JP2000101827A - Digital video coding device and decoding device using watermarking and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a distorted host video image that is transmitted through a severe noise environment by using a current screen. SOLUTION: This coding device includes a discrete wavelet transform section 202 that applies discrete wavelet transformation to a received host video image and provides an output of M×M wavelet coefficients (M is a positive integer), an important coefficient extract section 204 that extracts coefficients with high importance at a prescribed ratio among the M×M wavelet coefficients, a pseudo random number generating section 206 that generates a random number according to rules for encryption codes, and a coefficient replacement/ combination section 208 that obtains replacement position information denoting N×N replacement positions (N is a positive integer smaller than M) by using the random number and replaces/combines M×M wavelet coefficients at the N×N replacement positions denoted by the replacement position information among the M×M wavelet coefficients with the N×N important wavelet coefficients respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image evaluation method using "watermarking" filed by the present applicant.
(Method For Evaluating Image Quality Using Waterma
rking) "U.S. Provisional Patent Application No. 60 / 091,540 (19
98.7.1.). BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital video coding apparatus, a decoding apparatus, and a method using watermarking. The present invention relates to a digital video coding apparatus, a decoding apparatus, and a method thereof, which enable a video coding.

[0002]

2. Description of the Related Art Water marking
Is a technology for transmitting an encrypted image together with a transmitted image for the purpose of displaying security and rights of the image. The receiver receives a video to be transmitted (hereinafter, referred to as a host video) together with an encrypted video (hereinafter, referred to as a signature video) transmitted in secret, and decrypts the signature video by a decryption device. FIG. 1 is a block diagram showing the concept of a digital video codec device for generating a watermarked video and extracting a signature video from the watermarked video.

[0003] Such a conventional digital video codec device performs a discrete cosine transform (DCT) on a host video and a signature video to be transmitted to the host video in secret, at the time of encoding. The DCT coefficient for the video of is extracted. The DCT coefficients are encoded by an encoder. At this time, the DCT coefficient component of the signature image is encrypted by another encryption encoder that performs a control operation for encryption. This makes it possible to transmit the DCT coefficient of the host video and the DCT coefficient of the signature video that has been encrypted and inserted into the DCT coefficient of the host video.
If the coefficient and the DCT coefficient of the signature image encrypted and inserted into the DCT coefficient of the host image are directly subjected to DCT conversion, a watermarked image in which the signature image does not appear but only the host image appears can be obtained.

On the other hand, a signature image watermarked in a host image is restored by decoding with a special decoding device. In the restoration process, DCT coefficients are extracted by performing discrete cosine transform on the watermarked video. Next, the DCT coefficient extracted by performing a discrete cosine transform of the original host video is subtracted from the DCT coefficient of the watermarked video to extract the DCT coefficient component of the encrypted signature video. A decoder decodes the DCT coefficient component. At this time, the encryption decoder performs a control operation for decryption. The DCT coefficients of the signature image decoded by the decoding are subjected to inverse discrete cosine transform again to restore the signature image.

In such a digital video codec using watermarking, if it is determined that the current host video is severely distorted, the decoder corrects the current screen using the previous host video. However, if the current screen is not used to correct the screen and the previous screen is used, there is a problem that the flow of information is not continuous.
Also, when the scene changes suddenly, there is a problem that a screen correction error may occur.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention uses encoding and decoding to correct a distorted host image transmitted from a noisy environment using a current screen. It is an object of the present invention to provide a digital video coding device, a decoding device and a method thereof.

[0007]

In order to achieve the above object, a digital video coding apparatus according to the present invention performs a discrete wavelet transform of a transmitted host video to obtain a predetermined positive integer M. A discrete wavelet transform unit that outputs × M wavelet coefficients;
An important coefficient extraction unit for extracting a coefficient of a predetermined ratio having a high degree of importance among the × M wavelet coefficients, a pseudo-random number generation unit for generating a random number according to a rule corresponding to an encryption code, and using the random number
When a predetermined positive integer smaller than M is N, the replacement position information indicating the replacement position of N × N places is obtained, and the N × N places of the M × M wavelet coefficients indicated in the replacement position information are determined. A coefficient replacement / combination unit that replaces and combines the coefficient on the replacement position with N × N important wavelet coefficients is provided.

