Lecture 15 - Stanford Vision Lab

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Object Bag of ‘words’ Fei-Fei Li Lecture 15 - 6 14‐Nov‐11
Analogy to documents Of all the sensory impressions proceeding to the brain, the visual experiences are the dominant ones. Our perception of the world around us is based essentially on the messages that reach the brain from our eyes. For a long time it was thought that the retinal image was transmitted sensory, point brain, by point to visual centers in the brain; the cerebral cortex was a visual, perception, movie screen, so to speak, upon which the image in retinal, the eye was cerebral projected. Through cortex, the discoveries of eye, Hubel cell, and Wiesel optical we now know that behind the origin of the visual perception in the nerve, brain there image is a considerably more complicated Hubel, course of Wiesel events. By following the visual impulses along their path to the various cell layers of the optical cortex, Hubel and Wiesel have been able to demonstrate that the message about the image falling on the retina undergoes a stepwise analysis in a system of nerve cells stored in columns. In this system each cell has its specific function and is responsible for a specific detail in the pattern of the retinal image. China is forecasting a trade surplus of $90bn (£51bn) to $100bn this year, a threefold increase on 2004's $32bn. The Commerce Ministry said the surplus would be created by a predicted 30% jump in exports to $750bn, compared with a 18% rise in imports to $660bn. The figures China, are likely trade, to further annoy the surplus, US, which has commerce, long argued that China's exports are unfairly helped by a deliberately exports, undervalued imports, yuan. Beijing US, agrees the yuan, surplus bank, is too high, domestic, but says the yuan is only one factor. Bank of China governor Zhou foreign, Xiaochuan increase, said the country also needed to do trade, more to value boost domestic demand so more goods stayed within the country. China increased the value of the yuan against the dollar by 2.1% in July and permitted it to trade within a narrow band, but the US wants the yuan to be allowed to trade freely. However, Beijing has made it clear that it will take its time and tread carefully before allowing the yuan to rise further in value. Fei-Fei Li Lecture 15 - 7 14‐Nov‐11
Page 1 and 2: Lecture 15: Object recognition: Bag
Page 3 and 4: What we will learn today? • Bag o
Page 5: Related works • Early “bag of w
Page 9 and 10: definition of “BoW” - Independe
Page 11 and 12: 1.Feature detection and representat
Page 17 and 18: 2. Codewords dictionary formation
Page 19 and 20: 2. Codewords dictionary formation F
Page 21 and 22: Visual vocabularies: Issues • How
Page 23 and 24: 3. Bag of word representation frequ
Page 25 and 26: Learning and Recognition codewords
Page 27 and 28: Discriminative classifiers category
Page 29 and 30: Nearest Neighbors classifier Query
Page 31 and 32: K- Nearest Neighbors classifier fro
Page 33 and 34: Learning and Recognition 1. Discrim
Page 35 and 36: Support vector machines • Find hy
Page 37 and 38: Nonlinear SVMs •Datasets that are
Page 39 and 40: Nonlinear SVMs • Nonlinear decisi
Page 41 and 42: Pyramid match kernel • Fast appro
Page 43 and 44: What about multi‐class SVMs? •
Page 45 and 46: Object recognition results • ETH
Page 47 and 48: Learning and Recognition 1. Discrim
Page 49 and 50: Some notations • w: a collection
Page 51 and 52: the Naïve Bayes model c w N Graphi
Page 53 and 54: Csurka et al. 2004 Fei-Fei Li Lectu
Page 55 and 56: Generative vs discriminative • Di
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What we will learn today? • Bag o
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Parts and Structure Literature •
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Deformations A B C D Fei-Fei Li Lec
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Background clutter Fei-Fei Li Lectu
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Learning Models `Manually’ • Ob
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So far….. • Representation - Jo
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(Semi) Unsupervised learning •Kno
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Unsupervised detector training - 2
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Learning • Take training images.
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Detector Selection •Try out diffe
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Learned face model Pre-selected Par
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Background images Fei-Fei Li Lectur
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Detections of Cars Fei-Fei Li Lectu
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3D Object recognition - Multiple mi
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So far (2)….. • Representation
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Object categorization Fergus et. al
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•Kadir & Brady saliency region de
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Motorbikes Samples from appearance
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Background images evaluated with mo
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Airplanes Fei-Fei Li Lecture 15 - 9
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Summary of results Dataset Fixed sc
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Why this design? • Generic featur
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Supplementary materials • One‐S
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Fei-Fei Li Lecture 15 - 103 14‐No
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Algorithm Burl, et al. Weber, et al
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How do we do better than what stati
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Bayesian framework P(object | test,
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Bayesian framework P(object | test,
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model () space Model Structure Each
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Variational EM Random initializatio
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Faces Motorbikes Airplanes Spotted
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Experiments: obtaining priors airpl
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Number of training examples Fei-Fei
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Number of training examples Fei-Fei
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Lecture 15 - Stanford Vision Lab

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