JP2007324876A - Data transmitter, data receiver, data transmitting method, data receiving method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a receiving side to properly restore data even when continuous packet losses occur in a network. <P>SOLUTION: This data transmitter is provided with: a means for generating encoded data packet for network transmission from encoded data; a means for generating an encoded data packet group from a preset number of continuous encoded data packets; a means for generating a redundant data packet group comprising one or a plurality of redundant data packets for performing error correction for encoded data packets in the encoded data packet group and generating an encoded data packet group with redundant data by the redundant data packet group and the encoded data packet group; and a means for rearranging a transmitting order of packets in the prescribed number of continuous encoded data packet groups with redundant data and transmitting the packets in the encoded data packet groups with redundant data in the rearranged order. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a technique that enables packet recovery to be performed properly on the receiving side even when packet loss occurs continuously in a network when redundant data is attached for error correction. It is.

  A system for transmitting and receiving high-definition video over a network such as the Internet has been proposed. In such a system, video data encoded with MPEG2 using a commercially available HD camera is packetized on a PC, sent to another PC via a network, and from that PC via a digital broadcast recorder. Displayed on a high-definition TV. However, the code amount of MPEG2 data of an HD camera is 19 to 25 Mbps, and in the currently popular best-effort Internet, packet loss occurs due to congestion, and stable video communication cannot be performed.

  On the other hand, in general digital broadcasting, by adding redundant data for error correction to video data encoded with MPEG2, the original video data is restored even when the radio wave condition is bad and data loss occurs due to weather or the like. A mechanism has been proposed (Non-Patent Document 1). Therefore, it is conceivable to apply this technique to the solution of problems such as packet loss in the above-mentioned high-definition video transmission.

However, even if an error correction mechanism such as that described in Non-Patent Document 1 is introduced, error correction cannot be performed if the network congestion situation becomes worse than previously assumed. In particular, there are many cases in which multiple packets are lost continuously in a discrete manner on the Internet. If redundant data is increased more than necessary to cope with such continuous packet loss, the bandwidth increases and network congestion occurs. The situation gets worse and further packet loss occurs.
Further, there is a technique described in Patent Document 1 as a conventional technique for transmitting and receiving video with an error correction code added. The purpose of this technique is to suppress an increase in transmission delay and calculation amount by adding an error correction code. However, even when this technique is used, there is a problem that when a plurality of packets are continuously lost, data cannot be properly restored on the receiving side.
http://www.soumu.go.jp/s-news/2003/030127_2.html JP 2005-347927 A

  The present invention has been made in view of the above points, and in a system in which redundant data for error correction is added to transmit / receive encoded data, even if continuous packet loss occurs in the network, redundancy is achieved. It is an object of the present invention to provide a technique that makes it possible to appropriately restore data on the receiving side without increasing data.

  The above-described problems include encoded data packet generation means for generating encoded data packets for network transmission from encoded data obtained by encoding video or audio, and a predetermined number of consecutive encoded data packets. Redundant data comprising encoded data packet group generation means for generating an encoded data packet group from one and one or a plurality of redundant data packets for performing error correction on the encoded data packet in the encoded data packet group A predetermined number of consecutive encoded data packet group generating means with redundant data, generating a packet group, and generating an encoded data packet group with redundant data using the redundant data packet group and the encoded data packet group; The transmission order of packets in the coded data packet group with redundant data was changed, and changed. Is solved by the data transmitting apparatus characterized by comprising a transmission order changes transmission means for transmitting a packet in said redundant data with the encoded data packets to the network turn.

  The encoded data packet group generation unit with redundant data, when generating the redundant data packet, divides each packet of the encoded data packet group from the beginning for each predetermined number of bits, One or a plurality of redundant bit strings are calculated from a set of bit strings at the same position from the head in a plurality of packets constituting the data, and one or more redundant packets having the same length as the encoded data packet are combined by combining them. A plurality may be generated.

  Further, the transmission order changing transmission means is configured to determine the predetermined number based on the number of consecutive packet losses in the network and the maximum number of packets that can be recovered by error correction even if lost in one encoded data packet group with redundant data. May be calculated.

