JPH06303608A - Scrambler - Google Patents

Abstract

(57) [Abstract] [Object] A scrambler for performing signal shuffling in order to limit the reproducer of a digitally encoded signal, and in particular, a scrambler capable of effect control for compressed data including variable length codes. The purpose is to provide. A code detection device 1 detects which information an input bit is, and a control circuit 2 exclusively uses a signal switching device 3 as a code to be scrambled in the case of a coded block pattern signal. Control is performed so as to send a signal to the logical sum device 6 or the cyclic shift device 5, and the random number generator 4 generates a random number of the number required for scrambling.
When the block equal to the number of coded blocks in the block group indicated by the coded block pattern signal is coded by using the cyclic shift device 5 or the exclusive OR device 6, Convert to a coded block pattern signal represented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides signal agitation that limits who can reproduce it by agitating the signal during transmission or storage of digitally encoded signals and by giving decoding procedures only to authorized ones. The present invention relates to a scrambler for performing a scrambler, and more particularly to a scrambler for performing an effect control for controlling the degree of scramble stirring according to the purpose.

[0002]

2. Description of the Related Art As a scrambler for digital signals, a scrambler for audio signals is used in pay satellite broadcasting. FIG. 5 is a block diagram of a conventional scrambler.

In FIG. 5, numeral 11 is a random number generator, and numeral 12
Is an exclusive OR circuit. In the configuration of the conventional example as described above, the input signal is generated by the random number generator 11 according to the scramble key and the exclusive OR circuit 12
The exclusive OR operation is performed in to obtain a random number signal.
At the time of decryption, the random number from the random number generator 11 can be decrypted by performing the exclusive OR operation again on the scramble signal, but the random number generated by the random number generator 11 is determined by the scramble key. Only the person who has the scramble key can decrypt it. Also, random numbers 1 and 0
The degree of signal agitation can be controlled by controlling the generation ratio of.

[0004]

However, in the above-mentioned conventional configuration, when controlling the degree of agitation, the bits are randomly inverted even if the generation ratio of 1 and 0 is controlled. In the case of transmission after being encoded, variable-length coded data may be included and each bit may have a large effect on the entire video, making it difficult to decode the entire signal or degrading the image more than expected. hand,
There was a problem that the degree of stirring could not be finely controlled.

It is an object of the present invention to solve the above problems and to provide a scrambler capable of effect control on a compression-coded signal.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a format having a hierarchical structure of data in which data of a plurality of pixels is put together to form one coding block, and a block group is composed of the plurality of the coding blocks. In the digital video signal coded in, for the digital video signal including a coded block pattern signal indicating whether each block in the block group is coded in each block group, the coding block pattern signal,
The coded block pattern signal is provided with conversion means for converting into a coded block pattern signal representing a case where the number of coded blocks in the block group is equal to the number of coded blocks.

[0007]

According to the present invention, when a normal signal is reproduced by the above-mentioned structure, it is judged whether each block in the block group is coded or not, and the uncoded part is skipped. As a matter of course, in order to convert the coded block pattern signal that functions to reproduce the signal of each block to the correct position in the video into a random value, each block will be reproduced at the wrong position in the image, Effect control that partially deteriorates the reproduced image can be realized.

Further, the coded block pattern signal conversion method is changed so that the number of coded blocks in the block group becomes the same value, thereby matching the number of blocks actually existing in the group block. So
Since it does not affect the reproduction of the data after that, the appearance can be controlled by making the contents understandable to some extent, rather than making the contents invisible at all.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a scrambler according to an embodiment of the present invention.

In FIG. 1, 1 is a code detecting device for reading which bit of which signal the currently input signal indicates, and 2 is the current code of the input signal from the detection result of the code detecting device 1. A controller for deciding whether or not to scramble and controlling on / off of scrambling,
Is a signal switching device for switching the processing performed by the input signal according to the signal from the control device 2, 4 is a random number generating device, and 5 is a cyclic shift for cyclically shifting the transmitted signal according to the signal from the random number generating device. The device, 6 is an exclusive OR circuit.

The operation of the scrambler of the present embodiment having the above configuration will be described. First, the input signal is a video signal compliant with the MPEG (Moving Picture Expert Group: Joint Working Group of International Standardization Organization ISO and International Electrotechnical Commission IEC) standard. MPEG
Regarding the standard, for example, "Motion Picture Coding Technology for Storage Media", Television Society Journal, Vol.45, No.7, pp807-812 (19)
91), and is currently working on standardization of higher image quality encoding, including the draft of ISO-IEC / JCT1 / SC29 / WG11 NO328.

