To solve the problem that some area deforms too large and large volume of redundant data in the process of panoramic video mapping, a Double-Ring mapping Projection (DRP) algorithm was proposed. Firstly, according to the geometric characteristics of spherical video and the visual characteristics of Human Visual System (HVS), the spherical video was divided into 14 equal-sized regions by two mutually orthogonal ring areas regions. Then, according to the space domain sampling theorem, the 14 regions corresponding to the spherical video content were mapped to 14 rectangular videos with the same size by Lanczos interpolation method. Finally, according to the characteristics of the latest video coding standard, the 14 rectangular videos were rearranged to get a compact panoramic video in keeping with coding standards. The experimental results show that the DRP algorithm achieve a higher compression efficiency compared with the EquiRectangular mapping Projection (ERP) algorithm, OctaHedral mapping Projection (OHP) algorithm and IcoSahedral mapping Projection (ISP) algorithm. Specifically, compared with the most popular ERP algorithm, the proposed method reduces the bit rate by 8.61% which obviously improves the coding efficiency.

Sample Adaptive Offset (SAO) is a time-consuming part of in-loop filter in the second generation of Audio Video coding Standard (AVS2) and High Efficiency Video Coding (HEVC) standard. Aiming at the problem that existing SAO algorithms had large amounts of computation and high complexity, an improved fast rate-distortion algorithm was proposed. In this new method, the original defined table of the offset values and its binary bit string to be written into the code stream were modified by analyzing the relationship between the different offset values of each class in the edge mode and its change of the rate-distortion, so that an early termination condition was set to quickly find the best offset value for the current SAO unit without calculating the rate-distortion cost of each offset. The experimental results show that, compared with the calculation results in AVS2, the proposed algorithm reduces not only the calculation amounts but also the number of cycles by 75% to find the best offset values and the operating time of in-loop filter by 33%, which effectively lowers the complexity of the calculation in ensuring the rate-distortion of image barely changed.

For Audio Video coding Standard Ⅱ(AVS2) intra-prediction mode determination process is complicated to calculate, and the popularity of ultra-high definition video put encoding and decoding system under great pressure, a kind of fast intra prediction algorithm was presented in this paper. The algorithm selected the part of the Smallest Coding Unit (SCU) prediction mode,reducing the amount of computation of the underlying SCU, and then the upper layer Coding Unit (CU) obtained the prediction mode by the lower CU prediction mode, thereby reducing the amount of computation of the upper CU. The experimental results show that the impact on the compression efficiency of the algorithm is very small, the encoding time on average decreases more than 15 percent, and can effectively reduce the complexity of intra-coding.