JPH03128572A - Transmitting and receiving method for facsimile broadcast - Google Patents

Abstract

PURPOSE:To prevent deviation in the descramble timing even to a data packet missing caused by a transmission error by applying scrambling in the unit of N bits and all to each block being divisions of a picture signal in the unit of N (integral number) bits. CONSTITUTION:An original picture signal is divided into blocks in the unit of 176 bits from the head and scrambling is applied by adding a pattern of the above-mentioned 176 bits to a picture bocks in the unit of 176 bits. Thus, when packet missing takes place due to a transmission error at reception, the timing deviation of descramble takes place in a conventional method and a problem of the deviation affected onto a succeeding picture data is solved.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a facsimile broadcast transmission/reception method suitable for use in a paid broadcasting system in facsimile broadcasting in which facsimile signals are multiplexed onto broadcast radio waves and broadcast.

(b) Conventional Technology Currently, teletext services are being provided in order to diversify and improve the sophistication of television broadcasting services.

Furthermore, deliberations are underway at the Telecommunications Technology Council with the aim of putting facsimile broadcasting, which multiplexes facsimile images onto broadcast waves, into practical use for the purpose of supplementary services for television and teletext broadcasting, as well as special services. The contents of this facsimile broadcasting service are diverse, such as TV program information, tourist information, stock market conditions, and specialized information.

This facsimile broadcasting transmission method employs a method in which a subcarrier modulated by a facsimile signal is multiplexed with voice by frequency division into an audio carrier wave, and then FM modulated and transmitted. An outline of this method will be explained below.

The center frequency of the subcarrier is 4.5 f 1I (70, 80
4 kHz; fs' (horizontal synchronizing pulse frequency of television), on which the facsimile signal is modulated by a four-phase differential phase modulation method. As shown in Fig. 4, the facsimile signal consists of 32 buckets of 288 bits each, and a frame synchronization signal is added to the frame structure.
Take Omatsuto.

As shown in Figure 5, each bucket is called MC (Mode Control) to identify the type of service.
It consists of a header of 6 bits and a data bucket part of 272 bits.

Furthermore, the data bucket consists of a 14-bit prefix, a 176-bit data part, and a single data bucket.
A 7-bit format is used in which 82 bits of code for error correction are added to 90 bits of information, and it is possible to identify whether the contents of the data portion are an image signal or a control signal using the bfix.

The image signal is composed of a signal obtained by adding a control code such as an EOL (line synchronization signal) after encoding the original image signal using a redundancy suppression encoding method called MH or MR.

Now, the report on facsimile broadcasting is aimed at non-pay broadcasting, but it is thought that future pay broadcasting systems will continue to be considered.

Paid broadcasting is a broadcasting system in which receivers can receive specific broadcasting services by entering into a remuneration contract with a broadcaster. An effective method is to scramble the image signal and transmit it with confidentiality, so that only paid broadcast subscribers can restore it using a decoder.
For example, the scrambled method is also used in paid satellite broadcasting systems.

Conventionally, as a method of scrambling, a PN (pseudorandom) signal sequence is added to a digitized binary signal sequence (
An EX-OR calculation circuit is used as a mod 2 addition circuit), and a shift register array based on a generator polynomial is used as a PN signal generation circuit. In this case, a combination of generator polynomials and initial values of shift registers may be used as the scrambling key.

When using this scrambling method for facsimile broadcasting, it is only necessary to scramble the image data part before transmission. For example, a shift register for scrambling is initialized at the beginning of each person's image signal, and then the shift register string is It is only necessary to add the output signal to the image signal while shifting the output signal every one clock.

On the other hand, on the receiving side, a descrambling circuit based on the same generating polynomial as that on the transmitting side is used to set a predetermined initial value based on a flag indicating the beginning of each member's image, and from then on, the output of the PN signal generation circuit is received. By adding it to the signal (which has been scrambled), the original image signal can be restored.

(c) Problems to be Solved by the Invention Although scrambling using such a PN signal generation circuit is generally a commonly used method, when applying it to facsimile broadcasting, consideration must be given to the following points.

