Patent ID: 9681136
Date: 2017-06-13
CPC Classifications: H04N

Claim:
1. A coding method for coding a B frame on a block-by-block basis by adaptively switching between frame coding and field coding, the coding method comprising: determining a first maximum number of first frame indices and a second maximum number of second frame indices, the first maximum number indicating a maximum number of the first frame index for frame coding and the second maximum number indicating a maximum number of the second frame index for frame coding; generating first commands and second commands, the first commands indicating correspondence between the first frame indices and first reference frames, each of the first frame indices being an index for designating the first reference frame for a current block to be coded and the second commands indicating correspondence between the second frame indices and second reference frames, each of the second frame indices being an index for designating the second reference frame for the current block to be coded; adaptively switching, on a block-by-block basis, between frame coding and field coding; determining a maximum number of first field indices for field coding to be double a value of the first maximum number of the first frame indices, and determining a maximum number of second field indices for field coding to be double a value of the second maximum number of the second frame indices; (i) specifying a first reference index corresponding to the first reference frame for the current block to be coded and a second reference index corresponding to the second reference frame for the current block to be coded when frame coding is selected for the current block to be coded, the first and second reference frames being referred to when the current block is coded through motion compensation using frame coding, and (ii) specifying a first reference index corresponding to the first reference field for the current block to be coded and a second reference index corresponding to the second reference field for the current block to be coded when field coding is selected for the current block to be coded, the first and second reference fields being referred to when the current block is coded through motion compensation using field coding; and coding (i) the first maximum number and the second maximum number, (ii) the first reference index and the second reference index for the current block to be coded, and (iii) a prediction error for the current block to be coded, wherein said specifying of a first reference index corresponding to the first reference field and a second reference index corresponding to the second reference field includes: