JPH057917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television signal transmission device that records and then reproduces scrambled broadcasting.

Recently, a scrambled broadcasting system has been proposed in which a broadcasting station scrambles and transmits a television signal of a specific program so that subscribers to the broadcasting station can view the specific program via a decoder. This system uses a scrambled signal obtained by scrambling a television signal of a specific program by, for example, reversing the polarity at a predetermined period or changing the order of the signals at a predetermined period, and a key code for decoding the scrambled signal. Therefore, even if this scrambled signal is received by a normal TV receiver, the original images and audio cannot be viewed.
Only subscribers can use a decoder to restore (descramble) the scrambled signal using a key code and view the original images and audio of a specific program.

In the past, when a scrambled signal was recorded on a VTR and then played back, flickering occurred, and there was a risk that a third party might find out that some of the content was simply descrambled. Furthermore, if distortion occurs in the transmission system, the original state cannot be restored even if proper descrambling is performed.

The present invention provides a transmission device suitable for recording and reproducing scrambled broadcasts on a VTR or the like, and when selecting and reproducing one program from a plurality of recorded programs, key It is designed to identify the code.

Embodiments of the present invention will be described below with reference to the drawings.

First, an embodiment of a method for scrambling a television signal will be described.

In scrambled broadcasting, it is important to hide the contents of the scrambled signal as much as possible when it is received by a normal receiver.

In a method for inverting the polarity of a television signal, the television signal is inverted at a predetermined field period. If the scrambled signal obtained by this method is affected by distortion in the transmission system, it will not correctly return to its original waveform when descrambled on the receiving side. For example, when a signal whose polarity has been inverted is inverted again by a decoder, flickering occurs at the polarity inverted portion. Such flickering is particularly noticeable when the screen is close to a still image. Also, when recording scrambled broadcast programs on a VTR,
has nonlinearity in direct current or alternating current, so
Flickering is particularly likely to occur.

This embodiment solves the above-mentioned problem in the scrambling method that performs polarity reversal.

First, as shown in FIG. 1, a predetermined cycle T (for example, 60 seconds) is set in the television signal of a specific program to be scrambled using an index signal ID, and a screen transition portion of the specific program is detected. Screen change signal (scene change signal)
Get SC. Furthermore, a key code or pattern _P1 is determined. In this pattern _P1 , the rising and falling points are synchronized with the field period, and the signal ID,
In cooperation with SC, one of scramble patterns P ₂ , P ₃ , and P ₄ that determines polarity reversal is formed. These patterns P ₂ , P ₃ or P ₄ are scrambled by reversing the polarity of the video period of the television signal of the specific program, for example in the high level portion. Note that the key code pattern _P1 is repeated at a period T.

Pattern _P2 is an AND of ID or SD and _P1 , and the level is inverted at this AND output. In pattern P ₃ , the rising edge is executed at ID or SC,
The falling edge is executed at the falling edge of pattern _P1 .
Pattern P ₄ has a rising edge between ID or SD and P ₁ .
It is executed with AND output, and the falling edge is executed with SC.

The scramble pattern that determines polarity reversal is
In addition, various patterns can be formed based on ID, SC, and _P1 .

According to this embodiment, since polarity reversal is always performed at the same time as screen switching, the above-mentioned screen flickering becomes less noticeable. Furthermore, since the polarity is reversed by combining the screen change and the key code pattern _P1 , the scrambling effect is enhanced. Furthermore, since the descrambling method becomes difficult to decipher, security is improved.

Note that the signals ID, SC, and _P1 are each encoded with a predetermined number of bits, as will be described later, and are inserted into a predetermined position of the television signal and sent out. The decoder on the receiving side detects these ID, SC, and _P1 , restores the scramble pattern, and performs descrambling to restore the polarity of the scrambled image signal based on this scramble pattern.

Next, various signals sent out from a broadcasting station along with a scrambled specific program and their sending method will be described.

FIG. 2 shows the format of a scrambled broadcast television signal transmitted from a broadcasting station.

During the video signal period, a scrambled specific program, address code, program code, and key code are transmitted in this order. During the vertical blanking period, the program code, ID, SC code, address mode, key mode, stop code, etc. are transmitted in this order.
A scrambled program is sent out on the audio channel. Note that the audio signal may be scrambled in various ways using, for example, the scrambling pattern described above. Further, each code is transmitted as a signal obtained by NRZ modulating a binary signal of a predetermined number of bits.

