Notes for Algorithm description for Versatile Video Coding and Test Model 5
##3.1 VVC coding architecture
##3.2 Partitioning
a CTU consists of an N×N block of luma samples together with two corresponding blocks of chroma samples
The maximum allowed size of the luma block in a CTU is specified to be 128×128 (although the maximum size of the luma transform blocks is 64×64).
###3.2.3 Partitioning of the CTUs using a tree structure
In VVC, a quadtree with nested multi-type tree using binary and ternary splits segmentation structure replaces the concepts of multiple partition unit types
A coding tree unit (CTU) is first partitioned by a quaternary tree (a.k.a. quadtree) structure. Then the quaternary tree leaf nodes can be further partitioned by a multi-type tree structure.