WO2012113212A1

WO2012113212A1 - Method and system for sending multicast join request in advance during fast channel change

Info

Publication number: WO2012113212A1
Application number: PCT/CN2011/078939
Authority: WO
Inventors: 朱晓斌
Original assignee: 中兴通讯股份有限公司
Priority date: 2011-02-24
Filing date: 2011-08-25
Publication date: 2012-08-30
Also published as: CN102651823A

Abstract

Disclosed are a method and system for sending a multicast join request in advance during fast channel change, for overcoming the defect that the processing capability of the fast channel change server is wasted as the unicast/multicast change mechanism in the existing fast channel change technology does not take into account the processing time overhead of the data device in processing a multicast join request. The time for pre-sending the multicast join request during the fast channel change process is taken into account, thus shortening the time for the server to send unicast code streams, saving the processing capability, and reducing the deployment cost.

Description

Method and system for pre-sending a multicast request in fast channel switching

The present invention relates to the field of communications, and in particular, to a method and system for pre-sending a multicast request during fast channel switching. Background technique

Digital video coding technology generally uses interframe coding to increase the compression ratio, which causes the decoder to receive an I frame (Intra Frame) to begin displaying the video correctly. In IPTV, multicast technology is preferred to transmit live streams, and all terminals collectively receive the same stream. When the terminal performs channel switching, the time at which it starts to receive the live stream is random. It usually takes a while to receive the I frame and display the video picture, which seriously affects the channel switching speed of the IPTV.

There are a variety of Fast Channel Change (FCC) schemes for improving the channel switching speed of IPTV. The current mainstream solution is to use the Fast Channel Change Server (FCC Server or FCC Server) to channel code. The stream is buffered. When the channel is switched, the unicast mode is used to quickly send the code stream starting with the I frame. After receiving the video, the terminal quickly decodes and displays the video picture. Then the FCC Server stops sending the unicast code stream, and the terminal starts to use the multicast stream. Decode.

In the above solution, the timing at which the FCC Server stops transmitting the unicast code stream and the terminal starts to use the multicast code stream decoding (hereinafter referred to as "unicast and multicast switching") is very critical, and the premature handover may not receive enough. Unicast data cannot be connected to multicast data, causing damage to the video picture played by the terminal to affect the user experience. However, if the switch is too late, there is no need to worry about the connection between unicast and multicast data, but the FCC Server needs to send a long time unicast. The code stream invisibly wastes the processing power of the FCC Server and increases the deployment cost. Subsequent sections of this article will support terminals that support fast channel switching. Called Fast Channel Change Client (FCC Client or FCC Client), it is simply referred to as "client" without causing confusion. Correspondingly, the fast channel switching server can be simply referred to as "server". ".

At present, the unicast code stream can be sent by the server at a higher speed. When the unicast code stream and the multicast code stream are synchronized (ie, the connection is made), the client is notified to request to join the multicast group, and the client receives the multicast stream. The server is then notified to stop sending the unicast stream. In an actual IPTV bearer network, the data device needs to process a request to join the multicast group for a certain period of time, which means that there is a delay interval between the client sending a multicast request and receiving the multicast stream. Short time

300ms, the length is 700ms or even longer, and the above switching mechanism does not consider this time overhead. After the unicast and multicast streams are synchronized, the server continues to send hundreds of milliseconds of unicast stream until the client actually receives it. Multicast stream, which obviously wastes service capabilities.

In the IETF (Internet Engineering Task Force) draft draft-ietf-avt-rapid-acquisition-for-rtp-17, the server can calculate the earliest time when the client requests to join the multicast group and deliver it to the client. The client can refer to this data to determine the time to request to join the multicast group. How to get the data of "the earliest time to request to join the multicast group" and how the client uses this data, the document does not give a substantive explanation. Summary of the invention

In view of this, the main object of the present invention is to provide a method and system for pre-sending a multicast request during fast channel switching, so as to shorten the time for the server to send a unicast stream and save processing power. In order to achieve the above object, the technical solution of the present invention is achieved as follows:

The method for pre-sending the multicast request in the fast channel switching includes: collecting the processing time cost of the data processing device to process the multicast request, calculating the synchronization time between the unicast and the multicast code stream, and calculating the client to send the multicast in advance. The moment of the request.

