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Effective Deep Multi-source Multi-task Learning Frameworks for Smile Detection, Emotion Recognition and Gender Classification

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https://doi.org/10.31449/inf.v42i3.2301 Informatica 42 (2018) 345–356 345
Effective Deep Multi-source Multi-task Learning Frameworks for Smile
Detection, Emotion Recognition and Gender Classification
Dinh Viet Sang and Le Tran Bao Cuong
Hanoi University of Science and Technology, 1 Dai Co Viet, Hai Ba Trung, Hanoi, Vietnam
E-mail: sangdv@soict.hust.edu.vn, ltbclqd2805@gmail.com
Keywords: multi-task learning, convolutional neural network, smile detection, emotion recognition, gender classification
Received: March 29, 2018
Automatic human facial recognition has been an active reasearch topic with various potential applications.
In this paper, we propose effective multi-task deep learning frameworks which can jointly learn represen-
tations for three tasks: smile detection, emotion recognition and gender classification. In addition, our
frameworks can be learned from multiple sources of data with different kinds of task-specific class labels.
The extensive experiments show that our frameworks achieve superior accuracy over recent state-of-the-art
methods in all of three tasks on popular benchmarks. We also show that the joint learning helps the tasks
with less data considerably benefit from other tasks with richer data.
Povzetek: Razvita je izvirna metoda globokih nevronskih mrež za tri hkratne naloge: prepoznavanje smeha,
ˇ
custev in spola.
1 Introduction
In recent years, we have witnessed a rapid boom of artifi-
cial intelligence (AI) in various fields such as computer vi-
sion, speech recognition and natural language processing.
A wide range of AI products have boosted labor productiv-
ity, improved the quality of human life, and saved human
and social resources. Many artificial intelligence applica-
tions have reached or even surpassed human levels in some
cases.
Automatic human facial recognition has become an ac-
tive research area that plays a key role in analyzing emo-
tions and human behaviors. In this work, we study different
human facial recognition tasks including smile detection,
emotion recognition and gender recognition. All of three
tasks use facial images as input. In smile detection task,
we have to detect if the people appearing in a given image
are smiling or not. We then classify their emotions into
seven classes: angry, disgust, fear, happy, sad, surprise and
neutral in emotion recognition task. Finally, we determine
who are males and who are females in gender classification
task.
In general, these tasks are often solved as separate prob-
lems. This may lead to many difficulties in learning mod-
els, especially, when the training data is not large enough.
On the other hand, the data of different facial analysis tasks
often shares many common characteristics of human faces.
Therefore, joint learning from multiple sources of face data
can boost the performance of each individual task.
In this paper, we introduce effective deep convolutional
neural networks (CNNs) to simultaneously learn common
features for smile detection, emotion recognition and gen-
der classification. Each task takes input data from its corre-
sponding source, but all the tasks share a big part of the
networks with many hidden layers. At the end of each
network, these tasks are separated into three branches with
different task-specific losses. We combine all the losses to
form a common network objective function, which allows
us to train the networks end-to-end via the back propaga-
tion algorithm.
The main contributions of this paper are as follows:
1. We propose effective architectures of CNNs that can
learn joint representations from different sources of
data to simultaneously perform smile detection, emo-
tion recognition and gender classification.
2. We conduct extensive experiments and achieve new
state-of-the-art accuracies in different tasks on popu-
lar benchmarks.
The rest of the paper is organized as follows. In sec-
tion 2, we briefly review related work. In section 3, we
present our proposed multi-task deep learning frameworks
and describe how to train the networks from multiple data
sources. Finally, in section 4, we show the experimental re-
sults on popular datasets and compare our proposed frame-
works with recent state-of-the-art methods.
2 Related work
2.1 Deep convolutional neural networks
In recent years, deep learning has been proven to be ef-
fective in many fields, and particularly, in computer vision.
Deep CNNs are one of the most popular models in the fam-
ily of deep neural networks. LeNet [21], and AlexNet [20]
346 Informatica 42 (2018) 345–356 D. Sang et al.
are known to be the earliest CNN architectures with not
many hidden layers.
Latest CNNs such as VGG [33], Inception [35], ResNet
[13] and DenseNet [16] tend to be deeper and deeper. In
ResNet, residual blocks can be stacked on top of each other
with over 1000 layers. Meanwhile, some other CNN ar-
chitectures like WideResNet [41] or ResNeXt [40] tend
to be wider. All these effective CNNs have demonstrated
their impressive performances in one of the biggest and the
most prestigious competitions in computer vision - the an-
nual ImageNet Large Scale Visual Recognition Challenge
(ILSVRC).
2.2 Smile detection
Traditional methods often detect smile based on a strong
binary classifier with low-level face descriptors. Shan et
al. [32] propose a simple method that uses the intensity
differences between pixels in the gray-scale facial images
and then combines them with AdaBoost classifier [39] for
smile detection. In order to represent faces, Liu et al. [23]
use histograms of oriented gradients (HOG) [10], mean-
while, An et al. [4] use local binary pattern (LBP) [3], lo-
cal phase quantization (LPQ) [25] and HOG. Both of them
[23, 4] then apply SVM classifier [9] to detect smiles. Jain
et al. [18] propose to use Multi-scale Gaussian Derivatives
(MGD) and SVM classifier as well for smile detection.
