JP2002118553A - Broadcast system and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a broadcast system enabling users to freely select view start times of program data, with efficiently using communication channels. SOLUTION: A server 10 comprises a request processor 12 for dynamically changing communication means for use in data transmission according to the number of clients 20 requesting program data and a digest generator 13 for generating digest of program data as long as required. It broadcasts much requested program data to the clients in one to multiple communication and less requested program data in one to one communication. Upon receipt of a request during broadcasting of program data, it generates a digest of already broadcast parts of the program data and transmits it to the client. The client 20 first receives the digest of the program data and changes over for receiving the originally broadcasting program data after ending the reception of the digest.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcasting system and a method therefor, and more particularly, to a server and a plurality of clients connected via a communication medium, and the server transmitting program data in response to a request from the client. This is related to the broadcasting system as described above.

[0002]

2. Description of the Related Art With the advancement of network technology, it has become possible to distribute broadcasts conventionally performed using broadcast radio waves on networks. For example, JP-A-9
Japanese Patent Application Laid-Open No. 149354 discloses a technique in which a video server and a set-top box serving as a client are connected by a high-speed network bus, and necessary video data is transferred from the server to the client and played according to a request from a user. Have been. In addition, the user can request reproduction of video data at any time.

[0003]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 9-1 is disclosed.
In a video distribution system such as that disclosed in Japanese Patent No. 49354, a server and a client perform one-to-one communication.
Is an integer of 2 or more), when a request for video data is received from two or more clients, a communication band that is n times as large as that when one client is used is required. On the other hand, when video data is transmitted on a one-to-many basis as in an existing television broadcast, there is an advantage that a fixed communication band can be used regardless of the number of clients. It is transmitted according to a predetermined schedule, and the disadvantage is that video data cannot be viewed from the beginning at an arbitrary time, and when data of the same size is transmitted, one-to-many rather than one-to-one communication Is more costly, and is inefficient when the number of receiving clients is small.

[0004] In the case of a form in which video data broadcast like a home server is reproduced while storing the data in an auxiliary storage device on the client, the video data is transmitted to a plurality of clients in a certain communication band. , The client can freely select the viewing start time of the video data on the client side, but (a) a large-capacity auxiliary storage device is required for the client; (b) stored in the client Video data that cannot be viewed cannot be viewed.

An object of the present invention is to allow a client to flexibly designate a viewing start time of video data without providing any auxiliary storage device in the client, and to set a required communication band and communication cost as required. It is an object of the present invention to provide a broadcasting system and method for reducing the same.

[0006]

According to the present invention, a server and a plurality of clients are connected via a communication medium,
A broadcasting system in which the server transmits program data in response to a request from the client,
The server dynamically changes the communication method and communication path of the communication medium according to an increase or decrease in the number of clients requesting the program data during a period in which the program data is transmitted to the client. A broadcast system characterized by including communication medium change control means for controlling is obtained.

The communication medium change control means performs a one-to-one communication when the number of clients requesting the program data is smaller than a predetermined number. It is characterized in that it is switched to the one-to-many communication system, and the one-to-many communication system is a broadcast communication. The one-to-one communication method is characterized by communication using a telephone line as a communication path.

Further, the communication medium change control means dynamically changes and controls a communication system and a communication path of the communication medium according to a predetermined schedule. Further, the server includes a data storage unit that stores the program data, and a transmission unit that transmits the stored data from the data storage unit, and further includes a data generation unit that generates the program data to be transmitted in real time. Wherein the transmitting means is capable of transmitting the data generated by the data generating means.

Further, the client is characterized in that it includes means for dynamically responding to a change in the communication method or communication path of the communication medium. Furthermore, if the server receives a request for the program data from another client during the period of transmitting the program data, the server may transmit the program data from the start of transmission of the program data to the reception of the request. Digest generating means for generating the digest data from the transmitted program data and the program data to be transmitted while transmitting the digest data of the program to the client, including the digest data and the following program data. It is characterized in that it is transmitted.

[0010] The client may further include means for receiving the digest data, and switching to receive the program data being transmitted after the reception of the digest data, and wherein the digest generating means comprises: The start point of the range for generating data is not from the start point of the program data but from the time point specified by the client. The end point of the digest data generation range can be specified by the client.

