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One of the significant application of computer vision is Stabilizing a video that was captured from a jittery or moving platform. One way to stabilize a video is to track a prominent feature in the image and utilize it as an anchor point to cancel out all perturbations relative to it. This technique, however, must be bootstrapped with knowledge of where such a salient feature remains in the first video frame. The paper presents method of video stabilization that works without any such erstwhile knowledge. The method is built on the basis of Random Sampling and Consensus (RANSAC) and adding few additions to the existing methodologies. It instead automatically investigates for the "background plane" in a video sequence, and utilizes its observed distortion to precise for camera motion. All the simulations have been performed using MATLAB tool.
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APPLICATION OF FEATURE POINT MATCHING TO VIDEO STABILIZATION
By
Nikhil Prathapani
Student Member, IEEE
INTRODUCTION
Along with advancement, digital video has introduced new
problems like video noising, video de-stabilization and video
jitter.
In order to overcome these problems, new techniques like video
enhancement and video stabilization have been proposed.
Of the proposed video stabilization techniques, all most all of
them require prior knowledge of prominent frame.
But the proposed technique is based on RANSAC*, SSD and SIFT,
it does not require any erstwhile knowledge of prominent video
frame for stabilization purpose.
*Tordoff, B; Murray, DW. "Guided sampling and consensus for motion estimation."European Conference n Computer Vision, 2002.
Why estimate visual motion? Visual Motion can be annoying
Camera instabilities, jitter Measure it; remove it (stabilize)
Visual Motion indicates dynamics in the scene Moving objects, behavior Track objects and analyze trajectories
Getting six parameters
SIFT algorithm – Find corresponding pairs At time k
It needs three pairs to determine a unique solution
Y X A
SIFT correspondence from frame 200,201 in outdoor sequence STREET
The fundamental matrix F
C C’T=C’-C
Rp p’
TRp'p Two reference frames are related via the extrinsic parameters
The fundamental matrix F The fundamental matrix is the algebraic
representation of epipolar geometry
The fundamental matrix satisfies the condition that for any pair of corresponding points x↔x’ in the two images
0Fx'xT 0lxT
RANSAC (Random Sampling and Consensus )
repeatselect minimal sample (8 matches)compute solution(s) for Fdetermine inliers
until (#inliers,#samples)>95% or too many times
compute F based on all inliers
SSD (sum of squared differences) surface – textured area
SSD surface – edge
SSD – homogeneous area
ALGORITHM
ANALYSIS AND RESULTS
Step 1- Reading frames from a movie file
Step 2- Collecting Salient Points from Each Frame
SIFT
Step 3- Selecting Correspondences Between Points
SSD
Step 4-. Estimating Transform from Noisy Correspondence
RANSACaffine transform will be a 3-by-3 matrix:[a_1 a_3t_r;a_2 a_4t_c;
0 0 1]The parameters ‘a’ define scale, rotation, and sheering effects of the transform, while the parameters ‘t’ are
translation parameters.
Step 5- Transform Approximation and Smoothing
Step 6- Run on the Full Video
Raw input mean and Corrected sequence mean images
PSNR MSE
RAW INPUT MEAN 22.5406 3.62
CORRECTED SEQUENCE MEAN
25.5725 3.59
CONCLUSION
The paper presents a comprehensive and thorough
approach to video stabilizing videos using MATLAB.
This kind of novel approach to video stabilizing [6, 7, 8]
without prior knowledge of prominent features in the frames
has targeted many applications in the fields of motion
estimation, remote sensing, and airborne applications
REFERENCES
[1]P. A. Keller, The cathode-ray tube: technology, history and applications,Palisades Press, 1991, ISBN 0963155903.[2]W. C. O’Mara, Liquid crystal flat panel display: manufacturing science andtechnology, Van Nostrand Reinhold, 1993, ISBN 0442014287.[3]J. Hutchison, “Plasma display panels: the colorful history of an Illinois tech-nology”, ECE alumni news, university of Illinois, vol. 36(1), 2002.[4]C. Poynton, Digital video and HDTV algorithms and interfaces, MorganKaufmann, 2003, ISBN 1558607927.[5] Tordoff, B; Murray, DW. "Guided sampling and consensus for motion estimation."European Conference n Computer Vision, 2002.[6] Lee, KY; Chuang, YY; Chen, BY; Ouhyoung, M. "Video Stabilization using Robust Feature Trajectories." National Taiwan University, 2009.[7] Litvin, A; Konrad, J; Karl, WC. "Probabilistic video stabilization using Kalman filtering and mosaicking." IS&T/SPIE Symposium on Electronic Imaging, Image and Video Communications and Proc., 2003.[8] Matsushita, Y; Ofek, E; Tang, X; Shum, HY. "Full-frame Video Stabilization." Microsoft® Research Asia.CVPR 2005.
Acknowledgements
I am deeply indebted to my parents who have always backed me equally during all times.
THANK YOU
Any Queries?
For research articles, papers and projects in the fields of Image Processing and Nanoelectronics,
you can connect to my research profile:
http://jntuhcej.academia.edu/NikhilPrathapani
SIFT detector proposed considers local image characteristic and retrieves feature points that are invariant to image rotation, scaling, translation, partly illumination changes and projective transform.
The scale-invariant feature extractor detects feature points through a staged filtering approach that identifies stable points in the scale-space.
Scale Invariant Feature Transform
Why Features? A brief yet comprehensive representation of
the image Can be used for:
Image alignment Object recognition 3D reconstruction Motion tracking Indexing and database search More…
Desired Feature Properties• Robustness => Invariance to changes in
illumination, scale, rotation, affine, perspective • Locality => robustness to occlusion and clutter.
• Distinctiveness => easy to match to a large database of objects.
• Quantity => many features can be generated for even small objects
• Efficiency => computationally “cheap”, real-time performance
Algorithm1. Scale-space extrema detection2. Keypoint localization3. Orientation assignment4. Keypoint descriptor