ctual colour representation method in use. The actual colour representation method in use can be indicated in syntax that is specified in Annex E. The (monochrome) auxiliary arrays, which may or may not be present as auxiliary pictures in a coded video sequence, are optional for decoding and can be used for such purposes as alpha blending. The variables SubWidthC, and SubHeightC are specified in Table 6-1, depending on the chroma format sampling structure, which is specified through chroma_format_idc and separate_colour_plane_flag. An entry marked as "_" in Table 6-1 denotes an undefined value for SubWidthC or SubHeightC. Other values of chroma_format_idc, SubWidthC, and SubHeightC may be specified in the future by ITU-T ISO/IEC. Table 6-1 - SubWidthC, and SubHeightC values derived from chroma_format_idc and separate_colour_plane_flag chroma_format_idc separate_colour_plane_flag Chroma Format SubWidthC SubHeightC monochrome 4:2:0 4:2:2 4:4:4 4:4:4 In monochrome sampling there is only one sample array, which is nominally considered the luma array. In 4:2:0 sampling, each of the two chroma arrays has half the height and half the width of the luma array. In 4:2:2 sampling, each of the two chroma arrays has the same height and half the width of the luma array. In 4:4:4 sampling, depending on the value of separate_colour_plane_flag, the following applies: If separate_colour_plane_flag is equal to 0, each of the two chroma arrays has the same height and width as the luma array. Otherwise (separate_colour_plane_flag is equal to 1), the three colour planes are separately processed as monochrome sampled pictures. The width and height of the luma sample arrays are each an integer multiple of 16. In coded video sequences using 4:2:0 chroma sampling, the width and height of chroma sample arrays are each an integer multiple of 8. In coded video sequences using 4:2:2 sampling, the width of the chroma sample arrays is an integer multiple of 8 and the height is an integer multiple of 16. The height of a luma array that is coded 