JPS5824285A - Chargeable television system - Google Patents

Abstract

PURPOSE:To obtain received pictures of high quality with simple constitution by modulating a TV signal, coding and transmitting the modulated signal with control codes from a random code generating circuit, and then applying the signal restored on a reception side to the input terminal of a TV receiver. CONSTITUTION:On a transmission side, a TV signal is modulated at a part 1 and sent to a high frequency video synchronizing signal processing circuit 2, and the signal is coded with control codes from a random code generating circuit 5 and transmitted from an antenna 4 through an exciter 3. On a reception side, on the other hand, the received high frequency TV signal is frequency-converted at a part 6 and detected at a part 8 to be sent to a random code generating circuit 19 through a V trigger generating circuit 10. This circuit 19 supplies N-bit random codes to a video synchronizing regenerated signal synthesizing circuit 21 in every vertical or horizontal blanking period, and the circuit 21 outputs a video synchronizing regenerated signal to a high frequency video synchronous processing circuit 22. The circuit 22 restores a high frequency coded TV signal from the circuit 8 and supplies the restored signal to the input terminal I of a TV receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to pay television systems, and in particular to improvements in their encryption systems.

There are two main types of encryption methods used in conventional pay television systems: one is to suppress the synchronization signal component to obtain an encrypted television signal, and the other is to invert the video signal component to encrypt it. Separated.

The former method has advantages such as a simple circuit, low cost, and good image quality because the processing is usually performed using high frequencies; however, it has low security against eavesdropping, which is fatal to the pay television system. There are certain shortcomings.

On the other hand, the latter method is more secure against eavesdropping than the former method, but the circuit is more complicated, the decoder is more expensive, the electrical characteristics of the TV signal deteriorate, data buzz occurs, etc. There are drawbacks.

The present invention has been made in order to improve the drawbacks of such conventional systems. 1. By moving the black level of the video signal component of an ordinary television signal beyond the pedestal level to the sync signal side, an encrypted television signal can be generated. The purpose of the present invention is to provide a new pay television system that is simple in construction, has good safety and picture quality, and is easy to configure.

In the present invention, after a normal television signal is modulated by the encoder on the transmitting side, level suppression processing is performed on both the synchronization signal component and the video signal component, and the black level of the video signal component is adjusted to the pedestal level as described above. 1 to the synchronizing signal component side, and generates and transmits a high frequency encrypted television signal such as 81 in FIG. 3, for example. This switching of the suppression level is performed in response to a control code output from a random code generation circuit whose initial state is set in the encoder. At this time, the AG on the receiving side
In order to operate the C circuit, a normal horizontal synchronization signal without encryption processing is transmitted every three to four horizontal synchronization signals.

Even if this high-frequency encrypted television signal is received by a normal television receiver, a signal like 84 in FIG. 3 will be detected, and the synchronization will be disrupted, making it impossible to view the signal.

The receiving side decoder responds to the same control code as the sending side, which is output from the random code generation circuit in synchronization with the sending side encoder, by giving the video synchronized reproduction signal 82 in Fig. 3 to the high frequency video processing circuit. It is restored to a normal high frequency television signal (83 in FIG. 3) and supplied to the television receiver.

In this case, the subscriber is notified in advance so that the status setting code of the random code generation circuit matches the encoder and decoder.

The present invention will be described below with reference to embodiments shown in the drawings.
In the transmitting side apparatus shown in FIG. 1, 1 is a modulator, 2 is a high frequency video synchronization signal processing circuit (encoder), 3 is an exciter, 14 is an antenna, and 5 is a random code generation circuit.

A modulator 1 modulates a normal television signal, and supplies the modulated television signal to a high-frequency video synchronization signal processing circuit 2, which performs the aforementioned encryption in response to the control code from a random code generation circuit 5. The processing is performed to create an encrypted television signal such as 81 in FIG. 3, which is transmitted from the antenna 4 via the exciter 3.

Note that the audio signal in the present invention ranges from 0 to 0 as shown in FIG.
15KH2 audio signal component, 9 pilot signal component and 3fH or 4fH as reference, ±15 on both sides thereof.
) G-12 carrier sub-audio signal component.

Figure 4 shows the decoder on the receiving side, 6 is a tuner, 7 is a high frequency amplification circuit, 8 is a video detection circuit, 9 is an AGC circuit,
10 is a v trigger generation circuit, 11 is an audio detection circuit, 12 is an audio processing circuit, 13 is a low frequency amplifier, 14 is a speaker,
15 is a PLL circuit, 16 is a horizontal retrace period pulse generation circuit, 17 is a synchronization pulse generation circuit, 18 is a Hiteo pulse generation circuit, 19 is a Langmuco-1 generation circuit, additional is a state setting switch, 21 is a video synchronized reproduction signal synthesis circuit, n is a high frequency video synchronization signal processing circuit.

In the decoder shown in FIG. 4, when one high frequency encrypted television signal S1 transmitted from a broadcasting station is received, the tuner 6
added to. The tuner 6 converts the received frequency to lower it to a required frequency, and provides the frequency conversion output to the high frequency amplifier circuit 7.

