Facial emotion recognition (FER) is an important topic in the fields of Computer Vision and Artificial intelligence owing to its significant academic and commercial potential. Although FER can be conducted using multiple sensors, this paper focuses on studies that exclusively use facial images, because visual expressions are main information channels in interpersonal communication. Lot of research was conducted over past few decades in the field of FER. Conventional FER approaches are described along with a summary of the representative categories of FER systems and their main algorithms initially. Later, implementation of deep-learning-based FER approaches using deep networks enabling “end-to-end” learning are described

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