“…Although FER systems have recently been improved due to deep learning techniques and technological advances, there are still some limitations to overcome, which include the following: - Lack of diverse databases causing a need for the acquisition of new large databases with a high level of annotation quality [ 39 , 46 , 53 , 56 , 83 , 124 , 161 , 164 ];
- The proposed methods do not provide better accuracy than the ones described in the literature, or the model achieved performance on par with state-of-the-art methods [ 49 , 50 , 92 ];
- Misclassifications between emotions (such as ”sad” and “angry”) which indicates that the system needs further improvements [ 58 , 120 , 162 , 165 , 175 ];
- Proposed architectures are usually characterized by high complexity [ 32 , 33 , 41 , 43 , 64 , 78 , 114 , 141 , 163 ];
- Small number of recognized emotions [ 45 , 90 , 93 , 116 , 160 ];
- The proposed model is built to recognize facial expressions on static images which may limit its applicability [ 68 , 73 ].
…”