In this paper, we propose a fast, accurate content-based video copy detection scheme based on bag-of-global visual features, which is characterized by (1) utilizing an efficient DCT-sign-based feature for fast detection; (2) performing multiple assignment in the temporal domain, in addition to the feature and spatial domain to ensure repeatability in segment-level matching; and (3) adopting an inverse document frequency weighting and temporal burstiness-aware scoring to emphasize distinctive visual words. Despite detection 95 times faster than real-time, the proposed system achieves a false negative rate of 0.2% against queries that are altered by non-geometric transformations without any false positives.

We propose a new voting strategy referred to as ratio voting to improve bag-of-visual words-based image retrieval. It limits the number of votes in proportion to the number of features in visual words, while conventional schemes use (estimated) distances or rank information as a filtering criterion. Ratio voting realizes adaptive thresholding that captures the density of feature vectors. In experiments, we adopt two different distance estimation methods in the post-filtering step and show that ratio voting achieves a considerable improvement in spite of its simplicity in both cases. Furthermore, we perform exhaustive experiments in combining ratio voting with multiple assignment approaches and show that choosing a multiple assignment approach also has a remarkable impact on accuracy.

Music and dance are two major forms of entertainment in our daily life. Moreover, the fact that people dance to music suggests the possibility of synchronizing human motion with music. In this paper, we present a novel system to automatically synthesize human motion that is synchronized with streaming music using both rhythm and intensity features. In our system, a motion capture database is re-organized into a novel graph-based representation with metadata (called metadata motion graphs) beforehand, which is specially designed for the streaming application. When receiving a certain amount of music data as a segment, our system will search a best path for the segment on a metadata motion graph. This approach, whose effectiveness is demonstrated in a user study, can compose motions segment by segment, which (1) are synchronized with the music at a beat level in a short enough period, (2) are connected seamlessly with the previous segment, and (3) have the necessary synchronization capacity for the remaining music no matter how long it is.

In this paper, we present a practical and automatic comic-like image layout system for event photos or event movies. We focus on the comic-like layout with cropping. The comic-like layouts allow viewers to track events in time sequential order like comic books, in which event images are cropped and arranged in panels from top left to bottom right on a screen so that the resultant layout has variety of image shapes and gives a pleasant impression. The main drawback of the conventional method is that an important region such as a face or a salient object area is sometimes cropped. In order to avoid excessive cropping of important regions while maintaining the image order, our system achieves adaptive layout to input images by generating all possible templates suitable for comic and deciding appropriate templates based on our proposed layout evaluation. In the demo, we will show that our full automatic system generates comic-like layouts immediately. Furthermore, the system allows a user to select his/her favorite layout from the multiple ones with different looks.

We propose a novel tool called short-term principal component analysis (ST-PCA) to analyze motion capture (MoCap) data, which records realistic movements in a high dimensional time series. Our ST-PCA is successfully applied to beat induction, which is an important perception of human motion especially in dances and is required by many applications such as music synchronization [Kim et al. 2003; Shiratori et al. 2006]. Following [Kim et al. 2003], motion beats are defined as the regular moments when the movement is changed significantly in direction or magnitude. Different from the previous approaches [Kim et al. 2003; Shiratori et al. 2006] that analyze MoCap data in each channel, we estimate the motion beats regarding MoCap data as a whole with the proposed ST-PCA, which performs PCA in a sliding window. Our experiments demonstrate that our method can estimate much more accurate beats in a wide range of motions including complicated dances.

