Image decoding method including determining a context for a current block according to a signal type under which a control parameter for the current block is classified

A coding method for coding a control parameter for controlling coding of a current block in an image, the coding method comprising:

• determining a context for a control parameter of the current block, from among a plurality of contexts;
• and
• performing arithmetic coding on the control parameter for the current block, using the determined context to generate a bitstream corresponding to the current block,
• wherein the determining further includes:
• when the control parameter is a split flag, determining the context by using both of coded control parameters for a left block and an upper block, the left block being a neighboring block to the left of the current block, and the upper block being a neighboring block on top of the current block;
• and
• when the control parameter is chroma intra prediction information, determining the context by using a predetermined value, without using any coded control parameters for the left block and the upper block, and
• wherein (i) the split flag indicates whether or not the current block is partitioned into a plurality of blocks and (ii) the chroma intra prediction information indicates a chroma intra prediction mode used for intra prediction for chroma of the current block.

A coding apparatus for coding a control parameter for controlling coding of a current block in an image, the coding apparatus comprising:

• a context control unit configured to determine a context for a control parameter of the current block, from among a plurality of contexts;
• and
• an arithmetic coding unit configured to perform coding on the control parameter for the current block, using the determined context to generate a bitstream corresponding to the current block,
• wherein the context control unit is configured to:
• when the control parameter is a split flag, determine the context by using both of coded control parameters for a left block and an upper block, the left block being a neighboring block to the left of the current block, and the upper block being a neighboring block on top of the current block;
• and
• when the control parameter is chroma intra prediction information, determine the context by using a predetermined value, without using any coded control parameters for the left block and the upper block, and
• wherein (i) the split flag indicates whether or not the current block is partitioned into a plurality of blocks and (ii) the chroma intra prediction information indicates a chroma intra prediction mode used for intra prediction for chroma of the current block.

A coding apparatus for coding a control parameter for controlling coding of a current block in an image, the coding apparatus comprising:

• processing circuitry;
• and
• storage coupled to the processing circuitry;
• wherein the processing circuitry performs the following using the storage:
• determining a context for a control parameter of the current block, from among a plurality of contexts;
• and
• performing arithmetic coding on the control parameter for the current block, using the determined context to generate a bitstream corresponding to the current block,
• wherein the determining further includes:
• when the control parameter is a split flag, determining the context by using both of coded control parameters for a left block and an upper block, the left block being a neighboring block to the left of the current block, and the upper block being a neighboring block on top of the current block;
• and
• when the control parameter is chroma intra prediction information, determining the context by using a predetermined value, without using any coded control parameters for the left block and the upper block, and
• wherein (i) the split flag indicates whether or not the current block is partitioned into a plurality of blocks and (ii) the chroma intra prediction information indicates a chroma intra prediction mode used for intra prediction for chroma of the current block.