Image analysis – Image compression or coding – Interframe coding
Reexamination Certificate
1997-12-09
2001-09-04
Au, Amelia M. (Department: 2623)
Image analysis
Image compression or coding
Interframe coding
C375S240240, C375S240120, C348S412100
Reexamination Certificate
active
06285791
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to a data transmission method, and more particularly to a method for transmitting video images in a data communication network.
2. Description of Related Art
In the prior art, several methods for the transmission of video images in a data communication network are known. A feature typical of these methods is that the image is compressed in some way before transmission to allow faster transmission. Among the prior-art compression methods are, e.g., MPEG (Moving Pictures Experts Group), and H.261 and H.263 standardized by ITU (International Telecommunication Union, ITU).
The prior-art compression methods are characterized in that, instead of transmitting complete frames, only the differences between successive frames are transmitted. Moreover, predictive coding is used to reduce temporal redundancy, and modification coding to reduce spatial redundancy.
A problem with the prior-art methods is that they apply compression to entire frames and transmit all differences between successive frames. Consequently, the amount of data to be transmitted remains too high for the needs of narrow-band data communication networks. For example, if an MPEG-compressed video image with a resolution of 388*288 is transmitted over a GSM network, the transmission of a single frame may take as long as 15 seconds.
It can be seen then that there is a need for a method for processing a video image so that the image can be readily transmitted even in a narrow-band data communication network, such as a GSM network.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a data transmission method.
The present invention solves the above-described problems by providing a method for processing a video image so that the image can be readily transmitted even in a narrow-band data communication network, such as a GSM network.
In the method of the present invention for the transmission of video images over a data communication network, the video image is encoded at the sending end, transmitted, and decoded at the receiving end. The equipment at the sending end comprises a reference memory, in which the first frame of the video image is stored. Next, the first frame is compressed and transmitted. At the receiving end, the frame is stored in an image memory. The first frame stored in the reference memory and the next frame in sequence are divided into blocks. Mutually corresponding blocks of the frames are compared with each other to determine a block difference. If the block difference exceeds a specified threshold, then the difference between the blocks is compressed and transmitted. In addition, the block is stored in the reference memory. At the receiving end, the difference is integrated into the image to be presented.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the frame is divided into blocks having the size of 8*8 pixels.
Another aspect of the present invention is that the block difference is determined by comparing some of the mutually corresponding pixels contained in blocks corresponding to each other and calculating the number of pixels differing from each other.
Another aspect of the present invention is that the comparison of pixels is performed using some of the bits indicating pixel value.
Another aspect of the present invention is that the comparison of pixels is performed based on the luminance component of the pixels.
Another aspect of the present invention is that a predetermined pat of each frame is transmitted and integrated into the image to be presented.
Another aspect of the present invention is that the compression method used is the JPEG (Joint Photographic Experts Group, JPEG) method.
As compared with prior art, the present invention has the advantage that it allows a considerable reduction in the amount of data to be transmitted, as the frames are divided into blocks and the difference between blocks corresponding to each other is only transmitted if the block difference is sufficiently large. This makes it possible to transmit video images in a narrow-band network as well. The method is particularly well suited for the transmission of video images obtained from a mainly stationary camera, such as a monitoring camera.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.
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patent: 5703966 (1997-12-01), Astle
patent: 5787199 (1998-07-01), Lee
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patent: 5835147 (1998-11-01), Florentin et al.
Altera Law Group LLC
Au Amelia M.
Miller Martin
Telecom Finland Oy
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