JPS62190A - Picture signal scramble transmission system - Google Patents

Abstract

PURPOSE:To prevent deterioration of picture quality by A/D converting a picture signal, and after making it, to a secret picture signal, D/A converting and transmitting. CONSTITUTION:Input picture analog signals are A/D converted, converted to digital signals, subtracting a fixed value from them, inverting or non-inverting polarity according to scramble key code, adding a fixed value, DA converted, converting to analog signals and the secret picture signals are sample value transmitted. In receiving side, the signals are AD converted again, converted to digital signals, a fixed value is subtracted, inverting or non-inverting polarity according to the scramble key code, a fixed value is added, DA converted again and the original picture is reproduced. In such a way, superposition of noise on a transmission line 9 means that the addition of the same noise as that supplied to a reproduced picture, therefore no damage which may be caused in a conventional equipment is generated, and stable reproduced picture can be obtained.

Description

[Detailed description of the invention] [Technical field of invention] The present invention uses an image signal scramble transmission method C.

[Technical background of the invention and its problems] Scrambling image signals is important for paid broadcasting such as pay television. In other words, pay TV is a system in which only those who pay the fee are informed of the scramble key and can descramble and view the original image, while those who do not pay the fee can only view the scrambled image because they do not have the key.

In order to obtain this scrambled image, images are replaced for each line, and images are replaced within a line, but this requires field memory and line memory, and the hardware is complicated. There was a drawback that absolute delay time occurred.

In addition, since multiple pixels were replaced at once, image secrecy was also poor.

As a pixel-by-pixel scrambling method that performs strong scrambling, a pit replacement method shown in FIG. 2C can be considered.

The image signal is first converted into a multi-bit digital signal (Y) by the A/D converter 1, the bits are replaced by the switch matrix 2g2, and then converted into a digital signal by the D/A converter 3.
/ A-converted and sent to the transmission line 4 as a secret image signal. On the receiving side, the received signal from transmission line 4 is A/
A/D conversion is performed by the D converter 5, and the switch matrix 5 of 6 is
Original order from 2 (yubits are swapped, DA at 7
The original image is converted and reproduced as an image. At this time, bit swapping of bits 2 and 6 corresponds to scrambling and descrambling, and the swapping becomes the encryption key and scramble key.

For example, changing key bits over time is effective (-).

Further, a random number addition method as shown in FIG. 3C is also conceivable.

This method is a method in which signals from a random number generator of C unit 9, for example, an M sequence generator, are added and scrambled by an adder circuit of 8 instead of bit permutations. Similarly on the receiving side (the output of the random number generator in 211 is subtracted by the IO subtraction circuit and descrambled. At this time, the random number may be generated and added every 8 bits of the image signal, for example, , parallel-to-serial conversion (-) may be used to add a C2 random number for each bit as a serial signal.The dynamic range will not be expanded by performing a modulo operation of 28 for 8 bits and a modulo of 2 for 1 bit. .

Of course, although not described in detail, it is necessary to synchronize the transmission and reception of the start timing signal and clock signal for random number generation, and information for this purpose is transmitted, for example, during the blanking period (-).

However, these two methods have the disadvantage that when noise is added to the analog transmission line 4, the noise may be amplified.

Swap (7t, so the left end is LSB and the right end is MSB. Also, in this notation, the 1st bit is the 4th bit Cyu, the 2nd bit is the 8th bit ζ: '138' means to swap.
However, if a small noise of 1 LSB is added on the transmission path and becomes '139', the reproduced data 18' will be correctly received. In this example, the small LSB noise on the transmission path increases the MOB noise C.

Furthermore, noise may increase even when random numbers are added.

When adding random number I40' to the level of '126' and sending out a scramble signal '39' (MOD 12B), if noise is added to 2L8B'2', 141' is received and when this is descrambled, 41-40=1'1' is played.

In other words, since it takes the modulo, when small positive noise is added to the large level (white level), it is converted to the small level (black level) (U), and conversely, when small level C2 negative small noise is added, it is converted to a large level. .

As described above, the conventional 1U system has the disadvantage of increased noise, and the transmission of image signals C2 has the disadvantage of significantly deteriorating the image quality.

[Purpose of the Invention] The purpose of the present invention is to improve the above-mentioned drawbacks of the conventional method, and to provide a stable image signal scramble transmission method that does not fail when descrambling is performed even when noise is added. shall be.

[Summary of the invention] The present invention performs AD conversion of an input image analog signal, converts it into a digital signal, subtracts a certain value, inverts or non-inverts the polarity according to a scramble key code, adds a certain value, and performs post-meal DA conversion. Then, the analog signal is converted into an analog signal C, and the sample value of this curved signal is transmitted.

On the receiving side C-, AD conversion is performed again to convert it to a digital signal, a fixed value is subtracted, and a scramble key code (Y) is therefore inverted or non-inverted, a fixed value is added, and DA conversion is performed again to reproduce the original image. The value can be either positive or negative.

[Effects of the Invention According to the present invention l2, the superimposition of noise on the transmission path is stabilized without causing the deterioration of the reproduced image that occurs with conventional devices, just by adding the same noise as the noise added to the single C2 reproduced image C2. You can browse nine playback images.

In addition, general image processing equipment, such as high-definition television transmission (Society of Communication Engineers Technical Research Report IE94-72P1~
Since image signals are digitally processed in digital televisions (see page 8), scrambling can be performed with a simple circuit configuration consisting of a simple adder and a scramble key code generation circuit.

i + bit by bit ζ with a simple circuit; to scramble,
The encryption scrambling function is so powerful that the scrambled image has no shape of the original image.

[Embodiment of the Invention] The configuration of an embodiment of the present invention is shown in FIG. ′～
'255' Level C Two Dojis.

