Patent ID: 8213517

Claim:
A decoding method for decoding plural pictures constituting a moving image from a bit stream, the decoding method comprising: a first and second information extracting step of extracting, using a first and second information extracting unit, from the bit stream on a picture-by-picture basis, either of (i) first information indicating that a target picture, which is either an I picture or a P picture, can be a reference picture to be referred to when decoding at least one P pictures following the target picture and (ii) second information indicating that the target picture cannot be a reference picture to be referred to when decoding each of P pictures following the target picture; a third information extracting step of extracting, from the bit stream on a block-by-block basis, (iii) third information indicating one specified reference picture to be referred to when performing predictive decoding on a target block included in a target P picture; a fourth information extracting step of extracting, from the bit stream on a picture-by-picture basis, (iv) fourth information indicating a plurality of candidate reference pictures, the candidate reference picture being a candidate for a reference picture selected from among pictures for which only the first information is attached, when decoding a target P picture; a storing step of storing, on a picture-by-picture basis, the target picture into a memory as a candidate reference picture only when the first information is extracted in the first and second information extracting step; and a decoding step of decoding, on a block-by-block basis, the target block by using the one specified reference picture, wherein the one specified reference picture is specified on a block-by-block basis, from among a plurality of candidate reference pictures which are stored in the memory, and the target block is predictively decoded with reference to the one specified reference picture.