JPS60109390A - Scramble system of television signal - Google Patents

Abstract

PURPOSE:To obtain the higher scramble effect and to obtain higher secrecy by level-shifting the horzontal blanking period in the whole period of a signal, and by inverting an optional image part by the prescribed folding back level. CONSTITUTION:A signal S0 which is supplied from a video signal source 1 is added to an HBLK shift circuit 3 through an amplifier 2, and is also added to a synchronizing separator circuit 4. As a result, horizontal and vertical synchronizing signals are separated. A timing circuit 5 controls the operational timing of the circuit 3 based on the signal from the circuit 4, and the level shift of the horizontal blanking period is executed over the whole period of the signal S0. A level-shifted signal S1 is added to an inversion/noninversion circuit 6, and the volantary horizontal blanking period and/or the volantary image part are/is inverted by a 50IRE intermediate luminance level.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a television signal scrambling method useful for contract television broadcasting.

Background technology and its problems Recently, contract television broadcasting has become popular in the United States and other countries.

In contract television broadcasting, only viewers who have signed a reception contract with the broadcasting station can receive normal reception, and those who do not have a contract are not able to receive normal reception. In order to prevent non-contractors from receiving normal reception, the sending side has traditionally manipulated video and audio signals so that when received by a normal TV receiver, they are not correct. Methods are used to prevent images and sounds from being obtained. This method is called scrambled broadcasting. In contract television broadcasting using this type of scramble system, viewers who have subscribed to the reception are
A descrambling device is required to restore (descramble) the scrambled signal to its original form.

In scrambled broadcasting, it is necessary to increase the scrambling effect of the television signal. In other words, when a scrambled television signal is received as is by a receiver, the images and sounds are confused as much as possible.
It is necessary to keep the contents as hidden as possible. At the same time, it is necessary to make the scrambled television signal highly confidential so that it cannot be easily decoded on the receiving side. That is, since the television signal is scrambled according to a predetermined scrambling method, it is necessary to prevent the receiving side from easily decoding the scrambling method and thereby preventing unauthorized reception.

Conventionally, as an example of a scrambling method for scrambling a video signal, a method has been proposed in which the white level side and the black level side of the video signal are inverted at a predetermined aliasing level.

When this scrambling method is used in an actual broadcasting system, a scramble pattern is formed by combining a field period in which the level is inverted and a field period in which the level is not inverted, and this scramble pattern is repeatedly transmitted. . At the same time, a key code signal for decoding the scramble pattern on the receiving side is inserted at a predetermined position in the vertical brushing period.

To receive the scrambled television signal scrambled as described above, the level-inverted field period is detected based on the key code signal, and the video signal of that field period is re-inverted to its original form. Descrambling is performed to restore the data.

However, this scrambling method has the disadvantage that if the scrambled signal is affected by distortion in the transmission system, the original waveform cannot be restored correctly when descrambling is performed on the receiving side. For example, when a signal whose level has been inverted is re-inverted, a level difference occurs from the original waveform, or the waveform becomes distorted. When a signal with such a waveform is applied to a receiver, flickering occurs on the screen at the inverted portion. This flicker is particularly noticeable when the screen is close to a still image.

Furthermore, when a scrambled broadcast program is recorded on a VTR, flicker is particularly likely to occur because the VTR has nonlinearity in both direct current and alternating current.

In order to reduce this flicker, increasing the cycle of level inversion weakens the scrambling effect. Furthermore, it is necessary to transmit a reference level signal in order to match the return levels for level inversion on both the transmitting and receiving sides. Furthermore, the key code signal is likely to be illegally decoded on the receiving side and the scramble pattern may be restored.

Another example of a conventionally proposed scrambling method is a method in which the horizontal synchronization signal portion is shifted to the level of the video signal portion to disturb the horizontal synchronization of the screen.

However, with this method, if the average luminance level of the video signal is high, even if the horizontal synchronization signal is shifted, the video portion may become higher than the sync chip and synchronization may be achieved. At this time, the screen becomes dark, but you can still see the normal screen. In addition, it is easy to restore the horizontal synchronization signal only by shifting it, and it is easy to receive it incorrectly.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and proposes a novel scrambling method that can increase the scrambling effect and improve confidentiality.

SUMMARY OF THE INVENTION The present invention levels-shifts the horizontal blanking period in the entire period of a television signal.

This can result in a scrambling effect that causes the screen to be out of synchronization and color errors.

Further, according to the present invention, the level of the horizontal blanking period is shifted, and any horizontal blanking period and/or any video portion is inverted at a predetermined folding level. This makes it completely impossible to separate the synchronization signals in the usual way on the receiving side, and
Color demodulation becomes even more difficult.

