**Figure 1.**
Face detection and tracking—algorithm outline.

**Figure 1.**
Face detection and tracking—algorithm outline.

**Figure 2.**
Example image frame with the region of interest (ROI) superimposed.

**Figure 2.**
Example image frame with the region of interest (ROI) superimposed.

**Figure 3.**
HR estimation algorithm outline.

**Figure 3.**
HR estimation algorithm outline.

**Figure 4.**
An example of HR time-series plots for algorithm No.1 (PSD) and ExG signal representation: (**a**) video No.5; (**b**) video No.9.

**Figure 4.**
An example of HR time-series plots for algorithm No.1 (PSD) and ExG signal representation: (**a**) video No.5; (**b**) video No.9.

**Figure 5.**
An example of video frames: (**a**) video No.5; (**b**) video No.9.

**Figure 5.**
An example of video frames: (**a**) video No.5; (**b**) video No.9.

**Figure 6.**
Comparison of signal extraction methods, algorithm No.1 (PSD): (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 6.**
Comparison of signal extraction methods, algorithm No.1 (PSD): (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 7.**
Comparison of signal extraction methods, algorithm No.2 (AR): (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 7.**
Comparison of signal extraction methods, algorithm No.2 (AR): (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 8.**
Comparison of signal extraction methods, algorithm No.3 (TIME): (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 8.**
Comparison of signal extraction methods, algorithm No.3 (TIME): (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 9.**
Comparison of signal extraction methods, algorithm No.1 (PSD), part 1: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 9.**
Comparison of signal extraction methods, algorithm No.1 (PSD), part 1: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 10.**
Comparison of signal extraction methods, algorithm No.1 (PSD), part 2: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 10.**
Comparison of signal extraction methods, algorithm No.1 (PSD), part 2: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 11.**
Comparison of signal extraction methods, algorithm No.1 (PSD), part 4: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 11.**
Comparison of signal extraction methods, algorithm No.1 (PSD), part 4: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 12.**
Comparison of signal extraction methods, algorithm No.1 (PSD), part 6: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 12.**
Comparison of signal extraction methods, algorithm No.1 (PSD), part 6: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 13.**
Comparison of signal extraction methods, algorithm No.2 (AR), part 1: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 13.**
Comparison of signal extraction methods, algorithm No.2 (AR), part 1: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 14.**
Comparison of signal extraction methods, algorithm No.2 (AR), part 2: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 14.**
Comparison of signal extraction methods, algorithm No.2 (AR), part 2: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 15.**
Comparison of signal extraction methods, algorithm No.2 (AR), part 4: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 15.**
Comparison of signal extraction methods, algorithm No.2 (AR), part 4: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 16.**
Comparison of signal extraction methods, algorithm No.2 (AR), part 6: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 16.**
Comparison of signal extraction methods, algorithm No.2 (AR), part 6: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 17.**
Comparison of signal extraction methods, algorithm No.3 (TIME), part 1: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 17.**
Comparison of signal extraction methods, algorithm No.3 (TIME), part 1: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 18.**
Comparison of signal extraction methods, algorithm No.3 (TIME), part 2: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 18.**
Comparison of signal extraction methods, algorithm No.3 (TIME), part 2: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 19.**
Comparison of signal extraction methods, algorithm No.3 (TIME), part 4: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 19.**
Comparison of signal extraction methods, algorithm No.3 (TIME), part 4: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 20.**
Comparison of signal extraction methods, algorithm No.3 (TIME), part 6: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Figure 20.**
Comparison of signal extraction methods, algorithm No.3 (TIME), part 6: (**a**) box plots for sRate; (**b**) box plots for RMSE. Blue lines—IQR range, red line—median value.

**Table 1.**
Results of the delay estimation for selected algorithms.

**Table 1.**
Results of the delay estimation for selected algorithms.

Algorithm | t_{0} [s] | t_{1} [s] | t_{2} = t_{0} − t_{1}[s] |
---|

No.1 (PSD) | 13.4 | 3 | 10.4 |

No.2 (AR) | 6.6 | 3 | 3.6 |

No.3 (TIME) | 5.1 | 3 | 2.1 |

**Table 2.**
Recorded video sequences covered by the study.

**Table 2.**
Recorded video sequences covered by the study.

Video No. | Room Settings | Participant’s Details | Camera Parameters |
---|

1 | room 1: artificial ceiling fluorescent light + natural light (dusk, medium lighting) from a one window on the left side + light from the one computer screen | participant 1: male, ~34 years old | camera-to-face distance ~50 cm, gain = 128, white balance off |

2 | room 1: artificial ceiling fluorescent light + natural light (dusk, medium lighting) from a one window on the left side + light from the one computer screen | participant 2: male, ~22 years old | camera-to-face distance ~50 cm, gain = 128, white balance off |

3 | room 2: daylight (cloudy, poor lighting): a one roof window on the left, and a second window in the back on the right + fluorescent lamps in the back (2 m) + ceiling fluorescent lamps + right-side table lamp + light from two computer screens | participant 3: male, ~44 years old | camera-to-face distance ~50 cm, gain = 128, white balance off |

4 | room 2: daylight (cloudy, medium lighting): a one roof window on the left, and a second window in the back on the right + fluorescent lamps in the back (2 m) + ceiling fluorescent lamps + light from two computer screens | participant 3: male, ~44 years old | camera-to-face distance ~50 cm, gain = 128, white balance on |

5 | room 3: daylight (sunny, strong lighting): a one window in the front + light from the one computer screen; | participant 3: male, ~44 years old | camera-to-face distance ~60 cm (computer screen slightly lower – user has to gaze slightly downwards), gain = 100, white balance on |

6 | room 4: nighttime, artificial light only (ceiling lamps, table lamps, led curtain lamps + light from the one computer screen); | participant 3: male, ~44 years old | camera-to-face distance ~50 cm (computer screen slightly lower – user has to gaze slightly downwards), gain = 128, white balance on |

7 | room 3: daylight (cloudy, medium lighting): a one window in the front + light from the one computer screen; | participant 4: female, ~42 years old | camera-to-face distance ~60 cm (computer screen slightly lower – user has to gaze slightly downwards), gain = 128, white balance on |

8 | room 2: daylight (cloudy, poor lighting): a one roof window on the left, and a second window in the back on the right + fluorescent lamps in the back (2 m) + light from two computer screens; | participant 3: male, ~44 years old | camera-to-face distance ~50 cm, gain = 100, white balance off |

9 | room 5: artificial ceiling fluorescent light + natural light (dusk, medium lighting) from a one window on the right side + right side bulb lamp + light from the one computer screen; | participant 5: male, ~23 years old | camera-to-face distance ~60 cm, gain = 128, white balance on |

**Table 3.**
The median sRate and RMSE for selected algorithms and signal extraction methods.

**Table 3.**
The median sRate and RMSE for selected algorithms and signal extraction methods.

Algorithm | RMSE [bpm] | sRate [%] |
---|

| G | GRD | ExG | ICA | G | GRD | ExG | ICA |
---|

PSD | 10.7 | 13.5 | 11.1 | 4.0 | 47% | 49% | 65% | 78% |

AR | 15.6 | 12.3 | 11.6 | 5.8 | 48% | 45% | 61% | 48% |

TIME | 16.8 | 13.1 | 10.9 | 8.6 | 35% | 43% | 45% | 26% |

average | 14.4 | 13.0 | 11.2 | 6.1 | 43% | 46% | 57% | 51% |