JPH06253307A - Method and device for scrambling television signal - Google Patents

Abstract

PURPOSE:To prevent descrambling by an illegal audience means by irregularly changing the transmission order of a 1st and a 2nd field. CONSTITUTION:The output of an analog switch 41 has frames omitted and skipped, field by field, by a timing signal generating circuit 37 and the field order is converted. Thus, the analog switch 41 converts the relation between odd and even fields of an input video signal irregularly, an encoder 5 performs a compressing process, and the result is outputted to a terminal equipment. Consequently, a horizontal synchronizing signal shifts in position even when an illegal audience device is used, so the signal can not be demodulated into the original signal. When a legal terminal equipment is used, a center side can exactly grasp a horizontal and a vertical compressed blanking period by receiving sent timing data and a key signal and the signal can be descrambled into the original signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scrambled television signal used in a CATV system or the like in which a large number of terminals send video signals to a large number of terminals connected to the center via cables. The present invention relates to a method and an apparatus.

[0002]

2. Description of the Related Art Generally, a CATV system is configured to transmit a program produced in a center or a program broadcast by airwave to a large number of terminals via cables.

In this case, some of the programs produced in the center may be charged. Therefore, when viewing this pay program on each terminal side, an operation such as imposing a charge in advance by a contract for viewing is performed.

Further, in order to prevent the illegal viewing of the pay program, the video signal of the pay program is preliminarily set on the center side so that a non-contracted television cannot receive the video signal. A so-called scramble operation is performed, in which an image is operated at the time of transmission. On the other hand, a descrambling device for returning the scrambled video signal to the original signal is installed on the side of the subscriber who is permitted to watch the pay program.

Various types of scrambling and descrambling methods have been proposed. For example, only the horizontal and vertical sync portions of a television signal are compressed by a few dB into a scrambled signal so that the normal television receiver cannot achieve horizontal and vertical synchronization, while the terminal side which is permitted to view the signal. In the so-called Gated Sync Suppress, the horizontal and vertical sync portions of the television signal compressed by several dB are expanded to the original level to restore the original television signal.
The ion method may be used. Another method is to compress only the horizontal synchronization period.

FIG. 3 shows the above-mentioned Gated Sync.
It shows how scramble processing is performed by the Suppression method. From the end of the horizontal synchronization,
The signal waveforms in the subsequent vertical blanking period are shown.

That is, FIG. 3A shows a state in which a normal television signal is modulated into an intermediate frequency video signal IFv. This intermediate frequency video signal IFv is shown in the figure at the center on the transmitting side. As shown in FIG. 3B, the horizontal synchronizing signal (H) portion and the vertical blanking period (VB
The I) portion is transmitted after being compressed at a specific level, for example, about 6 dB.

At the center, the key signal K indicating the compression timing of the horizontal synchronizing signal is superposed on the intermediate frequency audio signal IFa, and the intermediate frequency video signal IFv and the RF signal are frequency-converted to be sent to the terminal side. I have to.

On the other hand, in the terminal device, the received RF
The intermediate frequency audio signal IFa is separated from the signal, and the key signal K is detected from this signal IFa. Then, based on the detected key signal K, the horizontal synchronizing signal portion in the digitally compressed video signal is expanded by about 6 dB in correspondence with the transmitting side, and the lack of the key signal K is detected and the lack thereof is detected. The period, that is, the VBI part is also 6
A process of returning to the original television signal is performed by expanding the signal by about dB corresponding to the transmitting side.

However, in the case of a television signal scrambled by the above-mentioned scramble system,
It is known that even if it is not a legitimate CATV terminal, it is possible to perform descrambling and relatively easily illegally view.

That is, the intermediate frequency audio signal I
If the timing between the key signal K superimposed on Fa and the horizontal synchronizing signal portion in the digitally compressed video signal can be found, the descrambling operation of the horizontal synchronizing signal portion can be easily performed. Also, it is possible to descramble the vertical blanking period by detecting that the key signals are not continuously superimposed.

Therefore, in order to prevent such illegal viewing, a plurality of types of timings of the position of the video signal to be digitally compressed and the position of the key signal K to be superimposed on the control intermediate frequency audio signal IFa are prepared, and the timing is changed over time. The timing is changed so that it is impossible with the above-mentioned illegal viewing method.

On the other hand, to the regular descrambling device, the timing information is encrypted, and the timing mode data is superimposed on a part of the intermediate frequency audio signal IFa and transmitted, which is then transmitted. In the above, the timing mode data is decoded and the timing of decompression is controlled to be the same as the compression timing on the center side.

However, this time, a device for finding a compressed part from the scrambled video signal itself without using the key signal K and illegally descrambling the television signal is, for example, a RADIO EL.
ECTRONICS May 1990 issue "UNI
VERSAL DECODER ".

