Physiological information is extracted from detected electromagnetic radiation emitted or reflected by a subject (10). A data stream (30) derivable from the electromagnetic radiation is received. The data stream (30) includes a sequence (76 152) of signal samples (78a, 78b, 78c 154a, 154b, 154c) indicative of desired subject motion and of disturbing motion, the signal samples representing at least one region of interest (84 164) and at least one non-indicative motion region (86 166). The at least one defined region of interest (84 164) exhibiting an at least partially periodic indicative motion pattern attributable to at least one physiological parameter (56), and a disturbing motion portion. A sequence (158) of motion compensated samples (80 160a, 160b, 160c) at least partially compensated for undesired overall motion is derived. At least one characteristic signal (90 112) at least partially indicative of the at least partially periodic indicative motion pattern is derived from the sequence (158) of derived motion compensated samples (80 160a, 160b, 160c).
