The paper proposes an algorithm to expose spliced photographs. Firstly, a graph-based segmentation, which defines a predictor to measure boundary evidence between two neighbor regions, is used to make greedy decision. Then the algorithm gets prediction error image using non-negative linear least-square prediction. For each pair of segmented neighbor regions, the proposed algorithm gathers their statistic features and calculates features of gray level co-occurrence matrix. K-means clustering is applied to create a dictionary, and the vector quantization histogram is taken as the result vector with fixed length. For a tampered image, its noise satisfies Gaussian distribution with zero mean. The proposed method checks the similarity between noise distribution and a zero-mean Gaussian distribution, and follows with the local flatness and texture measurement. Finally, all features are fed to a support vector machine classifier. The algorithm has low computational cost. Experiments show its effectiveness in exposing forgery.

This paper proposes two efficient rate control algorithms for Motion JPEG2000. Both methods provide accurate visual quality control under buffer constraints. Frames of the same scene usually have the similar rate-distortion (R-D) characters. The proposed methods predict the R-D models of uncoded frames forwardly or bilaterally according to those of coded frames. Experimental results demonstrate that the proposed algorithms offer visual quality improvements over similar competing methods and save a large amount of memory simultaneously.

In this paper, we investigate a combination scheme of subcarrier intensity-modulation (SIM) with spatial modulation (SM) for optical wireless communication. Using computer simulation, the performances of the proposed SIM/SM scheme are investigated and compared with those of the conventional SIM scheme in the additive white gaussian noise (AWGN) as well as in outdoor environment with turbulence induced fading characteristics. Numerical results show that the proposed SIM/SM scheme can outperform the conventional SIM in an environment with different spectral efficiencies. When the spectral efficiency is varied from 2bits/s/Hz to 4bits/s/Hz, an Eb/N0 gain of 2dB to 5dB is achieved, when the bit error rate of 10-5 is maintained. It shows that the employment of SM may further improve the power efficiency of SIM, when the number of subcarriers increases according to the spectral efficiency. When the spectral efficiency is 4bits/s/Hz, the SIM/SM scheme for 0.5 of log-irradiance variance in the log-normal turbulence channel shows the same performance as SIM with variance of 0.3. This means that the SIM/SM can be an alternative choice in even worse environments.

Rateless erasure code is an error correction code that is able to encode a message of k uncoded symbols into an infinite number of coded symbols. One may reconstruct the original message from any k(1+ε) coded symbols, where ε denotes the decoding inefficiency. This paper proposes a hybrid code that combines the stepping code and random code and name it as Stepping-Random (SR) code. The Part I (first k) coded symbols of SR code are generated with stepping code. The rest of the coded symbols are generated with random code and denoted as Part II coded symbols. The numerical results show that the new hybrid code is able to achieve a complete decoding with no extra coded symbol (ε=0) if all the Part I coded symbols are received without loss. However, if only a portion of Part I coded symbols are received, a high probability of complete decoding is still achievable with k+10 coded symbols from the combination of Part I and II. SR code has a decoding complexity of O(k) in the former and O((βk)3) in the latter, where β ∈ R for 0 ≤ β ≤ 1, is the fraction of uncoded symbols that fails to be reconstructed from Part I coded symbols.