The collecting method is at least one of the following: and when obtaining a plurality of different values, using a statistical method including taking a minimum value or an average value to obtain a single value as a multicast request Processing delay:

Real-time statistics; when the client is working normally, calculate the time interval between itself sending a multicast request and receiving a multicast stream;

Experimental analysis; experiment with a network host supporting multicast function, measuring the time interval between sending a multicast request and receiving a multicast stream;

Empirical estimation; comprehensively including historical data, experimental results, equipment model, network architecture, and reasonable estimates;

The method for calculating the time for synchronizing the unicast with the multicast code stream is:

TSync=PDif/(RUc-RMc) Formula 1

In the above formula, TSync is the estimated time of synchronization between the unicast and the multicast code stream, and PDif is the amount of data separated between the unicast media packet sent by the server and the received multicast media packet at a certain time, RUc is The average bit rate of the unicast code stream sent by the server, RMc is the average code rate of the multicast code stream; dividing the divisor and the dividend on the left side of Equation 1 by RMc, the following equivalent formula is obtained:

TSync=TDif/( a Uc-1) Equation 2

In the above formula, TSync is the estimated time of synchronization between the unicast and multicast streams, and TDif is the time interval between when a media packet is received and transmitted, and a Uc is the unicast rate relative to the multicast rate. Ratio

The method for calculating the time when the computing client sends the multicast request in advance is:

TReqMc=TSync-TMcDly Equation 3

In the above formula, TReqMc is the relative time for the client to pre-send the multicast request, TSync is the unicast and multicast code synchronization time, and TMcDly is the multicast request processing delay.

The method for pre-sending a multicast request during fast channel switching includes: notifying a multicast request processing delay to a server, the server calculating a time when the client sends a multicast request in advance, and the server controlling the client to issue a join multicast request in advance .

The notification method is: the client saves the multicast request processing delay value, and communicates The link is sent to the server; the multicast request processing delay is used as the configuration parameter of the server; and the method for calculating the time for the client to send the multicast request in advance is:

TReqMc=TSync-TMcDly Equation 3

In the above formula, TReqMc is the relative time for the client to pre-send the multicast request, TSync is the unicast and multicast code synchronization time, and TMcDly is the multicast request processing delay;

The method for the server control client to pre-issue the join multicast request is:

The server notifies the calculated time of the pre-joining the multicast group to the client through the communication link, and the client sends a multicast request at a predetermined time; or

The server notifies the client when the time when the multicast group is added in advance, and the client sends a multicast request immediately after receiving the notification.

The method of pre-sending the multicast request in the fast channel switching includes: notifying the multicast request processing delay to the client, and the server calculates the time for the unicast to synchronize with the multicast stream, and the client sends the multicast request in advance.

In the process of notifying the multicast request processing delay to the client, the client directly saves the result; or, the multicast request processing delay is used as a configuration parameter of the client;

The method for the server to calculate the time for synchronizing the unicast with the multicast code stream is:

TSync=PDif/(RUc-RMc) Formula 1

In the above formula, TSync is the estimated time of synchronization between the unicast and the multicast code stream, and PDif is the amount of data separated between the unicast media packet sent by the server and the received multicast media packet, and the RUc is the server. The average code rate of the unicast code stream is sent, RMc is the average code rate of the multicast code stream; dividing the divisor and the dividend on the left side of Equation 1 by RMc, the following equivalent formula is obtained:

TSync=TDif/( a Uc-1) Equation 2

In the above formula, TSync is the estimated time of synchronization between the unicast and multicast streams, TDif is the time interval between when the media packet is received and transmitted, and a Uc is the ratio of the unicast rate to the multicast rate. ; The method for the client to send a multicast request in advance is:

The server sends the calculation result of the unicast and multicast code synchronization time to the client through the communication link; the client calculates the time for sending the multicast request in advance, and sends the join group when the time when the multicast request is sent in advance. Broadcast request.

a system for transmitting a multicast request in advance, including a collecting unit and a calculating unit, in a fast channel switching;

The collecting unit is configured to collect a processing time cost of the data device to process the multicast request, and the calculating unit is configured to calculate a time for synchronizing the unicast and the multicast code stream, and calculate a time when the client sends the multicast request in advance. .

