Video encoding method and apparatus, and video decoding method and apparatus using interpolation filter on which image characteristic is reflected

A video encoding method comprising:

• determining a degree of change between neighboring samples of at least one integer pixel unit adjacent to a reference sample of an integer pixel unit of a current sample and the reference sample;
• determining an interpolation filter among interpolation filters for producing reference samples of a sub-pixel unit to predict the current sample, based on the degree of change;
• determining a predicted sample value of the current sample by using a reference sample of a sub-pixel unit produced by applying the determined interpolation filter to the reference sample and the neighboring samples;
• and
• encoding a residual value between the predicted sample value and a sample value of the current sample,
• wherein the interpolation filters have different frequency passbands.

A video decoding apparatus comprising:

• a reference sample determiner configured to determine a degree of change between neighboring samples of at least one integer pixel unit adjacent to a reference sample of an integer pixel unit of a current sample and the reference sample, and determine an interpolation filter among interpolation filters for producing reference samples of a sub-pixel unit to predict the current sample, based on the degree of change;
• and
• a predictor configured to determine a predicted sample value of the current sample by using a reference sample of a sub-pixel unit produced by applying the determined interpolation filter to the reference sample and the neighboring samples, and produce a reconstructed sample value of the current sample by using a residual value between the predicted sample value and a sample value of the current sample,
• wherein the interpolation filters have different frequency passbands.