Figure 3.

Example of the transformation of a period for data augmentation, with relatively high changes in the Doppler FHR channel (in blue) and the MHR channel (in purple). (a) The raw data in a period. (b) The period after random transformation. Expert annotations are shown as colored zones. Data augmentation consisted in adding MS and FS on both the FHR and MHR channels. Moreover, both the MHR and the FHR were multiplied by a $\lambda \approx 0.9$. The final signal corresponds to poor quality recordings but remains realistic. It should be noted that the MHR and FHR were not annotated by the experts for the entire recording (either because the experts were uncertain, or the period did not contain difficult-to-interpret features).