KR20060055622A - Mpeg-4 moving picture encoder and decoder having a hash function - Google Patents

Abstract

The present invention inserts the watermark generated based on the use of the hash function into the image information and extracts the inserted watermark to prevent forgery of the image information, as well as the 'U' of the 'I' frame of the image information. The present invention relates to an MPEG-4 video encoder and a decoder to which a hash function is applied to distribute a hash code only to a block and a 'V' block to prevent image degradation.

The present invention for this purpose; An MPEG-4 video encoder having a hash function input unit which generates a watermark by a hash function between the quantization unit and the variable length encoder of a general MPEG-4 video encoder and can be driven only in an 'I' frame;

It is possible to drive only 'I' frame between the inverted variable length coder and the inverse quantizer of a typical MPEG-4 video decoder, and it is possible to determine whether the forgery is by comparing the value extracted from the watermark extracted from the decoding process and the hash. The MPEG-4 video decoder, which is equipped with a hash function comparison unit, is provided in association.

MPEG-4, video encoder and video decoder, hash function, I frame.

Description

MPEG-4 moving picture encoder and decoder having a hash function}

1 is a block diagram showing a typical MPEG-4 encoder and decoder;

2 is a block diagram showing an MPEG-4 video encoder to which a hash function is applied according to a preferred embodiment of the present invention;

3 is a block diagram showing the hash function insertion unit in FIG.

4 is a diagram illustrating an initial value input process of a hash function according to the present invention;

5 is a view showing an embodiment in which a watermark is inserted at a boundary of an I-frame according to the present invention;

6 is a block diagram showing an MPEG-4 video decoder to which a hash function is applied according to a preferred embodiment of the present invention;

FIG. 7 is a block diagram illustrating a hash function comparison unit of FIG. 6.

* Description of the symbols for the main parts of the drawings *

100: hash function insertion unit, 102, 122: hash function engine unit,

104, 124: register, 106: insertion portion,

120: hash function comparison, 126: comparison unit,

130: comparison result section.

The present invention relates to an MPEG-4 video encoder and a decoder to which a hash function is applied. More specifically, the present invention is similar to a conventional hardware structure by applying a hash function which is a function related to authentication of image data. The present invention relates to an MPEG-4 video encoder and a decoder to which a hash function is applied to enable efficient protection and minimization of image quality degradation.

As is well known, as the voice of protection for digital image data increases domestically and internationally, research and development are being actively conducted to prevent illegal distribution or duplication of digital image data. There is an absolute need for a system capable of detecting and verifying digital images when they are forged and modulated.

As a way to protect digital data, it is possible to drive only works that are normally purchased, such as encryption and scrambling, and in recent years, it is not recognized by the human eye or hearing. Watermarking technology has been spotlighted by inserting a predetermined identifier such as a logo or the like to detect when the data is copied or distributed without permission and claim the digital data.

The watermarking technology inserts a watermark, which is a specific identifier capable of claiming copyright, such as copyright information, into multimedia content such as video, image, and text. If the data to which the mark is inserted is illegally copied, the owner can identify through the reverse processing process that the illegally copied data is his or her copyrighted work.

Meanwhile, MPEG-4 is a standard for next-generation multimedia that is proposed and standardized by ISO / IEC-based SG29 WG11. This means that all media used in the existing multimedia communication can be viewed as a single object. Since each object can be processed independently, it is possible to choose the compression method that has the maximum efficiency for each object after recording each object independently, and also includes information about the relationship between objects and the user's access to the objects. Restrict access to copyrights for content.

As such, the structure of a video encoder and a decoder to which the MPEG-4 technology is generally applied is shown in FIG. 1.

Referring to FIG. 1, an MPEG-4 encoder and a decoder include an encoding module and a prediction module. First, the encoding module includes one of an intra-frame or an inter-frame. A buffer 10 associated with the mode decision unit 2, the discrete cosine transform unit (DCT unit) 4, the quantization unit 6, the variable length encoding unit 8, and the adaptive quantization unit 9 for determining the mode selection. The prediction module includes a motion prediction unit 12, a motion compensation unit 14, a buffer 16 for receiving a bitstream signal output from the buffer 10, and an inverse variable length encoding unit 18. , An inverse quantization unit 20, an inverse DCT unit 22, and an adder 24 is configured.

