JPH0757026B2 - Television signal transmission system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal transmission system, and more particularly to a scramble transmission system applicable to scramble broadcasting and the like.

Background Art and its Problems In contract television broadcasting, a broadcasting system called scrambled broadcasting is used. Scrambled broadcasting is a broadcasting system in which the broadcasting station side disturbs the television signal based on a predetermined method so that those who do not have a contract with the broadcasting station can not view normal images and sounds even if they receive the broadcasting. Is. In the contract television broadcasting, a decoder is given to a person who has a contract with the broadcasting station, and the scrambled television signal is restored to its original form by using this decoder so that normal images and sounds can be viewed. There is.

Therefore, in scrambled broadcasting, it is required that the television signal be transmitted with high confidentiality so that the content is unknown as much as possible when the broadcast is received by a person who does not subscribe. Therefore, various scrambling methods for disturbing the image and the sound have been proposed in the past. As a method of disturbing an image, for example, a method of inverting a white level and a black level of a video signal (Japanese Patent Application No. 57-13669, etc.) and a method of switching scanning lines have been proposed.

The scrambling method of replacing the scanning lines is practically promising because it has little deterioration in image quality and high confidentiality. However, if the scanning lines are exchanged at will, there is a portion where the color subcarriers are in phase with each other between adjacent scanning lines of the exchanged scanning lines. In addition, the band may be expanded depending on the content of the original image.

In this way, receiving the scrambled signal with the scanning lines interchanged, and performing signal processing under the premise that the color subcarriers between adjacent scanning lines have mutually opposite phases as in the case of the NTSC system, Or record using VTR,
When it is played back, the image quality deteriorates significantly when descrambled. Further, when the signal whose band has been widened as described above is passed through the transmission path matched with the band of the original signal, the image quality is deteriorated. Furthermore, the circuit for producing a clock pulse on the receiving side based on the color burst signal also becomes complicated.

An object of the present invention is to provide a scrambling method for solving the above-mentioned problems in the scrambling method by replacing scan lines.

SUMMARY OF THE INVENTION The present invention provides a first memory for storing data of a plurality of scanning lines of a television signal scrambled by changing the order of a plurality of scanning lines, and a switching order for switching the order of the plurality of scanning lines. , A second memory for storing a control signal indicating a scramble mode such as a switching period, a control signal inserting means for inserting the control signal into a scrambled television signal, and data of the plurality of scanning lines are stored in the first memory. So that the data of the plurality of scanning lines sequentially written in the first memory and written in the first memory are exchanged and read based on the control signal read from the second memory. Control means for controlling each of the two memories, and the control signal is an odd-numbered one even after the odd-numbered scanning lines are replaced. And the even numbered scanning lines are replaced even after the replacement of the even numbered scanning lines, and the control means includes vertical blanking of the television signal in which the control signal is scrambled. The control signal insertion means is controlled so as to be inserted at a predetermined position of the period, and the receiving side detects the control signal and descrambles the scrambled television signal based on the control signal. It is composed.

According to the present invention having such a configuration, color subcarriers for adjacent scanning lines can be made to have opposite phases to each other even after being scrambled by changing the order of the scanning lines, and the vertical blanking is performed. The period can be effectively used for scrambling.

EXAMPLE FIG. 1A shows a television screen when a normal image is displayed, and an image is formed by n scanning lines, .... FIG. 9B shows a screen when the order of the scanning lines is changed by scrambling the video signal having the contents of FIG. In this case, in this embodiment, the odd-numbered scanning lines in FIG. A are made to be odd-numbered even after the replacement, and the even-numbered scanning lines in FIG. A are made even-numbered after the replacement. . As a result, the color subcarriers between the adjacent scanning lines can be in the opposite phases to each other even after the scanning lines in FIG.

For example, the scan line before the replacement shown in FIG.
If the odd-numbered and are replaced, and the even-numbered and are replaced, and then ,, the phase of the color subcarrier is continuous between adjacent scanning lines as shown in FIG. On the other hand, if and are replaced in FIG. A, the color subcarriers between adjacent scanning lines of and and become discontinuous as shown in FIG.

