1. A decoding apparatus which decodes an encoded picture resulting from encoding of an input picture by an encoding apparatus, wherein the encoding apparatus includes: a first calculation unit configured to calculate a first parameter corresponding to a distance between the input picture that is encoded and a first reference picture referred to by the input picture and calculate a second parameter corresponding to a distance between the first reference picture and a second reference picture referred to by the input picture; a judgment unit configured to judge whether or not a value of a third parameter calculated based on a ratio between the first parameter and the second parameter is included in a predetermined range; a second calculation unit configured to calculate a predictive pixel value of the input picture by scaling pixel values of the first and second reference pictures using weighting coefficients calculated using the first and second parameters when the value of the third parameter is included in the predetermined range and calculate a predictive pixel value of the input picture by scaling pixel values of the first and second reference pictures using weighting coefficients having predetermined values when the value of the third parameter is not included in the predetermined range; and an encoding unit configured to encode the input picture using the calculated predictive pixel value, and wherein said decoding apparatus comprises: a first parameter calculation unit configured to calculate the first parameter corresponding to the distance between the encoded picture and the first reference picture referred to by the encoded picture; a second parameter calculation unit configured to calculate the second parameter corresponding to the distance between the first reference picture and the second reference picture referred to by the encoded picture; a judgment unit configured to judge whether or not the value of the third parameter calculated based on the ratio between the first parameter and the second parameter is included in the predetermined range; a predictive pixel value generation unit configured to: calculate the predictive pixel value of the encoded picture by scaling the pixel values of the first and second reference pictures using the weighting coefficients calculated using the first and second parameters when the value of the third parameter is included in the predetermined range; and calculate the predictive pixel value of the encoded picture by scaling the pixel values of the first and second reference pictures using the weighting coefficients having the predetermined values when the value of the third parameter is not included in the predetermined range; and a decoding unit configured to decode the encoded picture using the calculated predictive pixel value.