Efficient and flexible drift-free video bitstream switching at predictive frames

We propose an efficient and flexible coding scheme inspired by the SP picture technique in H.26L TML; it can achieve drift-free bitstream switching at predictive frames. Firstly, the proposed scheme improves the coding efficiency of the SP frames in H.26L TML by (1) reducing the number of quantization modules in the encoding path; (2) eliminating the mismatch between references for the prediction and the reconstruction; (3) outputting a high quality image for display purpose before the quantization step in the reconstruction loop. Secondly, the proposed scheme allows independent quantization parameters for up-switching and down-switching bitstreams. It can further reduce the switching bitstream size while keeping the coding efficiency of the normal bitstreams. It allows more rapid and frequent down-switching than up-switching. Furthermore, the size of the down-switching bitstream can be much smaller than that of the up-switching one. This is a very desirable feature for any TCP-friendly protocols currently used in most existing streaming systems.