It the rate control algorithms of the new generation video coding standard H.266/VVC (Versatile Video Coding), the rate-distortion optimization technique with independent coding parameters is adopted. However, the Coding Tree Units (CTUs) within the same frame affect others in the spatial domain, and there are global coding parameters. At the same time, in the CTU-level bit allocation formulas, approximated coding parameters for bit allocation are used, resulting in the reduction of rate control accuracy and coding performance. To address these issues, a spatial-domain global optimization algorithm for CTU-level bit allocation called RTE_RC (Rate Control with Recursive Taylor Expansion) was proposed, and the global coding parameters were approximated by using a recursive algorithm. Firstly, a globally optimized bit allocation model in spatial-domain was established. Secondly, a recursive algorithm was used to calculate the global Lagrange multiplier in the CTU-level bit allocation formula. Finally, the bit allocation of coding units was optimized and the coding units were coded. Experimental results show that under the Low-Delay Prediction frame (LDP) configuration, compared with the rate control algorithm VTM_RC (Rate Control algorithm Versatile Test Model), the proposed algorithm has the rate control error decreased from 0.46% to 0.02%, the bit-rate saved by 2.48 percentage points, and the coding time reduced by 3.52%. Therefore, the rate control accuracy and rate distortion performance are significantly improved by the proposed algorithm.
The existing attribute value reduction models are complex to implement, and the key information extracted by the models is often too concise, which affects the representation ability of the decision system. To resolve above problems, a heuristic attribute value reduction model based on certainty factor was proposed. Firstly, several attribute set tools with different properties were constructed, and the relevant theorems and proofs were shown; at the same time, a reduced information function was developed to assign values to the reduced attributes. Secondly, the certainty factor was taken as heuristic information and the strategy of bottom-up hierarchical search was adopted to construct a heuristic attribute value reduction model, and the layout path and operation process of the model were visually displayed in the form of the pseudo-codes of the program. Finally, the application and verification of the model were performed on simulation data from the existing research, the advantages, applicability, and scalability of the model were summarized and discussed. The results show that the new model is feasible and effective, easy to implement by programming; it has low requirements of data characteristics and is suitable for general expert systems;moreover, the value information extracted by the new model is diverse and concise with strong generalization, and does not lose the key information of the decision system.
Aiming at the problem of neglecting some narrow roads due to the formation constraints in the multi-UAV (Unmanned Aerial Vehicle) cooperative trajectory planning, a Fast Particle Swarm Optimization method based on Adaptive Distributed Model Predictive Control (ADMPC-FPSO) was proposed. In the method, the formation strategy combining leader-follower method and virtual structure method was used to construct adaptive virtual formation guidance points to complete the cooperative formation control task. According to the idea of model predictive control, combined with the distributed control method, the cooperative trajectory planning was transformed into a rolling online optimization problem, and the minimum distance and other performance indicators were used as cost functions. By designing the evaluation function criterion, the variable weight fast particle swarm optimization algorithm was used to solve the problem. The simulation results show that the proposed algorithm can effectively realize the multi-UAV cooperative trajectory planning, can quickly complete the adaptive formation transformation according to the environmental changes, and has lower cost than the traditional formation strategy.
Focusing on the problem that the privacy-preserving of identity authentication in Vehicular Ad Hoc NETworks (VANET), a conditional privacy-preserving authentication scheme was proposed. Firstly, this paper introduced the short signature technology, and then constructed a new identity-based short signature scheme. Compared with the well-known Conditional Privacy-Preserving Authentication Scheme (CPAS), the proposed scheme could reduce the computation costs required for both signature and verification processes and improve the communication efficiency. Secondly, the scheme divided the private signature key into two correlative sub-segments, so that it could effectively solve the issue of key escrow. Therefore, the scheme was especially suitable for the environment of VANET. Based on the proposed signature scheme, a conditional privacy-preserving authentication scheme was presented, which can achieve identity authentication with conditional privacy preservation. The theoretical and efficiency analysis shows that the scheme needs only three dot multiplication in the signature process and takes one dot multiplication, two pairing operation in the verification process. Especially, the proposed scheme use batch verification by adding the small coefficient test to accelerate the authentication speed and reduce the error rate.
Accurate background model is the paramount base for object extracting and tracing. In response to swing objects which part quasi-periodically changed in intricate scene, based on multi-Gaussian background model, a new Quasi-Periodic Background Algorithm (QPBA) was proposed to suppress the swing objects and establish an accurate and stable background model. The specific process included: According to multi-Gaussian background model, the object classification in scene was set up, and the effect on Gaussian model's parameters caused by swing objects was analyzed. By using color distribution values as samples to establish Gaussian model to keep swing pixels, the swing model in swing pixels was integrated into background model with weight factors of occurrence frequency and time interval. Comparison among QPBA and the classical background modeling algorithms such as GMM (Gaussian Mixture Model), ViBe (Visual Background extractor) and CodeBook was put forward, and the results were assessed in aspects of quality, quantity and efficiency. It shows that QPBA has a more obvious suppression on swing objects, and its fall-out ratio is less than 1%, so that it can handle the scene with swing objects. At the same time, its correct detection number is consistent with other algorithms, thus the moving objects can be reserved perfectly. In addition, the efficiency of QPBA is high, and its resolving time is approximate to CodeBook, which can satisfy the requirements of real-time computation.