JP2005167780A - Streaming data transmission apparatus and transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: Conventional streaming data transmission apparatuses and transmission methods conventionally require retransmission control in order to prevent packet loss during transmission, but conversely have a problem that it is difficult to pursue real-time performance. It was.
In order to solve the above problem, streaming data is stored in a transmission buffer memory 4 and either a first transmission protocol that guarantees the quality of transmission data by retransmission control or a second transmission protocol that does not perform retransmission control. Based on the data, the data stored in the buffer memory 4 is transmitted from the network device 6. In this case, the free space of the buffer memory 4 is detected by the CPU 7, and the transmission protocol of the network device 6 is switched by the CPU 7 in accordance with the detected free space of the buffer memory 4.
[Selection] Figure 1

Description

  The present invention relates to a streaming data transmission apparatus and transmission method.

  Streaming transmission that distributes data such as music and video using a network and reproduces received data in real time on the receiving side is becoming widespread. This is very convenient because it cannot be played back until all distributed data is received (see, for example, Patent Document 1).

By the way, in streaming transmission, retransmission control is required to prevent packet loss during transmission, but there has been a conflicting situation where it is difficult to pursue real-time performance.
JP 2002-77251 A (2nd to 6th pages, FIG. 1)

  As described above, conventional streaming data transmission apparatuses and transmission methods require retransmission control in order to prevent packet loss during transmission, but conversely have a problem that it is difficult to pursue real-time performance. It was.

  The present invention has been made in view of these points, and it is an object of the present invention to provide a streaming data transmission apparatus and transmission method that can reduce packet loss during transmission and can send data in real time. And

  To achieve the above object, a streaming data transmission apparatus according to claim 1 performs a buffer memory for storing streaming data, a first transmission protocol for guaranteeing the quality of transmission data by retransmission control, and retransmission control. The transmission means for transmitting the data stored in the buffer memory based on one of the second transmission protocols not present, the means for detecting the free space of the memory, and the free space of the memory detected by the detection means And a means for switching the transmission protocol of the transmission means accordingly.

  A streaming data transmission apparatus according to claim 2 is the streaming data transmission apparatus according to claim 1, wherein the transmission protocol switching means sets the first transmission protocol when there is a free space in the buffer memory. When the free space of the buffer memory is selected, the transmission protocol of the transmission means is switched to select the second transmission protocol.

  Furthermore, the streaming data transmission device according to claim 3 is the streaming data transmission device according to claim 1 or 2, further comprising means for adding a serial number to the data packets output from the buffer memory. It is what.

The streaming data transmission device according to claim 4 is the streaming data transmission device according to claim 1 or 2, wherein the memory free capacity detecting means is configured to check whether the memory is free every time one packet data is transmitted from the transmission means. It is characterized by being configured to detect a capacity.

  The streaming data transmission method according to claim 5 includes the steps of storing streaming data in a buffer memory, detecting the free capacity of the buffer memory, and according to the free capacity of the buffer memory detected in the detecting step, Selecting one of a first transmission protocol that guarantees the quality of transmission data by retransmission control and a second transmission protocol that does not perform retransmission control, and transmitting the data stored in the buffer memory. It is characterized by.

  A streaming data transmission method according to a sixth aspect is the streaming data transmission method according to the fifth aspect, wherein serial numbers not based on the first and second transmission protocols are added to the data packets output from the buffer memory. It is characterized by comprising steps.

  ADVANTAGE OF THE INVENTION According to this invention, the packet loss at the time of transmission can be reduced and the streaming data transmission apparatus and transmission method which can send data in real time can be provided.

  Hereinafter, embodiments of a streaming data transmission apparatus and a transmission method according to the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit block diagram showing an embodiment of a streaming data transmission apparatus according to the present invention.

  In the figure, 1 is a transmission side device, and 2 is a reception side device. The transmission side device 1 is supplied with video, audio, etc. as input, and outputs it as digital streaming data. The transmission buffer memory 4 temporarily stores the streaming data from the encoder 3. The transmission side device 1 stores the data from the buffer memory 4. The network device 6 is configured to read and transmit data to the receiving device 2 via the network 5, and the CPU (Central Processing Unit) 7 that checks the remaining capacity of the memory 4 and controls the network device 6. Note that the network 5 may have any form or route, and in short, the data may be delivered to the receiving side device 2. The transmission path may be wired or wireless.

