Phase-step detection¶

Fit a regular train before and after a candidate break and test for a step in its phase, accepting only steps without an intervening beat that could explain them.


Methods	Clocks carried in the signal

Studies¶

Study	Date	Status	Summary
Paced ECG as an independent clock	2026-10-17	current	Fixed-rate pacing gives a clock the recording chain cannot touch. Timing paced beats on three timelines shows that each SNUADC step-mode correction loses about 18 ms of signal, and that nothing else breaks the sample stream.
Where the PPG sawtooth stops	2026-10-11	current	In some stretches no slip comes although several were due. The PPG delay there is flat, not hidden: the monitor keeps framing, and only the content's drift against the frames has stopped.
The PPG's 30 Hz frame clock	2026-10-10	current	ECG and PPG fiducials resolve to one 2 ms sample, but PPG fiducials taken on raw samples lock to a hidden 33.3 ms frame grid. Scanning for it finds the oximeter's frame clock to about 1 ppm, a fixed fingerprint of each recording setup.
The PPG sawtooth and its correction	2026-10-10	current	The ECG→PPG delay creeps at 18–52 ppm and jumps up by one 33.3 ms frame at each slip, every 11–31 minutes. A tooth-by-tooth model removes it; where the correction is confident it is essentially exact on injected test data.