Multiple-compression detection is of particular importance in video forensics, as it reveals possible manipulations to the content. However, methods for detecting multiple compressions with same quantisation parameter...
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Multiple-compression detection is of particular importance in video forensics, as it reveals possible manipulations to the content. However, methods for detecting multiple compressions with same quantisation parameters (QPs) are rarely reported. To deal with this issue, a novel method is presented in this study to detect multiple H.264/advanced video coding compressions with the same QPs. First, a new set, named ratio difference set (RDS), is proposed, which is calculated by identifying the quantised DCT coefficients whose values will be changed after re-compression. Then, a discriminative and fixed statistical feature set extracted from RDS of each video is obtained to serve as input for classification. With the aid of support vector machines, the extracted feature set is used to classify the videos that have undergone H. 264 compressions twice or more from those compressed just once. Experimental results show that high classification accuracy and robustness against copy-move attack and frame-deletion attack can be achieved with the authors' proposed method.
This study proposes a new dynamic threshold model to detect keyframes for the coding of a video sequence. The proposed detection threshold is content adaptive which dynamically updates its value at each frame by takin...
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This study proposes a new dynamic threshold model to detect keyframes for the coding of a video sequence. The proposed detection threshold is content adaptive which dynamically updates its value at each frame by taking into consideration both the statistical properties of the video sequence and the resolution as well as the quantisation parameters. The content variation metric used in the proposed detection method utilises the information that is already generated by the encoder during the encoding process and thus it makes the detection process fast. By applying the proposed scheme to rate control, the sizes of group of pictures are now adapted to the video content and it removes the temporal redundancy among different frames better, which transforms to the improvements on coding efficiency. The experimental results have shown that the proposed method achieves peak signal-to-noise ratio (PSNR) improvement.
This study addresses the problem of designing state feedback controllers for Markov jump systems subject to input quantisation mismatch, and general transition rates allowed to be uncertain and unknown. First, a non-l...
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This study addresses the problem of designing state feedback controllers for Markov jump systems subject to input quantisation mismatch, and general transition rates allowed to be uncertain and unknown. First, a non-linear control law is constructed for eliminating the effect of input quantisation in the presence of mismatch between quantisation parameters. Then, a new method based on vertex separator algorithm is proposed for designing the controller. A sufficient condition is derived such that the stochastic stability and also the disturbance attenuation performance of the resulting closed-loop system can be ensured. Moreover, it is proved that the obtained result is theoretically less conservative than previous results. Finally, numerical examples are presented to show the effectiveness and advantages of the proposed method.
The rate-distortion optimisation criterion of depth maps coding is evaluated by virtual view distortion, which motivates research modelling the distortion and corresponding Lagrange multiplier for depth maps coding. C...
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The rate-distortion optimisation criterion of depth maps coding is evaluated by virtual view distortion, which motivates research modelling the distortion and corresponding Lagrange multiplier for depth maps coding. Current studies follow the assumption that the virtual view distortion introduced by texture videos distortion and depth maps distortion can be explored separately. Then the texture-videos-distortion-induced virtual view distortion is considered as a constant value during depth maps coding. A relationship between the optimal Lagrange multiplier of depth maps and texture videos distortion is investigated. Based on this relationship, an efficient Lagrange multiplier selection algorithm is proposed for depth maps coding based on quantisation parameters of texture videos and depth maps. With the proposed Lagrange multiplier, 1.36% bitrate saving with the same virtual view quality can be achieved compared with 3D high efficiency video coding reference software.
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