Picture coding method and picture decoding method
View Patent ↗An image coding method and an image decoding method is provided by which an image can be restored correctly even if part of memory management information is lost by a transmission channel error, a candidate of a reference image that can be referred to is selected more appropriately, and coding efficiency is improved. The image coding method includes a step for executing coding of an image, a step for judging whether a picture in the memory which is never used as reference exists, a step for coding memory management information for releasing the picture in the memory which is never used as reference when a picture in the memory which is never used as reference exists, a step for releasing the picture in the memory which is never used as reference, a step for judging whether the memory management information that releases the picture in the memory which is never used as reference is coded by coding of an image immediately before, and a step for coding again the memory management information that releases the picture in the memory which is never used as reference when the memory management information is coded.
1. A decoding method for decoding a data stream, the data stream being obtained by coding a moving image including a plurality of pictures, wherein the data stream includes:
a coded first picture generated by coding a first picture,
coded management information data generated by coding first memory management information for managing a reference picture stored in a memory, the first memory management information being attached to the coded first picture, and
re-coded management information data generated by coding the first memory management information again as second memory management information, the second memory management information being attached to a second picture which is different from the first picture, said method comprising:
extracting the second memory management information; and
performing the following based on the extracted second memory management information: (i) releasing an area of a decoder memory which holds an unnecessary picture and which is therefore to be released, when the area has not yet been released, and (ii) executing no processing on the decoder memory when the area has already been released based on the first memory management information.
2. A picture decoding method for decoding a coded picture with reference to a reference picture selected from among reference pictures stored in a memory, wherein the memory includes (i) a short term memory that holds a reference picture for a short period of time and (ii) a long term memory that holds a reference picture for a longer period of time than the short term memory, said method comprising:
decoding memory management information for managing the reference pictures stored in the memory; and
performing the following based on the decoded memory management information: (i)
moving a reference picture to be moved from the short term memory to the long term memory, when the reference picture exists in the short term memory, and (ii) executing no moving of the reference picture when the reference picture does not exist in the short term memory.
3. A picture decoding apparatus that decodes a coded picture with reference to a reference picture selected from among reference pictures stored in a memory that includes (i) a short term memory that holds a reference picture for a short period of time and (ii) a long term memory that holds a reference picture for a longer period of time than the short term memory, said apparatus comprising:
a management information decoding unit operable to decode memory management information for managing the reference pictures stored in the memory; and
a memory management information control unit operable (i) to move, from the short term memory to the long term memory, a reference picture which is designated as a reference picture to be moved, by the memory management information decoded by the management information decoding unit, when the reference picture exists in the memory, and (ii) to execute no processing on the memory when the reference picture does not exist in the memory.
4. A decoding method for decoding a data stream, the data stream being obtained by coding a moving image including a plurality of pictures, wherein the data stream includes:
a coded first picture generated by coding a first picture,
coded management information data generated by coding first memory management information for managing a reference picture stored in a memory, the first memory management information being attached to the coded first picture, and
re-coded management information data generated by coding the first memory management information again as second memory management information, the second memory management information being attached to a second picture which is different from the first picture, said method comprising:
extracting the second memory management information;
judging whether or not a processing for managing a decoder memory based on the first memory management information has already been performed; and
(i) decoding the second picture when it is judged that the processing has already been performed, and (ii) decoding the second picture after performing the processing when it is judged that the processing has not yet been performed.
5. The picture decoding method according to claim 4 ,
wherein the first and second memory management information indicate to release all areas of the decoder memory in which reference pictures have been stored before said decoding of the first picture.
6. A computer readeable program stored on a recording medium, the program for causing an information processing apparatus to execute a picture decoding method for decoding a data stream, the data stream being obtained by coding a moving image including a plurality of pictures, wherein the data stream includes:
a coded first picture generated by coding a first picture,
coded management information data generated by coding first memory management information for managing a reference picture stored in a memory, the first memory management information being attached to the coded first picture, and
re-coded management information data generated by coding the first memory management information again as second memory management information, the second memory management information being attached to a second picture which is different from the first picture, and
wherein the picture decoding method includes:
extracting the second memory management information; and
performing the following based on the extracted memory management information: (i) releasing an area of a decoder memory which holds an unnecessary picture and which is therefore to be released, when the area has not yet been released, and (ii) executing no processing on the decoder memory when the area has already been released based on the first memory management information.