As mentioned above, in data transmission using the facsimile broadcast band, it is possible to identify whether the received signal is a non-paid facsimile broadcast, a paid facsimile broadcast, or another service, taking into consideration the possibility of services other than facsimile broadcasting. The data is sent in a format in which a predetermined mode control signal (hereinafter referred to as MC) is added as a header. On the other hand, on the receiver side of facsimile broadcasting for paid broadcasting, the MC is referenced for the received signal, and if the MC is different from the MC specified for the paid broadcasting, the corresponding data bucket section is basically discarded. conduct.

Generally, in the case of broadcasting using radio waves, ghosts (multiple wave interference due to reflection) and noise interference interfere with the propagation characteristics of the radio waves, and depending on the interference situation, bit errors may occur during transmission.

For this purpose, a BCH correction code is added to the MC section, and 1
Efforts have been made to be able to correct errors in up to 3 out of 6 bits, but if the interference is large, correction may become impossible and image data from paid facsimile broadcasting services may be discarded.

On the other hand, when descrambling processing is performed on the receiving side, if a bucket dropout of the image signal occurs due to the above-mentioned MC section error 9, the timing of descrambling for subsequent image signals will be shifted, and the original image will not be restored. become unable. As a countermeasure, for example, the timing of the descrambling process can be corrected by attaching a bucket number to each bucket of the image signal and transmitting it, and detecting whether or not the bucket of image data is missing on the receiving side, but the circuit is complicated. Become.

From this point of view, the present invention has a simple configuration, and the M
Regardless of the missing bucket in the data part due to the error in part C,
To provide a method that does not cause a timing shift in descrambling.

(d) Means for Solving the Problems The present invention scrambles a binary digitalized facsimile image signal using redundancy suppression coding to provide confidentiality, and then multiplexes the signal onto broadcast radio waves and transmits the signal. In a facsimile broadcast transmission/reception method in which the receiving side performs descrambling processing to restore the image, the transmitting side divides the original image signal into blocks of N (integer) bits, and performs the same processing for each block of signals. A scrambling process of scrambling in units of N bits, a bucket configuration process of configuring an image signal bucket based on the scrambled image signal in units of N bits, and a transmission process of multiplexing the bucket onto a broadcast wave and transmitting it, On the receiving side, there are a receiving process for receiving the facsimile image signal bucket, a descrambling process for descrambling the received image signal in N bit units, and an image restoration process from the descrambled signal. It is characterized by including.

(e) Effect: According to the above means, since the H2N command is to perform scrambling in units of N bits for each block in which the image signal is divided into N (integer) bits, data bucket omissions due to transmission errors are prevented. There is no descrambling timing shift even in the case of

(f) Example An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1(a) and 1(b) are schematic explanatory diagrams of the scrambling method,
FIG. 2 and FIG. 3 are diagrams showing a transmitting side circuit configuration and a receiving side circuit configuration, respectively, for carrying out the method of the embodiment.

First, the scrambling method will be explained with reference to FIGS. 1(a) and 1(b).

That is, a pattern consisting of 176 bits is used as one key for scrambling. As shown in FIG. 1(a), the original image signal is divided into blocks of 176 bits from the beginning (these are called A and B).

C,----), and scrambles the image by adding the 176-bit pattern to each 176-pit image block. On the other hand, since the image signal in the data bucket part of the facsimile signal is bucketed in units of 176 bits as shown in FIG. 1(b) as in FIG. 5, the scrambling pattern for one image signal is common in all buckets. The same scrambling complete with 176 bits is applied.

According to such scrambling, even if a data bucket is missing on the receiving side, a timing shift in the descramp pull does not occur.

Also, according to this method, a maximum of (2176-1) keys can be used for scrambling. In facsimile broadcasting (excluding all 0s), in order to improve the time efficiency of transmission, the image signal is encoded using the MH or MR redundancy suppression encoding method and then sent as described above. In this case, if there is an error in transmission of even one bit in one packet of the image signal on the receiving side,
The line information contained in that bucket is decoded as a completely different image signal.

