CN1522069A - A Method for Preventing Illegal Broadcasting in Cable Digital TV Broadcasting - Google Patents

Abstract

The method for preventing illegal broadcasting in cable digital television broadcasting belongs to the technical field of signal transmission security, and is characterized in that: the sender regularly inserts control information at the transmission layer, and the receiver detects the control information before de-interleaving after phase demodulation at the physical layer, and judges the broadcast data The legality of the application is accepted or rejected. It can implement a method of preventing illegal broadcasting for receivers designed according to this method, and prevent illegal broadcasting from destroying my country's TV broadcasting industry. It is also compatible with receivers that have not yet been designed using this method on the market so that they can be used normally. Receive TV signal.

Description

A Method for Preventing Illegal Broadcasting in Cable Digital TV Broadcasting

technical field

A method for preventing illegal broadcasting in cable digital television broadcasting belongs to the technical field of signal transmission security, in particular to the technical field of signal transmission security in Internet, digital television and data broadcasting.

Background technique

In the past few years, with the transition from analog TV to digital TV, digital TV will become an important high-tech product that transmits production and living information and enriches the cultural life of the masses. TV signal is an important public information resource, which plays an important role in people's daily life, production and cultural progress. At present, there are some malicious acts that undermine the security of public information. For example, from June 23 to June 30, 2002, the overseas "Falungong" cult organization under the control and command of Li Hongzhi illegally launched radio signals to attack our Sino satellite. . The 9 programs of CCTV and 10 provincial TV stations in the "Village to Village" radio and television project transmitted on the satellite transponder were severely interfered, and some rural and remote mountainous people could not normally watch news, weather, flood forecast, World Cup, etc. Football finals and other shows. This serious illegal activity of interfering with the normal broadcasting of radio and television programs and the normal use of satellites violates relevant international conventions and basic norms of civil communications, endangers national security and violates public rights and interests. In order to prevent the bad effects of illegal broadcasting, in the cable digital TV broadcasting technology that will be popularized in our country, technical means of protecting public information security should be adopted to prevent bad effects of illegal TV broadcasting and protect public interests.

A method for preventing illegal broadcasting in cable digital TV broadcasting described in this paper uses the sending party to regularly insert the control sequence at the transmission layer, and the receiver detects the control sequence after phase demodulation at the physical layer before de-interleaving to judge the legitimacy of the broadcast data. Make acceptance or rejection processing. This is a security measure based on standards-based cable digital television broadcasting technology.

Contents of the invention

The purpose of the present invention is to provide a method for preventing illegal broadcasting in cable digital television broadcasting.

The present invention is characterized in that: the sending end regularly inserts control information into the transmission stream in cable digital television broadcasting, and the receiving end detects the specified control information after phase demodulation and before deinterleaving, extracts the control information, and verifies the broadcast transmitter Legality, for acceptance or rejection processing; it contains the following processing steps in turn:

(a). Generate control information with a length of 120 bits (15 bytes), and the byte numbers are 1 to 15; the control information is divided into synchronization, address field, control packet count, reserved broadcast channel, and CRC check, a total of 5 field; the length of the synchronization field is 32 bits, occupying the 1st, 2nd, 3rd, and 4th bytes of the 15-byte control information, and the sequence value of the synchronization field is expressed as 5D 8F 9A43 in hexadecimal; the length of the address domain field is 16 bits, occupying the 5th and 6th bytes of the 15-byte control information, using extended Hamming code encoding, in which the address code occupies the 1st to 11th bits, and the Hamming check code occupies the 12th to 15th bits, even The check code occupies the 16th bit; the length of the control packet count field is 8 bits, occupying the 7th byte of the 15-byte control information, and the count value is 0 to 255 cycles; the length of the reserved broadcast channel field is 48 bits, occupying 15 bytes The 8th to 13th bytes of the byte control information; the length of the CRC check field is 16 bits, occupying the 14th and 15th bytes of the 15-byte control information, and is used for the CRC check of the entire 15-byte control information test, its generating polynomial is g(x)=x ¹⁶ +x ¹² +x ⁵ +1;

