1 INTRODUCTION

2 DATASETS

3 A TAXONOMY FOR MER BASED ON DL

4 INPUTS  
4.1 Pre-processing  
4.2 Input modality  
4.3 Discussion  

5 DEEP NETWORKS FOR MER  
5.1 Network block  
5.2 Network architecture  
5.3 Training strategy  
5.4 Loss functions  
5.5 Discussion  

6 EXPERIMENTS  
6.1 Evaluation matrix  
6.2 Model evaluation protocols  

7 CHALLENGES AND FUTURE DIRECTIONS  
7.1 Dealing with small-scale dataset  
7.2 3D ME sequence  
7.3 AU analysis in MEs  
7.4 Multi-modal MER  
7.5 The explainability of MER based on DL  
7.6 MEs in realistic situations