The address mode is a coded number assigned to the subscriber in advance, and includes regular mode and special mode. When broadcasting a normal scrambled program in regular mode, the broadcasting station sends out the number codes of subscribers (for example, non-payers) who are not allowed to receive the program. If the decoder of the subscriber corresponding to this number detects his own number code, descrambling becomes impossible.
When transmitting a scrambled broadcast of a special program in special mode, only the number code of the special subscriber is transmitted. Therefore, only a decoder that detects this number code can descramble.

The key code is a decoding key code when descrambling a scrambled signal, and has, for example, a code specifying pattern _P1 in FIG. 1. In this embodiment, this key code is added to the end of the broadcast so that descrambling cannot be performed unless the scrambled broadcast is once recorded on a VTR or the like. For example, you can convert scrambled broadcast signals to a VTR.
Finally, store the key code in a memory, read the key code during playback,
Based on this, the reproduced signal is descrambled. That is, by adding a key code to the end, it is made impossible to view the program in real time. Note that the key code may be added to the starting edge of the program prior to the start of the program, and stored in the memory when a predetermined period of time has passed after detecting this starting edge (for example, when most of the program has elapsed), or the key code may be added to the starting edge of the program. It may be divided into a terminal portion and a terminal portion.

The program code is a code that specifies a key code. On the other hand, in order to prevent the key code from being decoded by anyone other than the subscriber, the key code is
It changes every day and every program. Therefore, when multiple programs are recorded on a tape, or when there are multiple recorded tapes, various key codes will be stored in the memory. The program code has content unique to the program, and the program code and key code are stored in memory in correspondence. Therefore, during playback, the corresponding key code can be selected depending on the playback program code. In this embodiment, this program code is expressed by a broadcast date and a program number.

This program code is inserted into the vertical blanking period as shown in FIG. 3 along with the ID and SC code. Note that the program code, ID, and SC code are inserted into the 14th and 15th horizontal scanning periods (hereinafter referred to as 14th and 15H) of the vertical blanking period, respectively.

In Figure 3, the program code PC is approximately 20
70V (V: field period) is continuously inserted at second intervals. That is, 70V each 14, 15H PC
is inserted, and this is repeated every 20 seconds. During this time, ID and SC codes are inserted into 14 and 15H, and this is repeated until the end of the program. PC and ID,
If the SC and SC match, one can be prioritized and the other shifted. In that case, it is better to move the PC. As shown in Figure 2, the program code is sent out 10V prior to programming. During this 10V period, the receiving side detects that it has received scrambled broadcasting and enters the operating state.

As mentioned above, by adding a program code to the entire period during which the program is being sent, the program code can be detected immediately and the key code can be specified no matter where the tape is played back from. . Because of this, pause during playback,
Even if you perform fast forwarding, rewinding, etc., descrambling can be performed immediately.

The address mode is sent during the address code sending period, and indicates whether the address code is currently being sent, regular mode or special mode, and 14.
Inserted at 15H.

The key mode indicates that a key code is being sent and is inserted into 14 and 15H.

Stop indicates that scrambled broadcasting has ended and is inserted at 14 and 15H.

Next, the data structure of each code mentioned above will be explained.

As shown in FIG. 4, the program code consists of 24 bits _d0 to _d23 representing the year, month, day and program number. Each bit is assigned as shown in FIG. 5 depending on the content. In FIG. 4, television signals S 14 and 15H are each divided into five periods, and one bit is assigned to each period. Note that HD is a horizontal synchronization signal and SB is a color burst signal.
First, a guide code indicating that it is a program code is added to 14 and 15H of the first field period _V1 in the illustrated code pattern. Then V ₂ ~
Six fields of V ₇ are added as shown along with bits β ₀ -β ₄ and 0. This configuration of V ₁ to _{V 7} is made into one program code as one pack, and this is 70V (10 packs) as shown in Figure 3.
Repeat at approximately 20 second intervals.

FIG. 6 shows the structure of the address code.

The scrambled broadcasting system according to this embodiment is assumed to have, for example, several hundred thousand to several hundred thousand subscribers. This makes it impossible to represent the subscriber number with a limited number of bits. Therefore, in this embodiment, the subscribers are divided into a plurality of groups, and a number is assigned to each group. Therefore, a subscriber will have a subscriber number consisting of a group number and a number within that group. In this embodiment, the group number is expressed as a group code using 20 bits _d1 to _d20 , and 50 people are assigned to each group. These 50 people are represented by 50 bits as a home code, and each person is assigned 1 bit. For example, the subscriber code of number 5 in a certain group represented by d ₁ to d ₂₀ is "d1...d ₂₀
0001000…00”. That is, the 5th bit of the 50 bits of the home code is set to "1",
All other bits are set to "0".
Such an address code is sent together with the aforementioned program code after a video period is inserted after the program ends.

