Image decoding method, image coding method, image decoding apparatus, image coding apparatus, and image coding and decoding apparatus
The image coding method includes: determining a context for a current block to be processed, from among a plurality of contexts; and performing arithmetic coding on the control parameter for the current block to generate a bitstream corresponding to the current block, wherein in the determining: the context is determined under a condition that control parameters of neighboring blocks of the current block are used, when the signal type is a first type, the neighboring blocks being a left block and an upper block of the current block; and the context is determined under a condition that the control parameter of the upper block is not used, when the signal type is a second type, and the second type is one of “mvd_l0” and “mvd_l1”.
1. A coding method for coding a control parameter for controlling coding of an image, the coding method comprising:
determining a context for a current block in the image, from among a plurality of contexts; and
performing arithmetic coding on the control parameter for the current block to generate a bitstream corresponding to the current block,
wherein the determining further includes:
determining a signal type under which the control parameter for the current block is classified;
determining the context by using both of coded control parameters for a left block and an upper block, when the signal type is a first type, 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
determining the context by using a predetermined fixed value, without using any coded control parameters for the left block and the upper block, when the signal type is a second type different from the first type,
wherein the control parameter determined as the first type belongs to the current block having a size larger than or equal to a size of a block to which the control parameter determined as the second type belongs,
wherein one of a split flag and a skip 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 the skip flag indicating whether or not the current block is to be skipped, and
wherein a difference parameter is classified under the second type, the difference parameter indicating a difference between a motion vector and a motion vector predictor of the current block.
2. A coding apparatus for coding a control parameter for controlling coding of 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 current block in the image, from among a plurality of contexts; and
performing arithmetic coding on the control parameter for the current block to generate a bitstream corresponding to the current block,
wherein the determining further includes:
determining a signal type under which the control parameter for the current block is classified;
determining the context by using both of coded control parameters for a left block and an upper block, when the signal type is a first type, 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
determining the context by using a predetermined fixed value, without using any coded control parameters for the left block and the upper block, when the signal type is a second type different from the first type,
wherein the control parameter determined as the first type belongs to the current block having a size larger than or equal to a size of a block to which the control parameter determined as the second type belongs,
wherein one of a split flag and a skip 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 the skip flag indicating whether or not the current block is to be skipped, and
wherein a difference parameter is classified under the second type, the difference parameter indicating a difference between a motion vector and a motion vector predictor of the current block.