[0011] Further, the storage means stores in advance one or more digest data of the program data, and the transmission means reads and transmits the digest data from the storage means in response to a request from the client. It is characterized by doing. Further, the server is:
Means for charging the client according to the communication medium and the quality of the digest data, further comprising, collecting the user information about the client, the communication medium used when transmitting the program data, The apparatus further comprises means for determining the quality of the digest data.

According to the present invention, there is provided a broadcasting method in which a server and a plurality of clients are connected via a communication medium, and the server transmits program data in response to a request from the client. In the server,
A communication medium for dynamically changing and controlling a communication method and a communication path of the communication medium according to an increase or decrease in the number of clients requesting the program data during a period in which the program data is being transmitted to the client; A broadcasting method characterized by including a change control step is obtained.

In the communication medium change control step, if the number of clients requesting the program data is smaller than a predetermined number, the communication is performed by a one-to-one communication method. It is characterized in that it is switched to the one-to-many communication system, and the one-to-many communication system is a broadcast communication. The one-to-one communication method is characterized by communication using a telephone line as a communication path.

Further, the communication medium change control step includes:
The communication system and the communication path of the communication medium are dynamically changed and controlled according to a predetermined schedule. Further, the server includes a step of storing the program data in a data storage unit in advance, and a transmitting step of transmitting the stored data from the data storage unit. The method further includes the step of creating program data to be generated in real time, and the transmitting step enables the created data to be transmitted.

[0015] The method is characterized in that the client includes a step of dynamically responding to a change in the communication system or communication path of the communication medium. Further, in the server, if another client requests this program data during the period of transmitting the program data, the server transmits the program data from the start of transmission of the program data to the reception of the request. A digest generating step of generating the digest data from the program data of the program and the program data to be transmitted while transmitting the digest data of the program to the client, and transmitting the digest data and the following program data. It is characterized by doing.

[0016] The method may further include a step of, at the client, receiving the digest data and, after completion of the reception, switching to receive the program data being transmitted. Further, in the digest generation step, a start point of a range in which the digest data is generated is set not from a start point of the program data but from a time point specified by the client. Further, the client can designate the end point of the generation range of the digest data.

The storage means stores in advance one or more digest data of the program data, and the transmitting step reads and transmits the digest data from the storage means in response to a request from the client. It is characterized by doing. The server may further include a step of charging the client according to the quality of the communication medium and the digest, and the server may collect user information on the client. And determining the quality of the digest data and the communication medium to be used when transmitting the program data.

The operation of the present invention will be described. The user requests program data to be viewed from the server via the client, and the client receives the program data transmitted from the server and presents the program data to the user. At this time,
The request processing section of the server is used to transmit program data based on the number of clients transmitting the same program data as the requested program data and the communication bandwidth required to transmit the requested program data. Communication means to be dynamically changed. That is, when the number of clients requesting a certain program data is small, the program data is transmitted to each client by one-to-one communication, and when the number of clients exceeds a predetermined threshold, the same program data is transmitted. The communication means used for the communication is switched to one-to-many communication for all clients requesting the program data. On the other hand, when certain program data is transmitted by one-to-many communication and the number of clients requesting the program data falls below a predetermined threshold, the program data is transmitted. Is switched to one-to-one communication for each client.

Further, in the above-mentioned broadcasting system, a time transition of the number of clients requesting the program data to be transmitted is predicted by audience rating survey or the like, and the program data is transmitted based on the expected increase / decrease of the number of clients. To dynamically change the communication means used for the communication.

By the above operation, a large amount of communication band is occupied for transmitting program data to many clients by one-to-one communication, and one-to-many communication which usually costs more than one-to-one communication The effect of reducing waste such as using a small number of clients can be obtained.

Also, when a user requests the server for a program data through a client in a state where the program data is transmitted by one-to-many communication, a digest of the already transmitted portion of the program data and the client are transmitted. The digest generation unit generates a digest of a portion to be transmitted while the program data is being transmitted, and the generated digest is transmitted to the client requesting the program data.
Transmit by one-to-one communication. The client requesting the program data first receives a digest of the program data transmitted by one-to-one communication and presents it to the user. After the digest reception is completed, the reception is switched to the reception of the program data which is originally being transmitted by one-to-many communication, and the program data is continuously presented to the user.

By the above operation, even if the user requests the program data which has already been transmitted by one-to-many communication from the middle, the program data can be viewed from the beginning, and the digest transmission can be performed. After the end, the client receives the continuation of the program data by one-to-many communication, so that there is an effect that no extra communication is required except for transmitting the digest. Further, according to the present invention, there is no need to prepare an auxiliary storage device on the client side, so that
It is also possible to reduce the cost and size of the client.