Between 30H and 34H of the signal S, d ₁ to _{d 20} representing the group code mentioned above are inserted. Note that M ₁ to M ₂ inserted in 30H are codes for specifying scramble broadcasting, for example, broadcast channels. Also above 50
Bit's home code is E ₁ ~ E ₅₀ , and this is 39
Divide into ~43H and 48~53H and insert. However, E ₅₀
is inserted into 34H. C ₀ to C ₄ and P are error correction bits based on Hamming codes. Also 36-38H, 45
The 0 bits in each section from ~47H and from 54 to 57H are blank times in consideration of the calculation time of the microcomputer in the decoder.

As mentioned above, 30 to 56H represent one group of 50 people, and this is group A-1. Next, this A-
Invert all the codes in one set to make the A-1 set, and insert this into 57-83H. Note that this A-1 set is used for error correction. The next 50 people will be inserted into Group A-2 from 84 to 110H, and then Group A-2 will be inserted. Similarly, A-3, A-3, A-4, A-4
Insert each pair to represent a total of 200 people. Next, insert the program code PC mentioned above into 246-251H along with bits β ₀ to β ₄ , and further insert bit 0.
Insert between 252 and 254H. Next, insert the inverted PC signal into 256-261H, and add a 0 bit.
Insert between 262 and 264H. If the above is considered as one pack, it will be approximately one field, and this will be repeated for even number and radix fields. Repeat one pack containing 200 different people, and all the subscribers will be represented by a total of N fields. The transmission of the address code is completed by repeating these fields 1 to N four times with the same content. Note that the reason why the same content is repeated four times is to prevent detection failures on the decoder side.

The key code is sent out during the video period after the address code is sent out, as shown in FIG. This key code is arranged in 5 bits each between 30 and 38H, and includes codes d ₁ to d ₂₃ and error correction codes C ₀ to _{C 4} ,
It is expressed as P. Adding 3H periods of no signal of 0 bits to this is one pack, and this one pack of 9H worth of data is repeated at, for example, 10V.

The ID, SC, address mode, key mode, and stop code are inserted by assigning predetermined code patterns of 5 bits to 14 and 15H of the vertical blanking period, respectively, as shown in FIG.

A transmitting circuit, a receiving side decoder, etc. for the scrambled broadcast signal shown in FIG. 2 having each code and scrambled program having the data structure as described above will be described.

FIG. 9 shows an embodiment of a circuit for scrambling on the transmitting side.

A video signal S of a specific program to be scrambled is applied to an input terminal 1, and an audio signal S _a of the specific program is applied to an input terminal 2. The signal S is applied to the video scrambler 3 and
In addition to the screen change signal generation circuit 4, the screen change portion is detected, and for example, the signal SC shown in FIG. 3 is obtained.

On the other hand, the synchronization separation circuit 5 separates the horizontal and vertical synchronization signals HD and VD from the signal S. The timing signal generation circuit 6 generates a synchronization signal and a blanking signal based on the signals HD and VD to drive the controller 7 and the data insertion circuit 8. Based on instructions from the controller 7, the data insertion circuit 8 creates data for each code shown in FIG. 2 and outputs it at a predetermined timing. The controller 7 generates the key code or pattern _P1 shown in FIG. 1 and applies it to the video scrambler 3 and the audio scrambler 9. video scrambler 3
determines the scramble pattern P _{2 ,} P ₃ or P ₄ in FIG. 1 based on the signal SC and the above pattern P 1,
This scrambles the signal S.

The data/video mixing circuit 10 combines the scrambled program and each code and outputs the result to an output terminal 11 as a scrambled video signal _Ss . Furthermore, the audio scrambler 9 scrambles the signal S _a and outputs it to the output terminal 12 as a scrambled audio signal S _as .

FIG. 10 shows an embodiment of a decoder on the receiving side. Furthermore, this decoder is for example
Connected between the VTR and monitor receiver.

When a scrambled broadcast is recorded on a tape using a VTR, the program code and key code of the program are stored in correspondence with each other in the nonvolatile memory 13 of the decoder.

When the tape is reproduced, the reproduced scrambled image signal S _s is applied to the video descrambler 15 from the input terminal 14, and the reproduced scrambled audio signal S _as is applied to the audio descrambler 17 from the input terminal 16. Synchronous separation circuit 18
extracts the signals HD and VD from the signal _S and drives the controller 19 which also serves as code detection and the scramblers 15 and 17, and the data separation circuit 20 extracts the signals HD and VD from the signal S.
The data of each code is extracted from _Ss and added to the controller 19.