An outline of a video signal based on the MPEG standard will be described below with reference to FIG. As shown in FIG.
The data structure is composed of a sequence layer (layer), and the sequence layer represents one moving image sequence, and the header part includes a sequence head identification signal which serves as a start code, various parameters and data, and one or more. GOP (Group of pictur
e)), and includes encoded data of a picture (image) group.

Further, the GOP layer is composed of frames of arbitrary length, and the head identification signal (Start-code) of the GOP which serves as a start code of the GOP layer, encoded data of one or more pictures, etc. Is included. Next, the above-mentioned picture layer includes a picture start identification signal (Start-code) that functions as a start code of the picture, encoded data of one or more slices, and the like. Slice start identification signal that contains the information of one or more macroblocks, can include any macroblock, and serves as the start code for the slice layer
(Start-code) and encoded data of one or more slices are included.

Further, the macroblock will be described.
This macroblock is a block of luminance 16 × 16 pixels and a color difference corresponding to it, and has luminance (Y) and color difference (C
b, Cr), each block is composed of several smaller basic coding units of 8 × 8 pixels. Figure 3
Shows the structure of this macroblock. The number of each block in the macroblock is as shown in FIG.
If the processed signal is a 4: 2: 0 signal, it has a maximum of 6 blocks with 4 luminances and 1 color difference, and the processed signal is 4: 2: 2. In the case of a signal, there are a total of eight with four luminances and two color differences.
In the case of 4: 4: 4, there are 4 luminances and 4 color differences.
It has a maximum of 12 blocks in total.

The data of each block are arranged in the order of the numbers assigned to each block in FIG. 3, and when the prediction coding is performed and the value obtained by quantizing the prediction error is all 0s. When it is not necessary to send data, the block is skipped and a macroblock is constructed. That is, when the second block is skipped with a 4: 2: 1 signal, the blocks in the macroblock are macroblocks in which five blocks 1, 3, 4, 5, 6 are arranged in order. Make up.

When the nth block is encoded, it is represented by bn = 1, and when it is not encoded, bn = 0.
It is represented by (n = 1,2, ...), and the coding block pattern in the macro block is "coded block pattern" (hereinafter, cbp), and in the case of a 4: 2: 0 signal, cbp = (b1 , b2, b
3, b4, b5, b6) ₂ represented by a 6-bit binary number, which is variable length encoded from 3 bits to 9 bits according to the frequency of appearance.

For 4: 2: 2, cbp = (b1, b2,
b3, b4, b5, b6, b7, b8) ₂ is represented by an 8-bit binary number and is used as it is in the case of 4: 4: 4.
cbp = (b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b
11, b12) ₂ is expressed as a 12-bit binary number and is used as a code as it is, and this signal exists for each macroblock.

Using the bit string having the above structure as an input signal, the code detection device 1 is provided with a code book for reproducing each code for reading the contents of all the data of the input signal, and is currently input. Which information is contained in the existing bit is transmitted to the control circuit 2. In the control circuit 2, when the cbp signal is detected, the process is selected as the code to be scrambled according to the signal from the code detection device 1, the signal switching device 3 is controlled, and the scrambling is required. A control signal that causes the random number generator 4 to output a random number of a random number is sent. The control method will be described below.

In the control device 2, when the code which is not normally scrambled is detected, the signal switching device 3 sends a signal for connecting the input signal to the terminal c, and the input signal is not processed and the output signal is not processed. Try to be.

The "coded block pattern" in the input signal
When the "rn" signal is detected, the connection of the signal switching device 3 is switched as a code to be scrambled, and a random number generation command is sent to the random number generation device 4.

First, when the signal being processed is 4: 2: 0, the control signal is sent in the signal switching device 3 so that the input signal and the terminal a are connected. Then, the code length information and a 1-bit random number generation command are sent to the random number generator 4. The random number generator 4 outputs a 1-bit random number to the exclusive OR circuit 6 based on the scramble key, and adds this to the final bit of the code.

However, "111", "01011", "01010", "0100"
In the case of 1 "and" 01000 ", the input signal is not scrambled and is connected to the terminal c in the signal switching device 3. Fig. 4 is used in the case of 4: 2: 0 signal
This is the cbp codebook. From FIG. 4, except for the case where the code is "111", all codes also have the code obtained by inverting the last bit in the codebook. In addition, the number of 1s in the binary display of the cbp value indicated by the code at that time is also the same except for the cases of "01011", "01010", "01001", and "01000". Therefore, the input signal is converted into a signal having the same code length, and when reproducing the converted signal, the decoded position is reproduced erroneously. For example, when the code of cbp is "1101" and is converted to "1100", the signal of the block at the 4th position is reproduced as the block at the 3rd position.

