The present invention relates to a moving picture decoding apparatus, and especially, to a moving picture decoding apparatus capable of reducing a necessary capacity of a frame memory to be used when coded moving pictures are decoded.
Conventionally, this kind of a moving picture decoding apparatus is used in a method for reducing a necessary frame memory capacity used in the decoding process. As the conventional moving picture decoding apparatus, JP-A-261635/1997, for example, discloses an arrangement for reducing a frame memory capacity necessary for storage or reference images and re-ordering decoded images, which comprises a data compression circuit for compressing a decoded image and a data expansion circuit for expanding compressed data. Also, in JP-A-247673/1997, an arrangement is proposed in which a set of moving pictures data of which data content has been reduced by data content reducing means for reducing data content of data read from the frame memory is restored by data content restoring means.
Also, in JP-A-4550/1998, for example, an apparatus is proposed in which a reduction in memory use capacity is facilitated using Adaptive Differential Pulse Code Modulation (ADPCM). In the apparatus described in the publication, compression is conducted by estimating a change in each block of n×m pixels compressed using orthogonal translation, encoding a first pixel of each block with p bits in accordance with the ADPCM method, encoding an estimated value of the change with n×h bits, and further, encoding a difference value between each pixel following the first pixel and an average value of all pixels in the block with p−k bits.
However, in the conventional moving picture decoding apparatus proposed in the above-described JP-A-4550/1998 and so forth, in which the objective is to reduce the capacity of frame memory used, there is a problem in that efficient access to the memory cannot be realized.
The reason for this is that an access width of the memory is not taken into account in a memory compression and expansion section of the above-described moving picture decoding apparatus.