In an actual scrambled broadcast, the scan line exchange order period and the like may be arbitrarily changed during the broadcast. In addition, a control signal indicating a scramble mode such as a scan line replacement order and a period is inserted at a predetermined position in the vertical blanking period. The decoder on the receiving side detects the control signal, decodes the scrambled television signal based on the control signal, and performs descrambling.
The control signal is composed of, for example, 8-bit data, and is inserted in such a manner that the 12th H period of the vertical blanking period is divided into eight sections and one bit is allocated to each section. The content of 8 bits indicates a scramble mode including, for example, a scan line replacement order (for example, 50 types), a scrambling time, and the like.

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

Next, an embodiment of the scramble device on the broadcast station side for performing the above-mentioned scramble and the descramble device for performing the descramble on the decoder on the receiving side will be described.

FIG. 3 shows an embodiment of the scrambler.

In the figure, an analog video signal to be scrambled is input to an input terminal 1. This video signal is band-limited through the low-pass filter 2 and then applied to the A / D converter 3 and the master clock generation circuit 4. The master clock generation circuit 4 creates a master clock having a frequency from subcarrier frequency f _SC to 3f _SC based on the color burst signal of the video signal and adds it to the A / D converter 3, the sync separation circuit 5 and the timing clock generation circuit 6. . A /
The D converter 3 samples the input video signal by the master clock and converts it into an 8-bit digital video signal, for example. This digital video signal is applied to the frame memory 7 and the sync separation circuit 5 to separate the horizontal and vertical sync signals. The timing clock generation circuit 6 creates a predetermined timing clock based on the sync signal and the master clock and adds it to the address conversion ROMs 8 and 9 and the computer device 10.

The frame memory 7 outputs the digital video signal 1
Has the capacity to store frames, and has the above address conversion ROM8
Writing is carried out by a write address signal obtained from the above, and reading is carried out by a read address signal obtained from the address conversion ROM 9. The read signal has the scanning lines interchanged, that is, scrambled as shown in FIG. 1B. Therefore, the address conversion ROM 8 converts the scanning line number generated from the timing clock into an address at which the input data of the frame memory 7 is actually written. Also, the above address conversion RO
The M9 determines the actual read address based on the scan line number generated from the timing clock and the read scan line designation signal obtained from the computer device 10.

The computer device 10 includes a keyboard 11, a microprocessor 12, a program ROM 13, a work RAM 14, an interface 15, and a display device 16 including a cathode ray tube and the like. The keyboard 11 is used when changing the contents of scramble. Program ROM13 is the contents of the above scramble,
That is, data such as the order of replacement of a plurality of types of scanning lines, scramble time data, a system program for operating a computer, and the like are stored. The buffer memory 17 is used for speed adjustment between the read scanning line designation signal obtained from the computer device 10 and the frame memory 7 which requires this signal.

The scrambled digital video signal read from the frame memory 7 as described above is then added to the control signal insertion circuit 18 so that the above-mentioned control signal indicating the scramble mode obtained from the computer device 10 is added to the vertical blanking period. Is inserted in place. The scramble digital video signal in which the control signal is inserted is converted into a scramble analog video signal by the D / A converter 19, and the clock component is removed by the low pass filter 20 and then output from the output terminal 21. It should be noted that another scrambling method for inverting the white level and the black level described above may be used together. In that case, the output signal of the frame memory 7 may be scrambled by another method.

FIG. 4 shows in more detail the above-mentioned scanning line replacement circuit, and the parts corresponding to those in FIG. 3 are designated by the same reference numerals. The address table 20 in the figure is a circuit in which the address conversion ROMs 8 and 9 shown in FIG. 2 are integrated.

In FIG. 4, first, the switch 21 is closed to the light side, and the switch 22 is closed. As a result, data is sequentially written in the buffer memory 17 by the address signal obtained from the buffer address counter 23. This data is read from the program ROM 13 by the keyboard 11 and indicates the order of the scanning lines of the scrambled screen. The frame memory 7 has a line memory structure in which one scanning line is treated as one block, and one data is required for one scanning line.

When the writing of the data to the buffer memory 17 is completed, the switch 21 is closed on the read side and the switch 22 is opened.
As a result, the buffer memory 17 is read by the address signal obtained from the read pointer generation circuit 24 every 1H. This read signal determines the address of the scanning line when reading the frame memory 7, and the address table 20 outputs a read address signal to the output terminal 26 based on the above signal. In addition, the line point generation circuit 25
Outputs a signal for determining the address of the scanning line when writing to the frame memory 7, and the address table 20 outputs a write address signal to the output terminal 27 based on this signal. Therefore, the address table 20 is 525 in one frame period.
The read address signal and the write address signal are output. The control signal is output to the output terminal 28. Further, a timing clock is added to the input terminal 29 from the timing clock generation circuit 6 of FIG. 2 and supplied to a predetermined circuit.

