Control motorized camera docks and enable intelligent subject tracking using DockKit. Use when discovering DockKit-compatible accessories, implementing camera subject tracking for faces or bodies, controlling dock motors for pan and tilt, configuring framing behavior, setting regions of interest, or

DockKit Framework for integrating with motorized camera stands and gimbals that physically track subjects by rotating the iPhone. DockKit handles motor control, subject detection, and framing so camera apps get 360 degree pan and 90 degree tilt tracking with no additional code. Apps can override system tracking to supply custom observations, control motors directly, or adjust framing. iOS 17+, Swift 6.3. Contents [Setup]( setup) [Discovering Accessories]( discovering accessories) [System Tracking]( system tracking) [Custom Tracking]( custom tracking) [Framing and Region of Interest]( framing and region of interest) [Motor Control]( motor control) [Animations]( animations) [Tracking State and Subject Selection]( tracking state and subject selection) [Accessory Events]( accessory events) [Battery Monitoring]( battery monitoring) [Common Mistakes]( common mistakes) [Review Checklist]( review checklist) [References]( references) Setup Import DockKit: DockKit requires a physical DockKit compatible accessory and a real device. The Simulator cannot connect to dock hardware. DockKit itself requires no special entitlements or DockKit specific Info.plist keys. Camera apps that use device cameras still need normal camera privacy handling, including NSCameraUsageDescription . The framework communicates with paired accessories automatically through the DockKit system daemon. The app must use AVFoundation camera APIs. DockKit hooks into the camera pipeline to analyze frames for system tracking. Discovering Accessories Use DockAccessoryManager.shared to observe dock connections: accessoryStateChanges emits DockAccessory.StateChange values with state , accessory , and trackingButtonEnabled . Use accessory.identifier for the name, category, and UUID; hardware details are available via firmwareVersion and hardwareModel . System Tracking System tracking is DockKit's default mode. When enabled, the system analyzes camera frames through built in ML inference, detects faces and bodies, and drives the motors to keep subjects in frame. Any app using AVFoundation camera APIs benefits automatically. Enable or Disable System tracking state does not persist across app termination, reboots, or background/foreground transitions. Set it explicitly whenever the app needs a specific value. Tap to Select Subject Allow users to select a specific subject by tapping: Custom Tracking Disable system tracking and provide your own observations when using custom ML models or the Vision framework. Providing Observations Construct DockAccessory.Observation values from your inference output and pass them to the accessory at 10 30 fps: Observation Types When reviewing custom tracking, explicitly choose among the only supported ObservationType cases: .humanFace , .humanBody , and .object . Do not answer with only .humanFace when body or object detections are possible. The rect uses normalized coordinates with a lower left origin (same coordinate system as Vision framework no conversion needed). Camera Information DockAccessory.CameraInformation describes the active camera; do not hardcode placeholder device, intrinsics, or frame size values. Set orientation to .corrected when coordinates are already relative to the bottom left corner. In review answers, reject opaque optional cameraInfo placeholders and show construction from the active AVCaptureDevice plus the current CMSampleBuffer . Track variants also accept [AVMetadataObject] instead of observations. Use the image: CVPixelBuffer overloads when DockKit should combine observations or metadata with the captured image buffer; the image argument is required in those overloads. Framing and Region of Interest Framing Modes Control how the system frames tracked subjects: Mode Behavior .automatic Documented default; system decides optimal framing .center Explicit opt in mode to keep subject centered .left Frame subject in left third .right Frame subject in right third Default system behavior often centers the primary subject, but .center is never the default like mode; .automatic is. Use .left or .right when graphic overlays occupy part of the frame. Region of Interest Constrain tracking to a specific area of the video frame: Use region of interest when cropping to a non standard aspect ratio (e.g., square video for conferencing) so subjects stay within the visible area. Motor Control Disable system tracking before controlling motors directly. Angular Velocity Set