When the collecting unit performs the collecting, the collecting method used is at least one of the following; and when a plurality of different values are obtained, a single value is obtained by using a statistical method including taking a minimum value or an average value, As a multicast request processing delay:

Real-time statistics; when the client works normally, calculate the time interval between the client sending a multicast request and receiving a multicast stream each time;

The calculating unit is configured to: when calculating the time at which the unicast and the multicast code stream are synchronized:

TSync=PDif/(RUc-RMc) Formula 1

TSync=TDif/( a Uc-1) Equation 2 In the above formula, TSync is the estimated time of synchronization between the unicast and multicast streams, TDif is the time interval between when the media packet is received and transmitted, and a Uc is the ratio of the unicast rate to the multicast rate. ;

The calculating unit is configured to: when calculating a time when the client sends a multicast request in advance:

TReqMc=TSync-TMcDly Equation 3

a system for transmitting a multicast request, including a notification unit, a server, and a client, in a fast channel switching;

The notification unit is configured to notify the server of the multicast request processing delay;

The server is configured to calculate a time when the client sends the multicast request in advance, and the control client sends the join multicast request in advance.

When the notification unit performs the notification, it is used to: trigger the client to save the multicast request processing delay value, and send it to the server through the communication link; and use the multicast request processing delay as the configuration parameter of the server;

The server calculates the time when the client sends the multicast request in advance, and is used for: TReqMc=TSync-TMcDly Formula 3

When the server control client sends a multicast request in advance, it is used to:

The time when the calculated pre-joining into the multicast group is notified to the client through the communication link, and the triggering client sends a multicast request at a predetermined time; or

The client is notified when the time when the multicast group is added in advance, and the triggering client sends a join multicast request immediately after receiving the notification.

Pre-sending a system for joining a multicast request, including a notification unit, and a service, during fast channel switching Server, client; among them,

The notification unit is configured to notify the client of the multicast request processing delay;

The server is configured to calculate a time for synchronizing the unicast and the multicast code stream;

The client is configured to send a join multicast request in advance.

The notification unit notifies the client of the multicast request processing delay, and the client directly saves the result; or the multicast request processing delay is used as a configuration parameter of the client; the server calculates the unicast and multicast When the code stream is synchronized, it is used to:

TSync=PDif/(RUc-RMc) Formula 1

TSync=TDif/( a Uc-1) Equation 2

In the above formula, TSync is the estimated time of synchronization between the unicast and multicast streams, TDif is the time interval between when the media packet is received and transmitted, and a Uc is the ratio of the unicast rate to the multicast rate. ;

When the client sends a multicast request in advance, it is used to:

After the server sends the unicast and multicast code synchronization time calculation result to the client through the communication link, it calculates the time for sending the multicast request in advance, and sends the join group when the time when the multicast request is sent in advance. Broadcast request.

It can be seen that the method and the system of the present invention overcome the shortcomings of the existing unicast and multicast switching mechanism in the fast channel switching technology, that the processing time overhead of the data device processing the multicast request is not considered, and the fast channel switching server wastes the processing capability. The time for joining the multicast request is pre-sent during the fast switching process of the channel, thereby shortening the time for the server to send the unicast code stream, saving processing power and low deployment cost. DRAWINGS

1 is a schematic diagram of a method for calculating a time for pre-sending a multicast request according to the present invention; FIG. 1 is a schematic flowchart of calculating a time for pre-sending a multicast request in a fast channel switching process according to the present invention;

FIG. 3 is a schematic flowchart of pre-sending a multicast request in a fast channel switching process according to an embodiment of the present invention; FIG.

4 is a schematic flow chart of pre-sending a multicast request in a fast channel switching process according to another embodiment of the present invention;

FIG. 5 is a schematic diagram of a deployment model of two embodiments provided by the present invention; FIG.

