An electronic apparatus, comprising a decoder module configured to: decode a denominator for a luma weighting factor of a target image from encoded data comprising encoded video bit stream using weighted prediction, wherein the denominator for the luma weighting factor represents fixed point precision of the luma weighting factor; decode a first difference value that is equal to a value of a difference between a denominator for a chroma weighting factor of the target image from the encoded data and the denominator for the luma weighting factor, wherein the denominator for the chroma weighting factor represents fixed point precision of the chroma weighting factor; derive the denominator for the chroma weighting factor by adding the denominator for the luma weighting factor and the first difference value; derive a first reference value of the luma weighting factor according to the denominator for the luma weighting factor, wherein the first reference value is equal to a value obtained by left shift of "1" by at least one binary digit specified by the denominator for the luma weighting factor; decode a difference value of the luma weighting factor from the encoded data, wherein the difference value of the luma weighting factor is equal to a value of a difference between the luma weighting factor and the first reference value; derive the luma weighting factor by adding the first reference value and the difference value of the luma weighting factor; derive a reference value of the chroma weighting factor according to the denominator for the chroma weighting factor, wherein the reference value of the chroma weighting factor is equal to a value obtained by left shift of "1" by at least one binary digit specified by the denominator for the chroma weighting factor; decode a difference value of the chroma weighting factor from the encoded data, wherein the difference value of the chroma weighting factor is equal to a value of a difference between the chroma weighting factor and the reference value of the chroma weighting factor; and derive the chroma weighting factor by adding the reference value of the chroma weighting factor and the difference value of the chroma weighting factor. decode a denominator for a luma weighting factor of a target image from encoded data comprising encoded video bit stream using weighted prediction, wherein the denominator for the luma weighting factor represents fixed point precision of the luma weighting factor; decode a first difference value that is equal to a value of a difference between a denominator for a chroma weighting factor of the target image from the encoded data and the denominator for the luma weighting factor, wherein the denominator for the chroma weighting factor represents fixed point precision of the chroma weighting factor; derive the denominator for the chroma weighting factor by adding the denominator for the luma weighting factor and the first difference value; derive a first reference value of the luma weighting factor according to the denominator for the luma weighting factor, wherein the first reference value is equal to a value obtained by left shift of "1" by at least one binary digit specified by the denominator for the luma weighting factor; decode a difference value of the luma weighting factor from the encoded data, wherein the difference value of the luma weighting factor is equal to a value of a difference between the luma weighting factor and the first reference value; derive the luma weighting factor by adding the first reference value and the difference value of the luma weighting factor; derive a reference value of the chroma weighting factor according to the denominator for the chroma weighting factor, wherein the reference value of the chroma weighting factor is equal to a value obtained by left shift of "1" by at least one binary digit specified by the denominator for the chroma weighting factor; decode a difference value of the chroma weighting factor from the encoded data, wherein the difference value of the chroma weighting factor is equal to a value of a difference between the chroma weighting factor and the reference value of the chroma weighting factor; and derive the chroma weighting factor by adding the reference value of the chroma weighting factor and the difference value of the chroma weighting factor.