Patent ID: 8155188

Claim:
A digital signal processor for decoding blocks of picture data included in a bit stream, the digital signal processor comprising: a memory; and a processor, connected to the memory, for: obtaining, from the bit stream including the blocks of picture data, a sequence of commands for respectively assigning frame-indices, used for frame decoding, to reference frames of the blocks of picture data; storing the frame-indices in the memory; adaptively switching, on a block-by-block basis, between frame decoding and field decoding; specifying, in a case where frame decoding is performed on a block of picture data, a reference frame, which is referred to when decoding the block of picture data, according to a reference index extracted from a coded block information area of the bit stream and according to a frame-index included in the assigned frame-indices; and in a case where field decoding is performed on the block of picture data: (i) generating a field-index for decoding the block of picture data using a frame-index stored in the memory, by (a) specifying two fields that make up a frame specified by frame-indices, (b) assigning a first value to one field, from among the specified two fields, having a parity that is the same as a parity of a field including a current block to be coded, the first value being obtained by doubling a value of the frame-indices, and (c) assigning a second value to another field having a parity that is different from the parity of the field including the current block, the second value being obtained by adding one to the first value; and (ii) specifying a reference field, which is referred to when decoding the block of picture data, according to the reference index extracted from the coded block information area of the bit stream and according to the generated field-index.