(b). Generate 8 pre-scrambling patterns, each pre-scrambling pattern has 15 bytes, and is used to pre-scramble the above-mentioned 15-byte control information;

(c). According to the principle that the randomization process should be compatible with the satellite system in GB/T 17700-1999, carry out data scrambling and randomization processing on the transport stream composed of MPEG-2 packets, and it also contains the following steps in turn :

(c.1). It is stipulated that the inserted MPEG-2 packet carrying control information is fixed as the i-th packet in a group of 8 MPEG-2 packets, where 1≤i≤8;

(c.2). The 15 bytes of control information generated in step (a) and the jth 15 bytes of the 8 pre-scrambling patterns generated in step (b) are subjected to bit-wise XOR processing , where 1≤j≤8, and j must correspond to the position i of the MPEG-2 packet, and the pre-scrambled 15-byte control information is obtained;

(c.3). Map the pre-scrambled control information into an MPEG-2 packet without user data. This MPEG-2 packet is set with an empty packet identifier or a special identifier agreed with the receiving end; each packet Consisting of 188 bytes, the pre-scrambled 15-byte control information is mapped to the 13th, 25th, 37th, 49th, 61st, and 73, 85, 97, 109, 121, 133, 145, 157, 169, 181 bytes; get the control packet;

(d). Carry out empty MPEG-2 packet filtering to the transmission stream of standard cable digital TV at first, and cache the MPEG-2 packet stream after filtering out empty packets; Multiplexing and rate adaptation module is used for multiplexing Cache the output MPEG-2 packet flow and control packet, ensure that the control packet is inserted into the MPEG-2 packet flow at intervals of 2 milliseconds, and ensure that the inserted control packet can only appear in each group of 8 transmission packets At the position of the i-th packet, in order to maintain a certain transmission rate during the multiplexing process, when the input rate is too small, a certain number of empty packets are inserted, and when the input rate is too high, some data packets are discarded; the transport stream processed;

(e). The transport stream processed by inserting control packets is subjected to standard cable digital TV synchronous inversion, scrambling randomization, encoding and convolutional interleaving;

(f). Carry out channel encryption processing on the transmission stream processed by standard encoding and convolution interleaving, and adopt pseudo-random scrambling with variable initial state, and its generator polynomial is g(x)=x ¹⁹ +x ⁵ +x ² +x+1, the 11-bit address code and 8-bit packet count value of the control information are used as the 19-bit initial state, and the transmission packet between the current control packet and the next control packet is scrambled after each control packet is inserted, and the control The packet is not scrambled; the encrypted transport stream is subjected to standard cable digital TV symbol mapping and modulation processing, and then sent out;

(g). In the receiver, first carry out the demodulation processing of the standard cable digital TV to the received transmission stream. At this time, the de-interleaving and channel decoding processing have not been performed, and the digital signal is initially obtained from the radio frequency signal; In the flow, by detecting the standard transmission packet header, identify the transmission packets one by one, and then detect the i-th signal packet agreed with the transmitter in the 8 signal packets of each frame, if the 13th, 25, 37, 49, 61, 73, 85, 97, 109, 121, 133, 145, 157, 169, and 181 bytes identify the control information in the specified format, indicating that the data flow is a legal data flow, and the data is received normally; If within a specified period of t seconds, the appearance of the control information in the specified format has not been detected, it indicates that it is an illegal data stream, the data is refused to be received, and the control information is continued to be detected.