The subtracter 2 subtracts a constant value, for example '128', from the constant value generating circuit 3. The output signal from the subtracter 2 is selectively inverted or non-inverted by the polarity inversion circuit (5). The scramble key generator 4 is a random number generator, and is realized, for example, by an M-sequence generator.
shows a scrambling circuit composed of a scrambling key generator 4 and a polarity inverting circuit 5. 4 uses an M-sequence generation circuit as a scramble key generator, and on the next side, it is delayed by the period of the image sampling clock from the DFP of 41°42.43. 44 is EXOR, 41
.

4: (The DFF output of (is input.) And the circuit 4.
By using the output of t as the input of 41, a pseudorandom number M sequence is generated from the output of 43. Each DFF has a frame synchronization signal (initial value is set from 2. This frame synchronization signal is a blanking period in another channel or image signal, horizontal or vertical synchronization signal part C; multiplexed and scramble key generator on the receiving side. 13 (: is supplied. From C2, synchronization is established so that the same image signal (-) corresponds to the same scramble key on the sending and receiving sides. The synchronization circuit is realized by a general four-rule circuit for data transmission.

A constant value is added to the selective C bipolar inverted eclipse image signal by an adder θ (Y). This constant value may be, for example, CY128 as in the constant value generation circuit 3. Thus, 10'
The scrambled image at a level of ~'255' is sent to the receiving side via the transmission line 9.

On the receiving side, the operation is the opposite of that on the sending side. The received signal is converted into a digital signal by an AD converter 10, and a subtracter 11 subtracts a constant value from a constant value generating circuit 12. The constant value of this constant value generating circuit 12 must be the same as the constant value from the constant value generating circuit 7 on the transmitting side. The subtracted value that is the output of the subtracter 11 is sent to the scramble key generator 1.
The key from 3? - Therefore, the polarity is selectively inverted by the polarity inverting circuit 14. Next ζ adder 15 (adds the constant value from the constant value generation circuit 16. This constant value is the same value as the constant value from the constant value generation circuit 3 on the transmitting side. The added signal is l) The A converter 17 converts the signal into an analog signal. This will give you a reproduced image. If there is no noise on the transmission path C2, the transmitting image signal will be correctly received because the receiving side will perform a computation completely inverse to the computation on the transmitting side.

In the above-described embodiment of the present invention, since the sample values of the curved analog signal are transmitted, the transmission band is narrower than that of the digital system 3, and there are advantages in that the frequency resources can be used effectively and the channel cost is low.

General (The C unit that transmits data correctly is the DA converter 8.
For example, the characteristics of the overall transmission path from the A/D converter 10 to the A/D converter 10 can be expressed as a squared cosine shape that satisfies Nyquist's first criterion, as shown in the literature (data transmission Pennett, Co-authored by Davey, Translated by Shogo Supervised). All you have to do is set it as a characteristic and sample it at the correct sample phase.

Even if noise is added to the transmission path, the scrambling method maintains the analog signal shape, so the noise does not increase. For example, when the level a is input as shown in FIG.
The output is '±(a-128)'.

The output of the D/A converter 8 is 1128±(a-128)'=
'a'or'256-8'. Accordingly, the output of the subtracter 11 on the receiving side is 'a-128' or '128-
a', and the output of the polarity inversion circuit 14 is 'a-128'.
becomes. Then, the output of the adder 15 becomes a.

Here, when a = O, the output of the D/A converter 8 is '25
6' and overflow may occur, but in this case, even if it is set to '255', there is almost no deterioration in image quality, so there is no problem.

The level on the transmission path is a or '256-8',
Since the input level (2) changes linearly, the noise is linearly added even when the noise is superimposed on C2, and the reproduced image signal is also linearly added. In other words, there is no breakdown due to noise.However, there is an effect of a limiter. .

[Other embodiments of the invention] In the embodiments described above, AD conversion and scrambling processing are performed.
The image is A-converted and sent out, subjected to human conversion, descrambled, and DA-converted to obtain a reproduced image. On the other hand, even if part or all of the addition/subtraction of a constant value is performed using analog processing (-), the analog circuit will increase in size, but the same effect with no damage due to the strength of scrambling or noise (2) can be obtained.

The effect is the same even if other image processing circuits such as a two-image filter are inserted between the AD conversion converter and the subtracter 2 instead of scrambling the reimaged signal itself.

Similarly C: Even if other data transmission processing circuits such as filters or synchronization signal multiplexing circuits are inserted between the adder 6 and the D/person conversion 1sp8, the effect is the same.

Furthermore, the subtraction, polarity inversion, and addition may be collectively performed by directly calculating the level of 1a1 or '256-1' and switching by using the switch from control C2 to 20 of the scramble key.

Another embodiment of this transmitter is shown in Figure 6C.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, Fig. 2 shows a conventional example, Fig. 3 shows another conventional example, Fig. 4 shows a scramble circuit, and Fig. 5 shows a dynamic FIG. 6, an explanatory diagram of the range, is a diagram showing another embodiment. 1. lO...A/D converter 8.17...D/human converter 3.7.12.16...constant value generation circuit 4.13...
・Scramble key generator 5.14... Polarity reversal circuit agent Patent attorney Noriyuki Chika (and 1 other person) No. 1
Figure 2 Figure 3 Figure 4 ■■■ ■O@■ Figure 5 Figure 6

Claims (1)

[Claims] (1) Sample the image signal, convert it from analog to digital, subtract a certain value, invert or non-invert the polarity according to the scramble key, add a certain value, convert it from digital to analog, transmit it, and sample the received signal. An image signal scramble transmission method characterized by performing analog-to-digital conversion, subtracting a constant value, inverting or non-inverting the polarity according to a scramble key, adding a constant value, performing digital-to-analog conversion, and reproducing the original image signal.