JP2004007799A - Data transmission method and data processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data transmission method for enhancing immunity to errors in video audio transmission and recording. <P>SOLUTION: The data transmission method is characterized in that priority denoting order of processing is cross-referenced with data blocks of time serial data, one data block or more with lower priority and a data block with higher priority are set to the same packet and transmitted / recorded repetitively once or more, or the data block with higher priority is set to the packet and transmitted / recorded repetitively once or more. Or the data transmission method is characterized in that at least an arithmetic operation of error check or a correction code is applied to information included in a transmitted packet to add a new transmission header in zero byte or more to a head of the transmitted packet, and the arithmetic method of at least error check or correction code is revised depending on the type of data included in the transmitted packet before the arithmetic operation when the arithmetic result of at least error check or correction code is transmitted together with the data. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a data transmission method and a data processing method for improving the tolerance of transmission path errors and recording medium errors of video, audio, and data.

(4) Conventionally, in a recording field such as a CD, since a reproduced signal causes an error in a byte unit, a Reed-Solomon code which is an error correction code in a byte unit has been widely used. In the communication field, since an error occurs randomly in a transmission path, a BCH code, which is a random correction code, and a convolutional code are used. On the other hand, broadcasting, especially terrestrial broadcasting, has various disturbances, and is poor as a digital transmission path.

As described above, conventionally, these problems have been solved by error detection, correction codes, and retransmission for video and audio transmission path errors and recording medium errors. However, the use of error detection and correction codes enhances error detection and correction capabilities, but requires processing time. Also, when retransmission is performed, the delay due to retransmission cannot be ignored in a communication situation such as a radio where a propagation delay is large.

と し て As a conventional example, MPEG2 (error correction method is not standardized) is used in satellite broadcasting, and the processing procedure of the error correction coding method is as follows (supervised by Hiroshi Fujiwara: practical MPEG textbook, ASCII).

(1) A synchronization packet is added for each fixed-length data packet, and a synchronization byte is given a periodicity every eight packets (synchronous inversion) to facilitate synchronization.

(2) By performing energy diffusion, when the same pattern as the synchronization signal appears continuously in the data part, synchronization is prevented from being disturbed, and the frequency spectrum is averaged and dispersed (1 and 0 patterns are Be distributed evenly).

(3) Reed-Solomon (RS) is used for error correction (outer code).

(4) Spread errors by interleaving in order to enhance the error correction capability of Reed-Solomon (RS).

(5) Convolutional coding is used for inner code error correction (Viterbi decoding is used for decoding).

(4) The burst-like error that could not be corrected by the convolutional code is corrected efficiently by the RS code, which is a burst error correction code. In a terminal or a mobile terminal realized by software implementation, a considerable burden is imposed on the terminal due to error correction processing. In consideration of this point, it is desirable that the error detection or correction method can be changed according to the type of information (difference in media, header portion, data portion, etc.) and importance.

(4) The Internet is transmitted in packet units. If an error is detected in a packet, the packet is discarded (in the case of the Internet, it is called an IP (Internet Protocol) packet).

IP packets are designed on the assumption of a relatively high-speed transmission path, as transmission paths such as Ethernet are small, and only simple error detection is introduced. weak).

パ ケ ッ ト Also, when the transmission path is congested (congested), the packet is discarded at the relay terminal. As a method for improving the transmission quality by increasing the resistance to packet loss, a method of encoding voice data and a method of storing encoded data with different timestamps in the same packet and transmitting the same have been proposed (redundant). RTP (Realtime Transport Protocol) payload for audio data (data format): ("RTP Payload for Redundant Audio Data", RFC2198, Internet Engineering Task Force).

The problems are that it cannot be applied to video and that important information cannot be selectively and repeatedly transmitted as necessary. Furthermore, a method of transmitting the calculation result between packets as a transmission packet has been proposed (An RTP Payload Format for Generic Forward Error Correction, Internet Draft, Internet Engineering Task Force). .

