CN100348048C - Abnormal LDPC code to MPEG-2TS hierarchical inequality protection method - Google Patents

Abstract

The present invention provides an abnormal LDPC code to MPEG-2TS hierarchical inequality protection method, which relates to the technical field of digital information transmission and especially majorly protects an MPEG-2 TSS flow package head and an adaptation field. The present invention is characterized in that a protective processing circuit is added at the transmitting terminal of a communication system and the address of an information node with a higher abnormal LDPC code degree is stored at the transmitting terminal, which cause the MPEG-2 TSS flow package head and the adaptation field to be mapped to the information node with the higher abnormal LDPC code degree; a protective counter processing circuit is added at the receiving terminal of the communication system, and the address of the MPEG-2 TSS flow package head and the adaptation field is stored at the receiving terminal. The address is utilized to restore the MPEG-2TS code stream in normal order. The method causes the bit error rate (BIT) of important information between the MPEG-2 TSS flow package head and the adaptation field to decrease 1 to 2 orders of magnitude at the same signal-to-noise ratio, greatly raises the bit error resisting ability, and obviously improves the overall system performance.

Description

Abnormal LDPC code is to MPEG-2TS classification unequal error protection method

Technical field

The invention belongs to digital information transmission technical field, particularly utilize the packet header of the classification unequal error protection ability of abnormal LDPC code to the MPEG-2TS code stream, important informations such as adaptation field are laid special stress on protecting.

Background technology

The LDPC sign indicating number is a kind of linear code based on sparse check matrix, is proposed by Gallager in 1962, and its check matrix has sparse property.When the check matrix of LDPC sign indicating number can be represented with tanner figure, as Fig. 1, there be M node in the bottom of tanner figure, and each node is represented a check digit of code word, is called check-node; There is N node the top, and each node is represented an information bit, is called information node; The limit number that each node links to each other is called the degree of this node.

Can be divided into regular LDPC sign indicating number and abnormal LDPC code to the LDPC sign indicating number.

Gallager has provided the definition of regular LDPC sign indicating number the earliest, and the degree of its information node and check-node is a fixed value.The LDPC sign indicating number (being abnormal LDPC code) of constructing on non-regular tanner figure that studies show that of MacKay and Neal has superperformance.With respect to regular code, the number of degrees of information node and check-node are not fixing values among the tanner figure of abnormal LDPC code, have 2,3,4 three kinds as the degree of the information node of the abnormal LDPC code among Fig. 1.The degree availability distribution function of abnormal LDPC code (ρ (x), λ (x)) expression, pairing generating function can be defined as respectively:

$\mathrm{\ρ}\left(x\right)=\underset{i=2}{\overset{\max }{\mathrm{\Σ}}}{\mathrm{\ρ}}_i{x}^i$ $\mathrm{\λ}\left(x\right)=\underset{i=2}{\overset{\max }{\mathrm{\Σ}}}{\mathrm{\λ}}_i{x}^i$

Wherein x ' is the element of i for the generating function degree, ρ _iRepresent the probability that this abnormal LDPC code degree is the information node of i, λ _iRepresent the probability that this abnormal LDPC code degree is the check-node of i, and satisfy $\underset{i=2}{\overset{\max }{\mathrm{\Σ}}}{\mathrm{\ρ}}_i=1$ With $\underset{i=2}{\overset{\max }{\mathrm{\Σ}}}{\mathrm{\λ}}_i=1.$ The value of i adopts numerical optimization technique to obtain by Computing, search under corresponding constraints.

The SPA algorithm is generally adopted in the decoding of LDPC sign indicating number.The SPA algorithm can be divided into probability territory SPA algorithm and log-domain SPA algorithm again, and the two is of equal value from decoding algorithm.

Before providing log-domain SPA algorithm, introduce to give a definition: make H represent the check matrix of M * N, H _{I, j}The representing matrix meta is changed to (i, item j).The bit set that definition participates in m check equations is N (m)={ n:H _{M, n}=1}, comprise bit n verification and set be M (n).Definition N (m) n represent to remove bit n in N (m) set, M (n) m represent to remove verification and m in M (n) set.

