KR0159413B1 - Descrambler for cancelling the reference signal - Google Patents

Abstract

The present invention relates to a descrambler having a reference signal removal function, wherein a non-inverted video signal and an inverted video signal are selectively output based on the descrambler information from a transmitting station and provided to an offset level detector and a second switch. The offset level detector detects the offset level of the scrambled video signal based on the color burst signal separated by the synchronization separator in the descrambler. The image signal output from the first switching unit and the offset level from the offset level detector are based on the selection pulse from the selection pulse generator based on the horizontal synchronizing signal separated by the synchronization separation unit in the descrambler. By selectively switching and outputting, it is possible to effectively remove the reference signal inserted in the scrambled video signal in the descrambler without separately employing the module for removing the reference signal, thereby simplifying the structure and reducing the manufacturing cost.

Description

Descrambler with reference signal rejection

1 is a schematic block diagram of a descrambler having a reference signal cancellation function according to a preferred embodiment of the present invention.

2 is a view for explaining an operation of removing a reference signal inserted in the scrambled video signal in the descrambler according to the present invention.

3 is a schematic block diagram of a conventional conventional reference signal removing device.

4 is a view for explaining an operation of removing a reference signal inserted in a descrambled video signal according to a conventional method.

* Explanation of symbols for main parts of the drawings

600: descrambler 610: amplifier

615: synchronization separator 620: reference pulse generator

625: selection pulse generator 630: reference signal detector

635: analyzer 640: non-inverting

645: inverting section 650, 660: switching section

655: offset level detector 700: sink detector

750: pedestal level detection unit 800: comparison unit

850: pulse generator 900: selector

The present invention relates to a descrambler (DESCRAMBLER), and more particularly, to a descrambler having a reference signal removal function for removing a reference signal inserted in an image signal scrambled in a descrambler. It is about.

Typically, a coaxial cable is connected between a transmitting station and a subscriber's receiver, and when the transmitting station transmits a broadcast signal through the coaxial cable, the receiver's receiver receives the image and transmits the image to a receiver of a television (hereinafter referred to as TV). A method of viewing a broadcast signal from a transmitting station by outputting a signal and outputting an audio signal to a speaker of a TV is called a cable television (hereinafter referred to as CATV).

On the other hand, the transmitting station is a method for preventing the non-subscriber from illegally connecting the coaxial cable to watch the broadcast signal from the transmitting station, and the horizontal synchronization signal and the color burst signal section in one horizontal line video signal. The receiver of the subscriber by inverting the effective video signal appearing on the TV receiver aperiodically around a predetermined reference level, for example, 50 IRE (a unit in which the size of the video signal is specified by the INSTITUDE RADIO ENGINEER) To send.

Inverting the effective video signal as described above aperiodically is called scramble, and restoring the scrambled effective video signal back to the original valid video signal is called descrambling, and a device for performing the same is called a descrambler. do.

At this time, the transmitting station is part of a method for descrambled the scrambled effective operation signal at the receiver of the subscriber, in the Republic of Korea, the reference level inverted the effective video signal in the back porch of the horizontal line video signal typically It is inserted and transmitted. This is called a reference signal.

Here, the back porch is called a back porch in the sense that it exists after the color burst signal of one horizontal line video signal, and in general, the TV receiver detects an average level of the color burst signal to determine the brightness of the effective video signal. The brightness is divided from black to white based on the size of the effective video signal based on the level.

3 is a schematic block diagram of a conventional reference signal removing device, which includes a descrambler 600, a sink detector 700, a pedestal level detector 750, a comparator 800, and a pulse generator 850. ) And a selection unit 900.

In FIG. 3, the descrambler 600 descrambles an effective video signal scrambled at a transmitting station, and the sink detector 700 receives a descrambled video signal when a descrambled video signal is input from the descrambler 600. The pulse corresponding to the color burst signal in the signal is provided to the pedestal level detector 750, and the sink detector 700 transmits a pulse corresponding to the reference signal inserted in the descrambled image signal to the pulse generator 850. to provide.

The pedestal level detection unit 750 detects the pedestal level of the image signal provided from the descrambler 600 based on a pulse corresponding to the color burst signal provided from the sink detection unit 700 (normally). Ground (GND), and then outputs a DC value corresponding to the difference between the detected pedestal level and the ground (GND), and the comparator 800 is connected to the DC value output from the pedestal level detector 750. Based on the compensation, the descrambled video signal output from the descrambler 600 is compensated.

On the other hand, the pulse generator 800 is a selective pulse for selectively outputting the descrambled video signal and the ground (GND) output from the descrambler 600 based on the pulse corresponding to the reference signal from the sink detector 700 And the switching unit 900 selectively switches the descrambled image signal and the ground GND output from the comparator 800 based on the selection pulse generated from the pulse generator 850.