The construction and operation of the MPEG-4 encoder and decoder consisting of the above elements are well known in the art, and a detailed description thereof will be omitted.

The encoding scheme in the MPEG-4 encoder / decoder is a combination of a coding scheme in the spatial domain and a coding scheme in the time domain, as provided by the mode determination unit 2.

The coding scheme in the spatial domain is a method in which the original image is passed through the DCT unit 4 and the quantization unit 6 and then compressed and transmitted by the variable length encoding unit 8 as a Huffman code. In the coding scheme in the region, the 'I' frame compressed in the spatial domain is reconstructed through the inverse quantization unit 20 and the inverse DCT unit 22 and then compared with the image currently input by the motion predictor 12. A method of predicting motion and encoding a difference (−) signal from an original image by spatially moving the current image by the predicted motion.

Here, the motion prediction method using the encoding method is called 'P' image for forward prediction, and 'B' image for including both forward and backward prediction, and 'P' only when the 'I' image is well reconstructed. The reconstruction of the image and the 'B' image can be performed efficiently. That is, the 'P' image can be expected to be completely reconstructed only when the 'I' image information is present. The 'B' image can be decoded only when there is decoded 'I' image information and 'P' image information used in the encoding process. It is possible.

Accordingly, the MPEG-4 encoder and the decoder can prevent the degradation and degradation of the compression efficiency of the image according to the method of embedding the encryption and the watermark. However, the existing watermark technology uses only watermark data in the spatial domain. In addition, the MPEG-4 coding scheme, which considers the time domain, is not suitable, and at the same time, there is a complicated problem of components in implementing real hardware.

Accordingly, the present invention has been made to solve the above problems, and by applying a hash function related to authentication of digital data without changing the structure of the conventional MPEG-4 encoder and decoder, efficient data with minimal operation An object of the present invention is to provide an MPEG-4 video encoder and a decoder to which a hash function is applied to minimize deterioration of protection and image quality.

MPEG-4 video encoder to which the hash function of the present invention is applied to achieve the above object; In a general MPEG-4 video encoder structure, a hash function input unit capable of generating a watermark by a hash function and driving only in an 'I' frame is separately installed between the quantizer and the variable length coder.

In addition, the MPEG-4 video decoder is applied to the hash function of the present invention for achieving the above object; In the general MPEG-4 video decoder structure, only the 'I' frame can be driven between the inverse length coder and the inverse quantizer. The hash function comparison unit that can be determined is characterized in that it is mounted separately.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

In describing the embodiments of the present invention, the same components as those in the prior art will be described with the same reference numerals.

FIG. 2 is a block diagram showing an MPEG-4 video encoder to which a hash function is applied according to a preferred embodiment of the present invention. FIG. 3 is a block diagram showing a hash function inserting unit shown in FIG.

As shown, the MPEG-4 video coder performs forward discrete cosine (FDCT) 4 for performing discrete cosine transform on input image information, and a quantization unit 6 for quantizing image information output from the FDCT 4. And storing the dequantized image information from the variable length encoding unit 8, the inverse quantization unit 20, and the inverse quantization unit 20 to which the output of the quantized image information is independently applied to a memory (not shown). In order to return the loss of the macroblock of the image information, it is located between the inverse discrete cosine transform unit (inverse DCT) 22, the quantization unit 6 and the variable length encoding unit 8, And a hash function inserting unit 100 for inserting a watermark in the image information in the discrete cosine transformed frequency domain.

The hash function insertion unit 100 is; A hash function engine 102 for using a hash function to insert a watermark in the quantized image information, and a value of the quantization unit 6 to be input in the next 'I' frame from the hash function engine 102. An insertion unit 106 and a hash function engine unit 102 for generating a seed value to be inserted into the slot, and at the same time, a reset value becomes an initial value so that the quantization value of the current 'I' frame is inserted. It consists of a register 104 to temporarily store the initial value generated in the and provided to the insertion unit 106.

The encoding process according to the MPEG-4 video encoder configured as described above will be described.