FIG. 4 is a block diagram showing the configuration of an example thereof. That is, the television signal sent from the cable C is converted by the frequency converter 111 into the frequency of the channel which is not broadcast in the area, and applied to the descramble circuit 113 and the video detection circuit 115. To be done. On the other hand, the video detection circuit 11
The television signal detected by 5 is 3.58M
It is applied to the timing generator 117 of Hz, and the output synchronized with the color burst signal in the television signal is extracted here.

As is well known, the color burst signal exists immediately after the horizontal synchronizing signal. Therefore, when the frequency phase of the color burst signal is identified, the color burst frequency 3.58 MHz × 2 ÷ 455 = 15.74 kHz ( From the relationship of (horizontal period frequency), the center side, that is, the position of the television signal compressed in the scrambler is inevitably recognized.

The lock output of the timing generator 117 is applied to the sync generator 121. As the sync generator 121, for example, a frequency divider type used in a video camera or the like is used. The timing generator 117 and the sync generator 121 include
A horizontal reset switch 119 and a vertical reset switch 123 are provided respectively.

When both the switches 119 and 123 are turned on and the screen of the television receiver is viewed, a vertical bar due to horizontal blanking and a horizontal bar due to vertical blanking appear on the screen. The vertical blanking bar moves horizontally, and the vertical blanking horizontal bar moves up and down.

Therefore, when the vertical bar due to horizontal blanking reaches the left and right ends, the horizontal reset switch 1
When 19 is turned off, only the horizontal bar due to vertical blanking remains on the screen thereafter, and the vertical blanking moves up and down in this state, so when the upper and lower ends of the screen are reached, the vertical reset switch 123 is pressed. By turning it off, the timing at which the television signal is compressed is set, and a normal screen can be obtained.

Then, the timing signal generator 125 is operated at the set timing described above, and the timing generator 125 sends a control signal to the descramble circuit 113. The descrambling circuit 113 receives the signal from the timing signal generator 125 and selects the switch 113b at the terminal a side, that is, the through position in the horizontal blanking and vertical blanking portions, and otherwise selects the switch 113b at the b side. That is, the original restored television signal can be obtained at the output end 127 by outputting to the output end 127 via the same 6 dB attenuator 113a as the level compressed on the center side.

[0021]

As described above, according to the current illegal viewing means, the Gated Sync Sup is used.
A signal descrambled by analyzing the signal itself scrambled by the compression method has also appeared.

The present invention has been made in view of the above circumstances, and a television signal which can prevent the descrambling due to the illegal viewing means as described above and can use the current regular descrambling apparatus as it is. An object of the present invention is to provide a scrambling method and device.

[0023]

In order to achieve the above object, the first invention of the present application is a television which compresses a predetermined section of a television signal to a specific level and superimposes information related to the compression and sends the information. A method of scrambling a signal, comprising: a first field and a second field of the television signal.
The gist is that the transmission order is changed irregularly with the field of.

The second invention of the present application is a scramble apparatus for a television signal, which compresses a predetermined section of the television signal to a specific level and superimposes information related to the compression and sends the information. John Signal 1st
Means for converting and outputting the transmission order of the second field and the second field, and the output signal of the converting means and the television signal before conversion by the converting means are randomly and alternatively selected. The gist is to have the selecting means and to change the field order of the television signal irregularly and send it out.

[0025]

According to the television signal scrambling method of the first invention of the present application, the descramble is performed by changing the transmission order of the first field and the second field of the television signal irregularly and then transmitting them. Prevent.

In the television signal scramble device according to the second aspect of the present invention, the transmission order of the first field and the second field of the television signal is converted and output by the converting means. Specifically, based on the selection result for each field, a part of the television signal is a normal even field, odd field, even field. ． ． By replacing the even field and the odd field in the order of, the odd field, the odd field, the even field, the even field. ． ． Changes are made for each field such as. Next, since the output signal of this conversion means and the television signal before conversion by this conversion means are randomly and alternatively selected, a part of the television signal may change irregularly from time to time. As a result, a television signal in which the field order is irregularly changed is transmitted.

The television signal to which such an irregular field change is added is sent by compressing the horizontal synchronizing portion and / or the vertical blanking interval in the television to a specific level by the next encoder. It

Therefore, even if the illegal viewing means detects the color burst signal and tries to find the horizontal synchronizing portion and / or the vertical blanking interval, the relation between the fields is irregularly changed, and the color burst signal is synchronized with this. You can't do that, and you can't descramble.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the scrambler according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a scrambling device on the center side according to the present invention.

In FIG. 1, a video / audio source 1 is a video / audio source such as a video tape recorder or a video disc player. The video signal from the video / audio source 1 is applied to the A / D converter 31 which constitutes the conversion circuit 3 and converted into a digital signal.

On the other hand, the video signal is synchronously separated by the sync separator circuit 35, and the sync signal in the video signal is extracted here. The sync signal extracted by the sync separator circuit 35 is applied to the timing signal generating circuit 37, and the write clock W and the read clock R output from the timing signal generating circuit 37.
Is connected to the field memory 33, and the data output of the field memory is connected to the D / A converter 39.

