JPS58178687A - Scrambler - Google Patents

Abstract

PURPOSE:To raise an effect of scramble and also to execute descramble completely, by adding or subtracting a signal which executes at least one processing of delay and level attenuation to a video signal, to or from its original video signal. CONSTITUTION:A signal Sa is supplied to a subtracting circuit 11, also is supplied to a delaying circuit 12 and becomes a signal S12 which is delayed by a period (tau). The signal S12 is multiplied by K by an attenuator 13, becomes a signal S13, is supplied to the circuit 11, and a signal Salpha=Sa-S13 is fetched, is converted to a television signal SA by a modulating circuit 2A, and is sent out. The signal SA has a ghost component by the signal S13, therefore, when its signal SA is received without descrambling it, a ghost by the signal S13 is generated. Also, a waveform of vertical and horizontal synchronizing pulses is put into disorder by a ghost component.

Description

[Detailed Description of the Invention] For example, ■F television broadcasting in the United States is shown in Figure 1A.
As shown in the figure, it is carried out on channels 2 to 13, but CATV broadcasting is carried out on Jl! lli! Im a blank part of VHF TV broadcast as shown? This is carried out on the A-W channels. And in this CATV broadcast, A-
The W channel CATV broadcast signal and the ■F TV broadcast signal of channels 2 to 13 are sent together through a single coaxial cable.

In this type of CATV broadcasting, special signal processing is performed on certain channels, so that general viewers cannot watch the broadcasts on that channel, but subscribers who wish to do so can enjoy the privilege of watching the broadcasts on that channel. There is a system that allows you to do this.

This special signal processing is called "scrambling," and the device for performing this scrambling is called a "scrambler." The signal processing that performs the opposite signal processing of scrambled channels to enable viewing of the broadcast is called ``desk simple'', and subscribers are required to perform this descrambling. A round adapter is provided, and this adapter is called a "descrangler."

The present invention aims to provide a scrambler that has a large scrambling effect and can perform complete descrambling.

An example of this will be explained below.

In FIG. 2, (lm)-(IN) indicates the signal source,
From these signal sources (IA) (IN), standard video signals (baseband color image
No.) S-8 is taken out. In addition, this example
In n, it is assumed that the channel of the signal S1 is scrambled.

And the unscrambled channel signal S, ~
S1 is supplied to the modulation circuits (2B) (2N) and converted into TV signals of each channel (TV broadcast band signals) S, ~SH, and these signals are sent to the coaxial cable for transmission via the NFi adder circuit (3). (4). Therefore, the signal source (IB) and modulation circuit (2B) to (IN)
, (2N), each f'ryne, 1DcATVj
Compatible with i5.

Also, regarding the signal S, the signal source (IA) and modulation circuit (two people) correspond to the CATV station of the channel, but this channel is provided with a second amplifier α4.

B (Pv is vertical synchronization/medium pulse, P.

(Horizontal synchronization) 4 pulses, P6 equalization noise, IH indicates 1 horizontal period), this signal S is supplied to the subtraction circuit 2 and is also supplied to the delay circuit (c) to produce a signal delayed by the period τ. It is assumed that S.2. The details of this delay time τ will be described later, but for example, T = 0.05H (≧3
．． 2j1 seconds), and therefore, the delayed signal '12 becomes as shown in FIG. 3C.

Then, this signal S12 is supplied to the attenuator (to) and is doubled (0≦≦1, in the third figure, =-) as shown in the third diagram to become the signal "1M," which is the 0 signal 81. ．．
is supplied to the subtraction circuit a, and as shown in Figure 3E, the signal '(!='a'15 is taken out, and this signal 8a
is supplied to a conversion circuit (two persons) and converted into a television signal 8□, and this signal S is sent to a coaxial cable (4) through an adder circuit (3).

In this case, the television signal iIA is modulated by the signal 8a, but this is because the video signal B is modulated by only the video signal K, and a ghost wave having the components of the signal S and 3 is superimposed on the television signal 8□. It is equivalent to

FIG. 4 shows the receiving side, and ■ is a descrambler. That is, the signals S, -S, from the coaxial cable (or its distribution line) (4) are supplied to the band removal filter (c), the signal 8m is removed, and the signals S, -SM are taken out, These signals SB to SN are supplied to an antenna terminal of a color television receiver (5) through an adder circuit (2).

Further, the signals 8□ to S□ from the coaxial cable (4) are supplied to the Pantono+S filter (2) to extract the signal S, and this signal S is supplied to the adder circuit (c). Then, the output signal of this adder circuit (2) is supplied to the delay circuit () and delayed by a period T, this delayed signal is supplied to attenuator (4) and multiplied by Supplied.