FIG. 5 shows a flow chart for the computer device 10.

In the microprocessor 12, scramble data is created according to the scramble mode designated by the keyboard 11. Also, a control signal indicating the scramble mode is created and inserted in the vertical blanking period. The scramble mode can be changed by the keyboard 11 at any time.

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

This descrambling device is basically constructed in substantially the same manner as the scrambling device of FIG. 3, and therefore the circuits corresponding to those of FIG. 3 are designated by 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. Further, a control signal detection circuit 33 is provided, and the control signal is extracted from the signal obtained from the A / D converter 3. The computer device 10 decodes the scramble mode on the basis of this control signal, whereby the digital video signal restored to the original form is read from the frame memory 7.

FIG. 7 shows a computer device 10 in the descrambling device.
FIG.

The "key-in" step in this flow chart is the operation that enables the descrambling device. That is, in the case of contract television broadcasting, the descrambling device can be operated when the user pays the fee. Specifically, a personal identification number by a method such as a card is used. Alternatively, the contractor number may be attached to the contractor, the contracted contractor number for which a fee has been paid 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, since the color subcarriers for adjacent scanning lines also have opposite phases in the television signal after being scrambled by changing the order of the scanning lines, the scanning lines are exchanged. This makes it possible to effectively prevent the deterioration of image quality even though the confidentiality of the television signal can be increased, and the circuit for generating the clock from the color burst signal on the receiving side requires a particularly complicated circuit. Not.

Also, the order of swapping the order of a plurality of scan lines,
A control signal indicating a scramble mode such as a replacement period is inserted into the scrambled television signal, and the receiving side detects the control signal and descrambles the scrambled television signal based on this control signal. Therefore, the scrambled television signal can be descrambled very easily on the receiving side even if the order of switching a plurality of scanning lines and the order of switching are changed in various ways. For this reason, the confidentiality of the television signal can be further enhanced by the descrambling by the replacement of the scanning lines.

Further, since a control signal indicating a scrambling mode such as a switching order and a switching period for switching the order of a plurality of scanning lines is inserted at a predetermined position in the vertical blanking period of the scrambled television signal, the vertical blanking is performed. The time period can be effectively used for scrambling, which can result in a higher scrambling effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a television screen for explaining the principle of the present invention, FIG. 2 is a waveform diagram for explaining the effect of the present invention, and FIGS. 3 to 7 are examples of the present invention. FIG. 3 is a block diagram of the scramble device, FIG. 4 is a block diagram of the part for performing the scan line replacement of FIG. 3, FIG. 5 is a flow chart of the computer device of FIG. 3, and FIG. 6 is a descramble device. A block diagram and FIG. 7 are flow charts of the computer device of FIG. The reference numerals used in the drawings are: 7 ... frame memory 8, 9 ... address conversion ROM 10 ... computer device 17 ... buffer memory 18 ... control signal insertion circuit.

Claims (1)

[Claims] 1. A first memory for storing data of the plurality of scanning lines of a television signal scrambled by changing the order of the plurality of scanning lines, and a rearrangement order for rearranging the order of the plurality of scanning lines,
A second memory for storing a control signal indicating a scramble mode such as a replacement period, a control signal inserting means for inserting the control signal into a scrambled television signal, and data of the plurality of scanning lines are stored in the first memory. The first and second so that the data of the plurality of scanning lines which are sequentially written in the memory and written in the first memory are interchanged and read based on the control signal read from the second memory. And a control means for controlling each of the memories, wherein the control signal is an odd-numbered scan line even after the odd-numbered scan lines are replaced, and an even-numbered scan line after the even-numbered scan lines are replaced. The control means is configured to perform a replacement, and the control means is a vertical blanking device for a television signal in which the control signal is scrambled. The control signal inserting means is controlled so that the control signal is inserted at a predetermined position in the video signal period, and the receiving side detects the control signal and descrambles the scrambled television signal based on the control signal. A transmission method of a television signal, which is characterized in that