JPS62230193A - Image scramble system - Google Patents

Abstract

PURPOSE:To execute a scramble having small scramble information and large disturbance in a circuit by executing the inherent scramble to the sections of horizontal synchronizing signals, color burst and video signals respectively. CONSTITUTION:Horizontal and vertical synchronizing signals separated from video signals by a synchronizing separator circuit 2 are inputted to a scramble control circuit 3. The control circuit 3 generates the random numbers of 0-8, and determines whether gain restriction is to be made or not to the sections of horizontal synchronizing signals, color burst signals and video signals based on the random number, and controls a gain control circuit 6, and at the same time, superposes the random number in the vertical fly-back lines as scramble information. Since the scramble is made in each section according to making or not making a fixed gain restriction, the circuit is made simple, and scramble information is lessened and the deterioration of signals is reduced. As scramble is made to each section respectively, the degree of disturbance to wrong receiving is large.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a video scrambling system, and particularly to a video scrambling system used in pay TV remote control broadcasting such as CATV.

(Prior art) In paid preview broadcasting on CATV, etc., the television signal is scrambled in order to enable normal reception only on specific receivers that have paid the reception fee or have a reception contract. It is necessary to perform the processing for t!A'!ll'.

To this end, the broadcasting station applies some kind of signal processing or modification (called scrambling) to the preview signal transmitted by the encoder, so that a normal television receiver cannot see the normal image.

Then, on the receiving side, reverse signal processing or reverse transformation (called descrambling) is applied at a decoder using a specific receiver for which a reception fee has been paid or a reception contract has been made, so that a normal image can be viewed.

One method for performing such scrambling processing is to add waveform scrambling and descrambling to a television signal shown in FIG. 9 in which a radio frequency (RF) carrier wave is modulated.

1H indicates one horizontal period.

Examples of this method include, for example, JP-A-60-15
As described in Publication No. 2188, the RF of FIG.
A horizontal synchronizing signal was embedded in the video signal by scrambling the television signal as shown in Figure 10 and attenuating the signal level of the horizontal 9I line erasure section of the television signal (the section indicated by the arrow in the figure). There is something that has been made to be a state.

In addition, as another example, for example, Special Publication No. 58-20191
As described in the publication, a sine wave signal or a similar signal having a frequency equal to or an integral multiple of the horizontal synchronization frequency as shown in Fig. 11 is used, and 8 Mam is added as shown in Fig. 12. There is a method in which the signal level of the IIF television signal shown in FIG. 9 is attenuated the most in the horizontal blanking section (the section indicated by the arrow in the figure). In this case, the horizontal synchronization signal is embedded in the video signal, and at the same time, the video signal is also scrambled in a form different from the original signal.

Note that in the above scrambling process, scrambling is performed uniformly for each horizontal section of a continuous television signal, but instead of scrambling for all horizontal sections, it is scrambled at regular intervals for each horizontal section. Nari 1 = Su, sometimes performed with irregular intervals.

In the above method, the horizontal synchronizing signal is basically undetectable, and a normal television receiver mistakenly recognizes the highest level portion of the video signal as the horizontal synchronizing signal.

Since the video signal is constantly changing, the horizontal synchronization becomes abnormal and, as a result, it becomes impossible to view the original video.

Next, the advantages and problems of the above two scrambling systems shown in FIGS. 10 and 12 will be described.

First, as for the method of level attenuating the horizontal blanking section shown in FIG. 10, the advantages are: 1) Scrambling and descrambling can be performed if both the encoder and decoder have gain control circuits, so the circuit configuration is simple. Only the scramble information and gain information to be transmitted is ■
Since the video signal is not scrambled, there is very little signal deterioration due to scrambling, and the quality of the descrambled bow is high. In addition, as a point of contact, if synchronization is forcibly established on the receiving side, eavesdropping becomes possible. For example, it is possible to interpolate the missing portion of the horizontal synchronization signal by using the vertical synchronization signal or the partially correct horizontal synchronization signal.

Next, the advantage of the method of AM modulation using a sine wave signal or the like shown in FIG. 12 is that the degree of disturbance is large as a scrambling method. Even if synchronization is forced on the receiving side, the video signal portion is also scrambled, so normal video cannot be viewed. In addition, the problems include: (1) The encoder and decoder require an AM modulator and AM demodulator with the same characteristics, which makes the circuit configuration complicated and is disadvantageous in terms of cost. (2) The scrambled information to be transmitted is also scrambled. In addition to on/off information, AMI key timing and AM change'mI! ! (1) Since scrambling is added to the video signal, signal deterioration due to scrambling is large and the quality of the Y-scrambled signal is poor.