  In this case, the transmission order changing transmission means can set the predetermined number to a value equal to or larger than a value obtained by dividing the number of consecutive packet losses by the maximum number of packets that can be restored.

  Further, the transmission order change transmission means transmits one packet in one encoded data packet group with redundant data in the predetermined number of consecutive encoded data packet groups with redundant data, and then By repeating the transmission of one packet in the encoded data packet group with redundant data in the next order, the packet can be transmitted.

  In addition, the present invention provides receiving means for receiving a plurality of packets including encoded data packets generated from encoded data obtained by encoding video or audio from a data transmitting apparatus via a network, and to be received A continuous packet loss number notifying means for measuring the number of packets continuously lost in the network from the number of packets and the number of packets actually received, and notifying the number to the data transmitting device, and a code comprising a plurality of encoded data packets One or more redundant data packets attached to the encoded data packet group and the encoded data packet group with redundant data consisting of the encoded data packet group is identified from the received plurality of packets, If there is a lost encoded data packet in the encoded data packet group with data, the encoded data And restoring means for restoring the error correction packet, decodes the coded data, can also be configured as a data receiving apparatus characterized by comprising an output means for outputting the decoded data. The present invention can also be configured as a program that causes a computer to function as each unit of the data transmission device, and a program that causes a computer to function as each unit of the data reception device.

  According to the present invention, in a system that transmits and receives encoded data by adding redundant data for error correction, even if continuous packet loss occurs in the network, the receiving side does not increase redundant data. It is possible to restore data appropriately.

  Embodiments of the present invention will be described below with reference to the drawings.

(System configuration)
FIG. 1 shows a system configuration diagram according to an embodiment of the present invention. As shown in FIG. 1, the system according to the present embodiment has a configuration in which a transmission terminal 1 and a reception terminal 2 are connected to the Internet 3.

  An HD camera 4 with a video encoding function is connected to the transmission terminal 1. The receiving terminal 2 has an MPEG2 decoder and is connected to an HD compatible TV monitor 5. For example, when a PC (personal computer) is used as the transmission terminal 1 and the reception terminal 2, the transmission terminal 1 and the HD camera 4 with video encoding function are connected by IEEE1394 (i-link), and the reception terminal 2 and the HD compatible TV are connected. The monitor 5 is connected by a component cable.

  FIG. 2 shows a functional configuration diagram of the transmission terminal 1. As shown in FIG. 2, the transmission terminal 1 includes a coded data receiving unit 11 that receives video coded data from the HD camera 4 with video coding function, and a packet for generating a coded data IP packet group with redundant data. The group generation processing unit 12, the IP packet transmission order change processing unit 13, the transmission unit 14 that transmits data to the Internet, and the continuous packet loss number are received via the Internet, and the IP packet transmission order change processing unit 13 receives A receiving unit 15 that notifies the number of consecutive packet losses is provided. The details of the encoded data IP packet group with redundant data, the transmission order changing process, the value received by the receiving unit 15 and the like will be described in detail in the description of the process flow to be described later.

  FIG. 3 shows a functional configuration diagram of the receiving terminal 2. As illustrated in FIG. 3, the receiving terminal 2 includes a receiving unit 21 that receives data from the Internet, a transmitting unit 22 that transmits a continuous packet loss number via the Internet, and a continuous packet loss number measurement process that measures the continuous packet loss number. Unit 23, an encoded data restoration processing unit 24 that performs an encoded data restoration process using an error correction technique, an encoded data decoding / display process that decodes the coded data and outputs (displays) to the monitor 5 The unit 25 is provided. The processing contents in the receiving terminal 2 will also be described in detail in the description of the processing flow described later.

  The arrangement of the functional units shown in each terminal is merely an example, and other functional configurations can be adopted as long as the following processing can be executed. Each terminal can be realized by installing a program for causing a computer (PC or the like) including a CPU, a storage device, and the like to execute processing described in this embodiment.

(Process flow)
Hereinafter, in the system shown in FIG. 1, the flow of processing when the encoded data is distributed from the transmission terminal 1 to the reception terminal 2 will be described with reference to the flowchart of FIG. 4.

