=Paper= {{Paper |id=Vol-2495/paper12 |storemode=property |title=Adversarial Learning for Visual Tracking Research Idea |pdfUrl=https://ceur-ws.org/Vol-2495/paper12.pdf |volume=Vol-2495 |authors=Emanuel Di Nardo |dblpUrl=https://dblp.org/rec/conf/aiia/Nardo19 }} ==Adversarial Learning for Visual Tracking Research Idea== https://ceur-ws.org/Vol-2495/paper12.pdf
                                  Adversarial Learning for Visual Tracking
                                               Research Idea

                                               Emanuel Di Nardo1[0000−0002−6589−9323]

                                                University of Milan, Milan MI 20122, Italy



                                 Abstract. The doctoral research activity1 mainly focuses on method-
                                 ologies in the field of computer vision. In particular, the work is focused
                                 on designing, developing and validating novel approaches, also based on
                                 deep learning methodologies, for visual tracking. Visual tracking in video
                                 sequences has always been a main topic in computer vision and interest-
                                 ing results have been obtained by approaches based on Support Vector
                                 Machine, Siamese Networks and Discrete Correlation Filters. However,
                                 these techniques are limited due to the low discriminative ability of the
                                 used features for object detection. In his research activities, Emanuel
                                 Di Nardo proposes a novel approach, based on Generative Adversarial
                                 Networks for feature extraction or regression. In particular, using Gen-
                                 erative Adversarial Networks we are able to characterize the elements to
                                 be traced in the scene and make them easier to recognize.

                                 Keywords: Deep Learning · Adversarial Learning · Feature Extraction
                                 · Visual Tracking


                          1    Introduction

                          Visual tracking in video sequences has always been a topic that arouses the
                          attention of the scientific community. It consists in detecting and following an
                          object that moves in a scene. The object will inevitably undergo modifications
                          during its movement (Fig. 1). It happens both because of the displacement itself
                          being free of constraints and because the scene itself, which could present obsta-
                          cles between the camera and the object and still due to problems caused by the
                          acquisition conditions as in the case of non-ideal lighting. Therefore it is needed
                          to use techniques that are defined as robust with a fair compromise of accuracy.
                          There are many challenges for this kind of task and one is VOT (Visual Object
                          Tracking) [7]. Usually, in this context the following three parameters are taken
                          into account:
                           1. Accuracy. Mean Overlap between the target and the ground truth
                           2. Robustness. How many times the target is lost
                           3. Expected Average Overlap (EAO). Mean of accuracy over multiple
                              video sequences with the same visual properties. It combines accuracy and
                              robustness




Copyright c 2019 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
102      E. Di Nardo




Fig. 1. Tracking examples under different conditions [5]. It is possible to observe in
(row 1) normal appearence and in (row 2) appearance changes, rigid target with a
motion blur, scale changes and illumination problems


    In the VOT challenge, it is possible to identify two kinds of tracking called
short-term and long-term. In the former, an object is always visible in the scene
and it is possible to detect it in each frame. In the latter, the target could not be
present in the scene for long time due to a total occlusion because it came out
of the scene. In this case, the tracker can not report any position for the object,
but it can provide a confidence score that the object is not present.


2     Related Work

Most of the works in visual tracking are compared on various challenges such as
VOT [7] and MOT (Multiple Object Tracking) [8]. On the one hand, a strong
evolution of techniques is based on the template matching of the whole object
[9] [10] [11]. On the other hand, other approaches tend to take into account
the movement and to estimate the possible position in which the target is lo-
cated, relying for example on the optical flow [12] [13]. Other methodologies
called part-based tend to scan the areas close to the initial target by estimating
which points have the greatest probability that there is a target or a part of
it [14] [15]. Nowadays, most trackers use approaches based on artificial Neural
Networks (NN) at various stages of the tracking process. Some use them to have
meaningful features that can be representative of the object [16] [17]. In recent
years, moreover, techniques based on Siamese networks have emerged, which see
two parallel networks that work together to estimate the location of the object
in the scene [5] [17] [18]. Other techniques use filters that allow, through a do-
main transformation, to discriminate the probable position in a robust and a
highly-efficient way [19] [20] [23]. Some methodologies mix all these approaches
together to be more and more precise [21] [22]. The approaches based on Deep
Learning [16] [17] [5] [22] use a pre-trained Neural Network on known datasets
for classifying objects in the images. A recent technique is VITAL [24]. It uses
1
    Ph.D. supervisor: Angelo Ciaramella (University of Naples Parthenope); co-
    supervisor: Fabio Narducci (University of Naples Parthenope).
                     Adversarial Learning for Visual Tracking Research Idea    103

a Generative Adversarial Networks to generate a mask that represents the most
relevant features in the image, based on the input target. Another recent ap-
proach uses compressive sensing for trajectory tracking [26] in order to reduce
the image complexity and be able to know where the target is moving on.


