embodiment of the present invention. As shown in FIG. 2, server 10 provides a video file as a continuous data stream. In this case, it is assumed that the total length of the video file is L seconds, and the video data is transmitted at a constant bit rate (CBR) of R bits / second. In order to transmit such a video file to a user terminal through the Internet, the video file is divided into a data block of D bits and transmitted. Therefore, the server must divide the entire video file into total (R * L) / D data blocks and transmit it every D / R seconds. Accordingly, the server 10 divides the video file into D bits contained in one packet to make n video data blocks B0-Bn-1, and from 0 to n- in each video data block B0-Bn-1. Manage by indexing up to 1. Processing the video file as described above may determine other user terminals that provide the video requested by the user terminal by knowing the information of the video requested by the user, that is, the video playback point, and accordingly, P2P-based video data transmission may be performed. Because you can. When the server 10 receives a video service request from the user terminals 120a to 120h, the server 10 determines a target for providing a video data stream to the user terminals 120a to 120h. Play-point) or one of the user groups.

Meanwhile, the system of the present invention includes a plurality of user terminals 120a to 120h together with the server 10. The server, the user terminal, and the user terminals are connected through the Internet (or IP network). The user terminals 120a to 120h are apparatuses for storing and playing back video data transmitted from the server 10 in a buffer, and the present invention further has a function of providing video data to another user terminal. The user terminal has a buffer that stores the video data block in order to solve the jitter problem when transmitting video over the network and to store the video data block to be provided to another user terminal. The user terminals 120a to 120h store recently received video data blocks within a range allowed by their buffer size, and transmit the stored data blocks to user terminals of child groups which are lower user groups. The size of the buffer is generally smaller than the size of the video.

A video data block stored in a buffer of each user terminal 120a to 120h will be described with reference to FIG. 3. 3 is a format diagram of a video data block stored in a buffer of a user terminal according to an embodiment of the present invention. In the video data block stored in the buffer, the index of the data block with the smallest index is called LD (lowest data block index in a buffer), and the index of the data block with the largest index is called HD (highest data block index in a buffer). The index of the video data block that the server 10 or another group sends to the group to which the user terminal belongs is called RP (Receiving Point), and the index of the video data block that the user group to which the user belongs is sent to the other user group It is called FP (Forwarding Point), and the index of the video data block that the user terminal is playing is called PP (Playing Point). The maximum value of the RP-LD is the size of a user buffer predetermined by the server 10, and the user terminal manages the buffer so that the RP-LD value does not exceed the size of the buffer.

The user terminals 120a to 120h determine a user group according to the video data block stored in the buffer, and determine a target for receiving the video data and a target for transmitting the video data.

Referring to FIG. 1, the user terminals 120a to 120h form a chain 100 connected to the server 10. The user terminals 120a, 120b and 120c form the first user group 110a among the user terminals 120a through 120h, the user terminals 120d and 120e form the second user group 110b, and the user terminals 120f and 120g. 120h forms the third user group 110c. As a result, the chain 100 includes at least one user group, and the user group includes at least one user terminal.

The first user group 110a receives video data from the server 10, the second user group 110b receives video data 130b from the first user group 110a, and receives a third user group ( 110c receives video data 130c from the second user group 110b. At this time, each of the video data 130a, 130b, 130c is composed of different video data blocks.

From a structural standpoint, user terminals form a group-chain structure in which user groups formed by one or more user terminals are connected by a chain.

According to the group-chain structure, the server or user group providing the video stream becomes the parent group, and the user group receiving the video stream becomes the child group.

The user groups 110a, 110b, and 110c are sets of peers, ie, user terminals 120, which play video data blocks having the same playback point, that is, the same index. Therefore, user groups 110a, 110b, and 110c have different playback points, and user terminals of the same user group have the same playback point PP.

In addition, the user terminals of the same user group have the same index RP of the data block transmitted by the parent group, the same index FP of the video data block transmitted to the child group, and the smallest of the stored video data blocks. The index LD of the value is the same.

Meanwhile, user terminals belonging to the same user group 110 are called members, and each user group has a member who plays a role of group master. The group master may add new user terminals or delete user terminals in the group to the user group to which the group master belongs. The group master updates the group information as shown in Table 1 below when the user terminal is added / deleted, and transmits the updated group information to each member so that the updated group information is shared.

Therefore, each member of the user group has group information as shown in Table 1 below.

