“…However, discriminative methods (Li et al (2017)), (Boussaad et al (2016)), (Sajid et al (2018a)), and (Sajid et al (2018b)) focus particularly on the choice of discriminatory features and metric learning that are invariant over time. Lately, another category can be added, it includes deep-learning based methods (Wang et al (2018)), (El Khiyari et al (2016)), (El Khiyari et al (2017)), (Sajid et al (2018c)), (Zhao et al (2019)), and (Ni et al (2019)).…”