Picture signal coding and decoding.

摘要

Picture signal coding and decoding methods and apparatus are disclosed which eliminate such a situation that, when a coded picture signal of a high definition television system is thinned out to one half in each of the vertical and horizontal directions and displayed on a television receiver of a lower definition system, the displayed picture does not exhibit smooth motion due to the loss of an interlace structure. In an encoder, picture element data are processed by DCT processing to obtain 8 x 8 coefficient data, and the coefficient data are transmitted. In a decoder, of the 8 x 8 coefficient data, only 4 x 4 coefficient data at the left upper corner are sampled out and processed by IDCT processing to obtain original picture element data. In the IDCT processing, those of the 4 x 4 coefficient data which belong to the fourth row are replaced by those of the coefficient data of the eighth row of the 8 x 8 coefficient data.