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  1. The increased ubiquitousness of small smart devices, such as cell- phones, tablets, smart watches and laptops, has led to unique user data, which can be locally processed. The sensors (e.g., microphones and webcam) and improved hardware of the new devices have al- lowed running deep learning models that 20 years ago would have been exclusive to high-end expensive machines. In spite of this progress, state-of-the-art algorithms for facial expression recognition (FER) rely on architectures that cannot be implemented on these devices due to computational and memory constraints. Alternatives involving cloud-based solutions impose privacy barriers that prevent their adoption or user acceptance in wide range of applications. This paper proposes a lightweight model that can run in real-time for image facial expression recognition (IFER) and video facial expression recognition (VFER). The approach relies on a personalization mechanism locally implemented for each subject by fine-tuning a central VFER model with unlabeled videos from a target subject. We train the IFER model to generate pseudo labels and we select the videos with the highest confident predictions to be used for adaptation. The adaptation is performed by implementing a federated learning strategy where the weights of the local model are averaged and used bymore »the central VFER model. We demonstrate that this approach can improve not only the performance on the edge device providing personalized models to the users, but also the central VFER model. We implement a federated learning strategy where the weights of the local models are averaged and used by the central VFER. Within corpus and cross-corpus evaluations on two emotional databases demonstrate that edge models adapted with our personalization strategy achieve up to 13.1% gains in F1-scores. Furthermore, the federated learning implementation improves the mean micro F1-score of the central VFER model by up to 3.4%. The proposed lightweight solution is ideal for interactive user interfaces that preserve the data of the users.« less
    Free, publicly-accessible full text available November 7, 2023
  2. Free, publicly-accessible full text available October 1, 2023
  3. Speech emotion recognition (SER) is a challenging task due to the limited availability of real-world labeled datasets. Since it is easier to find unlabeled data, the use of self-supervised learning (SSL) has become an attractive alternative. This study proposes new pre-text tasks for SSL to improve SER. While our target application is SER, the proposed pre-text tasks include audio-visual formulations, leveraging the relationship between acoustic and facial features. Our proposed approach introduces three new unimodal and multimodal pre-text tasks that are carefully designed to learn better representations for predicting emotional cues from speech. Task 1 predicts energy variations (high or low) from a speech sequence. Task 2 uses speech features to predict facial activation (high or low) based on facial landmark movements. Task 3 performs a multi-class emotion recognition task on emotional labels obtained from combinations of action units (AUs) detected across a video sequence. We pre-train a network with 60.92 hours of unlabeled data, fine-tuning the model for the downstream SER task. The results on the CREMA-D dataset show that the model pre-trained on the proposed domain-specific pre-text tasks significantly improves the precision (up to 5.1%), recall (up to 4.5%), and F1-scores (up to 4.9%) of our SER system.
    Free, publicly-accessible full text available September 18, 2023
  4. Expressive behaviors conveyed during daily interactions are difficult to determine, because they often consist of a blend of different emotions. The complexity in expressive human communication is an important challenge to build and evaluate automatic systems that can reliably predict emotions. Emotion recognition systems are often trained with limited databases, where the emotions are either elicited or recorded by actors. These approaches do not necessarily reflect real emotions, creating a mismatch when the same emotion recognition systems are applied to practical applications. Developing rich emotional databases that reflect the complexity in the externalization of emotion is an important step to build better models to recognize emotions. This study presents the MSP-Face database, a natural audiovisual database obtained from video-sharing websites, where multiple individuals discuss various topics expressing their opinions and experiences. The natural recordings convey a broad range of emotions that are difficult to obtain with other alternative data collection protocols. A feature of the corpus is the addition of two sets. The first set includes videos that have been annotated with emotional labels using a crowd-sourcing protocol (9,370 recordings – 24 hrs, 41 m). The second set includes similar videos without emotional labels (17,955 recordings – 45 hrs, 57more »m), offering the perfect infrastructure to explore semi-supervised and unsupervised machine-learning algorithms on natural emotional videos. This study describes the process of collecting and annotating the corpus. It also provides baselines over this new database using unimodal (audio, video) and multimodal emotional recognition systems.« less
  5. The performance of facial expression recognition (FER) systems has improved with recent advances in machine learning. While studies have reported impressive accuracies in detecting emotion from posed expressions in static images, there are still important challenges in developing FER systems for videos, especially in the presence of speech. Speech articulation modulates the orofacial area, changing the facial appearance. These facial movements induced by speech introduce noise, reducing the performance of an FER system. Solving this problem is important if we aim to study more naturalistic environment or applications in the wild. We propose a novel approach to compensate for lexical information that does not require phonetic information during inference. The approach relies on a style extractor model, which creates emotional-to-neutral transformations. The transformed facial representations are spatially contrasted with the original faces, highlighting the emotional information conveyed in the video. The results demonstrate that adding the proposed style extractor model to a dynamic FER system improves the performance by 7% (absolute) compared to a similar model with no style extractor. This novel feature representation also improves the generaliza- tion of the model.
  6. Articulation, emotion, and personality play strong roles in the orofacial movements. To improve the naturalness and expressiveness of virtual agents(VAs), it is important that we carefully model the complex interplay between these factors. This paper proposes a conditional generative adversarial network, called conditional sequential GAN(CSG), which learns the relationship between emotion, lexical content and lip movements in a principled manner. This model uses a set of spectral and emotional speech features directly extracted from the speech signal as conditioning inputs, generating realistic movements. A key feature of the approach is that it is a speech-driven framework that does not require transcripts. Our experiments show the superiority of this model over three state-of-the-art baselines in terms of objective and subjective evaluations. When the target emotion is known, we propose to create emotionally dependent models by either adapting the base model with the target emotional data (CSG-Emo-Adapted), or adding emotional conditions as the input of the model(CSG-Emo-Aware). Objective evaluations of these models show improvements for the CSG-Emo-Adapted compared with the CSG model, as the trajectory sequences are closer to the original sequences. Subjective evaluations show significantly better results for this model compared with the CSG model when the target emotion is happiness.