| 主权项 |
1. A coding and decoding system which includes a coding apparatus for coding each of plural pictures constituting a moving image and a decoding apparatus for decoding plural pictures constituting a moving image from a bit stream,
said coding apparatus comprises: a first and second information generating unit operable to generate, 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 coding at least one of 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 coding each of P pictures following the target picture; a third information generating unit operable to generate, on a block-by-block basis, (iii) third information indicating one specified reference picture to be referred to when performing predictive coding on a target block included in a target P picture; a fourth information generating unit operable to generate, on a picture-by-picture basis, (iv) fourth information indicating a plurality of candidate reference pictures, each of the candidate reference pictures being a candidate for a reference picture selected from among pictures for which only the first information is attached, when coding a target P picture; a first storing unit operable to store, on a picture-by-picture basis, the target picture into a memory as a candidate reference picture only when the first information is generated for the target picture by the first and second information generating unit; a coding unit operable to code, on a block-by-block basis, the target block by using the one specified reference picture; and a bit stream generating unit operable to generate a bit stream corresponding to the moving image, by adding the first information, the second information, the third information and the fourth information to coded block data generated by the coding unit, 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 coded with reference to the one specified reference picture, said decoding apparatus comprises: a first and second information extracting unit operable to extract, 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 of 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 unit operable to extract, 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 unit operable to extract, from the bit stream on a picture-by-picture basis, (iv) fourth information indicating a plurality of candidate reference pictures, each of the candidate reference pictures 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 second storing unit operable to store, on a picture-by-picture basis, the target picture into a memory as a candidate reference picture only when the first information is extracted by the first and second information extracting unit; and a decoding unit operable to decode, 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. |
