Thesupport for region of interest (ROI) browsing, which allows dropping background part of video bitstreams, is a desirable feature\nfor video applications. With the help of the slice group technique provided by H.264/SVC, rectangular ROI areas can be encoded\ninto separate ROI slices. Additionally, by imposing certain constraints on motion estimation, ROI part of the bitstream can be\ndecoded without background slices of the same layer. However, due to the additional spatial and temporal constraints applied to\nthe encoder, overall coding efficiency would be significantly decreased. In this paper, a rate-distortion optimized (RDO) encoding\nscheme is proposed to improve the coding efficiency of ROI slices.When background slices are discarded, the proposed method uses\nbase layer information to generate the prediction signal of the enhancement layer.Thus, the temporal constraints can be loosened\nduring the encoding process. To do it in this way, the possible mismatch between generated reference frames and original ones\nis also considered during rate-distortion optimization so that a reasonable trade-off between coding efficiency and decoding drift\ncan be made. Besides, a new Lagrange multiplier derivation method is developed for further coding performance improvement.\nExperimental results demonstrate that the proposed method achieves significant bitrate saving compared to existing methods.
Loading....