Log-domain SPA algorithm:

Input: priori probability information $p_n^0=P(y_n=0)$ With $p_n^1=P(y_n=1)=1-p_n^0,n=1,\·\·\·,N;$ Output: hard decision is x={x1 as a result ..., xN};

Calculating process:

Initialization: to each n, calculating channel information $\mathrm{\&gamma;n}=\log (p_n^0/p_n^1);$ For each (m, n) ∈ (i, j) | Hi, j=1} calculates ${\mathrm{\&alpha;}}_{m,n}=\mathrm{sign}\left({\mathrm{\&gamma;}}_n\right)\log \left(\frac{1+e^{-\left|{\mathrm{\&gamma;}}_n\right|}}{1-e^{-\left|{\mathrm{\&gamma;}}_n\right|}}\right),$ Wherein $\mathrm{sign}\left({\mathrm{\&gamma;}}_n\right)=\left\{\begin{array}{cc}+1& {\mathrm{\&gamma;}}_n\&GreaterEqual;0\\ -1& {\mathrm{\&gamma;}}_n<0\&deg;\end{array}\right.$

Step 1 (level renewal): code check node processing step

To each m, n calculates

${\mathrm{\&beta;}}_{m,n}=\log \left(\frac{1+e^{-a}}{1-e^{-a}}\right)\underset{n^{\&prime;\&Element;}N\left(m\right)\backslash n}{\mathrm{\&Pi;}}\mathrm{sign}\left({\mathrm{\&alpha;}}_{m,n^{\&prime;}}\right)---\left(1\right)$

Wherein $\mathrm{\&alpha;}=\underset{n^{\&prime;}\&Element;N\left(m\right)\backslash n}{\mathrm{\&Sigma;}}\left|{\mathrm{\&alpha;}}_{m,n^{\&prime;}}\right|$

Step 2 (the vertical renewal): information node treatment step

To each m, n calculates

${\mathrm{\&alpha;}}_{m,n}=\mathrm{sign}\left({\mathrm{\&gamma;}}_{m,n}\right)\log \left(\frac{1+e^{-\left|{\mathrm{\&gamma;}}_{m,n}\right|}}{1-e^{-\left|r_{\mathrm{mn}}\right|}}\right)---\left(2\right)$

Wherein ${\mathrm{\&gamma;}}_{m,n}={\mathrm{\&gamma;}}_n+\underset{m^{\&prime;}\&Element;M\left(n\right)\backslash m}{\mathrm{\&Sigma;}}{\mathrm{\&beta;}}_{m^{\&prime;},n}.$

For each n, it is as follows to upgrade posteriority log-likelihood ratio (LLR) λ n:

${\mathrm{\&lambda;}}_n={\mathrm{\&gamma;}}_n+\underset{m\&Element;M\left(n\right)}{\mathrm{\&Sigma;}}{\mathrm{\&beta;}}_{m,n}---\left(3\right)$

Step 3: checking decoding ending standard

Hard decision: $X_n=\left\{\begin{array}{cc}0& {\mathrm{\&lambda;}}_n>0\\ 1& {\mathrm{\&lambda;}}_n\&le;0\end{array},n=1,\&CenterDot;\&CenterDot;\&CenterDot;,N.\right.$

If Hx=0 or reach maximum iteration time finishes decoding and the Hard decision decoding result is exported; Otherwise repeating step 1-3.

Variable α m in the above-mentioned algorithm, n and β m, n are called information and arrive the information node external information to check-node external information and verification.Need to prove, realize function in the above-mentioned algorithm at hardware $f\left(x\right)=\log \left(\frac{1+e^{-\left|x\right|}}{1-e^{-\left|x\right|}}\right)$ The operation of Shi Caiyong look-up table.

The excellent properties of LDPC sign indicating number and the applications well prospect in the information reliable transmission thereof (for example digital television transmission system, optical communication, satellite communication,, the 4th third-generation mobile communication system, at a high speed and very high speediness rate Digital Subscriber Line, light and magnetic-memory system etc.), caused the great attention of countries in the world academia and IT industry circle.

