Method of block vector clipping and coding for screen content coding and video coding

A method of video coding using coding modes including IntraBC mode (Intra-block copy mode) for a current picture, the method comprising:

• determining, by a processor of an apparatus, a coded block vector that is included in a bitstream for carrying data of the current picture, the coded block vector pointing from a current prediction unit in the current picture to a reference block in the current picture;
• determining whether the reference block is located at least partially inside a current coding unit containing the current prediction unit;
• in response to the reference block being determined to be located at least partially inside the current coding unit,
• determining, by the processor of the apparatus, a modified block vector by modifying the coded block vector, the modified block vector pointing from the current prediction block to a modified reference block that corresponds to vertically shifting or horizontally shifting the reference block to be outside the current coding unit, all samples of the modified reference block being available for coding the current prediction unit;
• performing at least one of:
• (i) in a case that the reference block is located on a left side of the current coding unit in a horizontal direction,
• determining whether the reference block is at least partially below a lower edge of a coding tree unit containing the current coding unit in a vertical direction, and
• in response to the reference block being determined to be located on the left side of the current coding unit and at least partially below the lower edge of the coding tree unit, determining the modified block vector by modifying the coded block vector such that the modified reference block is above the lower edge of the coding tree unit;
• and
• (ii) in a case that the reference block is located on a right side of the current coding unit in the horizontal direction,
• determining whether the reference block is at least partially below a upper edge of the coding tree unit containing the current coding unit in the vertical direction, and
• in response to the reference block being determined to be located on the right side of the current coding unit and at least partially below the upper edge of the coding tree unit, determining the modified block vector by modifying the coded block vector such that the modified reference block is above the upper edge of the coding tree unit;
• and
• in a case that the modified block vector is determined,
• utilizing, by the processor of the apparatus, the modified block vector as a predictor for encoding or decoding of a current block vector for the current prediction unit, or utilizing, by the processor of the apparatus, the modified block vector as the current block vector for the current prediction unit for IntraBC encoding or decoding of the current prediction unit.