Abstract: A decoding method and apparatus for decoding compressed main data and, after that, outputting the decoded main data with other data being superposed thereon. The decoding apparatus consists of an input unit for inputting the compressed main data, a memory unit for storing compressed sub data, a switch unit for selecting and outputting the compressed main data and the compressed sub data at a predetermined timing, a decoding unit for decoding the compressed main data and the compressed sub data which are outputted from the switch unit, and a superposition unit for outputting the decoded main data and the decoded sub data in superposition.

Abstract: An image data conversion method and apparatus capable of real time output of moving pictures and simplifying the control circuit. This apparatus includes a central processing unit (CPU) for decoding compressed data and transferring the decoded data at the same line frequency as that of a receiver, and an image inverse-conversion processor for converting the data transferred from the CPU to an image size that can be displayed on the receiver. The CPU controls the decoded data so that it is decimated by eliminating predetermined lines so as to have the same number of lines as that of the receiver displaying apparatus, and be transferred to the image inverse-conversion processor. The image inverse-conversion processor includes a converter circuit common to the conversion to odd and even fields.