Some recent methods focus on applying deep neural net-
works to smile detection. Chen at al. [6] use deep CNNs to
extract high-level features from facial images and then use
SVM or AdaBoost classifiers to detect smiles as a classifi-
cation task. Zhang et al. [42] introduce two efficient CNN
models called CNN-Basic and CNN 2-Loss. The CNN-
2Loss is a improved variant of the CNN-Basic, that tries to
learn features by using two supervisory signals. The first
one is recognition signal that is responsible for the clas-
sification task. The second one is expression verification
signal, which is effective to reduce the variation of features
which are extracted from the images of the same expres-
sion class. [30] proposes an effective VGG-like network,
called BKNet, to detect smiles. BKNet achieves better re-
sults than many other state-of-the-art methods in smile de-
tection.
2.3 Emotion recognition
Classical approaches to facial expression recognition are
often based on Facial Action Coding System (FACS) [11].
FACS includes a list of Action Units (AUs) that describe
various facial muscle movements causing changes in facial
appearance. Cootes et al. [38] propose a model based on
an approach called the Active Appearance Model [8] that
creates over 500 facial landmarks. Next, the authors apply
PCA algorithm to the set of landmarks and derive Action
Units (AUs). Finally, a single layered neural network is
used to classify facial expressions.
In Kaggle facial expression recognition competition [1],
the winning team [36] proposes an effective CNN, which
uses the multi-class SVM loss instead of the usual cross-
entropy loss. In [31], Sang et al. propose the so-called
BKNet architecture for emotion recognition and achieve
better performance compared to previous methods.
2.4 Gender classification
Conventional methods for gender classification often take
image intensities as input features. [26] combines the 3D
structure of the head with image intensities. [15] uses im-
age intensities combined with SVM classifier. [5] tries to
use AdaBoost instead of SVM classifier. [12] introduces
a neural network trained on a small set of facial images.
[37] uses the Webers Local texture Descriptor [7] for gen-
der classification. More recently, Levi et al. [22] present
an effective CNN architecture that yields fairly good per-
formance in gender classification.
2.5 Multi-task learning
Multi-task learning aims to solve multiple classification
tasks at the same time by learning them jointly, while ex-
ploiting the commonalities and differences across the tasks.
Recently, Kaiser et al. [19] propose a big model to learn
simultaneously many tasks in nature language processing
and computer vision and achieve promising results. Rothe
et al. [28] propose a multi-task learning model to jointly
learn age and gender classification from images. Zhang et
al. [2] propose a cascaded architecture with three stages of
carefully designed deep convolutional networks to jointly
detect faces and predict landmark locations. Ranjan et al.
[27] introduce a multi-task learning framework called hy-
perface for face detection, landmark localization, pose es-
timation, and gender recognition. Nevertheless, the hyper-
face is only trained from a unique source of data with full
annotations for all tasks.
3 Our proposed frameworks
3.1 Overall architecture
In this work, we propose effective deep CNNs that can
learn joint representations from multiple data sources to
solve different tasks at the same time. The merged dataset
(Fig. 1) is fed into a block called “CNN Shared Network",
which can be designed by using an arbitrary CNN architec-
ture such as VGG [33], ResNet [13] and so on. The moti-
vation of the CNN Shared Network is to help the networks
learn the shared features from multiple datasets across dif-
ferent tasks. It is thought that the features learned in the
shared block can generalize better and make more accurate
predictions than a single-task model. Moreover, thanks to
joint representation learning, the tasks with less data can
largely benefit from other tasks with more data.
After the shared block, each network is separated into
three branches associated with three different tasks. Each
Effective Deep Multi-Source Multi-task Learning Frameworks Informatica 42 (2018) 345–356 347
branch learns task-specific features and has its own loss
function corresponding to each task.
3.2 Multi-task BKNet
Our first multi-task deep learning framework called Multi-
task BKNet has been previously described in [29] (Fig. 3),
which is based on the BKNet architecture [30, 31]. We
construct the CNN shared network by eliminating three last
fully-connected layers of BKNet (Fig. 2).
CNN Shared Network. In this part, we use four con-
volutional (conv) blocks. The first conv block includes two
conv layers with 32 neurons 3×3with the stride 1, followed
by a max pooling layer 2×2with the stride 2. The second
conv block includes two conv layers with 64 neurons 3×3
with the stride 1, followed by a max pooling layer 2×2
with the stride 2. The third conv block includes two conv
layers with 128 neurons 3×3with the stride 1, followed
by a max pooling layer 2×2with the stride 2. Finally, the
last conv block includes three conv layers with 256 neu-
rons 3×3with the stride 1, followed by a max pooling
layer 2×2with the stride 2. Each conv layer is followed
by a Batch normalization layer [17] and a ReLU (Recti-
fied Linear Unit) activation function [24]. The Batch nor-
malization layer reduces the internal covariant shift, and,
hence, allows us to use higher learning rate when applying
the SGD algorithm to accelerate the training process.
Branch Network. After the CNN shared network, we
split the network into three branches corresponding to sep-
arate tasks, i.e., smile detection, emotion recognition and
gender classification. While the CNN shared network can
learn joint representations across three tasks from multiple
datasets, each branch tries to learn individual features cor-
responding to each specific task.
Each branch consists of two fully connected layers with
256 neurons and a final fully connected layer with Cneu-
rons, where Cis the number of classes in each task (C= 2
for smile detection and gender classification branch, and
C= 7 for emotion recognition branch). Note that, after the
last fully connected layer, we can either use an additional
softmax layer as a classifier or not, depending on what kind
of loss function is being used. These kinds of loss function
are described in detail in the next section. Similar with
the CNN shared network, each fully connected layer in all
branches (except the last one) is followed by a Batch Nor-
malization layer and ReLU. Dropout [34] is also utilized in
all fully connected layers to reduce overfitting.