  Item         meaning  Chain ID  Identifier of the chain to which the group belongs  Generation time  Time when group information is generated  Time to be used  The time at which group information begins to be used  Number of members  The number of user terminals in the group  Member list  List containing each member's IP address, port, and state  RP  RP of group when group information is created  LD  LD of group when group information is generated

The member list is arranged in the order of time when the user enters the user group, ie the member's IP address, port, and state. For example, the first member who enters the user group records their information at '0', the first index of the member list, and the second member records their information at '1', the second index of the member list. do.

The index of each member in the member list is called its member ID. Each member checks its ID by checking the index of the member list after receiving the group information. The member whose ID is '0' among the members becomes the group master.

All members of the group share the group information of the group to which they belong, as shown in Table 1 above, by the group master, and also know the group information of the parent group and the group information of the child group in addition to the group information of the group to which they belong.

Hereinafter, a process in which group information and group information of a parent / child group are known to each member will be described with reference to FIG. 4.

The group master (0) of the user group (110b) updates the group information of the group to which it belongs in accordance with the addition of a new user terminal or the deletion of the existing user terminal, and the group master (group) of the server 10 and the parent group (110a) 0) and the group information of the group to which the updated one belongs to the group master (0) of the child group (110c). In addition, the group master (0) of the user group (110b) provides the group information to the member whose ID is [1, h] among the group members in order to provide the updated group information or the group information of the parent / child group to its group members. Send it. When h = 3, [1, h] is a member whose member ID (ie, index) is 1, 2, or 3. In addition, when the three members having IDs 1, 2, and 3 receive group information, the group information received above is transmitted to the members whose IDs belong to [I · h + 1, I · h + h]. I is an ID of a member for transmitting group information. Therefore, [I · h + 1, I · h + h] corresponding to a member with ID 1 is [3, 6], and [I · h + 1, I · h + h corresponding to a member with ID 2; ] Is [7, 9], and [I · h + 1, I · h + h] corresponding to the member whose ID is 3 is [10, 12].

Group information must also be transmitted reliably. The member who sent the group information should wait for the member who received the group information to send a response that the group information has been received. If the member does not send a response after a predetermined time, the member must retransmit the group information. If such retransmission is repeated more than a predetermined number of times, it is assumed that the member does not exist, and when the ID of the member is J, even the member whose ID is [J · h + 1, J · h + h] is grouped. Information must be sent.

However, when a user terminal newly joins or deletes a user group, a problem may occur when immediately using the group information of Table 1 updated by all members.

That is, if a member immediately uses the updated group information, the member using the updated group information and the member using the group information before the update are simultaneously present in the same user group while the group information is updated. However, members provide a video stream of a P2P transmission method according to group information. If group information used between members of the same user group is different, an error may occur in provision of a video stream.

The reason why the member using the updated group information and the member using the non-updated group information exist at the same time is that the group information transmitted by the group master is transmitted to all members as described with reference to FIG. 4 below. This is because the time taken to be transmitted becomes as shown in Equation 1 below.

T1 is a group information update time, Sg is a size of a group, that is, a number of group members, and d is a maximum value of a packet delay between users, and is predetermined by the server.

Therefore, in order to solve the problem, the group information of Table 1 includes time information at which group information starts to be used. When each member receives the group information, it does not use it immediately, and reads only the updated member list information in the group information, checks its ID and the new ID of another member, and transmits the group information to the other members as described above. In this case, the updated group information is stored in the queue, and the group information is used when the current time is used. Therefore, all members always use the same group information for video streaming. This is because it is advantageous for members to use the same group information when transmitting video data. That is, when the user information is added / deleted to the group and the group information is changed, it is advantageous to use the information of the previous group until all members know this for video data transmission, but to transmit the group information to the group member This is because the new group information must be used. For the same reason, when sending group information of a parent / child group to a group member, the last group information is taken out of the queue containing the group information of the group to which the group belongs, and the parent / child group is referred to by referring to the member list in the group information. Must be sent to other members.

Here, the group master has the number of members of the parent group, the child group, and the user group to which it belongs, and when the group information is updated, the time taken for all members of the parent group, the child group, and the user group to which it belongs to receive the updated group information. Calculate When the group master generates the group information, the group master sets the time for which the group information is used to be later than the time for all the calculated members to receive the group information. This allows the parent group, child group and all members of the same group that have received the updated group information to always use the same group information for video streaming.

Referring to FIG. 5, a process of forming a service structure, that is, a group-chain structure by the server 10 according to an embodiment of the present invention will be described. The description with reference to FIG. 5 will enable those skilled in the art to know which users are grouped into the same user group, when a child group occurs, and when a new chain occurs.

