The design and implementation of a software decoder for MPEG video bitstreams is described. The software has been ported to numerous platforms including PC''s, workstations, and mainframe computers. Performance comparisons are given for several different bitstreams and platforms including a unique metric devised to compare price/performance across different platforms (percentage of required bit rate per dollar). We also show that memory bandwidth is the primary limitation in performance of the decoder, not the computational complexity of the inverse discrete cosine transform as is commonly thought.