The cost of data dependence in motion vector estimation for reconfigurable platforms

Motion vector estimation is frequently performed as a prelude to the exploitation of temporal redundancies in video applications. As a result, a large volume of work has been done to develop techniques to avoid the heavy memory access requirements of full search motion vector estimation. Often, these approaches introduce data dependence to the algorithm, leading to memory accesses which cannot be determined at design time. Consequently, this complicates the exploitation of data reuse in hardware. In this work, the cost of data dependence is quantified. Experiments indicate that a data dependent fast motion vector estimation approach is faster than full search by up to 47% in the absence of data re-use optimisation. However, full search is approximately 16 times faster than the `fast' motion vector estimation algorithm when a static line buffering scheme and a parallel caching scheme are used respectively to exploit data re-use. Therefore, it is established that data dependence in motion vector estimation is very expensive in terms of hardware performance