JPH08265725A - Data scramble device - Google Patents

Abstract

PURPOSE: To make unauthorized use hardly performable and also provide and advertising effect to non-subscribers by performing a ciphering process to flag data for indicating the coding type of digital picture data to which a high efficiency compression encoding process is performed. CONSTITUTION: The high efficiency compression encoding process is performed to the picture data inputted to an input terminal 11 on a transmission side and they are converted to the bit streams of MPEG in an encoder 12 and then outputted to a buffer circuit 13 and a header decoder 14. The circuit 13 stores tentatively the data inputted from the encoder 12 and then them to a selector 5. The decoder 14 decodes the input data, takes out the PCT flag of a picture header and outputs it to a ciphering circuit 16. The circuit 16 replaces the contents of the inputted PCT flag of three bits on the basis of a ciphering table and outputs them to the selector 15. The selector 15 replaces the part of the PCT flag of the data obtained from the circuit 13 with the PCT flag outputted from the circuit 16 and performs output from an output terminal 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression system for compressing digital image data using a high-efficiency compression coding technique, and more particularly to a data scrambler for scrambling the compressed digital image data. Regarding the improvement of the device.

[0002]

2. Description of the Related Art As is well known, an MPEG (Moving Picture Image Coding Expe) is used as an international standard method for performing highly efficient compression coding processing on digitized image data.
rts Group). This MPEG is a DCT (Discreat Cosine Transfor) which is one of orthogonal transform techniques for transforming digital image data from a spatial coordinate system to a frequency coordinate system.
m) is a data compression method that combines motion compensation prediction processing and DCT processing is used to reduce the amount of spatial information, and motion compensation prediction processing is used to reduce the amount of temporal information.

The digital image data compressed by combining the DCT process and the motion compensation prediction process is
By performing the variable-length coding process by Huffman coding, which is one of the entropy coding, the code amount can be further reduced.

By the way, when the digital image data which has been subjected to the high-efficiency compression coding processing as described above is transmitted or recorded on a recording medium, in order to protect the copyright and prevent illegal copying, etc. It is considered to perform data scrambling processing. That is, only a person who pays a predetermined price in advance and obtains a means for canceling the scramble process can correctly reproduce the digital image data transmitted or recorded on the recording medium. There is.

In this case, in MPEG, a scramble flag is prepared in the header part of the transmission bit stream, and the receiving side detects whether or not the scramble process is performed by detecting the state of this flag. Deciding. The receiving side, which has not acquired the scramble processing canceling means, does not perform the decoding processing for reproduction when the flag determines that the scramble processing has been performed.

However, in MPEG, the flag indicating whether or not the scramble processing is performed has only 2 bits, and the insertion position is fixed, so that the contents of the flag can be easily rewritten illegally. The problem arises that On the other hand, the receiving side, which has not acquired the means for canceling the scramble process, cannot perform the decoding process at all, so that, for example, CATV (Cable
When used in a subscribed television broadcasting system such as broadcasting, the content of the program is hinted to non-subscribers to some extent to motivate them to view, and it is not possible to obtain the advertising effect for promoting subscription. There is also the inconvenience.

[0007]

As described above, in the conventional data scramble means, the flag indicating whether or not scramble processing is performed is likely to be illegally rewritten, and the advertising effect to non-subscribers is expected. It has the problem of not being able to.

Therefore, the present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide an extremely good data scramble apparatus which is unlikely to be illegally used and is expected to have an advertising effect on non-subscribers. To aim.

[0009]

A data scramble device according to the present invention extracts an encoder for performing a high-efficiency compression encoding process on digital image data and a flag data indicating an encoding type from an output bit stream of the encoder. Extraction means, encryption means for performing encryption processing on the flag data extracted by this extraction means, and flag data output from this encryption means for flag indicating the encoding type in the output bit stream of the encoder. A first replacement means for replacing data is provided.

[0010]

According to the above-described structure, the sending side encrypts the flag data indicating the image coding type and sends the encrypted flag data. Therefore, the receiving side that does not have the decryption means encrypts the flag data. On the basis of the above, since the decoder processing that does not correspond to the coding type of the input image is performed, the scramble processing can be performed so that the non-subscriber can determine the image content to some extent.
Further, if there is no table for decryption, the flag data cannot be rewritten, making it difficult for illegal use.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to describing one embodiment of the present invention, the principle of the present invention will be briefly described. That is, FIG. 3 shows the structure of the MPEG picture header. PCT in this picture header
(Picture Coding Type) is a 3-bit flag indicating the coding type of the image.

Here, in MPEG, there are three types of image coding types. The first is an intra-frame coded image called an I-picture, and the second is an inter-frame code called a P-picture that is predicted from an already-coded temporally previous frame. Image, the third is B
It is an inter-frame coded image called a picture that is predicted from two temporally preceding and following frames.

The 3-bit PCT flag represents an I picture by "001" and a P picture by "010".
, And the B picture is represented by “011”. Therefore, in the present invention, the PCT indicating the coding type of the image is
Scramble processing is performed by exchanging the contents of the flag based on a predetermined encryption table.

Based on the principle described above, one embodiment of the present invention will be described below in detail with reference to the drawings. That is, FIG. 1A shows the configuration of the transmission side, and the digital image data supplied to the input terminal 11 is
The data is supplied to the MPEG encoder 12, subjected to high-efficiency compression encoding processing, converted into an MPEG bit stream, and then supplied to the buffer circuit 13 and the header decoder 14, respectively.

