We describe a scheme that achieves spatially scalable coding of video by employing nonscalable video encoders (e.g., MPEG-2 main profile), along with a downsampler and an upsampler. The scheme is illustrated for the case of coding video at two resolutions. The enhancement layer is coded in two steps by first exploiting the spatial redundancy and then exploiting the temporal redundancy. Hence, the scheme has a separable implementation. Results are presented for five different sequences, coded for three different combinations of base and enhancement layer bit rates. When MPEG-2 main profile is used for the nonscalable encoders, the results obtained are comparable to the performance of MPEG-2 spatial scalability profile.

Given a video frame in terms of its 8/spl times/8 block-DCT coefficients, we wish to obtain a downsized or upsized version of this frame also in terms of 8/spl times/8 block-DCT coefficients. The DCT being a linear unitary transform is distributive over matrix multiplication. This fact has been used for downsampling video frames in the DCT domain. However, this involves matrix multiplication with the DCT of the downsampling matrix. This multiplication can be costly enough to trade off any gains obtained by operating directly in the compressed domain. We propose an algorithm for downsampling and also upsampling in the compressed domain which is computationally much faster, produces visually sharper images, and gives significant improvements in PSNR (typically 4-dB better compared to bilinear interpolation). Specifically the downsampling method requires 1.25 multiplications and 1.25 additions per pixel of original image compared to 4.00 multiplications and 4.75 additions required by the method of Chang et al. (1995). Moreover, the downsampling and upsampling schemes combined together preserve all the low-frequency DCT coefficients of the original image. This implies tremendous savings for coding the difference between the original frame (unsampled image) and its prediction (the upsampled image). This is desirable for many applications based on scalable encoding of video. The method presented can also be used with transforms other than DCT, such as Hadamard or Fourier.

We present a scheme for jointly watermarking and compressing digital video. The amount of watermark added is adapted to the expected degradation of the watermark due to compression. This results in a more robust watermark. This is achieved without any appreciable decrease in the quality of the decoded video compared to the case when the watermark is not adaptive. Results are presented for the flower garden sequence.

Given a video frame or image in terms of its 8/spl times/8 block-DCT coefficients we wish to obtain a downsized (lower resolution) or upsized (higher resolution) version of this frame also in terms of 8/spl times/8 block -DCT coefficients. We propose an algorithm for achieving this directly in the compressed domain which is computationally much faster, produces visually sharper images and gives significant improvements in PSNR (typically 4 dB better compared to other compressed domain methods based on bilinear interpolation). The downsampling and upsampling schemes combined together preserve all the low-frequency DCT coefficients of the original signal. This implies tremendous savings for coding the difference between the original (unsampled image) and its prediction (the upsampled image). This is desirable for many applications based on scalable encoding of video.

Given a video frame or image in terms of its 8×8 block-DCT coefficients, we wish to obtain a downsized or upsized (by factor of two) version of this frame also in terms of 8×8 block-DCT coefficients. We propose an algorithm for achieving this directly in the DCT domain which is computationally much faster, produces visually sharper images and gives significant improvements in PSNR (typically 4 dB better), compared to other compressed domain methods based on bilinear interpolation. The downsampling and upsampling schemes combined together preserve all the low-frequency DCT coefficients of the original image. This implies tremendous savings for coding the difference between the original (unsampled image) and its prediction (the upsampled image). This is desirable for many applications based on scalable encoding of video.

The paper proposes a computationally fast scheme for denoising a video sequence. Temporal processing is done separately from spatial processing and the two are then combined to get the denoised frame. The temporal redundancy is exploited using a scalar state 1D Kalman filter. A novel way is proposed to estimate the variance of the state noise from the noisy frames. The spatial redundancy is exploited using an adaptive edge-preserving Wiener filter. These two estimates are then combined using simple averaging to get the final denoised frame. Simulation results for the foreman, trevor and susie sequences show an improvement of 6 to 8 dB in PSNR over the noisy frames at PSNR of 28 and 24 dB.

A method for multidimensional hierarchical clustering that is invariant to monotonic transformations of the distance metric is presented. The method derives a tree of clusters organized according to the homogeneity of intracluster and interpoint distances. Higher levels correspond to coarser clusters. At any level the method can detect clusters of different densities, shapes and sizes. The number of clusters and the parameters for clustering are determined automatically and adaptively for a given data set which makes it unsupervised and non-parametric. The method is simple, noniterative and requires low computation. Results on various sample data sets are presented.

A new method for digital image watermarking which does not require the original image for watermark detection is presented. Assuming that we are using a transform domain spread spectrum watermarking scheme, it is important to add the watermark in select coefficients with significant image energy in the transform domain in order to ensure non-erasability of the watermark. Previous methods, which did not use the original in the detection process, could not selectively add the watermark to the significant coefficients, since the locations of such selected coefficients can change due to image manipulations. Since watermark verification typically consists of a process of correlation which is extremely sensitive to the relative order in which the watermark coefficients are placed within the image, such changes in the location of the watermarked coefficients was unacceptable. We present a scheme which overcomes this problem of "order sensitivity". Advantages of the proposed method include (i) improved resistance to attacks on the watermark, (ii) implicit visual masking utilizing the time-frequency localization property of the wavelet transform and (iii) a robust definition for the threshold which validates the watermark. We present results comparing our method with previous techniques, which clearly validate our claims.

In the literature many strategies for attacking and subverting a watermark have been presented. Such attacks suggest that the ability to embed non-erasable watermarks does not necessarily imply that the watermarking scheme can be used to establish ownership. The main aim of this paper is to formulate necessary and sufficient requirements for a watermarking scheme to be able to resolve rightful ownership. It is shown that some of the popular schemes proposed in literature for watermarking images do not satisfy these requirements. Finally, we show that a modification of a watermarking scheme in literature (Piva et al., 1997) performs satisfactorily.

We present a novel improvement to existing schemes for abrupt shot change detection. Existing schemes declare a shot change whenever the frame to frame histogram difference (FFD) value is above a particular threshold. In such an approach, a high value for the threshold results in a small number of false alarms and a large number of missed detections while a low value for the threshold decreases the number of missed detections at the expense of increasing the false alarms. We attribute this situation to the fact that the FFD cannot be reliably used as the sole indicator for the presence of a shot change. In the proposed method a two-step shot detection strategy is used which selectively uses a likelihood ratio (computed directly from the frames and not from the histograms) to confirm the presence of a shot change. Such a two-step checking increases the probability of detection without increasing the probability of false alarm. The improvement proposed is simple and computationally cheap. Tests with a wide variety of video sequences prove the efficacy of the proposed approach.