The controller 19 detects the ID and SC code, as well as the program code, reads out the corresponding key code from the memory 13, and executes these codes.
The IC, SC, and key codes are applied to the descramble pattern generation circuit 21. This generation circuit 21 restores a scramble pattern based on each code and applies this to the descramblers 15 and 17 as a descramble pattern. Descrambler 1
5 inverts the polarity of the signal _S according to the descrambling pattern, returns it to the original signal S, and outputs it to the output terminal 22.
Output to. The descrambler 17 returns the signal S _as to the original signal S _a and outputs it to the output terminal 23 .
These output signals S, S _a are applied to the line-in terminal of the receiver. In addition, the signals S and S _a are converted to the frequency of an empty TV channel by the RF modulation circuit 24,
The signal may be applied from the output terminal 25 to the antenna terminal of the receiver.

Fig. 11 is an explanatory diagram of the operation of the memory 13 during recording, and Fig. 12 shows the operation of the memory 13 during playback.
An explanatory diagram of the operation is shown.

During recording, the code discrimination section 27 in FIG.
First, the address code and address mode signal are detected from the signal sent from the VTR. During this recording, the VTR is put into recording mode EE, and a monitor signal is applied to the decoder. In the regular mode, when the address code includes the own decoder address (contractor number), the address matching determination circuit 28 detects this and stops the write control circuit 29 and write counter 30. Therefore, no key code is stored in the memory 13. If there is no decoder address in the address code, the program code and key code are stored in the memory 13 from the determination unit 27. Therefore, when a plurality of programs are recorded, program codes PC ₁ to PC _N and key codes KY ₁ to _{KY N} are stored in correspondence. In the case of special mode, it is stored only when the address code includes a decoder address.

During playback, the code discrimination unit 31 shown in FIG. 12 detects the program code from the played data.
It is added to the PC match determination circuit 33. The read counter 32 reads the program code PC ₁ ~ of the memory 13.
PC _N is read out sequentially and applied to the coincidence determination circuit 33. When the program code being reproduced matches the read program code, the corresponding key code is read. For example, ROM34 has 30
Data of different types of descrambling patterns are stored, and data corresponding to the read key code is read out. This data is applied to the descramble pattern generation circuit 21 shown in FIG.

The above is a case where a polarity reversal method is applied as a scrambling method, but the present invention can also apply various other scrambling methods.

As described above, the present invention records a television signal including a scrambled specific program, a key code for descrambling this specific program, and a program code for specifying this key code, and records these television signals on a VTR. A code and a program code are stored in correspondence with each other, and at the time of playback, a stored key code is selected according to the played program code, and a scrambled and recorded specific program is descrambled based on the key code. This relates to a television signal transmission device.

Therefore, according to the present invention, when a plurality of programs each having a different key code are recorded on a VTR, the key code of the program can be easily known from the program code reproduced during playback. Descrambling can be performed.

[Brief explanation of drawings]

FIG. 1 is a timing chart showing an example of a scrambling method applicable to the present invention, FIG. 2 is a diagram showing an example of the format of each code transmitted in scrambled broadcasting according to the present invention, and FIG. 3 is a diagram showing a program code and Figure 4 is a timing chart showing the relationship with other codes, Figure 4 is a diagram showing an example of the data structure of the program code, Figure 5 is a diagram showing the relationship between the contents of the program code and bits, and Figure 6 is the address code. 7 is a diagram showing an example of the data structure of a key code, FIG. 8 is a diagram showing an example of the data structure of other various codes, and FIG. 9 is a circuit block showing an example of the transmitting circuit. 10 is a circuit block diagram showing an embodiment of the decoder, and FIG. 11 is a circuit block diagram showing an embodiment of the decoder.
FIG. 12 is a block diagram explaining the operation of the memory during recording, and FIG. 12 is a block diagram explaining the operation of the memory during reproduction. In addition, in the symbols used in the drawings, PC,
PC ₁ ~ _{PC N} ...Program code, KY ₁ ~ _{KY N} ...
...Key code.

Claims (1)

[Scope of Claims] 1. Recording means for recording a television signal including a scrambled specific program, a key code for descrambling the specific program, and a program code for specifying the key code, the key code and the program. a storage means for storing each code in a corresponding relationship; a selection means for selecting the stored key code according to the reproduced program code when the recording means reproduces; and a selection means for selecting the stored key code according to the reproduced program code; and means for descrambling the scrambled specific program based on the selected key code.