JP2010021931A - Video image transmitter and video image receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mechanism capable of transmitting data securely while reducing an increase in data amount due to encryption in transmitting video images with a high bit rate over a network. <P>SOLUTION: A video image transmitter includes a scale-down image generation means (103) to generate a scale-down image from an original image input, an encryption means (111) that encrypts the scale-down image to generate encrypted data, a difference determination means (105) to determine differential data between the original image and scale-down image, an image compression means (106) that compresses the differential data to generate compressed data, and a transmission means (113) to transmit the encrypted data and compressed data to the outside. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a video transmission / reception apparatus that transmits and receives video safely and at high speed.

  Conventionally, video and audio are generally digitized and transmitted / stored. Since information such as video and audio has a very large amount of information as it is as the original information, it is often transmitted or stored as an encoded bit stream after being compressed (encoded) using an information compression technique. In order to correctly reproduce the video information compressed and transmitted or stored in such a manner, it is necessary to employ a common image encoding method on the encoding side and the reproduction side. For this reason, systems such as Motion-JPEG2000 and MPEG have already been established as international standards for image coding systems.

  In recent years, with the development of networks, it has become possible to transmit video content with a high bit rate that could not be transmitted due to the time taken over the network. As a result, there are increasing opportunities to transmit highly confidential images such as unpublished images, pre-edited images, and videos that have just been shot over a network. The eavesdropping of this highly confidential video on the network leads to a serious loss for the producer.

  It is conceivable to install a dedicated line as a method for preventing eavesdropping. However, since the dedicated line is expensive to introduce and run, VPN is a service that can use the public line as if it were a dedicated line. (Virtual Private Network) may be used. VPN is a technology for performing communication while encrypting communication contents using IPsec (Security Architecture for Internet Protocol), which is a standard for performing encrypted communication on the Internet, and suppressing tampering and wiretapping of communication data. .

There is a method disclosed in Patent Document 1 as an encryption method specialized for video, not a method for encrypting all data flowing through a network like VPN. Patent Document 1 encodes a target image independently for each object by MPEG4 Content-based coding, performs an encryption process only on an encoded bitstream related to a specific object in the image, and generates an encrypted bit. A method of multiplexing and transmitting after converting into a stream is disclosed. This makes it possible to encrypt only important parts.
Japanese Patent Laid-Open No. 10-112851

  Patent Document 1 relates to an invention in which limited information can be obtained by making it possible to reproduce a part of an image transmitted to a recipient who does not have a key for decryption. Therefore, the invention of Patent Document 1 is suitable for transmitting data to an unspecified number of recipients, but is not suitable for transmitting data to a specific recipient safely and at high speed.

  The present invention has been made in view of the above problems, and the object of the present invention is to securely transmit data while suppressing an increase in the amount of data due to encryption when transmitting a video with a high bit rate over a network. It is to provide a mechanism to do.

  A video transmission apparatus according to the present invention includes a reduced image creating unit that generates a reduced image from an input original image, an encryption unit that encrypts the reduced image and generates encrypted data, an original image, and an image of the reduced image Difference means for obtaining the difference data, image compression means for compressing the difference data and generating compressed data, and transmission means for transmitting the encrypted data and the compressed data to the outside.

  A video receiving apparatus according to the present invention comprises: receiving means for receiving encrypted data obtained by encrypting a reduced image created from an original image; and compressed data obtained by compressing difference data between the original image and the reduced image. A first decryption unit that decrypts the compressed data received by the reception unit and obtains differential data; a second decryption unit that decrypts the encrypted data received by the reception unit and obtains a reduced image; and a first decryption unit Image synthesizing means for generating an image having the same size as the original image from the difference data obtained by the means and the reduced image obtained by the second decoding means.

The first program according to the present invention is a program for controlling the control means of the video transmitting apparatus, and causes the control means to execute the following steps.
Generating a reduced image from the input original image and storing it in the first storage means;
Reading the reduced image from the storage means, encrypting it, generating encrypted data and storing it in the second storage means;
Obtaining difference data between the original image and the reduced image,
Compressing difference data, generating compressed data, and storing the compressed data in a third storage means;
A step of transmitting the encrypted data stored in the second storage means and the compressed data stored in the third storage means to the outside.