  First, the transmission terminal 1 acquires video / audio encoded data from the HD camera 4 (step 1). The output format of the HD camera 4 includes an uncompressed HD-SDI format and a compressed MPEG2 format. In the present embodiment, the latter MPEG2 format will be described. Of course, the encoding process to the MPEG2 format may be performed in the transmission terminal 1.

  In general, the MPEG2 encoded data output from the HD camera 4 is in the MPEG2-TS format divided into 188 bytes. In this embodiment, the MPEG2 encoded data is in the MPEG2-TS format. And

  After acquiring the encoded data, the transmission terminal 1 performs an encoded data IP packet generation process (step 2). Here, when transmitting and receiving data via the Internet, the upper limit of the packet size that can be transmitted at one time is generally determined, and the size is about 1500 bytes. That is, even if a packet having a larger size is generated and transmitted, it is divided in the network. In such a case, if packet loss occurs on the network path, the original packet including the lost divided packet cannot be restored, and the packet loss increases. Therefore, in the process of generating the encoded data IP packet in step 2, for example, 7 packets of MPEG2-TS are sequentially combined and an IP header is added so that the upper limit of the packet size that can be transmitted at once is not exceeded. Generate a data IP packet. FIG. 5 shows an example of the encoded data IP packet generated in step 2.

  Next, the transmission terminal 1 performs a process for generating an encoded data IP packet group and a process for generating a redundant data IP packet group (steps 3 and 4). Before the description, the redundant data used in this embodiment is used. A data generation method will be described.

In the present embodiment, redundant bits are generated by a Reed-Solomon code (see, for example, “C MAGAZINE January 2005 issue, issued by Softbank Creative Corporation”). Reed-Solomon code is a technique that enables error detection / correction in units of a plurality of bits. In the Reed-Solomon code, as shown in FIG. 6, M redundant data are used for K original data each composed of a plurality of bits. The relationship between K and M is shown in FIG.
As shown in FIG. 7, for example, when Reed-Solomon encoding is performed in units of 4 bits, the number of original data is 11, and the number of redundant data is 4. In addition, even if packet loss of up to 2 of these 15 occurs, 11 original data can be restored. In the present embodiment, such redundant data using Reed-Solomon codes is used.

  In the generation process of the encoded data IP packet group in step 3 of FIG. 4, the transmitting terminal 1 divides the encoded data IP packet generated continuously into the number corresponding to a predetermined redundant data generation method, Generates a group of data IP packets. For example, when Reed-Solomon encoding is performed in units of 4 bits shown in FIG. 7, the number of encoded data IP packets included in one encoded data IP packet group is 11. FIG. 8 shows an example of an encoded data IP packet group including K encoded data IP packets.

  Subsequently, the transmitting terminal 1 performs a redundant data IP packet group generation process (step 4). The processing concept here is shown in FIG. As shown in FIG. 9, K encoded data IP packets corresponding to a predetermined redundant data generation unit B are divided by B bits from the head, and M pieces of B corresponding to B are divided in units of divided B bits. Redundant data is generated and combined in order. As a result, M redundant data IP packets (redundant data IP packet group) having the same length as the encoded data IP packet are finally generated. In the above processing, for example, when B is 4, K is 11 and M is 4 from the table shown in FIG.

  As shown in FIG. 9, a set of an encoded data IP packet group and a redundant data IP packet group is set as an encoded data IP packet group with redundant data (step 5 in FIG. 4). Here, identification information for identifying the same encoded data IP packet group with redundant data may be attached to each packet.

  Next, the transmission terminal 1 performs transmission order change processing and transmission for a plurality of encoded data IP packet groups with redundant data (steps 6 and 7).

  In the case of the above Reed-Solomon encoding in units of 4 bits, if 3 or more packets out of 15 IP packets in one encoded data IP packet group with redundant data are lost, 11 original data are obtained. If there is a packet loss, it cannot be recovered.

  Therefore, focusing on the fact that the event that multiple packets are continuously lost occurs discretely on the Internet, in this embodiment, even if multiple packets are continuously lost, individual redundant data In the attached encoded data IP packet group, processing is performed to rearrange the order of transmission of IP packets in order to make the number of losses within the number of losses that can be restored.