Furthermore, the client that requests the program data can freely specify the range for generating the digest, not from the start of the program data to the portion to be transmitted before the digest transmission to the client is completed. To do. As a result, it is possible to obtain the effect that the user can receive the digest excluding the unwanted part of the program data.

Further, in the above-mentioned broadcasting system, a digest of program data is not generated at the time of receiving a request from a client, but is generated in advance in the data storage unit by generating a digest of several types in length. When a request is received from the client and stored in the data storage unit, a function of selecting a digest in the range closest to the range of the digest determined by the above procedure and transmitting the digest to the client is configured. With such a function, the above-described effects can be obtained without generating a digest in real time.

The program data created by the data creation unit is transmitted from the data transmission unit to the client and is accumulated in the data accumulation unit. When there is a request for the same program data from the client, a digest is created from the program data accumulated in real time, and the program data and its digest are transmitted to the client according to the above procedure. According to the above operation, the digest transmission can be performed not only for the program data previously stored in the data storage unit but also for the program data generated in real time such as a live video.

Further, the system is configured to have a function of charging for a request from a client based on a combination of the type of communication means used for transmitting program data and the quality of the digest generated by the digest generating unit. As a result, it is possible to provide appropriate services to users at appropriate prices.

Further, the user information of the client is managed in advance by the request processing unit, and the type of communication means used when transmitting data using the user information and the quality of the digest generated by the digest generation unit Is configured to have the function of determining This makes it possible to provide a service adapted for each user.

[0028]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing one configuration example of the broadcasting system according to the present embodiment. This broadcasting system is composed of N (N is an arbitrary number of 1 or more, for example, N
= 3) is connected to the server 10 and the client 20 connected by the communication path of FIG. In FIG. 1, the number of clients is 1 for convenience, but it is assumed that two or more clients are actually connected. Further, in the following description, only the elements indispensable for carrying out the present invention are shown, and the description of the same elements as those of the conventional product well known to those skilled in the art is omitted.

The server 10 shown in FIG. 1 includes a data storage unit 11 for storing program data to be transmitted to a client, and a request for deciding communication means in accordance with the transmission status of the data transmission unit 15 and the request content from the client 20. A processing unit 12, a digest generation unit 13 that generates a digest of the program data stored in the data storage unit 11 in accordance with the instruction content from the request processing unit 12, and a communication method and a communication path in accordance with the instruction content from the request processing unit 12. And a digest of program data stored in the data storage unit 11 or a digest of program data generated by the digest generation unit 13 in accordance with the instruction from the communication unit selection unit 14. Data transmission unit 15 and program data stored in the data storage unit 11 And a data creation unit 16 for forming.

Here, the communication means refers to the type of communication path connecting the server 10 and the client 20 and the type of communication method used when data is transmitted from the server 10 to the client 20. The type is, for example, a wired line such as Ethernet (registered trademark) or a telephone line, or a wireless line such as broadcast radio waves or wireless communication. The type of communication system is, for example, one-to-one. This refers to unicast for communication and multicast or broadcast for one-to-many communication.

The program data is multimedia data composed of moving pictures and sounds browsed by the user of the client 20, and is, for example, MPEG2 format video data.

The client 20 in FIG. 1 includes a data request unit 21 for requesting program data from a server, a data receiving unit 22 for receiving program data sent from the server through a communication path, and one or more types of communication means. A data selector 23 for instructing selection of program data to be received by the data receiver 22 from program data sent from the server, and a data output unit 24 for presenting the program data received by the data receiver 22 to the user And

Next, the operation contents when the number of clients 20 receiving program data increases in the above-mentioned broadcasting system will be specifically described with reference to the drawings. Server 10
The request processing unit 12 always waits for a program data request from the client 20, and when there is a request, the program data stored in the data storage unit 11 is processed according to the processing procedure shown in FIG. Send. When receiving the request (step S1), the request processing unit 12 transmits the requested program data from the data transmission unit 15 when the request and the communication band required for transmitting the requested program data are received. It is checked in which area of FIG. 3 the state determined from the number of clients 20 is located (step S2).

