Picture coding apparatus, picture decoding apparatus and the methods
A weighting factor mode determination unit determines whether to code an interlaced picture in a field mode or a frame mode, based on a value of a flag “AFF” indicating whether or not to switch between the field mode and the frame mode on a block-by-block basis and notifies switches and a multiplexing unit of the determined mode. The switches select either the field mode or the frame mode according to the notified mode. A field weighting factor coding unit or a frame weighting factor coding unit performs respectively the coding of respective weighting factors when the respective modes are selected.
1. A picture coding apparatus which codes a picture on a block-by-block basis, the picture coding apparatus comprising:
a motion compensation unit configured to generate, when performing frame coding on a block included in the picture, a predictive image using i) pixel values of a reference frame to which the block refers and ii) a frame weighting factor, and to generate, when performing field coding on the block, a predictive image using i) pixel values of a reference field to which the block refers and ii) a field weighting factor; and
a variable length coding unit configured to:
code the frame weighting factor and output a coded signal which includes i) a coded picture generated using the predictive image and ii) the coded frame weighting factor, when the picture has a frame structure and switching between the frame coding and the field coding is adaptively performed per block included in the picture;
code the frame weighting factor and output a coded signal which includes i) a coded picture generated using the predictive image and ii) the coded frame weighting factor, when the picture has a frame structure and the frame coding is performed on all blocks included in the picture; and
code the field weighting factor and output a coded signal which includes i) a coded picture generated using the predictive image and ii) the coded field weighting factor, when the picture has a field structure and the field coding is performed on all blocks included in the picture,
wherein the field weighting factor is generated from the frame weighting factor when the picture has the frame structure and the switching between the frame coding and the field coding is adaptively performed per block included in the picture, and
the field weighting factor and the frame weighting factor are coefficients used for calculating pixel values of the predictive image from pixel values of a reference picture.
2. A picture coding method for coding a picture on a block-by-block basis, the picture coding method comprising:
a motion compensation step of:
generating, when performing frame coding on a block included in the picture, a predictive image using i) pixel values of a reference frame to which the block refers and ii) a frame weighting factor; and
generating, when performing field coding on the block, a predictive image using i) pixel values of a reference field to which the block refers and ii) a field weighting factor; and
a variable length coding step of:
coding, using a variable length coding unit, the frame weighting factor and outputting a coded signal which includes i) a coded picture generated using the predictive image and ii) the coded frame weighting factor, when the picture has a frame structure and switching between the frame coding and the field coding is adaptively performed per block included in the picture;
coding the frame weighting factor and outputting a coded signal which includes i) a coded picture generated using the predictive image and ii) the coded frame weighting factor, when the picture has a frame structure and the frame coding is performed on all blocks included in the picture; and
coding the field weighting factor and outputting a coded signal which includes i) a coded picture generated using the predictive image and ii) the coded field weighting factor, when the picture has a field structure and the field coding is performed on all blocks included in the picture,
wherein the field weighting factor is generated from the frame weighting factor when the picture has the frame structure and the switching between the frame coding and the field coding is adaptively performed per block included in the picture, and
the field weighting factor and the frame weighting factor are coefficients used for calculating pixel values of the predictive image from pixel values of a reference picture.