An operation process of a conventional reference signal removing apparatus of the related art, which is constituted as described above, will be described with reference to FIG. 3 and FIG.

First, when the scrambled video signal from the transmitting station is descrambled through the descrambler 600 (FIG. 4A), the color burst signal in the descrambled video signal from the sync detector 700 (T2 section in FIG. 4A). Is generated and supplied to the pedestal level detection unit 750, and to the reference signal (section T3 in FIG. 4a) inserted in the descrambled video signal from the sink detection unit 700. A corresponding pulse (FIG. 4C) is generated and provided to the pulse generator 850.

Then, the pedestal level of the color burst signal is detected by the pedestal level detector 750 in the descrambled video signal based on the pulse (Fig. 4B) corresponding to the color burst signal provided from the sink detector 700. The DC value corresponding to the difference is provided to the comparator 800, compared with the set reference value (typically, ground (GND)), and the image descrambled corresponding to the DC value from the pedestal level detector 750. The signal is compensated through the comparator 800 and provided to the selector 900.

On the other hand, a selection pulse for selectively outputting the descrambled image signal and the ground (GND) from the pulse generator 850 based on the pulse (Fig. 4c) corresponding to the reference signal provided from the sink detection unit 700 The descrambled video signal and ground GND through the comparator 800 are selectively switched in the selector 900 based on the selection pulse from the pulse generator 850 (FIG. 4D).

However, the conventional reference signal removing apparatus as described above removes the reference signal inserted in the descrambled video signal by mounting a separate module 700-900 outside the descrambler 600, thereby increasing the manufacturing cost. There is a problem.

Accordingly, an object of the present invention is to provide a descrambler having a reference signal removing function capable of removing a reference signal inserted in an scrambled image signal in a descrambler without an additional module unit.

In order to achieve the above object, the present invention provides a device for descrambling a scrambled video signal provided from a transmitting station to prevent city office, comprising: amplifying the scrambled video signal transmitted from the transmitting station to a predetermined level; Sync average means for separating a color burst signal and a horizontal sync signal among the amplified scrambled video signals, and detecting the average level of the color burst signal by using the color burst signal separated from the sync separation means and separating the sync signal. Level detection means for detecting a reference level using the horizontal synchronization signal separated from the means, selection pulse generation means for generating a selection pulse for removing the reference signal based on the horizontal synchronization signal separated from the synchronization separation means; Compensating for the difference between the reference level and the average level detected by the level detecting means. And a video descrambler for descrambled by inverting or non-inverting the scrambled video signal output from the comparator based on descrambled information from the outside, and provided by the video descrambler. An offset level detecting means for detecting an offset level of the descrambled video signal and a video signal provided from said offset level detecting means and said video descramble means on the basis of a selection pulse from said selection pulse generating means; It provides a descrambler having a reference signal removal function, characterized in that consisting of a switching means.

Other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic block diagram of a descrambler having a reference signal cancellation function according to a preferred embodiment of the present invention. As can be seen from the drawing, a descrambler having a reference signal removing function according to the present invention includes an amplifier 610, a synchronization separator 615, a reference pulse generator 620, and a selective pulse generator 625. , The reference signal detector 630, the comparator 635, the non-inverting unit 640, the inverting unit 645, the first switching unit 650, the offset level detection unit 655, and the second switching unit 660. do.

Meanwhile, in FIG. 1, the amplifier 610, the synchronization separator 615, the reference pulse generator 620, the reference signal detector 630, the comparator 635, the non-inverting unit 640, and the inverting unit. 645 and the first switching unit 650 is a constituent member in the conventional descrambler 600, the operation process of the descrambler 600 will be described first with reference to FIG. 1 and FIG. Same as

First, the scrambled video signal transmitted from the transmitting station is amplified to a predetermined level for descrambling through the amplifier 610 (FIG. 2a), and the color burst signal of the scrambled video signal scrambled by the synchronization separator 615. Bs) and the horizontal synchronization signal Hs are separated, and the horizontal synchronization signal Hs is provided to the reference pulse generator 620 and the selection pulse generator 625, and the color burst signal Bs is the offset level to be described later. The detection unit 655 is provided.

Then, a pulse for detecting the position of the reference signal inserted in the scrambled image signal from the reference pulse generator 620 based on the horizontal synchronization signal Hs separated by the synchronization separator 615 (FIG. 2B) The reference level of the reference signal (T3 section in FIG. 2a) inserted in the scrambled video signal by the reference signal detector 630 is detected and provided to the comparator 635 based on the pulse.

Then, among the scrambled video signals amplified to a predetermined level set by the amplifier 610, the average level of the pedestal signal is detected by the comparator 635 and compared with the reference level provided from the reference signal detector 630. As a result, the compensator 635 compensates for the difference and then provides the non-inverting portion 640 and the inverting portion 645.

