Coding method for coding pixel blocks and apparatus therefor
First Claim
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1. A coding method for coding image data in units of pixel blocks having a prescribed size, each of the pixel blocks constituting a picture, comprising the steps of:
- a calculation step of performing a calculation by using image data in a pixel block of a picture of interest and image data in a block of another picture, and generating difference values therebetween;
an orthogonal transformation step of orthogonally transforming the difference values and generating a DC component and AC components;
a masking step of masking a part of an AC component area containing AC components generated by said orthogonal transformation step, said part being determined based on the amount of coded image data; and
a quantizing step of quantizing the AC components processed by said masking step.
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Abstract
An amount of data coded in the past is detected at a prescribed period. Criteria for deciding whether a pixel block of interest is to be coded by processing for motion-compensated coding of interframe difference, processing for coding of interframe difference without motion compensation or processing for intraframe coding are adjusted based upon the amount of code detected.
36 Citations
20 Claims
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1. A coding method for coding image data in units of pixel blocks having a prescribed size, each of the pixel blocks constituting a picture, comprising the steps of:
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a calculation step of performing a calculation by using image data in a pixel block of a picture of interest and image data in a block of another picture, and generating difference values therebetween; an orthogonal transformation step of orthogonally transforming the difference values and generating a DC component and AC components; a masking step of masking a part of an AC component area containing AC components generated by said orthogonal transformation step, said part being determined based on the amount of coded image data; and a quantizing step of quantizing the AC components processed by said masking step. - View Dependent Claims (2, 3)
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4. A coding apparatus for coding image data in units of pixel blocks having a prescribed size, each of the pixel blocks constituting a picture, comprising:
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calculation means for performing a calculation by using image data in a pixel block of a picture of interest and image data in a block of another picture, and generating difference values therebetween; orthogonal transformation means for orthogonally transforming the difference values and generating a DC component and AC components; masking means for masking a part of an AC component area containing AC components generated by the orthogonal transformation means, said part being determined based on the amount of coded image data; and quantizing means for quantizing the AC components processed by said masking means. - View Dependent Claims (5, 6)
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7. A coding method for coding image data in units of pixel blocks having a prescribed size, each of the pixel blocks constituting a frame image, by using one type of coding method selected based upon correlation with a corresponding pixel block of a previous frame, comprising:
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a first transformation step of transforming difference information of a pixel block based upon the selected coding method into frequency space; a second transformation step of performing averaging in units of pixel blocks for converting the entirety of said pixel block into mean-value data; and a selecting step of adaptively selecting said first transformation step and said second transformation step. - View Dependent Claims (8, 9, 10)
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11. A coding apparatus for coding image data in units of pixel blocks having a prescribed size, each of the pixel blocks constituting a frame image, by using one type of coding processing selected based upon correlation with a corresponding pixel block of a previous frame, comprising:
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first transformation means for transforming difference information of a pixel block based upon the selected coding method into frequency space; second transformation means for performing averaging in units of pixel blocks for converting the entirety of said pixel block into mean-value data; and selecting means for adaptively selecting said first transformation means and said second transformation means. - View Dependent Claims (12, 13, 14)
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15. A coding apparatus for coding image data in units of pixel blocks having a prescribed size, each of the pixel blocks constituting a picture, comprising:
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calculating means for performing a calculation by using image data in a pixel block of a picture of interest and image data in a block of another picture, and generating difference values therebetween; orthogonal transformation means for orthogonally transforming the difference values; masking means for masking apart of an area containing orthogonal transformation coefficients generated by said orthogonal transformation means, said part being determined based on the amount of coded image data; and quantizing means for quantizing the orthogonal transformation coefficients processed by said masking means.
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16. A coding apparatus for coding image data in units of pixel blocks having a prescribed size, each of the pixel blocks constituting a picture, comprising:
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calculation means for performing a calculation by using image data in a pixel block of a picture of interest and image data in a block of another picture, and generating difference values therebetween; orthogonal transformation means for orthogonally transforming the difference values; masking means for masking a part of an area containing orthogonal transformation coefficients generated by said orthogonal transformation means, said part being determined based on the amount of coded image data; and quantizing means for quantizing the orthogonal transformation coefficients processed by said masking means, wherein a size of a part to be masked by said masking means is increased in proportion to the amount of coded image data. - View Dependent Claims (17)
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18. A coding method for coding image data in units of pixel blocks having a prescribed size, each of the pixel blocks constituting a picture, comprising the steps of:
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a calculation step of performing a calculation by using image data in a pixel block of a picture of interest and image data in a block of another picture, and generating difference values therebetween; an orthogonal transformation step of orthogonally transforming the difference values, and generating a DC component and AC components; a masking step of masking a part of an area containing orthogonal transformation coefficients generated by said orthogonal transformation step, said part being determined based on the amount of coded image data; and a quantizing step of quantizing the orthogonal transformation coefficients processed by said masking step. - View Dependent Claims (19, 20)
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Specification