The encrypted television signal amplified by the circuit is sent to the video detection circuit 8.
A part of the detected output is applied to the AGC circuit 9, which extracts only the regular horizontal synchronizing signals sent every 3 to 4 from the transmitting side and applies AGC to the tuner 6.

Further, the detection output of the video detection circuit 8 is given to the V) IJ trigger generation circuit 10 and the audio detection circuit 11, and the V trigger generation circuit 10 applies the timing output of the vertical trigger pulse to the random code generation circuit 4 and the audio detection circuit 11. provides the audio detection output to the audio processing circuit 12, and the output processed by the circuit is amplified by the low frequency amplifier 13 and drives the speaker 14. At this time, a pilot signal is extracted from the voice-detected synthesized audio signal and the PLL circuit 1
5, the phase is locked in this circuit, and its output is added to the audio processing circuit 12 to process the audio detection output.

Now, since the video signal is encrypted as mentioned above,
Since a normal screen will not be reproduced unless it is restored to a normal high-frequency television signal, the pilot signal used in the audio signal processing is reused as follows.

That is, the output signals of p r, r, and circuit 15 are given to the horizontal retrace period pulse generation circuit 16, the synchronization pulse generation circuit 17, and the video pulse generation circuit 18 for processing, and the output signals from the respective circuits are sent to the video synchronization reproduction signal synthesis circuit. 21, provide the horizontal retrace pulse, synchronization pulse, and video pulse. At the same time, the synchronization pulse is also given to the random code generation circuit 19.

The random code generation circuit 19 is set to an initial state by a state setting switch, and supplies an N-bit random code to the video synchronized reproduction signal synthesis circuit 21 in units of vertical or horizontal retrace lines. In response to this random code, the circuit 21 outputs a video synchronization reproduction signal such as 82 in FIG. 3, and supplies it to the high frequency video synchronization signal processing circuit n. The circuit n
The high-frequency encrypted television signal as shown in 81 in FIG. 3, which is given from the video detection circuit 8, is restored as shown in 83 in the same figure and is supplied to the input terminal I of the television receiver.

FIG. 5 shows an example of the configuration of the video synchronized reproduction signal synthesis circuit 21. As shown in FIG. In the figure, 23 to 26 are control code application terminals supplied from the random code generation circuit 19, 27 is a video pulse application terminal, 2 is a horizontal retrace pulse application terminal, 29 is a synchronization pulse application terminal, is a 2 line = 4 line decoder, 32 to 36 are AND gates, 37 is an integration circuit, 3 is a differentiation circuit, 39 to 43 are transmission gate circuits,
44 is a negative direction clamp circuit, 45 is a positive direction clamp circuit, and 46 is a video synchronized reproduction signal output terminal.

FIG. 6 shows an example of the configuration of the random code generation circuit 19. In the figure, d1 to dn are D type 7 lip-flop circuits, S is a set terminal, CL is a clock terminal, and D1
~DN is a random control code output terminal, Sw1~5Wr
L-2 is each switch constituting the state setting switch, and OR is an OR circuit.

The logic circuits d1-drL constitute a pseudo-random number generation circuit, and by switching the switches SW1-5w1-2, the random number generation pattern can be changed and the code can be switched.

Set terminal SVC is the vertical trigger pulse or N1
A synchronizing pulse or a synchronous pulse counted N2 times is added to the clock terminal CL, and the output terminal D
An N-bit control code from 1 to DN can be obtained for each horizontal or vertical blanking line.

The control code obtained as described above is supplied to terminals L-A of the video synchronized reproduction signal synthesis circuit 21 in FIG. is given to one input of The video pulse given to terminal n is applied to AND gates 32-3.
The other input of circuit 37. The open outputs are applied to transmission gate circuits 40 and 41, respectively. The transmission gate circuits 39 to 41 are controlled by the outputs of AND gates 32 to 34, respectively, and the outputs of the husband's transmission gate circuits are combined and added to the negative direction clamp circuit 44, and the maximum value of the output is clamped. be done.

On the other hand, the horizontal retrace pulse and synchronization pulse applied to terminals A and 4 are controlled by the other input of AND gate 35.36 and the output of the AND gate (42.4).
3, and the outputs of each transmission gate are combined and applied to a positive direction clamp circuit 45, where the minimum value of the output is clamped.

The signals clamped by the negative direction clamp circuit 44 and the positive direction clamp circuit 45 are combined, and a video synchronized reproduction signal is obtained at a terminal 46.

FIG. 7 (al is an example of the transmission gate circuits 39 to 43, and Trl and Tr2 are transistors.
and (cl are circuit examples of the clamp circuits 44 and 45, respectively, Tr3 and Tr4 are transistors, and Dl and D2 are clamp diodes.

Figure 8 is an example of the high frequency video synchronization signal processing circuit B.
FBT is a field effect transistor.

