Comprehensive review and analysis on facial emotion recognition methods

Facial emotion recognition (FER) is a significant subject in computer vision and artificial intelligence because of its tremendous academic and commercial potential, such as in cognitive science, health care, virtual reality, and video conferencing in various domains. While FER could be carried out using multiple sensors, this review includes research that exclusively uses face images, since facial expressions are among the key pieces of knowledge in human interactions. We give a brief review of FER research carried out in recent years. We divided the techniques of FER mainly into two parts, i.e., based on the type of approach and based on the type of frame, which is further subdivided into two sub-parts of each classification for more detailed division. First, it explains traditional FER approaches together with a description of the representative classes of FER systems. Deep-learning FER strategies are then addressed using deep networks that allow "end-to-end" learning. This review is also directed toward an up-to-date deep learning strategy, which is a trending topic nowadays. A brief overview of publicly accessible assessment metrics is provided in the later part of this paper, as well as a comparison with the baseline results is presented, which is a norm for quantitative analysis of FER research. The whole analysis also could act as a concise field guide for beginners in the FER sector, providing general details and a common understanding of both the recent state-of-the-art research and established researchers searching for fruitful areas for further research. (c) 2023 SPIE and IS&T