| 摘要 |
A bitstream comprising only I and P frames can be reproduced at a high speed without increasing the process amount nor degrading the picture quality. A prediction structure of the P frames of a coded bitstream is modified, and a control unit ( 112 ) is used to cause a variable length coding unit ( 105 ) to add and code a prediction 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 detection unit ( 111 ). The coded image of a frame, in which the prediction usage flag is set up, is stored in a frame memory ( 109 ) and can be referred to during predicting and coding the P frames. As a result, during decoding, the decoded image of the frame, in which the prediction usage flag is set up, in the input bitstream is stored in 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 prediction.
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