The coding apparatus may further comprise an inverse discrete wavelet transform unit for generating a host image synthesized by performing an inverse discrete wavelet transform on the replaced M × M wavelet coefficients; A compression unit that compresses the code and outputs a bit stream. Also,
It is desirable that N is 0.5M or less.

According to another aspect of the present invention, there is provided a digital video coding apparatus comprising: a decompression unit for decompressing a bit stream to restore a host video and a predetermined encryption code; A video quality evaluation unit that evaluates quality and outputs a control signal that is in a first logical state if the restored host video is less than a reference quality, and otherwise is in a second logical state, and controls the first logical state A predetermined positive integer is calculated by performing a discrete wavelet transform of the restored host image in response to the signal.
In doing so, a discrete wavelet transform unit that outputs an M × M wavelet coefficient, a pseudo-random number generation unit that generates a random number according to a rule corresponding to the restored encryption code, and using the random number When a predetermined positive integer smaller than M is N, the separation position information indicating the replacement position of N × N places is obtained, and the N × N positions of the M × M wavelet coefficients indicated in the separation position information are determined. A coefficient separation unit for separating the coefficient on the replacement position,
An inverse discrete wavelet transform unit that outputs a signature image restored by performing an inverse discrete wavelet transform of the wavelet coefficient, an image scale conversion unit that enlarges the scale of the restored signature image to the scale of the host image, and a first logical state Selects the scaled signature image in response to the control signal of
And a video selector for selecting and outputting the restored host video in response to the control signal of the logical state.

In order to achieve the above object, a digital video codec according to the present invention is characterized in that when a predetermined positive integer is set to M by performing discrete wavelet transform on a transmitted host video, an M × M wavelet coefficient A first discrete wavelet transform unit that outputs a coefficient, an important coefficient extracting unit that extracts a coefficient of a predetermined ratio having high importance among the M × M wavelet coefficients, and a random number is generated in accordance with a rule corresponding to an encryption code. The first pseudo-random number generation unit to be, when using a predetermined positive integer smaller than M using the random number as N, obtain replacement position information indicating N × N replacement positions, the M × M Coefficient replacement / combination for replacing and combining the coefficients on the N × N replacement positions indicated in the replacement position information with N × N important wavelet coefficients among the wavelet coefficients. If, replaced M
An inverse discrete wavelet transform unit that generates a host video synthesized by performing an inverse discrete wavelet transform of × M wavelet coefficients, a compression unit that compresses the synthesized host video and the encryption code and outputs a bit stream, A decompression unit for decompressing the compressed bit stream to reconstruct the host video and a predetermined encryption code, and evaluating the video quality of the reconstructed host video to determine the first logic if the reconstructed host video is less than the reference quality. State, a video quality evaluation unit that outputs a control signal that otherwise becomes the second logical state, and a predetermined wavelet transform of the restored host video in response to the control signal of the first logical state. When a positive integer is M, a discrete wavelet transform unit that outputs an M × M wavelet coefficient corresponds to the restored encryption code A pseudo-random number generator for generating random numbers in accordance with the law, an integer of predetermined small positive than M by using the random number N
When determining the separation position information indicating the N × N replacement position, coefficient separation for separating the M × M wavelet coefficients on the N × N replacement position of the position indicated in the separation position information coefficient Unit, a second inverse discrete wavelet transform unit that outputs a signature image by performing an inverse discrete wavelet transform of the M × M wavelet coefficient, and a video scale conversion unit that enlarges the scale of the restored signature image to the scale of the host image. And an image selector for selecting the signature image whose scale is enlarged in response to the control signal of the first logic state, and selecting and outputting the restored host image in response to the control signal of the second logic state. It is characterized by including.

