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 decoding apparatus which decodes, on a block-by-block basis, a picture that is coded and included in a coded signal, the picture decoding apparatus comprising:
a variable length decoding unit configured to:
decode a frame weighting factor that is coded and included in the coded signal, and to generate a field weighting factor from the decoded frame weighting factor, in the case where the picture has a frame structure and is coded such that switching between frame coding and field coding of a block included in the picture is adaptively performed;
decode a frame weighting factor that is coded and included in the coded signal, in the case where the picture has a frame structure and is coded such that frame coding is performed on all blocks included in the picture; and
decode a field weighting factor that is coded and included in the coded signal, in the case where the picture has a field structure and is coded such that field coding is performed on all blocks included in the picture;
a motion compensation unit configured to:
generate a predictive image by scaling pixel values of a reference frame to which the block refers using the decoded frame weighting factor, in the case where the picture has a frame structure and is coded such that switching between frame coding and field coding of a block included in the picture is adaptively performed and the block included in the picture is frame coded, and to generate a predictive image by scaling pixel values of a reference field to which the block refers using the generated field weighting factor, in the case where the picture has a frame structure and is coded such that switching between frame coding and field coding of a block included in the picture is adaptively performed and the block is field coded;
generate a predictive image by scaling pixel values of a reference frame to which the block refers using the decoded frame weighting factor, in the case where all blocks included in the picture is frame coded; and
generate a predictive image by scaling pixel values of a reference field to which the block refers using the decoded field weighting factor, in the case where all blocks included in the picture is field coded; and
an adding unit configured to reconstruct the picture using the generated predictive image.
2. A picture decoding method which decodes, on a block-by-block basis, a picture that is coded and included in a coded signal, the picture decoding method comprising:
a variable length decoding step, performed by a variable length decoding unit, of:
decoding a frame weighting factor that is coded and included in the coded signal, and generating a field weighting factor from the decoded frame weighting factor, in the case where the picture has a frame structure and is coded such that switching between frame coding and field coding of a block included in the picture is adaptively performed;
decoding a frame weighting factor that is coded and included in the coded signal, in the case where the picture has a frame structure and is coded such that frame coding is performed on all blocks included in the picture; and
decoding a field weighting factor that is coded and included in the coded signal, in the case where the picture has a field structure and is coded such that field coding is performed on all blocks included in the picture; and
a motion compensation step, performed by a motion compensation unit, of:
generating a predictive image by scaling pixel values of a reference frame to which the block refers using the decoded frame weighting factor, in the case where the picture has a frame structure and is coded such that switching between frame coding and field coding of a block included in the picture is adaptively performed and the block included in the picture is frame coded, and generating a predictive image by scaling pixel values of a reference field to which the block refers using the generated field weighting factor, in the case where the picture has a frame structure and is coded such that switching between frame coding and field coding of a block included in the picture is adaptively performed and the block is field coded;
generating a predictive image by scaling pixel values of a reference frame to which the block refers using the decoded frame weighting factor, in the case where all blocks included in the picture is frame coded; and
generating a predictive image by scaling pixel values of a reference field to which the block refers using the decoded field weighting factor, in the case where all blocks included in the picture is field coded; and
an adding step, performed by an adding unit, of reconstructing the picture, using the generated predictive image.