Thread migration (TM) is a recently proposed dynamic power management technique for heterogeneous multi-processor system-on-chip (MPSoC) platforms that eliminates the area and power overheads incurred by fine-grained dynamic voltage and frequency scaling (DVFS) based power management. In this paper, we take the first step towards formally analyzing and experimentally evaluating the use of power-aware TM for parallel data streaming applications on MPSoC platforms. From an analysis perspective, we characterize the optimal mapping of threads to cores and prove the convergence properties of a complexity effective greedy thread swapping based TM algorithm to the globally optimal solutions. The proposed techniques are evaluated on a 9-core FPGA based MPSoC prototype equipped with fully-functional TM and DVFS support, and running a parallelized video encoding benchmark based on the MPEG standard. Our experimental results validate the proposed theoretical analysis, and show that the proposed TM algorithm provides within $8\%$ of the performance of DVFS within the same power budget assuming no overheads for DVFS. Assuming voltage regulator inefficiency of $80\%$, the proposed TM algorithm has $9\%$ higher performance than DVFS, again assuming the same total power budget.