Abstract: The image decoding method includes: determining a context for use in a current block to be processed, from among a plurality of contexts; and performing arithmetic decoding on a bit sequence corresponding to the current block, using the determined context, 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 “ref_idx_l0” and “ref_idx_l1”.

Abstract: A method of encoding video including: writing a plurality of predetermined buffer descriptions into a sequence parameter set of a coded video bitstream; writing a plurality of updating parameters into a slice header of the coded video bitstream for selecting and modifying one buffer description out of the plurality of buffer descriptions; and encoding a slice into the coded video bitstream using the slice header and the modified buffer description.

Abstract: An image coding method includes: deriving a candidate for a motion vector of a current block from a co-located motion vector; adding the candidate to a list; selecting the motion vector of the current block from the list; and coding the current block, wherein the deriving includes: deriving the candidate by a first derivation scheme in the case of determining that each of a current reference picture and a co-located reference picture is a long-term reference picture; and deriving the candidate by a second derivation scheme in the case of determining that each of the current reference picture and the co-located reference picture is a short-term reference picture.

Abstract: An image decoding method of decoding, on a block-by-block basis, image data included in a coded stream includes: deriving candidates for an intra prediction mode to be used for intra prediction for a decoding target block, the number of the candidates constantly being a plural number; obtaining, from the coded stream, an index for identifying one of the derived candidates for the intra prediction mode; and determining, based on the obtained index, one of the derived candidates for the intra prediction mode as the intra prediction mode to be used for intra prediction for the decoding target block.

Abstract: A decoder, encoder, and a recording medium causes a processor to generate a prediction image by an inter prediction process by i) obtaining first information from a bitstream associated with a variable number of feature points of a current block usable in performing an affine prediction, ii) obtaining a flag from the bitstream indicating a first or second value, iii) obtaining second information from the bitstream specifying first points in response to the flag indicating the first value, iv) determining third information provided the first points based on the second information and indicating a difference between coordinate values of a first point and a corresponding second point included in a reference picture, v) generating a prediction image of the current block according to the determined third information, and vi) refraining from obtaining the second information from the bitstream, in response to the flag indicating the second value.

Abstract: 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.

Abstract: The image coding method includes: determining a context in 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 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 (i) “merge_flag”, (ii) “ref_idx_l0” or “ref_idx_l1”, (iii) “inter_pred_flag”, (iv) “mvd_l0” or “mvd_l1”, (v) “no_residual_data_flag”, (vi) “intra_chroma_pred_mode”, (vii) “cbf_luma”, and (viii) “cbf_cb” or “cbf_cr”.

Abstract: An image coding method includes: deriving a candidate for a motion vector predictor from a co-located motion vector; adding the candidate to a list; selecting the motion vector predictor from the list; and coding a current block and coding a current motion vector, wherein the deriving includes: deriving the candidate by a first derivation scheme in the case of determining that each of a current reference picture and a co-located reference picture is a long-term reference picture; and deriving the candidate by a second derivation scheme in the case of determining that each of the current reference picture and the co-located reference picture is a short-term reference picture.

Abstract: An image coding method includes: selecting a first picture from plural pictures; setting a first temporal motion vector prediction flag which is associated with the first picture and is a temporal motion vector prediction flag indicating whether or not temporal motion vector prediction is to be used, to indicate that the temporal motion vector prediction is not to be used, and coding the first temporal motion vector prediction flag; coding the first picture without using the temporal motion vector prediction; and coding a second picture which follows the first picture in coding order, with referring to a motion vector of a picture preceding the first picture in coding order being prohibited.

Abstract: A picture coding method includes: performing a first derivation process for deriving a first merging candidate which includes a candidate set of a prediction direction, a motion vector, and a reference picture index for use in coding of a current block; performing a second derivation process for deriving a second merging candidate; selecting a merging candidate to be used in the coding of the current block from among the first and second merging candidates; and attaching an index for identifying the selected merging candidate to the bitstream; wherein the first derivation process is performed so that a total number of the first merging candidates does not exceed a predetermined number, and the second derivation process is performed when the total number of the first merging candidates is less than a predetermined maximum number of merging candidates.

