JP5096027B2 - Content distribution system and content distribution method - Google Patents

Description

  The present invention relates to a content distribution system and a content distribution method for receiving content data from a content server through a communication network in a user terminal.

  In recent years, broadcasting using communication, such as multicast broadcasting, has become popular, and various methods have been proposed particularly for buffering methods on the receiving side in content reproduction over a network.

There is an example of shortening the reproduction start waiting time by filling a necessary de-jitter buffer at high speed by using communication at a high speed at the start of content streaming reproduction (for example, Patent Document 1). reference).
Japanese Patent Laid-Open No. 2003-143583

  However, the communication network does not always maintain the connection. For example, restart due to a link failure of a modem such as xDSL, temporary link disconnection of a wireless LAN network, interruption of data transfer due to line bandwidth congestion, and the like may occur. For this reason, there is a possibility that the broadcast may be disconnected due to the communication line being stopped. In this case, it takes several tens of seconds for the streaming to resume due to reconnection, and the viewing is interrupted during that time.

  Therefore, the present invention solves the above-described problems, and avoids content viewing being interrupted even if data transfer is interrupted on the communication network in content distribution through the communication network. It is an object of the present invention to provide a content distribution system and a content distribution method that can be performed.

In order to solve the above problems, the present invention provides a content distribution system and method comprising a content distribution server and a plurality of content reception clients that receive content distributed from the content distribution server through a network. A server for conveying content as a first content stream transferred at a rate greater than the content playback rate; and a second content stream for transferring content at a rate equivalent to the content display rate and means for conveying a provided with two types of transfer means,
The plurality of content receiving clients are:
(1) The content is received from the content distribution server at a high speed as a first content stream transferred at a rate larger than the content reproduction rate at the content receiving client, and the received first content stream is received. After temporarily accumulating in the buffer as content data , switching from the first content stream to the second content stream transferred at a rate equivalent to the content display rate while continuing to accumulate in the buffer and performing content playback from the buffer,
(2) with continuously storing contents data of a certain time in a buffer, while transferring the second content stream, the network failure is not carried out the transfer of the second content stream is generated The step of continuing the content reproduction using the content data stored in the buffer,
(3) When the failure is recovered and normal transfer becomes possible, the second content stream is resumed, and the missing portion of the content data that could not be received during the network failure is and re-stored in the buffer by the reception at high speed using the content stream,
The execution,
The second content stream is executed in a multicast mode in which data is transmitted / received in a one-to-many relationship with a plurality of communication partners. In the multicast mode, the content reception client receives a decryption key from the content distribution server and To acquire a terminal list in which other content receiving clients holding a part or all of the content in the buffer are described, select an arbitrary content receiving client from the terminal list, make a distribution request, and select the other content A part or all of the content related to the distribution request is received from the reception client or the content distribution server, and the content reception client reconfigures the content and reproduces the content using the decryption key.

In the above invention, it is preferable that the first and second content streams are composed of streaming video data or streaming audio data.

In the above invention, when controlling the start and end of conveyance by the first content stream, the buffer is filled prior to the control processing by the control means, or a predetermined amount of channel content data is stored in the buffer. It is preferable to confirm that is accumulated .

Furthermore, in the above invention, the first content stream is executed in a unicast mode in which data is transmitted and received in a one-to-one relationship with a single communication partner, and each content receiving client can execute in the terminal list. The communication mode is described, and the content reception client detects the communication mode executable by the content distribution server or other content reception client based on the terminal list when the distribution request is made, and determines the communication partner according to the detected communication mode. It is preferable that a content server or other user terminal to be selected is selected and a distribution request designating a communication mode is transmitted to the selected communication partner .

Further, in the above invention, the second content stream, when transported in the multicast mode, after each client regeneration completion even to keep the streaming content constant time period, this first content It is preferable to further include means for enabling high-speed downloading using a stream.

  According to the present invention as described above, two types of methods for conveying the content channel signal to the distribution apparatus are prepared, and the first method conveys the content stream at a rate larger than the streaming content playback rate. The second method carries the content stream at the display rate of the content stream.

  Then, a buffer is prepared in the reception / playback device, and the content stream is cached in the buffer during content streaming playback. Thus, when the network is temporarily disconnected, the cached content stream is used. So that playback is not interrupted. Thereafter, when the network is restored, the cache is stored in the buffer while performing reproduction by performing the download using the first transport method described above.