continuous rotation speed in radians per second: Axes: x pitch (tilt). Positive tilts down on iOS. y yaw (pan). Positive pans right. z roll (if supported by hardware). Set Orientation Move to a specific position over a duration: Also accepts Rotation3D for quaternion based orientation. Set relative: true to move relative to the current position. The returned Progress object tracks completion. Motion State Monitor the accessory's current position and velocity: Setting Limits Restrict range of motion and maximum speed per axis: Animations Built in character animations that move the dock expressively: Animation Effect .yes Nodding motion .no Shaking motion .wakeup Startup style motion .kapow Dramatic pendulum swing Animations start from the accessory's current position and execute asynchronously. Always restore tracking state after completion. Keep animate(motion:) and setOrientation( :duration:relative:) calls to no more than twice per second; higher call rates can throw .frameRateTooHigh . Tracking State and Subject Selection iOS 18+ exposes ML derived tracking signals through the throwing trackingStates async sequence. Each state has time and trackedSubjects ( .person or .object ); persons include identifier , rect , speakingConfidence , lookingAtCameraConfidence , and saliencyRank (lower rank is more salient). Use selectSubjects( :) to lock tracking by UUID; pass [] to return to automatic selection. Use speakingConfidence for speakers, lookingAtCameraConfidence for engagement, rect for overlays, and lower saliencyRank values as fallback. In review answers, consume lookingAtCameraConfidence and rect in code, not just prose. Accessory Events Physical buttons on the dock trigger events through the throwing accessoryEvents async sequence (iOS 17.4+): Third party apps receive these events and implement behavior through AVFoundation. Battery Monitoring Monitor the dock's battery status through the throwing batteryStates async sequence (iOS 18+). A dock can report multiple batteries, each identified by name : Common Mistakes DON'T: Control motors without disabling system tracking DON'T: Assume tracking state persists across lifecycle events DON'T: Call track() outside the recommended rate DON'T: Spam orientation or animation calls DockKit can throw .frameRateTooHigh if animate(motion:) or setOrientation( :duration:relative:) is called more than twice per second. Set a trajectory, observe its Progress , and avoid tight command loops. DON'T: Forget to restore tracking after animations DON'T: Use DockKit in Simulator DockKit requires a physical DockKit compatible accessory. Guard initialization and provide fallback behavior when no accessory is available. Review Checklist [ ] import DockKit present where needed [ ] Subscribed to accessoryStateChanges to detect dock/undock events [ ] Handled both .docked and .undocked states [ ] System tracking disabled before custom tracking or motor control [ ] System tracking restored after animations complete [ ] Custom observations supplied at 10 30 fps [ ] animate and setOrientation commands limited to 2 calls per second [ ] Observation rect uses normalized coordinates (lower left origin) [ ] Camera information is built inline from the active AVCaptureDevice and current sample buffer [ ] Observation type choice names .humanFace , .humanBody , and .object [ ] @unknown default handled in all switch statements over DockKit enums [ ] Motion limits set if restricting accessory range of motion [ ] Tracking state re applied after app returns to foreground [ ] accessoryEvents guarded with available(iOS 17.4, ) [ ] trackingStates and batteryStates guarded with available(iOS 18.0, ) [ ] Battery UI preserves BatteryState.name for multi battery docks [ ] No DockKit code paths executed in Simulator builds References Extended patterns (Vision integration, service architecture, custom animations): [references/dockkit patterns.md](references/dockkit patterns.md) [DockKit framework](https://sosumi.ai/documentation/dockkit) [DockAccessoryManager](https://sosumi.ai/documentation/dockkit/dockaccessorymanager) [DockAccessory](https://sosumi.ai/documentation/dockkit/dockaccessory) [Controlling a DockKit accessory using your camera app](https://sosumi.ai/documentation/dockkit/controlling a dockkit accessory using your camera app) [Track custom objects in a frame](https://sosumi.ai/documentation/dockkit/track custom objects in a frame) [Modify rotation and positioning programmatically](https://sosumi.ai/documentation/dockkit/modify rotation and positioning behavior programmatically) [Integrate with motorized iPhone stands using DockKit WWDC23](https://sosumi.ai/videos/play/wwdc2023/10304/) [What's new in DockKit WWDC24](https://sosumi.ai/videos/play/wwdc2024/10164/)