For example, the MH code is a data compression method that encodes information on the number of consecutive white and black dots into a variable length code for a binary (mill/black) image signal in one line and compresses the data. If there is an error, not only will the number of consecutive dots in that part be incorrect, but because of the variable length code, there will be a timing shift in subsequent code decoding, resulting in a completely different image being decoded. Also, to detect line errors, it is usually determined whether the number of dots in one line is a predetermined value (for example, 1728 dots on A4 size) for the decoded line signal, and if it is different, it is determined that there is an error. Since line interpolation is often used, the image information for that line is completely discarded.

On the other hand, an image signal bucket includes several lines of line information on average.

Therefore, if the scrambling key has a groove base that differs in several bits in a fractional manner as a whole compared to the 176-bit pattern, the content of the image will not be understood. An example of the structure of this key is to divide 176 bits into multiple blocks, and compare the scramble patterns in each block for scramble patterns in different keys.
The pattern may be configured such that the number of blocks containing the same value is 0 or within a predetermined number.

For example, when 176 bits are divided into N blocks and the scramble patterns for different keys are compared for each block, the following configuration can be used to ensure that the scramble patterns do not contain the same value.

That is, as shown in FIG. 1(c), 176 bits are divided into 11 blocks (B1 to B11) in units of 16 bits, and B1
Once the value of the block (16 bits) is determined, B2 to Bl
The configuration is such that the value of the block l is uniquely determined.

For example, using the Bl pattern (scramble) as a key, 1
Expressed as a value converted to 0-decimal number, this is defined as P, and the value of B2 is 1 to P+. B3 is 2 to P+ Bi is P+
A pattern can be easily generated by configuring a binary display pattern corresponding to a numerical value K1-1 (Ki is an integer of 1 or more) as a scramble pattern for each block. However, Ki+Kj (when i+j) is used so that Ki does not overlap between blocks.

In addition, when P+Ki exceeds Q=z+$1, it is set as P+Ki −* P+Ki −Q.

A simple way to determine Ki is Ki=i-1. That is, the number to be added is increased by 1, such as adding 1 to B2 and adding 2 to B3.

The scramble key for this method is 2+5-1 (all 0
There are approximately 65,000 patterns (excluding patterns of 1), which is sufficient for practical use.

Next, the transmitting/receiving circuit will be explained according to FIGS. 2 and 3.

In Figure 2, (1) is an MH and MR encoding circuit for image signals, and (2) is an image signal that adds control codes such as EOL (line synchronization signal) to the encoded image data to create an image signal sequence. The generation circuit (3) divides the image signal sequence into blocks of 176 bits from the beginning, and adds (mod
2), and the image signal is scrambled by this circuit.

Incidentally, the scramble pattern generation circuit (4) uses the key value P(
It can be configured with a circuit that converts a decimal number) into a binary pattern and an adder circuit that adds Ki to each block B1, and there is no need to store the scramble pattern in memory.

This scrambled image signal is converted into a signal format for facsimile broadcasting by a frame generation circuit (5) and a frame generation circuit (6), and is further converted into a signal format for facsimile broadcasting by a modulator (7).
), the signal is subjected to four-phase differential phase modulation, and then multiplexed with an audio signal and transmitted as a broadcast wave.

In the receiving side circuit of FIG. 3, (11) is a tuner, which outputs a composite signal including a facsimile signal and voice, and demodulates it by a demodulator (12) using a four-phase differential phase modulation system.

The demodulated signal is frame synchronized by a frame synchronization circuit (13), and then decomposed into frames in a signal separation circuit (14) and separated into an MC part and a data bucket part (15).
The MC identification circuit (16), which identifies the information of the MCmC and determines whether it is a paid facsimile broadcast
) is an image data bucket extraction circuit that validates the information in the data bucket part when the identification signal is for the pay broadcast, and extracts the image signal bucket in units of 176 bits. The 176-bit descrambling pattern output from the scrambling pattern generation circuit (18) is added (mod 2
) is a circuit.

Note that the descramble pattern generation circuit (18) is configured similarly to the scramble pattern generation circuit (4).

