JPS63142987A - Scrambling method for television signal - Google Patents

Abstract

PURPOSE:To improve secrecy, by varying a signal component to be mixed on a transmission side in a real time by a random number circuit set corresponding to the random number circuit on the transmission side on a reception side, and negating a noise signal superimposed on a received television signal by using a table of random number on the reception side. CONSTITUTION:A synthesizer 126 generates plural frequencies based on a signal from a reference oscillator 125 consisting of a liquid crystal oscillator. Also, a frequency component generated from the synthesizer 126 is turned ON/OFF by the signal from the random number circuit 124, and after the phase of the component is corrected by a phase correction circuit 127, it is mixed with a television signal. The received television signal takes out a frame synchronizing signal at a synchronization extraction circuit 228, and supplies it to the random number circuit 224. A frequency generation circuit consists of a reference oscillator 225, a synthesizer 226, and a phase correction circuit 227 similarly as the transmission side, and a frequency signal for secrecy generated based on the table of random number is mixed at a mixing circuit 229 after shifting a phase by 180 deg.. By the above mixing, a secrecy signal is erased and is supplied to a demodulator.

Description

[Detailed Description of the Invention] [Summary] When adding secrecy to a television signal by superimposing a noise signal, a random number table is used to change the signal components to be mixed on the transmitting side in real time, and the signal components are superimposed on the received television signal. This ensures strict confidentiality by canceling out the generated noise signals using a random number table on the receiving side.

[Industrial application field]

The present invention relates to a method for scrambling television signals to improve confidentiality.

For example, in the case of pay television broadcasting, it is desirable to propose a method for processing transmitted and received television signals that allows only those who have paid the viewing fee to receive the television signal and prevents unauthorized viewing by others. .

[Conventional technology]

Conventionally, a method has been used in which cables and television equipment are modified to make it impossible to receive signals using a normal connection or a normal TV receiver.

FIG. 6 is a conventional television signal waveform diagram.

Figure a) shows a normal synchronization signal waveform. However, the same figure b
), the sync signal level is extremely low.

When the synchronization signal level is lowered in this way, when a normal television receiver is used, it becomes impossible to reproduce the synchronization signal, resulting in loss of synchronization.

Therefore, a special synchronization signal regeneration circuit must be installed to reproduce the synchronization signal. In other words, normal signals cannot be reproduced unless changes are made to the television device, so it is possible to prevent unauthorized viewing of the television signal. .

Another possible method is to superimpose a plurality of frequency components that become noise on the television signal, thereby interfering with the reception of the television signal.

[Problem that the invention seeks to solve]

The method of lowering the synchronization signal level described above has the problem that it is difficult to completely prevent eavesdropping because the synchronization signal reproducing circuit is easy to manufacture.

In addition, the method of superimposing multiple unnecessary frequency components on a TV signal to prevent eavesdropping uses a fixed frequency as the signal to be superimposed, and since there is no change in each frame, the superimposed frequency components are There is a problem in that it is easily revealed through analysis and cannot be avoided from being viewed by someone else.

[Means for solving problems]

The above problem is solved by the random number table circuit 2, as shown in the principle diagram of the present invention shown in FIGS. 1a and 1b. A plurality of frequency components generated from the above are mixed into a television signal in a mixer 5 and sent out, and the mixed frequency components are sent to the transmitting side random number table circuit 2 on the receiving side.
The random number table circuit 11, which is set corresponding to This problem is solved by the television signal scrambling method of the present invention.

[Effect]

Random numbers are set in the random number table circuit 2 in advance by the random number setting device 1. Every time the frame synchronization signal of the television signal is extracted from the synchronization extraction circuit 4, the random number table circuit 2 changes the output signal,
The combination of frequency components generated by the frequency generating circuit 3 is changed.

In the mixing circuit 5, different combinations of frequency components are mixed into the TV signal for each frame, and since the combinations are based on a random number table, the frequency components are analyzed on the receiving side, and the same random number settings as on the transmitting side are set in the random number table circuit. . The random number table circuit 11 changes the output signal in synchronization with the transmitted frame signal,
The frequency generating circuit 12 generates a combination of frequency components that is the same as the combination of frequency components superimposed on the received frame.

The frequency of this frequency generating circuit 12 is supplied in opposite phase to the mixing circuit 9, and by eliminating the scrambled signal from the transmitting side, a television signal free from interference is obtained.

Correct reception of television signals is possible only by providing the receiving side with a random number table corresponding to that on the transmitting side.

〔Example〕

The present invention will be described in detail according to the illustrated embodiments.

FIG. 2 shows a transmitting device of the present invention, and FIG. 3 shows a receiving device,
An example is shown for each.

A television signal as shown in FIG. 4a) is input to the synchronization extraction circuit 128. The output of the synchronization extraction circuit 128 is the mixing circuit 1
29, and the frequency for scrambling is mixed.

The synchronization extraction circuit 128 also provides a signal to the random number table circuit 124 on a frame-by-frame basis.

The random number table circuit 124 changes the output for each frame, and the reference oscillator 125, synthesizer 126, phase correction circuit 12
Synthesizer 126 in the frequency generation circuit consisting of 7 etc.
Change the random number given to .