When applying the high frequency encrypted television signal S1 to terminal 47 and the video synchronized playback signal S2 to terminal 48, the gate power of the FET is clamped to the same level as the video synchronized playback signal, so the level of the video synchronized playback signal can be adjusted appropriately. By doing so, a normal high frequency television signal S3 can be obtained from the source side terminal 41C of the FET.

FIG. 9 shows a detailed configuration example of the transmitting side system of the present invention shown in FIG. In the figure, a timing circuit 53 generates timing signals for a horizontal synchronization signal and a vertical synchronization signal from the normal television signal S'1 of FIG. 10 obtained from a video signal source 51. This timing is applied to a random code generation circuit 55, and a code is randomly generated at the timing of the horizontal synchronization signal. Random code generation circuit 55
The initial state is set by the state setting switch 56. The control code and the timing are applied between an encrypted signal generating circuit to generate an encrypted signal S'l. The encrypted signal generation circuit is similar to the video synchronization signal reproduction signal synthesis circuit on the decoder side described above, and obtains the encrypted signal S3 by inverting the level of the video synchronization signal reproduction signal with respect to the clamp level. This process is similar to that of the video synchronization reacquisition signal synthesis circuit shown in FIG. 5 described above. On the other hand, the television signal obtained from the video signal source 51 is transmitted to the video signal modulator 52. The modulated television signal S2 obtained in addition to the encoded signal generating circuit 5
The encrypted signal obtained from step 4 is sent to a high frequency video synchronization signal processing circuit. The high frequency video synchronization signal processing circuit 57 is the same as the high frequency video synchronization signal processing circuit of the decoder described above.

Also, the audio signal is generated from between the pilot signal generation circuits by the timing signal obtained from the timing generation circuit 53.
5. Obtain the pilot signal of 734KH2.

The audio signal source 59 is an audio signal to be encrypted, which is applied to the modulation circuit ω and modulated with a 3fH or 4fH carrier. The audio signal source 61 is an unencrypted audio signal. The pilot signal, the encrypted signal, and the audio signal are applied to the audio modulation circuit 62 and modulated at a high frequency.

The frequency spectrum of the audio signal in the baseband is as shown in FIG. The encrypted high-frequency signal obtained from the high-frequency video synchronization signal processing circuit group and the audio high-frequency signal obtained from the audio modulator 62 are frequency-converted and amplified by an exciter 63, and then radiated through an antenna 64.
1. As mentioned above, in the cryptographic processing method of the present invention, the black level of the video signal component of a normal television signal is moved beyond the best signal level to the synchronization signal side, but in this case, the level shift is performed using a triangular wave or a rectangular wave. It can be done to form waves, curves, etc.

Of course, the size and shape of the level can be switched randomly.

As is clear from the above explanation, the present invention can exhibit excellent effects as described below.

(]) Since encrypted television signals are processed at high frequencies, there is little deterioration in image quality, and the device configuration is simple and inexpensive.

(2) Since the level of the synchronization signal is switched randomly, it has high scrambling properties.

(3) High safety is achieved because the levels of video signal components are randomly transformed and switched. Even if the synchronization signal were to be restored with the intention of eavesdropping, it would be difficult to know the contents.

(4) Unlike conventional methods, no code is superimposed on the encrypted television signal, so no data bus or the like is generated. Furthermore, even if you intend to steal a video, it will not give any clues to deciphering it.

[Brief explanation of the drawing]

1 and 4 are block diagrams showing the configurations of the transmitting and receiving systems according to an embodiment of the present invention, FIG. 2 is a diagram showing the frequency spectrum of an audio signal, and FIG.
Similarly, FIG. 7(a) is a block diagram showing an example of the configuration of a random code generation circuit. (1)) and (C1 respectively represent the transmission gate circuit, negative direction clamp circuit and positive direction clamp circuit in FIG. 2)
...High frequency video synchronization signal processing, 5...Random code generation circuit, 6...Tuner, 19...Random code generation circuit, addition...Status setting switch, 21...
Video synchronous reproduction signal synthesis circuit, n...high frequency video synchronous signal processing circuit. Patent Applicant Clarion Co., Ltd. Agent Patent Attorney Nagai 1) Takesanbe' Figure 7 (0) (b) (C) Figure 8 Figure 9

Claims (1)

[Claims] m After modulating a normal television signal, the synchronization signal component and video signal component of the modulated television signal. High-frequency encryption is performed by performing level suppression processing in response to a control code output from a random code generation circuit whose initial state can be set, and moving the black level of the video signal component beyond the pedestal level to the synchronization signal side. A pay television system characterized by obtaining a converted television signal and transmitting it to the receiving side. (2) The pay television system according to claim (4), wherein the level movement is arranged in the form of a triangular wave, a rectangular wave, a curved line, or the like. (3) A random code generation circuit is provided on the receiving side to generate a control code independently and synchronously with the transmitting side, and the high frequency encrypted television signal is restored to a normal television signal by the control code. Claim No. (11) Paid telepicture system.