In the 8 kinds of pre-scrambling modes described in step (b), each kind of hexadecimal number from the 1st byte to the 15th byte sequence is expressed as follows:

Type 1: 73 A1 2B B4 9D 86 3B 30 25 3A FB 63 F7 EA 7D

Type 2: 71 2E A7 84 32 A3 76 41 D8 DB 19 CC 52 38 05

The third type: FC 56 91 50 68 CF 66 C7 1F 41 07 9D AA 97 58

  Type 4: 56 37 E3 B6 9A 6A 9B 53 08 56 6A 45 2A A8 62

Type 5: D5 E8 DF B0 99 DF C4 53 74 63 58 99 29 EE D7

  Type 6: 38 D4 DC 73 73 52 C1 6F 81 8A 36 DA 25 9F 08

  Type 7: C1 98 94 1D 97 D2 7D 8A BE BA B5 53 00 A9 F3

Type 8: C2 D5 9E 6A 3D E0 D6 03 66 19 66 E1 33 96 E5.

The interval of inserting control packets is 2 milliseconds, corresponding to different transmission rates, inserting a control packet in every multiple of 8 transmission packets; Insert a control packet in every 8 transmission packets at the second; insert a control packet in every 16 transmission packets when the rate of the transmission stream after inserting the control packet is required to be 13.056 Mbits per second; Insert a control packet in every 24 transmission packets when the rate of the transport stream after the packet is 19.584 Mbits per second; Insert a control packet into the packet; insert a control packet in every 48 transmission packets when the rate of the transmission stream after the insertion of the control packet is required to be 39.168 Mbits per second; when the rate of the transmission stream after the insertion of the control packet is required A control packet is inserted in every 64 transport packets at 52.224 Mbits per second.

The receiving end detects the control packet and extracts timing information with a period of 2 milliseconds for network synchronization

In the process of generating the control packet in step (c), the packet identifier of the control packet carrying the control information is agreed upon by the sending end and the receiving end.

Experiments prove that the invention effectively prevents illegal broadcast information inserted from outside. It is also compatible with general receivers.

Description of drawings:

The structure block diagram of Fig. 1 standard cable digital TV transmitter and receiver;

The schematic diagram of the transmission packet structure of Fig. 2 MPEG-2;

Figure 3a MPEG-2 transport packet

Figure 3b Randomized Transport Packet: Sync Byte and Randomization Sequence

Figure 3c RS(204, 188, T=8) code error protection packet

Figure 3d interleaving frame: interleaving depth I = 12 bytes

The block diagram of randomization and de-randomization in Fig. 4 standard cable digital TV;

Fig. 5 block diagram of convolutional interleaver and de-interleaver in standard cable digital TV;

The structural block diagram of the cable digital television transmitter and receiver containing control signal insertion and detection of Fig. 6 of the present invention;

Fig. 7 is a schematic structural diagram of a control signal in the present invention;

FIG. 8 is a schematic structural diagram of the address field in the control signal in the present invention;

Fig. 9 is a schematic diagram of the channel encryption process in the present invention;

Detailed ways:

We first describe the signal processing process of standard cable digital TV broadcasting technology, as shown in Figure 1.

In the transmitter of the standard cable digital TV broadcasting technology, the input is the standard MPEG-2 code stream, and the MPEG-2 code stream is composed of 188-byte MPEG-2 packets one by one, as shown in Figure 2, each The MPEG-2 packet consists of a 4-byte header and a 184-byte payload that is data; the 4-byte header is further divided into: a one-byte sync byte (47H), and a 15-bit packet flag, Packet marking is used to identify the type of packet and other control information of several bits; in this patent, we only use synchronization byte and packet marking;

In a standard cable digital TV broadcasting transmitter, the input standard MPEG-2 code stream is input through the baseband physical interface, and first undergoes synchronization byte (syncl) inversion and randomization processing, as shown in Figure 3a, which has not yet been synchronized The MPEG-2 packet of byte (syncl) reversal, syncl is the synchronization byte 47H, in Fig. 3a, Fig. 3b, Fig. 3c, Fig. 3d SYNC1 represents the inverse code of the non-randomized synchronization byte, that is, B8H, and SYNCn represents the non-randomized synchronization byte, that is, 47H, where n=2, 3, . . . , 8.

