In this paper, we propose a new seamless bitstream switching scheme to improve the coding performance ofH.264 SP-frames for rate adaptation. Our method removes one of the two requantization blocks in the SP-frame encoders so as to significantly improve coding performance. The seamless switching property of SP-frames is retained by properly restructuring the primary and secondary switching frame codecs. Experimental results show that our proposed scheme achieves close coding performance to that of regular H.264 P-frames and significantly better performance than that of SP-frames. The proposed method also provides the advantage ofusing a single secondary switching bitstream for both switching-up and switching-down processes.