FIG. 3 shows an example of a criterion for selecting a communication means possessed by the request processing unit 12. For example, program data requiring a wide communication band and the number of clients to be transmitted are determined. In many cases, ie, FIG.
In the case of being located in the area B, the program data is transmitted by broadcasting using broadcast radio waves, and conversely, when the program data is sufficient in a narrow communication band and the number of transmitting clients is small, that is, in FIG. When located in the area A, program data is transmitted by unicast using a telephone line.

When the program data request is received from the client 20, if the program data is already located in the area B in FIG. 3, the program data is being transmitted by broadcast. The unit 14 instructs the requesting client 20 to receive the broadcast program data (steps S3 and S4).

When the program data request is received from the client 20, if it is located in the area A of FIG. 3, it is checked whether or not the number of clients increases by one to shift to the area B (step S5). If the processing does not shift to the area B, the communication means selection unit 14 of the server 10 instructs the requesting client 20 to receive the program data transmitted in unicast (step S10).
6) The transmission of the program data is started from the data transmission unit 15 to the client 20 by unicast (step S7).

On the other hand, by increasing the number of clients by one,
When shifting from the area A to the area B in FIG.
The communication means selection unit 14 of 0 issues an instruction to switch the communication means from unicast to broadcast to all the clients 20 receiving the requested program data (step S8).
Instructs the data transmission unit 15 to switch the transmission of the program data from unicast to broadcast.
Further, it instructs the requesting client 20 to receive the program data transmitted by broadcast.

The client 20 receives a request for program data from the user, and receives the program data according to the processing procedure shown in FIG. Data request unit 21
Requests the server 10 for desired program data according to the request from the user (step S1).
1). After transmitting the request, the data selection unit 23 waits for an instruction from a communication unit used to receive the program data transmitted from the server 10 (step S1).
2), the instruction regarding the communication means is transferred to the data receiving unit 22.

The data receiving section 22 receives program data transmitted by broadcast or program data transmitted by unicast in accordance with an instruction from the data selecting section 23, and transfers the received program data to the data output section 24. . The data output unit 24 presents the program data passed from the data receiving unit 22 to the user using an existing data output device such as a display or a speaker.

Client 2 receiving program data
0 indicates whether the transmission of the program data from the server 10 ends or
Receive new program data requests from users,
Alternatively, the reception of the program data and the presentation to the user are continued until the stop of the reception of the program data is instructed (step S1).
4, S15). In the meantime, the data selection unit 23
Waits for an instruction to switch communication means (step S1)
6, S17), when receiving an instruction to switch from unicast to broadcast or to switch from broadcast to unicast, instructs the data receiving unit 22 to perform reception of program data by broadcast or unicast. Out, data receiving unit 2
2 switches communication means used for receiving program data according to the instruction.

Client 2 receiving program data
0 indicates whether the transmission of the program data from the server 10 ends or
When the user instructs to stop receiving the program data (steps S18 and S19), the reception of the program data performed by the data receiving unit 22 and the presentation of the program data performed by the data output unit 24 to the user are performed. Stops (step S20),
Wait for a program data request from the user. Further, the data request unit 21 notifies the server 10 of the end of the reception of the program data.

Client 2 receiving program data
0, upon receiving a request for new program data from the user, stops the reception of the program data by the data receiving unit 22 and the presentation of the program data by the data output unit 24 to the user at that time. The program data newly requested is received and presented to the user according to the procedure.

Next, the operation of the above-described broadcasting system when the number of clients 20 receiving program data is reduced will be specifically described with reference to the drawings.

Upon receiving the program data reception end notification from the client 20 transmitting the program data, the server 10 reselects the communication means according to the processing procedure shown in FIG. Upon receiving the reception end notification from the client 20 (step S21), the request processing unit 12 checks in which area in FIG. 3 the transmission state of the program data whose reception has ended is located (step S22). If it is located in the area A before receiving the end notification, the transmission of the program data by the unicast is continued as before (step S23).

If it is located in the area B, it is checked whether the transmission state shifts from the area B to the area A in FIG. 3 due to the decrease in the number of clients 20 by one (step S24). If not, the transmission of the program data by broadcasting is continued as before (step S25). When shifting from the area B to the area A,
The communication unit selection unit 14 of the server 10 issues an instruction to switch the communication unit from broadcast to unicast to all the clients 20 other than the client that has transmitted the reception end and receiving the program data (step S26). Further, the communication means selecting unit 14 instructs the data transmitting unit 15 to switch the transmission of the program data from broadcast to unicast. The data transmission unit 15 switches the communication means to unicast according to the instruction of the communication means selection unit 14 and continues transmission of the program data.