  In the above invention, the user terminal is a content distribution system that receives the distribution of content data from the content server through the communication network, and is provided in the user terminal or the content server in a one-to-one relationship with a single communication partner. Communication capable of executing either unicast mode for transmitting / receiving data, multicast mode for transmitting / receiving data in a one-to-many relationship with multiple communication partners, broadcast mode, anycast mode, or both modes And a buffer unit that is provided in the user terminal and receives content data from the content server or other user terminals and temporarily stores the data, and a communication unit of the content server or other user terminal that is provided in the user terminal. Detect and detect possible modes Depending on the mode, a content server or other user terminal to be a communication partner is selected, a distribution request unit that requests distribution of content to the selected communication partner, a user terminal, a storage capacity in the buffer unit, A monitoring unit that monitors the connection status to the communication network, and a mode switching that switches between modes based on the storage capacity of the buffer unit provided in the user terminal and detected by the monitoring unit, and the connection status to the network And an output unit for outputting the content data stored in the buffer unit.

  In such cases, while avoiding the degradation of content distribution services due to changes in communication conditions, while enjoying the benefits of both communication load distribution in multicast mode and high-speed communication in response to individual requests in unicast Can do.

  In the above invention, the content server issues an encryption key that permits output of the content data related to distribution, the content data can be output after being decrypted by the encryption key, and the output unit can view the content data when viewing it. Content related to viewing is obtained by acquiring a part or all of the content data from the content server or another user terminal, acquiring an encryption key corresponding to the acquired content data from the content server, and decrypting it with the acquired encryption key. It is preferable to output data. In this case, since network content is distributed between distributed user terminals, it is possible to reduce the burden on the content distribution server, avoid the concentration of communication, and reduce the communication load. be able to.

  In the above invention, when the mode switching unit resumes receiving the content data by multicast when it is detected that the connection to the network has been disconnected and reconnected, the content data becomes FEC (Forward Error Correction). ) Etc., if there is content / data loss that cannot be repaired, the content / data missing portion that could not be received by multicast during network disconnection is received at high speed using unicast. By doing so, it is possible to quickly recover the loss of the content data and more reliably avoid the deterioration of the content distribution service.

In the above invention, the unicast mode in which data is transmitted / received in a one-to-one relationship with a single communication partner, or the multicast mode, broadcast mode, and anycast mode in which data is transmitted / received in a one-to-many relationship with a plurality of communication partners. A content distribution method that uses a user terminal or a content server capable of executing any one of these modes, or both of these modes, and receives content data from the content server via a communication network in the user terminal, In the buffer unit provided in the terminal, receiving the content data from the content server or other user terminal, temporarily storing (1),
In the distribution request unit provided in the user terminal, the mode that can be executed by the content server or other user terminal is detected, and the content server or other user terminal that is the communication partner is selected and selected according to the detected mode. (2) requesting the content delivery to the other communication partner,
In the monitoring unit provided in the user terminal, monitoring the storage capacity in the buffer unit and the connection state to the communication network (3),
In the mode switching unit provided in the user terminal, step (4) of switching the mode based on the storage capacity of the buffer unit, which is the monitoring result of the monitoring unit, and the connection state to the network;
A step (5) of outputting the content data stored in the buffer unit by the output unit.

  In the above invention, in step (1), the content server issues an encryption key that permits output of the content data related to distribution, and the content data can be decrypted and output by the encryption key, and output in step (5). When outputting the content data, the part acquires part or all of the content data related to the output from the content server or another user terminal, and acquires the encryption key corresponding to the acquired content data from the content server. It is preferable to decrypt the content with the encryption key and output the content data.

  In the above invention, in step (4), when the mode switching unit detects that the storage capacity of the buffer unit has decreased below a certain value in the monitoring unit, and that the connection to the network has been disconnected and reconnected, It is preferable to select a content server or another user terminal as a communication partner based on the detection result in the mode detection unit, and perform the mode switching.

  As described above, according to the present invention, even when a line disconnection occurs due to a network failure or the like during viewing of a streaming broadcast on the Internet, it is possible to view without interruption due to reception by high-speed communication after buffering and restoration. It becomes possible.

