A decoder for a digital audiovisual transmission system, the decoder comprising a processor means for decompressing and displaying compressed still picture data and a memory (66, 67) characterised in that the memory (66, 67) comprises a storage memory (66) allocated to receive from the processor decompressed digital image data representing a plurality of still picture images (63, 64, 65) and at least one display memory (67) adapted to hold contemporaneously data representing multiple still picture images (68, 69, 70, 71) readable by the processor means prior to display, data representing the plurality of images being copied from the storage memory (66) to the display memory (67) for subsequent display.