Further, in the present invention, since the offset level for performing the level shift is set to the 5 Q I BE intermediate luminance level, there is no need to send a signal indicating a reference level for performing descrambling.

Embodiments FIGS. 1A and 1E show various embodiments of the scrambling method according to the present invention.

Figure A is a normal video signal So before being scrambled.
, and the video signal is A field, V, B
It consists of LK (vertical blanking period) and B field parts. There is a video portion Sv in the 1H period in the A field and B field period, and this IH
In the period H and 13LK (horizontal blanking period), there is a horizontal synchronization signal HP and a color burst signal CB. Even if the above video part tl:0IRE to 'IQ01R,B exists in the level range, the above V, BLK has the above signal H.
In addition to P and CB, there are an equalizer pulse EQ and a vertical synchronization signal vP (not shown).

FIG. 1B shows a scrambled video signal S1 obtained by scrambling the video signal So described above using a first method.

In this first method, the levels of the H and BLK portions are level-shifted using level 5 [IIRE of the video portion as an offset level. In the figure, the original signals HP and CB shown by dotted lines are lifted by 5 Q I Rli; to become signals HP5 and CB.

In this case, the video portion 8V is left as is. Also V, B
Also in the LK portion, all of the signals HP, CB, EQ and VP are level shifted and the output is T4J), , CBS.

EQ, VP5. In this way, the level shift in the H period is performed over the entire period of the signal So.

According to this first scrambling method, the following effects can be obtained.

(1), since the minimum level E1 of the 81 part SV is lower than the synchronized rough level E2, the HPlC
Synchronous signals such as B, EQ, V)' cannot be separated in the usual way. Therefore, the scrambling effect is
The screen becomes out of sync and color errors occur.

(2) Since the offset level is set to 50IRE, there is no need to send a signal indicating the reference level for descrambling to restore I(l)5, CB, EQ, VPs to their original values.

FIG. 1C shows a scrambled video signal S2 scrambled using the second method.

In this second method, the signal event 8 and CB5 level-shifted by the first method are further converted to 50 I R.
The level is inverted using E as the inversion level, and the signal HPss C
B3t! Knee L/It is. This reversal is H,BLK
The ratio BLK, which performs inversion, and H, BLK, which does not perform inversion, are arbitrarily selected. Further, no inversion is performed in the V and BLK portions.

By this second method, the following effects can be obtained in addition to the effects obtained by the method of (f, t41).

(1) In the case of the first method above, if the average level of the video (i4 part SV) is high, the above level E1 may be higher than B2, and Shingetsu 1 - IPs% CBS is possible. However, in this method, Il, P, and CB are level-shifted and inverted, so it is completely impossible to separate them using a normal method.

(2), since the color burst signal CB5 is also inverted, the color i9? A becomes even more difficult.

(3) Since the inversion level is set to 5QII (,E), there is no need to send a reference level for descrambling which inverts the signals HP3 and CB again and returns them to their original state.

(4) Since level inversion is performed completely randomly in units of H and BLK, it is difficult to decode on the receiving side, and secrecy can be enhanced.

FIG. 1] shows a scrambled video signal S3 scrambled using the sixth method.

In this second method, the signal S1 according to the first method is
The level of the video portion SV of is inverted using 5 Q i RE as the inversion level, and the video portion is 8V. This inversion is performed field by field, and fields to be inverted and fields not to be inverted are arbitrarily selected. In the illustrated case, the A field is inverted and the B field is not inverted. Further, the V and BLK portions are not inverted.

Inverting the video portion S■ is a method that has been proposed in the past, as described above. Therefore, according to the sixth method, in addition to the effect of the first method, it is possible to obtain a scramble effect in which a negative image is displayed on the screen.

FIG. 1E shows a scrambled video signal S4 scrambled by the fourth method.

This fourth method uses all of the first, second, and third methods described above, and can obtain all the effects described above for each method.

FIG. 2 shows an embodiment of a transmitting circuit for implementing the fourth method.

In the figure, a video signal So shown in FIG. 1A supplied from a video signal source (1) is passed through an amplifier (2) to
LK Applied to the shift circuit (3) and also added to the synchronization separation circuit (4) to generate horizontal and vertical synchronization signals HP1VP
are separated. The timing circuit (5) receives the signal HI
The operation timing of the ratio BLK shift circuit (3) is controlled based on D and VP. In response to this control, the H, BLK shift circuit (3) performs a level shift of the ratio BLK portion over the entire period of the signal So by the first method. The level-shifted signal S, as shown in FIG. 1B, is
In addition to the inverting/non-inverting circuit (6) controlled by the timing circuit (5), here the second method and the sixth method described above are used.
Scrambling is performed using the following method. As a result, a scrambled video signal S4 shown in FIG. 1E is obtained.

