Showing papers by "Houqiang Li published in 2005"

Neighborhood preserving projections (NPP): a novel linear dimension reduction method

Abstract: Dimension reduction is a crucial step for pattern recognition and information retrieval tasks to overcome the curse of dimensionality. In this paper a novel unsupervised linear dimension reduction method, Neighborhood Preserving Projections (NPP), is proposed. In contrast to traditional linear dimension reduction method, such as principal component analysis (PCA), the proposed method has good neighborhood-preserving property. The main idea of NPP is to approximate the classical locally linear embedding (i.e. LLE) by introducing a linear transform matrix. The transform matrix is obtained by optimizing a certain objective function. Preliminary experimental results on known manifold data show the effectiveness of the proposed method.

Error resilient video coding using flexible reference frames

Abstract: Conventional video coding techniques make use of the most recently decoded reference frame(s) for motioncompensated inter prediction. However, it has been shown that to allow using reference frames in a flexible way such that not only the latest reference frames are used is beneficial. A typical use of flexible reference frame is feedback based reference picture selection, wherein error-free reference frames available in both the encoder and decoder sides are selected and used for inter prediction reference. This paper first overviews support of reference picture selection in different video coding standards, and then presents three specific feedback based reference picture selection methods using flexible reference frames. In addition, a novel simple reference frame management method that enables using of flexible reference frame is proposed. The reference frame management method enables much simpler video codec implementations compared to the complex reference frame management methods in H.263 Annex U and H.264/AVC. The proposed coding methods and some conventional methods are compared with each other. Simulation results show significantly improved error resiliency performance of the proposed reference picture selection methods compared to conventional methods. The effect on the performance imposed by feedback delay variation is also shown. Thanks to the merits, support of flexible reference frame and the reference frame management has been adopted to the AVS-M video coding standard.

Face recognition using neighborhood preserving projections

Abstract: Subspace learning is one of the main directions for face recognition. In this paper, a novel unsupervised subspace learning method, Neighborhood Preserving Projections (NPP), is proposed. In contrast to traditional linear dimension reduction method, such as principal component analysis (PCA), the proposed method has good neighborhood-preserving property. The central idea is to modify the classical locally linear embedding by introducing a linear transform matrix. The transform matrix is obtained by optimizing a certain objective function. Experimental results on Yale face database and FERET face database show the effectiveness of the proposed method....

Face recognition using neighborhood preserving projections

Abstract: Subspace learning is one of the main directions for face recognition. In this paper, a novel unsupervised subspace learning method, Neighborhood Preserving Projections (NPP), is proposed. In contrast to traditional linear dimension reduction method, such as principal component analysis (PCA), the proposed method has good neighborhood-preserving property. The central idea is to modify the classical locally linear embedding by introducing a linear transform matrix. The transform matrix is obtained by optimizing a certain objective function. Experimental results on Yale face database and FERET face database show the effectiveness of the proposed method....

Automated segmentation and tracking of cells in time-lapse microscopy using watershed and mean shift

Abstract: In this paper, we present a new method combining watershed and mean shift for segmentation and tracking of cancer cell nuclei in time-lapse fluorescence. First, we apply the watershed algorithm to segment the cells in each frame of the video sequence, including clustered cells. Second, mean shift method is employed to track each cell in its cycle progression. The proposed method can automatically segment and track all cells without any manual initialization. Experimental result shows that our method can detect almost all the touching cells and track them successfully, especially in the case of cell mitosis which is a difficult task using traditional methods such as snake and level set.

An improved spatio-temporal video error concealment algorithm using partial differential equation

Abstract: The application of error concealment in video communication is very important when compressed video sequences are transmitted over error-prone networks and erroneously received. In this paper, we propose a novel error concealment scheme, in which the concealment problem is formulated as minimizing, in a weighted manner, the difference between the gradient of the reconstructed data and a prescribed vector field under given boundary condition. Instead of using the motion compensated block as the final recovered pixel values, we use the gradient of the motion compensated block together with the surrounding correctly decoded pixels of the damaged block to reconstruct the lost data. Both temporal and spatial correlations of the video signals are exploited in the proposed scheme. A well designed weighting factor is used to control the regulation level at a desired direction according to the local blockiness degree at the boundaries of the recovered block. The experimental results show that the proposed algorithm is able to achieve higher PSNR as well as better visual quality in comparison with the error concealment feature implemented in the H.264 reference software. The blocking effects are greatly alleviated while the structural information in the interior of the recovered block is well preserved.