6 is a flowchart of a fast channel switching process according to an embodiment of the present invention;

FIG. Ί is a flowchart of a fast channel switching process according to Embodiment 2 of the present invention. detailed description

To overcome the shortcomings of the processing time cost of the data device processing the multicast request, the fast channel switching server wastes the processing capability, which may be considered in the fast switching process of the channel. The time to join the multicast request is sent, which shortens the time for the server to send the unicast stream, saves processing power, and lowers the deployment cost.

The method for calculating the time for sending a multicast request in advance during the fast switching process of the channel is as follows:

The first step is to collect the processing time overhead of the data device to process the multicast request (hereinafter referred to as "multicast request processing delay"), and there are various collection methods, including but not limited to:

Empirical estimation; comprehensive historical data, experimental results, equipment model, network architecture, etc. Prime, make a reasonable estimate.

The above methods may be used alone or in combination. If a plurality of different values are obtained, a statistical method such as taking the minimum value or the average value is used to obtain a single value as the multicast processing delay.

The second step is to calculate the synchronization time between the unicast and the multicast code stream;

The server continuously receives the multicast stream and caches it. When the client requests the fast channel switching service from the server, the server will take the media packet starting with the I frame from the buffer and send it to the client in unicast mode.

The time for synchronizing unicast and multicast streams is calculated using the following formula:

TSync=PDif/(RUc-RMc) Formula 1

In the above formula, TSync is the estimated time of synchronization between the unicast and multicast streams, and PDif is the amount of data between the unicast media packets sent by the server and the received multicast media packets at a certain time, RUc is The average bit rate of the unicast code stream sent by the server, and RMc is the average bit rate of the multicast stream.

Dividing the divisor and the dividend on the left side of Equation 1 by RMc gives the following equivalent formula:

TSync=TDif/( a Uc-1) Equation 2

In the above formula, TSync is the estimated time of synchronization between the unicast and multicast streams, and TDif is the time interval between when a media packet is received and transmitted, and a Uc is the unicast rate relative to the multicast rate. The ratio, ie:

a Uc=RUc RMc

The result of this step is a relative time: For Equation 1, the timing start point is the time at which the calculation is performed; for Equation 2, the timing start point is the time at which the media packet selected for calculation is sent.

The third step is to calculate a time when the client sends a multicast request in advance;

Calculate using the following formula:

TReqMc=TSync-TMcDly Equation 3 In the above formula, TReqMc is the relative time for the client to pre-send the multicast request, TSync is the unicast and multicast stream synchronization time, and TMcDly is the multicast request processing delay.

The calculation of steps 2 and 3 above can be done by the server, client or other device, as long as the parameters required for calculation are passed to the corresponding device. Equation 1, Equation 2, and Equation 3 can also be expressed in absolute time form, and there may be other equivalent forms.

The first method for pre-sending a multicast request in the fast channel switching process of the present invention is as follows:

The first step is to notify the server of the multicast request processing delay. There are several ways to choose from, including but not limited to:

The client saves the multicast request processing delay value and sends it to the server through the communication link; the multicast request processing delay is used as a configuration parameter of the server.

In the second step, the server calculates the time when the client sends the multicast request in advance, and the specific method is given in the corresponding part of the previous section.

The third step, the server control client pre-issued to join the multicast request, there are several different ways, including but not limited to:

The two methods of pre-sending a multicast request in the fast channel switching process of the present invention are as follows:

The first step is to notify the client of the multicast request processing delay. There are several ways to choose from, including but not limited to:

The client directly saves the result, which is suitable for obtaining the multicast request processing delay by using real-time statistical methods; The multicast request processing delay is used as a configuration parameter of the client, which is suitable for obtaining the multicast request processing delay by using experimental analysis or empirical estimation.

In the second step, the server calculates the synchronization time between the unicast and the multicast code stream. For the specific process, refer to the second step of the method for calculating the time when the client sends the multicast request in advance.

In the third step, the client sends a multicast request in advance, and the step can be divided into three sub-steps: the server sends the calculation result of the synchronization time of the unicast and the multicast code stream to the client through the communication link;

The client calculates the time for sending the multicast request in advance. For the specific process, refer to the third step of the method for calculating the time when the client sends the multicast request in advance.