  The receiving-side device 2 receives the data transmitted through the network 5, the network device 8, the reception buffer memory 9 in which the data received by the network device 8 is stored, and the data stored in the buffer memory 9 It comprises a decoder 10 that reads, decodes and outputs to a display device, a network device 8 and a CPU (central processing unit) 11 that controls the buffer memory 9.

  Next, the operation of the apparatus shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a diagram schematically showing the amount of data stored in the transmission buffer memory 4. FIG. 2A shows a case where the amount of stored data 21 (hatched portion) is small, and FIG. A case where the amount of data 22 is large is shown. Reference numerals 23 and 24 denote free storage areas.

First, the streaming data encoded by the encoder 3 is temporarily stored in the transmission buffer memory 4. When the remaining capacity of the buffer memory 4 is sufficient (see FIG. 2A), transmission is performed from the network device 6 to the receiving-side device 2 using the TCP / IP protocol. In the TCP / IP protocol, data can be reliably transmitted by retransmitting data, so that a complete video can be reproduced on the receiving side. However, if transmission errors occur continuously and retransmissions occur frequently, the transmission rate decreases and the data in the transmission buffer memory 4 increases. Therefore, when the remaining capacity of the buffer memory 4 is reduced (see FIG. 2B), the transmission protocol is switched to the UDP / IP protocol to prevent the buffer memory 4 from overflowing.

  The data transmission rate sent from the encoder 3 needs to satisfy the following formula (1).

(Equation 1)
Data transmission rate <Transfer rate when retransmission does not occur in TCP / IP protocol (1)
If the above equation (1) is satisfied, the transmission buffer memory 4 will not become full as long as retransmission does not occur even if transmission is performed using the TCP / IP protocol. The transfer rate satisfies the following formula (2).

(Equation 2)
TCP / IP protocol transfer rate <UDP / IP protocol transfer rate (2)
Therefore, when transmission is performed based on the UDP / IP protocol, the transmission buffer memory 4 is free.

  FIG. 3 shows a process flow on the transmission side. Hereinafter, the transmission process will be described in more detail with reference to FIG.

  When transmission is started, data is sent from the encoder 3 to the transmission buffer memory 4. Therefore, the transmission buffer memory 4 is checked (step S1), and it is checked whether or not the data to be transmitted is in the buffer memory 4 (step S2). If there is no data in the buffer memory 4 (NO in step S2), the process returns to step S1 to wait until the data comes. If there is data in the buffer memory 4 (YES in step S2), it is next checked whether or not the free space in the buffer memory 4 is sufficient (step S3). As a criterion for this determination, it is determined that there is an empty space when the amount of data stored as an example is within 80% of the total buffer memory capacity. Generally, the most efficient value is set through a transmission experiment or the like.

  If the free space in the buffer memory 4 is sufficient (YES in step S3), the CPU 7 controls the network device 6 to perform data transfer based on the TCP / IP protocol, and the network device 6 conforms to the TCP / IP protocol. Based on this, data transfer is performed (step S4). When the buffer memory 4 has a small free space (NO in step S3), the CPU 7 controls the network device 6 to perform data transfer based on the UDP / IP protocol, and the network device 6 transmits based on the UDP / IP protocol. (Step S5).

  Whether the buffer memory 4 has enough free space is determined for each packet at the time of transmission. In the UDP / IP protocol, transmission confirmation is not performed by an acknowledge signal (ACK) or the like, so that the operation is completed with one transmission. On the other hand, in the TCP / IP protocol, it is checked whether or not the packet has been normally received by ACK from the receiving side (step S6).

If the reception is normal (YES in step S6), the transmission operation is completed. If the reception is not normally performed (NO in step S6), the same packet is transmitted again when a non-acknowledge signal (NACK) comes or a timeout occurs. Since data is sent from 3 to the buffer memory 4, there is a risk that the buffer memory 4 will overflow. Therefore, it is necessary to check whether or not the remaining capacity in the buffer memory 4 is sufficient even during retransmission (step S7). If the remaining capacity decreases (NO in step S7), it is necessary to abort the retransmission.

  Further, even if the remaining capacity of the buffer memory 4 is sufficient (YES in step S7), it is checked whether the number of retransmissions is less than the prescribed number N (step S8), and when the number of retransmissions exceeds the prescribed number N. (NO in step S8) similarly terminates retransmission. If the number of retransmissions is less than the prescribed number N (YES in step S8), the process returns to step S4, and data transfer is performed again based on the TCP / IP protocol.

  The packet whose retransmission has been aborted in steps S7 and S8 is sent only once based on the UDP / IP protocol (step S5). This process is an option and is not always necessary. There is no problem even if the packet is discarded when the retransmission is terminated. Here, transmission is finally performed based on the UDP / IP protocol, but this is based on the idea that changing the protocol will reduce the amount of headers and increase the possibility of transmission.

