CN110545294B

CN110545294B - IP data encapsulation method, restoration method and system applied to IPover DVB transmission

Info

Publication number: CN110545294B
Application number: CN201911011335.2A
Authority: CN
Inventors: 贾旭光; 邢胜帅; 宋佳
Original assignee: Six Zhida Beijing Technology Co ltd
Current assignee: Six Zhida Beijing Technology Co ltd
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2021-08-03
Anticipated expiration: 2039-10-23
Also published as: CN110545294A

Abstract

The patent relates to the technical field of data transmission, and particularly discloses an IP data encapsulation method applied to IP over DVB transmission, which comprises the following steps: step 1, obtaining an IP data frame from an Ethernet data frame; step 2, sequentially splitting the IP data frame into a plurality of data loads, and sequentially encapsulating the data loads into TS stream data; the invention also correspondingly discloses an IP data reduction method and an IP transparent transmission system for IP over DVB transmission. The invention solves the technical problem of overhigh protocol overhead required by IP over DVB transmission in the prior art, and realizes the transparent transmission of IP data which can be applied to transmission systems such as DVB, DTMB and the like by using smaller protocol overhead.

Description

IP data encapsulation method, restoration method and system applied to IPover DVB transmission

Technical Field

The invention relates to the technical field of data transmission, and particularly discloses an IP data encapsulation method, a recovery method and a system applied to IP over DVB transmission.

Background

DVB (Digital Video Broadcasting) is a set of Digital television standards established in europe. The DVB system supports audio video transmission in a ts (transport stream) stream format. The TS stream is a standard format for storing and transmitting audio-video data. Most of the conventional wireless image transmission systems adopt TS streams as standard formats, and TS packets (packets) in the TS streams are fixed to 188 bytes in length, and include a header of 4 bytes and a data payload of 184 bytes. The Packet header includes information such as a sync byte 47, a Packet PID (Packet Identifier), and a Packet continuity count.

The DVB system only supports TS stream transmission and cannot meet the requirement of transmitting IP (Internet Protocol) data. ETSI (European Telecommunications Standards Institute) proposes several schemes for IP over DVB, encapsulating IP data into TS streams. Common Encapsulation formats are MPE (Multi-Protocol Encapsulation) and ule (unidirectional light Encapsulation). The MPE encapsulation process is to encapsulate IP Data into PDU (Protocol Data Unit), and then further encapsulate the PDU (Sub Network Data Unit) into an SNDU (Sub Network Data Unit) according to DSM-cc (digital Storage Media Command and control) format. The SNDU consists of three parts, a header, a payload and a trailer check, where the header occupies 12 bytes and the trailer occupies 4 bytes. And then packaging the SNDU as data load into TS stream. The MPE encapsulation is shown in figure 1. ULE packaging is a simplification. The PDU unit is directly mapped into the transmission data load, thereby reducing the protocol overhead and the encapsulation flow. And the address field NPA of the ULE header may be configured to be optional, thereby reducing the packet header length of the ULE to 4 bytes. The ULE encapsulation is shown in fig. 2. In any case, finally, the data payload in the received TS packet may be reconnected to the IP data frame in sequence according to the transmission specification of the TS stream data.

In addition, for the second generation DVB standard, ETSI also proposes a new gse (general Stream encapsulation) encapsulation mode for IP data transmission. The method abandons the encapsulation form of 188 bytes fixed by TS stream, directly maps GSE to a physical transmission layer, the GSE packet header is fixed 4 bytes, and the rest domains are all selectable. The GSE packaging approach is shown in fig. 3.

The three IP data conversion modes have the highest GSE efficiency, but the conversion mode abandons the TS stream encapsulation mode and only supports the second generation DVB standard physical layer data frame, which has great limitation. MPE and ULE support TS stream mode encapsulation, ULE is more efficient than MPE, the minimum header only occupies 4 bytes, and in addition, 4 bytes of a TS stream packet header still has larger redundancy and improvement space.

Disclosure of Invention

One aspect of the present invention is to provide an IP data encapsulation method, a recovery method, and a system for IP over DVB transmission, so as to solve the technical problem in the prior art that the protocol overhead required by IP over DVB transmission is too high.

