# Research on Quantization Parameter Decision Scheme for High Efficiency Video Coding
## 1 Introduction
Therefore, the pursuit of ultra-high-definition video has become the trend. At present, the resolution of videos that is widely used on the Internet has reached 1080p, and the range of scene viewing angles is also constantly expanding. These have inspired researchers to continuously explore video coding standards. In 2013, the Video Coding Experts Group (VCEG) formulated a new video coding standard, H.265/HEVC. The H.265/HEVC [5] coding standard continues to use the six modules of intra-prediction, inter-prediction, transformation, quantization, entropy coding, and loop filtering and comprehensively measures the current network environment and computer processing capabilities. Depending on the type of video and other factors, the technology in each module is optimized or replaced to meet the needs of different industries or users. Compared to the H.264 encoding standard, this standard reduces the mismatch, improves the reliability of real-time transmission, reduces bandwidth overhead, and doubles the compression ratio. In order to meet the challenges brought by the massive increase in the resolution of the video and to promote the development of the next generation of international video coding standards, the Joint Video Exploration Team (JVET) was established in October 2015. On the evening of 1 July 2020, Versatile Video Coding (VVC) version 1 was formally finalized at the 19 th Joint Video Expert Group meeting. Compared to HEVC, VVC adds more than 30 new coding tools, covering all modules of the hybrid video codec system framework, making it not only more widely applicable to all links of the video industry chain but also able to widely cover all kinds of devices and terminals, such as mobile phones, computers, head-mounted virtual devices, and so on. In addition, according to the iterative requirements of the video coding standard, the data compression performance of VVC is doubled while keeping the decoder complexity not more than twice that of HEVC. Different from traditional two-dimensional videos, 360-degree panoramic videos are presented as a three-dimensional sphere, which makes existing video codec unable to directly encode and decode panoramic videos [6]. In order to solve this problem, JVET developed a panoramic video encoding standard test platform and developed a set of 360 Lib software library [7], which can be independently used for projection of panoramic video encoding, conversion and quality assessment can also be combined with the test platform of the video coding standard H.265/HEVC or H.266/VVC for panoramic video encoding and decoding operations. In order to be suitable for existing codecs, the panoramic video encoding process mainly includes projection and encoding. Panoramic video needs to be collected and spliced to form a spherical video. During encoding, it needs to be converted into a flat video through a projection transformation process before it can be encoded. There are already many projection conversion methods, such as Equi-Rectangular Projection (ERP), Cube Map (CMP) [8], Equi-angular Cubemap (EAC) [9], Octahedron projection (OHP), Icosahedron Projection (ISP), Segmented Sphere Projection (SSP), Rotated Sphere Projection (RSP), etc. Restricted by factors such as acquisition and splicing, most panoramic video content is often converted to ERP projection format. The ERP projection projects the pixels in each frame of the panoramic video to a rectangular area according to a one-to-one mapping relationship. This will cause some distortion in the projected video, which affects the coding efficiency. The CMP projection format is another format supported by video encoders. This format maps each pixel in the panoramic image to the corresponding position of a disc, with the center of the circle being the observation point (viewport). Compared to the ERP projection format, the CMP projection format keeps the image height fixed and will provide a more realistic panoramic effect but will cause obvious distortion at the edges of the image.