In this case, the image signal input to the non-inverting unit 640 is not inverted, but is input to the first switching unit 650, and the image signal input to the inverting unit 645 is inverted around the reference level so that the first switching unit is inverted. Input to 650, the first switching unit 650 is descrambled and output based on the descrambling information from the transmitting station.

Meanwhile, the present invention is characterized by further including a selection signal generator 625, an offset level detector 655, and a second switching unit 660 in a conventional descrambler as described above. The description of the operation of these components and the operation of removing the reference signal in the scrambled video signal will mainly be described.

In FIG. 1, the selection pulse generator 625 uses the horizontal synchronization signal Hs separated by the synchronization separator 615 to output an image signal and an offset level detector from the first switching unit 650. 655 generates a selection pulse (Fig. 2c) for selectively outputting the offset level (OFF-SET LEVEL), and the offset level detector 655 is based on the color burst signal separated by the synchronization separator 615. To detect an offset level of the descrambled video signal output from the first switching unit 650, and the second switching unit 660 is configured to generate the first switching unit (based on the selection pulse from the selection pulse generator 625). The video signal output from 650 and the offset level from the offset level detector 655 are selectively output.

The de-scrambler 600 further includes a selection pulse generator 625, an offset level detector 655, and a second switch 660 in the descrambler 600. The operation of the scrambler will be described in more detail.

First, an image signal that is selectively switched and output from the first switching unit 650 based on the descrambling information is provided to the offset level detecting unit 655 and the second switching unit 660, and is synchronized with the descrambler 600. The offset level of the image signal provided to the offset level detection unit 655 is detected based on the color burst signal separated by the separation unit 615 and provided to the second switching unit 660.

Next, the selection pulse for removing the reference signal from the descrambled video signal from the selection pulse generator 625 based on the horizontal synchronization signal Hs separated by the synchronization separator 615 in the descrambler 600 ( 2c), this selection pulse is a selection pulse for selectively switching the image signal output from the first switching unit 650 and the offset level from the offset level detection unit 655.

Accordingly, the image signal output from the first switching unit 650 and the offset level from the offset level detection unit 655 are selectively switched and output based on the selection pulse from the selection pulse generator 625, thereby scrambled the image. The reference signal is removed from the signal.

For example, as illustrated in FIG. 2C, the video signal from the first switching unit 650 is output in the sections T1 and T2 where the selection pulse from the selection pulse generator 625 is a high level signal. In the period T4 where the switching is performed by the second switching unit 660 and the selection pulse from the selection pulse generator 625 is a low level signal, the offset level detected by the offset level detection unit 655 is the second switching unit 660. ), And the video signal from the first switching unit 650 is switched in the period T5 in which the selection pulse from the selection pulse generator 625 is a high level signal, as shown in FIG. The reference signal is removed.

As described above, the non-inverted video signal and the inverted video signal are selectively output based on the descramble information from the transmitting station and provided to the offset level detector 655 and the second switching unit 660, and the descrambler. The offset level of the scrambled video signal is detected by the offset level detector 655 based on the color burst signal Bs separated by the synchronization separator 615 in 600. Then, the image output from the first switching unit 650 based on the selection pulse from the selection pulse generator 625 based on the horizontal synchronization signal Hs separated by the synchronization separator 615 in the descrambler 600. The offset level from the signal and the offset level detector 655 is selectively switched by the second switching unit 660 and output.

Therefore, the present invention can effectively remove the reference signal inserted in the scrambled video signal in the descrambler without separately employing the module for removing the reference signal, thereby simplifying the structure and reducing the manufacturing cost. have.

Claims (1)

An apparatus for descrambling a scrambled video signal provided from a transmitting station for preventing city hearing, the apparatus comprising: amplifying a scrambled video signal transmitted from the transmitting station to a predetermined predetermined level and then performing color burst in the amplified scrambled video signal. Synchronization separating means (610, 615) for separating the signal from the horizontal synchronization signal; Level detecting means for detecting an average level of the color burst signal using the color burst signal separated by the sync separating means (610, 615) and detecting a reference level using the horizontal sync signal separated from the sync separating means. 620, 630; Selection pulse generation means (625) for generating a selection pulse for removing the reference signal based on the horizontal synchronization signal separated by the synchronization separation means (610, 615); A comparator 635 for compensating for the difference between the reference level and the average level detected by the level detection means (620, 630); Image descramble means (640, 645) for descrambled scrambled video signal output from the comparator 635 by inverting or non-inverting based on descrambling information from the outside; Offset level detection means (655) for detecting an offset level of the descrambled video signal provided from said video descramble means (640, 645); Switching means 660 for selectively outputting the video signals provided from the offset level detecting means 655 and the image descramble means 640, 645 based on the selection pulse from the selection pulse generating means 625; Descrambler having a reference signal removal function, characterized in that made.