Abstract: A photoplethysmography or PPG signal processing device configured to detect atrial flutter, includes a processor and memory including computer program code The processor and memory are configured to cause the PPG signal processing device to obtain (101) at least one PPG signal (200) for a human or animal; detect (102) heartbeats (201, 202, 203, 204, 205, . . . ) in the at least one PPG signal (200); and determine (103) interbeat intervals (301, 302, 303, 304, . . . ) for pairs of consecutive heartbeats (201-202, 202-203, 203-204, 204-205, . . . ) in the at least one PPG signal (200). The processor and memory cause the PPG signal processing device to detect (104) interbeat interval baselines, each interbeat interval baseline (302-304) corresponding to a plurality of consecutive interbeat intervals (302, 303, 304) that are constant within a predefined tolerance value; determine (105) respective average interbeat interval values (401, 402, . . .

Abstract: A computer-implemented method for direct photoplethysmography or direct PPG comprises obtaining during a time interval plural PPG signals for respective sensors in a wearable device; and combining the plural PPG signals to thereby obtain a multi-sensor PPG signal.

Abstract: A computer-implemented method for contact photoplethysmography, abbreviated contact PPG, comprises obtaining during a time interval plural PPG signals for sub-regions of a lens or video frame; and combining the plural PPG signals to thereby obtain a multi-region PPG signal.