JPS60256287A - Transmission system of television signal - Google Patents

Abstract

PURPOSE:To prevent degradation in picture quality by placing a scanning line of an odd-numbered order into an odd-numbered order even after the replacement and placing a scanning line of an even-numbered order into an even-numbered order even after replacement in replacing the scanning line. CONSTITUTION:An analog video signal to be scrambled is inputted to a terminal 1 in a scrambler at the broadcast station side, and after this signal passes through an LPF2, it is fed to an A/D converting circuit 3 and a master clock oscillator 4. Then the oscillator 4 produces a master clock having subcarrier frequencies fSC-3fSC based on a color burst signal of the video signal, and the clock is fed to an A/D converter 3, a synchronizing separator circuit 5 and a timing clock generating circuit 6. This converter 3 samples the input video signal by using the master clock and converts it into a digital video signal. This signal is fed to a frame memory 7, written in a ROM8, read from a ROM9 based on the scanning designation signal from a computer 10 and the scanning lines are replaced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a television signal transmission system, and more particularly to a scrambled transmission system that can be applied to scrambled broadcasting and the like.

Background Art and Problems In contract television broadcasting, a broadcasting system called scramble broadcasting is used. Scrambled broadcasting is broadcasting in which the broadcasting station disturbs the television signal using a predetermined method, so that even if those who do not have a contract with the broadcasting station receive the broadcast, they will not be able to view normal images and sound. It is a method.

Then, a decoder will be given to those who have contracted with the line transmission station for contract television broadcasting, and by using this decoder to restore the scrambled television signal to its original form, it will be possible to watch normal images and sound. I have to.

Therefore, in scrambled broadcasting, if the broadcast is received by a non-contractor, it is required to transmit it with high secrecy of television (No. 6) so that the contents are not known as much as possible. Many scrambling methods have been proposed to disturb images and sounds.

For example, a method of inverting the white level and black level of a video signal (Japanese Patent Application No. 13669/1989)
Conventionally, methods have been proposed for replacing the scanning lines (number, etc.) and scanning lines.

The above-mentioned scrambling method in which scanning lines are replaced has little deterioration in image quality and is highly confidential, so it is promising for practical use. However, if the scanning lines are interchanged completely arbitrarily, there will be a portion where the color subcarriers are in phase with each other between adjacent scanning lines of the interchanged scanning lines. Furthermore, depending on the content of the original image, the band may be expanded.

In this way, signal processing is performed on the assumption that the scan lines are damaged and the scrambled signal is replaced, and the color subcarriers between adjacent scan lines outstrip each other in reverse phase, as in the case of the NTSO system. If the video is recorded or played back using a VTR or a VTR, the image quality will deteriorate significantly when descrambling is performed. Furthermore, as described above, if a signal whose band has been expanded is passed through a transmission path matched to the band of the original signal, the image quality will deteriorate. Furthermore, the circuit for generating clock pulses based on the color burst signal on the receiving side is also a via circuit.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a scrambling method for solving the above-mentioned problems in the scrambling method using scanning line replacement.

Outline of the Invention In the present invention, when exchanging scanning lines, an odd-numbered scanning line is made to remain an odd-numbered scanning line even after the scanning line is exchanged, and an even-numbered scanning i! ! It is divided by the number that remains even after n permutations. Accordingly, even after the scanning lines are replaced, the color subcarriers for adjacent fixed line lines can be made to have opposite phases to each other.

The 11th entry of the embodiment shows a normal image displayed on the television screen at 7'cja, with n scanning lines ■, ■...
・・・・・・・・・・・・・・・＠There are 9 images or formation sites. Figure B shows a screen obtained by scrambling the video signal having the content of figure A and changing the order of the scanning lines. In this case, in this embodiment, the odd-numbered scanning lines of the person in the same figure are changed so that they become the odd-numbered ones even after being replaced, and the even-numbered scanning lines of the person in the same figure are also changed even after being replaced.
I! I try to make it the first fragrance. As a result of this, the color subcarriers between adjacent scanning lines can be made to have opposite phases even after the scanning lines B in the figure are replaced.

For example, FIG. 2 A1 shows the scanning line ■ of the replacement penalty.