At present, the information source audio frequency and video compression section of main number television standard mainly is the MPEG-2TS standard that MPEG (Motion Picture Experts Group) proposes.It is further developing of MPEG-1, and code stream is 1.5～50Mb/s, is mainly used in video and digital audio transmission on satellite, cable and the microwave.MPEG-2TS stream is exactly Transmitting Stream, both transmission code stream.The length of TS stream is defined as 188 bytes, and PES (Packet Elementary Stream) is stored in the TS stream bag by segmentation and transmits.TS stream bag is divided into three parts, packet header, and adaptation field, payload, Fig. 2 are the MPEG-2TS flow structures, and Fig. 3 is a head-coating structure, and Fig. 4 is the adaptation field structure.MPEG-2TS stream format interoperability is good, is applicable to transmission.The importance of each Byte is different in the TS stream bag, and the packet header and the adaptation field of TS stream bag comprise a lot of important informations, than important many of payload (payload), as:

The sync_byte sync byte if make a mistake, will cause this TS packet loss, if cause system's lock-out, can cause a large amount of error codes.

The PID Packet Identifier is represented this TS bag type, if make a mistake, will cause this TS packet loss, if the PID of video (video) bag makes a mistake, becomes audio frequency (audio) bag and enters audio decoder, can cause a large amount of mistakes.

The PCR program clock reference for the MPEG-2TS decoder provides accurate timing, if make a mistake, will cause decoder buffer overflow or underflow.Cause a large amount of mistakes.

As seen, the packet header and the adaptation field information of MPEG-2TS stream are extremely important, should be laid special stress on protecting these important informations., in main number television transmission standard and other transmission standard, all the packet header and the adaptation field of MPEG-2TS stream are not laid special stress on protecting at present, cause the anti-error code capacity of these important informations relatively poor, thereby influenced the performance of system.

Summary of the invention:

The objective of the invention is to utilize the classification unequal error protection characteristic of abnormal LDPC code; a kind of frame head to video flowing with packet configuration is provided; packet header, the method that important informations such as adaptation field are laid special stress on protecting is to the packet header of MPEG-2TS stream and the method for adaptation field focused protection.

The invention is characterized in:

For communication system, this method increased the protection treatment circuit and realizes that this protection treatment circuit contains: controller (11) at the communication system transmitting terminal before the chnnel coding circuit; Counter (12) links to each other with controller (11); Identifier (13) links to each other with controller (13) synchronously, detects MPEG-2TS code stream packet header; Addressed memory (14) for input buffer (15) provides OPADD, and links to each other with controller (11); Input buffer (15) links to each other with addressed memory (14) with controller (11), and this input buffer (15) has MPEG-2TS code stream input and MPEG-2TS code stream output, output packet header and the adjusted MPEG-2TS code stream of adaptation field; In this protection treatment circuit, described guard method realizes according to following steps:

The address of the information node that step 1) is higher with the abnormal LDPC code degree is stored in the addressed memory (14);

Step 2) controller 1 control MPEG-2TS code stream enters input buffer (15) in proper order, and controller (11) starts synchronous identifier (13) and begins to catch step and catch the sync_byte sync byte simultaneously;

Step 3) is worked as synchronous identifier (13) and is captured sync_byte, in order to prevent the byte identical to occur in the TS stream payload with sync byte, detect sync_byte every 188 bytes, after being consecutively detected three subsynchronous bytes, think that synchronously, (13 offer controller (11) synchronizing signal to identifier synchronously;

After step 4) controller (11) obtained synchronizing signal, enabling counting device (12) count down to 188, MPEG-2TS stream bag just in this moment input buffer (15), and unison counter (12) offers controller (11) count signal;

Step 5) controller (11) starts input buffer (15) output, input buffer (15) beginning begins to export the MPEG-2TS code stream according to the address of the higher information node of abnormal LDPC code degree that addressed memory (14) is stored, the order of the MPEG-2TS code stream of being exported has been adjusted, TS stream packet header and the higher information node of the adjustment corresponding abnormal LDPC code degree in territory;

The controlled MPEG-2TS code stream of step 6) order is input to channel encoder through after encoding, and finishes the mapping to the higher information bit of abnormal LDPC code degree of packet header and adaptation field;