3.3 Multi-task ResNet
ResNet [13] is known as one of the most efficient CNN
architectures so far. In order to enhance the information
flow between layers, ResNet uses shortcut connections be-
tween layers. The original variant of ResNet is proposed
by He et al. in [13] with different numbers of hidden lay-
ers: ResNet-18, ResNet-34 or ResNet-50, ResNet-101 and
ResNet-152. He et al. then introduce an improved variant
of ResNet (called ResNet_v2) in [14] which shows that the
pre-activation order “conv - batch normalization - ReLU"
is consistently better then post-activation order “batch nor-
malization - ReLU - conv".
Inspire by the design concept of ResNet_v2, we propose
a multi-task ResNet framework to jointly learn three tasks:
smile detection, emotion recognition and gender classifi-
cation. Since the amount of facial data is not large, we
choose ResNet-50 (with bottleneck layer) as the base ar-
chitecture to design our multi-task ResNet framework. In
the original ResNet_v2-50 architecture, there are 4 resid-
ual blocks, each of which consists of some sub-sampling
blocks and identity blocks. The architectures of identity
blocks and sub-sampling blocks are shown in Fig. 4a and
Fig. 4b. For both these two kinds of blocks, we use the
bottleneck architecture with base depth mthat consists of
three conv layers: a 1×1conv layer with mfilters followed
by a 3×3conv layer with mfilters and a 1×1conv lay-
ers with 4mfilters. The identity blocks and sub-sampling
blocks are distinguished by the stride value in the second
conv layer and the shortcut connection. In sub-sampling
blocks, we use a conv layer with stride 2 instead of stride
1 as in identity blocks. The first residual block of ResNet-
50 contains only 3 identity blocks and has no sub-sampling
block. The next three residual blocks of ResNet-50 have
a sub-sampling block at the top, followed by 3, 5 and 2
identity blocks, respectively.
Based on the aforementioned ResNet_v2-50 architec-
ture, we propose two versions of multi-task ResNet frame-
work. In the first version, which is abbreviated as Multi-
task ResNet ver1, we use all of 4 residual blocks to build
the CNN shared network to learn joint representations for
three tasks. Like in multi-task BKNet, for each task in
branch network, we use two fully connected layers with
256 neurons combined with a softmax classifier. Fig. 5a
illustrates the architecture of Multi-task ResNet ver1.
In the second version, which is abbreviated as Multi-
task ResNet ver2, we only use first three residual blocks
to build the CNN shared network. For each task in the
branch network, we use a separate residual block combined
with global average pooling layer and a softmax classifier.
Fig. 5b illustrates the architecture of Multi-task ResNet
ver2.
3.4 Multi-source multi-task training
In this paper, we propose effective deep networks that can
learn to perform multi tasks from different data sources.
All data sources are mixed together and form a large com-
mon training set (Fig. 1). Generally, each sample in the
mixing training set is only related to some of the tasks.
Suppose that:
Tis the number of tasks (T= 3 in this paper);
Ltis the individual loss corresponding to the tth task,
t= 1,2, ..., T .
348 Informatica 42 (2018) 345–356 D. Sang et al.
Original dataset Cropped dataset Merged dataset
Smile dataset
Emotion datasetEmotion dataset Emotion dataset
Face detection
Merge and
randomly
shue
Gender dataset
Gender dataset
Smile dataset
Figure 1: Merged dataset
Figure 2: The CNN shared network in Multi-task BKNet is
just the top part (marked by red lines) of the BKNet archi-
tecture [30], excluding the last three fully-connected layers.
Nis the number of samples from all training datasets;
Ctis the number of classes corresponding to the tth
task (C1=C3= 2 for smile detection and gender
classification task, C2= 7 for emotion recognition
task);
– st
iis the vector of class scores corresponding to i-th
sample in tth task;
lt
iis the correct class label of i-th sample in tth task;
– yt
iis the one-hot encoding of the correct class label of
i-th sample in tth task (yt
i(lt
i)=1);
Figure 3: Our proposed Multi-task BKNet
b
yt
iis the probability distribution over the classes of i-th
sample in tth task, which can be obtained by applying
the softmax function to st
i.
αt
i∈ {0,1}is the sample type indicator (αt
i= 1 if
the ith sample is related to the tth task, and αt
i= 0
otherwise).
Note that, if the ith sample is not related to tth task, then
the true label does not exist, and we can ignore lt
iand yt
i.
To ensure the mathematical correctness in this case, we can
set them to arbitrary values, for instance, lt
i= 0 and yt
iis a
Effective Deep Multi-Source Multi-task Learning Frameworks Informatica 42 (2018) 345–356 349
(a) Identity block (b) Subsampling block
Figure 4: The architectures of identity blocks and sub-sampling blocks in our Multi-task ResNet framework.
zero vector.
In this paper, we try two kinds of loss: soft-max cross
entropy or multi-class SVM loss.
The cross-entropy loss requires to use a softmax layer
after the last fully-connected layer of each branch. The
cross-entropy loss Ltcorresponding to tth task is defined
as follows:
Lt=1
N
N
X
i=1
αt
i
Ct
X
j=1
yt
i(j)log(b
yt
i(j))
,(1)
where yt
i(j)∈ {0,1}indicates whether jis the correct
label of i-th sample; b
yt
i(j)[0,1] expresses the probability
that jis the correct label of i-th sample.
The multi-class SVM loss function is used when the last
fully connected layer in each task-specific branch accom-
panies with no activation function. The multi-class SVM
loss function corresponding to the tth task can be defined
as follows:
Lt=1
N
N
X
i=1
αt
i
Ct
X
j=1
j6=lt
i
max(0,st
i(j)st
i(lt
i) + 1)2
,
(2)
where st
i(j)indicates the score of class jin the i-th sample;
st
i(lt
i)defines the score of true label lt
iin the i-th sample.
