JPS6195687A - Scramble system of television signal - Google Patents

Abstract

PURPOSE:To prevent unfair eaves dropping by having a variable phase for an index signal showing a compressing position of the compressed TV video signal to a horizontal synchronizing signal in the video signal and AM- modulating a sound signal with these signals. CONSTITUTION:A TV video signal of an input terminal 1 is on one hand inputted to a synchronizing separating circuit 2 and on the other hand inputted to a video signal modulating circuit 3 and a video IF from a carrier generating circuit 4 is AM-modulated as a carrier. At a synchronizing separating circuit 2, respective horizontal and vertical synchronizing signals are separated from a video signal, the respective synchronizing signals are obtained and a switching signal generating circuit 5 generates the first switching signal in correspondence to a horizontal blanking period and the second switching signal in correspondence to the vertical blanking period. An amplitude suppressing circuit 6 suppresses amplitude during the blanking period of an output signal of the modulating circuit 3 and send to a frequency converting circuit 7. A TV sound signal is FM-modulated by a sound IF carrier at a sound signal modulating circuit 9 and inputted to a control signal modulating circuit 10. At the circuit 10, the sound signal after FM modulation is AM-modulated.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a TV signal scrambling system used in pay television broadcasting systems such as ATV.

Conventional technology Various scrambling methods for I'V (television) signals have been proposed in the past, and one of them is, for example,
8-51678 has something to show. That is, the method of this publication compresses the horizontal blanking period including the horizontal synchronization signal of the TV video signal after AM modulation to a level sufficiently lower than that of the video signal part, and also The TV audio signal after FM modulation is subjected to AM modulation using a pulse signal (referred to as an index signal) at a time position, and the TV audio signal after AM modulation and the previously compressed TV video signal are transmitted to the receiving side. ing.

Therefore, according to this method, the receiving side performs AM detection on the TV audio signal that has not been transmitted from the transmitting side, and extracts the index signal of the song description, and uses this index signal as a time reference for each horizontal blanking period. The original TV video signal can be restored by creating a corresponding switching signal, receiving the switching signal, and switching the amplification gain for the compressed TV video signal.

(C) Problems to be Solved by the Invention However, in the conventional method described above, the index signal always has a constant phase relationship with the horizontal synchronization signal, so the advantage is that the configuration of the descrambling device on the receiving side is simple. On the other hand, third parties other than regular subscribers (subscribers)
There is a drawback that the descrambling method can be easily decoded and viewed by someone else.

Therefore, in view of this, the present invention provides a T.
We are trying to propose a V-fold signal scrambling method.

B) Means for Solving the Problems In the present invention, the index signal indicating the compression position of the compressed TV video signal as described above has a variable phase with respect to the horizontal synchronization signal in the video signal. , representing this index signal and the above-mentioned phase (No. 1 performs AM modulation on the TV audio signal, and transmits this AM-modulated sound P and the above-mentioned compressed video signal to the receiving side.

(E) Effect According to the above configuration, by appropriately changing the phase of the index signal with respect to the horizontal synchronization signal and transmitting it, it becomes difficult for non-subscribers to decipher the descrambling method, and
By transmitting a signal representing the above-mentioned phase, descrambling on the subscriber side can be easily realized.

(F) Embodiment FIG. 1 shows a schematic configuration of a scrambling device on the transmitting side to which the present invention is applied. In the same figure, (11 is an input terminal into which a baseband TV video signal is introduced, the TV video signal introduced here is inputted to the synchronization separation circuit (21) on the one hand, and the video signal is modulated on the other hand. Circuit (3)
The signal is input to the carrier wave generating circuit (4) and subjected to AM modulation using the video signal F (intermediate frequency a) as a carrier wave.

The synchronization separation circuit (2) separates the horizontal and vertical synchronization signals from the video signal, obtains these synchronization signals, and generates a switching signal generating circuit (51 includes at least the horizontal synchronization signal h within the horizontal blanking period). A first switching signal corresponding to a short period (hereinafter referred to simply as "horizontal blanking period" 85) and a second switching signal corresponding to a vertical blanking period are created. The signal is obtained, and the amplitude of the output signal (FIG. 2 (a)) of the video signal modulation circuit (3) is compressed during each blanking period. Therefore, the output signal of the amplitude suppression circuit (6) becomes as shown in Figure 2 (b), and this signal (b) is sent to the frequency conversion circuit (7). It will be done.