As described above, in the broadcasting system of the present embodiment, the communication means is dynamically switched according to the increase or decrease of the number of clients requesting program data.
Efficient use of communication paths, such as occupying a large amount of communication bandwidth to transmit to a large number of clients by unicast, or transmitting expensive broadcasts to a small number of clients, Operation becomes possible.

In the description of the above embodiment, the communication means at the time of being located in the area A and the area B in FIG. Although both methods are different, a form in which the communication path is the same and only the communication method is switched, or a form in which the communication method is the same and only the communication path is switched may be employed.

In the description of the above embodiment, the number of clients 20 that request program data uses the number of clients 20 that actually transmit requests to the request processing unit 12. The time transition of the number of clients requesting program data is predicted in advance by a rating survey or the like, and the communication means used to transmit program data is dynamically switched based on the estimated number of clients. Alternatively, the communication unit selection unit 14 may use a broadcast to instruct the client 20 to switch the communication unit.

In the above embodiment, the client 20
Since there is no need to send a request from the client 20 to the server 10, it is possible to configure a broadcasting system that dynamically changes communication means without preparing a communication path from the client 20 to the server 10.

Next, the operation of the above-described broadcasting system when the client 20 receiving program data requests distribution of a program digest will be specifically described with reference to the drawings. Here, the program digest is program data that can be presented in a shorter time than originally required to present the program data by extracting a part of the program data or increasing the reproduction speed.

FIG. 6 shows a flow of the program data transmitted from the server 10 when the client 20 requests the distribution of the program digest. FIG. 6 shows a state R at the time R at which the client 20 requests the program data C, and the program data C has already been broadcasted and transmitted to another client 20 for (request time R-program start time S). Is represented. The transmission of the program data C ends at the program end time E.

FIG. 7 shows that the client 20 requesting the program data C sends the program data not from the request time R in the middle of the program data C but from the program start time S to the program end time E which is the entire program data C. 3 shows the flow of program data when a request for a program digest is made to the server 10 in order to receive the program digest in the range up to. The client 20 receives the program digest of the program data C by unicast from the request time R to the digest end time D, and receives the program data C by broadcast from the digest end time D to the program end time E.

FIG. 8 shows the operation procedure of the server 10 for realizing the flow of the program data shown in FIGS. 6 and 7, and FIG. 9 shows the operation procedure of the client. Here, time T in the figure
1, T2 is a parameter for determining a program digest generation operation, and any value that satisfies the constraint condition of T1>T2;
For example, T1 = 10 minutes and T2 = 3 minutes are set. The scale P in the figure is a parameter for determining the length of the program digest to be generated, and an arbitrary value that satisfies the constraint condition of P> 0, for example, P = 2 is set.

The server 10 always waits for a program data request from the client 20 in the request processing unit 12 while transmitting the program data C stored in the data storage unit 11 by broadcasting. , The program digest of the program data C stored in the data storage unit 11 is transmitted according to the processing procedure shown in FIG.

Upon receiving the request (step S31), the request processing unit 12 checks whether the value of (program end time E-request time R) is equal to or less than time T1 (step S32). If the time is less than the time T1, the digest end time D is set to the same value as the program end time E (step S33), and the process proceeds to the program digest generation processing. If it is longer than time T1, it is checked whether the value of (request time R-program start time S) / P is less than time T2 (step S34), and if less than time T2, digest end time D is (request time R-program start time S) / P + request time R
(Step S35). If it is equal to or longer than the time T2, the digest end time D is set to (time T2 + request time R) (step S36).

The digest generating unit 13 is configured to execute, for example, JP-A-09-13893 and JP-A-09-27099 based on the digest end time D determined by the request processing unit 12 in accordance with a request from the client 20.
No. 7, using a known method disclosed in Japanese Patent Publication No. 7-203, from a program data having a length from the program start time S to the digest end time D of the program data C, a length corresponding to the value of (digest end time D-request time R). Then, a program digest having a certain length is generated (step S37).

The data transmitting unit 15 transmits the program digest generated by the digest generating unit 13 to the client 20 requesting the program data C by unicast (step S38). When the transmission of the program digest is completed, the communication means selecting unit 14 sets the client 2
0, an instruction to switch the communication means from unicast to broadcast is issued (step S39). In addition, the data transmission unit 15 also transmits the above-mentioned program digest,
The broadcast transmission of the program data C is performed in parallel.