The server receives a request message for requesting a video service from a new user terminal (501). The request message includes a video data block index (RI) of a playback start point requested by the user terminal. The video data block index (RI) is the smallest index among the indexes of the video data block to be received by the user.

When the server receives the video service request message from the user terminal, the server checks the video data block index (RI) included in the received request message (502). The checking of the video data block index (RI) is for checking whether there is a user group capable of providing a video stream to a user terminal requesting service among user groups of the currently configured chains 100, 200, and 300.

The server uses the video data block index (RI) of the playback point to determine the number of video data blocks (α) received by the group while including the user terminal to find the user group to include the user terminal requesting the service. The limit number β of unnecessary video data blocks is determined. The α and β vary depending on the video streaming rate. Since the streaming rate is determined to be a fixed value, the α and β are stored in the server 10 as a default value.

When the server 10 grasps RI, α, and β, it finds a user group that satisfies the following Equation 2 for all user groups. That is, the server subtracts the index (RI) of the video data block requested by the user from the user group and subtracts the index (RP) of the video data block sent by the server 10 or another group to the group. While the user terminal is included in the user group, the user group satisfies a condition that is greater than the number of video data blocks (α) received by the user group and less than the limit number (β) of video data blocks that the user terminal requesting a new service needlessly receives. Find the user group you are using.

 beta> RI-RP> alpha

In Equation 2, RP is the RP of each user group. If more than one user group is determined through Equation 2, the server selects a group having the minimum RI-RP as the user group to include the user terminal requesting the service.

If the user terminal requesting the service is included in the user group having an RP smaller than RI-β or the user terminal is included in the user group 110 having an RP greater than the RI-α, the user terminal requesting the service receives the desired video stream. The user terminal does not have to wait for a long time or is not provided with the desired video stream, so the user terminal does not play the desired playback point.

The server checks the user group to include the user terminal that requested the service through Equation 2 (504). As a result of the check, when the user group to include the user terminal is determined, the group master information of the determined user group is provided to the user terminal requesting the service. The user terminal requesting the service requests the group master of the provided user group to participate as a member. The group master granting the group participation request of the new user terminal provides an ID to the newly joined user terminal and updates the group information (505).

In step 504, if there is no user group to include the user terminal requesting the service, the server checks whether it is possible to create a new group using the user terminal requesting the service as a group master and make it a child group of another group (506). .

To create a new user group, the server applies the following equation 3 to a user group that does not have a child group. That is, the server receives the video data block received by the user group while the index of the video data block requested by the user in the user group includes the minimum video data block index LD of the group and the user terminal requesting the new service in the user group. Is larger than the sum of α, and the index of the video data block being played by each user terminal of the current user group and the video data block received by the user group while including the newly requested user terminal to the user group. Find a user group that satisfies a condition smaller than the number α.

The PP is a PP of the user group to be applied.

The server checks whether there is a user group that satisfies Equation 3 (507). As a result, if there is a user group that satisfies Equation 3, the server creates a new user group in which the user terminal requesting service is a group master, and a user group in which the user terminal is a group master satisfies Equation 3 above. Become a child group of the user group (508). The child group communicates with the master of the parent group to receive the video data block. If it is determined in step 507 that the user terminal requesting the service cannot be included in the user group or a new user group cannot be made a child group of an existing user group, the server includes a new user terminal including the user terminal requesting the service. Create a chain.

To form a new chain is to create a new user group that does not have P2P data transmission with the user group of the existing chain, where a new user group including the user terminal requesting service is the top of the chain that receives the video stream from the server. It becomes a parent group and the user terminal becomes a group master.

The top level parent group does not have its own parent group, so it must receive data streams from the server. In order for the server to create a new chain, you need to consider the free bandwidth. Since the top-level parent group receives the data stream directly from the server, it cannot create a new chain unless the server has enough free bandwidth.

Therefore, the server checks its free bandwidth and checks whether the free bandwidth is sufficient to provide a data stream (509). The server determines whether a new chain can be created by checking its free bandwidth (510).

As a result of the check, if it is determined that there is free bandwidth for creating a new chain, the server forms a new chain in which the user terminal requesting the service is the group master of the highest parent group. At this time, the server assigns a chain ID to the new chain, and the user terminal, which is the group master, generates group information including the chain ID received from the server (511).

In the above description, the batching technique can be used when the server creates a new group. That is, if multiple users request similar RIs at short time intervals and need to create new user groups to provide services to these users, they can be made into one user group. At this time, the group master of this group becomes the user who first requested the video.

