Abstract. Steganography is a technique applied to ensure secure communication. It is challenged by visual observation or statistical analysis to ascertain whether a message is hidden within a cover medium. Several steganographic methods have been proposed for palette-based images. These methods maintain image quality but cannot resist some statistical and visual attacks. To overcome this problem, two parity assignments with performances similar to those of existing parity assignments are proposed. An innovative embedding process that randomly selects one parity assignment while embedding secret bits in each pixel is provided. Finally, a steganographic method using the proposed embedding process and a specified adaptive scheme is presented. Experimental results revealed that the proposed method is undetectable under some statistical and visual attacks even as it maintains image quality.

Embedding efficiency is an important issue in steganography methods. Matrix embedding (1, n, h) steganography was proposed by Crandall to achieve high embedding efficiency for palette images. This paper proposes a steganography method based on multilayer matrix embedding for palette images. First, a parity assignment is provided to increase the image quality. Then, a multilayer matrix embedding (k, 1, n, h) is presented to achieve high embedding efficiency and capacity. Without modifying the color palette, hk secret bits can be embedded into n pixels by changing at most k pixels. Under the same capacity, the embedding efficiency of the proposed method is compared with that of pixel-based steganography methods. The comparison indicates that the proposed method has higher embedding efficiency than pixel-based steganography methods. The experimental results also suggest that the proposed method provides higher image quality than some existing methods under the same embedding efficiency and capacity.

The primary goal of steganographic methods is to develop statically undetectable methods with high steganographic capacity. The embedding efficiency is one kind of measure for undetectability. Block-based steganography methods have been proposed for achieving higher embedding efficiency under limited embedding capacity. However, in these methods, some blocks with larger embedding distortions are skipped, and a location map is usually incorporated into these methods to record the embedding status of each block. This reduces the embedding capacity for secret messages. In this study, we proposed a block-based steganography method without a location map for palette images. In this method, multiple secret bits can be embedded in a block by modifying at most one pixel with minimal embedding distortion; this enables each block to be used for data embedding; thus, our method provides higher embedding capacity. Furthermore, under the same capacity, the estimated and experimental embedding efficiencies of the proposed method are compared with those of Imaizumi et al. and Aryal et al.’s methods; the comparisons indicate that the proposed method has higher embedding efficiency than Imaizumi et al. and Aryal et al.’s methods.

In most secret image sharing schemes, the secrecy level of each pixel is the same. However, in real applications, different pixels may require different secrecy levels. For example, in a patient's medical image, the region with the patient's name must be highly protected. To solve this problem, Wang and Lin proposed a scheme that allows a dealer to divide an image into multiple regions, each of which is associated with a certain level of secrecy. In their scheme, an extra pixel-security-level map (PSLM) is required to record the secrecy level of each pixel, and the shadow size of the PSLM is approximately 20 % of that of the secret image. It is unreasonable to have such a large overhead. To reduce the shadow size of the PSLM, they restricted each region to be a rectangle. Furthermore, any two participants can reconstruct the PSLM, enabling the content of regions with high secrecy levels to be compromised easily. To resolve these disadvantages, this paper proposes a new encoding scheme for PSLMs. The location of each region is protected according to its secrecy level, thus improving the security of the image. Moreover, the shape of each region is unrestricted, and the shadow size of the PSLM is reduced significantly.

In this paper, we present an online handwritten system for music score recognition. Music score is used to record a music song. People often used to compose a music score on the sheet of paper. In our system, we propose the pen based writing method and use multi-strokes to form a music notation. We extract the height, shape and direction from a stroke as the features and recognize it as a symbol. Then the symbol is combined with other symbols to form a music notation. The system is robust for a general use and supports enough music notations for composition. The recognition rate is 98.35%.

