Recently, two new international image and video coding standards have been released: the wavelet-based JPEG2000 standard designed basically for compressing still images, and H.264/AVC, the newest generic standard for video coding. As part of the JPEG2000 suite, Motion-JPEG2000 extends JPEG2000 to a range of applications originally associated with a pure video coding standard like H.264/AVC. However, currently little is known about the relative performance of Motion-JPEG2000 and H.264/AVC in terms of coding efficiency on their overlapping domain of target applications requiring the random access of individual pictures. In this paper, we report on a comparative study of the rate-distortion performance of Motion-JPEG2000 and H.264/AVC using a representative set of video material. Our experimental coding results indicate that H.264/AVC performs
surprisingly well on individually coded pictures in comparison to the highly sophisticated still image compression technology of JPEG2000. In addition to the rate-distortion analysis, we also provide a brief comparison of the evaluated coding algorithms in terms of complexity and functionality.
There is a considerable amount of literature about image denoising using wavelet-based methods. Some new ideas where also reported using fractal methods. In this paper we propose a hybrid wavelet-fractal denoising method. Using a non-subsampled overcomplete wavelet transform we present the image as a collection of translation invariant copies in different frequency subbands. Within this multiple representation we do a fractal coding which tries to approximate a noise free image. The inverse wavelet transform of the fractal collage leads to the denoised image. Our results are comparable to some of the most efficient known denoising methods.
In this paper, we propose a spatially adaptive wavelet thresholding method using a context model that has been inspired by our prior work on image coding. The proposed context model relies on an estimation of the weighted variance in a local window of scale and space. Appropriately chosen weights are used to model the predominant correlations for a reliable statistical estimation. By iterating the context-based thresholding operation, a more accurate reconstruction can be achieved. Experimental results show that our proposed method yields significantly improved visual quality as well as lower mean squared error compared to the best recently published results in the denoising literature.
In this paper, we present a novel design of a wavelet-based video coding algorithm within a conventional hybrid framework of temporal motion-compensated prediction and transform coding. Our proposed algorithm involves the incorporation of multi-frame motion compensation as an effective means of improving the quality of the temporal prediction. In addition, we follow the rate-distortion optimizing strategy of using a Lagrangian cost function to discriminate between different decisions in the video encoding process. Finally, we demonstrate that context-based adaptive arithmetic coding is a key element for fast adaptation and high coding efficiency. The combination of overlapped block motion compensation and frame-based transform coding enables blocking-artifact free and hence subjectively more pleasing video. In comparison with a highly optimized MPEG-4 Advanced Simple Profile coder, our proposed scheme provides significant performance gains in objective quality of 2.0-3.5 dB PSNR.
This paper describes a video coding algorithm that combines new ideas in motion estimation, wavelet filter design, and wavelet-based coding techniques. A motion compensation technique using image warping and overlapped block motion compensation is employed to reduce temporal redundancies in a given image sequence. This combined motion model has the advantage of representing more complex motion than simple block matching schemes. Spatial decorrelation of the motion compensated residual images is performed using an one- parametric family of biorthogonal IIR wavelet filters coupled with a highly efficient pre-coding scheme. Experimental results demonstrate substantial improvements in objective quality of 1.0 - 2.2 dB PSNR compared to the H.263+ standard. Especially at very low bit-rates where the reconstruction quality of block-based coders suffers from visually annoying blocking artifacts the proposed coding scheme produces a superior subjective quality.
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