The total loss of the network is computed as the weighted
sum of the three individual losses. In addition, we also add
L2 weight decay term associated with all network weights
Wto the total network loss to reduce overfitting. The over-
all loss can be defined as follows:
Ltotal =
T
X
1
µtLt+λkWk2
2,(3)
where µtis the importance level of the tth task in the over-
all loss; λis the weight decay coefficient.
We train the network end-to-end via the standard back
propagation algorithm.
3.5 Data pre-processing
All the images from the datasets that we use later are por-
traits. Nevertheless, our networks works with facial regions
only. Thus, we have to perform data pre-processing to crop
faces from the original images in the datasets. Here we
use Multi-task Cascaded Convolutional Neural Networks
(MTCNN) [2] to detect faces in each image. Fig. 6 shows
some examples of using MTCNN for cropping faces.
350 Informatica 42 (2018) 345–356 D. Sang et al.
(a) First version with fully connected layers in the branch net-
work
(b) Second version with residual blocks in the branch network
Figure 5: Our proposed Multi-task ResNet framework. The notation “Identity block, m"means the identity block with
base depth m.
After that, the cropped images are converted to grayscale
and resized to 48 ×48 ones.
Figure 6: MTCNN for face detection. The top row is
original images. The bottom row are cropped faces using
MTCNN.
3.6 Data augmentation
Due to small amount of samples in the dataset, we use data
augmentation techniques to generate more new data for the
training phase. These techniques help us to reduce overfit-
ting and, hence, to learn more robust networks.
We used three following popular ways for data augmen-
tation:
- Randomly crop: We add margins to each image in the
datasets and then crop a random area of that image with the
same size as the original image;
- Randomly flip an image from left to right;
- Randomly rotate an image by a random angle from
15to 15. The space around the rotated image is then
filled with black color.
In practice, we find that applying augmentation tech-
niques greatly improves the performance of the model.
4 Experiments and evaluation
4.1 Datasets
4.1.1 GENKI-4K dataset
GENKI-4K is a well-known dataset used in smile detection
task. This dataset includes 4000 labelled images of human
face from different ages, and races. Among these pictures,
2162 images were labeled as smile and 1838 images were
Effective Deep Multi-Source Multi-task Learning Frameworks Informatica 42 (2018) 345–356 351
labeled as non-smile. The images in this dataset are taken
from the internet with different real-world contexts (unlike
other face datasets, often taken in the same scene), which
makes the detection more challenging. However, some im-
ages in the dataset are unclear (not sure whether smile or
not). In some previous works, some unclear images are
eliminated during the training and testing phases. It is obvi-
ously that keeping wrong samples in the dataset intuitively
makes the model more likely to be confused during the
training phase. In the testing phase, the wrong samples
might considerably reduce the overall accuracy, when the
model makes true predictions but the data says no. Despite
that fact, in this work we still retain all the images in the
original dataset in both phases. Fig. 7 shows some exam-
ples from GENKI-4K dataset.
Figure 7: Some samples in the GENKI-4K dataset. The top
two rows are examples of smile faces and the bottom two
rows are examples of non-smile faces.
4.1.2 FERC-2013 dataset
FERC-2013 dataset is provided on the Kaggle facial ex-
pression competition. The dataset consists of 35,887 gray
images of 48x48 resolution. Kaggle has divided into
28,709 training images, 3589 public test images and 3589
private test images. Each image contains a human face that
is not posed (in the wild). Each image is labeled by one of
seven emotions: angry, disgust, fear, happy, sad, surprise
and neutral. Some images of the FERC-2013 dataset are
showed in Fig. 8.
4.1.3 IMDB and Wiki dataset
In this work, we use IMDB and Wiki datasets as data
sources for gender classification task.
The IMDB dataset is a large face dataset that includes
data from celebrities. The authors take the list of the
most popular 100,000 actors as listed on the IMDB web-
site and (automatically) crawl from their profiles date of
Figure 8: Some samples in the FERC-2013 dataset.
birth, name, gender and all images related to that per-
son. The IMDB dataset contains about 470.000 images. In
this paper, we only use 170.000 images from IMBD. The
Wiki dataset also includes data from celebrities, which are
crawled data from Wikipedia. The Wiki dataset contains
about 62.000 images and in this work we will use about
34.000 images from this dataset. Fig. 9 shows some sam-
ples from IMDB and Wiki datasets.
Figure 9: Some samples in the IMDB and Wiki datasets.
4.2 Implementation detail
In the experiments, we use GENKI-4K dataset for smile
detection, FERC-2013 for emotion recognition. We sepa-
rately use one of the two IMDB and Wiki datasets for gen-
der classification task.
Our experiments are conducted using Python
programing-language on computers with the follow-
ing specifications: Intel Xeon E5-2650 v2 Eight-Core
Processor 2.6GHz 8.0GT/s 20MB, Ubuntu Operating
352 Informatica 42 (2018) 345–356 D. Sang et al.
System 14.04 64 bit, 32GB RAM, GPU NVIDIA TITAN
X 12GB.
Preparing data: Firstly, we merge three datasets
(GENKI-4K, FERC-2013, gender dataset IMDB/Wiki) to
make a large dataset. We then create a marker vector to de-
fine sample type indicators αt
i. We always keep the num-
ber of training data for each task equally to help the learn-
ing process stability. For example, if we train our model
with two datasets: dataset A with 3000 samples, dataset B
with 30000 samples, we will duplicate dataset A 10 times
to make a big dataset with total 60000 samples.