This method, increases the anti-treatment circuit of protection and realizes that this protects anti-treatment circuit to contain: controller (21) after the channel decoding circuit at receiving terminal of communication system; Counter (22) links to each other with controller (21); Addressed memory (23) provides MPEG-2TS code stream packet header and adaptation field address, and links to each other with controller (21); Input buffer (24) links to each other with addressed memory (23) with controller (21), and this input buffer (24) has MPEG-2TS code stream input, receive channel decoding circuit output code flow and MPEG-2TS code stream output, and output recovers the normal sequence code stream; At the anti-treatment circuit of described protection, described method realizes according to following steps:

MPEG-2TS is flowed packet header to step 1) and the adaptation field address is stored in the addressed memory (23);

Step 2) controller (21) control input buffer (24), the code stream of memory channel decoder output, and enabling counting device (22) counting are when counting down to 188, offer controller (22) count signal, what input buffer this moment (24) was stored is the adjusted MPEG-2TS code stream of order;

Step 3) controller (21) starts input buffer (24) output, exports according to the TS stream packet header and the adaptation field address of addressed memory (23) storage, and institute's output code flow is the MPEG-2TS stream of normal sequence just, realizes the recovery of MPEG-2TS stream.Abnormal LDPC code of the present invention is to the unequal error protection method of MPEG-2TS code stream, and to 4 bytes in packet header and preceding 16 bytes of adaptation field, totally 20 bytes are protected.The address of the information node that transmitting terminal addressed memory (14) storage abnormal LDPC code degree is higher.Receiving terminal addressed memory (23) store M PEG-2TS stream packet header and adaptation field address.

The inconsistency that the abnormal LDPC code degree distributes causes the difference of the anti-error code capacity of each information node.Analyze the SPA algorithm of LDPC decoding, soft decoding information is the iteration transmission between information node and check-node, and check-node provides soft decoding information for information node when vertical the renewal, and information node utilizes this soft information to decipher.When level was upgraded, this soft decoding information was returned to check-node by information node again, until the full detail node by correct decoding (if exceed maximum iteration time, then withdraw from iteration, and output decode results).As can be known, spend higher information node and link to each other with a plurality of check-nodes, and these a plurality of check-node apart from each others, these check-nodes can provide more soft decoding information to the higher information node of degree, through small number of iterations, but spend just correct decoding of higher information node, its anti-error code capacity is strong.On the contrary, spend less information node and link to each other with less check-node, the soft decoding information that less check-node provides is less, like this, it is less to spend the soft decoding information that less information node obtains, through after the iteration repeatedly, these information nodes also are difficult to correct decoding, its anti-error code capacity a little less than.Abnormal LDPC code has natural unequal error protection ability (Unequal Error Protection); in same abnormal LDPC code word; spend higher information node and have higher anti-error code capacity; spend lower information node and have less anti-error code capacity, and this unequal error protection ability increasing and decipher the minimizing of iterations and more and more significant along with signal to noise ratio.

We can utilize this unequal error protection ability that the important information of MPEG-2TS stream is protected; important informations such as packet header and adaptation field are mapped to the abnormal LDPC code degree than on the higher information node; improve the anti-error code capacity of these important informations, the error rate of important information is significantly reduced.

At system's transmitting terminal, before channel coding module, increase the protection treatment circuit.The address of the information node that system's storage abnormal LDPC code degree is higher, according to the different structure of selected abnormal LDPC code, institute of system address stored amount can be very little, even do not need to store the address of the higher information node of abnormal LDPC code degree.System detects the packet header and the adaptation field of MPEG-2TS bag from input MPEG-2TS code stream, because MPEG-2TS bag is fixing 188Bytes length, packet header and adaptation field are at the front end of TS bag, and packet header accounts for 4 bytes, though adaptation field length is unfixing, but fixing structure is arranged, and system is easy to detect packet header and adaptation field after finding the bag start byte of MPEG-2TS code stream.Before MPEG-2TS stream carries out the abnormal LDPC chnnel coding, carry out the position and adjust and handle, according to system's address stored, MPEG-2TS code stream packet header and adaptation field are mapped on the higher information node of the degree of abnormal LDPC code.The payload mappings of MPEG-2TS code stream is to the out of Memory node of abnormal LDPC code.