When the client arrives at the time when the multicast request is added in advance, it sends a join multicast request. The implementation of the technical solution will be further described in detail below with reference to the accompanying drawings:

1 is a schematic diagram of a method for calculating a time for pre-sending a multicast request according to the present invention: wherein a horizontal axis t represents time and a vertical axis p represents a progress of transmission of a media packet.

The straight line 101 is the progress of the media packet transmission of the multicast stream, which is equivalent to the progress of the server's reception and buffering of the multicast media packet, and the slope corresponds to the average code rate RMc of the multicast stream in Equation 1.

Line 102 is the progress of the media packet transmission of the unicast stream sent by the server, and its slope corresponds to the unicast stream average rate RUc in Equation 1.

At time T1, the ordinate difference corresponding to 101 and 102 is the amount of data separated by the unicast media packet sent by the server at this time and its received multicast media packet, that is, the PDif in Fig. 1.

101 and 102 intersect at time T3, which means that the unicast and multicast streams are synchronized at time T3, and the difference between T3 and T1 corresponds to TSync in Equation 1, for lines with known slopes of 101 and 102. In this case, TSync can be calculated from the ordinate difference of both T1 times, that is, Equation 1.

Now, from another angle, it is assumed that the server sends a unicast media packet at time T1, the packet delivery schedule corresponds to the ordinate of the line 102 at time T1, and the line 101 has the same ordinate as the ordinate. The horizontal coordinate TO of the point is the time when the media packet is sent in the multicast code stream, that is, the time when the server receives the media packet. Obviously, the difference between TO and T1 is that the media packet in Equation 2 is received from the The time interval between transmissions is TDif.

The difference in the abscissa of the two points on the two straight lines 101 and 102 and the same ordinate is known (ie TDif), and the slopes of the straight line 101 and the straight line 102 are known, then two mathematical operations can be calculated. The horizontal coordinate of the line intersection and the time interval TSync of T1, namely Equation 2.

Assume that the multicast request processing delay is TMcDly. In order to ensure that the client just receives the multicast stream when the unicast and multicast streams are synchronized, it needs to be sent a period of time relative to TSync (at time T2 in Figure 1). Join the multicast request, and the length of this advance is TMcDly.

In Fig. 1, the time interval TSync between T1 and T3 can be calculated by Equation 1 or Equation 2, and the time interval TMcDly between T2 and T1 is known. Then, between Equations 3 and T3 can be calculated. Time interval TReqMc.

The unicast and multicast stream synchronization time is usually in seconds, the multicast request processing delay is hundreds of milliseconds, and the media packet transmission time is basically on the order of 10 milliseconds, which is negligible compared with the first two. Therefore, the calculation method proposed by the present invention ignores the transmission time of the media packet on the network.

The foregoing operation road for pre-sending the time of joining the multicast request in the fast switching process of the channel may represent the process shown in FIG. 2, and the process includes the following steps:

Step 210: Collect the processing time overhead of the data device to process the join multicast request, and the operation may be implemented by setting a collecting unit.

Step 220: Calculate the time for unicast and multicast code stream synchronization.

Step 230: Calculate the time when the client sends a multicast request in advance.

The operations in steps 220 and 230 can be implemented by setting up a computing unit.

The foregoing operation idea of pre-sending a multicast request in the fast channel switching process may represent a flow as shown in FIG. 3 or FIG. 4 and the like.

The process shown in Figure 3 includes the following steps: Step 310: Notify the server of the multicast request processing delay.

Step 320: The server calculates the time when the client sends the multicast request in advance.

Step 330: The server control client sends a join multicast request in advance.

The process shown in Figure 4 includes the following steps:

Step 410: Notifying the client of the multicast request processing delay.

Step 420: The server calculates the time for the unicast to synchronize with the multicast code stream.

Step 430: The client sends a multicast request in advance.

The notification operation in Figures 3 and 4 can be notified of the setting notification unit implementation.