In our work, we divide each dataset into training set and
testing set. With GENKI-4K dataset, we use 3000 samples
for training and 1000 samples for testing. With FERC-2013
dataset we use data split as provided by Kaggle. With Wiki
dataset, we use 30000 samples for training and about 4200
samples for testing. With IMDB dataset, we use 150000
samples for training and about 20000 samples for testing.
Training phase: With Multi-task BKNet architecture,
our model is trained end-to-end by using SGD algorithm
with momentum 0.9. We set the batch size equal to 128.
We initialize all weights using a Gaussian distribution with
zero mean and standard deviation 0.01. The L2 weight de-
cay is λ= 0.01. All the tasks have the same importance
level µ1=µ2=µ3= 1. The dropout rate for all fully
connected layers is set to 0.5. Moreover, we apply an ex-
ponential decay function to decay the learning rate through
time. The learning rate at step kis calculated as follows:
curLr =initLr decayRatem/decay Step ,(4)
where curLr is the learning rate at step m;initLr is
the initialization learning rate at the beginning of training
phase; decayStep is the number of steps when the learning
rate decayed.
In our experiment, we set initLr = 0.01,decayRate =
0.8and decayStep = 10000. We train our Multi-task
BKNet model in 250 epochs.
Similar to Multi-task BKNet, we train our Multi-task
ResNet end-to-end by using SGD algorithm with momen-
tum 0.9. We set the batch size equal to 128. We initial-
ize all weights using variance scaling initializer (He initial-
izer). The L2 weight decay is 104. All the tasks have the
same important level µ1=µ2=µ3= 1. We train the
Multi-task ResNet ver1 in 100 epochs and train the Multi-
task ResNet ver2 in 80 epochs. The initial learning rate is
0.05 and then decreased by 10 times whenever the training
loss stops improving.
Testing phase: In the testing phase, our model is eval-
uated by k-fold cross-validation algorithm. This method
splits our original data into kparts of the same size. The
model evaluation is performed through loops, each loop se-
lects k1parts of data as training data and the rest is
used for testing model. For the convenience of doing com-
parison between different methods, we use 4-fold cross-
validation algorithm as previous works. We will report the
average accuracy and the standard deviation after 4 itera-
tions. Moreover, we test our model with two different loss
functions mentioned above.
Furthermore, we combine different checkpoints obtained
during the training phases to infer test samples. In the pa-
per, we keep 10 last checkpoints corresponding to 10 last
training epochs for inference.
4.3 Experimental results
4.3.1 Multi-task BKNet
In this work, we set up two experiment cases. Firstly, we
train our model with GENKI-4K, FERC-2013 and Wiki
dataset. Secondly, we train our model with GENKI-4K,
FERC-2013 and IMDB dataset. Table 1 shows our experi-
ment setup.
We report our results and compare with previous meth-
ods in Table 2. As we can see, using cross-entropy loss
function gives better result than using SVM loss function
in all cases.
In smile detection task, the best accuracy we achieve is
96.23 ±0.58% when we train our model with GENKI-4K,
FERC-2013 and IMDB dataset. In all experiment cases, we
achieve better results than previous state-of-the-art meth-
ods. Especially, the Multi-task BKNet clearly outperforms
the single-task BKNet [30]. This fact proves that the smile
detection task largely benefits from other tasks thanks to
sharing the commonalities between data.
In emotion recognition task, the best accuracy
we achieve is 71.03 ±0.11% for public test and
72.18 ±0.23% for private test. This result consider-
ably outperforms all of previous methods.
In gender classification task, to the best of our knowl-
edge, there are no previous results on the Wiki and IMDB
datasets for gender classification. In this paper, we apply
the single-task BKNet model [30] and achieve the accu-
racy 95.82 ±0.44% and 91.17 ±0.27% on the Wiki and
IMDB datasets, respectively. The best accuracy we get
on Wiki is 96.33 ±0.16% when we train our Multi-task
BKNet model on Wiki. The best accuracy we get on IMDB
is 92.20 ±0.11% when we train our model on IMDB. We
also report the test accuracy on IMDB when we train the
model on Wiki, and the test accuracy on Wiki when we
train the model on IMDB.
In all tasks, the Multi-task BKNet yields comparative re-
sults and even better than the single-task BKNet in many
cases. Furthermore, it should be emphasized that the
Multi-task network can effectively solve all the three tasks
by using only a common network instead of three sepa-
rate ones, which would requires approximately three times
more memory storage and computational complexity.
4.3.2 Multi-task ResNet
Based on the experimental results of Multi-task BKNet, we
will choose the best config B4 in Table 1 to evaluate our
Effective Deep Multi-Source Multi-task Learning Frameworks Informatica 42 (2018) 345–356 353
Table 1: Experiment setup
Name Datasets Loss function Use ensemble?