Similarly, another problem is that important information cannot be selectively and repeatedly transmitted as necessary.

Ｈ As a transmission protocol considering mobile communication, H.264 223 (Multiplexing Protocol for Low Bitrate Multimedia Communication, Telecommunication Standardization Sector of ITU), depending on the type of media to be transmitted (video, audio, etc.). A method for changing error resilience has been proposed.

In particular, H. 223 Annex B proposes a method of copying header information of a previous transmission packet and transmitting the copied header information as an optional header of a header of a newly transmitted transmission packet in order to increase error tolerance of the header of the transmission packet. The header portion is protected by copying and transmitting the header portion. For the data portion, error resilience is enhanced by a method using error detection, error correction code (error detection by CRC (Cyclic Redundancy Check), error correction by convolutional code), and retransmission (H.223 Annex C).

Further, a system for performing different error correction coding according to the importance and priority of data has been proposed (error correction coding device, error correction decoding device, and communication system (Japanese Patent Application Laid-Open No. 9-116440), A signal transmission method, a communication device used for the signal transmission method, and a receiving device (Japanese Patent Laid-Open No. 7-336400).

In this method, the data for processing the error correction code can be suppressed to the minimum necessary, and the processing amount can be reduced as compared with the conventional method. However, the granularity (for example, for video, frame unit, GOB unit, etc., for video) associated with the priority is unknown or bit stream unit. In addition, since the method uses the error detection and the error correction code, there is a problem in the load for processing the error detection and the correction code in the terminal and the delay time required for the processing.

In the ATM (asynchronous transmission mode), a method has been proposed in which, when retransmitting an ATM cell packet, a plurality of copies of a packet to be retransmitted are transmitted a plurality of times. It is possible to improve the reliability by transmitting the same retransmission request a plurality of times (Makoto Ito, retransmission control method for MPEG2 video transmission on ATM network, IEICE IN97-67). Since all cell packets are retransmitted in response to a retransmission request, an increase in the number of retransmission requests causes an increase in transmission packets.

場合 Assuming the use of existing Internet protocols, it is difficult to fundamentally resolve error resilience because only the measures to be taken against packet loss can be discussed. On the other hand, a method for enhancing error resilience for IP (Internet Protocol) itself has been proposed (application of RS code and interleaving), and it has become possible to enhance error resilience for data transmission (errors). Application of large-scale multicast architecture with no error and forward error correction technology, IEICE (Research Institute of Information Technology SSE97-130).

However, strong error correction is not necessary for some media such as video, so by implementing error resilience according to the type of media transmitted in IP packets, the terminal that is generated for error detection and error correction can be used. Load and delay can be suppressed.

で は In the prior art, As in H.223, the coding system of the error correction code is changed or retransmitted according to the type of data to be transmitted (video, audio, text, etc.). However, although the error detection and correction capabilities are enhanced by enhancing the error detection and correction codes, the processing time is increased. Also, when retransmission is performed, the delay due to retransmission cannot be ignored in a communication situation such as a radio where a propagation delay is large. On the other hand, as a method that does not use retransmission, error detection, and correction codes, conventionally, audio data is encoded by a different encoding method and transmitted repeatedly, or a method of repeatedly transmitting a copy of a packet header portion, a retransmission method, or the like. A method of repeatedly transmitting packets to be transmitted has been proposed. However, since selective overlapping transmission has not been performed, the amount of overlapping transmission cannot be ignored in the case of transmission for video and audio.

In order to solve this problem, the present invention selectively and repeatedly stores the same data in different packets according to the priority, the frame type of the video, the encoding method, or the like, or repeatedly transmits and records the data in packet form. Resolve.

In other words, by using the priority of each encoded bit stream or the priority of each frame constituting the bit stream, data having high importance is selected, and the data is repeatedly transmitted and recorded with a time lag. The robustness against packet loss and data errors can be enhanced without unnecessarily increasing the amount. The present method may be applied not only to newly transmitted data packets but also to retransmitted data packets.