Further, the digital video coding method according to the present invention for achieving the above object comprises the following steps: (a) When a predetermined positive integer is set to M by performing discrete wavelet transform on a transmitted host video, M × M Obtaining an M wavelet coefficient; (b) extracting a coefficient of a predetermined ratio having high importance among the M × M wavelet coefficients; and (c) generating a random number according to a rule corresponding to an encryption code. And (d) determining a predetermined positive integer smaller than M using the random number as N, obtaining replacement position information indicating N × N replacement positions, (e) the M × M
Wavelet coefficients indicated in the replacement position information
Replacing the coefficients on the N × N replacement positions with N × N important wavelet coefficients, respectively.

The digital video decoding method according to the present invention for achieving the above object comprises the steps of (a) evaluating the quality of a synthesized host video and determining whether the quality is above a predetermined standard. (B) setting the synthesized host image as the host image when the quality of the host image is determined to be equal to or more than the predetermined reference in the (a) step, and (c) the host image in the (a) step Setting the signature image concealed in the synthesized host image as the host image if the quality of the synthesized image is determined to be less than the predetermined standard.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a digital video coding apparatus, a decoding apparatus, a codec apparatus and a method thereof according to the present invention will be described with reference to the accompanying drawings. FIG. 2 is a block diagram illustrating a structure of a digital video codec device according to an embodiment of the present invention. Also figure
3 and 4 are flowcharts respectively showing the main steps of a digital video coding method and a digital video decoding method according to an embodiment of the present invention embodied in the digital video codec apparatus.

Referring to FIG. 2, the digital video codec according to the present invention includes an encoding unit 20 and a decoding unit 22. The encoding unit 20 includes a discrete wavelet transform unit 202, an important coefficient extraction unit 204, a pseudo random number generation unit 206, a coefficient replacement / combination unit 208, an inverse discrete wavelet transform unit 210, and a compression unit 212. The decoding unit 22 includes a decompression unit 222 and a video quality evaluation unit 2
24, discrete wavelet transform unit 226, pseudo-random number generation unit 228, coefficient separation unit 230, inverse discrete wavelet transform unit 232, video scale conversion unit 234, and video selection unit 236
Is provided.

FIGS. 2 and 3 show the operation of the encoding unit 20.
In other words, the discrete wavelet transform unit 202
Receives a transmitted host image and performs discrete wavelet transform (step 302) to output discrete wavelet coefficients. The discrete wavelet coefficients comprise a square matrix as is well known. In this embodiment, the discrete wavelet coefficient is a predetermined positive integer represented by M
Is assumed to be composed of a matrix of M rows × M columns. The important coefficient extracting unit 204 extracts 25% of the M × M wavelet coefficients having high importance (step 304).

The pseudo-random number generation unit 206 generates a random number according to a rule corresponding to a predetermined encryption code that can be selectively input by a user. The coefficient replacement / combination unit 208 sets N × N replacement positions when a predetermined positive integer smaller than M is set to N using the random number (step 306). The coefficient replacement / combination unit 20
8 is the N × N selected from the M × M wavelet coefficients
The coefficients on the replacement positions are replaced and combined with N × N important wavelet coefficients, respectively (step 308). Where stage 3
In 04, 25% of the M × M wavelet coefficients were selected as the coefficients of high importance, so N was 1/2 of M,
That is, it is set to 0.5M. In consideration of the characteristics of the watermarking, N is preferably 0.5M or less in consideration of the influence on the original host video. The important wavelet coefficients of the host image transmitted by such replacement and combination are arbitrarily distributed as wavelet coefficients of the signature image in the wavelet coefficients of the synthesized host image.