The second program according to the present invention is a program for controlling the control means of the video receiving apparatus, and causes the control means to execute the following steps.
Receiving encrypted data obtained by encrypting a reduced image created from the original image and compressed data obtained by compressing difference data between the original image and the reduced image, and storing the received data in a storage unit;
Decoding the compressed data stored in the storage means to obtain difference data;
Decrypting the encrypted data received by the storage means to obtain a reduced image;
A step of generating an image having the same size as the original image from the difference data obtained by decoding and the reduced image obtained by the decoding.

  Since the image is separated into a reduced image and differential data, and only the reduced image is encrypted, the amount of encryption processing can be reduced and the amount of data after compression and encryption compared with the case where all areas are encrypted. Can be suppressed. This makes it possible to transmit video data safely and at high speed.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Video compression / encryption device)
FIG. 1 shows the configuration of a video compression / encryption apparatus which is an embodiment of a video transmission apparatus of the present invention. In the following description, an example in which an image of 640 × 480 pixels is compressed and encrypted will be described. Further, the functions of the video compression / encryption apparatus described below can be realized by the CPU executing a predetermined program, that is, by software. Alternatively, it can be realized by hardware.

  The block dividing unit 101 divides the entire area of the input image into blocks of a predetermined size. In this embodiment, the entire area of 640 × 480 pixels as shown in FIG. 2 is divided into blocks of 8 pixels × 8 lines. That is, one video frame of 640 × 480 pixels is divided into 4,800 (= 80 × 60) blocks.

  The average calculator 102 calculates the average value of each element of the block divided by the block divider 101. For example, assume that one block of 8 pixels × 8 lines shown in FIG. 2 is a block 301 shown in FIG. In this case, the average value of the pixel values of the block 301 is (10 + 15 + 20 + 30 +...) / 64 = 25.

  The reduced image creating unit 103 accumulates the average value of the pixel values in one block obtained by the average calculating unit 102 in the reduced image memory 104 and creates a reduced image. One representative value (average value) is stored in the reduced image memory 104 for each block. As a result, a reduced image of 80 × 60 pixels is created for an image of 640 × 480 pixels. As described above, since the average value of the pixel values of the block 301 is 25, the representative value of the pixel values of the block including the first pixel to the eighth pixel and the first line to the eighth line is 25. This is the value of the (1, 1) coordinate of the reduced image.

  The difference calculation unit 105 subtracts the average value obtained by the average calculation unit 102 from the value of each pixel in the block area. In the example of FIG. 3, since the average value of the block 301 is 25, the next block 302 is derived by subtracting the average value (25) from the value of each pixel of the block 301.

  The video compression unit 106 includes a DCT unit 107, a quantization unit 108, and a VLC encoding unit 109. A DCT (Discrete Cosine Transform) unit performs two-dimensional DCT on an 8 × 8 block to obtain an 8 × 8 frequency component. This converted value is called a DCT coefficient. In the example of FIG. 3, two-dimensional DCT is performed on the block 302 to derive the block 303. The value of the (1, 1) coordinate after the two-dimensional DCT is applied is called a DC (Direct Current, direct current) component. The DC component is a component that holds a value corresponding to eight times the average value of pixel values before compression of an 8 × 8 block. Since the difference calculation unit 105 adjusts the average value of the block 302 to be 0, the DC component obtained by the DCT unit 107 is always 0. In this embodiment, an example in which an average value is obtained before DCT is shown. However, a value obtained by reducing the DC component after DCT to 1/8 is used as a representative value of the block, and the DC component is The block 303 may be obtained by clearing 0.

  The quantization unit 108 quantizes each DCT coefficient. Quantization is a process of reducing the precision of values and redividing them into coarser sections. In this embodiment, the block 303 is quantized by dividing the value of each pixel by 5. As shown in FIG. 3, the block 304 is derived by quantizing the block 303.