Halftone images are commonly printed on books, newspapers, and magazines. How to protect the copyright of these printed halftone images becomes an important issue. Digital watermarking provides a solution for copyright protection. In this paper, we will propose a novel printable watermarking method for dithering halftone images. Based on downsampling and the property of a dispersed dithering screen, the method can resist cropping, tampering, and print-and-scan process attacks. In addition, comparing to Guo et al.'s method, the experimental results show that the proposed method provides higher robustness for the above-mentioned attacks and better visual quality in the high-frequency regions of halftone images.

In the area of secret image sharing (SIS), most papers focused on the schemes for threshold or some special access structures. Regarding general access structures (GAS), few results have been found in the literature. Two SIS schemes for GAS were proposed in 2001 and 2010, both are based on qualified sets. However, one distorts the reconstructed secret image, and some extra information is needed in both schemes. Here, we propose three polynomial based SIS schemes for GAS. Considering either qualified or forbidden sets, these schemes can reconstruct the secret image perfectly without any extra information needed. Some proof and analysis on the shadow sizes of the three schemes are given to lead us to choose the one with the smallest size. In addition, we also give some comparisons with two existing schemes, and security issue is also addressed in conclusion.

A stereo-pair image contains two views of a scene called the left image and right image. This paper proposes a novel watermarking method for stereo-pair images. The proposed method is divided into three parts: watermark creation, watermark embedding, and watermark verification. Because the left and right images of a stereo pair appear to be highly similar, a robust watermark is first created based on a feature map that records the positions of the unmatched blocks between these two images. The created watermark is then embedded into the left image by swapping the AC coefficients. A feature map is first extracted from the watermarked stereo-pair image during the verification process. Subsequently, the embedded watermark is extracted from the watermarked left image and converted into an estimated feature map. Ownership is proved when the feature map and the estimated feature map are similar. Experimental results indicate that the proposed method exhibits greater robustness against malicious attacks and produces less distortion than existing methods do.

In a PowerPoint file, animation effects are used to emphasize objects, timing effects are used to control the presentation time, and slide transition effects are used to highlight particular slides. Thus, using various effects can make the presentation of a PowerPoint file more colorful and attractive. In this paper, we propose a steganographic method to embed message in a PowerPoint file via various effects. In contrast to other steganographic methods, we not only hide message naturally but also keep the content of the cover media intact. Furthermore, the proposed method can resist the format conversion attack. The experiment result demonstrates that the proposed method is undetectable under some visual and statistical attacks.

In this paper, the bag of words (BoW) representation of modulation spectral analysis of spectral as well as cepstral features will be constructed for music genre classification. First, the modulation spectrum of each spectral and cepstral feature will be obtained through modulation spectral analysis of a longer texture window. Then, the BoW model of the modulation spectral features will be constructed and used for music classification. Experiments conducted on the music database employed in the ISMIR2004 Audio Description Contest have shown that the proposed BoW representation of modulation spectral features can achieve promising classification accuracy, particularly when it is combined with the BoW representation of frame features.

Slow motion replays are valuable for sports video analysis. Many methods for slow motion replay detection have been proposed, and they are classified into two categories. One assumes that a replay is sandwiched by a pair of visually similar special digital video effects, but the assumption is not always true in basketball videos. The other analyzes replay features to distinguish replay segments from non-replay segments. The results are not satisfactory since some features (e.g. dominant color of sports field) are not applicable for basketball. Most replay detectors focus on soccer videos. In this paper, we propose a novel idea to detect slow motion replays in basketball videos. The existence of scoreboard is referred to filter large amount of non-replay frames, this improves detection accuracy. After scoreboard frame filtering, every consecutive non-scoreboard frame sequence bounded by scoreboard frames are considered as a non-scoreboard segment. Characteristics of replays and non-replays are observed to create features, which can be used to detect replays and prune non-replays from non-scoreboard segments. Experimental results show that the proposed replay detection method is applicable for both kinds of basketball videos with/without TV commercials. As compared with previous researches for basketball videos, our method presents the superior performance.