(Problems to be Solved by the Invention) As described above, in the conventional RF television signal scrambling method, the degree of scramble disturbance is large, the amount of scrambled information transmitted is small, the circuit configuration is simple, and the scrambled signal It was not possible to fully satisfy all requirements regarding the amount of deterioration.

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned problems by providing a video scrambler that has a simple circuit configuration, reduces the amount of scrambled information transmitted, has little signal deterioration due to scrambling, and can perform scrambling processing with a large degree of disturbance. The purpose is to provide a method.

[Structure of the Invention] (Means and Effects for Solving the Problems) According to the video scrambling method of the present invention, when a television signal obtained by RF modulating a composite color video signal is scrambled, Video scrambling is performed using a unique scrambling method for at least three sections of the signal, including the horizontal synchronization signal section, color burst section, and video signal section. It is sufficient to descramble each section using a unique descrambling method (corresponding to the above-mentioned unique scrambling method).

(Example) Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of an encoder and decoder to which the video scrambling method of the present invention is applied, and FIG. 2 is a waveform diagram showing an example of an RF television signal to explain the video scrambling method of the present invention. be.

In FIG. 1, reference numeral 1 indicated by a broken line frame is an encoding part, and the input composite color video signal is supplied to a sync separation circuit 2 and a data convolution circuit 4, and the sync separation circuit 2 converts the horizontal sync signal and The vertical synchronization signal is separated, and the horizontal synchronization signal and vertical synchronization signal are supplied to the scramble control circuit 3, and the scramble It, II control circuit 3 uses the two synchronization signals and the algorithm of the Ibl al1 circuit to control the gain control circuit and the Create a corresponding scrambled data signal. The scrambled data signal is superimposed on the video signal by the data superimposition circuit 4. This video signal is RF
The signal is RF-modulated by the modulator 5 and becomes an RF-modulated video signal (RF television signal). This RF television signal is supplied to a gain control circuit 6, and a gain control signal from the scramble control circuit 3 causes a
The signal is divided into two signal sections, each of which is gain controlled with a different gain, and is output as a scrambled RF television signal. The scramble control circuit 3 and gain control circuit 6 will be described later.

This scrambled RF television signal is input to a decoder 10 indicated by a broken line frame through a cable 20, detected by a detector 11, and the detected signal is input to a synchronization separation circuit 12 and a data detection circuit 13. The synchronization separation circuit 12 outputs a horizontal synchronization signal and a vertical synchronization signal, and the data detection circuit 13 outputs a scrambled data signal. These three signals are input to the descrambling control circuit 14 to create a gain control signal for ask crumple. In addition, the scrambled RF
The television signal is input to the gain control circuit 15, where it is descrambled using the gain control signal and is converted into a normal RF signal.
A television signal is output.

J5, in the above case, the scrambled data signal is converted to the composite video signalff! Although the signal is superimposed on the audio signal, it is also possible to use a circuit configuration in which it is superimposed on the audio signal or transmitted using a separate line.

Figure 2 shows the scrambled RF Luvision signal -
An example is shown, and this RF television signal has horizontal synchronization signal section A1, colorverse 1-section B, and video signal section C.
For the three sections, the gain 1. is different in each section. It is in a scrambled state by performing IJtlll (specific gain reduction). In the case of such a scrambling method, seven scrambling states are possible depending on the presence or absence of gain control for each section of A-C, and the scrambling effect on the video in each case is shown in Table 1. . The O mark indicates a case where gain control is provided in each section. Although this table shows the above seven cases, it is also possible to perform gain control on the vertical blanking section or a part thereof if necessary. Note that the table above also includes the state without scrambling.

Below Margin The advantages of the scrambling method using gain control of different gains for the three sections A to C as described above are as follows. ■The circuit configuration is simple, requiring only a gain control circuit similar to the conventional scrambling method using level attenuation in the horizontal blanking section. (2) Since the scramble information to be transmitted is only related to the presence or absence of gain control in each section, there is little information captured. ■Even if synchronization is forcibly applied on the receiving side, the colors and brightness remain out of order, making it impossible to see a normal image, and the degree of disturbance caused by scrambling is large. ■When attempting to reproduce synchronization from the few remaining normal horizontal synchronization signals, color bursts and video signals act as false horizontal synchronization signals, causing malfunctions and making it difficult to reproduce images illegally. (2) No operation other than uniform gain control is applied to the video signal section. , deterioration of the video signal due to scrambling is extremely small.

