fig9 the decoder includes an idct downsampling unit 81 inverse discrete cosine transforming and filter downsampling the received dct coefficients to reduce from an 8 u00d7 8 inclusive of i p and b pictures to an 8 u00d7 4 block an adder 82 adding the 8 u00d7 4 downsampled data to a motion compensated data a classifier 83 classifying and separating the data from the adder 82 into i p and b pictures a format converting unit 84 converting the b picture of the 8 u00d7 4 data from the classifier 83 into a modified 4 2 0 format in which more vertical color signal information is included than horizontal color signal information a first and second data encoding unit 85 a and 85 b encoding the i and p pictures from the classifier 83 and the b picture from the format conversion unit 84 respectively a memory 86 including an anchor frame memory 86 a storing the i p picture information encoded by the first and second data encoding units 85 a and 85 b and a b frame memory 86 b storing the b picture information the decoder in fig9 further includes a first data decoding unit 87 decoding the data stored in the anchor frame memory 86 a a horizontal upsampling unit 88 horizontally upsampling the information decoded by the first data decoding unit 87 to convert into a 8 u00d7 8 size a motion compensated predictor 89 receiving an output of the horizontal upsampling unit 88 and performing both motion compensation and prediction using the motion vector information a horizontal downsampling unit 90 for horizontally downsampling and forwarding the output of the motion compensation predictor 89 into an 8 u00d7 4 size to.