An Initial Quantization Parameter Decision Method Based on Frame Complexity with Multiple Objectives of GOP for Rate Control of H.264

Abstract

In this paper, we proposed an initial quantization parameter (QP) decision method based on frame complexity with multiple objectives of GOP (Group of Pictures) for H.264 rate control algorithm. Primarily, we choose four video sequences with different characteristics to constitute a sample space and find their optimal initial QPs which can guarantee to generate video sequences with consistent quality by minimizing the variation of QPs in a GOP, while ensuring the minimizing actual encoding bit rate closer to the target bit rate in various bit rates. And then we calculate the spatial characteristic of tested video sequences using the proportion of the number of complex MBs in the first I-frame. The optimal initial QPs are represented in a two-dimensional matrix form arranged in spatial characteristic and target bit rate according to proposed selection method of optimal initial QP. When any video sequence is given under any target bit rate, its spatial characteristic is calculated and mapped to one of four samples through the proposed mapping method. Finally, its optimal initial QP is determined by picking an element of matrix according to the mapped spatial characteristic and given target bit rate. Simulation results show that the proposed method achieves more obvious consistency in objective PSNRs and has secured encoding bit rate than noted algorithms.