Skip to content

fix(sensing-server): person count hysteresis to stop flickering #295

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ruvnet merged 1 commit into from
Mar 24, 2026
+66 −24
Merged

fix(sensing-server): person count hysteresis to stop flickering #295

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
90 changes: 66 additions & 24 deletions rust-port/wifi-densepose-rs/crates/wifi-densepose-sensing-server/src/main.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -304,6 +304,8 @@ struct AppStateInner {
model_loaded: bool,
/// Smoothed person count (EMA) for hysteresis — prevents frame-to-frame jumping.
smoothed_person_score: f64,
/// Previous person count for hysteresis (asymmetric up/down thresholds).
prev_person_count: usize,
// ── Motion smoothing & adaptive baseline (ADR-047 tuning) ────────────
/// EMA-smoothed motion score (alpha ~0.15 for ~10 FPS → ~1s time constant).
smoothed_motion: f64,
Expand Down Expand Up @@ -1247,12 +1249,15 @@ async fn windows_wifi_task(state: SharedState, tick_ms: u64) {

let feat_variance = features.variance;

// Multi-person estimation with temporal smoothing (EMA α=0.15).
// Multi-person estimation with temporal smoothing (EMA α=0.10).
let raw_score = compute_person_score(&features);
s.smoothed_person_score = s.smoothed_person_score * 0.85 + raw_score * 0.15;
s.smoothed_person_score = s.smoothed_person_score * 0.90 + raw_score * 0.10;
let est_persons = if classification.presence {
score_to_person_count(s.smoothed_person_score)
let count = score_to_person_count(s.smoothed_person_score, s.prev_person_count);
s.prev_person_count = count;
count
} else {
s.prev_person_count = 0;
0
};

Expand Down Expand Up @@ -1377,12 +1382,15 @@ async fn windows_wifi_fallback_tick(state: &SharedState, seq: u32) {

let feat_variance = features.variance;

// Multi-person estimation with temporal smoothing.
// Multi-person estimation with temporal smoothing (EMA α=0.10).
let raw_score = compute_person_score(&features);
s.smoothed_person_score = s.smoothed_person_score * 0.85 + raw_score * 0.15;
s.smoothed_person_score = s.smoothed_person_score * 0.90 + raw_score * 0.10;
let est_persons = if classification.presence {
score_to_person_count(s.smoothed_person_score)
let count = score_to_person_count(s.smoothed_person_score, s.prev_person_count);
s.prev_person_count = count;
count
} else {
s.prev_person_count = 0;
0
};

Expand Down Expand Up @@ -1724,18 +1732,45 @@ fn compute_person_score(feat: &FeatureInfo) -> f64 {

/// Convert smoothed person score to discrete count with hysteresis.
///
/// Uses asymmetric thresholds: higher threshold to add a person, lower to remove.
/// This prevents flickering at the boundary.
fn score_to_person_count(smoothed_score: f64) -> usize {
// Thresholds chosen conservatively for single-ESP32 link:
// score > 0.50 → 2 persons (needs sustained high variance + change points)
// score > 0.80 → 3 persons (very high activity, rare with single link)
if smoothed_score > 0.80 {
3
} else if smoothed_score > 0.50 {
2
} else {
1
/// Uses asymmetric thresholds: higher threshold to *add* a person, lower to
/// *drop* one. This prevents flickering when the score hovers near a boundary
/// (the #1 user-reported issue — see #237, #249, #280, #292).
fn score_to_person_count(smoothed_score: f64, prev_count: usize) -> usize {
// Up-thresholds (must exceed to increase count):
// 1→2: 0.65 (raised from 0.50 — multipath in small rooms hit 0.50 easily)
// 2→3: 0.85 (raised from 0.80 — 3 persons needs strong sustained signal)
// Down-thresholds (must drop below to decrease count):
// 2→1: 0.45 (hysteresis gap of 0.20)
// 3→2: 0.70 (hysteresis gap of 0.15)
match prev_count {
0 | 1 => {
if smoothed_score > 0.85 {
3
} else if smoothed_score > 0.65 {
2
} else {
1
}
}
2 => {
if smoothed_score > 0.85 {
3
} else if smoothed_score < 0.45 {
1
} else {
2 // hold — within hysteresis band
}
}
_ => {
// prev_count >= 3
if smoothed_score < 0.45 {
1
} else if smoothed_score < 0.70 {
2
} else {
3 // hold
}
}
}
}

Expand Down Expand Up @@ -2824,12 +2859,15 @@ async fn udp_receiver_task(state: SharedState, udp_port: u16) {
let vitals = smooth_vitals(&mut s, &raw_vitals);
s.latest_vitals = vitals.clone();

// Multi-person estimation with temporal smoothing.
// Multi-person estimation with temporal smoothing (EMA α=0.10).
let raw_score = compute_person_score(&features);
s.smoothed_person_score = s.smoothed_person_score * 0.85 + raw_score * 0.15;
s.smoothed_person_score = s.smoothed_person_score * 0.90 + raw_score * 0.10;
let est_persons = if classification.presence {
score_to_person_count(s.smoothed_person_score)
let count = score_to_person_count(s.smoothed_person_score, s.prev_person_count);
s.prev_person_count = count;
count
} else {
s.prev_person_count = 0;
0
};

Expand Down Expand Up @@ -2929,12 +2967,15 @@ async fn simulated_data_task(state: SharedState, tick_ms: u64) {
let frame_amplitudes = frame.amplitudes.clone();
let frame_n_sub = frame.n_subcarriers;

// Multi-person estimation with temporal smoothing.
// Multi-person estimation with temporal smoothing (EMA α=0.10).
let raw_score = compute_person_score(&features);
s.smoothed_person_score = s.smoothed_person_score * 0.85 + raw_score * 0.15;
s.smoothed_person_score = s.smoothed_person_score * 0.90 + raw_score * 0.10;
let est_persons = if classification.presence {
score_to_person_count(s.smoothed_person_score)
let count = score_to_person_count(s.smoothed_person_score, s.prev_person_count);
s.prev_person_count = count;
count
} else {
s.prev_person_count = 0;
0
};

Expand Down Expand Up @@ -3577,6 +3618,7 @@ async fn main() {
active_sona_profile: None,
model_loaded,
smoothed_person_score: 0.0,
prev_person_count: 0,
smoothed_motion: 0.0,
current_motion_level: "absent".to_string(),
debounce_counter: 0,
Expand Down