The Experts below are selected from a list of 22371 Experts worldwide ranked by ideXlab platform

Alan C Bovik - One of the best experts on this subject based on the ideXlab platform.

  • local bandwidth constrained fast inverse Motion Compensation for dct domain video transcoding
    IEEE Transactions on Circuits and Systems for Video Technology, 2002
    Co-Authors: Shizhong Liu, Alan C Bovik
    Abstract:

    Discrete cosine transform (DCT) based digital video coding standards, such as MPEG and H.26x, are becoming more widely adopted for multimedia applications. Since the standards differ in their format and syntax, video transcoding, where a compressed video bit-stream is converted from one format to another, is of interest for purposes such as channel bandwidth adaptation and video composition. DCT-domain video transcoding is generally more efficient than spatial-domain transcoding. However, since the data is organized block by block in the DCT domain, inverse Motion Compensation becomes the bottleneck for DCT-domain methods. We propose a novel local bandwidth constrained fast inverse Motion Compensation algorithm operating in the DCT domain. Relative to Chang's algorithm, we achieve computational improvement of 25%-55% without visual degradation. A by-product of our algorithm is a reduction of blocking artifacts in very low bit-rate compressed video sequences. The proposed algorithm can be combined with other reported fast methods for more computational savings. We also present a look-up-table (LUT) based implementation method by modeling the statistical distribution of the DCT coefficients in natural images and video sequences. By this method, we obtain a further 31%-48% improvement in computation. The memory requirement of the LUT is about 800 kB, which is reasonable. Moreover, the LUT can be shared by multiple DCT-domain video processing applications running on the same computer or video server.

  • local bandwidth constrained fast inverse Motion Compensation for dct domain video transcoding
    International Conference on Acoustics Speech and Signal Processing, 2001
    Co-Authors: Shizhong Liu, Alan C Bovik
    Abstract:

    DCT-based digital video coding standards such as MPEG and H.26x are becoming more widely adopted for multimedia applications. Since the standards differ in their format and syntax, video transcoding, where a pre-coded video bit-stream is converted from one format to another format, is of interest for purposes such as channel bandwidth adaptation and video composition. DCT-domain video transcoding is generally more efficient than spatial domain transcoding. However, since the data is organized block by block in the DCT-domain, inverse Motion Compensation becomes the bottleneck for DCT-domain methods. We propose a novel local bandwidth constrained fast inverse Motion Compensation algorithm operating in the DCT-domain. Relative to Chang's (1995)algorithm, the proposed algorithm achieves computational improvement of 25% to 55% without visual degradation. A by-product of the proposed algorithm is a reduction of blocking artifacts in very low bit-rate compressed video sequences.

Shizhong Liu - One of the best experts on this subject based on the ideXlab platform.

  • local bandwidth constrained fast inverse Motion Compensation for dct domain video transcoding
    IEEE Transactions on Circuits and Systems for Video Technology, 2002
    Co-Authors: Shizhong Liu, Alan C Bovik
    Abstract:

    Discrete cosine transform (DCT) based digital video coding standards, such as MPEG and H.26x, are becoming more widely adopted for multimedia applications. Since the standards differ in their format and syntax, video transcoding, where a compressed video bit-stream is converted from one format to another, is of interest for purposes such as channel bandwidth adaptation and video composition. DCT-domain video transcoding is generally more efficient than spatial-domain transcoding. However, since the data is organized block by block in the DCT domain, inverse Motion Compensation becomes the bottleneck for DCT-domain methods. We propose a novel local bandwidth constrained fast inverse Motion Compensation algorithm operating in the DCT domain. Relative to Chang's algorithm, we achieve computational improvement of 25%-55% without visual degradation. A by-product of our algorithm is a reduction of blocking artifacts in very low bit-rate compressed video sequences. The proposed algorithm can be combined with other reported fast methods for more computational savings. We also present a look-up-table (LUT) based implementation method by modeling the statistical distribution of the DCT coefficients in natural images and video sequences. By this method, we obtain a further 31%-48% improvement in computation. The memory requirement of the LUT is about 800 kB, which is reasonable. Moreover, the LUT can be shared by multiple DCT-domain video processing applications running on the same computer or video server.

