> ## Documentation Index
> Fetch the complete documentation index at: https://docs.medera.info/llms.txt
> Use this file to discover all available pages before exploring further.

# Heart Rate

> rPPG-derived HR with < 5 bpm MAE

HR is extracted by `_extract_heart_rate(signal, fps)` from the CHROM-processed rPPG signal.

| Aspect           | Value                                                 |
| :--------------- | :---------------------------------------------------- |
| Accuracy         | \< 5 bpm MAE at SNR > 3.0                             |
| Minimum duration | 30 s (set via `min_hr_duration`)                      |
| Signal           | CHROM rPPG → bandpass \[0.7, 4.0] Hz → SciPy FFT peak |
| Output           | `heart_rate` (bpm), `heart_rate_confidence` (0–1)     |

If the minimum duration is not met or SNR ≤ 3.0, the engine returns `heart_rate = None` and `heart_rate_confidence = 0.0`. There is no fabrication.