If the server cannot include the user terminal in the user group, cannot create a new child group using the user terminal, or cannot create a new chain including the user terminal, the server rejects the user terminal video service request. The user terminal transmits the data to the user terminal (512).

The server accepts the user's video request in step 505 or step 508 or 511 and includes the user terminal in the group-chain structure. Thereafter, update or newly generated group information is received from the group master of the corresponding user group to confirm that the user terminal is successfully included in the group-chain structure.

In this case, the new user terminal added to the group-chain structure has not received the video data and thus does not have the video data block in the buffer of the user terminal. Therefore, the LD of the user terminal added to the existing user group except the user terminal of which the new user terminal is the group master is not the same as the LD of the group master. In this way, a member having an LD different from the LD of the group master becomes a temporary member, and the information that the user terminal is a temporary member is stored in state information of the member. However, the temporary member is to have the same LD and the group master, as described below with reference to Figure 6. After a sufficient time, the temporary member is a full member accordingly.

Hereinafter, a process of transmitting a video data block to a new user terminal added to the group-chain structure will be described.

Prior to the description, the process of transmitting the video data block includes the transmission of the video data block from the server to the user group or from the parent group to the child group, and the transmission of the video data block between members in the same user group. The process of transmitting the video data block from the server to the user group is the same as the process of transmitting the video data block by acting as a parent group with respect to the first group of the chain, and thus will not be described.

First, a process of transmitting video data blocks between groups will be described with reference to FIG. 6.

If a user terminal requests a video service from a server and is included in a user group, the user terminal receives group information (601). The user terminal checks its state in the group information to determine whether it is a regular member (602).

In this process, the temporary member becomes a full member. The buffer of the newly joined temporary member in the group stores the video data block corresponding to the required playback point, that is, the RI, and the RI remains the user until the buffer becomes full. LD becomes. As time passes, video data blocks of the index after the RI are provided from the server or the parent group and group members. In this state, other members of the same user group use the pre-RI index as LD. Since the buffer capacity is much smaller than the video capacity, the video data block having the smallest index value among the video data blocks stored over time Receive a new video data block while deleting it. Therefore, the regular member's LD gradually increases in value and eventually becomes the same as the temporary member's LD. The temporary member checks whether the LD of the group master and the LD of the group master are the same through the group information. If the two members are equal, the temporary member informs the group master that he is ready to become a full member. The group master makes a temporary member a regular member by changing the state value of the temporary member and updating the group information.

When the temporary member becomes a regular member, the LD of the user terminal becomes the same as that of the LD of the group master (0), so that the video data block stored in the buffer can be transmitted to the child group. Here, the temporary member receives the video data block from the server or the parent group and provides the received video data block to other members of the same group, but does not provide the video data block to the child group until it becomes a full member.

If the user terminal is a temporary member, it waits until it becomes a full member (603). When the user terminal becomes a regular member, the user terminal checks whether the user group to which the user terminal belongs has a child group (604). If it is determined in step 604 that there is no child group, the user terminal waits until a child group is created (605).

When a user group is created, the user terminal checks whether the remainder of dividing the group's FP by the number of full members in the group (NFM) is equal to its ID in order to transmit a video data block to the members of the child group (606). If the ID of the user terminal is equal to the remainder obtained by dividing the FP of the group by the number of authorized members in the group (NFM), the video data block of the index corresponding to the FP is read from the buffer and transmitted to the child group. Be prepared to

For example, if the FP of the group is 20, the number of authorized members (NFM) of the group is 6, and the ID of the user terminal is 2, the remainder for 20/6 is 2, so the user terminal has video data having an index of 20. It is the transmission subject of the block. The remaining members, i.e., members with IDs 0, 1, 3, 4, and 5, do not transmit video data blocks having an index of 20 to the child group.

As another example, if the FP of the group is 20, the number of members (NFM) of the group is 6, and the ID of the user terminal is 3, the remainder for 20/6 is 2, so that the user terminal cannot be a video data block transmission subject. In other words, the member whose ID is 2 is the transmission subject of the video data block whose index is 20.

According to the data stream rate R, the FP is increased after a predetermined time, and thus the block transmission subject of the video data is changed (607).

When the user terminal becomes the transmission subject of the video data block corresponding to the current FP, the member of the child group (that is, the target member) to receive the video data block is identified. The target member of the child group obtains the remainder obtained by dividing FP by the number of members (NCM) of the child group, and determines a member of the child group having an ID corresponding to the obtained remainder as the target member (608).