The client 20 that has requested the program digest of the program data C from the server 10 receives the program data according to the processing procedure shown in FIG. The data request unit 21 requests the server 10 for a program digest of the program data C desired by the user (step S41). After transmitting the request, the data receiving unit 22 receives the program digest of the program data C transmitted by unicast from the server 10 and passes the received program digest to the data output unit 24. The data output unit 24 presents the program digest passed from the data receiving unit 22 to the user using an existing data output device such as a display or a speaker (step S42).

The data selection unit 23 waits for an instruction to switch the communication means from the server 10 while the data reception unit 22 is receiving the program digest, and receives an instruction to switch to the broadcast from the server 10 (step S43). , And instructs the data receiving unit 22 to receive the program data by broadcasting. The data receiving unit 22 that has received the instruction to switch to the broadcast from the data selection unit 23 ends the reception of the program digest by unicast, and starts receiving the program data C transmitted by broadcast. The received program data C is transferred to the data output unit 24 and presented to the user (step S44).

As described above, in the broadcasting system according to the present embodiment, the client receives the program data that has already been transmitted at the time of requesting the program data as the program digest. Since the format is to receive the program data transmitted by broadcast, even if the program is requested in the middle of the program data, the data from the start of the program data can be obtained, and the server Since program data is transmitted by broadcast except for transmission of digests, the communication bandwidth required for transmission of common parts other than program digests is constant even if there are requests from multiple clients at different times. The required communication bandwidth is transmitted to individual terminals by unicast program data. Compared to the case where, it is possible to reduce.

Even if the client starts receiving the program data later than the program start time, the client can make the reception end time of the program data the same as the program end time.

In the description of the above embodiment, the communication system is switched between unicast and broadcast. However, the communication routes may be the same or different.

In the description of the above embodiment, the timing at which the client 20 switches the communication system used to receive program data or the program digest from unicast to broadcast is determined by the server 10.
It is assumed that the switching instruction is received from the server 10. However, the switching instruction is not issued from the server 10 at all, and the client 20 may determine that the point at which the transmitted program digest ends is the switching timing of the communication method. Good.

In the description of the above embodiment, the digest generation unit 13 generates a program digest from program data in the range from the program start time S to the digest end time D. 10, when the client 20 requests the program digest,
One or both of the start time and the scale P of the range for generating the program digest are passed, and the digest generating unit 13 determines the range for generating the program digest based on the parameters passed from the client 20. It may be determined.

Also, in the above description of the embodiment, the data transmission unit 15 transmits the program digest to the client 20 after the program digest generation by the digest generation unit 13 is completed. May be transmitted in parallel.

In the description of the above embodiment, the program digest generation by the digest generation unit 13 is performed at the time of a request from the client 20. For example, the program digest is five minutes from the beginning of the program data. , 1
The program data cut out every 5 minutes, such as 0 minutes, 15 minutes,..., Is converted into a program digest having a length of 5 minutes in advance and stored in the data storage unit 11, and the client 20 requests the program digest. May be replaced with an operation of selecting a program digest having a length closest to the value of (request time R-program start time S + 5).

Next, in the above-described broadcasting system, the program data transmitted from the server 10 is stored in the data storage unit 11 in advance.
The details of the operation when the data is created in real time by the data creation unit 16 instead of being stored in the data creation unit 16 will be specifically described.

The data creation unit 16 comprises, for example, an existing video camera and an MPEG2 encoder.
The captured video is converted in real time into video data in the MPEG2 format. The data creating unit 16 converts the converted MPE
The video data in the G2 format is stored as program data in the data storage unit 11 and transferred to the data transmission unit 15 to transmit the program data to the requesting client 20. At this time, the server 10 and the client 2
0 operates in accordance with the processing procedure shown in FIGS. 2 to 9 described above, whereby a dynamic change of the communication means in response to an increase or decrease in the number of clients 20 requesting the program data created in real time, Of the program digest can be realized.

Also, in the above embodiment, the request processing unit 12 is provided with the type of communication means used when transmitting the program data to the client 20 and the algorithm used by the digest generation unit 13 to generate the program digest. Client 2 according to a combination of the program digest quality determined by the generation range of the program digest and the time length of the generated program digest.
A function of charging for a request from 0 may be added.