Among ■, ■, and ■, the odd-numbered ■ and ■ are swapped, and the even-numbered ■ and ■ are also swapped.

If (1) and (2), the phase of the color subcarrier is continuous between l adjacent scanning lines as shown in B of the figure. For this one thing,
If ■ and ■ in A of the same figure are replaced, 1 is shown in 0 of the same figure.
The color subcarriers between adjacent scanning lines of this (■) and (2) and between (2) and (2) become discontinuous.

In actual scrambled broadcasting, the scanning line replacement order period and the like may be arbitrarily changed during broadcasting. In addition, a control signal indicating the scrambling mode, such as the scanning line replacement order and period, is inserted at a predetermined position in the vertical blanking period. In the decoder on the receiving side, the above control signal is
Based on this control signal, the entire scrambled television signal is decoded and descrambled.

The control signal is composed of, for example, 8-bit data, and is inserted in such a manner that, for example, the H period of the 12th scan of the vertical blanking period is divided into eight sections, and one bit is assigned to each section. The contents of the 8 bits indicate the scrambling mode, which includes, for example, the order in which scanning lines are replaced (91 types are 50 types), the time for scrambling, and so on.

Furthermore, if the vertical blanking period is also made to participate in scrambling, the scrambling effect can be further enhanced.

Next, embodiments of a scrambling device on the broadcasting station side for performing the above-mentioned scrambling and a descrambling device for descrambling on the receiving side decoder l will be described.

FIG. 3 shows an embodiment of the scrambling device.

In the figure, an analog video signal to be scrambled is input to input terminal 1. This video signal is band-limited through a low-pass filter 2 and then applied to an A/D converter 3 and a master clock generation circuit 4. The master clock generation circuit 4 generates a master clock having a frequency of 3 fBc from the subcarrier frequency f8C based on the color burst signal of the video signal, and connects the A/D converter 3, the synchronization separation circuit 5, and the tie clock generation circuit. 6
Add to. The A/D converter 3 samples the input video signal using the mask clock and converts it into, for example, an 8-bit digital video signal. This digital video signal is applied to the frame memory 7 and also to the synchronization separation circuit 5 to separate horizontal and vertical synchronization signals.

The timing clock generation circuit 6 generates a predetermined timing clock based on the synchronization signal and the master clock, and outputs it to the address conversion ROM 8.9 and the computer device 1.
Add to 0.

The frame memory 7 stores the digital video signal in one
It has the capacity to store one frame, and the above address conversion RO
Writing is performed using a write address signal obtained from M8, and reading is performed using a read address signal obtained from address conversion ROM9. The scan lines of this readout signal are replaced, that is, scrambled, as shown in FIG. 1B, resulting in nine scan lines. For this purpose, the address conversion ROM 8 converts the scanning line number generated from the timing clock into an address where the input data of the frame memory I is actually written. Further, the address conversion ROM 9 determines the actual read address based on the scanning line number generated from the timing clock and the read scanning line designation signal obtained from the computer system [10].

The computer system f110 has a keyboard 11, a microprocessor 12, and a program 0M13. Work RAM1
4, an interface 15, a display device 16 consisting of a cathode ray tube, etc. The keyboard 11 is used to change the scramble content. Program) LOM
i3 stores the contents of the scramble, that is, the order in which the plurality of types of scanning lines are replaced, the scramble time, etc., and the system program for operating the computer. Further, the buffer memory 17 is connected to the computer device 10.
This signal is used for speed adjustment between the readout scanning line designation signal obtained from the frame memory 7 and the frame memory 7 that requires this signal.

The scrambled digital video signal read out from frame memory 7 as described above is then applied to control signal insertion circuit 18 and obtained from computer system ff1110. The aforementioned control signal indicating the scrambling mode can be inserted at a predetermined position in the vertical blanking period.

The scrambled digital video signal into which the control signal has been inserted is converted into a scrambled analog video signal by the D/A converter 19, and after the clock component is removed through the low-pass filter 20, it is output from the output terminal 21. Note that other scrambling methods such as inverting the white level and black level described above may be used in combination. In that case, the output signal of the frame memory 7 may be scrambled using another method.

