In recent years, speech emotion recognition technology is of great significance in widespread applications such as call centers, social robots and health care. Thus, the speech emotion recognition has been attracted much attention in both industry and academic. Since emotions existing in an entire utterance may have varied probabilities, speech emotion is likely to be ambiguous, which poses great challenges to recognition tasks. However, previous studies commonly assigned a single-label or multi-label to each utterance in certain. Therefore, their algorithms result in low accuracies because of the inappropriate representation. Inspired by the optimally interacting theory, we address the ambiguous speech emotions by proposing a novel multi-classifier interactive learning (MCIL) method. In MCIL, multiple different classifiers first mimic several individuals, who have inconsistent cognitions of ambiguous emotions, and construct new ambiguous labels (the emotion probability distribution). Then, they are retrained with the new labels to interact with their cognitions. This procedure enables each classifier to learn better representations of ambiguous data from others, and further improves the recognition ability. The experiments on three benchmark corpora (MAS, IEMOCAP, and FAU-AIBO) demonstrate that MCIL does not only improve each classifier’s performance, but also raises their recognition consistency from moderate to substantial.

Deep Learning has achieved remarkable successes in many industry applications and scientific research fields. One essential reason is that deep models can learn rich information from large-scale training datasets through supervised learning. It has been well accepted that the robust deep models heavily rely on the quality of data labels. However, current large-scale datasets mostly involve noisy labels, which are caused by sensor errors, human mistakes, or inaccuracy of search engines, and may severely degrade the performance of deep models. In this survey, we summaries existing works on noisy label learning into two main categories, Loss Correction and Sample Selection, and present their methodologies, commonly used experimental setups, datasets, and the state-of-the-art results. Finally, we discuss a promising research direction that might be valuable for the future study.

Scatter targets of complex land covers in polarimetric synthetic aperture radar (PolSAR) images are often randomly oriented and cause randomly fluctuating echoes, which brings a challenge to PolSAR image classification. Therefore, many existing methods have alleviated this problem through orientation compensation. However, there are still two obstacles that limit the improvement of classification accuracy. On the one hand, generally, these methods process PolSAR images with fixed polarization rotation angles, which is experience-dependent and inflexible. On the other hand, for the different land covers of a PolSAR image, the existing methods do not consider these rotation angles separately. For the first obstacle, we design a group of convolution kernels called polarization rotation kernels (PRKs) and utilize them to build the polarimetric convolutional neural network (CNN) (PolCNN). The PolCNN is the base network of our final model, and it can learn polarization rotation angles adaptively. For the second obstacle, we extend the PolCNN into a multipath structure, the final model polarimetric multipath CNN (PolMPCNN). The polarization rotation angles of different land covers are directly related to the networks of different paths within the PolMPCNN. Furthermore, we also put forward the two-scale sampling and the stagewise training algorithm in order that our PolMPCNN can fit different scales of PolSAR targets and pays more attention to difficult training samples. Experiments on real PolSAR images show that the proposed model achieves the best classification results with an extremely low sampling rate of 0.1%.

Outlier detection is to separate anomalous data from inliers in the dataset. Recently, the most deep learning methods of outlier detection leverage an auxiliary reconstruction task by assuming that outliers are more difficult to recover than normal samples (inliers). However, it is not always true in deep auto-encoder (AE) based models. The auto-encoder based detectors may recover certain outliers even if outliers are not in the training data, because they do not constrain the feature learning. Instead, we think outlier detection can be done in the feature space by measuring the distance between outliers’ features and the consistency feature of inliers. To achieve this, we propose an unsupervised outlier detection method using a memory module and a contrastive learning module (MCOD). The memory module constrains the consistency of features, which merely represent the normal data. The contrastive learning module learns more discriminative features, which boosts the distinction between outliers and inliers. Extensive experiments on four benchmark datasets show that our proposed MCOD performs well and outperforms eleven state-of-the-art methods.

Multimodal Emotion Recognition (MER) may encounter incomplete multimodal scenarios caused by sensor damage or privacy protection in practical applications. Existing incomplete multimodal learning methods focus on learning better joint representations across modalities. However, our investigation shows that they are lacking in learning the unimodal representations which are rather discriminative as well. Instead, we propose a novel framework named Mixture of Modality Knowledge Experts (MoMKE) with two-stage training. In unimodal expert training, each expert learns the unimodal knowledge from the corresponding modality. In experts mixing training, both unimodal and joint representations are learned by leveraging the knowledge of all modality experts. In addition, we design a special Soft Router that can enrich the modality representations by dynamically mixing the unimodal representations and the joint representations. Various incomplete multimodal experiments on three benchmark datasets showcase the robust performance of MoMKE, especially on severely incomplete conditions. Visualization analysis further reveals the considerable value of unimodal and joint representations. Codes are realised at https://github.com/wxxv/MoMKE.