A recent dynamic increase in demand for wireless multimedia services has greatly accelerated the research on cross layer optimization techniques for transmitting multimedia data over wireless channel. In this paper, we explore a novel theoretical approach for joint optimization between the rate distortion (RD) of H.264/AVC video and the link-capacity of MIMO parallel subchannels. We obtain the optimal power level of subchannels through an optimization problem to minimize total visual distortion. In the simulation results, compared to the water filling (WF) method, the proposed scheme provides better results in aspects of visual quality in the face of sum rate loss.