  A method of rearranging the transmission order in this embodiment will be described with reference to FIG. In the case shown in FIG. 10, P encoded data IP packet groups with redundant data are set as one unit, and the transmission order is rearranged within the unit. Specifically, after transmitting the k-th encoded data IP packet in the encoded data IP packet group with the p-th redundant data in the unit, the encoding with the p + 1-th redundant data is then performed in the unit. Rearrangement for transmission is performed in the order of transmitting the k-th encoded data IP packet in the data IP packet group. Then, after transmitting the k-th encoded data IP packet in the last (P-th) encoded data IP packet group with redundant data in the unit, return to the first encoded data IP packet group with redundant data, The k + 1-th encoded data IP packet in the encoded data IP packet group with redundant data is transmitted.

  By using such a transmission method, for example, even if P packets are continuously lost, only one IP packet is lost in one encoded data IP packet group with redundant data.

  Therefore, for example, when the maximum number of packet losses allowed in one encoded data IP packet group with redundant data is L, and X consecutive packet losses are detected on the receiving side, P (the number of coded data IP packet groups with redundant data in the unit) may be set to a value equal to or greater than X / L. More specifically, when the maximum number of packet losses allowed in one encoded data IP packet group with redundant data is 2, and 20 consecutive packet losses are detected on the receiving side, Let P be 20/2 = 10. That is, rearrangement of the transmission order as shown in FIG. 10 is performed with 10 encoded data IP packet groups with redundant data as one unit. The number of consecutive packet losses on the receiving side may be received from the receiving terminal 2 as will be described later, or a predetermined number may be set.

  In the transmission order change process of step 6, for each encoded data IP packet in the encoded data IP packet group with redundant data, an ID for identifying each unit, which is a unit for changing the transmission order, ID for identifying the number of coded data IP packet groups with redundant data and which coded data IP packet or redundant data coded IP packet belongs to which coded data IP packet group with redundant data (FIG. 10). In the example, an IP header in which “symbol 1-1”, “symbol 2-1”,..., “Redundant PM” corresponds to this ID) is added. In the transmission process, the transmission terminal 1 continuously transmits IP packets by connectionless communication (step 7).

  The receiving terminal 2 that receives the IP packet transmitted from the transmitting terminal 1 refers to the ID included in the IP header and generates a coded data IP packet group with redundant data in the original order. For example, a buffer is provided for each encoded data IP packet group with redundant data in the unit, and the encoded data IP packet group with redundant data in the original order is generated by filling the buffer according to the ID included in the IP packet. To do. When the IP packet of a new unit is received, the number of consecutive packet losses in the previous unit can be calculated. That is, since the number of packets to be received in one unit is known from the ID, the number of packet losses can be calculated from the number of packets and the number of packets actually received. The receiving terminal 2 sends this value to the transmitting terminal 1 (step 8).

  The transmitting terminal 1 receives this value, determines the number (P) of coded data IP packet groups with redundant data included in the unit whose transmission order is changed based on this value, and changes the transmission order in units of the unit. Then, the IP packet is transmitted (step 6).

  In addition, the receiving terminal 2 that has received the IP packet transmitted from the transmitting terminal 1 performs encoded data restoration processing (step 9). Here, restoration is performed in units of coded data IP packet groups with redundant data. First, when the encoded data IP packet does not have a packet loss, only encoded data is extracted from the encoded data IP packet group with redundant data to generate complete encoded data.

  If the encoded data has lost packets, but the number of losses is equal to or less than the maximum number of recoverable loss, recovery is performed in Reed-Solomon code bit units (for example, 8 bit units), and the recovered data is combined. Thus, the complete encoded data is restored. In cases other than the above, incomplete encoded data is generated by extracting only encoded data from the encoded data IP packet group with redundant data.

  Next, the receiving terminal 2 divides the encoded data (see FIG. 5) composed of a plurality of MPEG2-TS data, extracts the individual MPEG2-TS data, performs the decoding process, and outputs to the HD compatible TV monitor 5. Is displayed (step 10). If the encoded data is incomplete, it is not necessary to display a frame including the encoded data.