  In addition, according to the present invention, by appropriately setting the buffer size based on the restart time of the communication device / line, the delay from the real time can be minimized, load distribution by multicast, unicast It is possible to enjoy the merits of both parties to meet individual requirements in

  Hereinafter, an embodiment of a content viewing system according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing an overall configuration of a content viewing system according to the present embodiment.

  As shown in the figure, in the present embodiment, the content distribution server 2 is connected to the Internet 8, and each reception client 1a to 1d, which is a reception / playback device having a buffer, is connected via a router 83. Internet 8 can be connected.

  In the present embodiment, the content distribution server 2 has two types of unicast (first content stream) and multicast (second content stream) as methods for carrying content channel signals. . At this time, in unicast, the content stream is transported at a rate larger than the streaming content playback rate, and in multicast, the content stream is transported at the display rate of the content stream.

  As shown in FIGS. 2 to 4, the receiving clients 1a to 1d perform high-speed download by unicast at the start of reproduction (reproduction request or channel change) (S101 and S102). At this time, it is confirmed whether or not the caching to the buffer has been performed for a predetermined amount (here, about 5 seconds) (S103), and loop processing is performed until the predetermined amount of buffer is accumulated ("N" in S103) "). Examples of the technology related to switching between unicast and multicast at the start of playback include, for example, US Pat. No. 6,792,449 (“Startup methods and using for streaming content”, applicant: Microsoft Corporation) It is possible to employ a technique according to Japanese Patent No. 188915 (“Method and apparatus for changing received streaming content channel”, Japanese Patent Application No. 2002-263472, applicant: Thomson Licensing SA).

  Next, the content stream is cached in the buffer, and when a predetermined amount is accumulated in the buffer ("Y" in S103), switching from unicast to multicast (S104), the content is received by multicast. While continuing to accumulate in the buffer, the stream is reproduced from the beginning of the buffer (S105).

  In particular, when communication via Internet 8 etc. is temporarily interrupted when receiving and playing back via multicast download (S106), sufficient data is stored in the buffer to the extent that the missing part can be played back. If there is enough time to play back the missing part (S107), and if there is enough data storage and time to play back the missing part ("Y" in S107), the receiver side will buffer The network stream is awaited to be restored by a loop process while the reproduction is not interrupted by using the cached content stream (“N” in S110). On the other hand, after the communication disconnection occurs, in step S107, when there is not enough data accumulation in the buffer and there is no time until reproduction of the missing portion ("N" in S107), reproduction stop processing is performed (S109), Wait for network recovery by loop processing ("N" in S110).

  After that, when the Internet 8 is restored (“Y” in S110), if the playback stop process in step S109 is not performed and the playback is continued (“N” in S111), the multicast reception is resumed. At the same time, the stream content is downloaded at high speed using unicast for the loss due to the communication disconnection (S112 and S113). As a result, both unicast and multicast streams are reproduced while being received, and the cache is stored in the buffer at high speed (S114). Note that when Internet 8 was restored, the playback point of the missing part had already been reached, and if content playback was stopped by step S109 ("Y" in step S111), high-speed unicast was used. Return to the playback start flow.

  At the time of reception / reproduction in step S114, it is determined whether or not all of the missing portions have been downloaded by unicast (S115), and reception of both the unicast and multicast is continued until all of the missing portions are downloaded (S115). "N"), if all of the missing data has been downloaded ("Y" in S115), it is returned to multicast reception again (S104), and the normal playback flow after step S105 is taken.

(User terminal configuration)
The user terminal 1 (1a to 1d) is an arithmetic processing device including a CPU. In this embodiment, the user terminal 1 (1a to 1d) includes a communication function, and also has a function of receiving streaming distribution and executing an application for viewing. The user terminal 1 (1a to 1d) can be realized by a general-purpose computer such as a personal computer or a dedicated device with special functions, and includes a mobile computer, a PDA (Personal Digital Assistance), and a mobile phone. .

  In the present embodiment, during communication in the multicast mode, the user terminal 1 transmits a viewing request to the distribution server 2 (or another distribution management server) and reproduces the net content related to the viewing request. And receiving the decryption key D3 to be transmitted from the distribution server and the terminal list D2 of the other user terminals holding part or all of the net content related to the request, the content distribution server 2 or other user terminals 1a to You may make it acquire from 1d. In this case, the user terminal 1 selects an arbitrary user terminal as the partner terminal device from the terminal list D2, makes a distribution request, and requests from the selected partner terminal (here, the user terminal 1b) and the content distribution server 2. The network content D4 is received in part or in whole, and the user terminal 1 reconstructs the network content D4, and reproduces and views it with the decryption key D3.

