Image coding system with adaptive spatial frequency and quantization step and method thereof
First Claim
1. An image coding system in a system including an image inputting means, an image coding means for calculating orthogonal transform coefficients of the inputted image, and an image code transmitting means, comprising:
- previously defined parameter information, arranged in a table, having a plurality of combinations of quantizing step values and upper limit values of image space frequencies in correspondence with an image code size;
means for deciding one combination from said parameter information on the basis of a size of an image code of the inputted image coded by said image coding means; and
quantizing means for quantizing the orthogonal transform coefficients for space frequencies below said upper limit values of image space frequencies of the decided combination, on the basis of the quantizing step value of said decided combination, while executing no quantization for space frequencies higher than said upper limit values of image space frequencies of said decided combination.
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Abstract
An image coding system and method thereof previously defines a plurality of combinations into a table. The table includes candidate values for quantizing steps and candidate values for upper limit values of space frequencies in correspondence with an image code size. The frequencies are coded into the pattern table on the basis of an error between the required code size, which is decided by the system performance, and required images. The generated code size is taken at the time of prediction coding between motion compensation frames. One combination of a quantizing step and upper limit values of space frequency are selected. The combination is coded from the candidate values depending on the image attribute and codes conforming to an international standard. The combinations are generated at a satisfactory coding efficiency. The coding efficiency is achieved by controlling the coding parameters depending on the image attribute and generated code size.
71 Citations
21 Claims
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1. An image coding system in a system including an image inputting means, an image coding means for calculating orthogonal transform coefficients of the inputted image, and an image code transmitting means, comprising:
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previously defined parameter information, arranged in a table, having a plurality of combinations of quantizing step values and upper limit values of image space frequencies in correspondence with an image code size; means for deciding one combination from said parameter information on the basis of a size of an image code of the inputted image coded by said image coding means; and quantizing means for quantizing the orthogonal transform coefficients for space frequencies below said upper limit values of image space frequencies of the decided combination, on the basis of the quantizing step value of said decided combination, while executing no quantization for space frequencies higher than said upper limit values of image space frequencies of said decided combination. - View Dependent Claims (2, 3, 4, 5)
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6. A TV conference system in a system including an image inputting means, an image coding means for calculating orthogonal transform coefficients of the inputted image, and an image code transmitting means, comprising:
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previously defined parameter information, stored in a table, having a plurality of combinations of quantizing step values and upper limit values of image space frequencies in correspondence with an image code size; means for executing a motion compensation prediction and generating a difference block, for image data inputted from said image inputting means, obtaining an orthogonal transform coefficient by executing an orthogonal transform for the generated difference block; means for deciding one combination from said parameter information on the basis of a size of an image code of the inputted image coded by said orthogonal transform coefficient; and quantizing means for quantizing the orthogonal transform coefficients for space frequencies below said upper limit values of image space frequencies of the decided combination, on the basis of the quantizing step value of said decided combination, while executing no quantization for space frequencies higher than said upper limit values of image space frequencies of said decided combination. - View Dependent Claims (7)
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8. A moving picture coding system in a system including an image inputting means, an image coding means for calculating orthogonal transform coefficients of the inputted image, and an image code transmitting means, comprising:
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previously defined parameter information, stored in a table, having a plurality of combinations of quantizing step values and upper limit values of image space frequencies in correspondence with an image code size; means for executing a motion compensation prediction and generating a difference block, for image data inputted from said image inputting means, obtaining an orthogonal transform coefficient by executing an orthogonal transform for the generated difference block; means for deciding a plurality of combinations from said parameter information on the basis of a size of an image code of the inputted image coded by said orthogonal transform coefficient; means for estimating the image attributed on the basis of at least one of said difference block and orthogonal transform coefficient; means for selecting a combination of a desired one quantizing step value and upper limit value of space frequency from said decided plurality of combinations in correspondence with said estimated image attribute; and quantizing means for quantizing the orthogonal transform coefficients, for space frequencies below said upper limit values of image space frequencies of the selected combination, on the basis of the quantizing step value of said selected combination, while executing no quantization for space frequencies higher than said upper limit values of image space frequencies of said selected combination. - View Dependent Claims (9, 10, 11)
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12. A moving picture coding system in a system including an image inputting means, an image coding means for calculating orthogonal transform coefficients of the inputted image, a frame memory, and an image code transmitting means, comprising:
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previously defined parameter information, stored in a table, having a plurality of combinations of quantizing step values and upper limit values of image space frequencies in correspondence with an image code size; means for dividing inputted image data into blocks of n pixels×
n pixels, integrating a plurality of said blocks, and generating macro blocks;means for generating a motion vector for each of said macro blocks by performing operations between said macro blocks and image data stored in said frame memory; means for executing motion compensation prediction by generating a difference block for each of said divided blocks; means for obtaining an orthogonal transform coefficient by executing orthogonal transform for said difference blocks; means for deciding at least one combination from said parameter information on the basis of said image code size of the inputted image coded by said coding means; means for estimating the image attribute on the basis of at least one of said difference block and said orthogonal transform coefficient; means for selecting a combination of a desired one quantizing step value and a desired upper limit value of space frequency from said decided at least one combination in correspondence with said estimated image attribute; and quantizing means for quantizing the orthogonal transform coefficients for space frequencies below said upper limit values of image space frequencies of the selected combination, on the basis of the quantizing step value of said selected combination, while executing no quantization for space frequencies higher than said upper limit values of image space frequencies of said selected combination. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. An image coding method in a system including an image inputting means, an image coding means, and an image code transmitting means, comprising:
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a step of obtaining previously defined parameter information having a plurality of combinations of quantizing steps and upper limit values of image space frequencies in accordance with an image code size, the parameter information being stored in a table; a step of deciding one combination from said parameter information on the basis of a size of an image code of the inputted image coded by said image coding means; and a quantizing step of quantizing the orthogonal transform coefficients for space frequencies below said upper limit values of image space frequencies of the decided combination, on the basis of the quantizing step value of said decided combination, while executing no quantization for space frequencies higher than said upper limit values of image space frequencies of said decided combination.
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20. A method of TV conference in a system including an image inputting means, an image coding means, and an image code transmitting means, comprising:
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a step of obtaining previously defined parameter information having a plurality of combinations of quantizing steps and upper limit values of image space frequencies depending on the image code size, the parameter information being stored in a table; a step of executing a motion compensation prediction and generating a difference block, for image data inputted from said image inputting means, obtaining an orthogonal transform coefficient by executing orthogonal transform for the generated difference block; a step of deciding one combination from said parameter information on the basis of a size of an image code of the inputted image coded by said orthogonal transform coefficient; and a quantizing step of quantizing the orthogonal transform coefficients for space frequencies below said upper limit values of image space frequencies of the decided combination, on the basis of the quantizing step value of said decided combination, while executing no quantization for space frequencies higher than said upper limit values of image space frequencies of said decided combination.
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21. A moving picture coding method in a system including an image inputting means, an image coding means, and an image code transmitting means, comprising:
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a step of obtaining previously defined parameter information having a plurality of combinations of quantizing steps and upper limit values of image space frequencies in accordance with an image code size, the parameter information being stored in a table; a step of executing a motion compensation prediction and generating a difference block, for image data inputted from said image inputting means, obtaining an orthogonal transform coefficient by executing orthogonal transform for the generated difference block; a step of deciding a plurality of combinations from said parameter information on the basis of a size of an image code of the inputted image coded by said orthogonal transform coefficient; a step of estimating the image attributed on the basis of at least one of said difference block and orthogonal transform coefficient; a step of selecting a combination of a desired one quantizing step value and upper limit value of space frequency from said decided plurality of combinations in correspondence with said estimated image attribute; and a quantizing step of quantizing the orthogonal transform coefficients for space frequencies below said upper limit values of image space frequencies of the selected combination, on the basis of the quantizing step value of said selected combination, while executing no quantization for space frequencies higher than said upper limit values of image space frequencies of said selected combination.
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Specification