A packet loss retransmission method in real-time streaming media transmission system

Abstract

The present invention relates to a packet loss retransmission method in a real-time streaming media transmission system, comprising the following steps: 1) a receiving end returns an ACK for each packet received, wherein the ACK information records the current packet information and the information of the multiple packets received previously, to prevent ACK loss; a marking method similar to SACK is as follows: an 8-bit information is used to record the reception information of the 8 packets before the current packet ID, which is set to 1 when received and to 0 when not received; 2) a sending end controls retransmission, and when the received ACK information indicates that a data packet is lost, data is retransmitted; 3) the sending end retransmits data, not the original packet, but forward error correction coded data. The present invention can solve the problem of ACK packet loss and solve the problem of retransmitted packet loss by utilizing out-of-order packets in the network.

Description

Technical Field

[0001] The present invention belongs to the technical field of data transmission systems of real-time streaming media transmission systems, and in particular relates to a retransmission control method of a sending end of a real-time streaming media transmission system. Background Art

[0002] The existing real-time streaming media transmission system based on the UDP protocol adopts the packet loss retransmission method. After the receiving end detects the packet loss, it sends a retransmission request. The sending end retransmits the lost data packet and performs one or more retransmissions depending on the packet loss situation.

[0003] When out-of-order packets occur, for example, if the data packets are numbered 1, 2, 3, 4, 5, 6, and 7, and the receiver receives data packets in the order of 1, 2, 5, 4, 6, and 7, it will automatically request retransmission of packets 3 and 4 upon receiving packet 5, rather than just requesting retransmission of packet 3. In other words, out-of-order packets will be treated as lost packets.

[0004] However, the existing network environment is becoming increasingly complex, especially in the WIFI environment, where the packet loss rate and disorder rate are relatively high. According to tests, when multiple devices are connected to the same WIFI routing device at the same time, the packet loss rate can reach more than 1% at the peak, and the disorder rate can reach more than 0.5%.

[0005] The traditional packet loss retransmission method has the following defects:

[0006] 1. Treat out-of-order packets as lost packets.

[0007] 2. Retransmission request packets will still be lost, and if a second request is made after the retransmission request packet is lost, it will cause a large delay.

[0008] 3. Retransmitted data packets are prone to packet loss, which also raises the question of whether to make a second request.

[0009] The packet loss rate has a significant impact on the viewing experience of real-time streaming systems. Taking a 1% packet loss rate as an example (in wireless networks, including out-of-order rates), excluding congestion losses, the theoretical packet loss rate after a retransmission is 0.1% (0.01%). However, the actual tested value is around 0.01%. For a 128kBps (1Mbps) bitstream, there are approximately 100 packets per second (each 1372 bytes). A packet loss rate of 0.01% (0.01%) means an unrecoverable packet loss every 100 seconds, which manifests as a pause in playback (packet loss waiting for key frames). If the packet loss rate is 0.01%, then a pause occurs every 10 seconds.

[0010] Therefore, the traditional packet loss retransmission method cannot meet the transmission requirements of real-time streaming media systems. Summary of the Invention

[0011] The purpose of the present invention is to improve the retransmission efficiency of a real-time streaming media transmission system based on the UDP protocol in a network with a high packet loss rate.

[0012] The specific technical solution of the present invention is:

[0013] A method for packet loss retransmission in a real-time streaming media transmission system comprises the following steps:

[0014] 1) The receiving end returns an ACK for each packet it receives. The ACK information records the current packet information and the information of multiple packets received previously to prevent ACK loss. The marking method is similar to SACK as follows: an 8-bit information is used to record the reception information of the 8 packets before the current packet ID. When received, the position is set to 1, and if not received, it is set to 0.

[0015] 2) The sender controls retransmission and retransmits data when the received ACK information indicates that a data packet is lost;

[0016] 3) The data retransmitted by the sender is not retransmitted using the original packet, but retransmitted using forward error correction coded data.

[0017] Furthermore, the step 3) uses forward error correction coded data retransmission, which means that if the data packet sequence numbers are 1, 2, 3, 4, 5, 6, 7, if the receiving end receives the data packets in the order of 1, 2, 5, 4, 6, 7, assuming that the ACK packet is not lost, the ACKs received by the sending end are 1, 2, 5, 4, 6, 7 in sequence. When the sending end receives ACK No. 5, it uses 1, 2, 3, 4, 5 as the original packets to generate two forward error correction coded data packets FEC1 and FEC2 for transmission. The receiving end can use 1, 2, 5, FEC1, and FEC2 to decode packets 3 and 4. Similarly, if the retransmitted packet is lost, the receiving end uses 1, 2, 5, 4, FEC1 or FEC2 to decode packet No. 3.