  • local bandwidth constrained fast inverse Motion Compensation for dct domain video transcoding
    International Conference on Acoustics Speech and Signal Processing, 2001
    Co-Authors: Shizhong Liu, Alan C Bovik
    Abstract:

    DCT-based digital video coding standards such as MPEG and H.26x are becoming more widely adopted for multimedia applications. Since the standards differ in their format and syntax, video transcoding, where a pre-coded video bit-stream is converted from one format to another format, is of interest for purposes such as channel bandwidth adaptation and video composition. DCT-domain video transcoding is generally more efficient than spatial domain transcoding. However, since the data is organized block by block in the DCT-domain, inverse Motion Compensation becomes the bottleneck for DCT-domain methods. We propose a novel local bandwidth constrained fast inverse Motion Compensation algorithm operating in the DCT-domain. Relative to Chang's (1995)algorithm, the proposed algorithm achieves computational improvement of 25% to 55% without visual degradation. A by-product of the proposed algorithm is a reduction of blocking artifacts in very low bit-rate compressed video sequences.

Gary J Sullivan - One of the best experts on this subject based on the ideXlab platform.

  • overlapped block Motion Compensation an estimation theoretic approach
    IEEE Transactions on Image Processing, 1994
    Co-Authors: M T Orchard, Gary J Sullivan
    Abstract:

    We present an estimation-theoretic analysis of Motion Compensation that, when used with fields of block-based Motion vectors, leads to the development of overlapped block algorithms with improved Compensation accuracy. Overlapped block Motion Compensation (OBMC) is formulated as a probabilistic linear estimator of pixel intensities given the limited block Motion information available to the decoder. Although overlapped techniques have been observed to reduce blocking artifacts in video coding, this analysis establishes for the first time how (and why) OBMC can offer substantial reductions in prediction error as well, even with no change in the encoder's search and no extra side information. Performance can be further enhanced with the use of state variable conditioning in the Compensation process. We describe the design of optimized windows for OBMC. We also demonstrate how, with additional encoder complexity, a Motion estimation algorithm optimized for OBMC offers further significant gains in Compensation accuracy. Overall mean-square prediction improvements in the range of 16 to 40% (0.8 to 2.2 dB) are demonstrated. >

  • rate distortion optimized Motion Compensation for video compression using fixed or variable size blocks
    Global Communications Conference, 1991
    Co-Authors: Gary J Sullivan, R L Baker
    Abstract:

    The authors describe a method for optimizing in a rate-distortion sense the performance of block matching Motion Compensation for video compression using fixed or variable size blocks. They apply recent advances in rate allocation theory and optimal tree structures to the choice of Motion vector and block size for each region of the prediction image. They show that a variable block size algorithm using an optimized tree structure yields a significant improvement in rate-distortion performance over traditional Motion Compensation with a fixed block size. The computational complexity of such a system is not significantly higher than that of a fixed block size system. >

  • Motion Compensation for video compression using control grid interpolation
    International Conference on Acoustics Speech and Signal Processing, 1991
    Co-Authors: Gary J Sullivan, R L Baker
    Abstract:

    A new class of Motion Compensation methods that are based on control grid interpolation (CGI) for use in video compression is described. The predominant Motion Compensation method, block matching, is shown to be a special case of CGI. A new CGI method is presented that produces a smooth Motion vector field, preserving continuity and connectivity in the prediction image. When contrasted with block matching, the new algorithm eliminates blocking artifacts while using the same or less side information for approximately the same mean square error. Search algorithms and coding methods developed previously for block matching can be used with this new technique. >

Terrence Chen - One of the best experts on this subject based on the ideXlab platform.

  • context region discovery for automatic Motion Compensation in fluoroscopy
    Computer Assisted Radiology and Surgery, 2016
    Co-Authors: Yin Xia, Sarfaraz Hussein, Vivek Singh, Matthias John, Terrence Chen
    Abstract:

    Purpose Image-based tracking for Motion Compensation is an important topic in image-guided interventions, as it enables physicians to operate in a less complex space. In this paper, we propose an automatic Motion Compensation scheme to boost image guidence power in transcatheter aortic valve implantation (TAVI).

