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 decoding apparatus for decoding a control parameter for controlling decoding of a current block in an image, the decoding 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 decoding unit configured to perform arithmetic decoding on a bitstream corresponding to the current block, using the determined context to obtain the control parameter for the current block,
• wherein the context control unit is configured to:
• determine a signal type under which the control parameter for the current block is classified;
• for the signal type of a first type, 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
• for the signal type of a second type different from the first type, 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 is classified under the first type, the split flag indicating whether or not the current block is partitioned into a plurality of blocks and (ii) the chroma intra prediction information is classified under the second type, the chroma intra prediction information indicating a chroma intra prediction mode used for intra prediction for chroma of the current block.

A decoding apparatus for decoding a control parameter for controlling decoding of a current block in an image, the decoding 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 decoding on a bitstream corresponding to the current block, using the determined context to obtain the control parameter for the current block, wherein the determining further includes:
• determining a signal type under which the control parameter for the current block is classified;
• for the signal type of a first type, 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
• for the signal type of a second type different from the first type, 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 is classified under the first type, the split flag indicating whether or not the current block is partitioned into a plurality of blocks and (ii) the chroma intra prediction information is classified under the second type, the chroma intra prediction information indicating a chroma intra prediction mode used for intra prediction for chroma of the current block.