Figure 3b is a schematic diagram of a group of 8 transport packets processed by synchronization byte inversion and randomization. The difference between the transmission packet and the MPEG-2 packet is that the synchronization byte of the MPEG-2 packet is 47H, and the transmission packet It is a group of 8 packets, the synchronization byte of the first packet is B8H, they are all 188 bytes, and the definitions of other fields are compatible; the system input code stream is MPEG-2 packet, as shown in Figure 3 The structure is randomized, compatible with the satellite system in GB/T 1770-1999. The generator polynomial of the randomized pseudo-random binary sequence (PRBS) is as follows:

1+x ¹⁴ +x ¹⁵

As shown in Figure 4, the sequence "100101010000000" is loaded into the PRBS counter to initialize it at the beginning of every 8 transmission packets. In a group of 8 packet lengths, the synchronization byte 47H of the first packet is reversed bit by bit, from 47H to B8H, which is to provide a start signal to the receiver descrambler. The first bit of the PRBS output is XORed with the first bit of the first byte after the sync byte (B8H) of the inverted transmission packet, and then the other bits are sequentially applied. In order to realize other synchronization functions, during the duration of the synchronization bytes of the subsequent 7 transmission packets, the PRBS continues to work, but its output is invalid, and these synchronization bytes are not randomized. Thus, the period of the PRBS sequence is 1503 bytes. The result of randomization is shown in Figure 3b. In each group of 8 transmission packets, the synchronization byte of the first packet is reversed to B8H, the synchronization byte of the other 7 packets remains 47H, and the 8 transmission packets All non-sync bytes in are randomized, ie bit-by-bit XORed with the PRBS sequence.

In the transmitter of standard cable digital TV broadcasting, the transmission packet after synchronization byte (syncl) inversion and randomization processing is carried out standard RS encoding, and RS (204, 188, T=8) code error protection is obtained packet, here each packet length is 204 bytes, wherein the first 188 bytes are the content of the transmission packet, unchanged, and the last 16 subsections are error code protection subsections, as shown in Figure 3c, our invention does not involve RS encoding and decoding The process, the theory and technology of RS coding can be found in "Error Correcting Codes - Principles and Methods", Xidian University, Wang Xinmei et al.

In a standard cable digital TV broadcasting transmitter, the RS-encoded data stream is subjected to convolutional interleaving processing with an interleaving depth of 12 bytes. The convolutional interleaving and corresponding de-interleaving processes are shown in Figure 5. The final transmission packet is shown in Figure 3d. Our invention does not involve the convolutional interleaving process. The theory and technology of convolutional interleaving can be found in "Error Correcting Codes - Principles and Methods", Xidian University, Wang Xinmei et al. It is worth noting that in our control packet, the control information is stored in the 13th, 25th, 37th, 49th, 61, 73, 85, 97, 109, 121, 133, 145, 157th of the 188-byte control packet , 169, and 181 bytes, after RS encoding and convolutional interleaving, the information on these bytes does not change in position, so that at the receiver, we can convert from RS to decoding and convolutional deinterleaving. The control information is extracted, and before RS decoding and convolution deinterleaving, the legality of the data can be judged and received or rejected.

In a standard cable digital TV broadcasting transmitter, the data stream processed by convolution and interleaving undergoes byte-to-m-bit symbol conversion, differential coding, baseband shaping, QAM modulation, and IF and RF physical interface processing, and is sent to the physical channel superior.

In a standard cable digital TV broadcast receiver, the signal from the physical channel passes through the RF and IF physical interface and QAM demodulator, matched filtering and equalization, differential decoder, symbol-to-byte mapping, and initially obtains the byte flow;

In a standard cable digital TV broadcast receiver, after convolution and deinterleaving, RS decoding, synchronous inversion and de-randomization, the MPEG-2 packet stream is output from the baseband physical interface and sent to the digital TV decoding device for processing .