Config A1 GENKI-4K, FERC-2013, IMDB SVM loss No
Config A2 GENKI-4K, FERC-2013, IMDB Cross-entropy loss No
Config A3 GENKI-4K, FERC-2013, IMDB SVM loss Yes
Config A4 GENKI-4K, FERC-2013, IMDB Cross-entropy loss Yes
Config B1 GENKI-4K, FERC-2013, Wiki SVM loss No
Config B2 GENKI-4K, FERC-2013, Wiki Cross-entropy loss No
Config B3 GENKI-4K, FERC-2013, Wiki SVM loss Yes
Config B4 GENKI-4K, FERC-2013, Wiki Cross-entropy loss Yes
Table 2: Accuracy comparison on four datasets
Method GENKI-4K FERC-2013 Wiki IMDB
Public test Private test
Chen et al [6] 91.8±0.95 - - - -
CNN Basic [42] 93.6±0.47 - - - -
CNN 2-Loss [42] 94.6±0.29 - - - -
Single-task BKNet + Softmax [30] 95.08 ±0.29 - - 95.82 ±
0.44*
91.16 ±
0.27*
CNN (team Maxim Milakov - rank 3
Kaggle) -68.2 68.8- -
CNN (team Unsupervised - rank 2
Kaggle) -69.1 69.3- -
CNN+SVM Loss (team RBM) [36] - 69.4 71.2- -
Single-task BKNet + SVM loss [31] - 71.0 71.9- -
Our Multi-task BKNet (Config A1) 95.25 ±0.43 68.10 ±0.14 69.10 ±0.57 93.33 ±0.19 89.60 ±0.22
Our Multi-task BKNet (Config A2) 95.56 ±0.66 68.47 ±0.33 69.40 ±0.21 93.67 ±0.26 90.50 ±0.24
Our Multi-task BKNet (Config A3) 95.60 ±0.41 70.43 ±0.19 71.90 ±0.36 93.70 ±0.37 91.33 ±0.42
Our Multi-task BKNet (Config A4) 96.23±0.58 70.15 ±0.19 71.62 ±0.39 94.00 ±0.24 92.20±0.11
Our Multi-task BKNet (Config B1) 95.25 ±0.44 68.60 ±0.27 69.28 ±0.41 95.25 ±0.15 88.18 ±0.26
Our Multi-task BKNet (Config B2) 95.13 ±0.20 69.12 ±0.18 69.40 ±0.22 95.75 ±0.18 88.68 ±0.15
Our Multi-task BKNet (Config B3) 95.52 ±0.37 70.63 ±0.11 71.78 ±0.08 95.95 ±0.15 88.83 ±0.18
Our Multi-task BKNet (Config B4) 95.70 ±0.25 71.03±0.11 72.18±0.23 96.33±0.16 89.34 ±0.15
Our Multi-task ResNet ver1 (Config B4) 95.55 ±0.28 70.09 ±0.13 71.55 ±0.19 96.03 ±0.22 89.01 ±0.18
Our Multi-task ResNet ver2 (Config B4) 95.30 ±0.34 69.33 ±0.31 71.27 ±0.11 95.99 ±0.14 88.88 ±0.07
Multi-task ResNet frameworks.
The results of our Multi-task ResNet are also shown in
Table 2. As one can see, our first version yields better re-
sults than the second version in all three tasks.
In smile detection task, the first version of multi-task
ResNet achieves 95.55 ±0.28% accuracy, while the sec-
ond version achieves 95.30 ±0.34% accuracy. With the
same config B4, our Multi-task BKNet model achieves
95.70 ±0.25% accuracy, which is slightly better then
Multi-task ResNet.
In emotion recognition task, the accuracy of the first
version of Multi-task ResNet is 70.09 ±0.13% for pub-
lic test set and 71.55 ±0.19% for private test set. The
accuracy of the second version is a little bit lower with
69.33 ±0.31% and 71.27 ±0.11% for public test set and
private test set, respectively. In this task, both versions of
Multi-task ResNet seem to clearly lose Multi-task BKNet,
which obtains higher approximately 1% accuracy in each
test set.
In gender classification task, both our variants of multi-
task ResNet yield pretty good results, which compete
with the results of of the multi-task BKNet model. The
first variant achieves the accuracy of 96.03 ±0.22% and
89.01 ±0.18% for Wiki dataset and IMDB dataset, re-
spectively. The second variant achieves the accuracy of
95.99 ±0.14% for Wiki dataset and 88.88 ±0.07% for
IMDB dataset.
The experiment results show that the Multi-task ResNet
is slightly worse than the Multi-task BKNet in all tasks.
The reason could be due to that ResNet with a pretty deep
architecture and fairly large number of parameters tends to
be over-complex w.r.t the mixing training data across the
three tasks and leads to overfitting. Meanwhile, BKNet is
quite smaller than ResNet, and is capable to fit the data
354 Informatica 42 (2018) 345–356 D. Sang et al.
Figure 10: Some samples that our Multi-task BKNet gives
wrong predictions.
better.
4.3.3 Speed performance comparison between
different frameworks
In Table 3 and Table 4, we show the inference time and
training time of three frameworks: Multi-task BKNet,
Multi-task ResNet ver1 and Multi-task ResNet ver2 with
Config B4 (from Table 1).
As one can see, the Multi-task ResNet ver2 acquires
the fastest convergence. Despite a little longer in training
time, Multi-task BKNet is significantly faster in inference
in comparison with both versions of Multi-task ResNet.
The fast inference with high accuracy make the Multi-task
BKNet well suitable for real-time applications.
Table 3: Comparison of inference time between different
frameworks
Framework Inference time
per image (sec)
Multi-task BKNet 0.02
Multi-task ResNet ver1 0.065
Multi-task ResNet ver2 0.071
Figure 11: Some results of our Multi-task BKNet frame-
work. The blue box corresponds to females and the red
box corresponds to males.
5 Conclusion
In this paper, we propose effective multi-souce multi-
task deep learning frameworks to jointly learn three facial
analysis tasks including smile detection, emotion recogni-
tion and gender classification. The extensive experiments
in well-known GENKI-4K, FERC-2013, Wiki, IMDB
datasets show that our frameworks achieve superior accu-
racy over recent state-of-the-art methods in all tasks. We
also show that the smile detection task with few data largely
benefit from the two other tasks with richer data.
In the future, we would like to exploit some new auxil-
iary losses to regulate the model learning process in order
to improve the performance accuracy of neural networks in
various computer vision tasks.
