In this thesis, the performance analysis of the H.264 decoder for decoding of high profile high definition data is done for the Pentium 4 processor and accordingly the optimization techniques based on single instruction multiple data and Windows based multithreading have been implemented. The comparison of optimized version of the H.264 decoder with the non-optimized version shows significant speed improvements after optimization thus making a contribution to the implementation of real-time decoding of high definition data encoded using H.264 high profile encoder.