Method and system for compressing motion image information

Abstract

A method and system are disclosed for compressing motion image information by means of predictive coding with a high compression ratio while maintaining high image quality. An image in each frame is divided into blocks in advance, and each of all blocks is approximated by (replaced with) a single plane defined by three data representing the magnitude of the intensity of the block, the block-to-block gradient of the intensity in the x direction, and the block-to-block gradient of the intensity in the y direction. Furthermore, corresponding pixels are compared with each other in each block consisting of n×m pixels between frames, and differential information is generated-according to the comparison result. Pixels indicated as being not greater than a parameter is treated (deleted) as pixels having no difference between frames. Information compression is performed for pixels indicated as being greater than the parameter.

Description

[0001] This application is a continuation application of Ser. No. 09 / 750,118, now pending.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a method and system for compressing motion image information data by means of predictive coding with a high compression ratio and with high image quality. [0004] 2. Description of the Related Art [0005] In image signal transmission, an image signal is first converted to another signal and then coded by assigning proper codes selected according to the statistical feature of the converted signal. When the image has high redundancy within a frame as is the case with an image including a regular pattern or a plain image, there is a high correlation between adjacent pixels, and thus it is possible to predict, to a certain degree, a pixel value to be coded next from a pixel value which has already been coded. Therefore, if components which could not be predicted are extracted, and the coding is perfor...

AI Technical Summary

Benefits of technology

[0012] According to an aspect of the present invention, to achieve the above object, there is provided a method of compressing motion image information, comprising the steps of: comparing pixels in a frame with corresponding pixels in a spatially or temporally adjacent frame and generating differential information in accordance with the comparison result; generating and storing a 1-bit bit map indicating whether the differential information is greater or not greater than a given parameter; and compressing information of a pixel indicated as being greater than the parameter thereby reducing redundant information between frames, the method being characterized in that: an image in each frame is divided into blocks in advance, and each of all blocks is approximated by (replaced with) a single plane defined by three data representing the magnitude of a pixel value in the block, the block-to-block gradient of the pixel value in an x direction, and the block-to-block gradient of the pixel value in a y direction.

[0014] According to still another aspect of the present invention, to achieve the above object, there is provided a method of compressing image information, by means of comparing spatially or temporally adjacent pixels to each other and generating differential information so as to reduce redundant information between frames, the method including the steps of: comparing corresponding pixels to each other between frames and generating and storing a 1-bit bit map indicating whether the absolute value of the difference thereof is greater or not greater than a given parameter; and compressing information of a pixel indicated as being greater than the parameter thereby reducing redundant information between frames, the method being characterized in that: an image in each frame is divided into blocks in advance, and each of all blocks is approximated by (replaced with) a single plane defined by three data representing the magnitude of a pixel value in the block, the block-to-block gradient of the pixel value in an x direction, and the block-to-block gradient of the pixel value in a y direction.

[0023] According to still another aspect of the present invention, to achieve the above object, there is provided a method of compressing motion image information, by means of comparing spatially or temporally adjacent pixels to each other and outputting differential information thereby reducing redundant information between frames, the method including the steps of: comparing corresponding pixels to each other in each block consisting of n×m pixels (n and m are integers equal to or greater than 2) between frames and generating and storing a 1-bit bit map indicating whether the absolute value of the difference thereof is greater or not greater than a given parameter; and compressing information of a pixel indicated as being greater than the parameter, the method of compressing image information being characterized in that: an image in each frame is divided into blocks in advance, and each of all blocks is approximated by (replaced with) a single plane defined by three data representing the magnitude of a pixel value in the block, the block-to-block gradient of the pixel value in an x direction, and the block-to-block gradient of the pixel value in a y direction.

[0034] In the entropy coding process, codes which will appear in successive frames are predicted, and small deviations from predicted codes are output thereby reducing the redundancy of information. The other information is compressed by means of adaptive Huffman coding or adaptive arithmetic coding in which coding is performed on the basis of a table selected from a plurality of tables in accordance with predicted information.

Problems solved by technology

In the case of a motion image in a video telephone or the like, images of adjacent frames are very similar to each other, and thus the temporal change is limited.

However, in the conventional image signal compression technique, because of the complexity of the block coding process, it is difficult to achieve both a high compression ratio and a high speed in the predictive compression coding of image data or audio data.

This means that the code includes a large amount of redundancy.

Furthermore, when a difference between frames is great, significant degradation in image quality occurs, and a high-quality image cannot be obtained.

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