Prior to explaining the operation of the present invention, the MPEG-4 video system performs discrete cosine conversion by dividing the image information into "8 * 8" block units to improve computational efficiency. The B 'frame or the' P 'frame has a macroblock to which a skid macro block and a motion vector are applied as shown in [Table 1]. The hash function of the present invention is applied to the DC coefficient of the 'I' frame by the spatial domain coding method rather than the 'B' frame.

TABLE 1

[Table 1] compares the number of omitted macroblocks in the GOP (Group of Pictures), which is a set of continuous image information starting with an I-frame, and the number of macroblocks to which motion is applied.

As such, since the DC coefficient of the 'I' frame is used, an initial value for inserting the watermark should be extracted from the 'I' frame, and a hash function is used for the insertion and extraction of the initial value.

The hash function is the most frequently used cryptographically for digital signature, data integrity, and message authentication. In particular, the hash function calculates a hash code of information desired for integrity verification and stores it safely. The integrity of the information can be checked after comparing with the stored hash code value.

As such a hash function, MD-5 (128 bits), SHA-1 (160 bits), HAS160 (160 bits) and the like are applied as a function that receives 512 bits of input and outputs 128 bits or 160 bits.

Next, the process of embedding the watermark in the image information using the hash function as described above will be described.

First, the FDCT (Foward DCT) 4 performs a prior discrete cosine transform on the input image information, and the image information output from the FDCT 4 is quantized by the quantization unit 6 and then the variable length coding unit 8 In addition to being delivered to) it is also delivered to the hash function insertion unit (100).

Then, the hash function engine 102 of the hash function insertion unit 100 receives the quantized information and inserts an initial value to be inserted into the value of the quantization unit 6 to be input in the next 'I' frame. ) The initial value generated by the hash function inserter 100 is transmitted to the inserter 106 via the register 104 and the reset value becomes the initial value. It is inserted as a quantized value of an I 'frame and passed to the variable length coder 8. In other words, a hash code that is a watermark is generated by the hash function insertion unit, and the hash code is combined with quantized image information and then encoded through a variable length encoding process.

In this case, referring to FIG. 4, the initial value of the hash function, that is, the 512-bit input value, is a DC value of each 'Y' block from one of 24 macroblocks, based on the center of the 'I' frame. Four DC values are selected from the first macro block. In FIG. 4, 'A' is a reference position macroblock, and 'B' is a DC value of the 'Y' block.

In addition, referring to FIG. 5 showing an 8 * 8 type 'U' block and a 'V' block, the hash code is distributed to the 'U' block of the 'I' frame and the least significant bit of the AC values of the 'V' block. 4 bits are allocated to each of the 'U' block and the 'V' block of the macro block for the first 20 of the 'I' frames.In this case, by inserting at the boundary of the frame, even if there is a deterioration in image quality, Should be insufficient.

As such, the hash function insertion unit 100 distributes and inserts a hash code into the bits of the DC value of the 'Y' block and the AC value of the 'U' block and the 'V' block, thereby generating a watermark, and generating the watermark. It is inserted into the image information transmitted from the quantization unit 6 and then transferred to the variable length encoding unit 8 to perform the encoding process for the 'I' frame.

On the other hand, after encoding the image information by whitening the above process, a decoding process of extracting the watermark is performed.

FIG. 6 is a block diagram showing an MPEG-4 video decoder to which a hash function is applied according to a preferred embodiment of the present invention. FIG. 7 is a block diagram showing a hash function comparison unit in FIG.

As illustrated, an MPEG-4 decoder for extracting a watermark receives an encoded image information from the variable length encoder 8 of the encoder and inverse VLC (Inverse VLC) for inverting the variable length code. 18) a hash function comparison unit 120 for comparing the watermark extracted by the inverse variable length encoding unit 18 and a value output from the hash function, and the comparison result from the hash function comparison unit 120 to the microprocessor. Comprised of the comparison result unit 130 to notify.

The hash function comparator 120 includes a hash function engine 122, a register 124, and a comparator 126.

Next, the operation of the decoder will be described in connection with the operation of the encoder.

