Abstract: A hybrid video encoder which carries out motion estimation and compensation (8) in the transform domain. In such an encoder, the calculation of a prediction block (Ŷ) from previously encoded blocks (Z) stored in the transform-domain frame memory (7) requires a large number of multiplications. This applies particularly to the motion estimation algorithm. In accordance with the invention, only a few DCT coefficients of candidate prediction blocks are calculated, for example, the DC coefficient and some AC coefficients. In a preferred embodiment, the AC coefficients are adaptively selected in dependence upon the motion vector which is being considered. The calculated coefficients of the candidate prediction blocks and the corresponding coefficients of the current input picture block (Y) are then compared to identify the best-matching prediction block.

Abstract: A hybrid video encoder which carries out motion estimation and compensation (8) in the transform domain. In such an encoder, the calculation of a prediction block (Ŷ) from previously encoded blocks (Z) stored in the transform-domain frame memory (7) requires a large number of multiplications. This applies particularly to the motion estimation algorithm. In accordance with the invention, only a few DCT coefficients of candidate prediction blocks are calculated, for example, the DC coefficient and some AC coefficients. In a preferred embodiment, the AC coefficients are adaptively selected in dependence upon the motion vector which is being considered. The calculated coefficients of the candidate prediction blocks and the corresponding coefficients of the current input picture block (Y) are then compared to identify the best-matching prediction block.