- 10,000, (8) baseband TV audio signal is introduced n
The audio signal introduced here is FM-modulated by the audio IF carrier from the carrier wave generation circuit (4) in the audio signal modulation circuit (9), and then input to the control signal generation circuit. Ru. This circuit (in 11, the index signal and flag signal obtained from the control signal generation circuit
), and in its 's1 mode (standard mode), the trailing edge coincides with the leading edge of each horizontal synchronizing signal (5) outside the vertical plan young period, as shown in No. 31 as an index signal, and the next pulse (1) Create wo. Moreover, in this first mode, the control signal generation circuit l111 does not generate a flag signal, which will be described later, so the modulation input to the control signal modulation circuit αG is as shown in FIG. Therefore, in this case, the output signal of the keying circuit a1 is as shown in Fig. 2 (c).
In the mode, the index signal from the control signal generation circuit a11 is D=18μsea・delay tN from the index signal (FIG. 5(a)) in the standard (first) mode.
9 pulses, and a flag signal as data indicating this mode is generated in the period of the 24th line in each field of the video signal as shown in FIG. Therefore, in the case of this fourth mode, the mixed output of the index signal (1) and the flag signal CFI from the control signal generation circuit all is as shown in FIG. 11, the output signal of this modulation circuit aα is as shown in FIG.

In addition, in each mode other than the above, the control signal generation circuit αB similarly generates the index signal in the standard mode (FIG. 5 (at)) by the predetermined time shown in FIG. 4 (delayed by DI). index signal (1),
A flag signal flight 1 that appears in a predetermined line period shown in FIG. 4 is created. Moreover, the above-mentioned first to ninth modes can be switched completely freely, for example, for each channel by controlling a combiator or the like.

It is configured to be performed completely randomly for each program and each day of the week.

Then, the modulated audio signal outputted from the control signal generation circuit as described above (see FIG. (0) in the figure is converted to the carrier frequency of its own channel in the frequency conversion circuit (71) and transmitted to the receiving side.

Next, FIG. 6 shows a schematic configuration of a descrambling device on the receiving side. In the figure, α'2 is an input terminal into which the TV signal of each channel transmitted from the transmitting side as described above is introduced, and the TV signal of each channel is input to channel α3. After being frequency-converted into a signal of a specific channel (for example, the first channel or the second channel), the signal is fed to the video signal extraction circuit α4 on one side, and inputted to the audio signal extraction circuit (151) on the other side.

Output signal of the audio signal extraction circuit α (Fig. 7 (b))
is input to the AM detection circuit, thereby decoupling the °C pulse train signal (number f in the same figure), and the pulse train signal t→ is input to the gate circuit a711c. A gate pulse (G=l in the figure) is obtained from the generating circuit, and only the index signal (11) in the pulse train signal e→ is passed, and the index signal is applied as one input of the phase detection circuit 9. Also, as the other input of this phase detection circuit α9, the above pulse generation circuit (fHc horizontal frequency from 181)
A pulse signal is given.

The output of this phase detection circuit α9 controls the 52 fH ■00 (voltage controlled oscillator) ■, and therefore the 52 fH
A PLL (phase locked loop) is configured together with the timing pulse generation circuit α&, which is configured by a combination of a counter that counts 2fH pulses, and the like. Further, Ca4l is a vertical detection circuit to which output No. 41 of the gate circuit surface is given, and a vertical blanking period VCilt index signal (I
The blanking period is detected by utilizing the fact that t does not exist, and the counter of the pulse generating circuit a81 is reset by the detection output. Incidentally, the index signal is detected by the detection circuit C4 by sampling with horizontal period pulses from the timing pulse generation circuit αg.