FIG. 4 shows in more detail the circuit for performing the above-mentioned scanning line replacement, and parts corresponding to those in FIG. 3 are given the same reference numerals. Note that the address table 20 in the figure is a circuit integrated with the address conversion ROM 8.9f in figure Wc2.

In FIG. 4, first, switch 21 is closed to the light side, and switch 22 is also closed.

As a result, data is sequentially written into the buffer memory 17 according to the address signal received from the buffer address counter 23. This data is a program 几0M1
3 by the keyboard 11, which indicates the order of the scan lines on the scrambled screen. The frame memory 7 has a line memory configuration in which one scanning line is treated as one block, and one piece of data is required for one scanning line.

When the writing of data to the buffer memory 17 is completed, the switch 21 is closed to the read side and the switch 22 is opened. As a result, data can be read from the buffer memory 17 or by the address signal obtained from the read pointer generation circuit 24 every 1H. This is to determine the address of the scanning line when reading out the fc flaw signal frame memory 7, and the address table 20 outputs a read address signal to the output terminal 26 based on the above signal. Further, the write point generation circuit 25 outputs a signal for determining the address of the scanning line to be read into the frame memory 7, and based on this signal, the address table 20 outputs a write address signal to the output terminal 27.

Therefore, the address table 20 has 525 addresses in one frame period.
Outputs the read address signal and write address signal. Note that the control signal is outputted to the output terminal 28.

Further, a timing clock is applied to the input terminal 29 from the timing clock generation circuit 6 of FIG. 2, and is supplied to a predetermined circuit.

FIG. 5 generates scrambled data according to the scramble mode specified in the flow for the computer device 10. Furthermore, a control 11 signal indicating the scramble mode is generated and inserted into the vertical blanking period. The scramble mode can be changed at any time using the keyboard 11.

FIG. 6 shows a descrambling device in a receiving side decoder.

This descrambling device basically has substantially the same configuration as the scrambling device shown in FIG. 3, and therefore circuits corresponding to those in FIG. 3 are given the same reference numerals.

In FIG. 6, a scrambled video signal is applied to the input terminal 31, and a descrambled normal video signal is obtained at the output terminal 32. Also, the control signal detection circuit 33
The control signal is extracted from the signal obtained from the A/D converter 3. By decoding the computer 921fi10 cascade mode based on this control signal, the digital video signal restored to its original form can be read out from the frame memory 7.

FIG. 1 shows a flowchart regarding the computer unit t10 in the descrambler.

The "key parakeet" step in this flowchart is an operation for enabling the descrambling device fIL.

That is, in the case of contract television broadcasting, the descrambling device becomes operational when the user pays a fee. Specifically, a secret card or other method such as an iE number is used. Alternatively, a subscriber number may be attached to the subscriber, and the subscriber number that paid the fee may be added to the scrambled broadcast signal and transmitted, and the decoder side may detect this.

Effects of the Invention According to the present invention, it is possible to increase secrecy through scanning line replacement while eliminating deterioration in image quality.

Furthermore, a particularly complicated circuit for generating a clock from a color burst signal on the receiving side is not required.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a television screen for explaining the present invention in principle, FIG. 2 is a waveform diagram for explaining the present invention in detail, and FIGS. 3 to 7 show examples of the present invention. Figure 3 is a block diagram of the scrambling device, Figure 4 is a block diagram of the part that replaces the scanning lines in Figure 3, Figure 5 is a flowchart of the computer device in Figure 3, and Figure 6 is a block diagram of the descrambler. 7 is a flowchart of the computer device of FIG. 6. In addition, in the symbols used in the drawings, 7 ・・・・・・・・・・・・・・・Frame memory 8
．． 9・・・・・・・・・Address conversion ROM10
・・・・・・・・・・・・・・・Computer equipment. Agent Masaru Ueya Yoshio Tsuneko A Figure 1: A B 52 2 Figure 5 Special opening aGO-256287 (8) Figure 7

Claims (1)

[Claims] The scanning lines are replaced, and when performing this replacement, the odd-numbered scanning lines are made to remain the odd-numbered numbers even after the replacement, and the even-numbered scanning lines are made to be the even-numbered numbers even after the replacement. A television signal transmission system developed in this way.