As a method for inputting the key information, the recipient may key in the form of a personal identification code, or insert an IC card storing the key information.

(19) is a composite circuit that performs MH and MR decoding on the restored data from the decrambling adder circuit (17).

In the above embodiment, common scrambling is applied to all image signal buckets by setting the unit of the pattern that is the key for scrambling to be the same number as 176 pits, which is the unit of the image signal bucket. Therefore, if a bucket is missing due to a transmission error during reception, the conventional method causes a timing shift in descrambling, and this shift affects subsequent image data, making it impossible to restore it.This method solves the problem. We can solve that problem.

Further, the scrambling process is simple, as shown in FIG. 2, by simply dividing the original image signal into 176 bits and applying a common scrambling pattern to each bit. Similarly, for descrambling, 176
The circuit configuration is simple because a predetermined pattern of 176 pits is simply added to the image bucket in units of bits, and no special synchronization circuit for descrambling is required.

Incidentally, the groove bottom element in the above embodiment may be constructed by a hardware logic circuit or may be constructed by software.

Furthermore, the scramble pattern generation circuit (4) and the descramble pattern generation circuit (18) may be a well-known PN (pseudorandom) signal generation circuit using a shift register array based on a generator polynomial; however, in this case, By performing tlI so that the shift register for scramble generation is initialized at the beginning of each block of N bits of the image signal, the PN signal string for each block can be made the same.

Next, another embodiment of the present invention will be described with reference to FIGS. 6 to 9. Fig. 6 is a schematic explanatory diagram of the scrambling method, Fig. 7 is an explanatory diagram of the main part, and Figs. 8 and 9 are diagrams showing the transmitting side circuit configuration and receiving side circuit vi precepts, respectively, to realize the embodiment method. be.

The difference in FIG. 6 from the first embodiment shown in FIGS. 1 to 3 is that the 176-bit scramble pattern that is added to each block obtained by dividing the image signal into 176-bit units from the beginning is a PN pattern. It is a point. This PN pattern is generated based on a key for the PN pattern, and is initialized for each beginning of the image signal of each bucket using a PN signal generator composed of, for example, an S-type feedback shift register, that is, it is locked. If the initial settings are made using the bit string corresponding to all or part of the initial setting value, bucket-complete addition can be performed.

Furthermore, the 176-bit image signal after PN addition is converted into M=8
The point is that substitution conversion processing is performed for each bit-based block bl, b2, . . . .

What is substitution conversion processing?Magazine ``Nikkei Electronics J197''
As introduced in the April 1999 issue, this is a method of converting an input bit pattern according to a conversion table showing the relationship between the input bit pattern and the output bit pattern, and is realized, for example, by the method shown in FIG.

In other words, the address is the total (8+K) bit value of the bits (e.g., 8 bits) and each 8-bit data that constitute the key for substitution conversion, and is output from the ROM that stores the contents after substitution conversion in the data section. 8-bit data CI, C2.
...Achieved by using C22.

Image signal blocks A”, B”, etc. after substitution conversion are the first
The data is converted into packets and formatted in units of 176 bits as shown in Figure (b).

Next, the transmitting/receiving circuit will be explained according to FIGS. 8 and 9.

In FIGS. 8 and 9, the same components as in FIGS. 2 and 3 are denoted by the same reference numerals, and their explanations will be omitted. The difference in Fig. 8 from Fig. 2 is the PN pattern generation circuit (4゛).
After adding the 176-bit pattern obtained by mod 2 using a PN pattern addition circuit (3'), the 176-bit pattern is scrambled by substituting it in 8-bit units using a letter conversion circuit as shown in FIG. Also, what is different in FIG. 9 from FIG. 3 is the image bucket extraction circuit (16
) is subjected to the reverse conversion process on the transmitting side based on the scramble key in 8-bit units, and the inversely converted signal is output from the PN pattern generation circuit (18') in 176-bit units. The addition of mod 2 with the 176-bit scramble pattern is performed using an adder circuit (17
').

