A method of coding video data, the method comprising: determining an intra prediction mode for a chroma prediction unit of a chroma block (176, 204) of the video data based on an intra prediction mode of a luma prediction unit in a corresponding luma block (172, 202), wherein the partitioning of the corresponding luma block into luma prediction units is determined using a first tree structure that is separate from a second tree structure that determines the partitioning of the chroma block into chroma predictions units, the first and second tree structures being quad-tree-binary-tree structures, and coding the chroma prediction unit according to the determined intra prediction mode; characterized in that the step of determining an intra prediction mode for a chroma prediction unit of a chroma block based on an intra prediction mode of a luma prediction unit in a corresponding luma block comprises: determining one of a plurality of luma prediction units of the corresponding luma block that is located at a position corresponding to a center position of the luma block corresponding to the chroma block, wherein the center position is defined according to a coordinate tuple including an x coordinate defined using twice the horizontal offset of the chroma block and a y coordinate defined using twice the vertical offset of the chroma block, wherein the coordinate tuple is based on the width W and height H of the chroma block such that the determined one of the plurality of luma prediction units is at the center position having the coordinate tuple 2x + W-1, 2y + H-1; and deriving a derived mode, DM, for the chroma mode from a luma mode associated with the luma prediction unit located at the center position of the corresponding luma block partition; wherein the video data are in the 4:2:0 color format. determining an intra prediction mode for a chroma prediction unit of a chroma block (176, 204) of the video data based on an intra prediction mode of a luma prediction unit in a corresponding luma block (172, 202), wherein the partitioning of the corresponding luma block into luma prediction units is determined using a first tree structure that is separate from a second tree structure that determines the partitioning of the chroma block into chroma predictions units, the first and second tree structures being quad-tree-binary-tree structures, and coding the chroma prediction unit according to the determined intra prediction mode; characterized in that the step of determining an intra prediction mode for a chroma prediction unit of a chroma block based on an intra prediction mode of a luma prediction unit in a corresponding luma block comprises: determining one of a plurality of luma prediction units of the corresponding luma block that is located at a position corresponding to a center position of the luma block corresponding to the chroma block, wherein the center position is defined according to a coordinate tuple including an x coordinate defined using twice the horizontal offset of the chroma block and a y coordinate defined using twice the vertical offset of the chroma block, wherein the coordinate tuple is based on the width W and height H of the chroma block such that the determined one of the plurality of luma prediction units is at the center position having the coordinate tuple 2x + W-1, 2y + H-1; and deriving a derived mode, DM, for the chroma mode from a luma mode associated with the luma prediction unit located at the center position of the corresponding luma block partition; wherein the video data are in the 4:2:0 color format. deriving a derived mode, DM, for the chroma mode from a luma mode associated with the luma prediction unit located at the center position of the corresponding luma block partition; wherein the video data are in the 4:2:0 color format.