On the other hand, Ca1l is a flag signal detection circuit, which converts the output signal of the fIJ AM detection circuit (Fig. 7 (c)) into a signal with a small tolerance width (N in the figure) using a monostable motor, lkf vibrator, etc. , the presence or absence of a flag signal is detected by sampling this signal (to) at the rising edge υ timing of the pulse from the timing pulse generation circuit (18).The detection output is given to the decoder circuit for detection. The timing is compared with the reference timing obtained from the timing pulse generator α seconds to decode the horizontal line number in each field where the flag signal is present.Furthermore, this decoder decodes the line number by decoding the line number.
Detects which of the modes 1 to 9 in Figure 4 the currently received audio (No. 8 is being modified to AM v4),
A reset pulse (FIG. 7 (G)) having a timing (described later) corresponding to the detected mode f' is generated, and this pulse (G) is applied to the switching signal generation circuit 1231.

The switching signal generation circuit (23 is the reset pulse (23)
5 of the switching signal '2voo■ which becomes high level during the vertical blanking period and the horizontal blanking period, with the time point reset by (g) as the starting point of the vertical blanking period.
The switching signal is generated by obtaining a 2fH pulse, but at that time, the timing of the reset pulse H changes according to the above-mentioned 1st to 9th modes, so that the switching signal changes to In other words, when the mode detected as described above is, for example, the 4th mode, it is assumed that the signal (A) corresponds to the 1st-order reset pulse generated in the 1st (standard) mode. By applying a reset pulse whose timing is advanced by 18 .mu.se.alpha. to the switching signal generating circuit, the phase of switching No. 41 11JI coincides with the video signal (a) currently being received.

The above switching signal (S) is the output signal (S) of the video signal extraction circuit I (
A) is applied to the gain switching circuit to be introduced, and during the high level period of this signal (S), the amplification gain of the circuit 4 is switched to increase, and as a result, the video signal section and It is derived as a regular carrier video signal in which the relative gain difference with the horizontal and vertical image blanking periods has been eliminated.

Then, this video signal is mixed with a carrier audio signal (port 1) from the audio signal extraction circuit (1) and sent to the antenna terminal of the TV receiver ff1 (not shown).

Here, the above audio signal (mouth 1 is the index signal I11
and the flag signal (F') are AM-modified v4 and sent to the TV receiver, but since the TV audio l-jFM modulation has been carried out, both of the above signals (
11 (Fl can be removed and there is no problem at all.

In the above embodiment, the video signal was scrambled by amplitude compression on the modulated carrier video signal Vζ on the transmitting side, but the baseband video signal was scrambled in the same manner as ℃, and the scrambled video The signal may be modulated to obtain the carrier video signal. Further, although it is preferable to perform the amplitude compression during the horizontal and vertical image blanking periods as in the embodiment, it is also possible to perform the amplitude compression only during the horizontal blanking period.

(G) Effects of the Invention According to the scrambling method of the present invention, the time position t'ft of the index signal, which is the basis for descrambling the video signal, can be changed arbitrarily. It is possible to prevent illegal eavesdropping by making decoding difficult for five parties, and the descrambling device on the receiving side is not much different from conventional devices and can be realized at low cost with a simple configuration, and there is less risk of malfunction. There are many advantages.

[Brief explanation of the drawing]

Each of the drawings shows an embodiment of the present invention, and FIG. 1 is a block diagram showing a schematic configuration of the main parts of the scrambling device, FIGS. 2 and 3 are waveform diagrams showing signal waveforms of each part of the scrambler, 5 and 5 are explanatory diagrams and signal waveform diagrams for explaining the index signal sending mode, FIG. 6 is a block diagram showing the schematic configuration of the main parts of the descrambler, and FIG. 7 shows the signal waveforms of each part. There is a waveform diagram to show. (Eng. 1: Index signal, (Fl: flag individual number) Sanyo Electric Co., Ltd.

Claims (2)

[Claims] (1) The horizontal blanking period including the horizontal synchronization signal in the television video signal is compressed by a certain amount to a level sufficiently lower than the maximum modulation degree of the video signal part, and each horizontal synchronization signal after the compression is A television signal in which a television audio signal is AM-modulated using an index signal having a variable phase and a signal representing the phase, and the AM-modulated audio signal and the compressed video signal are transmitted to a receiving side. Scramble method. (2) The signal representing the phase is of a flag signal type corresponding to a predetermined position within one predetermined horizontal line of the television video signal, and the horizontal line position where this flag signal is inserted is set to the phase. 2. The television signal scrambling method according to claim 1, wherein the method is changed accordingly.