According to this embodiment, scrambling is processed in such a way that every 176-bit packet is completed, so even if the data bucket part is discarded due to a transmission error in the MC part, the data bucket of services other than paid facsimile broadcasting is This is the same as the first embodiment in that there is no problem of descrambling synchronization in any case where it is discarded.
After the PN signals are added, substitution conversion is further performed, which has the advantage that it cannot be easily deciphered illegally, and that scrambling with high secrecy can be applied.

Incidentally, in the second embodiment shown in FIGS. 6 to 9, a scramble pattern generating circuit similar to that of the first embodiment may be used. In addition, a substitution conversion circuit (10), a reverse substitution circuit (20)
) may be replaced by a transliteration circuit, that is, a circuit that uses a method of rearranging the order of the bits of the input pattern, or a circuit that uses a method that combines the transliteration method and the substitution method.

Furthermore, in both the above-mentioned first and second embodiments, as a method of scrambling and descrambling in N-bit units, m of N-bit scramble patterns are used for each N-bit block.
Although o d 2 addition is used, the present invention is not limited to this, and it is also possible to perform scrambling and descrambling in units of N bits using a transposition method and/or a substitution method.

(G) Effects of the Invention As described above, according to the present invention, even when a data bucket is dropped due to a transmission error in the MC section, a timing shift in descrambling does not occur, and it is useful as a pay broadcasting system in facsimile broadcasting. It is.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are schematic explanatory diagrams of a scrambling method in an embodiment of the present invention, and FIG. 2 is a circuit diagram of a transmitting device for broadcasting based on the scrambling method of the embodiment. FIG. 3 is a circuit diagram of a receiving side device for receiving broadcasting based on the scrambling method of the same embodiment, FIG. 4 is a frame configuration diagram of a facsimile signal in facsimile broadcasting, and FIG. 5 is a bucket configuration diagram of a facsimile signal.
6 to 9 show a second embodiment of the present invention, FIG. 6 is a schematic explanatory diagram of a scrambling method corresponding to FIG. 1(a), and FIG. 7 is a main part WI of FIG. 6. 8 and 9 are circuit diagrams corresponding to FIGS. 2 and 3, respectively. (3) (3') = -addition circuit for scrambling, (4) (
4') - = Scramble pattern generation circuit (17) (1
7') - adder circuit for descrambling, (18) (18'
)--descramble pattern generation circuit, (10)--fold character conversion circuit, (20)--reverse substitution conversion circuit.

Claims (3)

[Claims] (1) After scrambling the binary digitalized facsimile image signal using redundancy suppression coding to provide confidentiality, it is multiplexed onto broadcast radio waves and transmitted, and the receiving side performs descrambling processing to convert the image into In a facsimile broadcast transmission/reception method for restoration, on the transmitting side, a scrambling process is performed in which the original image signal is divided into blocks of N (integer) bits, and the signal of each block is scrambled in the same N bits; It includes a bucket configuration process of configuring an image signal bucket based on the scrambled image signal in units of N bits, and a transmission process of multiplexing the bucket onto broadcast waves and transmitting the image signal bucket. A facsimile broadcast transmission/reception method comprising: a receiving process; a descrambling process for performing decrambling in N-bit units on the received image signal in N-bit units; and an image restoration process for restoring an image from the descrambled signal. (2) In the method for transmitting and receiving facsimile broadcasting according to claim (1), the scrambling and descrambling in units of N bits converts a binary pattern of N bits created based on a key into a mod 2 for each block of N bits.
A facsimile broadcast transmission/reception method characterized in that the facsimile broadcast transmission/reception method is performed by adding . (3) In the method for transmitting and receiving facsimile broadcasting according to claim (2), on the receiving side, the N-bit data after the mod2 addition process is further divided into m (integer) pieces M (=N/m).
) Contains a conversion process that converts a bit unit block by transliteration and/or substitution process, and the sending side converts the N-bit data after addition processing of the N-bit binary pattern with the same key as the sending side. On the other hand, M-bit inverted characters and /
Or, a facsimile broadcast transmission/reception method characterized by including an inverse conversion process for performing substitution conversion.