[0018] The method of the present invention has the following advantages:

[0019] 1. It can solve the problem of ACK packet loss.

[0020] 2. Use out-of-order packets in the network to solve the problem of lost retransmission packets.

[0021] According to tests, in a network environment with a packet loss rate of 1%, after one retransmission, the packet loss rate can be reduced to close to the theoretical level of one ten-thousandth. Moreover, because out-of-order packets can be used to recover data, data decoding can be performed without waiting for all retransmitted packets to reach the receiver, thereby appropriately improving the real-time performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic diagram of a packet loss retransmission method in a real-time streaming media transmission system. DETAILED DESCRIPTION

[0023] like Figure 1 Figure 2 shows a schematic diagram of a packet loss retransmission method in a real-time streaming media transmission system according to the present invention. The transmitting end includes a data transmission module, a forward error correction encoding module, and an ACK receiving buffer processing module. The receiving end includes a data receiving module, a forward error correction decoding module, and an ACK generation module. The transmitting end performs normal data transmission and receives an ACK. If data loss (ACK loss) is detected, the forward error correction encoding module generates an error-correcting data packet based on the number of lost packets, and retransmits the error-correcting data packet.

[0024] After receiving the normal data, the receiving end uses the ACK generation module to generate ACK data and returns it to the sending end.

[0025] After receiving the error-corrected data packet, the receiver uses the forward error correction decoding module to decode the data and recover the lost data.

[0026] A packet loss retransmission method in a real-time streaming media transmission system comprises the following steps:

[0027] 1) The receiving end returns an ACK for each packet it receives. The ACK information records the current packet information and the information of multiple packets received previously to prevent ACK loss. The marking method is similar to SACK as follows: an 8-bit information is used to record the reception information of the 8 packets before the current packet ID. When received, the position is set to 1, and if not received, it is set to 0.

[0028] 2) The sender controls retransmission and retransmits data when the received ACK information indicates that a data packet is lost;

[0029] 3) The sender retransmits data using forward error correction (FEC) instead of the original packet. For example, if the data packets are numbered 1, 2, 3, 4, 5, 6, or 7, and the receiver receives data packets in the order 1, 2, 5, 4, 6, or 7, assuming the ACK packets are not lost, the sender receives ACKs 1, 2, 5, 4, 6, or 7. When the sender receives ACK number 5, it uses packets 1, 2, 3, 4, or 5 as the original packets to generate two forward error correction (FEC) packets, FEC1 and FEC2, for transmission. The receiver can then decode packets 3 and 4 using packets 1, 2, 5, FEC1, or FEC2. Similarly, if the retransmitted packet is lost, the receiver can decode packet 3 using packets 1, 2, 5, 4, FEC1, or FEC2.

Claims

1. A method for packet loss retransmission in a real-time streaming media transmission system, comprising the following steps: 1) The receiving end returns an ACK for each packet it receives. The ACK information records the current packet information and the information of multiple packets received previously to prevent ACK loss. The marking method is similar to SACK as follows: an 8-bit information is used to record the reception information of the 8 packets before the current packet ID. When received, the position is set to 1, and if not received, it is set to 0. 2) The sender controls retransmission and retransmits data when the received ACK information indicates that a data packet is lost; 3) The data retransmitted by the sender is not retransmitted using the original packet, but retransmitted using forward error correction coded data; The step 3) uses forward error correction coded data retransmission, which means that if the data packet sequence numbers are 1, 2, 3, 4, 5, 6, 7, if the receiving end receives the data packets in the order of 1, 2, 5, 4, 6, 7, assuming that the ACK packet is not lost, the ACKs received by the sending end are 1, 2, 5, 4, 6, 7 in sequence. When the sending end receives ACK No. 5, it uses 1, 2, 3, 4, 5 as the original packets to generate two forward error correction coded data packets FEC1 and FEC2 for transmission. The receiving end can use 1, 2, 5, FEC1, and FEC2 to decode packets 3 and 4. Similarly, if the retransmitted packet is lost, the receiving end uses 1, 2, 5, 4, FEC1 or FEC2 to decode packet No. 3.

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