Add Pan/Tilt (PTZ) support for Arlo pan-tilt cameras

[dw5304]

Summary

Adds PanTiltZoom support to ArloCamera for Arlo's pan/tilt models (e.g. VMC2083A – Essential Indoor 2nd-gen Pan & Tilt). Previously the plugin exposed no movement controls for these cameras.

The Scrypted PanTiltZoom interface is added capability-gated (only cameras whose Arlo capabilities advertise PanTiltZoom.pan), so no other models are affected.

How Arlo PTZ actually works (the non-obvious part)

Arlo pan/tilt is velocity-based continuous motion, not absolute positioning. I captured the official web client (my.arlo.com) driving the camera and found it sends, on the device notify channel:

// while the joystick is held:
{ "from": "<userId>_web", "to": "<deviceId>", "action": "continuousMove",
  "resource": "cameras/<deviceId>/ptz", "publishResponse": true,
  "properties": { "panTiltSpaces": { "velocityGenericSpace": { "x": <pan -1..1>, "y": <tilt -1..1> } } } }

// on release:
{ "from": "<userId>_web", "to": "<deviceId>", "action": "stop",
  "resource": "cameras/<deviceId>/ptz", "publishResponse": true }

Key findings:

• The action is continuousMove (move until stop), not set. An action:"set" with positionGenericSpace is accepted by the cloud (success:true) but the camera never moves.
• Properties use velocityGenericSpace (x=pan velocity, y=tilt velocity, each −1..1), not positionGenericSpace.
• The web app happens to send this over the SIP-WebSocket instantMessage proxy during a live stream, but the existing HTTP /notify channel works identically — no in-band/SIP changes needed. The camera reports live position back on cameras/<id>/ptz (action:"is") as it moves.
• Read-only capability/preset metadata is available at cameras/<id>/ptz (position, homePosition, defaultPTZSpeed, presets[]).

Changes

• arlo/arlo_async.py: PTZContinuous(basestation, camera, x, y) (continuousMove) and PTZStop(basestation, camera) (stop).
• camera.py:
  • ArloCamera now mixes in PanTiltZoom.
  • has_ptz property gated on Capabilities.PanTiltZoom.pan.
  • arlo_presets helper (exposes Arlo presets as Scrypted PTZ presets metadata).
  • get_applicable_interfaces advertises PanTiltZoom when has_ptz.
  • ptzCapabilities is published in delayed_init (needs to run after the device is registered — setting it during get_applicable_interfaces is too early and the state write is lost).
  • ptzCommand maps Scrypted PTZ → Arlo: nonzero pan/tilt velocity → continuousMove; zero → stop. This lines up exactly with ONVIF/clients that drive PTZ via ContinuousMove + Stop.

Testing

• VMC2083A, firmware er1.4, interfaceVersion i007.
• Verified the camera physically pans/tilts full range and reports matching live positions back over the event stream.
• Verified end-to-end via UniFi Protect (adopted as an ONVIF camera through a rebroadcast/ONVIF bridge): joystick press → continuousMove, release → stop.

Notes / follow-ups

• Presets and absolute moves aren't wired into ptzCommand yet (clients using ONVIF ContinuousMove/Stop — incl. UniFi — only need continuous + stop, which this covers). Preset metadata is exposed via ptzCapabilities.presets; honoring a goto-preset command could be a follow-up (Arlo has a presetToken-based move).
• Latency is inherent (cloud round-trip); the velocity+stop model handles it gracefully.

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