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1. Deepemocluster: a Semi-Supervised Framework for Latent Cluster Representation of Speech Emotions

   https://doi.org/10.1109/ICASSP39728.2021.9414035  

   Lin, Wei-Cheng ; Sridhar, Kusha ; Busso, Carlos ( June 2021 , IEEE international conference on acoustics, speech and signal processing (ICASSP 2021))

   null (Ed.)

   Semi-supervised learning (SSL) is an appealing approach to resolve generalization problem for speech emotion recognition (SER) systems. By utilizing large amounts of unlabeled data, SSL is able to gain extra information about the prior distribution of the data. Typically, it can lead to better and robust recognition performance. Existing SSL approaches for SER include variations of encoder-decoder model structures such as autoencoder (AE) and variational autoencoders (VAEs), where it is difficult to interpret the learning mechanism behind the latent space. In this study, we introduce a new SSL framework, which we refer to as the DeepEmoCluster framework, for attribute-based SER tasks. The DeepEmoCluster framework is an end-to-end model with mel-spectrogram inputs, which combines a self-supervised pseudo labeling classification network with a supervised emotional attribute regressor. The approach encourages the model to learn latent representations by maximizing the emotional separation of K-means clusters. Our experimental results based on the MSP-Podcast corpus indicate that the DeepEmoCluster framework achieves competitive prediction performances in fully supervised scheme, outperforming baseline methods in most of the conditions. The approach can be further improved by incorporating extra unlabeled set. Moreover, our experimental results explicitly show that the latent clusters have emotional dependencies, enriching the geometric interpretation of the clusters. 

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2. An Efficient Temporal Modeling Approach for Speech Emotion Recognition by Mapping Varied Duration Sentences into Fixed Number of Chunks

   https://doi.org/10.21437/Interspeech.2020-2636  

   Lin, Wei-Cheng ; Busso, Carlos ( October 2020 , Interspeech 2020)

   null (Ed.)

   Speech emotion recognition (SER) plays an important role in multiple fields such as healthcare, human-computer interaction (HCI), and security and defense. Emotional labels are often annotated at the sentence-level (i.e., one label per sentence), resulting in a sequence-to-one recognition problem. Traditionally, studies have relied on statistical descriptions, which are com- puted over time from low level descriptors (LLDs), creating a fixed dimension sentence-level feature representation regardless of the duration of the sentence. However sentence-level features lack temporal information, which limits the performance of SER systems. Recently, new deep learning architectures have been proposed to model temporal data. An important question is how to extract emotion-relevant features with temporal infor- mation. This study proposes a novel data processing approach that extracts a fixed number of small chunks over sentences of different durations by changing the overlap between these chunks. The approach is flexible, providing an ideal frame- work to combine gated network or attention mechanisms with long short-term memory (LSTM) networks. Our experimental results based on the MSP-Podcast dataset demonstrate that the proposed method not only significantly improves recognition accuracy over alternative temporal-based models relying on LSTM, but also leads to computational efficiency. 

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3. Exploiting Co-occurrence Frequency of Emotions in Perceptual Evaluations To Train A Speech Emotion Classifier

   https://doi.org/10.21437/Interspeech.2022-11041  

   Chou, Huang-Cheng ; Lee, Chi-Chun ; Busso, Carlos ( September 2022 , Interspeech 2022)

   Previous studies on speech emotion recognition (SER) with categorical emotions have often formulated the task as a single-label classification problem, where the emotions are considered orthogonal to each other. However, previous studies have indicated that emotions can co-occur, especially for more ambiguous emotional sentences (e.g., a mixture of happiness and sur- prise). Some studies have regarded SER problems as a multi-label task, predicting multiple emotional classes. However, this formulation does not leverage the relation between emotions during training, since emotions are assumed to be independent. This study explores the idea that emotional classes are not necessarily independent and its implications on training SER models. In particular, we calculate the frequency of co-occurring emotions from perceptual evaluations in the train set to generate a matrix with class-dependent penalties, punishing more mistakes between distant emotional classes. We integrate the penalization matrix into three existing label-learning approaches (hard-label, multi-label, and distribution-label learn- ing) using the proposed modified loss. We train SER models using the penalty loss and commonly used cost functions for SER tasks. The evaluation of our proposed penalization matrix on the MSP-Podcast corpus shows important relative improvements in macro F1-score for hard-label learning (17.12%), multi-label learning (12.79%), and distribution-label learning (25.8%). 

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4. Chunk-Level Speech Emotion Recognition: A General Framework of Sequence-to-One Dynamic Temporal Modeling

   https://doi.org/10.1109/TAFFC.2021.3083821  

   Lin, Wei-Cheng ; Busso, Carlos ( May 2021 , IEEE Transactions on Affective Computing)

   null (Ed.)

   A critical issue of current speech-based sequence-to-one learning tasks, such as speech emotion recognition (SER), is the dynamic temporal modeling for speech sentences with different durations. The goal is to extract an informative representation vector of the sentence from acoustic feature sequences with varied length. Traditional methods rely on static descriptions such as statistical functions or a universal background model (UBM), which are not capable of characterizing dynamic temporal changes. Recent advances in deep learning architectures provide promising results, directly extracting sentence-level representations from frame-level features. However, conventional cropping and padding techniques that deal with varied length sequences are not optimal, since they truncate or artificially add sentence-level information. Therefore, we propose a novel dynamic chunking approach, which maps the original sequences of different lengths into a fixed number of chunks that have the same duration by adjusting their overlap. This simple chunking procedure creates a flexible framework that can incorporate different feature extractions and sentence-level temporal aggregation approaches to cope, in a principled way, with different sequence-to-one tasks. Our experimental results based on three databases demonstrate that the proposed framework provides: 1) improvement in recognition accuracy, 2) robustness toward different temporal length predictions, and 3) high model computational efficiency advantages. 

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5. Expressive Speech-Driven Lip Movements with Multitask Learning

   https://doi.org/10.1109/FG.2018.00066  

   Sadoughi, Najmeh ; Busso, Carlos ( May 2018 , IEEE Conference on Automatic Face and Gesture Recognition (FG 2018))

   The orofacial area conveys a range of information, including speech articulation and emotions. These two factors add constraints to the facial movements, creating non-trivial integrations and interplays. To generate more expressive and naturalistic movements for conversational agents (CAs) the relationship between these factors should be carefully modeled. Data-driven models are more appropriate for this task than rule-based systems. This paper provides two deep learning speech-driven structures to integrate speech articulation and emotional cues. The proposed approaches rely on multitask learning (MTL) strategies, where related secondary tasks are jointly solved when synthesizing orofacial movements. In particular, we evaluate emotion recognition and viseme recognition as secondary tasks. The approach creates shared representations that generate behaviors that not only are closer to the original orofacial movements, but also are perceived more natural than the results from single task learning. 

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