Video coding method and device for avoiding small chroma block intra prediction

A method for controlling block intra prediction for an encoder, comprising:

• obtaining a video bitstream;
• encoding the video bitstream with prediction information of a current coding unit (CU) in a segment of a current picture, comprising:
• upon determining that the current CU belongs to a current Small Chroma Intra Prediction Unit (SCIPU) and a tree depth of the SCIPU is less than or equal to a threshold T2, and that the prediction type of the chroma CB is intra prediction, including the prediction type of the chroma CB in the prediction information, a SCIPU being a coding tree node whose chroma CB size is larger than or equal to TH chroma samples and has at least one child luma CB whose size is smaller than 4TH luma samples, and T2 being 1 or 2;
• and
• outputting the encoded video bitstream, wherein a width of any reconstructed chroma CB intra-predicted from the encoded video bitstream is greater than 2.

A method for controlling block intra prediction for an encoder, comprising:

• obtaining a video bitstream;
• encoding the video bitstream with prediction information of a current coding unit (CU) in a segment of a current picture, comprising:
• upon determining that the segment has a dual tree structure indicating separate partitioning structures for luma and chroma components of the segment, and that the prediction type of the segment is intra prediction, including the prediction type of the segment and a variable MinCbLog2SizeC in the prediction information, the variable MinCbLog2SizeC indicating a binary logarithmic value of a minimum size of the chroma CB of the current CU;
• and
• outputting the encoded video bitstream, wherein a width of any reconstructed chroma CB intra-predicted from the coded video bitstream is greater than 2.