DockKit

DockKit lets your camera app drive motorized stands and gimbals that physically pan and tilt to keep subjects in frame across a 360-degree field of view. Automatic tracking works in any camera app with zero code; you integrate only when you want custom framing, direct motor control, your own tracking model, device animations, or the on-device tracking signals added in iOS 18.

Part of the axiom-media suite (skills/dockkit.md).

When to Use

Use this skill when you're:

• Building a camera, video-conferencing, live-streaming, fitness, or education app that should track subjects on a motorized stand
• Customizing how a subject is framed (alignment or a region of interest)
• Taking direct control of the motors for custom motion or animations
• Feeding your own Vision / Core ML inference to track non-default subjects (hands, animals, objects)
• Reacting to accessory buttons (shutter, flip, zoom) or gimbal controls
• Reading intelligent-tracking signals (saliency, speaking, looking-at-camera) to build custom tracking logic (iOS 18+)

Example Prompts

• "How do I track a subject with a DockKit motorized stand?"
• "How do I take direct control of a DockKit stand's motors?"
• "How do I feed my own Vision hand-tracking into DockKit?"
• "Why isn't my DockKit custom motor control doing anything?"
• "How do I read which person is speaking from DockKit tracking states?"
• "How do I handle DockKit gimbal buttons and battery level?"

Key Concepts

Observe dock state first

.docked and .undocked are inverted from intuition: .undocked means the phone IS in the stand and connected. Gate all control on .undocked from the accessoryStateChanges async sequence.

System tracking overrides you

System tracking is on by default. Disable it before any custom motor control or custom inference, or your commands are silently ignored:

try await DockAccessoryManager.shared.setSystemTrackingEnabled(false)

Direct motor control

setAngularVelocity(_:) takes a Spatial.Vector3D in radians/second for pitch (x), yaw (y), and roll (z):

import Spatial
// Pan right at 0.2 rad/s while tilting down at 0.1 rad/s
try await accessory.setAngularVelocity(Vector3D(x: -0.1, y: 0.2, z: 0))

Coordinate origins differ

Region of interest uses an upper-left (display) origin; DockAccessory.Observation rects use a lower-left (Vision) origin. Vision results pass straight through to track(_:cameraInformation:).

iOS 18 intelligent tracking

The trackingStates async sequence exposes per-subject saliency rank, speaking confidence, and looking-at-camera confidence so you can build features like "always track the active speaker" via selectSubjects(_:).

Common Mistakes

Mistake	Cost	Fix
Treating .docked as "ready"	Commands sent with no accessory	Gate on .undocked
Leaving system tracking on	Custom control silently overridden	setSystemTrackingEnabled(false) first
Missing camera permission	.cameraTCCMissing thrown	Request NSCameraUsageDescription first
Confusing coordinate origins	Tracking drifts or inverts	Region of interest = upper-left; observations = lower-left
Thread.sleep/GCD between commands	Blocks, fights the async API	Use Task.sleep; the APIs are async

Related

• camera-capture — The underlying AVCaptureSession DockKit tracks against
• now-playing — Other media-suite system integrations
• For custom Vision / Core ML inference feeding observations, see the axiom-vision suite

Resources

WWDC: 2023-10304, 2024-10164, 2023-111336

Docs: /dockkit, /dockkit/dockaccessory, /dockkit/dockaccessorymanager, /dockkit/dockaccessory/observation, /dockkit/dockkiterror