Bit plane coding apparatus

A bit plane coding apparatus for dividing a data group including plural data with their absolute value components expressed by n bits (n being a natural number) into at least one or more blocks and coding each of the blocks by bit plane, the bit plane coding apparatus comprising:

• bit plane search means for searching each block for the most significant bit plane of bit planes including a bit having a valid value (valid bit),
• the bit plane search means comprising:
• a storage unit for storing bit position specifying information specifying one bit position of the n bits in association with each block of the data group;
• and
• an update control unit to which an absolute value component of each data constituting the data group is inputted and which updates the bit position specifying information stored in the storage unit every time an absolute value component is inputted,
• wherein the update control unit reads out bit position specifying information of a block to which the inputted absolute value component belongs, from the storage unit, then compares a bit position indicated by the bit position specifying information with a bit position of the most significant valid bit of the inputted absolute value component and selects the higher bit position, and updates the bit specifying information of the block in the storage unit to a content specifying the selected bit position, and
• the storage unit outputs the bit position specifying information after the end of update with respect to the absolute value components of all the data constituting the data group, as the most significant bit plane of the bit planes including a valid bit.