The inverse discrete wavelet transform unit 210 generates a synthesized host image by performing an inverse discrete wavelet transform on the replaced M × M wavelet coefficients (step 310). Since the synthesized host image includes a signature image by watermarking, there is not much difference from the original host image, and the signature image is difficult to recognize with the naked eye. The compression unit 212 compresses the synthesized host image and the encryption code, and outputs a compressed bit stream (step 312). Here, the fact that the encryption code is compressed together means that the separation position is set according to the same rule as the replacement position used at the time of encoding. As described above, the encoding unit 20 pseudo-randomly rearranges the higher importance coefficients among the wavelet coefficients of the transmitted host image into the wavelet coefficients of the host image itself. Therefore, an important part of the host image is watermarked in the host image itself.

The host video watermarked by the encoding unit 20 is decoded by the decoding unit 22. FIG. 2 shows the operation of the decoding unit 22.
Referring to FIG. 4, the decompression unit 222 decompresses the compressed bit stream to restore the host image and the encryption code (step 402). The encryption code is the encoding part 2
This is for determining a generation rule of a pseudo-random number used for replacement and combination of coefficients at 0.
The encryption code in the decoding unit 22 determines a generation rule of a pseudo-random number used for separating coefficients, which will be described later, similarly to the encoding unit 22.

The image quality evaluation unit 224 evaluates the quality of the restored host image and determines whether the quality of the restored host image is higher than a reference (step 42). That is, the video quality evaluation unit 224 outputs a control signal that becomes logical "high" if the quality of the restored host video is lower than the reference quality, and outputs a logical "low" otherwise. The evaluation of the video quality can be performed, for example, by the same method as the distortion evaluation.

The discrete wavelet transform unit 226 performs a discrete wavelet transform of the restored host image in response to a control signal of a logic "high", and sets a predetermined positive integer to M. Output (step 460). Meanwhile, the pseudo-random number generator 228 generates a random number according to the rule corresponding to the restored encryption code (step 462). Since the pseudo-random number generation unit 228 performs the same operation as the pseudo-random number generation unit 206 of the encoding unit 20, a restored encryption code, that is, the same encryption code as the code used in the encoding unit 20 is input. And a random number according to the same rule as that used in the encoding unit 20.

When a predetermined positive integer smaller than M is set to N using the random number, the coefficient separating section 230 uses N × N
A separation position is set (step 464). Further, the coefficient separating unit 230 separates the coefficients on the N × N separation positions among the M × M wavelet coefficients (step 466). Where N
Is determined at the time of replacement and combination of coefficients in the encoding unit 20, and is preferably 0.5M or less. The inverse discrete wavelet transform unit 232 outputs the signature image restored by performing the inverse discrete wavelet transform on the N × N wavelet coefficients (step 468). Since the restored signature image is an image restored by a wavelet coefficient having a higher importance among wavelet coefficients corresponding to the original host image, the restored signature image is an image close to the original host image.

The image scale converter 234 converts the scale of the restored signature image into the scale of the host image (step 470). The signature image whose scale has been converted in this way is set as a host image. Finally,
The image selection unit 236 selects the signature image whose scale is enlarged in response to the control signal of logic "high", and selects and outputs the restored host image in response to the control signal of logic "low".

Accordingly, if the quality of the restored host image is equal to or higher than a predetermined reference, the decoding unit 22 sets the synthesized host image as the host image (step 44) and outputs it.
On the other hand, if the quality of the restored host image is less than the predetermined standard, the signature image concealed in the host image is restored, and the restored signature image is set as the host image (step 46) and output.

[0024]

As described above, according to the digital video codec apparatus and method of the present invention, information for correcting a distorted host video transmitted from a highly noisy environment using a current screen is used. Since the flow is continuous, no screen correction error occurs even when the scene changes suddenly. The encoding unit and the decoding unit of the codec device according to the embodiment of the present invention may be embodied as a digital video coding device and a decoding device, respectively, as needed.

Also, the digital video coding method and the decoding method according to the present invention can be created by a computer-executable program. In addition, the present invention can be embodied as a general-purpose digital computer that operates the program from a medium used in the computer. The medium includes a magnetic recording medium such as a floppy disk and a hard disk, an optical recording medium such as a CD-ROM and a DVD, and a broadcasting medium such as the Internet. Also, such functional programs, codes, and code segments can be easily inferred by programmers in the technical field to which the present invention belongs.