  When the transmission is completed, the process returns to the transmission process again to transmit the next packet, and the buffer memory 4 is checked again (step S1). Thereafter, the same processing is repeated.

  According to the above embodiment, packet loss during transmission can be reduced, and data can be sent in real time.

  In the above embodiment, the CPU 7 checks the free capacity of the transmission buffer memory 4. However, since the free capacity can be known by checking the stored data amount, the stored data amount is checked. It does not matter if you check either one.

  By the way, when data is transmitted using a different protocol, data reconstruction at the receiving device 2 is a problem. In both the TCP / IP and UDP / IP protocols, there is a possibility of reaching the receiving side in an order different from the sending timing on the transmitting side due to a difference in header size or presence / absence of retransmission. This is particularly important in a wireless environment. As a means for preventing this, there is a method of adding a sequence number for each packet. Unlike the sequence number of a general packet, it is not sent with a sequence number closed only with the UDP / IP protocol and a sequence number closed only with the TCP / IP protocol. It is to manage the sequence number collectively by protocol. The sequence numbers are added in the order sent out from the transmission buffer 4 regardless of the protocol. On the other hand, the receiving side device 2 performs data rearrangement with reference to the sequence number portion of the received packet.

Details will be described below with reference to FIG. FIG. 4 is a diagram illustrating how packets received by the receiving-side device 2 are rearranged in the reception buffer memory 9 in the order of transmission from the transmission buffer memory 4. In the figure, 31 and 32 are packets transmitted from the network device 6 based on the UDP / IP protocol, and 33 is a packet transmitted from the network device 6 based on the TCP / IP protocol. Reference numerals 34 to 36 denote data relating to sequence numbers added to the packets 31 to 33, respectively. Here, the packets 31 to 33 are sent from the transmission buffer memory 4 in the order of the packets 31, 33, and 32.

  The packet data 31 to 33 are rearranged in the order of transmission in the reception buffer memory 9 under the control of the CPU 11 based on the sequence number data (see FIG. 4 / the right side is the head position in the figure).

  Although it is easiest to add the sequence number to the head of the data portion, the sequence number in the RTP protocol may be used as it is. By adding the sequence number, it is possible to sense a packet loss on the receiving side.

1 is a block diagram showing an embodiment of a streaming data transmission apparatus according to the present invention. The figure for demonstrating the data amount in the transmission buffer memory of the apparatus of FIG. The flowchart for demonstrating operation | movement of the apparatus of FIG. The figure for demonstrating the data transmission in other embodiment of the streaming data transmission apparatus which becomes this invention.

Explanation of symbols

1: Transmission side device 2: Reception side device 3: Encoder 4: Transmission buffer memory 5: Network 6: Network device 7: CPU (central processing unit)
8: Network device 9: Reception buffer memory 10: Decoder 11: CPU (central processing unit)

Claims (6)

  Stored in the buffer memory based on one of a buffer memory for storing streaming data, a first transmission protocol that guarantees the quality of transmission data by retransmission control, and a second transmission protocol that does not perform retransmission control A transmission means for transmitting data, a means for detecting the free space of the memory, and a means for switching the transmission protocol of the transmission means in accordance with the free space of the memory detected by the detection means Streaming data transmission device.   2. The streaming data transmission apparatus according to claim 1, wherein the transmission protocol switching means selects the first transmission protocol when there is a free space in the buffer memory, and there is no free space in the buffer memory. In this case, the streaming data transmission apparatus is configured to switch the transmission protocol of the transmission means so as to select the second transmission protocol.   3. The streaming data transmission apparatus according to claim 1, further comprising means for adding a serial number to the data packets output from the buffer memory.   3. The streaming data transmission apparatus according to claim 1, wherein the memory free capacity detecting means is configured to detect the free capacity of the memory every time one packet data is transmitted from the transmitting means. A streaming data transmission device.   The step of accumulating streaming data in the buffer memory, the step of detecting the free space of the buffer memory, and the step of guaranteeing the quality of transmission data by retransmission control according to the free space of the buffer memory detected in the detection step A streaming data transmission method comprising: selecting one transmission protocol and a second transmission protocol that does not perform retransmission control, and transmitting data stored in the buffer memory. 6. The streaming data transmission method according to claim 5, further comprising a step of adding a serial number not based on the first and second transmission protocols to the data packet output from the buffer memory. Transmission method.

Images