Further, the synchronization extraction circuit 128 supplies a reference signal to the phase correction circuit 127 of the frequency generation circuit.

An example of the frequency components mixed in the mixing circuit 129 is shown in FIG. 4b). As the mixed signal, N frequencies covering the frequency components of the audio signal 41, color signal 42, and brightness signal 43 in the television signal are selected, and these frequencies f1 to fn are used as secret signals.

The signals of each frequency are turned on and off by the random number table circuit 124 for each frame.

At this time, if the signal strength is determined to be m times that of the synchronization signal, processing on the receiving side becomes easier.

In FIG. 2, the random number table of the random number table circuit 124 is input to the CPU by manual input from the random number setting input device 123, for example.
The data is once written into the main memory 122 under the control of the random number table circuit 121 , and then written from the main memory 122 into the random number table circuit 124 . In FIG. 1, these parts are shown as a random number setting device 1.

As shown in FIG. 5, the random number table circuit 124 receives a secret signal f1.
~fn is turned on and off for each frame. Assuming that the period of the random number table is T, a matrix of TXN is created. In the table, on is indicated by 1 and off is indicated by 0.

The synthesizer 126 is a reference oscillator 1 consisting of a crystal oscillator.
A plurality of frequencies are generated based on the signal from 25. In addition, the synthesizer 126 receives a signal from the random number table circuit 124.
The frequency components generated from the signal are turned on and off, and after their phase is corrected by a phase correction circuit 127, they are mixed into the television signal.

For example, if we put 8 frequencies in the audio signal, 8 frequencies in the color signal, and 16 frequencies in the video signal as secret signals and create a random number table with a period of 32 frames, the random number table has a capacity of 1 kilobit, and the synchronization of the random number table It takes about 1 second at most.

It is folded. The trigger signal is used to synchronize the random number table circuit on the receiving side and is placed in the first or last scan line of the frame.

FIG. 3 shows an embodiment of the receiving device.

A synchronization extraction circuit 228 extracts a frame synchronization signal from the received television signal and supplies it to a random number table circuit 224. Additionally, the trigger extraction circuit 230 notifies the starting point of the random number table.

The frequency generation circuit consists of a reference oscillator 225, a synthesizer 226, and a phase correction circuit 227, as on the transmitting side, and the random number table shows that the generated secret frequency signal has a phase of 18
The mixture is shifted by 0 degrees and mixed in the mixing circuit 229. This mixing eliminates the secret signal and supplies it to the demodulator.

CPU 221, main memory 222, random number setting input device 22
3 corresponds to 10 in FIG. 1b.

The random number setting input device 223 is changed according to the random number setting situation on the sending side, and for example, as a ROM card,
distributed to viewers. Settings for the random number table circuit are performed in almost the same way as on the transmitting side.

C. Effects of the Invention] According to the present invention, unless the receiving side is equipped with a random number table that is the same as the random number table provided on the transmitting side, the received television signal cannot be viewed normally, and television broadcasting with extremely high secrecy is prevented. is possible. Moreover, the generation and superposition of the secret signal can be realized with a simple circuit configuration, and its effects are extremely large.

[Brief explanation of the drawing]

1a and 1b are diagrams of the principle of the present invention, FIG. 2 is a block circuit diagram of an embodiment of the transmitting device of the present invention, and FIG. 3 is a block circuit diagram of an embodiment of the receiving device of the present invention. FIG. 4 shows an example of a television signal and scrambling frequency, FIG. 5 shows an example of a TXN matrix random number table, and FIG. 6 shows a conventional television signal waveform diagram. In the figure, ■, 10 is a random number setting device, 2.11.124.224 is a random number table circuit, 3.12 is a frequency generation circuit, 4.7.128.228 is a synchronization extraction circuit, 5.9.12
9.229 is a mixing circuit, 6.131 is a transmitter, 8.230 is a trigger extraction circuit, and 121.221 is a CPU. 122.222 is a main memory, 123.223 is a random number setting input device, 125.225 is an oscillator, 126.226 is a synthesizer, 127.227 is a phase correction circuit, and 130 is a trigger superimposition circuit. Engagement gF4's cooling round 'I7 Ia Figure Ice Breathing Principle Turning Power 1b Invention 771 Received Narrow I Car Refresh - Implementation Row 7F Diary - Column 3 Mouth 1-1 Fortune 1 Symbol Otsu a - Chiko record ° 4 and the same number for flan file 1t n - *
Figure 1 No. 4 Number of plants in one cycle f A major example of a T×N matrix random number table No. 5 Figure 6

Claims (1)

[Claims] A random number table circuit (2) generates a plurality of frequency components generated from a frequency generation circuit (3) whose output frequencies are combined by the output of a synchronization extraction circuit (4) for each frame, and a mixer (5). The mixed frequency components are sent out after being mixed with the television signal at the receiving side, and the mixed frequency components are sent to the random number table circuit (1) set corresponding to the transmitting side random number table circuit (2).
1), a plurality of frequency components generated from the frequency generation circuit (12) whose combination of output frequencies changes depending on the output of the synchronization extraction circuit (7) for each frame and a mixer (9) on the transmitting side. is a method of scrambling television signals characterized by mixing and removing them in opposite phases.