When the target member is determined, the user terminal transmits the video data block corresponding to the FP to the target member of the child group (609).

In the above description, a member of a parent group sends a video data block of an index corresponding to its ID + (full number of members of the same user group * N) among all video data blocks stored in a buffer to a selected member of the child group. send. N is a natural number including 0.

In the parent group, video data blocks are evenly distributed to members of the child group. That is, each member of the child group receives a video data block of an index corresponding to its ID + (number of members of the same user group * N) from the parent group. Therefore, each member of the child group must provide the other member with the received video data block.

7 shows a process in which each member of the child group transmits the received video data block to other members of the same user group. Hereinafter, a video data block transmission process between members in the same user group will be described with reference to FIG. 7.

FIG. 7 transmits a video data block, ie, video streams 130a1, 130a2, 130a3, 130a4, each member (0, 1, 2, 3) received from a member of parent group 110a to another member of group 110b. It is a process.

Each member (0, 1, 3, 4) receives the video data block from the parent group (110a), and transmits the previously received video data block to other group members until receiving the next video data block.

In this case, if the number of regular members of a group is NFM and the number of temporary members is NTM, the upload bandwidth used by the formal members of this group for video streaming is expressed by Equation 4 below.

On the other hand, when the user arbitrarily stops the service during video streaming, other members may not receive the video data block during the video data transmission process. If the maximum value of the packet delay between user terminals is d, each member may calculate the arrival time of a specific video data block. If the video data block to be received from the parent group does not arrive within the expected time, the user terminal requests any member of the parent group to retransmit the block of the video data. Accordingly, when the user terminal receives the retransmitted video data block, the user terminal transmits it to other members of the group.

Also, if a video data block to be received from another member of the group does not arrive within the expected time, the server is requested to retransmit the video data block. Each user terminal must receive a video data block until just before playback, so the RP-PP should have sufficient intervals. Also, since the user terminal cannot transmit data not received to the child group, the FP should always be smaller than the PP.

As such, retransmission increases bandwidth usage of the server and the user terminal. If the upload bandwidth usage exceeds 2 · R, the user terminal does not retransmit the video data block even if another user terminal requests retransmission of the video data block. In this case, the lost video data block is retransmitted from the server.

8 to 9, the operation of the present invention for the case where the user stops playing during the service will be described.

First, an embodiment of the present invention will be described with reference to FIG. 8 when the user explicitly informs the user to stop receiving the service.

The user terminal checks the video playback stop at the user's request (801). The user terminal varies its operation according to whether it is a group master or a general member (802). That is, if the user terminal is not the master of the group, the user terminal requests the group master (0) to delete itself from the member (803).

Accordingly, the group master (0) deletes the user terminal from the group member according to the member deletion request of the user terminal, updates the group information, and transmits the updated group information to the server, the parent and the child group (804). At this time, the group master updates the member list while updating the member list. That is, if the ID of the deleted member is 3, the ID of the member having an ID of 3 or more is lowered by one. In operation 804, the group information from which the user terminal is deleted is transmitted to the server 10, the parent group, and the child group, so that the user terminal can stop playing the video (805).

On the other hand, if the user terminal is a group master in step 802, the user terminal checks whether there is another member through the group information (806). If no other member exists, the user terminal requests the server to delete the user group (807). In response to the request of the user terminal, the server deletes the user group to which the user terminal belongs, and then connects the parent group and the child group of the user group (808). If there is no other group in the chain to which the user terminal belongs by deleting the user group to which the user terminal belongs, the chain is also deleted.

On the other hand, if it is confirmed that the user terminal is a group master and there are other members, the user delegates the role of the group master to the member whose ID is the smallest (809). A member who becomes a group master by the user terminal to stop playing deletes the user terminal to stop playing from the group and updates the group information (810).

FIG. 9 is a diagram for explaining a process of updating group information when a user stops playing a video without notifying the user to stop receiving the service.

According to the above-described P2P-based video service method according to the present invention, the group information is not updated unless the user notifies the service suspension, thereby providing the video stream to the user terminal that has stopped the service. However, the user terminal that stops the service does not provide a video stream to other members and members of the child group. As a result, unless the server or group master is informed of the user's service suspension in any form, other members will not receive the video data block until they request retransmission.

The present invention utilizes a heart-bit message to solve the problem. The heartbeat message is periodically generated at every member and sent to a specific member. The heartbeat message contains the IP address information of the member. The member sends a heartbeat message to other members in the same user group. The member receiving the heartbeat message from the other members checks the ID of the member sending the heartbeat message by comparing the IP address of the received heartbeat message with the group information. Each member monitors whether a heartbeat message of a specific member is received within a predetermined time T0. If each member does not receive a heartbeat message from a particular member for a predetermined time T0, the member determines that this situation is a timeout situation. A particular member has timed out means that the particular member has timed out the video service.

