  Breathing rate is a vital health metric that is an invaluable indicator of
the overall health of a person. In recent years, the non-contact measurement of
health signals such as breathing rate has been a huge area of development, with
a wide range of applications from telemedicine to driver monitoring systems.
This paper presents an investigation into a method of non-contact breathing
rate detection using a motion detection algorithm, optical flow. Optical flow
is used to successfully measure breathing rate by tracking the motion of
specific points on the body. In this study, the success of optical flow when
using different sets of points is evaluated. Testing shows that both chest and
facial movement can be used to determine breathing rate but to different
degrees of success. The chest generates very accurate signals, with an RMSE of
0.63 on the tested videos. Facial points can also generate reliable signals
when there is minimal head movement but are much more vulnerable to noise
caused by head/body movements. These findings highlight the potential of
optical flow as a non-invasive method for breathing rate detection and
emphasize the importance of selecting appropriate points to optimize accuracy.