Therefore, the one-stroke component (the modulated component by the signal 81M) in the signal S1 is removed by the feedback loop between the circuit (c) and the video signal S1.
A standard television signal SA modulated only by the standard TV signal SA is extracted.

This signal 8A is then supplied to the antenna terminal of the receiver (5) through the edge calculation circuit (2). Therefore, if the channel of the receiver (5) is changed, it is possible to watch any channel among the television signals S, -SH corresponding to the change.

Scrambling and descrambling are performed as described above, but in this case, especially according to the present invention, since the scrambled television signal sAF'i has a ghost component due to the signal 811 as described above, When the signal S□ is received (reproduced) without being descrambled, the video detection output becomes the signal Sa shown in Figure E of llA3, and the reproduction signal 85. This causes a ghost to appear.

However, not only that, but also a vertical synchronization pulse Pv and a horizontal synchronization pulse P as shown in FIG. 3E.

Since the waveform of is disturbed by the boost component, its reproduction is not practical because vertical synchronization or horizontal synchronization occurs.

In other words, it is possible to prevent a receiver to which the television receiver is not connected, that is, a viewer other than the subscriber, from viewing the broadcast of the television signal SA without permission.

Furthermore, even if a non-contractor uses a receiver equipped with a ghost removal device, the ghost removal device is
In this invention, since the vertical synchronization signal Pv is disturbed, the scrambled channel cannot be viewed after all. Therefore, the effect of scrambling is positive.

Furthermore, since the desk single is performed using the feed bar cruzi (c)~@ in accordance with scrambling, complete descrambling can be performed and high quality broadcasting can be provided to subscribers.

Moreover, the descrambler■ is used as a delay circuit (2)
If an AW filter is used, everything can be configured with only passive elements, and therefore no power can be used.

In addition, the viewer does not need to distinguish between scrambled channels and non-scrambled channels, and simply selects the desired channel, so the operation is simple. Furthermore, there is no need for a special receiver (5) or modification.

By the way, in the above case, the delay time τ is τ-0.05H, but the delay time τ may be any value that disturbs vertical synchronization or horizontal synchronization in a receiver that does not perform descrambling, and is 0. It can be selected to be approximately ≦τ≦0.5H.

i 5 an, t4 pulse width T (-0,
04H)... Signal S when delay time T is changed based on 3. S
Figure 15A if o<r<r, o, garden map BViτ, <τ<2-cho, case (same as Figure 3)
, C in the same figure is the case where τ>2 units. In addition, the 2nd gun is water/
・This is the pulse width of Hei-synchronous/Hei-Russ Ph.

As is clear from Fig. 5, if descrambling is not performed, the waveforms of the vertical synchronization pulse Pv and the horizontal synchronization pulse Ph will be distorted in any case, resulting in a pseudo synchronization pulse. In addition, white peaks may affect the main synchronization separation circuit, and the vertical or horizontal synchronization of the playback screen will be disrupted, resulting in a scrambling effect. be able to.

However, in reality, if the delay time τ is increased, the delay circuit (b) and the delay circuit (b) become expensive, and other characteristics deteriorate. Furthermore, considering the transmission characteristics of the circuit, coaxial cable (4), etc., it is practical that τ≧0.5 μsec (≧0.008H). especially,? = 0.5 μs, the delay circuit υ,
(B) was also practical because it was easy to make.

The same applies to the attenuation ratio k of the attenuators α], 2), and this attenuation ratio should be selected taking into account the delay time τ, but there is a loss in the delay circuit (6), slope, etc. Therefore, in the subtraction circuit a), S 1 in terms of level ratio.
3/8 (attenuation ratio k so that z = about 0.5
It is practical to select

Figure wJ6 shows another example of the scrambler sequence. In this example, a video signal 81 is converted into a video intermediate frequency signal 11 by a modulation circuit (5), and this signal! 1 is syscrambled by the scrambler α1 and then supplied to the frequency converter (6A) where it is converted into a television signal 8□. Note that at this time, in the scrambler (to), the circuit αη is an adder circuit. Therefore, the circuit 2 of the desk lamp 2- is used as a subtraction circuit.

Note that in the above description, scrambling can be performed at the stage of the television signal, and descrambling can also be performed at the stage of the video intermediate frequency signal or the video signal after Fi video detection.

[Brief explanation of the drawing]

Figures 1 and 3 to 1/45 are diagrams for explaining this invention, and Figures 2 and 6 are system diagrams of an example of this invention. (6), 2) is a delay circuit, and I, 2) is an attenuator. ton y 纺筈ノ

Claims (1)

[Claims] In CATV broadcasting, signal processing of at least one of delay and level attenuation is performed on the baseband or TV broadcast band video signal, and this signal-processed video signal is added to the original video signal. Subtract this 7Fl
A scrambler that transmits a video signal that has been subjected to ll calculation or subtraction.