  • Motion estimation model for cardiac and respiratory Motion Compensation
    International Conference Information Processing, 2012
    Co-Authors: Sebastian Kaeppler, Alexander Brost, Martin Koch, Terrence Chen, Joachim Hornegger, Felix Bourier, Klaus Kurzidim, Norbert Strobel
    Abstract:

    Catheter ablation is widely accepted as the best remaining option for the treatment of atrial fibrillation if drug therapy fails. Ablation procedures can be guided by 3-D overlay images projected onto live fluoroscopic X-ray images. These overlay images are generated from either MR, CT or C-Arm CT volumes. As the alignment of the overlay is often compromised by cardiac and respiratory Motion, Motion Compensation methods are desirable. The most recent and promising approaches use either a catheter in the coronary sinus vein, or a circumferential mapping catheter placed at the ostium of one of the pulmonary veins. As both methods suffer from different problems, we propose a novel method to achieve Motion Compensation for fluoroscopy guided cardiac ablation procedures. Our new method localizes the coronary sinus catheter. Based on this information, we estimate the position of the circumferential mapping catheter. As the mapping catheter is placed at the site of ablation, it provides a good surrogate for respiratory and cardiac Motion. To correlate the Motion of both catheters, our method includes a training phase in which both catheters are tracked together. The training information is then used to estimate the cardiac and respiratory Motion of the left atrium by observing the coronary sinus catheter only. The approach yields an average 2-D estimation error of 1.99 ± 1.20 mm.

  • combined cardiac and respiratory Motion Compensation for atrial fibrillation ablation procedures
    Medical Image Computing and Computer-Assisted Intervention, 2011
    Co-Authors: Alexander Brost, Martin Koch, Andreas Wimmer, Terrence Chen, Rui Liao, Joachim Hornegger, Norbert Strobel
    Abstract:

    Catheter ablation of atrial fibrillation has become an accepted treatment option if a patient no longer responds to or tolerates drug therapy. A main goal is the electrical isolation of the pulmonary veins attached to the left atrium. Catheter ablation may be performed under fluoroscopic image guidance. Due to the rather low soft-tissue contrast of X-ray imaging, the heart is not visible in these images. To overcome this problem, overlay images from pre-operative 3-D volumetric data can be used to add anatomical detail. Unfortunately, this overlay is compromised by respiratory and cardiac Motion. In the past, two methods have been proposed to perform Motion Compensation. The first approach involves tracking of a circumferential mapping catheter placed at an ostium of a pulmonary vein. The second method relies on a Motion estimate obtained by localizing an electrode of the coronary sinus (CS) catheter. We propose a new Motion Compensation scheme which combines these two methods. The effectiveness of the proposed method is verified using 19 real clinical data sets. The Motion in the fluoroscopic images was estimated with an overall average error of 0.55 mm by tracking the circumferential mapping catheter. By applying an algorithm involving both the CS catheter and the circumferential mapping catheter, we were able to detect Motion of the mapping catheter from one pulmonary vein to another with a false positive rate of 5.8 %.

Luc Van Gool - One of the best experts on this subject based on the ideXlab platform.

  • Fast 3D scanning with automatic Motion Compensation
    Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition, 2007
    Co-Authors: Thibaut Weise, Bastian Leibe, Luc Van Gool
    Abstract:

    We present a novel 3D scanning system combining stereo and active illumination based on phase-shift for robust and accurate scene reconstruction. Stereo overcomes the traditional phase discontinuity problem and allows for the reconstruction of complex scenes containing multiple objects. Due to the sequential recording of three patterns, Motion will introduce artifacts in the reconstruction. We develop a closed-form expression for the Motion error in order to apply Motion Compensation on a pixel level. The resulting scanning system can capture accurate depth maps of complex dynamic scenes at 17 fps and can cope with both rigid and deformable objects.