Conventionally, in the Internet, when an error is detected in a transmission packet, the transmission packet is discarded. By using a new error detection and correction coding scheme for a transmission packet, error resilience is enhanced, but the transmission format such as a transmission header is changed, and this point has not been considered in the conventional technology.

Therefore, in the present invention, error detection or correction code calculation is performed on information included in a transmission packet, a new transmission header is added to the head of the transmission packet, and the error detection or correction code calculation result is added. Transmit.

(4) By changing the method of calculating an error detection or error correction code in accordance with the information on the type of data included in a transmission packet, it is not necessary to provide excessive error resilience.

Also, in order to cope with various error detections and corrections, the identification information indicating that a function to perform error correction is added to the transmission packet and the type of the information can be identified by the transmission header so that the Internet protocol Diversify error resilience.

Specifically, on the Internet, if an error is detected using a simple checksum in a UDP (User Datagram Protocol) packet, the UDP packet is discarded. Although information is transmitted by IP packets, transmitted data is discarded from the viewpoint of reliability of transmission by using UDP (discarded as described above if there is an error in the packet) and TCP (Transmission Control Protocol: packet loss). (In the case of occurrence, retransmission processing is performed) (in the case of transmission, a UDP or TCP header and actual data follow in order after the IP header).

ＩＰ IP packets used on the Internet are transmitted via satellite Although the error correction capability of an IP packet can be enhanced by a method such as FEC (Forward Error Correction) or interleaving as in H.223, the transmission header is different from a conventionally used IP packet in the transmission format ( Format) and cannot be interpreted.

Therefore, according to the type of data to be transmitted, IP (Internet Protocol) itself is encapsulated (the IP packet is treated as data, and a new communication header is added to the head of the IP packet) to perform error correction coding. The error resilience of the Internet protocol is enhanced by enabling identification information indicating that a function of performing error correction is added to an IP packet and the type thereof to be identified by an IP header.

It should be noted that, for processing relating to error detection and correction, different schemes may be used for the communication header (IP, UDP, and TCP headers) and the data portion, or error detection and correction may not be used. .

方式 A method of performing different error correction coding according to the importance and priority of data has been proposed.

(4) As a result, data on which error correction code processing is performed can be suppressed to the minimum necessary, and the processing amount can be reduced as compared with the conventional method. However, the granularity (for example, for video, frame unit, GOB unit, etc., for video) associated with the priority is unknown or bit stream unit.

Therefore, by changing the method of error detection or error correction according to the priority corresponding to each frame of the video, the application range of the priority can be clarified, and the granularity of the application range can be reduced.

INDUSTRIAL APPLICABILITY The present invention is used in transmission lines requiring error tolerance such as wireless LAN, mobile phone, satellite communication, satellite broadcasting, xDSL (high-speed transmission line using telephone line), and CATV (cable TV). It is possible to include not only a transmitting / receiving terminal but also a relay device.

The data transmission method according to the present invention determines the number of transmissions of the data section based on a data section of time-series data related to video and / or audio and a priority indicating an order in which the data section is processed. The information on the determined number of transmissions and the data section are transmitted.

Further, the data processing method according to the present invention receives a data section of time-series data related to video and information indicating how many times the data section is repeatedly transmitted, and based on the information, It is characterized by performing a process of holding or discarding.

According to the present invention, it is possible to increase the error tolerance of video / audio transmission / recording while suppressing excessive transmission.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a transmission or recording format output by a data processing device.

Conventionally, as an error resilience method that does not use retransmission, error detection, and correction codes, the audio data is encoded using different encoding methods and transmitted repeatedly, a method that repeatedly transmits a copy of the packet header part, and repeatedly transmits a retransmission request And other methods have been proposed.

た め However, since selective overlapping transmission was not performed, the amount of overlapping transmission cannot be ignored in the case of transmission targeting video and audio. In order to solve this problem, the present invention selectively and repeatedly stores the same data in different packets according to the priority, the frame type of the video, the encoding method, or the like, or repeatedly transmits and records the data in packet form. Resolve.