Herein, the member is set to TO1 if the member transmitting the heartbeat message is TO1, and TO2 if the member of the other user group transmits the heartbeat message. TO1 is shorter than TO2. Making TO1 shorter than TO2 means that members of the same user group are notified of the deletion of members within the same user group before the parent or child group, and the parent and child groups are notified of the updated group information, thereby leaving the group master or leaving many members. This is to prevent the service error caused by.

Meanwhile, each member sends a heartbeat message to a specific member and receives a heartbeat message from the specific member. Accordingly, each member in the same user group transmits and receives a heartbeat message as shown in FIG. 9.

First, as shown in FIG. 9, the group master (0) of the user group (110b) periodically sends a heart-beat message to the group master (0) of the parent group (110a) and the group master (0) of the child group (110c). Send it.

Each member 0 to 12 of the user group 110b periodically transmits a heartbeat message to the following members when their ID is I.

1. ID = Parent member

2. ID = In-class member

3. Child member with ID = [Ih + 1, Ih + h]

9, an example will be described. As shown in FIG. 9, h = 3. And for members with ID = 2 Is [2/3], so ID = 0. Therefore, a heart-beat message is sent to the member whose ID is 0 (parent member). And Since [1, 3] sends heart-beat messages to members with IDs 1, 2, and 3 (equivalent members). In addition, since [I / h + 1, I / h + h] is [7, 9], a heart-beat message is transmitted to members (child members) having IDs 7, 8, and 9. Where h can be arbitrarily determined. Increasing h increases the stability but increases the load of the user terminal. Increasing h decreases the stability but decreases the load of the user terminal.

Referring to FIG. 9, a process of processing a master in each group according to service termination of a user terminal will be described.

If the user terminal stops playing the video without notifying the other member that the video has been stopped, the terminals receiving the heartbeat message from the user terminal may not receive the heartbeat message from the user terminal which has stopped service for a certain period of time. . In this case, other user terminals determine that a timeout situation has occurred.

When a user terminal in a group stops a service, the user terminal that stops the service may be a member of the group or a master terminal of the group. Therefore, the processing of the two cases will be described separately.

First, a case in which a user terminal which has stopped a service is only a member terminal in a group will be described. The user terminal transmitting and receiving a heart-beat message with the user terminal that has stopped the service notifies the master terminal of the group that a timeout has occurred in the user terminal that has stopped the service. When a member who has been sending or receiving a heart-beat message with the group's master terminal stops service, the group's master terminal recognizes it immediately. As such, when the master of the group is notified or acknowledged that a particular member has stopped service, the corresponding user terminal is deleted from the user group, and when the ID of the remaining members is needed through the group information, the ID of the corresponding members is updated. . Then, the group master terminal notifies the updated group information to other members and parent / child groups.

Next, a case in which the user terminal that has stopped a service is a group master will be described.

The master terminal of the group not only transmits and receives a heartbeat message with the master terminal of the parent group and the master terminal of the child group, but also transmits and receives a heartbeat message with other member terminals in the group. Therefore, when the master terminal stops service, the member terminal of the group, the master terminal of the parent group, and the master terminal of the child group are recognized. However, since the heart-beat message timeout timer TO1 between members in the group is shorter than the heart-beat message timeout timer TO2 with the master terminal of another group, the members in the group are not aware of the service interruption of the master terminal. You get to know first. Therefore, when the master terminal in the group stops the service, the member with the smallest ID among the members of the group that exchanged the heartbeat message with the group master is set as the group master, and the newly set terminal is the existing master terminal that has stopped the service. Is deleted from the user group information, and the newly updated user group information is notified to other members, the parent group, and the child group in the group. The heartbeat message is transmitted and received according to the updated user group information. At this time, members of the group that exchanged heartbeat messages with the group master also exchange heartbeat messages, so that several members do not attempt to become the group master at the same time.

On the other hand, the master of the parent group and the master of the child group that was sending and receiving heart-beat messages with the master terminal of the group does not receive the heart-beat message from the master terminal of the group, even after a certain time has passed from the master of the new group If no -bit message is received, it determines that all members of the current group have stopped the service and notifies the server that the current group has been destroyed.