6 Acknowledgments
This research is funded by Hanoi University of Science and
Technology under grant number T2016-LN-08.
References
[1] Challenges in respresentation learning: Facial expres-
sion recognition challenge, 2013.
[2] Joint face detection and alignment using multitask
cascaded convolutional networks. IEEE Signal Pro-
cessing Letters, 23(10):1499–1503, 2016. https:
//doi.org/10.1109/lsp.2016.2603342.
[3] T. Ahonen, A. Hadid, and M. Pietikäinen. Face recog-
nition with local binary patterns. Computer vision-
eccv 2004, pages 469–481, 2004.
[4] L. An, S. Yang, and B. Bhanu. Efficient smile de-
tection by extreme learning machine. Neurocom-
puting, 149:354–363, 2015. https://doi.org/
10.1016/j.neucom.2014.04.072.
[5] S. Baluja, H. A. Rowley, et al. Boosting sex identi-
fication performance. International Journal of com-
puter vision, 71(1):111–119, 2007. https://doi.
org/10.1007/s11263-006-8910-9.
[6] J. Chen, Q. Ou, Z. Chi, and H. Fu. Smile de-
tection in the wild with deep convolutional neu-
ral networks. Machine vision and applications,
28(1-2):173–183, 2017. https://doi.org/10.
1007/s00138-016-0817-z.
[7] J. Chen, S. Shan, C. He, G. Zhao, M. Pietikainen,
X. Chen, and W. Gao. Wld: A robust local
image descriptor. IEEE transactions on pattern
analysis and machine intelligence, 32(9):1705–1720,
2010. https://doi.org/10.1109/tpami.
2009.155.
Effective Deep Multi-Source Multi-task Learning Frameworks Informatica 42 (2018) 345–356 355
Table 4: Comparison of training time between different frameworks
Framework Number of epochs Training time per
epoch (min)
Total training time
(min)
Multi-task BKNet 250 3.42 854
Multi-task ResNet ver1 100 8.12 817
Multi-task ResNet ver2 80 8.67 693
[8] T. F. Cootes, C. J. Taylor, et al. Statistical models of
appearance for computer vision, 2004.
[9] C. Cortes and V. Vapnik. Support vector machine.
Machine learning, 20(3):273–297, 1995.
[10] O. Déniz, G. Bueno, J. Salido, and F. De la Torre.
Face recognition using histograms of oriented gra-
dients. Pattern Recognition Letters, 32(12):1598–
1603, 2011. https://doi.org/10.1016/j.
patrec.2011.01.004.
[11] P. Ekman and E. L. Rosenberg. What the face
reveals: Basic and applied studies of sponta-
neous expression using the Facial Action Coding
System (FACS). Oxford University Press, USA,
1997. https://doi.org/10.1093/acprof:
oso/9780195179644.001.0001.
[12] B. A. Golomb, D. T. Lawrence, and T. J. Sejnowski.
Sexnet: A neural network identifies sex from human
faces. In NIPS, volume 1, page 2, 1990.
[13] K. He, X. Zhang, S. Ren, and J. Sun. Deep resid-
ual learning for image recognition. In Proceedings
of the IEEE conference on computer vision and pat-
tern recognition, pages 770–778, 2016. https:
//doi.org/10.1109/cvpr.2016.90.
[14] K. He, X. Zhang, S. Ren, and J. Sun. Identity
mappings in deep residual networks. In European
Conference on Computer Vision, pages 630–645.
Springer, 2016. https://doi.org/10.1007/
978-3-319-46493-0_38.
[15] X. He and P. Niyogi. Locality preserving projec-
tions. In Advances in neural information processing
systems, pages 153–160, 2004.
[16] G. Huang, Z. Liu, L. Van Der Maaten, and K. Q.
Weinberger. Densely connected convolutional net-
works. In CVPR, volume 1, page 3, 2017. https:
//doi.org/10.1109/cvpr.2017.243.
[17] S. Ioffe and C. Szegedy. Batch normalization: Ac-
celerating deep network training by reducing internal
covariate shift. In International Conference on Ma-
chine Learning, pages 448–456, 2015.
[18] V. Jain and J. L. Crowley. Smile detection
using multi-scale gaussian derivatives. In 12th
WSEAS International Conference on Signal Process-
ing, Robotics and Automation, 2013.
[19] L. Kaiser, A. N. Gomez, N. Shazeer, A. Vaswani,
N. Parmar, L. Jones, and J. Uszkoreit. One model
to learn them all. arXiv preprint arXiv:1706.05137,
2017.
[20] A. Krizhevsky, I. Sutskever, and G. E. Hinton. Im-
agenet classification with deep convolutional neural
networks. In Advances in neural information process-
ing systems, pages 1097–1105, 2012.
[21] Y. LeCun, L. Bottou, Y. Bengio, and P. Haffner.
Gradient-based learning applied to document recog-
nition. Proceedings of the IEEE, 86(11):2278–
2324, 1998. https://doi.org/10.1109/5.
726791.
[22] G. Levi and T. Hassner. Age and gender classifi-
cation using convolutional neural networks. In Pro-
ceedings of the IEEE Conference on Computer Vision
and Pattern Recognition Workshops, pages 34–42,
2015. https://doi.org/10.1109/cvprw.
2015.7301352.
[23] M. Liu, S. Li, S. Shan, and X. Chen. Enhancing ex-
pression recognition in the wild with unlabeled refer-
ence data. In Asian Conference on Computer Vision,
pages 577–588. Springer, 2012. https://doi.
org/10.1007/978-3-642-37444-9_45.
[24] V. Nair and G. E. Hinton. Rectified linear units im-
prove restricted boltzmann machines. In Proceed-
ings of the 27th international conference on machine
learning (ICML-10), pages 807–814, 2010.