At system receiving terminal, after the channel decoding module, increase the anti-processing module of protection, the packet header and the adaptation field address of the store M PEG-2TS of system code stream.After MPEG-2TS stream carries out the abnormal LDPC channel decoding, carry out the anti-adjustment in position and handle, according to system's address stored, the information node that the degree of abnormal LDPC code is higher is mapped to the packet header and the adaptation field of MPEG-2TS code stream.The out of Memory node of abnormal LDPC code also according to the payload of map addresses to the MPEG-2TS code stream, is finished the recovery of MPEG-2TS code stream.

Through this process, important informations such as packet header of MPEG-2TS stream and adaptation field are laid special stress on protecting, greatly improved the anti-error code capacity of these important informations, significantly improve systematic function.

The test abnormal LDPC code is to the protective capability of MPEG-2TS stream important information.The degree of selected abnormal LDPC code information node has 2,3, and 6,15 four kinds, its degree distribution generating function is:

ρ(x)＝0.37x ²+0.38x ³+0.15x ⁶+0.1x ¹⁵

When not considering that the importance of packet header of MPEG-2TS code stream and adaptation field and abnormal LDPC code get the unequal error protection ability, directly carry out chnnel coding, it is on 3 the information node that the packet header of MPEG-2TS code stream and adaptation field are mapped to the abnormal LDPC code degree; After the unequal error protection ability of the importance of the packet header of having considered the MPEG-2TS code stream and adaptation field and abnormal LDPC code; carry out important information mapping before chnnel coding, it is on 15 the information node that the packet header of MPEG-2TS code stream and adaptation field are mapped to the abnormal LDPC code degree.

Test environment: modulation system is 16QAM, and channel is an awgn channel, the SPA decoding algorithm iteration that is adopted 20 times.

Test result:

Signal to noise ratio Eb/NO (dB)	The error rate BER in TS stream packet header and adjustment territory before improving	Improve the error rate BER in TS stream packet header, back and adjustment territory
			4.4	1.89e-4	1.08e-5
4.5	3.40e-5	1.99e-6
			4.6	5.52e-6	7.97e-8
4.7	1.42e-6	5.31e-8

As seen; utilize the natural unequal error protection ability of abnormal LDPC code; packet header to the MPEG-2TS code stream is protected with very important information such as adjusting the territory; can make BER decline 1 to 2 order of magnitude (under identical signal to noise ratio) of these important informations; greatly improve its anti-error code capacity, obviously improved the entire system performance.

Description of drawings:

Fig. 1 is certain abnormal LDPC code Tanner figure

Fig. 2 is MPEG-2TS flow structure figure.

Fig. 3 is MPEG-2TS stream head-coating structure figure.

Fig. 4 is MPEG-2TS stream adaptation field structure chart.

Fig. 5 is protection treatment circuit structure chart.

Fig. 6 is the anti-treatment circuit structure chart of protection.

Fig. 7 is certain communication system figure, and 7.1 is transmitting terminal, and 7.2 is receiving terminal

Embodiment:

Analyze selected abnormal LDPC code structure, obtain the degree distribution function of this abnormal LDPC code information node, further the address of the higher information node of degree of obtaining.The packet header and the adaptation field of MPEG-2TS code stream of input is mapped on the higher information node of abnormal LDPC code degree.In the MPEG-2TS code stream order input buffer, read according to the address of the higher information node of abnormal LDPC code degree again, adjusted the position of MPEG-2TS code stream middle wrapping head and adaptation field, thereby realized the mapping of packet header and adaptation field, realized easy to the higher information node of abnormal LDPC code degree.

The packet header of MPEG-2TS code stream is regular length 4 bytes, and adaptation field length is unfixing, and this has increased the difficulty of adaptation field to the higher information node mapping of abnormal LDPC code degree.When realizing, information node mapping that can be only that the part degree of carrying out of one section regular length of adaptation field is higher.Take all factors into consideration the importance of adaptation field internal information and realize difficulty, get preceding 16 bytes of adaptation field (this 16 byte has comprised big extremely portion important information) and 4 bytes in packet header, totally 20 bytes are shone upon.

With reference to the accompanying drawings, embodiments of the present invention are described:

For communication system, this method increased the protection treatment circuit and realizes that this protection treatment circuit contains: controller (11) at the communication system transmitting terminal before the chnnel coding circuit; Counter (12) links to each other with controller (11); Identifier (13) links to each other with controller (13) synchronously, detects MPEG-2TS code stream packet header; Addressed memory (14) for input buffer (15) provides OPADD, and links to each other with controller (11); Input buffer (15) links to each other with addressed memory (14) with controller (11), and this input buffer (15) has MPEG-2TS code stream input and MPEG-2TS code stream output, output packet header and the adjusted MPEG-2TS code stream of adaptation field; In this protection treatment circuit, described guard method realizes according to following steps:

The address of the information node that step 1) is higher with the abnormal LDPC code degree is stored in the addressed memory (14);

Step 2) controller 1 control MPEG-2TS code stream enters input buffer (15) in proper order, and controller (11) starts synchronous identifier (13) and begins to catch step and catch the sync_byte sync byte simultaneously;

Step 3) is worked as synchronous identifier (13) and is captured sync_byte, in order to prevent in the TS stream payload byte identical with sync byte arranged also, can detect sync_byte every 188Bytes, after being consecutively detected three subsynchronous bytes, think that synchronously, (13 offer controller (11) synchronizing signal to identifier synchronously;

After step 4) controller (11) obtained synchronizing signal, enabling counting device (12) count down to 188, MPEG-2TS stream bag just in this moment input buffer (15), and unison counter (12) offers controller (11) count signal;

Step 5) controller (11) starts input buffer (15) output, input buffer (15) beginning begins to export the MPEG-2TS code stream according to the address of the higher information node of abnormal LDPC code degree that addressed memory (14) is stored, the order of the MPEG-2TS code stream of being exported has been adjusted, TS stream packet header and the higher information node of the adjustment corresponding abnormal LDPC code degree in territory;

The controlled MPEG-2TS code stream of step 6) order is input to channel encoder through after encoding, and finishes the mapping to the higher information bit of abnormal LDPC code degree of packet header and adaptation field;

This method, increases the anti-treatment circuit of protection and realizes that this protects anti-treatment circuit to contain: controller (21) after the channel decoding circuit at receiving terminal of communication system; Counter (22) links to each other with controller (21); Addressed memory (23) provides MPEG-2TS code stream packet header and adaptation field address, and links to each other with controller (21); Input buffer (24) links to each other with addressed memory (23) with controller (21), and this input buffer (24) has MPEG-2TS code stream input, receive channel decoding circuit output code flow and MPEG-2TS code stream output, and output recovers the normal sequence code stream; At the anti-treatment circuit of described protection, described method realizes according to following steps:

MPEG-2TS is flowed packet header to step 1) and the adaptation field address is stored in the addressed memory (23);

Step 2) controller (21) control input buffer (24), the code stream of memory channel decoder output, and enabling counting device (22) counting are when counting down to 188, offer controller (22) count signal, what input buffer this moment (24) was stored is the adjusted MPEG-2TS code stream of order;

Step 3) controller (21) starts input buffer (24) output, exports according to the TS stream packet header and the adaptation field address of addressed memory (23) storage, and institute's output code flow is the MPEG-2TS stream of normal sequence just, realizes the recovery of MPEG-2TS stream.Abnormal LDPC code of the present invention is to the unequal error protection method of MPEG-2TS code stream, and to 4 bytes in packet header and preceding 16 bytes of adaptation field, totally 20 bytes are protected.The address of the information node that transmitting terminal addressed memory (14) storage abnormal LDPC code degree is higher.Receiving terminal addressed memory (23) store M PEG-2TS stream packet header and adaptation field address.

A communication system that adopts the method for the invention as shown in Figure 7, transmitting terminal 7.1 has increased protection treatment circuit of the present invention, receiving terminal 7.2 has increased the anti-treatment circuit of protection of the present invention.The MPEG-2TS code stream of input can be multimedia messagess such as video, audio frequency, data; the MPEG-2TS code stream is given protection treatment circuit of the present invention; give the abnormal LDPC code coder then to carry out error correction coding; pass through the OFDM multi-carrier modulation again; after the multiple connections such as last and PN sequence, after the radio-frequency module processing, launch by antenna.The receiving terminal antenna receives modulation signal, after down-conversion and analog-to-digital conversion, delivers to the OFDM multi-carrier demodulation systems through separating multiple connection.Signal after the demodulation is imported the anti-treatment circuit of protection of the present invention after giving the ldpc code decoder processing, recovers the MPEG-2TS code stream at last.