The server receiving the group destruction fact deletes the information about the destroyed group, connects the parent group and the child group of the destroyed user group in the parent / child relationship, and then connects the parent / child group in the newly parent / child relationship. Inform parent and child group information.

Meanwhile, the above-described embodiment of the present invention is an embodiment of the distributed terminal management method in order to maintain the group-chain structure while reducing the load on the server. That is, in order to prevent the load of the server, the interaction between the user terminals constituting the group-maintaining group-chain structure (that is, group information between the group master, the group master candidate and the terminal, and the heart-beat message between the terminals) Forwarding) allows the user terminal to manage the group-chain structure on behalf of the server.

The present invention can be implemented to comply with the centralized terminal management method, in addition to the distributed terminal management method described above. The centralized terminal management method refers to an operation performed by a user terminal (that is, selecting a group master among members of a group, checking whether a user terminal is still present through a heartbeat message, and updating group information according to addition / deletion of terminals in a group). And an operation such as notifying the member of the updated group information). In this case, the user terminal may provide the server with the information provided to the group master, and the server may act as the group master. It is obvious that the operation of the server for the centralized terminal management can be easily implemented by those skilled in the art through the above-described embodiments of the present invention.

The technical spirit of the present invention has been described above with reference to the accompanying drawings, but this is by way of example only and not intended to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

The present invention has the effect of enabling a video service using a small server bandwidth regardless of the number of users that the server is being serviced, thereby allowing the service provider to reduce the cost required to provide the service, thereby reducing the service fee. It becomes cheaper. According to the present invention, instead of providing a certain amount of upload bandwidth, the user can be provided with a seamless on-demand video service at a low price.

1 is a block diagram of a P2P based video service system according to the present invention;

2 is a format diagram of a video file provided from a server.

3 is a format diagram of video data stored in a buffer of a user terminal according to the present invention;

4 is a view for explaining a process in which group information is known to each member according to the present invention.

5 is a flowchart illustrating a processing procedure in a server according to an embodiment of the present invention.

6 is a flowchart illustrating a video data block transmission process from a parent group to a child group according to an embodiment of the present invention.

7 is a view for explaining a video data transmission process between members in the same group according to an embodiment of the present invention.

8 is a flowchart illustrating a process of deleting a user terminal from a group-chain structure when the user terminal requests to stop service according to the present invention.

9 is a view for explaining a user terminal deletion process when the user terminal terminates the service without notifying the service suspension according to an embodiment of the present invention.

Claims (16)

