Optimal frame memory and data transfer scheme for MPEG-4 shape coding

An optimal frame memory and data transfer scheme is proposed for MPEG-4 shape coding in embedded systems. The proposed alpha frame buffer scheme contains two approaches. First, a distributed tile-based memory organization is used to efficiently support the time-varying size of alpha plane. Second, a compression scheme is used to reduce the number of memory access to and the size of the alpha frame memory. Under the criteria of MPEG-4 standard, the size of alpha frame memory can be reduced to 50% by introducing a small index table (2.73%-5.08% of the original frame memory size). A coarse assessment shows that the number of memory reference can be reduced to 56.25%. On the other hand, the proposed data transfer scheme combines the run length coding and addressing mode to reduce average data transfer time to 9.39%. Therefore, the shared system bus can be kept as free as possible, which in turn leads to increasing the potentialities of improvement on system performance. Furthermore, this data transfer scheme also helps in accelerating the processing of shape coding.