Claims (4)

1. abnormal LDPC code is to MPEG-2TS classification unequal error protection method, it is characterized in that: for communication system, this method increases the protection treatment circuit and realizes that this protection treatment circuit contains: controller (11) at the communication system transmitting terminal before the chnnel coding circuit; Counter (12) links to each other with controller (11); Identifier (13) with controller (11) interconnection, detects MPEG-2TS code stream packet header synchronously; Addressed memory (14) for input buffer (15) provides OPADD, and links to each other with controller (11); Input buffer (15) links to each other with controller (11), and this input buffer (15) has MPEG-2TS code stream input and MPEG-2TS code stream output, output packet header and the adjusted MPEG-2TS code stream of adaptation field; In this protection treatment circuit, described guard method realizes according to following steps:

The address of the information node that step 1) is higher with the abnormal LDPC code degree is stored in the addressed memory (14);

Step 2) controller (11) control MPEG-2TS code stream enters input buffer (15) in proper order, and controller (11) starts synchronous identifier (13) and begins to catch step and catch the sync_byte sync byte simultaneously;

Step 3) is worked as synchronous identifier (13) and is captured the sync_byte sync byte, in order to prevent to occur the byte identical in the MPEG-2TS code stream payload with sync byte, detect sync_byte every 188 bytes, after being consecutively detected three subsynchronous bytes, think that synchronously, identifier (13) offers controller (11) synchronizing signal synchronously;

After step 4) controller (11) obtained synchronizing signal, enabling counting device (12) count down to 188, MPEG-2TS stream bag just in this moment input buffer (15), and unison counter (12) offers controller (11) count signal;

Step 5) controller (11) starts input buffer (15) output, input buffer (15) beginning begins to export the MPEG-2TS code stream according to the address of the higher information node of abnormal LDPC code degree that addressed memory (14) is stored, the order of the MPEG-2TS code stream of being exported has been adjusted, MPEG-2TS code stream packet header and the higher information node of the adjustment corresponding abnormal LDPC code degree in territory;

The controlled MPEG-2TS code stream of step 6) order is input to channel encoder through after encoding, and finishes packet header and adjusts the mapping of territory to the higher information bit of abnormal LDPC code degree;

This method, increases the anti-treatment circuit of protection and realizes that this protects anti-treatment circuit to contain: controller (21) after the channel decoding circuit at receiving terminal of communication system; Counter (22) links to each other with controller (21); Addressed memory (23) provides MPEG-2TS code stream packet header and adaptation field address, and links to each other with controller (21); Input buffer (24) links to each other with addressed memory (23) with controller (21), and this input buffer (24) has MPEG-2TS code stream input, receive channel decoding circuit output code flow and MPEG-2TS code stream output, and output recovers the normal sequence code stream; At the anti-treatment circuit of described protection, described method realizes according to following steps:

MPEG-2TS is flowed packet header to step 1) and the adaptation field address is stored in the addressed memory (23);

Step 2) controller (21) control input buffer (24), the code stream of memory channel decoder output, and enabling counting device (22) counting are when counting down to 188, offer controller (21) count signal, what input buffer this moment (24) was stored is the adjusted MPEG-2TS code stream of order;

Step 3) controller (21) starts input buffer (24) output, exports according to the MPEG-2TS stream packet header and the adaptation field address of addressed memory (23) storage, and institute's output code flow is the MPEG-2TS stream of normal sequence just, realizes the recovery of MPEG-2TS stream.

2. abnormal LDPC code according to claim 1 is characterized in that MPEG-2TS unequal error protection method: to 4 bytes in packet header and preceding 16 bytes of adaptation field, totally 20 bytes are protected.

According to the described abnormal LDPC code of claim 1 to MPEG-2TS unequal error protection method, the address of the information node that transmitting terminal addressed memory (14) storage abnormal LDPC code degree is higher.

According to the described abnormal LDPC code of claim 1 to MPEG-2TS unequal error protection method, receiving terminal addressed memory (23) store M PEG-2TS stream packet header and adaptation field address.

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