Data holding apparatus

A data holding apparatus used for image processing in which an image is coded or decoded, on a macroblock basis, based on a field structure or a frame structure selected on a macroblock pair basis, said data holding apparatus comprising:

• a current register which holds a parameter set of a current macroblock to be coded or decoded;
• and
• registers which respectively hold parameter sets of macroblocks having neighboring relationships with the current macroblock,
• wherein at least one of said registers selectively holds, in sequence, parameter sets of respective different macroblocks having the neighboring relationships, one parameter set at a time,
• wherein the current macroblock repeats a first transition and a second transition alternately,
• the first transition is a transition of the current macroblock from a top macroblock to a bottom macroblock in a macroblock pair,
• the second transition is a transition of the current macroblock from a bottom macroblock in a macroblock pair to a top macroblock in a right neighboring macroblock pair,
• a parameter set includes parameters common to two macroblocks in a macroblock pair and parameters specific to each of the two macroblocks,
• said current register comprises:
• a common register which holds the common parameters;
• and a specific register which holds the specific parameters, and
• said data holding apparatus further comprises a switch which turns off to stop data input into said common register at the first transition and turns on to allow data input at the second transition,
• wherein said registers include:
• a first register which selectively holds one of a parameter set of a top macroblock in an above neighboring macroblock pair with respect to the current macroblock, and a parameter set of a top macroblock in a current macroblock pair containing the current macroblock;
• a second register which holds a parameter set of a bottom macroblock in the above neighboring macroblock pair with respect to the current macroblock;
• a third register which holds a parameter set of a top macroblock in a left neighboring macroblock pair with respect to the current macroblock;
• and
• a fourth register which holds a parameter set of a bottom macroblock in the left neighboring macroblock pair with respect to the current macroblock,
• wherein said first register holds the parameter set of the top macroblock in the current macroblock pair when the current macroblock is a bottom macroblock in the current macroblock pair, and the parameter set of the top macroblock in the above neighboring macroblock pair when the current macroblock is a top macroblock in the current macroblock pair.