On the other hand, the controller (7) includes a random pattern generation circuit that periodically generates a random pattern signal that is a random combination of inversion and non-inversion, and based on this random pattern signal, the timing circuit (5) and the data register (8) is controlled. According to this control, the data register (8) forms a key code signal indicating a scrambling pattern and other various code signals mentioned above. These code signals are sent to the adder (9) during a predetermined H period (
For example, it is inserted in the 15th H period). The signal S4 into which the code signal has been inserted is then modulated by a modulation circuit aO) and sent out as a scrambled television signal Ssc.

FIG. 6 shows an embodiment of a descramble apparatus for restoring the original video signal So by damaging the descrambled television signal "sc".

In Fig. 5, the above signal S selected by tuner 0υ
sc is converted into an intermediate frequency signal by an intermediate frequency circuit (121), and then detected by a detection circuit (131) to obtain a scrambled video signal S4. 05) are added to the gate circuit Q61αη and data sampling circuit side, respectively.

The data extraction circuit (19) extracts data indicating the scramble pattern from the code signal, and based on this data the controller (19) controls the timing circuit (19). (21), Vertical synchronization separation circuit (22)
Accordingly, regular horizontal and vertical synchronizing signals HP and Vl' are separated by a method described later. These signals HP%V
The timing circuit (a)) is synchronized by P. The timing circuit υ) drives the gate circuit Q61071, the data extraction circuit (1g, the AGC circuit 051, etc.) at a predetermined timing, and controls the inverting operation and non-inverting operation of the inverting/non-inverting circuit. .This circuit a inverts the video portion SV and signal (Ps) of the signal S4, and passes the video portion SV and signal (Ps) as is.The output signal of this circuit is then sent to the synchronization signal restoration circuit (23 ) in addition to the signal f(Ps, CBS) under the control of the timing circuit QJ.

VF6, EQ, 4= are returned to their original levels and become the first regular signals HP, CB, VP% EQ, respectively. With the above steps, descrambling is completed and the original video is restored.
Kokichi can get it.

FIG. 4 shows the implementation of the circuit for obtaining the regular horizontal and vertical IC synchronization signals Hp and vp from the above signal 84 (+l), and FIG. 5 shows the timing of FIG.
.

In addition, Fig. 4 shows the gate circuit 111i in Fig. 6)
71, Horizontal synchronization separation circuit (2I) and vertical synchronization separation circuit (2:!This is the part that is the same as the 1st class, but 4'!, 6J is new to each circuit in Figure 4) 4J.

It is numbered.

First, from the signal S4, the regular signal 111! , VP will be explained with reference to FIG. 5. For example, in the 15th H period (not indicated by 15H) in the V, BLK portion of the signal S4 for one song, the data 8 of the code signal is
D is inserted.

First, the signal 84 shown in FIG.
Gate pulse UP1 of one cycle is used. This signal GP is obtained from the oscillator (supplied independently of the g signal S4. In the case shown, the signal 84η) shows the state in which the signal signal G and pulse GP1 are most deviated. .

This pulse GP1 extracts the signal shown in FIG. In the case shown, part of the video portion SV or S■ and V, B
The signal EQ5 in the LK portion is extracted. After the period in which the threshold exists, no signal is extracted, resulting in a no-signal period. When this no-signal period continues, for example, into a 4H period, a gate pulse 010 having a wider pulse width than the pulse OP1 is supplied to gate the signal S4. When the gate is opened with this pulse G1o, the first pulse that passes is signal IP5. When this first signal HP, passes, a pulse G,. falls and the gate is closed. After that, the signal 1 (the subsequent signal UP) can be extracted by supplying the pulse GP1 every 1H from P5.The level of the extracted signal level is shifted using 5 Q I RE as the offset level. According to the above, it is possible to obtain a regular signal HP.
, the signal HP can be obtained by drawing in the circuit during the BLK period.

On the other hand, a gate pulse Gl)2 shown in the fifth diagram, which is delayed by RH from the pulse GP1, is created, and this pulse GP2
gates the signal S4. When the pulse GP is synchronized with the signal 1-IP as described above, this pulse OP2 is at a position corresponding to the no-signal part of the V, BLK part, and the period of the signal VP5 is divided into six pulses GP2. will be catered for. As a result, this pulse OP2 causes six low level portions SL in the period of the signal VP as shown in FIG.
A signal with . After counting this low level portion SL six times and confirming the data 5D between 15HM, that period is determined to be the V, BLK portion, and the gate pulse GP shown in FIG. This pulse O
P3 is the end point of the next field from the above falling point (next V).

BLK start point). Thereafter, by detecting V and IJLK using this pulse OP3 to obtain a signal VP, and further level-shifting this signal vP5 by 5QIRE, a normal signal V l' can be obtained.

Next, the operation of the circuit shown in FIG. 4 based on the above-mentioned principle will be explained.

The scrambled video signal S4 applied to the input terminal 0()) is applied to the gate circuit 01), and after being inverted by the inverting circuit 02), is applied to the gate circuit (c).

The gate circuit C'1llC31 is opened every 1 i] by the Gert pulse OP1 obtained by dividing the 14 MHz signal output from the reference oscillator 0→ into cans by the frequency divider 05). Kate times Wr L3+1 G:3)
The gated signal is applied to an adder C37), from which the signal of FIG. 5C is obtained. When the time constant circuit C38) detects that this signal has become a no-signal state continuously in the 4HIJJ direction, the time limit circuit C (91) is operated to output the gate pulse GP1o, and this pulse GP10 causes the gate circuit (1311Ca1 is opened.The timer circuit (39)
is reset, the pulse GP1o falls, and the gate circuit 16c3υ03) is closed. From then on, adder C37+
IP5 (by resetting the frequency divider Om by the input signal, the pulse GP and the signal ILP5 are synchronized. As a result, the signal 1111'5 is separated, and this separated signal) IP5 is restored to its original level by the restoration circuit (40), thereby obtaining a normal signal HP.

On the other hand, after the signal IMP5 is synchronized with the signal 0P1o, the signal IMP5 is delayed by %H in the delay circuit (4I) and becomes the gate pulse (JP2).
P2 opens a gate circuit (431) every 1H through a switch (421).A signal S4 is applied to this gate circuit (431), and by opening the gate, the gate circuit (431) is opened every 1H.
The signal shown in Figure E is obtained. Further, the control circuit (44) including a counter for counting the pulse GP1 detects the low level part SL of the signal shown in FIG. Detects the H period of . This detection signal causes the data extraction circuit (451
extracts the data SD and adds it to the judgment circuit (41i1).

The data SD consists of, for example, 64 bits, the first 8 bits of which are data indicating that it is a Sfuranzuru broadcast. When the determination circuit (4b) confirms the above data, it switches the switch (4z1).

The control circuit (4a) has a flip-flop (47j) set to V.

A signal is created that is set at the beginning of the BLK period and reset at the end of the 15th I (period) in which the data SD is inserted, and this causes the flip-flop (
4η') I'm happy with the pulse GP3 in Figure 15F. Thereafter, this pulse GP3 is passed through a switch (4z) to a gate circuit (431), whereby the V, l3LI< portion including the signal ~'P5 is gated.
) can obtain a normal signal VP by returning the gated signal vP8 to its original level.

Effects of the Invention The present invention provides the following advantages:1. Since the BLK portion is level-shifted, it is no longer possible to separate the synchronization signal in the usual way at the receiving end, which causes the screen to become out of sync and creates a scrambling effect that causes color errors.

Furthermore, in the present invention, the level of the BLR portion is shifted, and at the same time, any horizontal blanking period and/or any video portion is roughly inverted at a predetermined aliasing level. Separation becomes completely impossible, and color demodulation becomes even more difficult, making it possible to prevent unauthorized reception.

Further, in the present invention, since the offset level for performing the level shift is set to the 5 DI BE intermediate brightness level, there is no need to send a signal indicating the reference level for performing the descramble.

[Brief explanation of drawings]

Fig. 1 is a signal waveform diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing an embodiment of the transmitting side circuit, Fig. 6 is a block diagram showing an embodiment of the receiving side circuit, and Fig. 4 is a synchronization diagram. A block diagram showing an embodiment of a circuit for restoring a signal, and FIG. 5 is a timing chart of FIG. 4. In addition, in the codes used in the drawings, (1)......Video signal source (3)
・・・・・・・・・・・・H,BLK circuit (6)...
......Inverting/non-inverting circuit S4. S4...
It is a scrambled video signal. Agent Masaru Doyo〃 Yoshio Tsunekako〃 Toshiki Sugiura

Claims (1)

[Claims] 1. A television signal scrambling method characterized by level-shifting the horizontal blanking period in the entire period of the television signal of a specific program to a predetermined level. 2. The television signal scrambling method according to claim 1, wherein any horizontal blanking period and/or any video portion is inverted at a predetermined aliasing level. 6. The television signal scrambling method according to claim 1, wherein the offset level for performing the level shift is set to a 53IRE intermediate brightness level.