  A VLC (Variable Length Code) encoding unit 109 encodes the DCT coefficients quantized by the quantization unit 108 by run-length encoding. As shown in FIG. 3, a bit string 305 is derived by encoding the block 304 with VLC. Thus, the image data compressed by passing through the DCT unit 107, the quantization unit 108, and the VLC encoding unit 109 of the video compression unit 106 is stored in the compressed image memory 110.

  The encryption unit 111 encrypts the reduced image created by the reduced image creation unit 103 using a secret key exchanged with the receiving device in advance, and stores the encrypted image in the encrypted image memory 112.

  The transmitting unit 113 first acquires the size of the stored image data from each of the encrypted image memory 112 and the compressed image memory 110 and transmits it. Next, the image data stored in the encrypted image memory 112 is transmitted, and then the image data stored in the compressed image memory 110 is transmitted.

  By repeating the above processing for the number of frames to be transmitted, it is possible to construct a mechanism for encrypting only the reduced image and transmitting the video without encrypting the difference data. As a result, it is possible to provide a mechanism in which data cannot be restored even if eavesdropping while suppressing an increase in the amount of transmission data.

  In this embodiment, the reduced image is encrypted as it is. However, the reduced image may be encrypted after being compressed in advance through the block dividing unit 101 or the video compression unit 106.

(Video decoding device)
Next, a video decryption device (one embodiment of the video reception device of the present invention) that receives and decrypts data transmitted from the video compression / encryption device 10 will be described. FIG. 4 shows the configuration of the video decoding apparatus. Note that the functions of the video decoding apparatus described below can be realized by the CPU executing a predetermined program, that is, by software. Alternatively, it can be realized by hardware.

  The reception unit 401 receives the data transmitted from the transmission unit 113 of the video compression / encryption apparatus 10, and first acquires the size of the reduced image and the compressed image. Next, based on the size, encrypted data and compressed data of the reduced image are acquired from the received data, and are stored in the encrypted image memory 402 and the compressed image memory 405, respectively.

  The decryption unit 403 decrypts the reduced image stored in the encrypted image memory 402 by using the secret key exchanged in advance with the transmitting device, creates an uncompressed reduced image, The reduced image is stored in the reduced image memory 404.

  The video decoding unit 406 includes a VLC decoding unit 407, an inverse quantization unit 408, and an inverse DCT unit 409.

  The VLC decoding unit 407 decodes the data received by the receiving unit 401 into 8 × 8 quantized DC coefficients. A bit string 305 corresponding to one block is extracted from the data stored in the compressed image memory 405 and decoded by VLC to create a block 304 (see FIG. 5).

  The inverse quantization unit 408 performs inverse quantization on the block decoded by VLC. Inverse quantization is a process reverse to the DCT process performed by the quantization unit 108. In the present embodiment, each DCT coefficient is multiplied by 5 to return to the original scale. As illustrated in FIG. 5, the block 501 is derived by multiplying the block 304 decoded by the VLC decoding unit 407 by 5 and performing inverse quantization.

  An inverse DCT (Inverse DCT) unit 409 performs inverse DCT on the block inversely quantized by the inverse quantization unit 408. The inverse DCT is a process that calculates the pixel data from the DCT coefficient by a process reverse to the DCT. As shown in FIG. 5, the block 502 is derived by performing inverse DCT on the block 501 inversely quantized by the inverse quantization unit 408.

  The image composition unit 410 adds the representative value to the area block obtained by the inverse DCT unit 409. The representative value is a pixel value of a pixel corresponding to the block in the reduced image stored in the reduced image memory 404. Since the block 502 is a block corresponding to the first pixel to the eighth pixel and the first line to the eighth line, the representative value of the block 502 is a pixel of the (1, 1) coordinate of the reduced image. Since the pixel value of the (1, 1) coordinate of the reduced image is 25, 25 is added to the value of each element of the block 502 obtained by inverse DCT to derive the block 503 (see FIG. 5).