  In order to perform reception in such a multicast mode, a configuration as shown in FIG. 5 can be adopted. FIG. 5 is a block diagram showing an internal configuration of the user terminal 1 (1a to 1d).

  The user terminal 1 (1a to 1d) includes a communication interface 11, a communication mode control unit 12, a cache unit 17, a content reproduction unit 13, an output signal generation unit 14, and an output as modules related to streaming reception and reproduction. An interface 20, a display unit 21, and a monitoring unit 18 are provided.

  The communication interface 11 is a module that transmits and receives data as packets through the IP network 8. Via the communication interface 11, the network content D4, the terminal list D2, and the like are received, and the distribution request D1 is transmitted to the content distribution server. Sent to 2.

  The cache unit 17 is a buffer device that temporarily stores and holds the network content received from the IP network 8 and played back by the content playback unit 13. In the present embodiment, prior to content playback by the media viewing application 22, the content is downloaded and stored in advance. The data stored in the cache unit 17 can be shared with other user terminals by an OLM (OverLay Multicast) peer-to-peer network system, and there is a distribution request from another user terminal Is transmitted to the other user terminal.

  The communication mode control unit 12 determines the communication mode (multicast mode or unicast mode) of the communication partner based on the storage capacity of the cache unit 17 detected by the monitoring unit 18 and the network connection state in the communication interface 11. This is the module that performs the selection. That is, the communication mode control unit 12 includes a unicast communication unit 12a that executes a unicast mode that performs data transmission / reception in a one-to-one relationship with a single communication partner, and data transmission / reception in a one-to-many relationship with a plurality of communication partners. A multicast communication unit 12b for executing a multicast mode for performing The communication mode control unit 12 selects either one or both of these communication units 12a or 12b based on a control signal from the monitoring unit 18, and connects to the communication interface 11, thereby the unicast mode. Or any of the multicast modes, or both of these modes.

  Further, the user terminal 1 includes a monitoring unit 18 and a distribution request unit 19 as modules relating to a distribution request.

  The monitoring unit 18 is a module that detects and monitors the storage capacity in the cache unit 17 and the connection state to the IP network 8 by the communication interface 11, and controls a control signal that instructs mode switching based on the monitoring result. Input to the unit 12 and the distribution request unit 19.

  The distribution request unit 19 is a module that transmits a distribution request for playing net contents in accordance with a user operation (media viewing application activation or channel change). In this embodiment, the distribution request includes a distribution request for the decryption key D3 and a distribution request for net content (main stream / banner data) D4. These distribution requests are transmitted to the content distribution server 2.

  In addition, the distribution request unit 19 detects a communication mode that can be executed by the content distribution server 2 or another user terminal (for example, 1a or 1b), and the content server or other communication partner that is a communication partner according to the detected communication mode A user terminal is selected, and a content distribution request specifying a communication mode is transmitted to the selected communication partner. Note that the selection of the communication partner according to the communication mode is performed based on the executable communication mode of each terminal described in the terminal list D2.

  The content playback unit 13 is a module that plays back Web pages, moving image data, and audio data, and outputs them from the media viewing application 22 on the display unit 21, the speaker 20a, and the like. The content reproduction unit 13 acquires the decryption key D3 corresponding to the net content acquired in response to the distribution request D1 from the content distribution server 2, and decrypts the net content cached in the cache unit 17 with the decryption key D3. And play.

  The content playback unit 13 may be provided with a function of inserting banner data on a Web page or inserting a video clip for advertisement into a main stream of net content. Such a video clip insertion function includes, for example, an insertion position detection process for analyzing a main stream and detecting a position where additional information such as CM clip data is inserted, and a CM clip at a position detected by the detection process. Is inserted, and the network content is played back while inserting the CM clip into the main stream.

  Furthermore, the content playback unit 13 may have a function of recording the playback history and playback stop position of the played net content as user trend data, and changing the next playback start position according to this recording. Specifically, the net content (main stream, CM clip) that the user has already viewed, the file name of the banner data, and the playback stop position are stored as a playback history (user trend data) in a storage device such as a hard disk, At the time of reproduction, the reproduction history is referred to. If the content has already been viewed, the content is skipped, or if the viewing is stopped in the middle, the reproduction is continued from there.