For example, when broadcasting sports broadcast program data, the program data is transmitted by broadcast during the first two hours of the program data, and no special fee is collected from the user of the client 20. After two hours of transmission of the program data, the transmission is switched to the unicast transmission, and the user who wishes to continue viewing requests the server 10 through the client 20 for the sports relay program data. The server 10 unicastly broadcasts the sports broadcast program data only to the client 20 that transmitted the request, and bills the user of the client 20 that transmitted the request, for example, 100 yen.

In the above embodiment, the request processing unit 12 manages the user information of the client 20 (for example, information on age, gender, taste, etc.) in advance, and uses the user information to execute the program. The type of communication means used when transmitting data to the client 20;
The function of determining the quality of the program digest generated by the digest generation unit 13 may be added to the request processing unit 12.

Further, in the above-described embodiment, the communication means used when located in the area B of FIG. 3 showing the criterion for selecting the communication means is broadcast. As shown, the area B may be divided into an area B1 and an area B2, and multicast may be used in the area B1 and broadcast may be used in the area B2.

FIG. 3 showing the criterion for selecting the communication means in the above embodiment is configured based on the communication band necessary for transmitting the program data and the number of clients requesting the program data. However, it may be configured to include a communication cost necessary for transmitting the program data, a program data production cost, and the like.

[0074]

As is apparent from the above description, according to the present invention, the communication means used for data transmission can be dynamically changed according to the increase or decrease in the number of clients requesting program data. There is an effect that efficient use of the communication path and reduction in cost are realized. Also, by transmitting the program digest, even if the time at which the client starts receiving the program data is later than the start time of the program data, the client receives the program data from the beginning and sets the program data reception end time to the program data. This can be the same as the end time. Further, there is an effect that the communication path required at that time is suppressed to a necessary minimum, and there is an effect that it is not necessary to prepare an auxiliary storage device in the client.

[Brief description of the drawings]

FIG. 1 is a block diagram of a broadcasting system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a processing procedure for transmitting program data while the server dynamically switches communication procedures when the number of clients increases in the present embodiment.

FIG. 3 is a diagram showing a criterion for switching a communication procedure in the present embodiment.

FIG. 4 is a diagram showing a processing procedure in which a client receives program data while dynamically switching a communication procedure in the present embodiment.

FIG. 5 is a diagram showing a processing procedure for transmitting program data while the server dynamically switches communication procedures when the number of clients is reduced in the present embodiment.

FIG. 6 is a diagram showing a transmission state of program data in the present embodiment.

FIG. 7 is a diagram showing transmission status of program data and a program digest when a client requests a program digest in the present embodiment.

FIG. 8 is a diagram showing a processing procedure in which a server transmits a program digest and program data when a client requests a program digest in the present embodiment.

FIG. 9 is a diagram showing a processing procedure in which a client receives a program digest and program data when the client requests a program digest in the present embodiment.

FIG. 10 is a diagram showing another example of a criterion for switching a communication procedure in the present embodiment.

[Explanation of symbols]

 Reference Signs List 10 server 11 data storage unit 12 request processing unit 13 digest generation unit 14 communication procedure selection unit 15 data transmission unit 16 data creation unit 20 client 21 data request unit 22 data reception unit 23 data selection unit 24 data output unit

Claims (30)

