Scalable video encoding method and apparatus using image up-sampling in consideration of phase-shift and scalable video decoding method and apparatus

An up-sampling method for scalable video decoding, the up-sampling method comprising:

• obtaining, from an improvement layer bitstream, information indicating a value of a phase shift for an up-sampling filter, wherein the value of a phase shift is a pixel displacement between a pixel in a pixel unit of a low resolution image and a pixel in a sub-pixel unit of a high resolution image and the pixel in a sub-pixel unit of a high resolution image is determined by up-sampling based on a scaling factor between the high resolution image and the low resolution image;
• selecting at least one filter coefficient set corresponding to the determined value of a phase shift from the information indicating the value of a phase shift for an up-sampling filter, included in filter coefficient data comprising corresponding filter coefficient sets for values of phase shifts;
• and
• generating the high resolution image by performing filtering on the low resolution image by using the selected at least one filter coefficient set,
• wherein the information indicating a value of a phase shift for an up-sampling filter is signaled via a picture parameter set (PPS) included in the improvement layer bitstream,
• the selecting at least one filter coefficient set comprises selecting a filter coefficient set corresponding to a first phase shift among sets of filter coefficients for up-sampling for a sampling position having the second phase shift,
• the sets of filter coefficients comprises filter coefficients for sub-pixel positions whose denominator is 2 to the power of n,
• the first phase shift is one from among the sub-pixel positions whose denominator is 2 to the power of n, and the second phase shift is a sub-pixel position whose denominator is not 2 to the power of m and whose numerator is 1, and
• wherein n and m are integers, and the first phase shift is different from the second phase shift.