Abstract: A moving picture coding method includes (i) transforming, for each of one or more second processing units included in the first processing unit, a moving picture signal in a spatial domain into a frequency domain coefficient and quantizing the frequency domain coefficient, and (ii) performing arithmetic coding on a luminance CBF flag indicating whether or not a quantized coefficient is included in the second processing unit in which transform and quantization are performed, wherein, in the arithmetic coding, a probability table for use in arithmetic coding is determined according to whether or not the size of the first processing unit is identical to the size of the second processing unit and whether or not the second processing unit has a predetermined maximum size.

Abstract: An image coding method includes: writing, into a sequence parameter set, buffer description defining information for defining a plurality of buffer descriptions; selecting one of the buffer descriptions for each processing unit that is a picture or a slice, and writing buffer description selecting information for specifying the selected buffer description, into a first header of the processing unit which is included in the coded bitstream; and coding the processing unit using the selected buffer description, and the buffer description defining information includes long-term information for identifying, among a plurality of reference pictures indicated in the buffer descriptions, a reference picture to be assigned as a long-term reference picture.

Abstract: The image decoding method includes determining a context for use in a current block to be processed, from among a plurality of contexts, wherein in the determining: the context is determined under a condition that control parameters of a left block and an upper block are used, when the signal type is a first type; and the context is determined under a third condition that the control parameter of the upper block is not used and a hierarchical depth of a data unit to which the control parameter of the current block belongs is used, when the signal type is a third type, and the third type is one or more of (i) “merge_flag”, (ii) “ref_idx_l0” or “ref_idx_l1”, (iii) “inter_pred_flag”, (iv) “mvd_l0” or “mvd_l1”, (v) “intra_chroma_pred_mode”, (vi) “cbf_luma”, and (vii) “cbf_cb” or “cbf_cr”.

Abstract: An image encoding method including: a constraint information generating step of generating tile constraint information indicating whether or not there is a constraint in filtering on boundaries between adjacent tiles among a plurality of tiles obtained by dividing a picture, and storing the tile constraint information into a sequence parameter set; and a filter information generating step of generating, for each of the boundaries, one of a plurality of filter information items respectively indicating whether or not filtering is executed on the boundaries, and storing the plurality of filter information items into a plurality of picture parameter sets, wherein, in the filter information generating step, the plurality of filter information items which indicate identical content are generated when the tile constraint information indicates that there is the constraint in the filtering.

Abstract: A method of encoding video including: writing a plurality of predetermined buffer descriptions into a sequence parameter set of a coded video bitstream; writing a plurality of updating parameters into a slice header of the coded video bitstream for selecting and modifying one buffer description out of the plurality of buffer descriptions; and encoding a slice into the coded video bitstream using the slice header and the modified buffer description.

Abstract: An image coding method of coding an image on a per coding unit basis, the method comprising: applying a frequency transform to luminance data and chrominance data of transform units in the coding unit including predetermined blocks each corresponding to one or more of the transform units; and coding the luminance data and the chrominance data to which the frequency transform has been applied to generate a bitstream in which the luminance data and the chrominance data are grouped on a per predetermined block basis.

Abstract: A decoder includes a memory and a processor coupled to the memory. The processor is configured to obtain first information from a bitstream, the first information indicating a number of first points in a current picture. The processor is also configured to determine second information provided for each of the first points based on the first information, the second information indicating a difference between a coordinate value of a first point and a coordinate value of a corresponding second point, the corresponding second point being included in a reference picture. The processor is further configured to generate a prediction image of a current block by performing an affine prediction according to the determined second information.

Abstract: An image decoding method of decoding, on a block-by-block basis, image data included in a coded stream includes: deriving candidates for an intra prediction mode to be used for intra prediction for a decoding target block, the number of the candidates constantly being a plural number; obtaining, from the coded stream, an index for identifying one of the derived candidates for the intra prediction mode; and determining, based on the obtained index, one of the derived candidates for the intra prediction mode as the intra prediction mode to be used for intra prediction for the decoding target block.

Abstract: 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.

Abstract: A processor obtains pieces of coded data, which are included in a bitstream and generated by coding tiles, and tile boundary independence information, which indicates whether each boundary between the tiles is a first or second boundary. Image data of a first tile is generated by decoding a first code string included in first coded data with reference to decoding information of a decoded tile when the tile boundary independence information indicates the first boundary, and by decoding the first code string without referring to the decoding information when the tile boundary independence information indicates the second boundary. A bit string is added after the first code string to make a bit length of first coded data a multiple of a predetermined N bits, with N being an integer greater than or equal to 2.