(When going through a video communication server)
Now, in addition to performing direct communication between the transmitting terminal 1 and the receiving terminal 2 via the Internet 3 as described above, as shown in FIG. 11, the video communication is performed via the video communication server 6. Is also possible.

  In the example illustrated in FIG. 11, the transmission terminal 1 and the reception terminal 2 have the same functional configuration as that illustrated in FIG. 1, and the video communication server 6 has only a function of relaying communication between the transmission terminal 1 and the reception terminal 2. Alternatively, the transmission terminal 1 simply sends the encoded data IP packet to the video communication server 6, and the video communication server 6 performs data redundancy, grouping, and transmission order change processing to the reception terminal 2. The encoded data may be transmitted.

  As described above, by using the transmission order changing technique described in the present embodiment, it is possible to perform error correction correctly and restore a packet even if consecutive packet losses occur on the Internet.

  In addition, the number of encoded data IP packet groups with redundant data used for the transmission order change is calculated using the number of consecutive packet losses, so the number of encoded data IP packet groups with redundant data can be minimized. , The delay associated with the transmission order change can be optimized.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made within the scope of the claims. For example, in the present embodiment, video / audio encoded data is taken as an example, but the present invention can also be applied to an audio-only application such as an IP phone. In this embodiment, Reed-Solomon coding is used as an example of an error coding method. However, this method is also applied to parity coding, hamming coding, BCH coding, and the like, which are methods for adding other redundant data. The invention can be applied.

It is a system configuration figure in an embodiment of the invention. 2 is a functional configuration diagram of a transmission terminal 1. FIG. 3 is a functional configuration diagram of a receiving terminal 2. FIG. It is a flowchart which shows the flow of a process in the case of delivering encoded data from the transmission terminal 1 to the receiving terminal 2. It is a figure which shows an example of an encoding data IP packet. It is a figure for demonstrating a Reed-Solomon code | symbol. It is a figure for demonstrating a Reed-Solomon code | symbol. It is a figure which shows the example of the encoding data IP packet group containing K encoding data IP packets. It is a figure for demonstrating the production | generation processing method of a redundant data IP packet group. It is a figure for demonstrating the method of rearrangement of a transmission order. It is a figure which shows embodiment which communicates via the video communication server.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission terminal 2 Reception terminal 3 Internet 4 HD camera with a video encoding function 5 HD-compatible TV monitor 6 Video communication server 11 Encoded data reception unit 12 Packet group generation processing unit 13 IP packet transmission order change processing units 14 and 22 Transmission unit 15, 21 Reception unit 23 Continuous packet loss number measurement processing unit 24 Encoded data restoration processing unit 25 Encoded data decoding / display processing unit

Claims (10)

