p u2212 frame due to some type of error or conversely if a p u2212 frame is decoded as a p frame the correct prediction image is not synthesized in the decoder and the quality of the decoded image deteriorates after synthesizing the prediction image the operation returns to fig1 and the quantized dct coefficients is input in 1108 inverse quantization and inverse dct is then applied to these coefficients and the resulting image is stored in frame memory e in 1109 it is checked again whether the frame currently being decoded is an i frame if the current frame is not an i frame images stored in frame memory d and e are added in 1110 and the resulting sum image is stored in frame memory e the image stored in frame memory e before starting the process in 1111 is the reconstructed image this image stored in frame memory e is output to the output frame memory for instance 706 in fig7 in 1111 and then output from the decoder as the reconstructed image the decoding process for a frame is completed here and the process for the next frame starts by returning to 1102 when a software based on the flowchart shown in fig8 12 is run in the software.