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Documentation Index

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STUB DOCUMENT: This page is intentionally minimal and will be expanded with deeper technical details in a future update.
A two-camera privacy-preserving worker. YOLOv8 detects each person, the worker pixelates their bbox, and the driver substitutes the anonymised frame into the WebRTC stream before the bytes leave the edge.

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Why pixelate?

Pixelation reads as “a person, doing something” to a human reviewer — unlike stick figures which vanish on occlusion, low light or unusual poses. It also doesn’t need a pose model, cutting per-frame CPU cost by roughly 2× on edge devices. See the Privacy caveat below — pixelation is visual obscuring, not cryptographic de-identification.

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Pieces

LayerComponentNotes
Modelyolov8n (catalog)Plain detector; no pose head. Auto-downloaded on first cw.models.load().
Anonymisationcyberwave.vision.anonymize_frame()Pixelates each person’s bbox. Mode is configurable ("pixelate" / "redact" / "blur" / "bbox"). Skeleton overlay disabled.
Frame substitutionFrame substitutionDriver consults FILTERED_FRAME_CHANNEL (frames/filtered) before WebRTC encoding when CYBERWAVE_METADATA_FRAME_FILTER_ENABLED=true on the twin.
Routingtwin_uuid=ctx.twin_uuid on cw.data.publish()Same worker, two independent streams. See Multi-Camera Detection Routing.

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Worker

import os
import numpy as np
from cyberwave.data import FILTERED_FRAME_CHANNEL
from cyberwave.vision import anonymize_frame

CAMERA_1 = os.environ["CAMERA_1_TWIN"]
CAMERA_2 = os.environ["CAMERA_2_TWIN"]

model = cw.models.load("yolov8n")

def _anonymise(frame, ctx):
    result = model.predict(frame, classes=["person"], confidence=0.4)
    # Privacy fail-closed: ``anonymize_frame`` only obscures bbox
    # regions for matching detections. On a frame where the model
    # missed everyone (sub-threshold, occluded, partial body) it
    # would otherwise return the raw frame unchanged and the driver
    # would substitute that into WebRTC. Publish a black frame
    # instead — matches the driver's fail-closed behaviour for
    # stale and shape-mismatched filtered frames.
    if any(d.label == "person" for d in result.detections):
        out = anonymize_frame(
            frame,
            result.detections,
            mode="pixelate",
            draw_skeleton=False,
        )
    else:
        out = np.zeros_like(frame)
    cw.data.publish(FILTERED_FRAME_CHANNEL, out, twin_uuid=ctx.twin_uuid)
    for det in result.detections:
        if det.area_ratio > 0.3:
            cw.publish_event(ctx.twin_uuid, "person_too_close", {
                "area_ratio": round(det.area_ratio, 3),
                "frame_ts": ctx.timestamp,
            })

@cw.on_frame(CAMERA_1, sensor="default")
def on_camera_1_frame(frame, ctx): _anonymise(frame, ctx)

@cw.on_frame(CAMERA_2, sensor="default")
def on_camera_2_frame(frame, ctx): _anonymise(frame, ctx)
The same gate is applied automatically to workers generated from an anonymize workflow node, so workflows authored in the visual editor get the same privacy fail-closed behaviour without any code changes.

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Driver configuration

Enable the frame filter per camera twin (each generic-camera driver container): 
CYBERWAVE_METADATA_FRAME_FILTER_ENABLED=true
# Optional: widen the freshness window for CPU-only workers
# (default 200 ms is tuned for >= 5 Hz GPU workers).
CYBERWAVE_METADATA_FRAME_FILTER_FRESHNESS_MS=400
The channel name (frames/filtered) and fail-closed blank fallback are hard-coded in the driver. Freshness is tunable per driver via CYBERWAVE_METADATA_FRAME_FILTER_FRESHNESS_MS — raise it (e.g. 400–500) for CPU-bound workers, at the cost of keeping visibly-stale anonymised frames on screen longer. 0 is a valid “force blank” fail-close test mode. To see the raw camera feed for debugging, set CYBERWAVE_METADATA_FRAME_FILTER_ENABLED=false and restart the driver.
When CYBERWAVE_DETECTION_OVERLAYS is left at its default (true), bounding boxes and labels are drawn on top of the anonymised frame and reveal each person’s position — which defeats the anonymisation contract for location-sensitive deployments. Set CYBERWAVE_DETECTION_OVERLAYS=false alongside the filter flag if that matters.

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Privacy boundary

The Zenoh→MQTT bridge does not forward frames/* channels by default. Only events (person_too_close, …) and detections cross the WAN. The raw and anonymised frames stay on-device.
Pixelation is reversible by public depixelation models. It is deliberate visual obscuring, not GDPR-grade de-identification. For legal de-identification, combine pixelate with "redact" masking or drop frames entirely and publish only events.

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Per-zone alerting with Spatial Filter + Timed Condition

For deployments where the pixelation is just the privacy scaffold and the actual alert is “person loitering inside a restricted polygon”, combine this driver setup with a workflow that wires spatial_filter and timed_condition downstream of call_model + anonymize. The polygon also renders as a read-only overlay on the twin’s WebRTC stream so operators can see which zones are armed without opening every workflow. See the Zone-based intrusion detection tutorial for the full end-to-end recipe.

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Reference implementation