FIG. 3 is a block diagram showing an example of the scramble control circuit 3. As shown in FIG. In this example, the scramble state can be switched every vertical period (1), and the scramble data signal determined based on the random number generator is m-folded in binary form during the vertical retrace period. And so. In FIG. 3, the random number sequence created by the random number generation circuit 21 is converted into a random number sequence from 0 to 7 by the remainder of 8 creation circuit 22. It is converted into 2 (000) to (111) by the binary number conversion circuit 23.
Convert to a base random number sequence. By the way, first, as an example of gain control of signal q, as shown in FIG.
The case where the color burst part and the video signal part are divided into three parts is shown, and these three parts are divided into a binary number sequence (000
) to (111), for example, the third digit 1.0 indicates the presence or absence of gain control for the horizontal synchronization signal part, and the second digit 1°0 indicates the gain control for the color burst part. presence or absence,
Let us assume that the first digit, 1.0, indicates the presence or absence of gain control for the video signal portion. Then, this 3-digit binary number sequence data is added to the center of gravity control data creation circuit 25 at a timing approximately corresponding to the (vertical period) timing pulse, and from this circuit 25,
By outputting the binary number string data after a period of time, the binary number string data can be superimposed on the horizontal cycle period that is included in the vertical retrace period. Note that the above four circuits 21, 22, 23, and 25 are controlled by the V timing pulse.

Now, the data of the previous three-digit binary number string is connected to the suppression start timing generation circuit 26A to 24 by the connection 24 for each digit.
26C. These circuits 26A to 26C are H
(Horizontal period) It is controlled by a timing pulse, and for example, if the input is "1", a pulse is generated after a predetermined time from the H timing pulse. For example, if the timing generation circuit 26B is compatible with color burst suppression, a pulse is generated at a time corresponding to immediately before a color burst and approximately 5 μsec later than the 1'' timing pulse. In other words, the timing generation circuit 268-2
6G determines the suppression start time of each of the three sections: horizontal synchronization signal section, color burst section, and video signal section.

The respective outputs of the suppression start timing generation circuits 26A to 26C are input to suppression pulse width determination circuits 27A to 27C. When the suppression pulse width determining circuits 27A to 27G receive a timing signal input, they thereafter output a pulse with a specific time width. For example, if the pulse width determining circuit 27B is compatible with color burst suppression, a pulse with a time width of about 5 μsec that can mask the color burst section is output immediately after the pulse input. That is, the suppression pulse width determining circuits 27A to 27G output pulses corresponding to the suppression time. Since the binary number sequence (000)-(111) is output at random from the initial setting, the presence or absence of pulses output from the suppression pulse width determining circuits 27A to 27C is made at random.

Finally, in the addition circuit 30, the suppression pulse width determination circuit 27A
The sum of the three outputs of ~27C is taken and a final gain control signal is created by a waveform shaping circuit (not shown).

The signals in the circuit shown in FIG. 3 are as shown in the waveform diagrams shown in FIGS. 4 and 5. For example, the binary number string data (1°0.1) as shown in FIG. 4(a) is sent from the binary number conversion circuit 23 to the superimposition control data creation circuit 25 as shown in FIG. 4(b).
It is output after the fall of the timing pulse, and the circuit 25 performs time adjustment and outputs superimposition data as shown in FIG. 4(C) after a time interval T from the V timing pulse. This superimposition data is superimposed by the data superimposition circuit 4 of FIG. 1 in a certain horizontal cycle period during the vertical retrace period of the composite video signal, as shown in FIG. 4(d).

On the other hand, a signal of 1.0.1 is input to each circuit as shown in FIG. 5(a) to the suppression start timing generation circuits 26A to 26C.
Then, a pulse as shown in FIG. 5(C) is outputted at a timing that is a certain time interval Te1lli from the 1'' timing pulse in FIG. 5(b). However, the output of 26B
(dashed line) is not present in this example. Then, by these timing pulses, the suppression pulse width determining circuits 27A to 2
7C outputs a pulse with a specific time width as shown in FIG. 5(d). However, the output of 27B (broken line) is not present in this example. The multi-pulse outputs of the circuits 27A to 27G are added by an adder circuit 30 and output as a gain control signal as shown in FIG. 5(e).

Regarding the creation of control signals on the decoder side: It is almost the same as on the L encoder side. The scrambled data signal superimposed on the vertical retrace period can be extracted by a slice circuit that can operate only during the time when the data is on. If you replace the extracted 3-bit binary string data with 0.1 data for each digit, then the same suppression start timing generation circuit, suppression pulse width determination circuit, addition circuit, and waveform shaping circuit as on the encoder side will be used. By preparing a signal and controlling its gain so that it works as an expansion instead of a suppression, the signal can be descrambled.