In the standard cable digital TV broadcasting technology of the present invention, the transmitter regularly inserts control information at the transmission layer, and the receiver detects the control information after phase demodulation at the physical layer before interleaving, judges the legality of the broadcast data, and makes acceptance or rejection processing; the significance of such processing is to implement a method for preventing illegal broadcasting for receivers conforming to the design of this patent, and to prevent illegal broadcasting from destroying my country's TV broadcasting industry. It is also compatible so that it can receive TV signals normally. Its signal processing process is shown in Figure 6; its processing process is as follows:

The first step is to generate control information with a length of 120 bits (15 bytes), as shown in Figure 7, the byte numbers are 1 to 15; the control information is divided into synchronization, address field, control packet count, reserved broadcast channel, CRC Checksum, a total of 5 fields; the length of the synchronization field is 32 bits, occupying the 1st, 2nd, 3rd, and 4th bytes of the 15-byte control information, and the sequence value of the synchronization field is expressed as 5D 8F 9A in hexadecimal 43; The length of the address domain field is 16 bits, occupying the 5th and 6th bytes of the 15-byte control information, and using extended Hamming code encoding, as shown in Figure 8, where the address code occupies the 1st to 11th bits, and the Hanming The plain check code occupies the 12th to 15th bits, and the even check code occupies the 16th bit; the length of the control packet count field is 8 bits, occupying the 7th byte of the 15-byte control information, and the count value is 0 to 255 cycles ;The length of the reserved broadcast channel field is 48 bits, occupying the 8th to 13th bytes of the 15-byte control information; the length of the cyclic redundancy check code (CRC) check field is 16 bits, occupying the 15th byte of the control information 14, 15 bytes, used for the CRC check of the control information of the whole 15 bytes, its generator polynomial is g(x)=x ¹⁶ +x ¹² +x ⁵ +1; according to the standard CRC code encoding method, The encoding process is to regard the information bits as a polynomial, for example, if the information bit is 1001, then the corresponding polynomial is s(x)=x ³ +1, multiply s(x) by x ¹⁶ , here 16 is because the CRC code check The number of detection bits is 16, and then polynomial division is performed on it. $\frac{\mathrm{the\; s}\left(x\right)\×x^{16}}{g\left(x\right)}=q\left(x\right)+\frac{r\left(x\right)}{g\left(x\right)},$ Where q(x) is the part that can be divisible by g(x) after multiplying s(x) by x ¹⁶ , r(x) is the part that cannot be divisible by g(x), then encode the CRC of the information s(x) The final result is s(x)×x ¹⁶ +r(x), which is divisible by g(x), the receiver performs polynomial division on it, divides it by g(x), and analyzes the remainder, You can check whether there is an error in the data transmission. These are standard CRC code methods. The theory and technology of CRC codes can be found in "Error Correcting Codes-Principles and Methods", Xidian University, Wang Xinmei et al.

The second step is to generate a 15-byte pre-scrambling pattern, which is used to pre-scramble the 15-byte control information generated above. There are 8 kinds of 15-byte pre-scrambling patterns, starting with the hexadecimal number The order of 1 byte to 15th byte is expressed as follows:

