Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-08-06
2001-07-17
Le, Vu (Department: 2713)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240210
Reexamination Certificate
active
06263024
ABSTRACT:
TECHNICAL FIELD
The present invention relates to image coding apparatus and image decoding apparatus for coding and decoding digital images, and also relates to recording media that record computer programs to implement these apparatuses by software.
BACKGROUND ART
One of the current standard recommendations on method for coding/decoding digital images with an interlaced structure is ITU-TH.262NN which is capable of efficiently coding/decoding TV signals such as NTSC.
There is another method for coding/decoding digital images including not only pixel luminance and chrominance signal values, but also form information signals that indicate the form of an object, which is adopted as an evaluation model of the ISO/IEC MPEG4 (ISO/IEC ITC/SC29/WG11 N1469 November 1996).
This method is characterized by the ability not only to effectively reduce the amount of codes by coding/decoding luminance signal and chrominance signal for only significant pixels indicated by the form information, but also to easily synthesize images in accordance with the form information.
However, the MPEG4 evaluation model described above does not take into account images which have an interlaced structure in which one frame contains 2 fields, which prevents efficient coding/decoding of input images with the interlaced structure.
In addition, the H.262 takes account of a motion compensation method and discrete cosine transformation a by taking the interlaced structure for luminance and chrominance signals into consideration, whereas it uses as the method for coding binary images which indicates a significant form, special methods such as down-sampling, up-sampling, and prediction of variation locations of pixel values that are not considered by the H.262, which prevents the coding/decoding means applicable to the interlaced structure used in the H.262 from being simply adopted.
DISCLOSURE OF INVENTION
The present invention has taken into account such circumstances and its objective is to provide an image coding apparatus and image decoding apparatus capable of improving the coding efficiency when coding/decoding input images by adaptively selecting for each block whether to code/decode form information images in field units or in frame units.
To achieve the above objective, the present invention implements an image coding apparatus that inputs a binary digital image with an interlaced structure with one frame consisting of 2 fields, divides said image into two-dimensional blocks consisting of a plurality of pixels, judges for each block whether to carry out coding processing in field units or frame units and carries out coding in field units or frame units for each block based on the result of mode judgment.
Furthermore, the present invention implements an image decoding apparatus that decodes a binary digital image with an interlaced structure with one frame consisting of two fields from the image coding signal coded by the above image coding apparatus for each two-dimensional block consisting of a plurality of pixels, in field units or frame units in accordance with the mode information.
Thus, by adaptively selecting for each block whether to perform coding/decoding in field units or frame units allows a highly efficient image coding/decoding apparatus to be implemented.
The image coding apparatus of the present invention is an image coding apparatus that performs coding by dividing a binary digital image into blocks consisting of a plurality of pixels, judging for each block which provides better coding efficiency, coding processing in field units or coding processing in frame units.
On the other hand, the image decoding apparatus of the present invention is an image decoding apparatus that decodes from the image coding signal to a binary digital image and switches decoding processing in field units or decoding processing in frame units based on the mode information for each block.
Furthermore, when coding a binary digital image, the present invention judges for each block which provides better efficiency; down-sampling in field units or down-sampling in frame units.
When decoding a binary digital image, the image decoding apparatus of the present invention switches for each block down-sampling processing in field units or down-sampling processing in frame units based on the mode information.
On the other hand, when coding a binary digital image, the image coding apparatus of the present invention judges for each block which provides better efficiency; motion compensation in field units or motion compensation in frame units.
When decoding a binary digital image, the image decoding apparatus of the present invention switches for each block motion compensation in field units or motion compensation in frame units based on the mode information.
Furthermore, when coding a binary digital image, the image coding apparatus of the present invention judges for each block which provides better efficiency; detection of pixel value change points in field units or frame units in the image coding apparatus that performs coding of the positional relationship between a target pixel and pixels with variable pixel values.
The image decoding apparatus of the present invention is an image decoding apparatus that decodes a binary digital image from the positional relationship between a target pixel and pixels with variable pixel values and switches for each block whether to calculate the location of pixels with variable pixel values in field units or frame units based on the mode information.
The image coding apparatus of the present invention is an image coding apparatus that when coding a binary digital image, determines probability distribution of the pixel value of the target pixel from the pixel value distribution status of the peripheral pixels and carries out coding of the pixel value of the target pixel according to the probability distribution, judging for each block which provides better efficiency to determine the probability distribution, surveying the distribution of peripheral pixel values in field units or frame units.
The image decoding apparatus of the present invention is an image decoding apparatus that determines the probability distribution of the pixel value of a target pixel from the pixel value distribution of the peripheral pixels and carries out decoding of the pixel value of the target pixel according to the probability distribution, switching for each block the method for surveying the distribution status of peripheral pixel values to determine the probability distribution in field units or frame units. In the image coding apparatus of the present invention that determines the probability distribution of the pixel value of the target pixel from the distribution status of pixel values of predicted motion compensation images and carries out coding of the pixel value of the target pixel according to the probability distribution, it determines for each block which provides better efficiency; surveying the distribution of pixel values of the predicted motion compensation image in field units or frame units. In the image decoding apparatus of the present invention that determines the probability distribution of the pixel value of the target pixel from the distribution status of pixel values of predicted motion compensation images and carries out decoding of the pixel value according to the probability distribution, it switches for each block the method for surveying the distribution of pixel values of the predicted motion compensation images in field units or frame units. When coding binary digital images and multi-level digital images for each block, the image coding apparatus of the present invention selects whether to perform coding processing of binary digital images in field units or frame units based on the mode information of the multi-level digital images of said block. This eliminates the necessity of using special codes for the mode information of binary digital images, making it possible to improve the coding efficiency. When decoding binary digital images and multi-level digital images for each
Greenblum & Bernstein P.L.C.
Le Vu
Matsushita Electric - Industrial Co., Ltd.
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