FIG. 6 is a circuit diagram showing an example of the gain control circuit 6, in which an RF television signal is input to the base of the transistor Q1, and the collector of the transistor Q1 is connected to the resistor R3.
The emitter of transistor Q1 is connected to the DC power supply VCC through resistor R1, the emitter of transistor Q1 is connected to the collector of transistor Q2 through resistor R2, and the emitter of transistor Q2 is connected to the collector of transistor Q2 through resistor R2. Connect to the ground point and apply 1 to the base of transistor Q2! ? Control signal 8 is input. Then, a gain-controlled RF television signal is output from the collector of the transistor Q1.

In the above circuit, the circuit of transistor Q1 is a common emitter circuit for transistor Q2, the resistance value of collector resistor R3 is r3 (Ω), the resistance value of emitter resistor R1 is ``1 (Ω), and resistance 1< Assuming that the resistance value of the transistor Q2 is rl (Ω) across from the resistor R1, when there is no gain control signal input, the transistor Q2 becomes non-conductive, one end of the resistor R2 is open, and the gain G of the amplifier is equal to the resistor R1.゜] Determined by the resistance ratio of <3, G-r3/r
It is 1.

In addition, when there is a gain aill tll signal, the transistor Q2 becomes conductive, one end of the resistor R2 is grounded, and the gain G' of the amplifier is determined by the resistance ratio of the parallel resistors R1 and r(2) and the resistor R3. It is determined by G'-r3 /
(rl //r1) =r3/(rl
/·λ ) ;2 (r3 /r1 )=2G, and the gain is twice that of the case without the control signal. With this, a switching circuit with a gain of 6 dB can be constructed. The range of gain change can be arbitrarily determined by changing the value of the resistor R3.

FIGS. 7 and 8 are explanatory diagrams for explaining other embodiments of the present invention. In this figure, only the lower portion of the RF television signal is shown. In this embodiment, as in the example of FIG. 2, the RF-modulated television signal is
Instead of controlling the gain with a different gain in C, the DC level is shifted independently in each section A-C, and the result is almost the same as in Table 1 for images received by DC level shifting. can give the effect of That is, the RF preview signal as shown in FIG. 7 is divided into horizontal synchronization signal section A1 color burst section B1 video signal section mc as shown in FIG.
Shift the DC level independently for each C. As a result, the same effect against prying eyes as in the case of FIG. 2 can be obtained.

In the above embodiment, the horizontal four-stage Shinkyu Ward A, the Color Burst Ward Question 8. Although the case where gain control of different gains is performed and the case where a different DC level shift is applied to at least three sections of the video signal section C will be described, the present invention is not limited to the above embodiment. -C with different level attenuation (Fig. 10) and AM modulation (1st
2) may be used for scrambling. That is, video scrambling may be performed using a scrambling method (gain control, DC level shift, level attenuation, AM modulation) specific to each section A-C.

[Effects of the Invention] As described above, according to the present invention, with a simple circuit configuration,
The amount of information transmitted for scrambling is small, and scrambling with a large degree of disturbance against unauthorized reception can be performed, and signal deterioration due to scrambling is reduced, and the quality of the descrambled signal is also good.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an encoder and decoder in which the video scrambling method of the present invention is used, and FIG. 2 is a 11F diagram explaining the video scrambling method of the present invention.
A waveform diagram showing an example of a television signal; FIG. 3 is a block diagram showing an example of the scramble control circuit of FIG. 1;
4 and 5 are waveform diagrams explaining the circuit operation of FIG. 3, FIG. 6 is a block diagram showing an embodiment of the gain control circuit of FIG. 1, and FIGS. 9 is a waveform diagram of a normal RF television signal, and FIG. 10 is a waveform diagram of an RF television signal illustrating a conventional video scrambling method. 11 and 12 are waveform diagrams of a sine wave signal and an RF television signal to explain other conventional examples of the video scrambling system. 1... Encoder, 2.12... Synchronization separation circuit, 3.14... Scramble control circuit, 4... Data superimposition circuit, 5... RF modulator, 6.15... Gain control Circuit, 10... Decoder, 11... Detector, 13...
・Data detection circuit. Agent: Patent Attorney Noriyoshi Chika Hiroshi Uji Figure 5Q

Claims (1)

[Claims] When scrambling a television signal obtained by amplitude modulating a carrier high frequency wave with a composite color video signal, at least three of a horizontal synchronizing signal section, a color burst section, and a video signal section of the television signal are provided. A video scrambling method characterized by performing video scrambling for two sections using a scrambling method unique to each section.