The IP data encapsulation method applied to IP over DVB transmission in the scheme comprises the following steps,

step 1, obtaining an IP data frame from an Ethernet data frame;

step 2, sequentially splitting the IP data frame into a plurality of data loads, and sequentially encapsulating the data loads into TS stream data;

the length of TS packets in the TS stream data is 188 bytes, and the packet header of each packet is a uniform synchronous byte;

when the length of the IP data frame is greater than 186 bytes, encapsulating the first 185 bytes of the IP data frame as a frame header in a first packet, wherein the values of the second and third bytes of the first packet represent the frame length of the IP data frame;

the rest bytes of the IP data frame are sequentially encapsulated into a plurality of continuous intermediate packets in a 186/packet mode, and the rest bytes are all encapsulated into a tail packet until the number of the rest bytes of the IP data frame is less than or equal to 186;

the second byte of the middle packet is a 16-system number 06;

the second byte of the tail packet is a 16-system number 07, and the part of the tail packet less than 188 bytes is filled by padding bytes;

when the length of the IP data frame is less than 187 bytes, encapsulating the IP data frame in a short frame packet;

the value of the second byte of the short frame packet represents the frame length of the IP data frame

The short frame packet is less than 188 bytes filled by fixed padding bytes.

Further, the sync byte is a hexadecimal number 47.

Further, the fixed stuff byte is a hexadecimal number FF.

Further, step 1 also includes step 11: and counting the length of the IP data frame to obtain the frame length information of the IP data frame.

Further, step 1 also includes step 12: and caching the IP data frame and the length information thereof in the RAM.

Further, step 2 encapsulates the IP data frame as follows:

step 21: reading frame length information from an RAM, generating different packet header information according to different frame lengths, wherein the first packet header comprises a synchronous byte and a frame length, the frame length is larger than 186 bytes, the frame length occupies two bytes, and the frame length is smaller than or equal to 186 bytes, and the frame length occupies 1 byte; if the frame length is not the first packet, the frame length is not written, and the hexadecimal number 06 is written in the next byte of the synchronous byte;

generating a packet header each time, and reducing the number of the remaining bytes of the IP data frame from the frame length 186 each time, if the frame is the first packet, reducing 185;

step 22: after the generation of the packet header information is finished, sequentially reading IP data from the RAM and filling the IP data into TS packet data with the length of 188 bytes, and skipping to step 21 when the number of remaining bytes of the current IP data frame exceeds 186 bytes to continue executing the generation process of the TS packet; skipping to step 23 when the remaining IP data is less than 186 bytes which is not enough to fill one complete TS stream packet;

and step 23, filling fixed padding bytes in the rest part to form a complete TS packet.

According to the definition of the method, the numerical value represented by the second byte and the third byte of the first packet is directly the length value of the IP data frame, according to the IP transmission specification, the length of one IP data frame in the Ethernet is not more than 1500 bytes at most, the conversion into a 16-system number is 05DC, and further, if two bytes are used for representing the frame length, the first byte is certainly less than 06, so that as long as the next byte behind the synchronization byte is more than 05, the byte is certainly not used for representing the length value of the IP data frame; on the other hand, the length of an IP data frame is at least 60 bytes, and the short frame packet uses one byte to represent the frame length of the IP data frame, so according to the previous definition of the short frame packet, the value of the second byte of the short frame packet must be as large as 07 which is smaller than 187 (16-system BB). Thus, the first packet, the middle packet, the last packet and the short frame packet defined in the invention can be completely distinguished by adopting two specific values of 06 and 07 to represent the middle packet and the last packet, and adopting two judgment conditions of less than 06 and more than 07, and the required protocol overhead only needs 2-3 bytes per packet.

Another aspect of the present invention provides an IP data recovery method for IP over DVB transmission, comprising the following steps:

step A: acquiring the TS stream data;

and B: performing packet synchronization on the TS stream data by using a limitation condition that a synchronous byte and a byte which is 187 bytes apart from the synchronous byte should be the synchronous byte;

and C: searching IP data frame header and frame length information and identifying each packet in the TS stream, wherein the process comprises the following steps: detecting the value of the next byte after the sync byte;

the byte value less than 06 is the first packet, and the frame length is the value of the byte and the next byte;

if the byte value is more than 07, the short frame packet is obtained, and the length is the value of the next byte;

a tundish equal to 06 and a tail-packet equal to 07;

step D: filtering the packet header and the padding in the TS packet to obtain all effective data of the IP data frame;

step E: and sequentially connecting the effective data to obtain a restored IP data frame.