Type 1: 73 A1 2B B4 9D 86 3B 30 25 3A FB 63 F7 EA 7D

Type 2: 71 2E A7 84 32 A3 76 41 D8 DB 19 CC 52 38 05

Type 3: FC 56 91 50 68 CF 66 C7 1F 41 07 9D AA 97 58

Type 4: 56 37 E3 B6 9A 6A 9B 53 08 56 6A 45 2A A8 62

Type 5: D5 E8 DF B0 99 DF C4 53 74 63 58 99 29 EE D7

Type 6: 38 D4 DC 73 73 52 C1 6F 81 8A 36 DA 25 9F 08

Type 7: C1 98 94 1D 97 D2 7D 8A BE BA B5 53 00 A9 F3

Type 8: C2 D5 9E 6A 3D E0 D6 03 66 19 66 E1 33 96 E5

In the third step, the transmission stream of standard cable digital TV is composed of MPEG-2 packets, and the data scrambling and randomization process should be performed on the transmission stream. The randomization process can be compatible with the satellite system in GB/T17700-1999. That is, every 8 MPEG-2 packets are taken as a group, the synchronization byte of the first MPEG-2 packet is reversed from 47H to B8H, and a start signal is given to the scrambler, and the specified scrambler is used for every 8 MPEG-2 packets. The scrambling mode is scrambled; the MPEG-2 packet carrying the control information inserted after the present invention stipulates is fixed as the i-th packet in these 8 MPEG-2 packets, wherein 1≤i≤8; here just to the ath step Perform pre-scrambling on the generated 15-byte control information, that is, perform bit-wise XOR processing with the 15 bytes of the j-th type of the 8 pre-scrambling modes generated in step b, where 1≤j ≤8, and correspond to i; obtain the pre-scrambled 15-byte control information; map the pre-scrambled 15-byte control information to an MPEG-2 packet that does not carry user data, this MPEG-2 The packet is set with an empty packet identifier or a special identifier agreed with the receiving end; each packet is composed of 188 bytes, and the pre-scrambled 15-byte control information is mapped separately from the 1st to the 15th byte order To the 13th, 25th, 37th, 49th, 61st, 73th, 85th, 97th, 109th, 121st, 133th, 145th, 157th, 169th, 181th bytes of this MPEG-2 packet; get the control packet;

The fourth step is to first filter out empty MPEG-2 packets on the transmission stream of standard cable digital TV, and cache the MPEG-2 packet stream after filtering out empty packets; the multiplexing and rate adaptation module is used for multiplexing Cache the output MPEG-2 packet flow and control packet, ensure that the control packet is inserted into the MPEG-2 packet flow at intervals of 2 milliseconds, and ensure that the inserted control packet can only appear in each group of 8 transmission packets At the position of the i-th packet, in order to maintain a certain transmission rate during the multiplexing process, when the input rate is too small, a certain number of empty packets are inserted, and when the input rate is too high, some data packets are discarded; the transport stream processed;

In the fifth step, the transmission stream processed by inserting control packets is subjected to synchronous inversion of standard cable digital TV, scrambling randomization, encoding and convolution interleaving, as shown in Figure 3a, Figure 3b, Figure 3c, Figure 3d, Figure 4 , and shown in Figure 5;

The sixth step is to perform channel encryption processing on the transmission stream that has undergone standard coding and convolution interleaving processing, and adopt pseudo-random scrambling with variable initial state, and its generator polynomial is g(x)=x ¹⁹ +x ⁵ +x ² +x+1, the 11-bit address code and 8-bit packet count value of the control information are used as the 19-bit initial state. The scrambling process is shown in Figure 9. After each control packet is inserted, the current control packet and the next control packet scramble the transmission packets in between, and not scramble the control packets; perform standard cable digital TV symbol mapping and modulation processing on the encrypted transmission stream, and send it out;

In the seventh step, in the receiver, firstly carry out standard cable digital TV demodulation processing on the received transmission stream. At this time, the deinterleaving and channel decoding processing have not been performed, and the digital signal is initially obtained from the radio frequency signal; In the flow, by detecting the standard transmission packet header, identify the transmission packets one by one, and then detect the i-th signal packet agreed with the transmitter in the 8 signal packets of each frame, if the 13th, 25, 37, 49, 61, 73, 85, 97, 109, 121, 133, 145, 157, 169, and 181 bytes identify the control information in the specified format, indicating that the data flow is a legal data flow, and the data is received normally. Perform decryption processing, which corresponds to the encryption processing in the sixth step above. The encryption and decryption processing is equivalent to a kind of scrambling and descrambling operation. The scrambling and descrambling process is shown in Figure 9, and then the deinterleaving of standard cable digital TV is carried out and channel decoding processing, and finally get the MPEG-2 code stream, which is sent to the digital TV decoding equipment for processing; if within a specified period of t seconds, the appearance of the control information in the specified format has not been detected, it is indicated as illegal Data flow, refuse to receive data, and continue to detect control information.