  The output signal generation unit 14 converts the net content that can be played back by the content playback unit 13 into a video signal and an audio signal, and converts the net content to a video signal such as the media viewing application 22 displayed on the display unit 21. This is a module that synthesizes video signals and generates a signal that can be output by the display unit 21 or the speaker 20a.

  The output interface 20 is a module that outputs video and audio output signals from the display unit 21 and the speaker 20a, respectively. The display unit 21 is a display device such as a liquid crystal display, for example, and synthesizes and displays a plurality of screens such as the media viewing application 22.

  In addition, the user terminal 1 includes an application execution unit 15 and an operation device interface 16 as modules related to the user interface.

  The application execution unit 15 is a module that executes applications such as a general OS, browser software, and the media viewing application 22, and is usually realized by a CPU or the like. The application execution unit 15 can receive a chat service related to sports watching by executing chat software linked with the media viewing application 22, for example.

  The operation device interface 16 is a module to which operation devices such as a mouse and a keyboard are connected, and the operation signals are input / output. By using the application execution unit 15 and the operation device, the user can input a keyword for searching for content or input a character string that is an evaluation of the net content after viewing.

(Action / Effect)
By using such a system and method according to this embodiment, it is possible to enjoy both of the merits of reducing the load by multicast and responding to individual requests in unicast. Further, in order to reduce the load on the distribution device side, it is possible to perform a process of disconnecting the connection with the receiving device that continues to receive by unicast after a certain time.

  In the above embodiment, the buffer size of the receiving device may be specified based on the restart time. For example, bit rate × restart time × (1 + α) is calculated. As a method for estimating the restart time, a method of preparing an API that returns an estimate to the communication device, or a method designated by the user or inferring from the communication speed can be considered. At this time, the client may determine how many seconds later the content is received from the timing of receiving the content on the network, and the playback may be performed as such.

It is a conceptual diagram which shows the whole structure of the system which concerns on embodiment. It is a flowchart figure in the content viewing-and-listening system concerning an embodiment. It is a conceptual diagram which shows the response | compatibility at the time of a link break in the content viewing-and-listening method concerning embodiment. It is a conceptual diagram which shows the response | compatibility at the time of a link break in the content viewing-and-listening method concerning embodiment. It is a block diagram which shows the example of an internal structure of the user terminal 1 (1a-1d) which concerns on embodiment.

Explanation of symbols

D1 ... Delivery request
D2 ... Device list
D3 ... Decryption key
D4 ... Net content
1 (1a to 1d): User terminal (receiving client)
2. Content delivery server
11… Communication interface
12 ... Communication mode controller
12a… Unicast Communication Department
12b: Multicast communication part
13… Content playback section
14 ... Output signal generator
15 ... Application execution part
16 ... Operation device interface
17 ... Cache part
18 ... Monitoring section
19 ... Delivery request part
20… Output interface
20a… Speaker
21 ... Display section
22… Media viewing application
83 ... Router

Claims (14)