[Claims] 1. A broadcasting system in which a server and a plurality of clients are connected via a communication medium, and wherein the server transmits program data in response to a request from the client, wherein the server comprises: During the period of transmitting the program data to the client, according to the increase or decrease of the number of clients requesting the program data,
A broadcast system comprising a communication medium change control unit for dynamically changing and controlling a communication method and a communication path of the communication medium. 2. The communication medium change control means performs communication in a one-to-one communication system when the number of clients requesting the program data is smaller than a predetermined number, and in other cases, 2. The broadcast system according to claim 1, wherein the broadcast system is switched to a one-to-many communication system. 3. The broadcasting system according to claim 2, wherein said one-to-many communication system is a broadcast communication. 4. The communication system according to claim 2, wherein the one-to-one communication system is a communication using a telephone line as a communication path.
Or the broadcast system according to 3. 5. The communication medium change control means according to claim 1, wherein said communication medium change control means dynamically changes and controls a communication system and a communication path of said communication medium according to a predetermined schedule. Broadcast system as described. 6. The server according to claim 1, wherein the server includes a data storage unit that stores the program data, and a transmission unit that transmits the stored data from the data storage unit. Broadcast system. 7. The server according to claim 1, wherein said server further comprises data creating means for creating program data to be transmitted in real time, and said transmitting means is capable of transmitting data created by said data creating means. 6. The broadcasting system according to 6. 8. The broadcasting system according to claim 1, wherein said client includes means for dynamically responding to a change in a communication method or a communication path of said communication medium. 9. When the server receives a request for the program data from another client during the period of transmitting the program data, the server performs processing from the start of transmission of the program data to the reception of the request. Program data sent to
Digest generating means for generating the digest data from program data to be transmitted while transmitting the digest data of the program to the client, further comprising transmitting the digest data and the following program data. The broadcast system according to any one of claims 1 to 8, wherein: 10. The broadcasting system according to claim 9, wherein said client further includes means for receiving said digest data, and switching to receive said program data being transmitted after completion of said reception. 11. The digest generation means according to claim 9, wherein a start point of the range for generating the digest data is set not from a start point of the program data but from a time point designated by the client. 10
Broadcast system as described. 12. The broadcast system according to claim 9, wherein the client can designate an end point of the generation range of the digest data. 13. The storage means according to claim 1, wherein:
9. The apparatus according to claim 6, wherein said digest data is stored in advance, and said transmitting means reads out and transmits the digest data from said storing means in response to a request from said client. Or the broadcast system described. 14. The broadcasting system according to claim 9, wherein said server further comprises means for charging said client according to the quality of said communication medium and said digest data. 15. The server further comprising: means for collecting user information regarding the client, and determining the communication medium and the quality of the digest data used when transmitting the program data. The broadcast system according to any one of claims 9 to 14, wherein: 16. A broadcasting method in which a server and a plurality of clients are connected via a communication medium, and wherein the server transmits program data in response to a request from the client, wherein: A communication medium for dynamically changing and controlling a communication method and a communication path of the communication medium according to an increase or decrease in the number of clients requesting the program data during a period in which the program data is being transmitted to the client; A broadcast method comprising a change control step. 17. The communication medium change control step includes performing one-to-one communication when the number of clients requesting the program data is smaller than a predetermined number; otherwise, 17. The broadcasting method according to claim 16, wherein the method is switched to a one-to-many communication system. 18. The broadcasting method according to claim 17, wherein the one-to-many communication system is a broadcast communication. 19. The broadcasting method according to claim 17, wherein the one-to-one communication method is communication using a telephone line as a communication path. 20. The communication medium change control step according to claim 16, wherein a communication system and a communication path of the communication medium are dynamically changed and controlled according to a predetermined schedule. The broadcast method described. 21. The server according to claim 16, further comprising a step of storing the program data in a data storage means in advance and a step of transmitting the stored data from the data storage means. Or the broadcasting method described. 22. The server further comprising the step of: creating program data to be transmitted in real time;
22. The broadcasting method according to claim 21, wherein the transmitting step can transmit the created data. 23. The broadcasting method according to claim 16, further comprising a step of dynamically responding to a change in a communication method or a communication path of the communication medium in the client. 24. When the server receives a request for the program data from another client during the period of transmitting the program data, the server waits for the server to start transmitting the program data and receive the request. Further comprising a digest generating step of generating the digest data from the program data transmitted to the client and the program data to be transmitted while transmitting the digest data of the program to the client, wherein the digest data and the subsequent program data are generated. The broadcast method according to any one of claims 16 to 23, wherein the broadcast is transmitted. 25. The broadcasting method according to claim 24, further comprising the step of: receiving, at the client, the digest data, and after receiving the digest data, switching to receive the program data being transmitted. 26. The digest generation step according to claim 24, wherein the start point of the range for generating the digest data is not from the start point of the program data but from the time point specified by the client. 25. The broadcasting method according to 25. 27. The broadcasting method according to claim 24, wherein the end point of the generation range of the digest data can be designated by the client. 28. The method according to claim 28, wherein the storage unit stores one of the program data.
24. The digest data according to claim 21, wherein the digest data is stored in advance, and the transmitting step reads and transmits the digest data from the storage unit in response to a request from the client. Or the broadcast system described. 29. The broadcasting method according to claim 24, further comprising a step of charging the client in accordance with the quality of the communication medium and the digest data in the server. 30. The server further comprising: collecting user information on the client in the server to determine the communication medium to be used when transmitting the program data and the quality of the digest data. The broadcast method according to any one of claims 24 to 29, characterized in that: