Apparatus and method for 2-D discrete transform using distributed arithmetic module

The present invention relates to a distributed arithmetic module employing a zero input detection circuit that reduces electric power consumption by avoiding unnecessary calculation. An apparatus for performing a discrete cosine transform (DCT) on a video signal, including; input unit for receiving the video signal in a block by block basis; discrete cosine transform (DCT) unit for receiving each image data block from the input unit and conducting a discrete cosine transform/inverse discrete cosine transform (DCT/IDCT) operation on the received image data block to generate a transformed image data block containing N×M pixel value; zero input detect unit for determining whether pixel values of a current image data block are all "0" and generating a detection signal in order to bypass the DCT/IDCT performing on the current image block; and output unit for outputting the transformed image data block as a transformed video signal.