[25] V. Ojansivu and J. Heikkilä. Blur insensitive texture
classification using local phase quantization. In Inter-
national conference on image and signal processing,
pages 236–243. Springer, 2008. https://doi.
org/10.1007/978-3-540-69905-7_27.
[26] A. J. O’toole, T. Vetter, N. F. Troje, and H. H.
Bülthoff. Sex classification is better with three-
dimensional head structure than with image inten-
sity information. Perception, 26(1):75–84, 1997.
https://doi.org/10.1068/p260075.
[27] R. Ranjan, V. M. Patel, and R. Chellappa. Hyper-
Face: A deep multi-task learning framework for face
detection, landmark localization, pose estimation,
and gender recognition. IEEE Transactions on Pat-
tern Analysis and Machine Intelligence, pages 1–1,
356 Informatica 42 (2018) 345–356 D. Sang et al.
2017. https://doi.org/10.1109/tpami.
2017.2781233.
[28] R. Rothe, R. Timofte, and L. Van Gool. Dex: Deep
expectation of apparent age from a single image.
In Proceedings of the IEEE International Confer-
ence on Computer Vision Workshops, pages 10–15,
2015. https://doi.org/10.1109/iccvw.
2015.41.
[29] D. V. Sang, L. T. B. Cuong, and V. V. Thieu.
Multi-task learning for smile detection, emotion
recognition and gender classification. In Pro-
ceedings of the Eighth International Symposium on
Information and Communication Technology, Nha
Trang City, Viet Nam, December 7-8, 2017, pages
340–347, 2017. https://doi.org/10.1145/
3155133.3155207.
[30] D. V. Sang, L. T. B. Cuong, and D. P. Thuan. Facial
smile detection using convolutional neural networks.
In The 9th International Conference on Knowledge
and Systems Engineering (KSE 2017), pages 138–
143, 2017. https://doi.org/10.1109/kse.
2017.8119448.
[31] D. V. Sang, N. V. Dat, and D. P. Thuan. Facial ex-
pression recognition using deep convolutional neu-
ral networks. In The 9th International Conference
on Knowledge and Systems Engineering (KSE 2017),
pages 144–149, 2017. https://doi.org/10.
1109/kse.2017.8119447.
[32] C. Shan. Smile detection by boosting pixel dif-
ferences. IEEE transactions on image processing,
21(1):431–436, 2012. https://doi.org/10.
1109/tip.2011.2161587.
[33] K. Simonyan and A. Zisserman. Very deep convo-
lutional networks for large-scale image recognition.
arXiv preprint arXiv:1409.1556, 2014.
[34] N. Srivastava, G. E. Hinton, A. Krizhevsky,
I. Sutskever, and R. Salakhutdinov. Dropout: a sim-
ple way to prevent neural networks from overfitting.
Journal of machine learning research, 15(1):1929–
1958, 2014.
[35] C. Szegedy, W. Liu, Y. Jia, P. Sermanet, S. Reed,
D. Anguelov, D. Erhan, V. Vanhoucke, and A. Ra-
binovich. Going deeper with convolutions. In Pro-
ceedings of the IEEE conference on computer vision
and pattern recognition, pages 1–9, 2015. https:
//doi.org/10.1109/cvpr.2015.7298594.
[36] Y. Tang. Deep learning using support vector ma-
chines. CoRR, abs/1306.0239, 2, 2013.
[37] I. Ullah, M. Hussain, G. Muhammad, H. Aboalsamh,
G. Bebis, and A. M. Mirza. Gender recognition from
face images with local wld descriptor. In Systems,
Signals and Image Processing (IWSSIP), 2012 19th
International Conference on, pages 417–420. IEEE,
2012.
[38] H. Van Kuilenburg, M. Wiering, and M. Den Uyl.
A model based method for automatic facial expres-
sion recognition. In Proceedings of the 16th Euro-
pean Conference on Machine Learning (ECML’05),
pages 194–205. Springer, 2005. https://doi.
org/10.1007/11564096_22.
[39] P. Viola and M. Jones. Fast and robust classification
using asymmetric adaboost and a detector cascade. In
Advances in neural information processing systems,
pages 1311–1318, 2002.
[40] S. Xie, R. Girshick, P. Dollár, Z. Tu, and K. He.
Aggregated residual transformations for deep neural
networks. In Computer Vision and Pattern Recog-
nition (CVPR), 2017 IEEE Conference on, pages
5987–5995. IEEE, 2017. https://doi.org/
10.1109/cvpr.2017.634.
[41] S. Zagoruyko and N. Komodakis. Wide residual net-
works. In Procedings of the British Machine Vi-
sion Conference 2016. British Machine Vision Asso-
ciation, 2016. https://doi.org/10.5244/c.
30.87.
[42] K. Zhang, Y. Huang, H. Wu, and L. Wang. Fa-
cial smile detection based on deep learning fea-
tures. In Pattern Recognition (ACPR), 2015 3rd
IAPR Asian Conference on, pages 534–538. IEEE,
2015. https://doi.org/10.1109/acpr.
2015.7486560.
... In our project, we divided the dataset into 2 folders train data and test data , each person in the dataset has 10 images , we put 8 of them in the training part and 2 in the testing part . In the age estimation there are 6 classes (0-6), (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), (25-32), (38-43), (48-53) and (+ 60), the gender "m : male" "f : female" for the label we took from the name on the images so that we renamed all the pictures for example : "Adele-1-[f,(48-53)]", "dagran-2-[m,(38-43)]". So each photo in training and test data has two labels, gender label and age group label. ...
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