Stereo images captured from a pair of CCDs simultaneously are widely used to create the illusion of 3D depth. Each pair of stereo images has many similar block pairs. In this paper, a novel reversible data hiding method is proposed to embed secret data in these similar block pairs. To increase the embedding capacity, each 3-bit secret data is first converted to a pair of integers. Then, similar block pairs are found based on the lower frequency DCT-quantized coefficients. Each converted integer is embedded via the difference of a pair of middle frequency DCT-quantized coefficients from these similar block pairs. It is worth mentioning that the proposed method is reversible, but the existing data hiding methods for stereo images are irreversible. Experimental results show that the proposed method is undetectable under Chi-square analysis, and it provides high embedding capacity while maintaining acceptable quality of stereo images higher than 30 dB. The experimental results also show that the proposed method outperforms Chang et al.'s method and Lin and Shiu's method in embedding capacity and image quality.

Semantic event extraction is helpful for video annotation and retrieval. For sports video, most previous works detect events by video content itself. Some useful external knowledge has been researched recently. In this paper, we proposed an unsupervised approach to extract semantic events from sports webcast text. First, unrelated words in the descriptions of webcast text are filtered out, and then the filtered descriptions are clustered into significant event categories. Finally, the keywords for each event category are extracted. According to our experimental results, the proposed approach actually extracts significant text events, which can be used for further video indexing and summarization. Furthermore, we also provide a hierarchical searching scheme for text event retrieval.

Semantic event and slow motion replay extraction for sports videos have become hot research topics. Most researches analyze every video frame; however, semantic events only appear in frames with scoreboard, whereas replays only appear in frames without scoreboard. Extracting events and replays from unrelated frames causes defects and leads to degradation of performance. In this paper, a novel framework is proposed to tackle challenges of basketball video analysis. In the framework, a scoreboard detector is first provided to divide video frames to two classes, with/without scoreboard. Then, a semantic event extractor is presented to extract semantic events from frames with scoreboard and a slow motion replay extractor is proposed to extract replays from frames without scoreboard. Experimental results show that the proposed framework is practicable for basketball videos. It is expected that the proposed framework can be extended to other sports.

This paper proposed an undetectable steganographic method through Tetris games.The stegoed tetrimino sequence will be different in each game play, regardless of a secret message being changed or not.The proposed extraction process can automatically extract the secret message while the receiver plays Tetris.A simulator is given to demonstrate that the proposed method can work well on Tetris.A theoretic proof and some experimental results are given to show that the proposed method is undetectable. Although various steganographic methods have been proposed that use distinct cover media, using games to hide data remains a recent development. The study presents a steganographic method based on online Tetris games, in which secret messages are embedded using a generated tetrimino sequence. Each time a person plays an online Tetris game, a new tetrimino sequence should be generated. The proposed method meets this requirement, generating a distinct stegoed tetrimino sequence for each game played. In addition, the study presents a scenario and a simulator for the proposed method. Theoretical proof and experimental results are provided to demonstrate that the proposed method is undetectable.

In this paper, a difference expansion based reversible data hiding approach which achieves the low distortion requirement under the same embedding capacity is proposed. An edge-oriented prediction method and a modified overflow/underflow prevention method are proposed to achieve the requirement. For each pixel, the prediction method uses edge information to get a better predicted value in an attempt to reduce the image distortion. Experimental results have demonstrated that the proposed reversible data hiding method yields lower distortion than several well-known expansion-based reversible data hiding methods.

In this paper, a difference expansion based reversible data hiding approach which achieves the low distortion requirement under the same embedding capacity is proposed. An edge-oriented prediction method and a modified overflow/underflow prevention method are proposed to achieve the requirement. For each pixel, the prediction method uses edge information to get a better predicted value in an attempt to reduce the image distortion. Experimental results have demonstrated that the proposed reversible data hiding method yields lower distortion than several well-known expansion-based reversible data hiding methods.