  Over the last few years, automatic facial micro-expression analysis has
garnered increasing attention from experts across different disciplines because
of its potential applications in various fields such as clinical diagnosis,
forensic investigation and security systems. Advances in computer algorithms
and video acquisition technology have rendered machine analysis of facial
micro-expressions possible today, in contrast to decades ago when it was
primarily the domain of psychiatrists where analysis was largely manual.
Indeed, although the study of facial micro-expressions is a well-established
field in psychology, it is still relatively new from the computational
perspective with many interesting problems. In this survey, we present a
comprehensive review of state-of-the-art databases and methods for
micro-expressions spotting and recognition. Individual stages involved in the
automation of these tasks are also described and reviewed at length. In
addition, we also deliberate on the challenges and future directions in this
growing field of automatic facial micro-expression analysis.
