BreathLink · drawing set · v1.0
Part I · Cover Docket · Abstract · v1.0 figures/claims alignment
- Philips Biosensing-by-rPPG · foundational IP, licensing program
- NuraLogix Anura (2023) · closest commercial · vitals during video calls, single-participant
- Binah.ai SDK · Lifelight (Class II) · commercial rPPG SaaS
- Wu et al. SIGGRAPH '12 — single-source Eulerian VM
- Verkruysse '08 — single-source rPPG
- All cited rPPG art is single-participant · this is inter-participant coherence
- Speech-gating to avoid turn-taking false decoherence
- Peer-to-peer · no server aggregator (cf. cloud SaaS)
- Ambient (non-corrective) UI per "synchrony decouples self" (bioRxiv '25)
- Outbound rPPG suppression (claim 9) — separate novelty
- Dyadic ANS synchrony (Frontiers '21) — lab dyads, contact sensors
- Zoom AI Companion · Calm-app — different modalities entirely
- Sheet 1 FIG. 1 Two-tile video call · breath ROIs 100
- Sheet 2 FIG. 2 Coherence trace · breath in phase / out of phase 200
- Sheet 3 FIG. 3 Per-side pipeline · ROI → VM → respiration 300
- Sheet 4 FIG. 4 Peer-host coherence · symmetric · no aggregator 400
- Sheet 5 FIG. 5 Outbound rPPG suppression · local-only physiology 500
Part II · Drawings FIG. 1 – 5 · Sheets 1 – 5
Part III · Specification Background · Summary · Brief description
Eulerian Video Magnification (Wu et al., SIGGRAPH 2012) and the broader sub-pixel motion-magnification family enable recovery of respiration and pulse signals from ordinary video. Remote photoplethysmography (rPPG; Verkruysse et al., 2008; and later) recovers heart-rate from facial colour variation in webcam feeds. Both literatures focus on the per-source physiological signal.
A parallel literature establishes that interacting dyads spontaneously synchronize cardiac, respiratory, and electrodermal rhythms during naturalistic conversation, with the strength of synchrony correlating with engagement and reciprocity (Frontiers in Neuroscience 2021; Cognition 2022; and related work). That literature is uniformly built on contact sensors (chest belts, ECG, EDA) under laboratory conditions; it does not address recovery of the signals from a camera stream already in use for a video-conferencing session, nor the conversion of the synchrony measurement into an in-session UX surface.
Two findings from the dyadic-synchrony literature constrain the UX claim. First, interpersonal respiratory synchronization can coincide with intra-personal cardiorespiratory decoupling (bioRxiv 2025), so a UX that pushes participants toward synchrony may not be physiologically benign. Second, dyadic respiratory synchrony is driven by the predictability and stability of each participant's rhythm, not by online mutual adaptation (Cognition 2022); nudging toward a target γ may therefore target the wrong variable. The disclosed system accordingly surfaces an ambient indicator rather than a corrective nudge: the indicator reflects the current state to the participants, who may attend or ignore.
A second, distinct threat motivates the outbound suppression of physiological signal. The same recovery primitives, applied in reverse by a recipient of the conferencing video, allow a peer, a conferencing platform, or any downstream consumer of the transmitted stream to infer heart rate, respiration, and stress correlates of a participant who is unaware that such inference is tractable on ordinary video. Nature Communications Engineering (2025) demonstrates the attack on standard video streams and characterizes signal-suppression countermeasures. The disclosed system addresses this threat directly: the same primitive that enables the disclosed coherence UX, applied to the unmodulated local source, is rendered non-recoverable on the outbound stream by a sub-pixel modulation that preserves perceptual video quality. The local UX and the outbound privacy posture are thus two faces of the same observation: that respiration and pulse are present in any reasonable webcam stream and that the question is which observers are permitted to see them.
The disclosed system applies the per-source primitives in the multi-participant video-conferencing context and treats the pairwise coherence of the recovered signals as a UX-surfaceable metric, gated to intervals of bilateral non-speech detected from the existing conferencing audio stream so that ordinary turn-taking anti-phase respiration is not misread as decoherence.
Stated structurally — and this is the load-bearing framing of the disclosure — the system is symmetric and peer-to-peer, recruits no auxiliary physiological sensor, and depends on no third-party aggregator. Each host independently computes its own γ from its own respiration trace and the traces of its peers, exchanged only over the conferencing session's own data channel. There is no biometric server in the architecture. This distinguishes the disclosed method from any inter-participant physiological-coherence system that funnels traces to a backend (e.g. Apple Health cloud, hospital telemetry aggregation, or wellness-platform analytics), and from any chest-strap / wearable inter-participant coupling system that adds physical sensors to the conferencing setup.