Encoded data packet generating means for generating encoded data packets for network transmission from encoded data obtained by encoding video or audio;
Encoded data packet group generation means for generating an encoded data packet group from a predetermined number of consecutive encoded data packets; and
Generating a redundant data packet group including one or a plurality of redundant data packets for performing error correction on the encoded data packet in the encoded data packet group, the redundant data packet group and the encoded data packet group; And an encoded data packet group generation unit with redundant data for generating an encoded data packet group with redundant data, and
The transmission order of the packets in the coded data packet group with redundant data for a predetermined number is changed, and the transmission order is changed so that the packets in the coded data packet group with redundant data are sent to the network in the changed order. A data transmission apparatus comprising: a transmission unit.   The encoded data packet group generation unit with redundant data, when generating the redundant data packet, divides each packet of the encoded data packet group from the beginning for each predetermined number of bits, One or a plurality of redundant bit strings are calculated from a set of bit strings at the same position from the head in a plurality of packets constituting the data, and one or more redundant packets having the same length as the encoded data packet are combined by combining them. The data transmission device according to claim 1, wherein a plurality of data transmission devices are generated.   The transmission order changing transmission means calculates the predetermined number based on the number of consecutive packet losses in the network and the maximum number of packets that can be recovered by error correction even if lost in one encoded data packet group with redundant data. The data transmission device according to claim 1, wherein:   The data transmission apparatus according to claim 3, wherein the transmission order change transmission means sets the predetermined number to a value equal to or greater than a value obtained by dividing the number of consecutive packet losses by the maximum number of packets that can be restored. .   The transmission order changing transmission means transmits one packet in one encoded data packet group with redundant data in the predetermined number of consecutive encoded data packet groups with redundant data, and then The data according to any one of claims 1 to 4, wherein the packet is transmitted by repeating transmission of one packet in a group of encoded data packets with redundant data in the following order. Transmitter device. Receiving means for receiving a plurality of packets including encoded data packets generated from encoded data obtained by encoding video or audio from a data transmission device via a network;
A continuous packet loss number notifying means for measuring the number of packets continuously lost in the network from the number of packets to be received and the number of packets actually received, and notifying the number to the data transmission device;
One or more redundant data packets attached to an encoded data packet group made up of a plurality of encoded data packets and an encoded data packet group with redundant data made up of the encoded data packet group are received Reconstructing means for recognizing from a plurality of packets and restoring the encoded data packet by error correction when there is a lost encoded data packet in the encoded data packet group with redundant data;
A data receiving apparatus comprising: output means for decoding encoded data and outputting the decoded data. A data transmission method executed by a data transmission apparatus having a function of transmitting data via a network,
An encoded data packet generating step for generating an encoded data packet for network transmission from encoded data obtained by encoding video or audio;
An encoded data packet group generation step for generating an encoded data packet group from a predetermined number of consecutive encoded data packets; and
Generating a redundant data packet group including one or a plurality of redundant data packets for performing error correction on the encoded data packet in the encoded data packet group, the redundant data packet group and the encoded data packet group; And an encoded data packet group generation step with redundant data for generating an encoded data packet group with redundant data, and
The transmission order of the packets in the coded data packet group with redundant data for a predetermined number is changed, and the transmission order is changed so that the packets in the coded data packet group with redundant data are sent to the network in the changed order. A data transmission method comprising: a transmission step. A data receiving method executed by a data receiving device having a function of receiving data via a network,
Receiving means for receiving a plurality of packets including encoded data packets generated from encoded data obtained by encoding video or audio from a data transmission device via a network;
A continuous packet loss number notifying means for measuring the number of packets continuously lost in the network from the number of packets to be received and the number of packets actually received, and notifying the number to the data transmission device;
One or more redundant data packets attached to an encoded data packet group made up of a plurality of encoded data packets and an encoded data packet group with redundant data made up of the encoded data packet group are received A recovery step that identifies from a plurality of packets and restores the encoded data packet by error correction when there is a lost encoded data packet in the encoded data packet group with redundant data;
An output step of decoding encoded data and outputting the decoded data. A data receiving method comprising: Computer
Encoded data packet generating means for generating encoded data packets for network transmission from encoded data obtained by encoding video or audio;
Encoded data packet group generation means for generating an encoded data packet group from a predetermined number of consecutive encoded data packets;
Generating a redundant data packet group including one or a plurality of redundant data packets for performing error correction on the encoded data packet in the encoded data packet group, the redundant data packet group and the encoded data packet group; And an encoded data packet group generation means with redundant data for generating an encoded data packet group with redundant data.
The transmission order of the packets in the coded data packet group with redundant data for a predetermined number is changed, and the transmission order is changed so that the packets in the coded data packet group with redundant data are sent to the network in the changed order. Transmission means,
Program to function as. Computer
Receiving means for receiving a plurality of packets including encoded data packets generated from encoded data obtained by encoding video or audio from a data transmitting apparatus via a network;
A continuous packet loss number notifying means for measuring the number of packets continuously lost in the network from the number of packets to be received and the number of packets actually received, and notifying the number to the data transmission device;
One or more redundant data packets attached to an encoded data packet group made up of a plurality of encoded data packets and an encoded data packet group with redundant data made up of the encoded data packet group are received Reconstructing means for recognizing the encoded data packet by error correction when there is a lost encoded data packet among the encoded data packet group with redundant data identified from a plurality of packets,
Output means for decoding the encoded data and outputting the decoded data;
Program to function as.

Images