Referring to FIG. 5, FIG. 5 is a deployment model of two embodiments provided by the present invention, where the entities involved mainly include a data device 501, a server 502, and a client 503, and adopt an Internet Group Management Protocol (IGMP). ) to support multicast.

The server 502 can send an IGMP message to the data device 501 via the channel 509 to join the multicast group in which the channel is located, and the data device 501 transmits the multicast code stream to the server 502 via the channel 504.

The client 503 can send an IGMP message to the data device 501 through the channel 505 to join the multicast group where the channel is located, and the data device 01 sends the multicast code stream to the client 503 via the channel 506.

A two-way communication channel 507 is established between the server 502 and the client 503 via RTCP for message communication related to fast channel switching, and the server 502 transmits the buffered unicast stream to the client 503 via the channel 508.

The channel 504 and the channel 506 support the multicast, and the upper stream is encoded by the RTP. The unicast stream sent by the server 502 to the client 503 through the channel 508 is still RTP-encapsulated, and the RTP sequence number field is not modified. Once the RTP sequence number of the unicast code stream received by the client can be seamlessly connected with the RTP sequence number of the multicast stream, it is considered that the unicast and multicast code streams are synchronized.

After the server 502 starts, it sends an IGMP message to the data device 501 through the channel 509. Join the multicast group where the live channel is located, and continue to receive the media packet through the channel 504 for caching. The client 503 continuously counts the time interval between the sending of the join multicast request and the reception of the multicast code stream, and the minimum or average value thereof is used as a multicast request processing delay.

Referring to FIG. 6, FIG. 6 is a flowchart of a fast channel switching process in Embodiment 1. The left and right sides separated by a broken line are respectively a processing flow of a server and a client, and the vertical solid arrows indicate respective processing steps of a server or a client. The order of the lines, and the horizontal dotted arrow gives the sequence of the corresponding processing steps of the server and client as the start and end points of the arrow respectively. The process shown in Figure 6 includes the following steps:

Step 601: The client requests a fast channel switching service to the server, where the request message carries the multicast request processing delay data.

Step 602: The server receives the fast channel switching request of the client, and extracts the multicast request processing delay data to save;

Step 603: The server sends the buffered multicast code stream to the client from the I frame. Step 604: The set top box receives and displays the unicast code stream sent by the server.

Step 605: The server calculates a time for sending the multicast request in advance, and notifies the client to join the multicast group immediately when the corresponding time arrives;

Step 606: The client sends an IGMP message to the data device, requesting to join the multicast group. Step 607: The client receives the multicast code stream, and when the unicast and the multicast code stream are synchronized, switch to use the multicast code stream for decoding. And notifying the server to stop sending the unicast code stream;

Step 608: The server stops sending the unicast code stream.

Referring to FIG. 7, FIG. 7 is a flow chart of the fast channel switching process of the second embodiment, which is separated from the left and right by a dotted line, and the meanings of the solid arrow and the dotted arrow are also the same as those in FIG. 6. The process shown in Figure 7 includes the following steps:

Step 701: The client requests a fast channel switching service from the server.

Step 702: The server receives a fast channel switching request from the client, starting from the I frame to the client. Sending the buffered multicast code stream;

Step 703: The client receives the unicast code stream sent by the server and displays it.

Step 704: The server calculates a time for synchronizing the unicast with the multicast code stream, and notifies the client of the result;

Step 705: The client calculates the time for sending the multicast request in advance according to the synchronization time of the unicast and multicast code streams provided by the server, and the delay of the multicast request processing saved by the client;

Step 706: The client sends an IGMP message to the data device at the corresponding time according to the calculation result of the previous step, and requests to join the multicast group.

Step 707: The client receives the multicast code stream, and when the unicast is synchronized with the multicast code stream, switches to use the multicast code stream for decoding, and notifies the server to stop sending the unicast code stream.

Step 708 The server stops sending the unicast code stream.

In summary, the present invention essentially implements a delay request to control a client to pre-send a multicast request according to a multicast request processing delay, so that when unicast and multicast are synchronized, the client just receives the group. The broadcast stream not only ensures the connection between the unicast and multicast streams on the client, but also reduces the time for the server to send the unicast stream, thereby reducing the deployment cost of fast channel switching.

