174,412 research outputs found
Learning Task Relatedness in Multi-Task Learning for Images in Context
Multimedia applications often require concurrent solutions to multiple tasks.
These tasks hold clues to each-others solutions, however as these relations can
be complex this remains a rarely utilized property. When task relations are
explicitly defined based on domain knowledge multi-task learning (MTL) offers
such concurrent solutions, while exploiting relatedness between multiple tasks
performed over the same dataset. In most cases however, this relatedness is not
explicitly defined and the domain expert knowledge that defines it is not
available. To address this issue, we introduce Selective Sharing, a method that
learns the inter-task relatedness from secondary latent features while the
model trains. Using this insight, we can automatically group tasks and allow
them to share knowledge in a mutually beneficial way. We support our method
with experiments on 5 datasets in classification, regression, and ranking tasks
and compare to strong baselines and state-of-the-art approaches showing a
consistent improvement in terms of accuracy and parameter counts. In addition,
we perform an activation region analysis showing how Selective Sharing affects
the learned representation.Comment: To appear in ICMR 2019 (Oral + Lightning Talk + Poster
Video Classification With CNNs: Using The Codec As A Spatio-Temporal Activity Sensor
We investigate video classification via a two-stream convolutional neural
network (CNN) design that directly ingests information extracted from
compressed video bitstreams. Our approach begins with the observation that all
modern video codecs divide the input frames into macroblocks (MBs). We
demonstrate that selective access to MB motion vector (MV) information within
compressed video bitstreams can also provide for selective, motion-adaptive, MB
pixel decoding (a.k.a., MB texture decoding). This in turn allows for the
derivation of spatio-temporal video activity regions at extremely high speed in
comparison to conventional full-frame decoding followed by optical flow
estimation. In order to evaluate the accuracy of a video classification
framework based on such activity data, we independently train two CNN
architectures on MB texture and MV correspondences and then fuse their scores
to derive the final classification of each test video. Evaluation on two
standard datasets shows that the proposed approach is competitive to the best
two-stream video classification approaches found in the literature. At the same
time: (i) a CPU-based realization of our MV extraction is over 977 times faster
than GPU-based optical flow methods; (ii) selective decoding is up to 12 times
faster than full-frame decoding; (iii) our proposed spatial and temporal CNNs
perform inference at 5 to 49 times lower cloud computing cost than the fastest
methods from the literature.Comment: Accepted in IEEE Transactions on Circuits and Systems for Video
Technology. Extension of ICIP 2017 conference pape
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