RECORDING MEDIUM HAVING RECORDED THEREON CODED INFORMATION USING PLUS AND/OR MINUS ROUNDING OF IMAGES

摘要

Medium with image decoding program effecting: extracting motion vector information, quantized DCT coefficients, and rounding method information from input information; dequantizing quantized DCT coefficients to DCT coefficients; performing inverse DCT conversion to an error image; synthesizing a prediction image of a currently decoded image by performing motion compensation using motion vector information, rounding method information, and a previously decoded reference image; and adding prediction and error images to obtain a decoded image; wherein motion compensation is performed with half-pixel accuracy and uses bilinear interpolation to calculate intensity values of chrominance or luminance at points where no pixels exist in the reference image, the interpolation using a positive or negative rounding method, using rounding specified by rounding method information included in coded information of the currently decoded image; wherein the rounding method specifies one of two values specifying a positive or negative rounding method, via rounding method information of one bit.

主权项

1. A computer-readable medium having stored thereon an image decoding program which, when executed by a computer, effects operations comprising:
extracting motion vector information, quantized DCT coefficients, and rounding method information from input information to be decoded; dequantizing the quantized DCT coefficients to obtain DCT coefficients; performing inverse DCT conversion on the DCT coefficients to obtain an error image; synthesizing a prediction image of a currently decoded image by performing motion compensation using the motion vector information, the rounding method information, and a reference image which is a previously decoded image; and adding the prediction image to the error image to obtain a decoded image; wherein the motion compensation is performed with half-pixel accuracy and uses bilinear interpolation to calculate intensity values of chrominance or luminance at points where no pixels actually exist in the reference image, the bilinear interpolation being performable using a positive rounding method or a negative rounding method; wherein the bilinear interpolation is performed using a rounding method specified by the rounding method information; wherein the rounding method information is included in coded information of the currently decoded image; wherein the rounding method specifies one of two values; wherein one of two values specifies a positive rounding method, and another one of two values specifies a negative rounding method; and wherein the rounding method information consists of one bit.