The present disclosure relates to signal processing and, more particularly, to determining the value of a physiological parameter, such as the blood oxygen saturation (SpO2) of a subject. In an embodiment, a first baseline for a first waveform and a second baseline for a second waveform are determined. In this embodiment, the first and second waveforms are indicative of the physiological parameter of the subject. The first and second waveforms are filtered to obtain a first direct-current (DC) component for the first waveform and a second DC component for the second waveform. A measured value for the physiological parameter is derived from the first and second baseline signals, and the first and second DC components. In an embodiment, the measured value for the physiological parameter is determined based on a ratio of the normalized difference between the DC component and the baseline signal for the first waveform with respect to same for the second waveform.
