251 research outputs found
Temporal Action Segmentation: An Analysis of Modern Techniques
Temporal action segmentation (TAS) in videos aims at densely identifying
video frames in minutes-long videos with multiple action classes. As a
long-range video understanding task, researchers have developed an extended
collection of methods and examined their performance using various benchmarks.
Despite the rapid growth of TAS techniques in recent years, no systematic
survey has been conducted in these sectors. This survey analyzes and summarizes
the most significant contributions and trends. In particular, we first examine
the task definition, common benchmarks, types of supervision, and prevalent
evaluation measures. In addition, we systematically investigate two essential
techniques of this topic, i.e., frame representation and temporal modeling,
which have been studied extensively in the literature. We then conduct a
thorough review of existing TAS works categorized by their levels of
supervision and conclude our survey by identifying and emphasizing several
research gaps. In addition, we have curated a list of TAS resources, which is
available at https://github.com/nus-cvml/awesome-temporal-action-segmentation.Comment: 19 pages, 9 figures, 8 table
High-Dimensional Regression with Gaussian Mixtures and Partially-Latent Response Variables
In this work we address the problem of approximating high-dimensional data
with a low-dimensional representation. We make the following contributions. We
propose an inverse regression method which exchanges the roles of input and
response, such that the low-dimensional variable becomes the regressor, and
which is tractable. We introduce a mixture of locally-linear probabilistic
mapping model that starts with estimating the parameters of inverse regression,
and follows with inferring closed-form solutions for the forward parameters of
the high-dimensional regression problem of interest. Moreover, we introduce a
partially-latent paradigm, such that the vector-valued response variable is
composed of both observed and latent entries, thus being able to deal with data
contaminated by experimental artifacts that cannot be explained with noise
models. The proposed probabilistic formulation could be viewed as a
latent-variable augmentation of regression. We devise expectation-maximization
(EM) procedures based on a data augmentation strategy which facilitates the
maximum-likelihood search over the model parameters. We propose two
augmentation schemes and we describe in detail the associated EM inference
procedures that may well be viewed as generalizations of a number of EM
regression, dimension reduction, and factor analysis algorithms. The proposed
framework is validated with both synthetic and real data. We provide
experimental evidence that our method outperforms several existing regression
techniques
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