3   Research Idea
The main objective of the research activity is the introduction of a novel approach
based on Generative Adversarial Networks (GANs) [1] for visual tracking. In a
first scenario a GAN is used for tracking. Usually, the adversarial networks are
used to generate samples that are as close as possible to the real ones. This is
possible thanks to the property they have to learn the distribution of the data
they want to generate. This type of approach leads to the generation of a latent
space for the representation of the data. Here, the idea is to use this property
for extracting representative samples (i.e., features). Some studies reported this
approach combined with autoencoders [27] [28]. In particular, the generator net-
work encodes the vector representation extracted form the latent space. In a
second scenario GANs could be used directly to perform a regression operation
[29] [30] to define where an object is found, or at least, as a support to the
localization through probable positions. Differently from what has already been
done [24], in the proposed approach GAN should be able to extract a meaningful
representation of the object with a concrete reconstruction of the target local-
ization in the image instead of a simple dropout mask that suggests what are
the areas that are more sensible to the input. Furthermore, we want the ability
of domain adaptation of GANs to be discriminating for this activity without
recurring, as it happens in [24] and [25] to pre-training on the task of tracking.
Another aspect that should not be underestimated is that of scene and the ob-
ject regularizing. In this context, GANs could be used to remove alterations in
images to make tracking easier or even generating objects in positions different
from those known to better estimate how an object can be changed over time.


4   Planning
Phase One A generative network is built to perform and study the segmenta-
tion of the image trying to localize a target object in an image. The investigation
aims to generate an image that is related to the ground truth used in the dis-
criminator network. As the first point, the activity tries to relate an image and a
target that is visible in it. The first experiments are conducted using the model
in Fig. 2 a generative model with two inputs (the image and the target) that
are encoded individually. In the end, they are concatenated on the feature di-
mension to achieve an association between them. Further methodologies are in
development to enforce the relationship between the image and the target. In
this context, it has to face some problems. The first one is the multi-domain
property that the network tries to approximate because it is not trained on a set
of objects that belong to the same category, but on a large variety of them. On
104     E. Di Nardo




           Fig. 2. First generator model studied in the research activity


the other hand, the segmentation purpose should help to normalize this behavior
because the objective function is calibrated to work on a less complex solution.
Another problem is related to the segmentation quality. It is possible that the
result is not accurate with a degeneration to a kind of output that can be more
similar to a heat-map.
Phase Two The segmentation obtained from the first step can help to under-
stand what is the discriminatory effect of the learned latent space. It can be used
trying to work only on the encoding of the input without bringing it to the gen-
erative output in a pure autoencoder fashion. The main challenge is on the usage
of only encoded features because space on which it is mapped could be lost some
important properties if partially described. Another important investigation can
be done on the discriminator side of the GAN. Usually, it is used only in the
generative learning step and not in the operative phase, but it learns to extract
characteristic features of real data. It is an important property that could be
used in a verification step to avoid low-quality output or in a distraction-aware
manner.
Future proposals In addition to GAN based plan, other research paths can
be invested in future investigation. It involves analyzing the techniques based on
dictionary learning, compressive sensing [26] and ODE [3] that appear to be a
valid alternative to the classical operations found in all tracking algorithms.
 The shown planning would achieve a strong representation of a generic object
and, consequently, learning also the localization in the space. It can be used as
tracking-by-detection solution in a short-term challenge. It gives the possibility
to join the VOT challenge to evaluate the research work using the benchmark
tools provided in the competition and validate the effectiveness of the developed
model.

5     Conclusions
Aim of this study is the introduction of innovative methodologies for visual
tracking in the field of computer vision. In particular, it could be noted that
                       Adversarial Learning for Visual Tracking Research Idea         105

new elements that are currently used in different fields with excellent results
could give a strong boost to the current research status.
    These should be validated comparing with proposed state-of-the-art method-
ologies to understand how much they characterize or not. From here, it is possible
to analyze how to use the whole adversarial model as a detector of objects with-
out going through other methods. This study could also lead to using different
characterization techniques from convolutional networks. In particular, in [31]
the proposed approach deviates from the classic CNN and that appears to be a
good alternative to prevent the number of parameters from exploding.


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