Features and effects of the present invention:

The sender inserts control information regularly at the transport layer, and the receiver detects the control information after the phase demodulation of the physical layer and before de-interleaving, judges the validity of the broadcast data, and makes a processing of receiving or rejecting; the significance of such processing is that the The designed receiver implements a method for preventing illegal broadcasting, prevents illegal broadcasting from destroying my country's TV broadcasting industry, and is also compatible with receivers that have not yet adopted the design of the invention in the market so that they can normally receive TV signals.

Claims (5)

1. The method for preventing illegal broadcasting in cable digital television broadcasting is characterized in that: the sending end regularly inserts control information in the transmission stream in cable digital television broadcasting, and the receiving end detects the prescribed control information before deinterleaving after phase demodulation Information, extracting control information, verifying the legitimacy of the broadcast transmitter, and processing it for receiving or rejecting; it contains the following processing steps in turn: (a). Generate control information with a length of 120 bits (15 bytes), and the byte numbers are 1 to 15; the control information is divided into synchronization, address field, control packet count, reserved broadcast channel, and CRC check, a total of 5 field; the length of the synchronization field is 32 bits, occupying the 1st, 2nd, 3rd, and 4th bytes of the 15-byte control information, and the sequence value of the synchronization field is expressed as 5D 8F9A 43 in hexadecimal; the length of the address domain field is 16 bits, occupying the 5th and 6th bytes of the 15-byte control information, using extended Hamming code encoding, in which the address code occupies the 1st to 11th bits, and the Hamming check code occupies the 12th to 15th bits, even The check code occupies the 16th bit; the length of the control packet count field is 8 bits, occupying the 7th byte of the 15-byte control information, and the count value is 0 to 255 cycles; the length of the reserved broadcast channel field is 48 bits, occupying 15 bytes The 8th to 13th bytes of the byte control information; the length of the CRC check field is 16 bits, occupying the 14th and 15th bytes of the 15-byte control information, and is used for the CRC check of the entire 15-byte control information test, its generating polynomial is g(x)=x ¹⁶ +x ¹² +x ⁵ +1; (b). Generate 8 pre-scrambling patterns, each pre-scrambling pattern has 15 bytes, and is used to pre-scramble the above-mentioned 15-byte control information; (c). According to the principle that the randomization process should be compatible with the satellite system in GB/T 17700-1999, carry out data scrambling and randomization processing on the transport stream composed of MPEG-2 packets, and it also contains the following steps in turn : (c.1). It is stipulated that the inserted MPEG-2 packet carrying control information is fixed as the i-th packet in a group of 8 MPEG-2 packets, where 1≤i≤8; (c.2). The 15 bytes of control information generated in step (a) and the jth 15 bytes of the 8 pre-scrambling patterns generated in step (b) are subjected to bit-wise XOR processing , where 1≤j≤8, and j must correspond to the position i of the MPEG-2 packet, and the pre-scrambled 15-byte control information is obtained; (c.3). Map the pre-scrambled control information into an MPEG-2 packet without user data. This MPEG-2 packet is set with an empty packet identifier or a special identifier agreed with the receiving end; each packet Consisting of 188 bytes, the pre-scrambled 15-byte control information is mapped to the 13th, 25th, 37th, 49th, 61st, and 73, 85, 97, 109, 121, 133, 145, 157, 169, 181 bytes; get the control packet; (d). Carry out empty MPEG-2 packet filtering to the transmission stream of standard cable digital TV at first, and cache the MPEG-2 packet stream after filtering out empty packets; Multiplexing and rate adaptation module is used for multiplexing Cache the output MPEG-2 packet flow and control packet, ensure that the control packet is inserted into the MPEG-2 packet flow at intervals of 2 milliseconds, and ensure that the inserted control packet can only appear in each group of 8 transmission packets At the position of the i-th packet, in order to maintain a certain transmission rate during the multiplexing process, when the input rate is too small, a certain number of empty packets are inserted, and when the input rate is too high, some data packets are discarded; the transport stream processed; (e). The transport