[Brief description of the drawings]

FIG. 1 Generates a watermarked video,
FIG. 3 is a block diagram showing the concept of a digital video codec device for extracting a signature video from the watermarked video.

FIG. 2 is a block diagram illustrating a structure of a digital video codec device according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating main steps of a digital video coding method according to an embodiment of the present invention.

FIG. 4 is a flowchart illustrating main steps of a digital video decoding method according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 20 encoding unit 22 decoding unit 202 discrete wavelet transformation unit 204 important coefficient extraction unit 206 pseudo-random number generation unit 208 coefficient substitution / combination unit 210 inverse discrete wavelet transformation unit 212 compression unit 222 expansion unit 224 video quality evaluation unit 226 discrete wavelet transformation Unit 228 pseudo-random number generation unit 230 coefficient separation unit 232 inverse discrete wavelet transformation unit 234 video scale conversion unit 236 video selection unit

Claims (12)

[Claims] 1. A digital video coding apparatus using watermarking, wherein when a predetermined positive integer is set to M by performing a discrete wavelet transform on a transmitted host video, a discrete wavelet transform for outputting an M × M wavelet coefficient. An important coefficient extraction unit that extracts a coefficient of a predetermined ratio having a high degree of importance among the M × M wavelet coefficients; a pseudo random number generation unit that generates a random number according to a rule corresponding to an encryption code; When using a predetermined positive integer smaller than M as N using N, obtain replacement position information indicating a replacement position of N × N places, N of the M × M wavelet coefficients indicated in the replacement position information × The coefficient at the N replacement positions
A digital video coding apparatus comprising: a coefficient replacement / combination unit that replaces and combines N × N important wavelet coefficients with each other. 2. An inverse discrete wavelet transform unit for generating a host image synthesized by performing an inverse discrete wavelet transform on the replaced M × M wavelet coefficients, and compressing the synthesized host image and the encryption code. The digital video coding apparatus of claim 1, further comprising: a compression unit that outputs a bit stream. 3. The digital video coding apparatus according to claim 1, wherein said N is 0.5M or less. 4. A digital video decoding apparatus for decoding a bitstream coded using watermarking, wherein the decompression unit decompresses the bitstream to recover a host video and a predetermined encryption code. A video quality evaluation unit that outputs a control signal that evaluates the video quality of the restored host video and the restored host video is less than the reference quality and that is in the first logical state, and is otherwise in the second logical state; A discrete wavelet transform unit that outputs an M × M wavelet coefficient when a predetermined positive integer is set to M by performing discrete wavelet transform on the restored host image in response to a control signal in a logical state; Pseudo-random number generation unit that generates a random number according to a rule corresponding to the generated encryption code When the predetermined positive integer smaller than M is set to N using the random number, separation position information indicating a replacement position of N × N places is obtained, and the separation position information among the M × M wavelet coefficients is determined. A coefficient separation unit that separates the coefficients on the N × N replacement positions shown, and an inverse discrete wavelet transform unit that outputs a signature image restored by performing an inverse discrete wavelet transform on the M × M wavelet coefficients, A video scale conversion unit for expanding the scale of the restored signature image to the scale of the host image; and selecting the scaled signature image in response to the control signal of the first logic state, and selecting the control signal of the second logic state. And a video selector for selecting and outputting the restored host video in response to the video signal. 5. The digital video coding apparatus according to claim 4, wherein said N is 0.5M or less. 6. A digital video codec apparatus using watermarking, wherein a first discrete integer for outputting a M × M wavelet coefficient when a predetermined positive integer is M by performing a discrete wavelet transform on a transmitted host video. A wavelet transform unit, an important coefficient extracting unit that extracts a coefficient of a predetermined ratio having high importance among the M × M wavelet coefficients, and a first pseudo-random number that generates a random number according to a rule corresponding to an encryption code When a predetermined positive integer smaller than M is set to N using the random number, N is used to obtain replacement position information indicating a replacement position of N × N places, and the replacement is performed among the M × M wavelet coefficients. The coefficients on the N × N replacement positions indicated in the position information
