Image coding method, image decoding method, image coding apparatus, image decoding apparatus, and image coding and decoding apparatus
An image coding method comprising: obtaining current signals to be coded of each of the processing units of the image; generating a binary signal by performing binarization on each of the current signals to be coded; selecting a context for each of the current signals to be coded from among a plurality of contexts; performing arithmetic coding of the binary signal by using coded probability information associated with the context selected in the selecting; and updating the coded probability information based on the binary signal, wherein, in the selecting, the context for the current signal to be coded is selected, as a shared context, for a signal which is included in one of a plurality of processing units and has a size different from a size of the processing unit including the current signal to be coded.
1. An image coding and decoding system comprising:
an image coding apparatus which compression-codes an image including a plurality of processing units having mutually different sizes; and
an image decoding apparatus which reconstructs a coded image including a plurality of processing units having mutually different sizes by decoding the coded image,
wherein the image coding apparatus comprises:
one or more memories; and
circuitry that executes operations comprising:
storing a plurality of contexts;
obtaining current signals to be coded included in the plurality of processing units of the image;
generating a binary signal by performing binarization on each of the current signals to be coded;
selecting a context for each of the current signals to be coded from among the plurality of contexts;
executing a coded probability information identification process for identifying coded probability information associated with the context selected in said selecting and an update process for updating, based on the binary signal, the coded probability information associated with the context selected in said selecting; and
performing arithmetic coding of the binary signal by using the coded probability information identified in said executing,
wherein a shared context is set in advance,
wherein in said selecting, the shared context is selected as the context for the current signal to be coded in the case where a size of the processing unit which includes the current signal to be coded is a block size of 16×16, and in the case where the size of the processing unit which includes the current signal to be coded is a block size of 32×32, and
wherein in said selecting, a dedicated context is selected as the context for the current signal to be coded in the case where the size of the processing unit which includes the current signal to be coded is smaller than the block size of 16×16, and
wherein the image decoding apparatus comprises:
one or more memories; and
circuitry that executes operations comprising:
storing the plurality of contexts;
selecting, from among the plurality of contexts, a context for each of current signals to be decoded included in the plurality of processing units of the coded image;
executing a decoded probability information identification process for identifying decoded probability information associated with the context selected in said selecting;
obtaining the current signals to be decoded;
generating the binary signal by performing arithmetic decoding of the current signals to be decoded by using the decoded probability information; and
reconstructing the image data by performing multi-value conversion on the binary signal,
wherein in said executing, an update process is executed for updating the decoded probability information identified in said executing based on the binary signal,
wherein the shared context is set in advance,
wherein in said selecting, the shared context is selected as the context for the current signal to be decoded in the case where a size of the processing unit which includes the current signal to be decoded is a block size of 16×16, and in the case where the size of the processing unit which includes the current signal to be decoded is a block size of 32×32, and
wherein in said selecting, the dedicated context is selected as the context for the current signal to be decoded in the case where the size of the processing unit which includes the current signal to be decoded is smaller than the block size of 16×16.