The disclosed system computes inter-participant respiratory coherence symmetrically and peer-to-peer, using only the webcam already running in the conferencing session, with no auxiliary physiological sensor and no third-party aggregator. At each participant's local host, ROI tracker (304) selects lower-face landmarks within the host's outgoing webcam frames (302), with chest landmarks used as a fallback when in frame. VM block (306) applies Eulerian-style sub-pixel motion magnification to the ROI to recover a respiration trace (308) within an adaptive band centered on each participant's detected respiration mode. Per-host respiration traces are exchanged peer-to-peer over the existing conferencing data channel; each host computes pairwise coherence γ symmetrically over a sliding analysis window, restricted to intervals of bilateral non-speech detected from the existing conferencing audio stream. Upon sustained crossing of γ below a configured threshold, the conferencing UI surfaces an ambient indicator reflecting the current coherence state — not a corrective nudge to alter behavior. Upon sustained high γ, a corresponding high-coherence indicator state may be surfaced. For N > 2 participants, the indicator is derived from the median pairwise γ or a per-participant coherence-to-group score.
- FIG. 1Two-tile call view with lower-face primary ROI (106), chest fallback ROI (107), and per-participant respiration squiggles 108, 110.
- FIG. 2Two-panel coherence trace across a 0–600 s call session: upper panel shows caller-A respiration 202 (solid) and caller-B respiration 204 (dashed) — in-phase initially, drifting to anti-phase by ≈ 360 s; lower panel shows magnitude-squared coherence γ(t) 206 with high-coherence reference 208 (γ ≥ 0.8) and indicator-state threshold 210 (γ ≤ 0.4). Sustain window 212 (≥ 180 s of γ < 0.4) gates indicator state 214 (low-coherence). Legend 216 maps each glyph.
- FIG. 3Per-host pipeline blocks 302–308 with the off-host X marker establishing the privacy boundary.
- FIG. 4Symmetric peer-to-peer coherence: each host computes γ from its own and the peer's traces, exchanged via the existing conferencing transport. A per-host VAD module (406, 408) reading the conferencing audio gates γ computation to intervals of bilateral non-speech; no third-party aggregator.
- FIG. 5Outbound rPPG suppression: a shared webcam capture (502) feeds two pipelines — an unmodulated local pipeline (503) that computes γ on-host, and an outbound pipeline that applies sub-pixel modulation (504) prior to encoding so the transmitted stream (506) does not leak rPPG- or VM-recoverable physiology to peer side (508).
Part IV · Claims 10 total · 2 indep · 7 dep · 1 apparatus
1. A method for computing inter-participant respiratory coherence in an active video-conferencing session, comprising:
- (a)at each of a plurality of participant hosts, selecting a region of interest (304) in that host's outgoing webcam frames (302) comprising lower-face landmarks, optionally extended to chest landmarks when in frame;
- (b)recovering, by sub-pixel motion magnification (306) applied to said region of interest, a respiration signal (308) within an adaptive analysis band centered on said participant's detected respiration mode;
- (c)exchanging said respiration signal with at least one peer host over an existing conferencing data channel, without exchanging raw video or audio for said purpose;
- (d)computing, at each host, a pairwise magnitude-squared coherence γ of the local respiration signal and the received peer respiration signal over a sliding analysis window restricted to intervals of bilateral non-speech detected from the existing conferencing audio stream;
- (e)upon a sustained crossing of γ below a configured threshold, surfacing within the conferencing user interface an ambient indicator with a period or amplitude derived from a function of the participants' respiration signals over said analysis window, said indicator reflecting the current coherence state without prescribing a target respiration rate to any participant; and
- (f)wherein steps (a)–(e) are performed independently at each said participant host, no server or third-party aggregator computes or aggregates γ, and the only off-host transmission is, at step (c), of the per-host respiration signal between participating peers over the existing conferencing data channel.
2. The method of claim 1, wherein the sustained-crossing condition at step (e) is satisfied by either (i) a continuous interval of at least 180 seconds with γ below the configured threshold, or (ii) an integrated coherence deficit ∫(γthreshold − γ(t)) dt over γ < γthreshold exceeding a configured value over the analysis window.
3. The method of claim 1, further comprising surfacing a distinct high-coherence indicator state upon a sustained interval of γ above a high-coherence threshold, said high-coherence indicator state likewise reflecting current state and not prescribing a target respiration rate.
4. The method of claim 1, wherein the only physiological-signal input to the system is sub-pixel motion features of frames produced by the camera primarily used to encode the participant's outgoing video for the conferencing session.
5. The method of claim 1 extended to N > 2 participants, wherein for each pair (i, j) the system computes γi,j, and the surfaced indicator is derived from either (i) the median of γi,j over all pairs, or (ii) for each participant i, said participant's mean coherence to all other participants, surfaced as a per-participant coherence-to-group score.
6. The method of claim 1, wherein the ambient indicator surfaced at step (e) comprises one or more of: (i) a graphical element overlaid on or adjacent to one or more participant tiles, said graphical element animated with a period substantially equal to the median respiration rate of said one or more participants over the analysis window; (ii) a chromatic shift applied to a non-foreground region of the conferencing user interface, said shift varying monotonically with γ; or (iii) a subtle modulation of an audio cue distinct from the conferencing audio, said modulation reflecting current γ; and wherein no element of said ambient indicator includes a text prompt or other instruction directing any participant to alter their respiration rate.