Although many data hiding methods are proposed in the literature, all of them distort the quality of the host content during data embedding. In this paper, we propose a novel data hiding method in the compressed video domain that completely preserves the image quality of the host video while embedding information into it. Information is embedded into a compressed video by simultaneously manipulating Mquant and quantized discrete cosine transform coefficients, which are the significant parts of MPEG and H.26x-based compression standards. To the best of our knowledge, this data hiding method is the first attempt of its kind. When fed into an ordinary video decoder, the modified video completely reconstructs the original video even compared at the bit-to-bit level. Our method is also reversible, where the embedded information could be removed to obtain the original video. A new data representation scheme called reverse zerorun length (RZL) is proposed to exploit the statistics of macroblock for achieving high embedding efficiency while trading off with payload. It is theoretically and experimentally verified that RZL outperforms matrix encoding in terms of payload and embedding efficiency for this particular data hiding method. The problem of video bitstream size increment caused by data embedding is also addressed, and two independent solutions are proposed to suppress this increment. Basic performance of this data hiding method is verified through experiments on various existing MPEG-1 encoded videos. In the best case scenario, an average increase of four bits in the video bitstream size is observed for every message bit embedded.

This paper proposes an efficient data representation scheme to improve the performance of a data hiding method [1] in MPEG compressed domain. Even though [1] completely preserves the quality of the modified video to that of the original (compressed) video and [1] is reversible, [1] suffers from consistent filesize increase caused by data embedding. To suppress filesize increase, reverse zerorun length (RZL) is proposed to efficiently encode the message. RZL utilizes the statistics of the macroblocks with respect to [1], and the distance between two excited macroblocks is considered to encode a message segment. RZL simultaneously achieves high payload and high embedding efficiency, thus RZL is able to suppress the filesize increase caused by data embedding. We theoretically analyzed that RZL outperformsmatrix encoding for both payload and embedding efficiency for this particular data hiding method. Experiments are also carried out to verify the theoretically deduced results, and the observed results agree with the expected outcomes.

This paper proposes a novel visual cryptography method that embeds a natural secret image into two natural carrier images with high quality at low computational complexity. The secret image is decoded visually by superposing the two carrier images. For some applications such as entertainment use, all three images should be high quality natural images and low computational complexity is also required. However, in the conventional methods, picture quality and processing speed have been tradeoff relations. To solve this problem, we propose a method which is based on conventional visual cryptography using error diffusion halftoning and introduce an additional feedback mechanism to embed the high quality natural image. Experimental results show that the proposed method can achieve higher quality natural images of a superposed image and carrier images while computational complexity is maintained low when compared with the conventional methods.

This paper proposes a high speed bit rate reduction technique on the compressed domain for AAC audio. There are many kinds of AAC audio devices such as PCs and mobile terminals. In order to adapt to various requirements on audio quality and storage capacity, a fast audio transcoding method from a higher to a lower bit rate would be beneficial for the efficient use of master AAC contents. Although the scalability function of AAC or baseband transcoding, which converts a bitstream by decoding and re-encoding, can be employed for this purpose, lower coding efficiency or higher computation load is induced. To resolve these problems, this paper derives the relationship among MDCT, quantization and scaling, and achieves a fast and high quality bit rate reduction by introducing (1) an adaptive scalefactor control, (2) MDCT gain control and 3) the reuse of side information. Experimental results show that the proposed method is about 1.4 times faster than baseband transcoding while achieving almost the equivalent quality.

In this paper, we propose an efficient algorithm for conversion of an MP3 stream into AAC. Generally, this kind of conversion, transcoding, requires full decoding and re-encoding. However, the re-encoding based transcoding process may result in degradation of quality and take longer than encoding from a PCM signal. This paper proposes a method to inherit the frame structure and quantization scale from MP3 to AAC. This enables a reduction in the iteration process, which requires the most time in the AAC encoding process, without incurring degradation in quality. Experimental results show that the proposed method can perform bitstream domain transcoding at high speed while maintaining a high level of audio quality

This paper proposes an MP3 watermarking method that is applicable to a mobile terminal with limited computational resources. Considering that the embedded information is copyright information and metadata, which should be extracted before playing back, the watermark detection process should be executed quickly. However, conventional methods cannot detect a digital watermark at high speed. Thus, this paper proposes that scalefactor values in MP3 data be altered so as not to spoil audio quality. Evaluation tests show that the proposed method is capable of embedding 3bits/frame information and detecting at very high speed without degrading audio quality. Finally, this paper describes an application example of our proposal for authentication with a digital signature.