1,726 research outputs found
Learned features versus engineered features for semantic video indexing
International audienceIn this paper, we compare "traditional" engineered (hand-crafted) features (or descriptors) and learned features for content-based semantic indexing of video documents. Learned (or semantic) features are obtained by training classifiers for other target concepts on other data. These classifiers are then applied to the current collection. The vector of classification scores is the new feature used for training a classifier for the current target concepts on the current collection. If the classifiers used on the other collection are of the Deep Convolutional Neural Network (DCNN) type, it is possible to use as a new feature not only the score values provided by the last layer but also the intermediate values corresponding to the output of all the hidden layers. We made an extensive comparison of the performance of such features with traditional engineered ones as well as with combinations of them. The comparison was made in the context of the TRECVid semantic indexing task. Our results confirm those obtained for still images: features learned from other training data generally outperform engineered features for concept recognition. Additionally, we found that directly training SVM classifiers using these features does significantly better than partially retraining the DCNN for adapting it to the new data. We also found that, even though the learned features performed better that the engineered ones, the fusion of both of them perform significantly better, indicating that engineered features are still useful, at least in this case
Deep learning in remote sensing: a review
Standing at the paradigm shift towards data-intensive science, machine
learning techniques are becoming increasingly important. In particular, as a
major breakthrough in the field, deep learning has proven as an extremely
powerful tool in many fields. Shall we embrace deep learning as the key to all?
Or, should we resist a 'black-box' solution? There are controversial opinions
in the remote sensing community. In this article, we analyze the challenges of
using deep learning for remote sensing data analysis, review the recent
advances, and provide resources to make deep learning in remote sensing
ridiculously simple to start with. More importantly, we advocate remote sensing
scientists to bring their expertise into deep learning, and use it as an
implicit general model to tackle unprecedented large-scale influential
challenges, such as climate change and urbanization.Comment: Accepted for publication IEEE Geoscience and Remote Sensing Magazin
Learning a Complete Image Indexing Pipeline
To work at scale, a complete image indexing system comprises two components:
An inverted file index to restrict the actual search to only a subset that
should contain most of the items relevant to the query; An approximate distance
computation mechanism to rapidly scan these lists. While supervised deep
learning has recently enabled improvements to the latter, the former continues
to be based on unsupervised clustering in the literature. In this work, we
propose a first system that learns both components within a unifying neural
framework of structured binary encoding
Learning a Complete Image Indexing Pipeline
To work at scale, a complete image indexing system comprises two components:
An inverted file index to restrict the actual search to only a subset that
should contain most of the items relevant to the query; An approximate distance
computation mechanism to rapidly scan these lists. While supervised deep
learning has recently enabled improvements to the latter, the former continues
to be based on unsupervised clustering in the literature. In this work, we
propose a first system that learns both components within a unifying neural
framework of structured binary encoding
Aggregated Deep Local Features for Remote Sensing Image Retrieval
Remote Sensing Image Retrieval remains a challenging topic due to the special
nature of Remote Sensing Imagery. Such images contain various different
semantic objects, which clearly complicates the retrieval task. In this paper,
we present an image retrieval pipeline that uses attentive, local convolutional
features and aggregates them using the Vector of Locally Aggregated Descriptors
(VLAD) to produce a global descriptor. We study various system parameters such
as the multiplicative and additive attention mechanisms and descriptor
dimensionality. We propose a query expansion method that requires no external
inputs. Experiments demonstrate that even without training, the local
convolutional features and global representation outperform other systems.
After system tuning, we can achieve state-of-the-art or competitive results.
Furthermore, we observe that our query expansion method increases overall
system performance by about 3%, using only the top-three retrieved images.
Finally, we show how dimensionality reduction produces compact descriptors with
increased retrieval performance and fast retrieval computation times, e.g. 50%
faster than the current systems.Comment: Published in Remote Sensing. The first two authors have equal
contributio
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Multimodal Indexing of Presentation Videos
This thesis presents four novel methods to help users efficiently and effectively retrieve information from unstructured and unsourced multimedia sources, in particular the increasing amount and variety of presentation videos such as those in e-learning, conference recordings, corporate talks, and student presentations. We demonstrate a system to summarize, index and cross-reference such videos, and measure the quality of the produced indexes as perceived by the end users. We introduce four major semantic indexing cues: text, speaker faces, graphics, and mosaics, going beyond standard tag based searches and simple video playbacks. This work aims at recognizing visual content "in the wild", where the system cannot rely on any additional information besides the video itself. For text, within a scene text detection and recognition framework, we present a novel locally optimal adaptive binarization algorithm, implemented with integral histograms. It determines of an optimal threshold that maximizes the between-classes variance within a subwindow, with computational complexity independent from the size of the window itself. We obtain character recognition rates of 74%, as validated against ground truth of 8 presentation videos spanning over 1 hour and 45 minutes, which almost doubles the baseline performance of an open source OCR engine. For speaker faces, we detect, track, match, and finally select a humanly preferred face icon per speaker, based on three quality measures: resolution, amount of skin, and pose. We register a 87% accordance (51 out of 58 speakers) between the face indexes automatically generated from three unstructured presentation videos of approximately 45 minutes each, and human preferences recorded through Mechanical Turk experiments. For diagrams, we locate graphics inside frames showing a projected slide, cluster them according to an on-line algorithm based on a combination of visual and temporal information, and select and color-correct their representatives to match human preferences recorded through Mechanical Turk experiments. We register 71% accuracy (57 out of 81 unique diagrams properly identified, selected and color-corrected) on three hours of videos containing five different presentations. For mosaics, we combine two existing suturing measures, to extend video images into in-the-world coordinate system. A set of frames to be registered into a mosaic are sampled according to the PTZ camera movement, which is computed through least square estimation starting from the luminance constancy assumption. A local features based stitching algorithm is then applied to estimate the homography among a set of video frames and median blending is used to render pixels in overlapping regions of the mosaic. For two of these indexes, namely faces and diagrams, we present two novel MTurk-derived user data collections to determine viewer preferences, and show that they are matched in selection by our methods. The net result work of this thesis allows users to search, inside a video collection as well as within a single video clip, for a segment of presentation by professor X on topic Y, containing graph Z
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