stream processed by inserting control packets is subjected to standard cable digital TV synchronous inversion, scrambling randomization, encoding and convolutional interleaving; (f). Carry out channel encryption processing on the transmission stream processed by standard encoding and convolution interleaving, and adopt pseudo-random scrambling with variable initial state, and its generator polynomial is g(x)=x ¹⁹ +x ⁵ +x ² +x+1, the 11-bit address code and 8-bit packet count value of the control information are used as the 19-bit initial state, and the transmission packet between the current control packet and the next control packet is scrambled after each control packet is inserted, and the control The packet is not scrambled; the encrypted transport stream is subjected to standard cable digital TV symbol mapping and modulation processing, and then sent out; (g). In the receiver, first carry out the demodulation processing of the standard cable digital TV to the received transmission stream. At this time, the de-interleaving and channel decoding processing have not been performed, and the digital signal is initially obtained from the radio frequency signal; In the flow, by detecting the standard transmission packet header, identify the transmission packets one by one, and then detect the i-th signal packet agreed with the transmitter in the 8 signal packets of each frame, if the 13th, 25, 37, 49, 61, 73, 85, 97, 109, 121, 133, 145, 157, 169, and 181 bytes identify the control information in the specified format, indicating that the data flow is a legal data flow, and the data is received normally; If within a specified period of t seconds, the appearance of the control information in the specified format has not been detected, it indicates that it is an illegal data stream, the data is refused to be received, and the control information is continued to be detected. 2. The method for preventing illegal broadcasting in cable digital television broadcasting according to claim 1 is characterized in that: 8 kinds of pre-scrambling patterns described in step (b), every kind uses hexadecimal number from the 1st Byte to byte order 15 is represented as follows: Type 1: 73 A1 2B B4 9D 86 3B 30 25 3A FB 63 F7 EA 7D Type 2: 71 2E A7 84 32 A3 76 41 D8 DB 19 CC 52 38 05 Type 3: FC 56 91 50 68 CF 66 C7 1F 41 07 9D AA 97 58 Type 4: 56 37 E3 B6 9A 6A 9B 53 08 56 6A 45 2A A8 62 Type 5: D5 E8 DF B0 99 DF C4 53 74 63 58 99 29 EE D7 Type 6: 38 D4 DC 73 73 52 C1 6F 81 8A 36 DA 25 9F 08 Type 7: C1 98 94 1D 97 D2 7D 8A BE BA B5 53 00 A9 F3 Type 8: C2 D5 9E 6A 3D E0 D6 03 66 19 66 E1 33 96 E5. 3. according to the method for preventing illegal broadcasting in a kind of cable digital television broadcasting according to claim 1, it is characterized in that, the interval of described insertion control packet is 2 milliseconds, corresponding to different transmission rates, at every multiple of 8 Insert a control packet into every 8 transmission packets; when the rate of the transmission stream after the insertion of the control packet is required to be 6.528 Mbits per second, insert a control packet into every 8 transmission packets; when the transmission stream after the insertion of the control packet is required Insert a control packet in every 16 transmission packets when the rate is 13.056 Mbits per second; insert a control packet in every 24 transmission packets when the transmission rate after inserting control packets is required to be 19.584 Mbits per second packet; when the rate of the transmission stream after inserting control packets is required to be 26.112 Mbits per second, a control packet is inserted in every 32 transmission packets; when the rate of the transmission stream after insertion of control packets is required to be 39.168 Mbits per second Insert a control packet in every 48 transmission packets at the second; insert a control packet in every 64 transmission packets when the rate of the transmission stream after inserting the control packets is required to be 52.224 Mbits per second. 4. according to the method for preventing illegal broadcasting in a kind of cable digital television broadcasting according to claim 1, it is characterized in that, described receiving end is by detecting control packet, extracts therefrom the timing information that cycle is 2 milliseconds, is used for Network synchronization. 5. according to the method for preventing illegal broadcasting in a kind of cable digital television broadcasting according to claim 1, it is characterized in that, in the control packet generation process of described (c) step, the control packet used to carry control information The packet label is agreed upon by the sender and receiver.

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