Parallel transmission dispatching method for stream media data

[0054]The streaming media server only needs to send data to the outside, so only the sending management module needs to be deployed, while other nodes need to receive data and send data to the downstream child nodes, so both the sending management module and the receiving management module need to be deployed. The receiving management module deployed on the child node acts as a scheduler, and sends a scheduling command to the sending management module deployed on the parent node, coordinating each parent node to jointly provide streaming media data for the child node.

[0055] In each round, the sending management module sends the data allocated to the transmission in a GOP to each child node in turn, and piggybacks the priority MAP and the data ownership MAP in the first packet of each GOP. After sending a GOP data for each child node, receive whether there are new messages, these messages include "new child node join message", "exit channel message" and "redistribute transmission ratio message" and so on. In this way, messages can be processed in a timely manner while transmitting data as quickly as possible. For the flow chart of sending data, see figure 1.

[0056] When the sending management module receives the command packet of the reassignment task ratio of the receiving management module of the child node, it needs to update the data structure, transmit data according to the new ratio, and pay attention to the synchronization problem with other parent nodes. figure 2 The flowchart for rescheduling the sending management module, that is, the process of the sending management module reassigning a transmission task to a certain child node. Due to the existence of network delay, stale command packets for reassigning transmission tasks may be received, so it is necessary to check the serial number to determine whether it is stale. If it is not stale, compare the reference GOP number (denoted as g) in the command packet with the number of the next data packet to be transmitted (denoted as h). If g>h, the data packets between h and g need to be transmitted according to the original ratio; if g

[0057] The receiving management module mainly has two functions of receiving data and scheduling parent node transmission. The receiving management module may receive ACK or streaming media data packets from the parent node. The flow chart of receiving data received by the management module is as follows image 3 As shown, the data structure of the corresponding parent node is updated if a valid ACK is received. If a data packet is received, it is judged whether it is the first packet of a GOP, the priority MAP and the data ownership MAP are taken out, the data structure of the buffer is updated, and it is used to judge whether retransmission is required. When a new packet arrives, it will check whether there is any packet loss. The principle of judging packet loss is that in a sequence of packets that the parent node needs to transmit, a packet has not arrived when three packets with a higher sequence number arrive. , it is considered that the package is lost. High-priority packets need to be retransmitted, and low-priority packets do not need to be retransmitted.

[0058] The main task of the receiving management module to schedule the transmission of the parent node is to periodically detect the network performance of the parent node, and allocate the proportion of the data to be transmitted according to the network performance of the parent node. If it is detected that the performance of the parent node does not meet the requirements, it needs to be reassigned. If necessary, delete the parent node with poor performance and apply for a new parent node, so as to adapt to the instability of the network. The receiving management module of the child node determines whether the network performance of the parent node meets the requirements by calculating the receiving rate and packet loss rate of each parent node. The receiving rate is to calculate the receiving rate and packet loss rate of the parent node by recording the sequence numbers and time of the N recently arrived packets to calculate the situation of the packets arriving within the last c seconds. When the receiving rate of the parent node is less than the threshold or the packet loss rate is greater than a certain threshold, the parent node cannot meet the network performance requirements and needs to be redistributed. The flow chart of the receiving management module to check the performance of the parent node is as follows Figure 4 As shown, the next step is to check whether the parent node is waiting for ACK. Since the command packet sent to the parent node to reassign transmission tasks requires ACK, the child node needs to maintain the status of whether the parent node ACK has arrived, and periodically check , if it is found that the ACK has not arrived, the command packet is sent again. If the ACK does not arrive within three cycles, the network performance of the parent node is set to be the worst. The result of this is that the parent node will be deleted during the subsequent redistribution of transmission tasks.

[0059] When the ratio needs to be redistributed, the Send rate of each parent node will be calculated:

[0060] T ( i ) = s / ( R ( i ) 2 p ( i ) / 3 + t RTO ( 3 3 p ( i ) / 8 ) p ( i ) ( 1 + 32 p ( i ) 2 ) )

[0061] This formula is the flow formula of TCP-Friendly. According to the packet loss event rate of the parent node and the RTT (Round Trip Time) and other parameters, the traffic in the case of TCP-Friendly is simulated, and this is used as the prediction of the network performance of the parent node. , according to this prediction, the current network performance of the parent node is judged, and the proportion of transmission tasks is allocated. In order to enhance the adaptability to network instability, it is necessary to avoid too large a proportion of a parent node when assigning the proportion. Therefore, when it is calculated that the sending proportion of a parent node is greater than 50% of the total data, the parent node is set. The proportion of sending data is 50%, then the remaining parent nodes redistribute the proportion. In order to find a suitable parent node, the parent node needs to be replaced when the proportion allocated by the parent node is too small. Therefore, when the proportion allocated by the parent node is less than 10% of the total data, the parent node is deleted, and then the proportion of the remaining parent nodes is redistributed. Finally, calculate whether the sum of the Send rates of the remaining parent nodes is greater than the bit rate of the streaming media. If it is less than that, you need to apply for a new parent node.

[0062] In order to evaluate the performance of the parallel transmission scheduling method for fault-tolerant streaming media data, we built a basic 100M Ethernet environment, used 20 terminals for testing, and collected the average delay and average reception rate of all nodes. The result is as Figure 5 , 6 shown.

[0063] The data in the figure shows that when the number of nodes increases gradually, the average reception rate of the terminal from other nodes decreases with the increase of the number of nodes, and tends to be stable when the number of nodes is greater than 5. That is to say, the parallel scheduling algorithm has relatively low requirements on the receiving bandwidth of a single node, and the average is stable at 10k/s. And in the test case of 20 terminals, the average delay time does not exceed 4.5 seconds.

[0064] Since the invention realizes the parallel acquisition of streaming media data from multiple nodes with equal status in logical function, it effectively solves the problem of end-to-end bandwidth limitation encountered in the current streaming media data transmission. Moreover, in the process of scheduling each parent node for transmission, it can dynamically adjust the proportion of transmission tasks among the parent nodes according to the network performance of the parent node, and avoid over-reliance on a single parent node, so it has better protection against network performance instability. Adaptability, in the case of failure of a single parent node, it can be quickly recovered, and has little impact on the fluency of streaming media data. In the process of streaming media transmission, according to the characteristics of video data, the priority of the data packet is marked, and according to the priority, it is decided whether to retransmit the lost packet, which takes into account the load of the network and the quality of the picture.

[0065] Thus, it can be seen that the present invention achieves the intended purpose.