To improve encoding efficiency by selecting an appropriate orthogonal transformation mode and encoding an interlaced image signal in the encoding of the interlaced image signal.
Macroblocks inputted from an input terminal 10 are divided into intra-frame orthogonal transformation blocks to be orthogonally transformed. The macroblocks inputted at the same time are also divided into intra-field orthogonal transformation blocks to be orthogonally transformed. Then, prescribed coefficient data are selected from among orthogonally transformed coefficient data and made to be absolute values in each mode. The maximum value is detected from among the absolute values to be a representative value in each mode. A mode determining means 17 weights representative values of the respective modes, compares the representative values, selects the smaller mode and outputs a mode determination result.
FUJII SHOZO
OKA HIDEMI