Of these, the buffer circuit 13 is an MPEG
The data obtained from the encoder 12 is temporarily stored and then output to one input end of the selector 15. The header decoder 14 also decodes the header portion of the data obtained from the MPEG encoder 12 to extract the PCT flag of the picture header and outputs it to the encryption circuit 16.

The encryption circuit 16 includes a header decoder 1
2 shows the contents of the 3-bit PCT flag obtained from FIG.
They are exchanged based on the encryption table shown in (a) and output to the other input end of the selector 15. This selector 15 is used for the PCT of the data obtained from the buffer circuit 13.
The flag portion is the PCT output from the encryption circuit 16.
It is output after being replaced with a flag.

That is, from this selector 15, MP
Of the data obtained from the EG encoder 12, the PCT
Only the flags that have been replaced by the encryption table are output. Then, the output data of the selector 15 is taken out through the output terminal 17, and is supplied to a transmission path (not shown) or recorded on a recording medium.

Next, FIG. 1 (b) shows the structure of the receiving side. An MPEG bit stream in which only the PCT flag obtained from the output terminal 17 is encrypted is input to the input terminal 18. Is being supplied. This input terminal 18
The data supplied to is supplied to the buffer circuit 19 and the header decoder 20, respectively. Of these, the buffer circuit 19 temporarily stores the data supplied to the input terminal 18, and then outputs the data to one input terminal of the selector 21.

Further, the header decoder 20 extracts the PCT flag of the picture header by decoding the header portion of the data supplied to the input terminal 18, and outputs it to the decryption circuit 22. The decryption circuit 22 replaces the content of the 3-bit PCT flag obtained from the header decoder 20 with the original state based on the decryption table shown in FIG. 2B, and outputs it to the other input end of the selector 21. are doing. This selector 21 replaces the PCT flag portion of the data obtained from the buffer circuit 19 with the PCT flag output from the decryption circuit 22 and outputs the result.

That is, from the selector 21, the PCT flag of the data supplied to the input terminal 18 is replaced by the original state by the decryption table, that is, the output data of the MPEG encoder 12 is obtained. Become. Then, the output data of the selector 21 is supplied to the MPEG decoder 23 and subjected to decompression / decoding processing reverse to that of the MPEG encoder 12, whereby the original digital image data is restored, and the output terminal 24
It is taken out from and is used for image display.

In order to prevent falsification and forgery, the decryption circuit 22 is provided from the transmitting side, that is, the program provider side.
ICs in advance for authorized subscribers who pay the fee
(Integrated circuit) It is sent in the form of a card. For this reason, a legitimate subscriber installs the decryption circuit 22, which is an IC card, which has been sent in advance prior to the broadcast of the program, in his or her receiving device. As a result, the MPEG decoder 23
Can perform decompression decoding processing based on the correct PCT flag, and can correctly restore the image.

Since the non-subscriber does not have the decryption circuit 22, the output data of the buffer circuit 19, that is, P
The data in which the CT flag remains encrypted is supplied to the MPEG decoder 23, and the decompression decoding process is performed. In this case, the MPEG decoder 23 performs decoding processing that does not correspond to the coding type of the input image, such as performing decompression decoding processing that corresponds to a B picture even if an I picture is input. However, it is possible to determine the image content of the entire restored image.

Therefore, according to the configuration of the above embodiment, the transmitting side exchanges the PCT flag indicating the image coding type for transmission, and the receiving side which does not have the decryption means uses the exchanged PCT flag. On the basis of this, since the decoder processing that does not correspond to the coding type of the input image is performed, the scramble processing can be performed so that the non-subscriber can determine the image content to some extent. If there is no decryption table, PC
Since the T flag cannot be rewritten, fraud can be prevented. The present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the scope of the invention.

[0024]

As described above in detail, according to the present invention,
It is possible to provide an extremely good data scramble device that is not likely to be illegally used and can be expected to have an advertising effect on non-subscribers.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a diff scrambler according to the present invention.

FIG. 2 is a diagram showing details of an encryption table and a decryption table in the embodiment.

FIG. 3 is a diagram showing an MPEG picture header for explaining the principle of the present invention.

[Explanation of symbols]

11 ... Input terminal, 12 ... MPEG encoder, 13 ... Buffer circuit, 14 ... Header decoder, 15 ... Selector,
16 ... Encryption circuit, 17 ... Output terminal, 18 ... Input terminal,
19 ... Buffer circuit, 20 ... Header decoder, 21 ... Selector, 22 ... Decryption circuit, 23 ... MPEG decoder, 24 ... Output terminal.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04L 9/12 H04N 7/00 A H04N 7/015 7/133 Z 7/30 11/04

Claims (4)

[Claims] 1. A data scramble apparatus, characterized in that it is configured to perform encryption processing on flag data indicating the coding type of digital image data that has been subjected to high efficiency compression coding processing. 2. An encoder for performing high-efficiency compression encoding processing on digital image data, an extraction means for extracting flag data indicating an encoding type from an output bit stream of this encoder, and a flag extracted by this extraction means. An encryption unit for performing an encryption process on the data and a first replacement unit for replacing the flag data output from the encryption unit with the flag data indicating the coding type in the bit stream output from the encoder. A data scrambler characterized by the following. 3. The data scramble device according to claim 1, wherein in the encryption processing, original flag data is replaced with flag data of different coding types. 4. Extracting means for extracting flag data indicating an encoding type from the output bit stream of the exchanging means, deciphering means for deciphering the flag data extracted by the extracting means, and deciphering 3. The data scrambler according to claim 2, further comprising a second replacement means for replacing the flag data decoded by the means with flag data indicating an encoding type in the output bit stream of the extraction means. apparatus.