IMAGE ENCODING APPARATUS, IMAGE DECODING APPARATUS, IMAGE ENCODING PROGRAM AND IMAGE DECODING PROGRAM

摘要

A bit stream comprising only I and P frames can be reproduced at a high speed without increasing the process amount nor degrading the picture quality. An expectation structure of the P frames of an encoded bit stream is modified, and a control part (112) is used to cause a variable length encoding part (105) to add and encode an expectation usage flag indicative of whether the P frames can be referred to from the following frames and a reference image number notified, as information indicative of the frame numbers referred to by the P frames, by a motion detecting part (111). The encoded image of a frame, in which the expectation usage flag is set up, is stored into a frame memory (109) and can be referred to during expecting and encoding the P frames. As a result, during decoding, the decoded image of the frame, in which the expectation usage flag is set up, in the input bit stream is stored into the frame memory, and the decoded image of the frame number indicated by the reference image number of each P frame is extracted from the frame memory and decoded for expectation.