According to an aspect of the disclosure, a method of video decoding for a decoder is provided. In the method, transform block signaling information is acquired from a coded video bitstream. In addition, a determination is made to determine whether the transform block signaling information indicates an implicit transform scheme, and at least one of a low-frequency non-separable transform (LFNST) and a matrix-based intra predication mode (MIP) is invalid. In response to the determination that the transform block signaling information indicates the implicit transform scheme, and at least one of the LFNST and MIP is signaled as invalid, a primary transform type is determined based on a size of a coding block unit (CU), and a primary transform is performed for a transform block that is partitioned from the CU in accordance with the determined primary transform type.