A method for decoding a bitstream generated by encoding a video sequence of a plurality of pictures, the method comprising: decoding, from a sequence parameter set of the bitstream, information on a chroma sampling format and high-level syntax elements related to differential encoding of residual signals, the high-level syntax elements comprising a single common control flag indicating whether the differential encoding is enabled for the residual signals of each of luma and chroma components of the video sequence, and information on a maximum block size allowed for the differential encoding; if a target block to be currently decoded satisfies conditions defined by the information on the chroma sampling format and the high-level syntax elements, decoding a first chroma syntax element indicating whether the differential encoding is applied to a chroma block corresponding to the target block or not, and decoding a second chroma syntax element indicating a differential encoding direction applied to the chroma block based on the first chroma syntax element; reconstructing a residual block of the chroma block from the bitstream; and reconstructing the chroma block by modifying the residual signals within the residual block according to the differential encoding direction indicated by the second chroma syntax element, wherein: the conditions defined by the information on the chroma sampling format and the high-level syntax elements are satisfied when: the common control flag indicates that the differential encoding is enabled for both of the luma and chroma components of the video sequence, the value obtained by dividing the width of the target block by a horizontal scaling factor determined by the chroma sampling format is smaller than or equal to a horizontal threshold indicated by the information on the maximum block size, and the value obtained by dividing the height of the target block by a vertical scaling factor determined by the chroma sampling format is smaller than or equal to a vertical threshold indicated by the information on the maximum block size. decoding, from a sequence parameter set of the bitstream, information on a chroma sampling format and high-level syntax elements related to differential encoding of residual signals, the high-level syntax elements comprising a single common control flag indicating whether the differential encoding is enabled for the residual signals of each of luma and chroma components of the video sequence, and information on a maximum block size allowed for the differential encoding; if a target block to be currently decoded satisfies conditions defined by the information on the chroma sampling format and the high-level syntax elements, decoding a first chroma syntax element indicating whether the differential encoding is applied to a chroma block corresponding to the target block or not, and decoding a second chroma syntax element indicating a differential encoding direction applied to the chroma block based on the first chroma syntax element; reconstructing a residual block of the chroma block from the bitstream; and reconstructing the chroma block by modifying the residual signals within the residual block according to the differential encoding direction indicated by the second chroma syntax element, wherein: the conditions defined by the information on the chroma sampling format and the high-level syntax elements are satisfied when: the common control flag indicates that the differential encoding is enabled for both of the luma and chroma components of the video sequence, the value obtained by dividing the width of the target block by a horizontal scaling factor determined by the chroma sampling format is smaller than or equal to a horizontal threshold indicated by the information on the maximum block size, and the value obtained by dividing the height of the target block by a vertical scaling factor determined by the chroma sampling format is smaller than or equal to a vertical threshold indicated by the information on the maximum block size. the common control flag indicates that the differential encoding is enabled for both of the luma and chroma components of the video sequence, the value obtained by dividing the width of the target block by a horizontal scaling factor determined by the chroma sampling format is smaller than or equal to a horizontal threshold indicated by the information on the maximum block size, and the value obtained by dividing the height of the target block by a vertical scaling factor determined by the chroma sampling format is smaller than or equal to a vertical threshold indicated by the information on the maximum block size.