7. The method of claim 1, wherein the coherence statistic γ computed at step (d) is replaced by, or supplemented with, a phase-locking value (PLV) computed over the same analysis window, said PLV being the magnitude of the mean of the unit complex vectors representing the instantaneous phase difference between the participants' respiration signals; and wherein step (e) is gated by the resulting statistic in the same manner.
8. The method of claim 1, further comprising obtaining, at session start and prior to step (a) at any participant host, an explicit per-participant opt-in to the recovery and inter-participant exchange of the said participant's respiration signal; and wherein non-opted-in participants are excluded from γ computation at all hosts, with the conferencing user interface reflecting their exclusion in the manner that an absent peer is reflected.
9. A method for suppressing physiological-signal leakage in outbound conferencing video, comprising:
- (a)capturing webcam frames (502) at a participant host;
- (b)computing, locally and from the unmodulated said frames, a per-participant physiological signal (503) comprising at least one of respiration and pulse;
- (c)applying, prior to outbound encoding of the conferencing video, a sub-pixel modulation (504) in the spatial and temporal bands recoverable by remote photoplethysmography (rPPG) and by sub-pixel motion magnification, said modulation configured to preserve perceptual quality of the encoded video;
- (d)transmitting the modulated outbound stream (506) over the existing conferencing transport; and
- (e)wherein the unmodulated local physiological signal of step (b) is reconstructable by the local host at full fidelity, while a peer running rPPG or motion magnification on the received stream (508) cannot reconstruct said physiological signal at signal-to-noise ratios comparable to said unmodulated source.
10. A host computing device comprising a webcam, one or more processors implementing ROI tracker 304, a voice-activity-detection module reading the conferencing audio stream, VM block 306, coherence computation, an optional rPPG / VM suppression module 504, and a non-transitory memory storing instructions to perform claims 1 – 9.
Part V · Appendices Prior-art bibliography
- Wu, H.-Y. et al. Eulerian Video Magnification for Revealing Subtle Changes in the World. SIGGRAPH 2012.
- Verkruysse, W. et al. Remote plethysmographic imaging using ambient light. Optics Express 2008.
- Poh, M.-Z. et al. Non-contact, automated cardiac pulse measurements using video imaging and blind source separation. Optics Express 2010.
- Tarvainen, M. P. et al. An advanced detrending method with application to HRV analysis. IEEE TBE 2002.
- Automatic Estimation of Interpersonal Engagement During Naturalistic Conversation Using Dyadic Physiological Measurements. Frontiers in Neuroscience, 2021.
- The role of reciprocity in dynamic interpersonal coordination of physiological rhythms. Cognition, 2022.
- The social, decoupled self: interpersonal synchronization of breathing alters intrapersonal cardiorespiratory coupling. bioRxiv, 2025.
- Preserving privacy and video quality through remote physiological signal removal. Nature Communications Engineering, 2025.
- Kim, J. H. RoomMirror. Provisional draft v0.10 (parent application).
Part VI · Execution Version · v1.0 · figures aligned
- v0.12026-03-08 · Skeleton draft. Descendant of RoomMirror.
- v0.22026-03-26 · Revised on dyadic-synchrony literature: nudge → ambient indicator; speech-gated coherence; adaptive respiration band; multi-participant generalization; integrated-deficit alternative to fixed sustain.
- v0.32026-04-13 · Added outbound rPPG-suppression sibling claim and FIG. 5; renumbered apparatus with VAD module and optional rPPG-suppression module; FIG. 1 ROI updated to lower-face primary, chest fallback (per v0.2 spec).
- v0.42026-05-01 · Added three dependent claims on Claim 1: concretized ambient indicator (Claim 6 · halo / chromatic shift / audio cue, with no-text-prompt limitation), phase-locking value (PLV) as alternative coherence statistic (Claim 7), and explicit per-participant opt-in consent (Claim 8). Renumbered: rPPG-suppression method → Claim 9; apparatus → Claim 10. Added threat-model paragraph to Background motivating outbound suppression.
- v1.02026-05-18 · Figures realigned with v0.4 claim set. FIG. 3: ROI block now "lower-face primary + chest fallback" and respiration block "adaptive band" (replacing the obsolete "0.1–0.5 Hz" and "chest + face" labels). FIG. 4: added per-host VAD module blocks (406, 408) with gating arrows into the γ box and an explicit "VAD-gated · bilateral non-speech only" label. Brief Description entries for FIG. 1 and FIG. 4 updated to match.
This descendant cites the RoomMirror parent specification (see /roommirror) for the underlying respiration-inference primitive and adds one narrow claim group (the pairwise-coherence UX trigger in a video-conferencing context).