A coefficient replacement / combination unit that replaces and combines each with N × N important wavelet coefficients, and an inverse discrete wavelet transform unit that generates a host video synthesized by performing an inverse discrete wavelet transform on the replaced M × M wavelet coefficients A compression unit that compresses the synthesized host video and the encryption code and outputs a bit stream; a decompression unit that expands the compressed bit stream to recover the host video and a predetermined encryption code; A video quality evaluation unit that evaluates the video quality of the restored host video and outputs a control signal that is in the first logical state if the restored host video is less than the reference quality, and otherwise is in the second logical state; 1 When a predetermined positive integer is set to M by subjecting the restored host image to discrete wavelet transform in response to a control signal of a logical state, A discrete wavelet transformer that outputs a bullet coefficient, a pseudo-random number generator that generates a random number according to a rule corresponding to the restored encryption code, and a predetermined positive smaller than M using the random number. When an integer is N, the separation position information indicating the N × N replacement positions is obtained, and the coefficients on the N × N replacement positions indicated in the separation position information among the M × M wavelet coefficients are separated. A second inverse discrete wavelet transform unit that outputs a signature image by performing an inverse discrete wavelet transform of the M × M wavelet coefficient, and an image that enlarges the scale of the restored signature image to the scale of the host image. A scale converter, selecting the signature image whose scale is enlarged in response to the control signal of the first logic state, Digital video codec apparatus which comprises a video selection unit for selecting and outputting host image restored in response to a control signal state. 7. A digital video coding method using watermarking, wherein: (a) obtaining a M × M wavelet coefficient when a predetermined positive integer is M by performing discrete wavelet transform on a transmitted host video. (B) extracting a coefficient of a predetermined ratio with high importance among the M × M wavelet coefficients; (c) generating a random number according to a rule corresponding to an encryption code; When the predetermined positive integer smaller than M using the random number is N, a step of obtaining replacement position information indicating a replacement position of N × N places, (e) among the M × M wavelet coefficients Replacing the coefficients on the N × N replacement positions indicated in the replacement position information with N × N important wavelet coefficients, respectively. (F) generating a synthesized host video by performing an inverse discrete wavelet transform on the replaced M × M wavelet coefficients; and (g) compressing the synthesized host video and the encryption code. 8. The digital video coding method according to claim 7, further comprising the step of: 9. The method of claim 7, wherein N is 0.5M or less. 10. A digital video decoding method for decoding a coded bit stream using watermarking, comprising: (a) evaluating the quality of a synthesized host video to determine whether the quality is higher than a predetermined standard; Determining; (b) setting the synthesized host video as the host video when the quality of the host video is determined to be equal to or higher than a predetermined standard in the (a) step; (c) the (a) Setting the signature image concealed in the synthesized host image as the host image if the quality of the host image is determined to be less than the predetermined standard in the step. . 11. The method of claim 10, further comprising restoring a host image synthesized by expanding the bit stream and a predetermined encryption code. 12. The method according to claim 1, wherein the step (c) comprises: obtaining a M × M wavelet coefficient when a predetermined positive integer is M by performing a discrete wavelet transform on the restored host image; Generating a random number in accordance with the rule corresponding to the code, and when a predetermined positive integer smaller than M is set to N using the random number, separation position information indicating a replacement position of N × N places is obtained. Obtaining, and separating the coefficients on the N × N replacement positions indicated in the separation position information among the M × M wavelet coefficients, and performing inverse discrete wavelet transform on the M × M wavelet coefficients. Restoring the signature image, converting the scale of the restored signature image to the scale of the host image, and setting the converted signature image as the host image 11. The digital video decoding method according to claim 10, comprising the steps of: