1. A method for dynamically determining frames required to build a complete picture in an MPEG video stream comprising: decoding an order of frames in the MPEG video stream according to a dependency vector model, the dependency vector model being configured for determining a dependency vector as a function of the decode order video stream for seamless operation over several types of MPEG streams; and performing frame accurate representations of the MPEG stream in a bidirectional fashion as a function of the dependency vector determined according to the dependency vector model.