On the other hand, the output of the video source 1 and the D / A
The output of the converter 31 is connected to each input terminal of the analog switch 41, and the field input signal output of the timing signal generating circuit 37 is connected to the control input terminal of the analog switch 41. As a result, the output of the analog switch 41 outputs either the output of the video source 1 or the video signal delayed by one field from the video signal to the encoder 5. The encoder 5 supplies the video signal as it is to the video input terminal of the modulator 7.

On the other hand, the video signal and the audio signal from the video / audio source 1 are applied to the modulator 7, which are respectively modulated and converted into IF signals.

The video IF signal IFv and the audio IF signal IFa converted by the modulator 7 are returned to the encoder 5 again, where the horizontal sync portion and the vertical sync portion in the video signal obtained by the conversion circuit 3 are perpendicular to each other. Based on the blanking period, the video IF signal is compressed by a predetermined compression amount (for example, 6 dB). In addition, the audio IF signal I
For Fa, the key signal K is superimposed on the position corresponding to the horizontal synchronizing portion. Plural types (for example, 6, 15, 25, 33 μsec) of the superposition position of the key signal K are prepared, and the timing thereof is changed with the passage of time. The plurality of types of timings are encrypted as timing data by the encoder 5, and are superimposed on a part of the intermediate frequency audio IF signal IFa.

As described above, the horizontal synchronizing section and the intermediate frequency audio signal IFa in which the video IF signal IFv compressed in the VBI period, the key signal K and the timing data are superimposed.
Are applied from the encoder 5 to the up-converter 9. The up-converter 9 frequency-converts the IF signal into a predetermined RF signal and outputs it to the CATV line.

The analog switch 41 of the conversion circuit 3 is shown in FIG.
The input / output relationship of is shown. FIG. 2A shows a field relationship of video output of the video / audio source 1, and FIG.
Is the field relation of the video signal delayed by the A / D converter 31, the field memory 33, and the D / A converter 39. The output of the analog switch 41 is irregularly dropped or skipped for each field by the timing signal generating circuit 37 as shown in (C) to change the field order.

In the above description, the compression processing is performed in both the horizontal synchronizing section and the vertical blanking period, but it may be limited to the horizontal synchronizing section.

As described above, the relationship between odd and even fields of the input video signal is irregularly converted by the analog switch 41, the above-mentioned compression processing is performed by the encoder 5, and the result is output to the terminal device. As a result, even if the above-mentioned illegal viewing device is used, the position of the horizontal synchronizing signal changes, so that the original signal cannot be demodulated.

On the other hand, in the case of using a regular terminal device, the timing data and the key signal K sent from the center are received to accurately grasp the horizontal portion and the vertical blanking period compressed on the center side. Is possible and can be descrambled to the original signal.

As is apparent from the above description, in the present embodiment, the order of the fields of the television signal is irregularly changed and transmitted, so that descrambling is performed by the illegal viewer which has appeared in the past. It is not possible, and it is possible to descramble the regular terminal device currently used without any modification. This makes it possible to support the sound management of the CATV business.

In the above embodiment, the case where the sending order of the first field and the second field is irregularly changed has been described as an example, but the present invention is not limited to this and, for example, MUSE. It goes without saying that the present invention can be appropriately applied to a system such as a system in which one frame is composed of two or more fields.

[0042]

As described above, according to the present invention, the transmission order of the first field and the second field is irregularly changed, so that the descramble by the illegal viewing means can be prevented. The effect of.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment according to the present invention.

FIG. 2 is a diagram for explaining the operation of the embodiment shown in FIG.

FIG. 3 is a waveform diagram for explaining a scramble operation.

FIG. 4 is a block diagram showing an example of conventional illegal viewing.

[Explanation of symbols]

1 ... Video / audio source, 3 ... Conversion circuit, 5 ... Encoder, 7 ... Modulator, 9 ... Up converter, 31 ...
A / D converter, 33 ... Field memory, 35 ... Sync separator circuit, 37 ... Timing signal generating circuit, 39
... D / A converter, 41 ... Analog switch.

Claims (2)

[Claims] 1. A scramble method for a television signal, comprising compressing a predetermined section of the television signal to a specific level and transmitting information related to the compression in a superimposed manner, the first field of the television signal. A method of scrambling a television signal, characterized in that the transmission order of the first field and the second field is irregularly changed before transmission. 2. A television signal scrambler for compressing a predetermined section of a television signal to a specific level and transmitting information related to the compression in a superimposed manner, the first field of the television signal. And a second field for converting and outputting the transmission order of the second field, and selecting means for randomly and selectively selecting the output signal of this converting means and the television signal before conversion by this converting means. And a scramble apparatus for a television signal, characterized in that the field order of the television signal is irregularly changed and transmitted.