When the image information in which the watermark is inserted by the encoding process is transferred from the variable length encoding unit 8 to the inverse variable length encoding unit 18, the inverse variable length encoding unit 18 is inversely variable from the image information. Through the length encoding process, the quantization value of the 'Y' block is extracted and transmitted to the hash function comparison unit 120.

Then, the hash function engine 122 inputs the extracted quantization value of the 'Y' block to the hash function to extract the initial value inserted by the hash function insertion unit 100, and register 124. Transfer to the comparator 126 through the.

The comparison unit 126 compares the extracted initial value with the watermark extracted in the decoding process, determines whether there is a match, and notifies the microprocessor of the match. Allows you to determine if a forgery exists.

At this time, the initial values extracted from the 'U' block and the 'V' block values shown by the inverse variable length coder 18 coincide with the hash function values generated to perform the comparison operation.

As described above, according to the MPEG-4 video encoder and decoder to which the hash function of the present invention is applied, a watermark for preventing forgery is inserted and extracted into the hardware system structure of the conventional MPEG-4 video encoder and decoder. The structure of the component to be added can be simply added to eliminate the complexity of the overall configuration.

In addition, since the hash code is inserted only in the 'U' block and the 'V' block of the 'I' frame, it is possible to effectively protect data and to prevent image quality deterioration.

On the other hand, the present invention is not limited to the above-described specific preferred embodiments, and various changes can be made by those skilled in the art without departing from the gist of the invention claimed in the claims. will be.

Claims (8)

In the MPEG-4 video encoder based on discrete cosine transform, A forward DCT (FDCT) for performing discrete discrete cosine transform on input image information, a quantization unit for quantizing image information output from the FDCT, a variable length encoder and inverse quantization independently receiving the output of the quantized image information A decoded inverse discrete cosine transform unit for storing dequantized image information from the inverse quantizer in a memory and returning a loss of a macroblock of a frame, and located between the quantization unit and the variable length encoding unit A hash function insertion unit for inserting a watermark in the image information in the cosine transformed frequency domain; The hash function inserting unit is a hash function engine unit for using a hash function to insert a watermark in the quantized image information, and inserted into a value of the quantization unit to be input in a next 'I' frame from the hash function engine unit. An inserter which generates a seed value and at the same time a reset value becomes the initial value so that the quantization value of the current 'I' frame is inserted; and a register which temporarily stores the generated initial value and provides the inserted part to the inserter. MPEG-4 video encoder to which a hash function, characterized in that consisting of. The method of claim 1, The hash function engine inputs a DC value for each 'Y' block from a total of 24 macroblocks based on the center of the 'I' frame among the quantized image information transmitted from the quantization unit. MPEG-4 video encoder with a hash function. The method of claim 2, 4. The MPEG-4 video encoder to which the hash function is applied, wherein four DC values are input from the first macro block among the 24 macro blocks. The method of claim 1, The insertion unit is an MPEG to which a hash function is applied, characterized in that the hash code value is distributed and inserted into the least significant bits of the AC values of the 'U' block and the 'V' block of the 'I' frame among the I, B, and P frames. 4 Video encoder. The method of claim 4, wherein The inserter is an MPEG-4 video encoder to which a hash function is applied, characterized in that four bits are respectively inserted and inserted into the 'U' block and the 'V' block of the first 20 blocks of the 'I' frame. . In the MPEG-4 video decoder for decoding the encrypted video information received from the discrete cosine transform-based MPEG-4 video encoder, The value output from the watermark and the hash function extracted in the decoding process between the inverse variable length coder for receiving the encoded image information from the variable length coder of the encoder and the inverse variable length coder and the inverse quantizer for inverse quantization. MPEG-4 video decoder comprising a hash function comparison unit for comparing the configuration. The method of claim 6, The quantization value of the 'Y' block passed through the inverse variable length coding unit inputted to the hash function comparison unit is input from each of 24 macroblocks of 'Y' blocks based on the center of the 'I' frame, MPEG-4 video decoder, characterized in that four DC values are input from the first macroblock of the 24 macroblocks. The method of claim 6, And a hash function value input to the hash function comparison unit coincides with an initial value extracted from 'U' block and 'V' block values passed through the inverse variable length encoding unit.

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