Method and apparatus for performing motion estimation in the DCT domain

Motion estimation apparatus for determining a motion vector between a current block and a reference block of a reference frame, the reference block being a block located in a search region of the reference picture that most closely matches the current block, the search region being divided into search region blocks, the apparatus comprising:

• an orthogonal transform module connected to receive the current block and operating to generate a current quadruple of transform coefficient blocks by orthogonally transforming the current block using DCT/DST transforms of a first type without prior zero padding of the current block;
• a processing module connected to receive the current quadruple from the orthogonal transform module, and additionally to receive a reference quadruple of transform coefficient blocks generated from four of the search region blocks, the processing module operating to generate a quadruple of processed transform coefficient blocks from the current quadruple and the reference quadruple;
• an inverse transform module connected to receive the quadruple of processed transform coefficient blocks from the processing module, and operating to generate a block of exact cross-correlations between the current block and the search region by inversely transforming the quadruple of processed transform coefficient blocks using inverse DCT/DST transforms of a second type;
• and
• a motion vector determining module connected to receive the block of exact cross-correlations and operating to determine the motion vector therefrom.

A computer-readable medium in which is fixed a computer program that instructs a computer to perform a motion estimation method that determines a motion vector between a current block and a reference block of a reference frame, the reference block being a block located in a search region of the reference picture that most closely matches the current block, the search region being divided into search region blocks, the motion estimation method comprising:

• orthogonally transforming the current block using DCT/DST transforms of a first type without prior zero padding of the current block to generate a current quadruple of transform coefficient blocks;
• processing the current quadruple together with a reference quadruple of transform coefficient blocks generated from four of the search region blocks to generate a quadruple of processed transform coefficient blocks;
• inversely transforming the quadruple of processed transform coefficient blocks using inverse DCT/DST transforms of a second type to generate a block of exact cross-correlations between the current block and the search region;
• and
• determining the motion vector from the block of exact cross-correlations.