143 research outputs found
Weakly-Supervised Action Segmentation with Iterative Soft Boundary Assignment
In this work, we address the task of weakly-supervised human action
segmentation in long, untrimmed videos. Recent methods have relied on expensive
learning models, such as Recurrent Neural Networks (RNN) and Hidden Markov
Models (HMM). However, these methods suffer from expensive computational cost,
thus are unable to be deployed in large scale. To overcome the limitations, the
keys to our design are efficiency and scalability. We propose a novel action
modeling framework, which consists of a new temporal convolutional network,
named Temporal Convolutional Feature Pyramid Network (TCFPN), for predicting
frame-wise action labels, and a novel training strategy for weakly-supervised
sequence modeling, named Iterative Soft Boundary Assignment (ISBA), to align
action sequences and update the network in an iterative fashion. The proposed
framework is evaluated on two benchmark datasets, Breakfast and Hollywood
Extended, with four different evaluation metrics. Extensive experimental
results show that our methods achieve competitive or superior performance to
state-of-the-art methods.Comment: CVPR 201
Scale-Adaptive Video Understanding.
The recent rise of large-scale, diverse video data has urged a new era of high-level video understanding. It is increasingly critical for intelligent systems to extract semantics from videos. In this dissertation, we explore the use of supervoxel hierarchies as a type of video representation for high-level video understanding. The supervoxel hierarchies contain rich multiscale decompositions of video content, where various structures can be found at various levels. However, no single level of scale contains all the desired structures we need. It is essential to adaptively choose the scales for subsequent video analysis. Thus, we present a set of tools to manipulate scales in supervoxel hierarchies including both scale generation and scale selection methods.
In our scale generation work, we evaluate a set of seven supervoxel methods in the context of what we consider to be a good supervoxel for video representation. We address a key limitation that has traditionally prevented supervoxel scale generation on long videos. We do so by proposing an approximation framework for streaming hierarchical scale generation that is able to generate multiscale decompositions for arbitrarily-long videos using constant memory.
Subsequently, we present two scale selection methods that are able to adaptively choose the scales according to application needs. The first method flattens the entire supervoxel hierarchy into a single segmentation that overcomes the limitation induced by trivial selection of a single scale. We show that the selection can be driven by various post hoc feature criteria. The second scale selection method combines the supervoxel hierarchy with a conditional random field for the task of labeling actors and actions in videos. We formulate the scale selection problem and the video labeling problem in a joint framework. Experiments on a novel large-scale video dataset demonstrate the effectiveness of the explicit consideration of scale selection in video understanding.
Aside from the computational methods, we present a visual psychophysical study to quantify how well the actor and action semantics in high-level video understanding are retained in supervoxel hierarchies. The ultimate findings suggest that some semantics are well-retained in the supervoxel hierarchies and can be used for further video analysis.PhDComputer Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133202/1/cliangxu_1.pd
Deep Cross-Modal Audio-Visual Generation
Cross-modal audio-visual perception has been a long-lasting topic in
psychology and neurology, and various studies have discovered strong
correlations in human perception of auditory and visual stimuli. Despite works
in computational multimodal modeling, the problem of cross-modal audio-visual
generation has not been systematically studied in the literature. In this
paper, we make the first attempt to solve this cross-modal generation problem
leveraging the power of deep generative adversarial training. Specifically, we
use conditional generative adversarial networks to achieve cross-modal
audio-visual generation of musical performances. We explore different encoding
methods for audio and visual signals, and work on two scenarios:
instrument-oriented generation and pose-oriented generation. Being the first to
explore this new problem, we compose two new datasets with pairs of images and
sounds of musical performances of different instruments. Our experiments using
both classification and human evaluations demonstrate that our model has the
ability to generate one modality, i.e., audio/visual, from the other modality,
i.e., visual/audio, to a good extent. Our experiments on various design choices
along with the datasets will facilitate future research in this new problem
space
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