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.
In the Remaining Useful Life (RUL) prediction methods of aero-engine, the data at different time steps are not weighted simultaneously, including the original data and the extracted features, which leads to the problem of low accuracy of RUL prediction.Therefore, an RUL prediction method based on optimized hybrid model was proposed. Firstly, three different paths were chosen to extract features. 1) The mean value and trend coefficient of the original data were input into the fully connected network. 2) The original data were input into Bidirectional Long Short-Term Memory (Bi-LSTM) network, and the attention mechanism was used to process the obtained features. 3) The attention mechanism was used to process the original data, and the weighted features were input into Convolutional Neural Network (CNN) and Bi-LSTM network. Then, the idea of fusing multi-path features for prediction was adopted, the above-mentioned extracted features were fused and input into the fully connected network to obtain the RUL prediction result. Finally, the Company-Modular Aero-Propulsion System Simulation (C-MAPSS) datasets were used to verify the effectiveness of the method. Experimental results show that the proposed method performs well on all the four datasets. Taking FD001 dataset as an example, the Root Mean Square Error (RMSE) of the proposed method is reduced by 9.01% compared to that of Bi-LSTM network.
Rate-Distortion (R-D) optimization is a crucial technique in video encoders. However, the widely used independent R-D optimization is far from being global optimal. In order to further improve the compression performance of High Efficiency Video Coding (HEVC), a two-pass encoding algorithm combined with both R-D dependency and R-D characteristic was proposed. Firstly, the current frame was encoded with the original method in HEVC, and the number of bits consumed by the current frame and the R-D model parameters of each Coding Tree Unit (CTU) were obtained. Then, combined with time domain dependent rate distortion optimization, the optimal Lagrange multiplier and quantization parameter for each CTU were determined according to the information including current frame bit budget and R-D model parameters. Finally, the current frame was re-encoded, where each CTU had different optimization goal according to its Lagrange multiplier. Experimental results show that the proposed algorithm achieves significant rate-distortion performance improvement. Specifically, the proposed algorithm saves 3.5% and 3.8% bitrate at the same coding quality, compared with the original HEVC encoder, under the coding configurations of low-delay B and P frames.
Forged and tampered data frames should be identified and filtered out to ensure network security and efficiency. However, the existing schemes usually fail to work when verification devices are attacked or maliciously controlled in the Software Defined Network (SDN). To solve the above problem, a blockchain-based data frame security verification mechanism was proposed. Firstly, a Proof of Frame Forwarding (PoFF) consensus algorithm was designed and used to build a lightweight blockchain system. Then, an efficient data frame security verifying scheme for SDN data frame was proposed on the basis of this blockchain system. Finally, a flexible semi-random verifying scheme was presented to balance the verification efficiency and the resource cost. Simulation results show that compared with the hash chain based verifying scheme, the proposed scheme decreases the missed detection rate significantly when an equal proportion of switches are maliciously controlled. Specifically, when the proportion is 40%, the decrease effect is very obvious, the missed detection rate can still be kept no more than 32% in the basic verification mode, and can be further reduced to 7% with the assistance of the semi-random verifying scheme. Both are much lower than the missed detection rate of 72% in the hash chain based verifying scheme, and the resource overhead and communication cost introduced by the proposed mechanism are within a reasonable range. Additionally, the proposed scheme can still maintain good verification performance and efficiency even when the SDN controller is completely unable to work.
Object-oriented analysis of polarimetric Synthetic Aperture Radar (SAR) has been used commonly, while the polarimetric decomposition is still based on pixel, which is inefficient to extract polarimetric information. A object-based method was proposed for polarimetric decomposition. The coherent matrix of object was constructed by weighted iteration of scattering coefficient of similarity, and the convergence of coherent matrix was analyzed, therefore polarimetric information could be obtained through the coherent matrix of object instead of pixel, which can improve the efficiency of obtaining polarimetric features. To more fully reflect the terrain target, spatial features of object were extracted. After feature selection, polarimetric SAR image classification experiments using Support Vector Machine (SVM) demonstrate the effectiveness of the proposed method.