Patent ID: 8345992

Claim:
An image encoding method in an image encoding device which gets inputted image data and conducts an encoding of the image data by a predetermined pixel block unit selectively using intra-frame prediction or inter-frame prediction in which a difference between a reference picture and the image data is encoded, wherein the image encoding device performs the steps of: setting an output availability parameter indicating a specific range of past pictures where the image data can be fully and certainly decoded to be outputted if all past pictures fall within the range has been decoded when decoding the image data which has been encoded by the image encoding method; calculating, for each target block in the image data to be encoded, influenced range indicating a range within which pictures encoded in the past influence the target block, during encoding the target block; and controlling a range of the reference picture at encoding so that the calculated influenced range does not exceed the image output availability parameter, wherein the step of controlling includes the sub-steps of: when the inter-frame prediction is selected and the influenced range exceeds the output availability parameter, changing a prediction area to which the target block refers; when the influenced range still exceeds the output availability parameter despite changing the prediction area, performing intra-frame prediction for the target block.