Next, in the case of a signal of 4: 2: 2 or 4: 4: 4, the control signal is sent from the control circuit 2 so that the input signal is connected to the terminal b in the signal switching device 3. Further, a 4-bit random number generation command is sent to the random number generator 4. The random number generator 4 generates a 4-bit random number based on the scramble key and transmits it to the cyclic shift circuit 5. The cyclic shift device 5 cyclically shifts and outputs the cbp code by the number of times indicated by 4 bits of the signal from the random number generator. Therefore, the code length is the same as in the case of 4: 2: 0, and the position of each block is converted to an incorrect position. The signal generated as described above is fitted into the original position of the code of "cbp" and becomes the output signal.

As described above, according to this embodiment, 4: 2:
In the case of a 0 signal, the code length of "01011", "01010", "01001", "01000" is not processed as an exception, and the code length is simplified by adding a random number to the last bit of the remaining code. It is possible to realize a process for converting into a code in which the number of blocks included in the code does not change.

Also, in the case of a 4: 4: 2 or 4: 4: 4 signal, since the cyclic shift processing is performed, the number of 1's in the code does not change, and it can be realized by a very simple processing, which is practical. high. Also, since the MPEG standard coding method uses predictive coding, the reproduced signal may not only move the position of the block, but may also add an incorrect prediction error signal to the predicted value. And a more effective stirring effect than simply replacing blocks.

In the present embodiment, the conversion process is the process of inverting the final bit for the 4: 4: 0 signal, but the condition that the code length is not changed and the number of blocks is not changed is set. Other conversion means may be used as long as the conversion is satisfied. Further, even in the case of 4: 2: 2 and 4: 4: 4 signals, the conversion processing is cyclic shift, but other conversion means may be used as long as the conversion does not change the number of 1's in the code. Good. Further, the input signal is also a video signal conforming to MPEG in the present embodiment, but the same applies to other signals as long as the signal includes a code corresponding to the coding block pattern. It goes without saying that it can be realized with such a way of thinking.

[0027]

As described above, according to the present invention,
By converting a coded block pattern signal into a coded block pattern signal that is represented when a block equal to the number of coded blocks in the block group indicated by the coded block pattern signal is coded. Providing a scrambler that can control the appearance of a block without making it invisible at all so that the decoding position of the block is reproduced at the wrong position while other data can be read. Can
Its practical effect is great.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a scrambling device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a digital video signal based on the MPEG standard.

FIG. 3 is an explanatory diagram showing a configuration of blocks in a macro block in a digital video signal based on the MPEG standard.

FIG. 4 is an explanatory diagram of a DCT coefficient coding codebook used in the MPEG standard.

FIG. 5 is a block diagram of a conventional scrambler.

[Explanation of symbols]

 1 code detection device 2 control circuit 3 signal switching device 4 random number generation device 5 cyclic shift device 6 exclusive OR device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Ibaraki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A digital video signal coded in a format having a hierarchical structure of data in which data of a plurality of pixels are put together to form one coded block, and a block group is composed of the plurality of coded blocks. so,
For a digital video signal including a coded block pattern signal indicating whether or not each block in the block group is coded in each block group, the coded block pattern signal is converted into a block in the block group indicated by the coded block pattern signal. A scrambler, comprising: a conversion unit for converting into a coded block pattern signal that represents a case in which blocks equal to the number of coded blocks are coded. 2. The video signal is a video signal conforming to the MPEG standard, and the converting means includes "coded block p" in the signal.
For a code that represents "attern," the code represents
"coded block pat" represented by a binary number having a number of 1 which is equal to the number of 1 when the coded block pattern is expressed in binary number
A scrambler comprising a conversion means for converting a code when "tern" is encoded. 3. The signal processed by the conversion means is 4: 2 :.
3. The scrambler according to claim 2, wherein when the video signal is 0, the code expressing the "coded block pattern" is converted into another code having the same code length in the codebook. apparatus. 4. The signal processed by the converting means is 4: 2 :.
If the video signal is 2 or 4: 4: 4, "coded"
3. The scrambler according to claim 2, which is a conversion means for converting into a code word having a number of 1s equal to the number of 1s in the code word of the "block pattern".