36578035
Mobile robot sonar interpretation algorithm for distinguishing trees from poles
Abstract We describe an algorithm to automatically distinguish trees from round metal poles with a sonar system packaged on a mobile robot. A polynomial interpolation of the square root of the backscattered signal energy versus scan angle is first plotted. Asymmetry and fitting error are then extracted for each sweep across the object, giving a single point in an abstract phase space. Round metal poles are nearer to the origin than are trees, which scatter the sonar more irregularly due to lobulations and/or surface roughness. Results are shown for 20 trees and 10 metal poles scanned on our campus.
14749080
Mobile Robot Sonar Backscatter Algorithm for Automatically Distinguishing Walls, Fences, and Hedges
We present an algorithm to distinguish several types of brick walls, picket fences, and hedges based on the analysis of backscattered sonar echoes. The echo data are acquired by a mobile robot with a single-transducer 50 kHz pulse-echo sonar computer-controlled scanning system packaged as its sensor head. For several locations along a wall, fence, or hedge, a fan of backscatter sonar echoes is acquired, digitized, and stored on a computer as the sonar transducer is swept over a horizontal arc. Off-line, each digitized echo waveform is then rectified, smoothed, and summed to give a measure of the backscatter strength. This backscatter is then plotted versus scan angle, with a series of N-peak deformable templates fit to these data for each scan. The number of peaks in the best-fitting N-peak template indicates the presence and location of retro-reflectors, and allows automatic categorization of the various fences, hedges, and brick walls.
729904
Sprite generation for frame-based video coding
Sprite coding is a very efficient method for the representation and compression of background video object, which has been accepted by MPEG-4 standard. However, how to automatically generate sprite image from raw video sequence is still an open issue, because the motion of foreground video objects not only disturbs the accuracy of motion estimation but also blurs the generated sprite image. This paper presents a novel technique for the generation of background sprite image with improved global motion estimation (GME) and automatic segmentation. Since GME plays an important role in sprite generation, a hybrid scheme jointing the short-term and long-term motion estimation techniques is first developed in this paper. Automatic video segmentation based on available motion information is incorporated into sprite generation, which can mask moving foreground objects and meanwhile protect background sprite from blur. Therefore, the proposed technique is used to construct high quality sprite directly from a raw video sequence. Furthermore, with this technique the existing sprite coding can be extended to the field of frame-based coding.
9908902
Mode mapping method for H.264/AVC spatial downscaling transcoding
Transcoding is a very effective method for universal media adaptation. Spatial resolution downscaling is one of the most popular transcoding applications. Although a number of transcoding methods have been proposed in the past years, they are not very suitable for the most up-to-date H.264/AVC standard due to its many new features. In this paper, a coding mode mapping method is proposed for H.264/AVC spatial downscaling transcoding. Different from the traditional schemes, the proposed method is focused on the mode decision part, which plays a key role in H.264/AVC video encoding. The mapping scheme is exploited based on the statistics and analysis that reveals the inherent relationship between the frames having the same content but with different spatial resolutions.
41136176
Shape from silhouettes based on a centripetal pentahedron model
In this paper we present a novel volumetric shape from silhouette (SfS) algorithm based on a centripetal pentahedron model (pent-model). The pent-model is an object-centered volumetric model composed of a set of pentahedrons cut from the centripetal triangular pyramids, which together partition the 3D space. The SfS algorithm first computes the pyramids by constructing a geodesic sphere. These pyramids are then projected onto the image planes of all cameras. The intersections between the projected pyramids and the silhouettes, which are a set of hexagons, are computed. This process can be performed very efficiently with pre-computed polar silhouette graphs (PSGs) and reduced PSGs. The hexagons are then back-projected into the 3D space, where the intersections are calculated and the pent-model is derived. After that, a mesh surface model can be extracted by marching pentahedrons. Our algorithm has the combined advantages of robustness, speediness and preciseness. Experimental results based on both synthetic images and real photos are presented.
2827170
Nonlocal Edge-Directed Interpolation
In this paper, we proposed a new edge-directed image interpolation algorithm which can preserve the edge features and natural appearance of images efficiently. In the proposed scheme, we first get a close-form solution of the optimal interpolation coefficients under the sense of minimal mean square error by exploiting autoregressive model (AR) and the geometric duality between the low-resolution and high-resolution images .Then the coefficients of the Nonlocal Edge-directed interpolation (NLEDI) are derived with structure similarity in images, which are solutions of weighted least square equations. The new image interpolation approach preserves spatial coherence of the interpolated images better than the existing methods and it outperforms the other methods in terms of objective and subjective image quality.
15856113
Rate control for advance video coding (AVC) standard
Rate control plays a very important role in constant bit rate (CBR) coding. AVC standard is jointly developed by ISO and ITU-T, which contains several inter and intra prediction modes. Rate distortion optimization (RDO) based on prerequisite quantization parameters determines the optimal prediction of each macroblock. This makes the current AVC software difficult to adopt the existing rate control techniques. This paper proposes an efficient rate control algorithm at macroblock level for AVC standard by considering both rate control and optimal prediction selection. Firstly, a quantization parameter estimated from neighboring macroblock is used in selecting an initial prediction and calculating the activity. Secondly, the estimated quantization parameter is refined according to the activity and virtual buffer occupancy. At last, the prediction mode is determined with the refined quantization parameter. Experimental results show that the proposed rate control algorithm can accurately achieve the target bit rate. Furthermore, the coding efficiency is similar to or even better than that of variable bit rate (VBR) coding.