According to the present invention, the resilience to packet loss and data errors is enhanced by repeatedly transmitting and recording packets with high importance at different times.

In the example of FIG. 1A, the data section (a) has a high importance and is stored together with each of the data sections (b), (c) and (d) in the same packet.

Note that the importance is a priority indicating the order of processing predetermined by the user (for example, a priority for each coded bit stream (data sequence of time-series data) or a frame (time Priority for each data segment of sequence data), frame type (intra-frame coding, inter-frame coding), coded header and coded data, coding method, identifier for identifying bit stream to be transmitted (for example, , RTP, a synchronization source identifier (SSRC) and a generated data amount.

The data division unit may be a video or audio frame unit, or a GOB unit or MB unit for video. If it is a voice, it may be a voiced section and a silent section.

The data section (a) may be packetized and repeatedly transmitted and recorded independently. Further, as shown in FIG. 1B, the same data section may be repeatedly stored in the same packet.

FIG. 1 (C) shows how to repeatedly transmit to the communication header of a packet transmitted before transmitting the repeatedly transmitted data section to notify the receiving side how many times the repeatedly transmitted data section is repeatedly transmitted. It describes the SN (serial number) of the packet to be transmitted and the number of times of repeated transmission.

(4) This information may be repeatedly described in some transmission packets (or may be a flag for notifying whether the same data is repeatedly transmitted).

Note that such information may be transmitted by a control protocol independently of data transmission as shown in FIG. 1 (D).

(1) The expression method in the example of FIG. 1 (D) indicates how many times data segments are repeatedly transmitted for information such as priority. In the example, the number of times of repeated transmission for the data section of “priority # 2” is set to three. This makes it easy for the receiving side to maintain and discard the data section.

As shown in FIG. 1E, when two or more data sections are stored in the same packet, information on at least one of the priority, frame type, and data type of the stored data section is stored in the packet. By describing, transmitting, and recording at the beginning, the content determination of the stored data section can be speeded up.

FIG. 2 is a diagram for explaining error resilience due to computation between packets. A priority indicating the order of processing is associated with a data section of data, and an operation (exclusive OR) is performed between two or more data sections according to the priority, and an operation result is transmitted. It can repair important packets. If one of the packet describing the operation result and the transmission packet can be received, the other lost packet can be restored. Since the priority is reflected, selective processing becomes possible as compared with the conventional invention, and excessive transmission can be suppressed.

FIG. 3 is a diagram showing the error resilience of the Internet protocol. In the Internet, when an error is detected in a transmission packet, the transmission packet is discarded. The use of a new error detection and correction coding scheme for a transmission packet enhances error resilience, but requires a new change in transmission format such as a transmission header. The prior art did not consider this point.

Therefore, error detection or correction code calculation is performed on the information included in the transmission packet, a new transmission header is added to the head of the transmission packet, and the result of the error detection or correction code calculation is transmitted together.

(4) By changing the method of calculating an error detection or error correction code in accordance with the information on the type of data included in a transmission packet, it is not necessary to provide excessive error resilience.

Also, in order to support various error detection and correction methods, the identification information indicating that a function to perform error correction is added to the transmission packet, and the type of the information can be identified by the transmission header, so that the Internet protocol Diversify error resilience.

In FIG. 3A, an error correction code is calculated for an IP packet, and a transmission header is added to the beginning of the IP packet (a simple transmission header checksum or error correction may be used only between two points. May be applied), when transmitting the operation result of the error correction code together, according to the type of data included in the IP packet, an error detection method (for example, parity, CRC, etc.) and an error correction code By changing the operation method (for example, BCH, Reed-Solomon, convolutional coding, Viterbi decoding, etc.), the type of data to be transmitted (video, audio, text, etc.) and the part of the transmission packet (header, payload) Enables error resilience to Internet protocols (identifiers and files that describe the error resilience scheme used in the Be provided grayed may notify a protocol between terminals).

Note that the PPP (Point-to-Point Protocol) transmission framework may be used to enhance the error tolerance of the PPP according to the type of data to be transmitted.

