Patent ID: 8406306

Claim:
An image decoding apparatus which decodes a coded stream using motion compensation, said image decoding apparatus comprising: an arithmetic decoding unit configured to perform arithmetic decoding on the coded stream, obtain at least motion related information which relates to a motion vector used in coding, and generate binary data resulting from the arithmetic decoding; a memory which accumulates (i) the binary data in a first buffer and (ii) a reference picture in a second buffer, the reference picture being a decoded picture which is to be used in motion compensation; a reference area specifying unit configured to specify a part of pixel data of the reference picture accumulated in said second buffer, based on the motion related information obtained by said arithmetic decoding unit; a reference pixel buffer which is readable faster than said memory; a reference-pixel-reading control unit configured to copy the part of pixel data specified by said reference area specifying unit, from said memory to said reference pixel buffer; and a decoding unit configured to perform decoding to generate, on a predetermined block-by-block basis, decoded pixel data using motion compensation, using (i) the pixel data which is specified based on the motion vector and is read from said reference pixel buffer and (ii) the binary data accumulated in said first buffer, wherein said reference area specifying unit is configured to specify at least the pixel data to be used in motion compensation on a current block to be decoded, prior to the decoding of the current block performed by said decoding unit, and said reference-pixel-reading control unit is configured to, prior to the motion compensation in the decoding, read, from said second buffer, the pixel data specified by said reference area specifying unit to copy the read pixel data to said reference pixel buffer.