The present invention relates to fields of medical technology and camera-based vital signs monitoring using remote photoplethysmography (rPPG). A Device (10) for determining a physiological parameter of a subject (20) is presented, the device comprising: an interface (11) for receiving image data of a scene, said image data comprising a time-sequence of image frames； and a processor (12) for processing said image data, wherein the processor is configured to perform, for each of said image frames, the steps of: generating a set of weighting maps comprising at least a first weighting map and a second weighting map for weighting pixels of the image frame (102)； determining a first weighted image frame by weighting pixels of the image frame based on the first weighting map (103)； determining a second weighted image frame by weighting pixels of the image frame based on the second weighting map (104)； determining a first statistical parameter value based on the first weighted image frame (105)； determining a second statistical parameter value based on the second weighted image frame (106)； wherein the processor is further configured to perform the steps of: concatenating said first statistical parameter values over time based on the time-sequence of the corresponding image frames to obtain a first candidate signal (107)； concatenating said second statistical parameter values over time based on the time-sequence of the corresponding image frames to obtain a second candidate signal (108)； extracting a physiological parameter of the subject based on said first and/or said second candidate signal (109). The present invention further relates to a corresponding system (1) and method (100).L'invention concerne la surveillance de signes vitaux basés sur une caméra utilisant la PPG à distance. Un dispositif (10) permettant de déterminer un paramètre physiologique comprend : une interface (11) pour recevoir des données d'image comprenant une séquence temporelle de trames d'image ；