The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Industrial applicability

The invention discloses a method and a system for pre-sending a multicast request during fast channel switching, which can collect the processing time cost of the data device to process the multicast request, calculate the synchronization time of the unicast and the multicast stream, and calculate the client. The terminal pre-issues the moment of joining the multicast request; thereby shortening the time for the server to send the unicast code stream, saving processing power, and reducing deployment cost.

Claims

Claim

The method of pre-sending the multicast request in the fast channel switching includes: collecting the processing time cost of the data device to process the multicast request, calculating the synchronization time between the unicast and the multicast code stream, and calculating the client pre-issuing the joining group. The moment of the request.

2. The method according to claim 1, wherein

The collecting method is at least one of the following: and when a plurality of different values are obtained, a single value is obtained by using a statistical method including taking a minimum value or an average value as a multicast request processing delay:

TSync-PDif/(RUc-RMc) Formula 1

TSync=TDif/( a Uc-1) Equation 2

The method for calculating the time when the computing client sends the multicast request in advance is: TReqMc=TSync-TMcDly Equation 3

In the above formula, TReqMc is the relative time for the client to pre-send the multicast request, TSync is the unicast and multicast stream synchronization time, and TMcDly is the multicast request processing delay.

3. The method of pre-sending the multicast request in the fast channel switching, the method includes: notifying the multicast request processing delay to the server, the server calculating the time when the client sends the multicast request in advance, and the server controlling the client pre-issuing the joining group Broadcast request.

4. The method according to claim 3, wherein

The notification method is: the client saves the multicast request processing delay value, and sends the delay value to the server through the communication link; and the multicast request processing delay is used as the configuration parameter of the server;

TReqMc=TSync-TMcDly Equation 3

5. The method of pre-sending the multicast request in the fast channel switching, the method includes: notifying the multicast request processing delay to the client, and the server calculates the time for the unicast to synchronize with the multicast stream, and the client sends the multicast in advance. request.

6. The method according to claim 5, wherein

The method for the server to calculate the time for synchronizing the unicast with the multicast code stream is: TSync=PDif/(RUc-RMc) Equation 1 In the above equation, TSync is the estimated time of synchronization between unicast and multicast streams. PDif is the unicast media packet sent by the server at a moment and its received multicast media. The amount of data separated by packets, RUc is the average bit rate of the unicast stream sent by the server, and RMc is the average bit rate of the multicast stream; dividing the divisor and the dividend on the left side of Equation 1 by RMc, the following equivalent formula is obtained. :

TSync=TDif/( a Uc-1) Equation 2

The method for the client to send a multicast request in advance is:

7. The system for transmitting the multicast request in advance when the fast channel is switched, including the collecting unit and the calculating unit; wherein,

8. The system according to claim 7, wherein

When the collecting unit performs the collecting, the collecting method used is at least one of the following; and when a plurality of different values are obtained, a single value is obtained by using a statistical method including taking a minimum value or an average value. , as a multicast request processing delay:

Experimental analysis; use the network host that supports multicast function to conduct experiments, measure its transmission from the plus The time interval between the incoming multicast request and the received multicast stream;

TSync=PDif/(RUc-RMc) Formula 1

TSync=TDif/( a Uc-1) Equation 2

The calculating unit is used when: calculating the time when the client sends a multicast request in advance: TReqMc=TSync-TMcDly Formula 3

9. The system for transmitting the multicast request is pre-sent in the fast channel switching, including the notification unit, the server, and the client; wherein,

10. The system according to claim 9, wherein

When the notification unit performs the notification, it is used to: trigger the client to save the multicast request processing delay value, and send it to the server through the communication link; Configuration parameters;

When the server calculates the time when the client sends the multicast request in advance, it is used to:

TReqMc=TSync-TMcDly Equation 3

11. The system for adding a multicast request in advance, including a notification unit, a server, and a client, when the fast channel is switched;

The client is configured to send a join multicast request in advance.

12. The system of claim 11 wherein

TSync=PDif/(RUc-RMc) Formula 1

When the client sends a multicast request in advance, it is used to: