Method of orthogonal transform coding/decoding
First Claim
1. A method of orthogonal transform coding to quantize transformed coefficients which are divided into a plurality of bands to which respective different numbers of coefficients are allotted, comprising the steps of:
- arranging a plurality of quantization threshold level-tables designed on the basis of a probability density function of coefficient value on the assumption of a pre set number of coefficients, the quantization threshold level-tables corresponding to pre-set plural numbers of quantization bits respectively,selecting a table among the quantization threshold level-tables in response to a number of bits which the quantization of coefficients on a band is to be performed, andcompensating the quantization levels in the selected table with the square root of a ratio of the number of coefficients on tee band to the pre-set number of coefficients,thus to compare the coefficient values and the compensated threshold levels with each other to quantize the coefficient values.
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Abstract
There is provided the method of orthogonal transform coding/decoding to quantize/de-quantize transformed coefficients which are divided into a plurality of bands to which respective different numbers of coefficient are allotted. Quantization/de-quantization tables are arranged on the basis of a probability density function of the coefficient values designed on the assumption of a specified number of coefficients so as to correspond to the number of quantization/de-quantization bits. The values in the quantization/de-quantization tables selected according to the number of quantization/de-quantization bits are adaptively compensated on the basis of an actual number of coefficients on each band to quantize/de-quantize the coefficient values.
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Citations
3 Claims
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1. A method of orthogonal transform coding to quantize transformed coefficients which are divided into a plurality of bands to which respective different numbers of coefficients are allotted, comprising the steps of:
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arranging a plurality of quantization threshold level-tables designed on the basis of a probability density function of coefficient value on the assumption of a pre set number of coefficients, the quantization threshold level-tables corresponding to pre-set plural numbers of quantization bits respectively, selecting a table among the quantization threshold level-tables in response to a number of bits which the quantization of coefficients on a band is to be performed, and compensating the quantization levels in the selected table with the square root of a ratio of the number of coefficients on tee band to the pre-set number of coefficients, thus to compare the coefficient values and the compensated threshold levels with each other to quantize the coefficient values. - View Dependent Claims (2)
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3. A method of orthogonal transform decoding to de-quantize quantized values of transformed coefficients which are divided into a plurality of bands to which respective different number of coefficients are allotted, comprising the steps of:
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arranging a plurality of de-quantized value-tables designed on the basis of a probability density function of coefficient value on the assumption of a pre-set number of coefficients, the de-quantized value-tables corresponding to pre-set plural numbers of de-quantization bits, and the steps being the same as each other, selecting a table among the de-quantized value-tables in response to a number of bits by which the quantization of coefficients on a band was performed, and compensating the de-quantized values in the selected table with the square root of a ratio of the number of coefficients on the band to the pre-set number of coefficients, the de-quantized values corresponding to the quantized values of coefficients on the band.
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Specification