A method of decoding a bitstream by an electronic device is provided. A block unit is determined from an image frame received from the bitstream. An intra prediction mode index corresponding to one of wide-angle candidate modes is determined for the block unit. The electronic device determines whether the intra prediction mode index is different from predefined indices each corresponding to one of predefined wide-angle modes in the wide-angle candidate modes. Filtered samples are generated based on reference samples neighboring the block unit. The filtered samples are generated by an interpolation filter when the intra prediction mode index is different from the predefined indices. The filtered samples are generated by a reference filter when the intra prediction mode index is equal to at least one of the predefined indices. The block unit is reconstructed based on the filtered samples along a mode direction of the intra prediction mode index.