  The block synthesizing unit 411 is a process of collecting 4,800 (= 80 × 60) 8 × 8 pixels (blocks) to create one uncompressed image. As a result, a 640 × 480 image is finally decoded from the transmitted data.

  In this embodiment, the image composition unit 410 is performed after the inverse DCT process is completed. However, after the DC component of the block 501 before the inverse DCT process is changed to the representative value 200 (= 25 × 8), the inverse DCT is performed. Even if processing is performed, the same result can be obtained.

  In addition, although the block size of the present embodiment is 8 × 8, another size such as 4 × 4 may be used. In this embodiment, both the block size and the range for obtaining the average value are matched with 8 × 8, but the range for obtaining the average value may be different from the block size, such as 16 × 16.

  The video compression unit 106 of the present embodiment has been described on the assumption that DCT, quantization, and VLC are performed, but the present invention can also be applied to other compression methods. Further, although the secret key method is adopted as the encryption method of the present embodiment, the present invention can also be applied to other encryption methods such as a public key method.

  The present invention is useful for a video transmission / reception apparatus that transmits and receives video safely and at high speed.

The block diagram of the video compression encryption apparatus in embodiment of this invention Figure showing an example of block extraction Diagram showing how data is compressed Block diagram of video decoding apparatus in an embodiment of the present invention Diagram showing how data is decrypted

Explanation of symbols

10 Video compression / encryption device (video transmission device)
40 Video decoding device (video receiving device)
101 Block division unit 102 Average calculation unit 103 Reduced image creation unit 104 Reduced image memory 105 Difference calculation unit 106 Video compression unit 107 DCT unit 108 Quantization unit 109 VLC multiplexing unit 110 Compressed image memory 111 Encryption unit 112 Encrypted image memory 113 Read unit 114 Transmitter 301 8 × 8 original image data 302 8 × 8 difference data 303 DCT coefficient 304 Quantized data 305 Compressed bit string 401 Receiving unit 402 Encrypted image memory 403 Decryption unit 404 Reduced image memory 405 Compression Image memory 406 Video decoding unit 407 VLC decoding unit 408 Inverse quantization unit 409 Inverse DCT unit 410 Image composition unit 411 Block composition unit

Claims (4)

Reduced image creation means for generating a reduced image from the input original image;
Encryption means for encrypting the reduced image and generating encrypted data;
Difference means for obtaining difference data between the original image and the reduced image;
Image compression means for compressing the difference data and generating compressed data;
A video transmission apparatus comprising: transmission means for transmitting the encrypted data and the compressed data to the outside. Receiving means for receiving encrypted data obtained by encrypting a reduced image created from an original image, and compressed data obtained by compressing difference data between the original image and the reduced image;
First decoding means for decoding the compressed data received by the receiving means to obtain difference data;
Second decryption means for decrypting the encrypted data received by the reception means to obtain a reduced image;
The image processing apparatus includes: difference data obtained by the first decoding means; and image composition means for generating an image having the same size as the original image from the reduced image obtained by the second decoding means. Video receiver. A program for controlling the control means of the video transmission device,
In the control means,
Generating a reduced image from the input original image and storing it in the first storage means;
Reading and encrypting the reduced image from the storage means, generating encrypted data and storing it in the second storage means;
Obtaining difference data between the original image and the reduced image; and
Compressing the difference data, generating compressed data, and storing the compressed data in a third storage means;
Transmitting the encrypted data stored in the second storage means and the compressed data stored in the third storage means to the outside,
A program characterized by that. A program for controlling the control means of the video receiving device,
In the control means,
Receiving encrypted data obtained by encrypting a reduced image created from an original image, and compressed data obtained by compressing difference data between the original image and the reduced image, and storing the received data in a storage unit;
Decrypting the compressed data stored in the storage means to obtain difference data;
Decrypting the encrypted data received by the storage means to obtain a reduced image;
Causing the difference data obtained by the decoding and generating an image having the same size as the original image from the reduced image obtained by the decoding;
A program characterized by that.

Images