Further, in the step B, a secondary synchronization mode is adopted to synchronize the TS stream, and the synchronization process is as follows: detecting a received TS stream, entering a pre-synchronization state when a data synchronization byte is received, resetting a counter and starting counting, detecting whether the received data is still a synchronization byte when the data is counted to 187, entering a secondary synchronization state if the data is still the synchronization byte, and jumping back to the pre-synchronization state if the data is not the synchronization byte;

when the counter is cleared again and continues counting in the secondary synchronization state and the counter is accumulated to 187 again, the synchronization is completed if the received data is a synchronization byte, otherwise, the pre-synchronization is skipped, and the synchronization process is restarted.

Further, after the synchronization in the step B is completed, filtering out null packets that may be inserted into the transmitting system.

Further, the step E includes writing the filtered TS header and the filled IP data into the RAM in sequence, and executing output when the length of the data stored in the RAM reaches the frame length of the frame represented by the frame length information.

According to the definition of the aforementioned encapsulation method, the numerical value represented by the second and third two bytes of the first packet is directly the length value of the IP data frame, according to the IP transmission specification, the length of an IP data frame in the ethernet does not exceed 1500 bytes at most, and is converted into a 16-system number which is 05DC, and further if two bytes are used to represent the frame length, the first byte is certainly less than 06, so as long as the next byte after the sync byte is greater than 05, the byte is certainly not used to represent the length value of the IP data frame; on the other hand, the length of an IP data frame is at least 60 bytes, and the short frame packet uses one byte to represent the frame length of the IP data frame, so according to the previous definition of the short frame packet, the value of the second byte of the short frame packet must be as large as 07 which is smaller than 187 (16-system BB). Thus, the first packet, the middle packet, the last packet and the short frame packet defined in the invention can be completely distinguished by adopting two judgment conditions of less than 06 and more than 07, and the required protocol overhead only needs 2-3 bytes per packet.

Yet another aspect of the present invention provides an IP transparent transmission system, including: a transmitting end and a receiving end;

the transmitting end comprises a transmitting end and a receiving end,

an IP-to-TS module for receiving IP data frames from Ethernet and performing the aforementioned IP data encapsulation method applied to IP over DVB transmission to encapsulate the IP data into TS stream,

a transmitter for transmitting the TS stream encapsulated by the IP to TS module;

the receiving end comprises a receiving end and a transmitting end,

a receiver for receiving the TS stream from the transmitter;

the TS-to-IP module is used in the IP data reduction method applied to IP over DVB transmission, and reduces the received TS stream into an IP data frame, and sends the IP data frame into an ethernet in the form of an ethernet data frame.

The IP data encapsulation method, the restoration method and the system applied to the IP over DVB transmission realize the mutual conversion of the IP data and the TS stream, only occupy 2 to 3 bytes compared with MPE and ULE schemes, greatly reduce the protocol overhead, have the encapsulation format of fixed 188 bytes of the TS stream compared with GSE, support various standards of the existing DVB, DTMB and the like, directly encapsulate the MAC layer data, support IPV4 and IPV6, have simple encapsulation mode, are easy to realize chips such as FPGA and the like, and can realize high-efficiency transparent transmission of the IP data in the systems such as DVB, DTMB and the like.

Drawings

FIG. 1 is a schematic diagram of MPE encapsulation in the prior art;

FIG. 2 is a schematic diagram of a ULE packaging approach in the prior art;

FIG. 3 is a schematic diagram of a prior art GSE packaging approach;

FIG. 4 is a flow chart of the steps for converting IP data into TS stream data in an embodiment of the present invention;

fig. 5 is a schematic diagram of TS stream data encapsulated by IP data provided in an embodiment of the present invention;

FIG. 6 is a flowchart illustrating steps for reducing TS streams to IP data according to an embodiment of the present invention;

fig. 7 is a logic block diagram of an IP data transparent transmission system according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail below by way of specific embodiments:

the embodiment shows an IP data encapsulation method applied to IP over DVB transmission, where IP data in the embodiment is accessed through an ethernet.

As shown in fig. 4, the encapsulation process for converting IP data into TS stream in this embodiment is as follows:

step 101: and an Ethernet data preprocessing step, namely removing a preamble and an FCS field from an Ethernet data frame obtained from an Ethernet physical layer PHY chip to obtain an IP data frame, counting the frame length of the IP data frame, and generating signals such as IP data validity, frame tail indication and the like.

Step 102: an IP data frame caching step, wherein the IP data and the frame length information of the IP data are stored in an RAM, and the next step (step 103) is executed when a complete IP data frame is stored in the RAM;

it should be noted that the frequency of the TS stream clock at the later stage is usually lower than that of the ethernet interface clock, that is, the RAM reading speed is lower than the writing speed, so that the RAM depth needs to be increased according to the throughput in a specific application to prevent data loss caused by overflow.

Step 103: and a step of generating a TS packet header, namely reading IP frame length information from the RAM, and generating different packet header information according to different frame lengths.

In this embodiment, the IP data frames are divided into two types, a long frame and a short frame, according to the difference in the length of the IP data frames, where a frame length (including no FCS) is greater than 186 bytes for a long frame and a frame length smaller than 187 for a short frame. As shown in fig. 5, in this embodiment, different packing schemes are adopted for the long frame and the short frame, the long frame needs to be packed in a plurality of TS packets, and the TS packets for packing the long frame are further divided into a head packet including a head of the long frame, a middle packet including middle data of the long frame, and a tail packet including a tail of the long frame.

The format of the head packet header is that the synchronous byte 47 plus the length value (16 system) of 2 bytes totally occupies 3 bytes;

a synchronous byte 47 in a tundish packet header format reinforces a fixed character 06, and occupies 2 bytes;

a tail packet header format synchronous byte 47 reinforces a fixed character 07, and occupies 2 bytes; the short frame can be transmitted only by one TS packet, the packet header format is that the length value of 1 byte is added to the synchronous byte 47, and 2 bytes are occupied;

in this step, a header is generated each time, and the remaining number of bytes of the IP data frame is reduced 186 each time from the frame length (2 bytes occupied by the header sync byte 47 and the fixed character are subtracted from the length 188 bytes of the TS packet), and reduced 185 if the frame is the first packet (3 bytes occupied by the header sync byte 47 and the length value are subtracted from the length 188 bytes of the TS packet).

Step 104: and a step of generating packet data, namely sequentially reading IP data from the RAM and filling the IP data into TS packet data with the length of 188 bytes after the packet header information is generated according to different frame lengths. If the remaining byte number of the current IP data frame exceeds 186 bytes, the process jumps to step 103 to continue the TS packet generation process. The step 105 is skipped when the remaining IP data is less than 186 bytes which is not enough to fill one complete TS stream packet.

Step 105: and a step of filling redundancy, namely filling fixed byte hexadecimal FF in the residual part to obtain a complete TS packet with the length of 188 bytes, and completing the whole process of converting the IP data frame into the TS stream.

Step 106: the generated TS stream data can be sent out through a transmission system such as DVB and DTMB supporting TS stream transmission.

Correspondingly, the embodiment also discloses an IP data recovery method applied to IP over DVB transmission.

As shown in fig. 6, a specific process of restoring TS stream data obtained by the encapsulation method in this embodiment to IP data is as follows:

step 201: and a TS stream data input step, namely demodulating the signals sent by the transmission system to obtain TS stream data.

Step 202: and a step of packet synchronization and empty packet filtering, namely synchronizing TS stream data, and synchronizing the TS stream in a secondary synchronization mode, wherein the synchronization process comprises the following steps: detecting the received TS stream, entering a pre-synchronization state if the received data is in hexadecimal 47, resetting the counter and starting counting, detecting whether the received number is still 47 when the count reaches 187, entering a secondary synchronization state if the number is 47, and jumping back to the pre-synchronization state if the number is not 47. When the counter is cleared again and continues to count in the secondary synchronization state and the counter is accumulated to 187 again, synchronization is completed if the received data is 47, otherwise, pre-synchronization is skipped, and the synchronization process is restarted. After the synchronization is completed, empty packets possibly inserted in the transmitting system are filtered.

Step 203: and a step of acquiring an IP frame header and length, namely searching IP data frame header and frame length information in the TS after filtering the null packet, wherein the searching process is to judge the next byte after the synchronous byte 47, the byte value smaller than 06 is a long frame initial packet according to the definition of the step 103, and the length is the value of the byte and the next byte. If the length is more than 07, the short frame packet is obtained, and the length is the value of the next byte. Equal to 06 is a tundish and equal to 07 is a trailer.

It is to be noted that, in this embodiment, according to the definition of step 103, the numerical values represented by the second and third two bytes of the long frame header packet are directly the length value of the IP data frame, according to the IP transmission specification, the length of an IP data frame in the ethernet is not more than 1500 bytes at most, and is converted into a 16-ary number, that is, 05DC, and further, if two bytes are used to represent the frame length, the first byte is certainly less than 06, so as long as the next byte after the sync byte 47 is greater than 05, the byte is certainly not used to represent the length value of the IP data frame; on the other hand, the length of an IP data frame is at least 60 bytes, and the short frame packet uses one byte to represent the frame length of the IP data frame, so according to the previous definition of the short frame packet, the value of the second byte of the short frame packet must be as large as 07 which is smaller than 187 (16-system BB). Thus, the 0607 specific values are adopted to represent the middle packet and the tail packet, and the two judgment conditions of less than 06 and more than 07 are adopted, so that the first packet, the middle packet, the tail packet and the short frame packet defined in the invention can be completely distinguished, and the required protocol overhead only needs 2-3 bytes per packet.

Step 204: and a step of filtering the TS packet header and filling, wherein after frame header and frame length information is obtained, the packet header and filling in the TS packet are filtered, and all effective data of the IP data frame can be obtained.

Step 205: and generating an IP data frame, namely sequentially writing the filtered TS packet header and the filled IP data into an RAM, and executing reading when a complete IP data frame is stored in the RAM, namely when the length of the stored data reaches the frame length of the frame represented by the frame length information.

Step 206: and a step of generating Ethernet data, which is to add information such as a frame preamble and FCS to an IP data frame to generate the Ethernet data.

It should be noted that, according to the transmission specification of TS stream data, the sequence of TS packets is not disturbed, and therefore, the IP data in each TS packet is sequentially written into the RAM according to the receiving timing sequence, so that the required IP data frame can be restored. In addition, in this embodiment, the TS packets in the TS stream are generated one by one, and correspondingly, the TS packets are also read sequentially in a serial manner during restoration, which is only a non-limiting embodiment of the present invention.

It should also be known from the TS streaming and DVB specifications that all TS packets are transmitted and received serially in the same channel (frequency band), which also means that IP data frames are transmitted and received serially; and the length of the TS packet is fixed to 188 bytes, so that the TS packet synchronization can be realized only by a restriction condition that a unified header synchronization byte 47 and a byte which is 187 bytes apart from 47 still should be 47 (in step 202, if the received data is hexadecimal 47, the received data enters a pre-synchronization state, a counter is cleared and starts counting, and if the counted data reaches 187, whether the received data is still 47 is detected, if 47, the received data enters a secondary synchronization state, otherwise, the received data jumps back to the pre-synchronization state.), and each IP data frame can be distinguished separately by matching with frame length information (in step 205, when the length of the stored data reaches the frame length of the frame represented by the frame length information, a complete IP data frame is marked to be written completely).

The IP data encapsulation method applied to the IP over DVB and the corresponding recovery method thereof have the advantages of small protocol overhead (2-3 bytes per TS packet), adoption of the encapsulation scheme of 188 bytes of fixed TS stream, direct application to the existing DVB second generation and DTMB, DTMB-A and other communication systems, and realization of transparent transmission of IP data in the communication systems.

Taking DVB as an example, the embodiment further provides an IP transparent transmission system, as shown in fig. 7,

the transmitting end in the system comprises an IP to TS module, a data transmission module and a data transmission module, wherein the IP to TS module is used for receiving an IP data frame from an Ethernet and executing the IP data encapsulation method applied to IP over DVB transmission provided by the embodiment to generate and encapsulate IP data into TS streams, and DVB-TX is a DVB transmitter and is used for transmitting the TS streams encapsulated by the IP to TS module;

the DVB-RX included in the receiving end of the system is a DVB receiver and is used for receiving TS (transport stream);

the receiving end also comprises a TS-to-IP module which is used for executing the IP data reduction method applied to the IP over DVB transmission, reducing the received TS stream into an IP data frame and sending the IP data frame into the Ethernet in the form of the Ethernet data frame. In summary, compared with the existing MPE, ULE, and GSE encapsulation methods, the method and system provided in this embodiment have a simple protocol and a small number of occupied bytes, and can be applied to transmission systems such as DVB and DTMB to implement transparent transmission of IP data.

The foregoing is merely an example of the present invention and common general knowledge of known specific structures and features of the embodiments is not described herein in any greater detail. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.

Claims

1. An IP data encapsulation method applied to IP over DVB transmission is characterized by comprising the following steps,

step 1, obtaining an IP data frame from an Ethernet data frame;

the second byte of the middle packet is a 16-system number 06;

the value of the second byte of the short frame packet represents the frame length of the IP data frame;

the short frame packet is less than 188 bytes filled by fixed padding bytes.

2. The IP data encapsulation method applied to IP over DVB transmission according to claim 1, wherein: the sync byte is a hexadecimal number 47.

3. The IP data encapsulation method applied to IP over DVB transmission according to claim 1, wherein: the fixed stuff byte is a hexadecimal number FF.

4. The IP data encapsulation method applied to IP over DVB transmission according to claim 1, wherein: the step 1 also comprises a step 11: and obtaining the frame length information of the IP data frame by counting the length of the IP data frame.

5. The IP data encapsulation method applied to IP over DVB transmission according to claim 4, characterized in that: step 1 also includes step 12: and caching the IP data frame and the length information thereof in the RAM.

6. The IP data encapsulation method applied to IP over DVB transmission according to claim 5, characterized in that: in step 2, the IP data frame is encapsulated by the following steps:

step 22: after the generation of the packet header information is finished, sequentially reading IP data from the RAM and filling the IP data into TS packet data with the length of 188 bytes, and skipping to step 21 when the number of remaining bytes of the current IP data frame exceeds 186 bytes to continue executing the generation process of the TS packet; skipping to step 23 when the remaining IP data is less than 186 bytes which is not enough to fill a complete TS packet;

7. An IP data recovery method applied to IP over DVB transmission is characterized in that: the method comprises the following steps:

step A: obtaining TS stream data obtained according to the method of any one of claims 1 to 6;

a tundish equal to 06 and a tail-packet equal to 07;

8. The IP data recovery method applied to IP over DVB transmission according to claim 7, wherein: and B, synchronizing the TS stream in a secondary synchronization mode, wherein the synchronization process is as follows: detecting a received TS stream, entering a pre-synchronization state when a data synchronization byte is received, resetting a counter and starting counting, detecting whether the received data is still a synchronization byte when the data is counted to 187, entering a secondary synchronization state if the data is still the synchronization byte, and jumping back to the pre-synchronization state if the data is not the synchronization byte;

9. The IP data recovery method applied to IP over DVB transmission according to claim 7, wherein: and the step E comprises the steps of sequentially writing the filtered TS packet header and the filled IP data into the RAM, and executing output when the length of the data stored in the RAM reaches the frame length of the frame represented by the frame length information.

10. An IP transparent transmission system is characterized in that: the device comprises a transmitting end and a receiving end;

the transmitting end includes:

an IP to TS module, configured to receive an IP data frame from an ethernet and perform the IP data encapsulation method applied to IP over DVB transmission in any one of claims 1 to 6 to encapsulate IP data into a TS stream;

the receiving end includes:

a receiver for receiving the TS stream from the transmitter;

a TS-to-IP module, configured to perform the IP data recovery method applied to IP over DVB transmission in any one of claims 7 to 9, recover the received TS stream into an IP data frame, and send the IP data frame into an ethernet network in the form of an ethernet data frame.