A method implemented in a video coding device, the method comprising: obtaining , by a processor of the video coding device, a coding tree unit including a coding tree node; characterized in that the method further comprises: partitioning , by the processor, luma samples and chroma samples in a first coding tree node of the coding tree unit according to a common coding tree when a size of the first coding tree node exceeds a threshold; partitioning , by the processor, the luma samples in a second coding tree node of the coding tree unit with a luma coding sub-tree when a size of the second coding tree node is equal to or less than the threshold; and partitioning , by the processor, the chroma samples in the second coding tree node of the coding tree unit with a chroma coding sub-tree when the size of a second coding tree node is equal to or less than the theshold, wherein when the video coding device is an encoder, the method further comprising encoding the chroma samples and the luma samples into a bitstream based on the common coding tree, the luma coding sub-tree, and the chroma coding sub-tree; and wherein when the video coding device is a decoder, the method further comprising reconstructing chroma data and luma data received from a bitstream into a slice of a video frame based on the common coding tree, the luma coding sub-tree, and the chroma coding sub-tree. obtaining , by a processor of the video coding device, a coding tree unit including a coding tree node; characterized in that the method further comprises: partitioning , by the processor, luma samples and chroma samples in a first coding tree node of the coding tree unit according to a common coding tree when a size of the first coding tree node exceeds a threshold; partitioning , by the processor, the luma samples in a second coding tree node of the coding tree unit with a luma coding sub-tree when a size of the second coding tree node is equal to or less than the threshold; and partitioning , by the processor, the chroma samples in the second coding tree node of the coding tree unit with a chroma coding sub-tree when the size of a second coding tree node is equal to or less than the theshold, partitioning , by the processor, luma samples and chroma samples in a first coding tree node of the coding tree unit according to a common coding tree when a size of the first coding tree node exceeds a threshold; partitioning , by the processor, the luma samples in a second coding tree node of the coding tree unit with a luma coding sub-tree when a size of the second coding tree node is equal to or less than the threshold; and partitioning , by the processor, the chroma samples in the second coding tree node of the coding tree unit with a chroma coding sub-tree when the size of a second coding tree node is equal to or less than the theshold, wherein when the video coding device is an encoder, the method further comprising encoding the chroma samples and the luma samples into a bitstream based on the common coding tree, the luma coding sub-tree, and the chroma coding sub-tree; and wherein when the video coding device is a decoder, the method further comprising reconstructing chroma data and luma data received from a bitstream into a slice of a video frame based on the common coding tree, the luma coding sub-tree, and the chroma coding sub-tree. <EOS>