An apparatus for coding a block of a frame using intra-prediction includes a memory and a processor. The processor is configured to execute instructions stored in the memory to obtain an intra-prediction mode for coding the block of the frame; select a transform type for coding a transform block of a residual block, which results from predicting the block using the intra-prediction mode; and code the transform block using the transform type. To select the transform type includes to, in a case where the intra-prediction mode is a SMOOTH_PRED, select a ADST_ADST transform type; in a case where the intra-prediction mode is a SMOOTH_H_PRED, select a DCT_ADST transform type; and in a case where the intra-prediction mode is a SMOOTH_V_PRED, select a ADST_DCT transform type.