A video data processing method comprises receiving input data associated with a current picture, determining a size for a current coding tree unit (CTU) or a current coding unit (CU) in the current CTU, and if the size, a width, or a height of the current CTU or CU is greater than a threshold, the encoder or decoder splits the current CTU or CU into multiple blocks until each block is not greater than the threshold. The current CTU or CU is processed for prediction or compensation and transform or inverse transform. The current CTU is processed according to CTU-level syntaxes signaled in a video bitstream. The encoder or decoder encodes or decodes the current CTU. The threshold corresponds to a maximum supported transform unit (TU) size for the encoder or decoder.