The determination of the data type is made based on the presence or absence of a RTP (Realtime Transport Protocol) transmission header in an IP packet or a predetermined transmission header (one uniquely defined by the user or a transmission protocol other than RTP) or a data type ( RTP is identified by the payload type).

In addition, IP packets used on the Internet are transmitted by satellite broadcasting, H.264. Although it is expected that the error detection and correction capabilities of the IP are enhanced by a technique such as FEC as in H.223, the format is essentially different from that of the IP.

Therefore, in FIG. 3B, the IP header is extended (the IPv6 can be dealt with by registering the extension header as an extension header), or the IP protocol type (IP datagram) is newly defined, so that the error tolerance of the IP is improved. Can be applied.

Ｈ As shown in FIG. In H.223, regarding the method of error detection and correction, different error detection and correction methods are introduced by distinguishing the header part and the payload part.

Regarding error correction for IP packets, error detection different for each part of the target information (header part (IP, UDP, TCP), transmitted data (UDP, TCP may be transmitted data)), and media Alternatively, an error correction technique may be introduced.

In addition, H. By transmitting the 223 transmission packet as transmission data of the IP packet, transparent communication with a communication environment not using IP becomes possible. As before, the IP protocol type is H. 223 needs to be newly defined.

By managing the IP address, telephone number, and port number of the Internet in association with each other, the correspondence between the terminals can be managed, and the Internet and the H.264 connection can be managed. 223 can be interconnected.

Finally, conventionally, a method of performing different error correction coding according to the importance and priority of data has been proposed. As a result, the amount of data on which error correction code processing is performed can be suppressed to the minimum necessary, and the processing amount can be reduced as compared with the conventional method.

{However, the granularity of the data with which the priority is associated (for example, a frame unit or a GOB unit for video) is unknown or a bit stream unit.

Therefore, by changing the method of error detection or error correction according to the priority corresponding to each frame of the video, the application range of the priority can be clarified, and the granularity of the application range can be reduced.

As described above, the data transmission method and the data processing method according to the present invention are useful methods having the effect of improving the error tolerance of video / audio transmission / recording.

(A)-(E) The figure which shows the transmission or recording format which the data processing apparatus in embodiment of this invention outputs. Diagram showing error resilience by operation between packets (A) to (C) are diagrams showing error resilience of the Internet protocol

Claims (11)

The number of transmissions of the data section is determined based on the data section of the time-series data related to video and / or audio, and the priority indicating the order in which the processing of the data section is performed. A data transmission method for transmitting data division. 2. The data transmission method according to claim 1, wherein the two or more data sections are received as a packet, and the information on the determined number of transmissions is described in a communication header of the packet. 3. The data transmission method according to claim 1, wherein the priority is determined by a priority of each coded bit stream and a priority of each frame forming the bit stream. 4. The data transmission method according to claim 1, wherein an error detection or error correction operation is selectively performed between the two or more data sections having the higher priority, and the operation result is transmitted. . 5. The data transmission method according to claim 4, wherein the operation is an exclusive OR operation. The data transmission method according to any one of claims 1 to 5, wherein the priority is determined according to a frame type indicating whether the encoding is intra-frame encoding or inter-frame encoding. . 7. The data transmission method according to claim 1, wherein a unit of the data division is a frame unit, a GOB unit, or a MB unit. (4) A data processing method for receiving a data section of time-series data related to video and information indicating how many times the data section is repeatedly transmitted, and holding or discarding the data section based on the information. 9. The method according to claim 8, wherein two or more of the data sections are received as a packet, and the information indicating how many times the data section is repeatedly transmitted is described in a communication header of the packet. Data processing method. The information indicating how many times the data section is repeatedly transmitted is determined in association with a priority indicating an order in which processing is performed between the data sections. Data processing method. 11. The data processing method according to claim 10, wherein the priority is determined based on a priority for each coded bit stream and a priority for each frame forming the bit stream.

Images