A server for indexing and storing video data in units of blocks in which video files are divided into a predetermined size, and managing information related to a user group including at least one user terminal currently connected to a video service; And Including a plurality of user terminals connected to the server via the Internet, currently receiving a video service, The user group includes at least one master user terminal, The master user terminal is responsible for the addition / deletion of another user terminal to the group, and updates the user group information, and updates the updated user group information with the master user terminal of another group and the user terminal and server belonging to its own group. Provided by When the server receives a video block transmission request of a specific block from any user terminal, the server determines a transmission subject that can provide video data of the block requested by the user terminal, The user group includes a first group for receiving the video data of the block unit directly from the server, and a second group for receiving the video data of the block unit buffered to the user terminal in the first group, The user terminal of each group is a video service system, characterized in that for playing the video data of the block unit having the same index. The method of claim 1, The group information includes an identifier of a chain to which a group belongs, a time when group information is generated, a time at which group information starts to be used, a number of user terminals belonging to a group, and an IP address of a user terminal belonging to a group. And list information containing the port and state, an index of a video data block transmitted by a server or another user group to the group when the group information is generated, and an index information of the minimum video data block when the group information is generated. Video service system, characterized in that. The method according to claim 1 or 2, The server checks the index of the video data block requested by the user terminal, searches whether there is a user group that can include the user terminal requesting a new service among user groups currently receiving video service, Providing the master user terminal information of the user group to the user terminal requesting the new service, If a user group to include the newly requested user terminal is not found, the user may request to provide the newly requested video data block to the newly requested user terminal without having a child group. If there is a group search, and if a user group meeting the condition is found, a new group is created as the master terminal of the newly requested user terminal, and the generated user information is notified to the searched user group. And a group as a child group of the searched group. The method of claim 3, wherein If there is no user group capable of delivering the requested video data block to the user terminal requesting the new service, the server directly requests the new service if the current free bandwidth is enough to transmit the video data stream. And a video data block requested by the terminal. The method of claim 4, wherein The user terminal added to the user group becomes a formal member of the parent group when the minimum video data block index of its user group information is equal to the minimum video data block index of the master terminal of the parent group to which the user group belongs. And a video data block can be transmitted to a user terminal of a child group after being a member. The method of claim 5, When the user terminal in the parent group transmits the video data block to the user terminal of the child group, the index of the video data block to be transmitted to the user terminal of the current child group among the user terminals in the parent group is determined by And a user terminal having the same ID as the remainder divided by the number transmits the video data block to a specific user terminal of the child group. The method of claim 6, The child group user terminal to receive a video data block from the parent group user terminal is a terminal having an ID as a remainder obtained by dividing the index of the video data block to be transmitted by the number of members of the child group. . The method of claim 7, wherein And when a specific user terminal among user terminals belonging to one group receives a video data block from a parent group, the received video data block is delivered to all other user terminals belonging to the same group. The method of claim 8, When a user terminal of a specific group of the video services requests to stop the service, after deleting the user terminal requesting the service stop from the group, the master of the other group that exchanges the updated group information with the member terminal in the same group and the video data block Video service system, characterized in that the transmission to the terminal and the server. The method of claim 9, If the user terminal that has stopped the service is a master terminal of a group, after setting another user terminal in the specific group as a master terminal, the group information is updated by the newly set master terminal. The method of claim 10, A video service system, characterized in that a heart-beat message is transmitted and received at regular intervals between user terminals in the same group and master terminals of groups that exchange video data blocks to detect service departure of user terminals belonging to the group. A server for indexing and storing video data in units of blocks in which video files are divided into predetermined sizes, and managing information related to a user group including at least one user terminal currently connected to a video service; In a video service method in a system in which a user terminal connected through the Internet belongs to one user group, and each user group has a master terminal in charge of addition / deletion within a group of another user terminal. When the server receives a video data transmission request of a specific block from an arbitrary user terminal, the server checks the index of the video data block requested by the user terminal, and requests a new service among user groups currently receiving video service. A first step of searching for a user group capable of including the user terminal; A second step of providing master terminal information of the user group found in the first step to the user terminal requesting the new service; If the user group to include the user terminal requesting the new service is not found in the first step, the video data block requested by the user to the user terminal requesting the new service without having a child group among the already created groups Searching for whether there is a group capable of providing a third step; When a user group meeting the condition is found in the third step, a new group is created, wherein the newly requested user terminal is the master terminal, and the newly created user information is notified to the searched user group. A fourth step of making a group a child group of the searched user group; A fifth step of checking whether the current free bandwidth is a bandwidth capable of transmitting the requested video data block if there is no user group capable of delivering the requested video data block to the newly requested user terminal in the third step; ; A sixth step of transmitting the requested video data block directly to the user terminal that has requested the new service if there is available bandwidth that can be transmitted in the fifth step; And And a seventh step of notifying that the service cannot be provided if there is no free bandwidth in the fifth step. The method of claim 12, The group information includes an identifier of a chain to which a group belongs, a time when group information is generated, a time at which group information starts to be used, a number of user terminals belonging to a group, and an IP address of a user terminal belonging to a group. And index information of the video data block received from the server or another user group when the group information is generated, and index information of the minimum video data block when the group information is generated. Video service method. The method of claim 12, Among the user groups currently receiving the video service in the first step, a user group that may include the user terminal requesting a new service, The value obtained by subtracting the index (RP) of the video data block that the server 10 or another group sends to the group from the index (RI) of the video data block requested by the user is the user group requesting the newly requested service. It is a group that satisfies a condition that is larger than the number α of video data blocks received by each user group during inclusion in the subframe, and that the user terminal requesting the new service satisfies a condition smaller than the limit number β of video data blocks unnecessarily received. Video service method. The method of claim 12, A user group capable of providing a video data block requested by a user to the user terminal requesting the new service among the groups already created in the third step may include: The index of the video data block requested by the user indicates the minimum video data block index LD of the group and the number α of the video data blocks received by the user group while including the newly requested user terminal in the user group. Larger than the sum, the index of the video data block being played by each user terminal of the current user group and the number of video data blocks received by each user group while including the newly requested user terminal in the user group (β) The video service method, characterized in that the user group that satisfies a condition smaller than the sum. The method of claim 15, In the fourth step, the searched user group becomes a parent group, and the newly created group becomes a child group. A user terminal having an ID equal to the remainder obtained by dividing an index of a video data block to be transmitted to a user terminal of a current child group among the user terminals in the parent group by the number of full members in the current group; And transmitting a video data block to a user terminal of a child group having an ID of a remainder obtained by dividing an index of a video data block to be transmitted by the number of members of the child group.