MPEG-2 video decoder for DVD
A video decoder with an efficient controller scheme and a sub-picture decoder for DVD application is presented in this paper. Most of the reported architecture for MPEG2 video decoding uses a 64 bit bus and a complex bus arbitration scheme. Our design uses synchronous DRAMs instead of standard EDO DRAMs and involves a novel controller scheme that allocates bus space for DRAM access efficiently. This efficient allocation allows us to reduce bus width from 64 bits to 32 bits, without significantly increasing embedded buffer sizes, and still meeting the requirements for MPEG2 MP/ML decoding. The bus arbitration algorithm is also simple allowing for a less complex controller design. Our main strategy is to impose a certain order in the DRAM access by the various processes instead of allowing any process to request for bus access arbitrarily. We also take advantage of the restricted GOP (group of picture) sequence in the DVD format to allow a longer decoding time for B frames. The sub-picture pixel data are run-length compressed bitmaps that are overlayed on top of the MPEG reconstruction video. The architecture for sub-picture decoding is simple and easy to implement.