A content distribution system comprising a content distribution server and a plurality of content reception clients that receive content distributed from the content distribution server through a network ,
Said content distribution server, transferring the content, means for conveying a first content stream to be transferred at a greater rate than the reproduction rate of the content, the content, the display rate equivalent to the rate of the content and means for transferring the second content stream, comprising two transfer means,
The plurality of content receiving clients are:
A buffer for temporarily storing the received first or second content stream as content data;
Performs reception at high speed as the first content stream, then the received first content stream accumulated in the buffer, the switching to the second content stream from the first content stream while continuing accumulation of the buffer, and a content playback unit performing playback of content from the buffer,
Each with
The second content stream is executed in a multicast mode in which data is transmitted and received in a one-to-many relationship with a plurality of communication partners, and in the multicast mode, the content receiving client receives a decryption key from the content distribution server. In addition, a terminal list in which another content receiving client that holds part or all of the content in a buffer is obtained is obtained, and an arbitrary content receiving client is selected from the terminal list and a distribution request is made. Receiving a part or all of the content related to the distribution request from the selected other content receiving client or the content distribution server, reconstructing the content in the content receiving client, and reproducing the content with the decryption key. And
The content reproduction unit is configured to continuously storing the content data for a predetermined time in the buffer, the during the transfer of the second content stream, the failure occurs in the network the second content · when the stream transfer is no longer the case, to continue the content reproduction using the stored content data in the buffer,
The failure to recover, when it becomes possible to normal forwarding, the conjunction resume second content stream, the defect content of the content data has not been received during a network failure, the first content distribution system, characterized by re-accumulated in the buffer by the received at high speed by using the content stream. The content distribution system according to claim 1, wherein the first and second content streams are composed of streaming video data. 2. The content distribution system according to claim 1, wherein the first and second content streams are composed of streaming audio data. Control means for controlling the start and end of transport by the first content stream;
Content delivery system according to claim 1, further comprising a means to ensure that the buffer is filled before the control processing by the control means. Control means for controlling the start and end of transport by the first content stream;
Content delivery system according to claim 1, further comprising a means to verify that the content data of a predetermined amount is accumulated in the buffer prior to the control by the control means. The first content stream is executed in a unicast mode in which data is transmitted and received in a one-to-one relationship with a single communication partner,
In the terminal list, communication modes that can be executed by each content receiving client are described,
In response to the distribution request, the content receiving client detects a communication mode executable by the content distribution server or other content receiving client based on the terminal list, and the content serving as a communication partner according to the detected communication mode The content distribution system according to claim 1 , wherein a server or another user terminal is selected, and the distribution request designating a communication mode is transmitted to the selected communication partner . Wherein the second content stream, when transported in the multicast mode, after each client regeneration completion even to keep the streaming content constant time period, which by using the first content stream content delivery system according to claim 1, characterized by further comprising means for enabling downloading at a high speed. A content distribution method for receiving content distributed from a content distribution server through a network by a content receiving client,
The content is received from the content distribution server at a high speed as a first content stream transferred at a rate larger than the playback rate of the content at the content receiving client, and the received first content stream, after storing in the buffer as a temporary content data, from the first content stream, switching to the second content stream is transferred display rate equivalent to the rate of the content to the buffer while continuing accumulation and performing content playback from the buffer,
The content data for a predetermined time while continuously accumulated in the buffer, the during the transfer of the second content stream, the Network failures of the second content stream transfer line when we run out, the steps to continue the content reproduction using the stored content data in the buffer,
The failure to recover, when it becomes possible to normal forwarding, the conjunction resume second content stream, the defect content of the content data has not been received during a network failure, the first and re-stored in the buffer by the reception at high speed using the content stream,
The execution,
The second content stream is executed in a multicast mode in which data is transmitted and received in a one-to-many relationship with a plurality of communication partners, and in the multicast mode, the content receiving client receives a decryption key from the content distribution server. In addition, a terminal list in which another content receiving client that holds part or all of the content in a buffer is obtained is obtained, and an arbitrary content receiving client is selected from the terminal list and a distribution request is made. Receiving a part or all of the content related to the distribution request from the selected other content receiving client or the content distribution server, reconstructing the content in the content receiving client, and reproducing the content with the decryption key. JP the <br/> that Content distribution method to. 9. The content distribution method according to claim 8, wherein the first and second content streams are composed of streaming video data. 9. The content distribution method according to claim 8, wherein the first and second content streams are composed of streaming audio data. Controlling the start and end of transport by the first content stream by a control means;
Content distribution method according to claim 8, further comprising a step of confirming that the buffer prior to the control process are satisfied by the control means. Controlling the start and end of transport by the first content stream by a control means;
Content distribution method according to claim 8, further comprising a step of confirming that the content data of a predetermined amount in the buffer prior to the control processing by the control means is accumulated. The first content stream is executed in a unicast mode in which data is transmitted and received in a one-to-one relationship with a single communication partner,
In the terminal list, communication modes that can be executed by each content receiving client are described,
In response to the distribution request, the content receiving client detects a communication mode executable by the content distribution server or other content receiving client based on the terminal list, and the content serving as a communication partner according to the detected communication mode 9. The content distribution method according to claim 8 , wherein a server or another user terminal is selected, and the distribution request designating a communication mode is transmitted to the selected communication partner . Wherein the second content stream, when transported in the multicast mode, after each client regeneration completion even to keep the streaming content constant time period, which by using the first content stream content distribution method according to claim 8, further comprising the step of enabling downloading at a high speed.