detector_chat.py

import numpy as np

def pairwise_chat_flags(tracks, max_dist_px=80, min_stationary_s=10, fps=25.0):
    # tracks: dict id -> {'centroid':(x,y), 'history':[...]} ; returns set of ids chatting
    ids = list(tracks.keys())
    centroids = [tracks[i]['centroid'] for i in ids]
    chatting_ids = set()
    # Stationary check: movement in last ~min_stationary_s
    window = max(1, int(min_stationary_s * fps * 0.5))
    def is_stationary(hist):
        if len(hist) < window+1: return False
        pts = np.array(hist[-window:])
        d = np.linalg.norm(pts - pts.mean(axis=0), axis=1).mean()
        return d < 2.5  # pixels

    for i in range(len(ids)):
        for j in range(i+1, len(ids)):
            c1 = np.array(centroids[i]); c2 = np.array(centroids[j])
            dist = np.linalg.norm(c1 - c2)
            if dist <= max_dist_px and is_stationary(tracks[ids[i]]['history']) and is_stationary(tracks[ids[j]]['history']):
                chatting_ids.add(ids[i]); chatting_ids.add(ids[j])
    return chatting_ids