PauseCam for iPad

Pause and resume video recording into a single continuous file — something the stock Camera app on iPad simply can't do.

Record a scene, pause, reframe, resume — as many times as you like — and get one .mov in your Photos library with every paused gap stitched out and audio in perfect sync. No timeline editing, no clip joining, no third-party editor.

Built with SwiftUI + AVFoundation for iOS/iPadOS 17+.

Features

• 🎬 Pause/resume recording into a single continuous clip — the core feature
• 🎞️ Scene counter ("Scene N") that increments on every resume
• ⏱️ Live timer showing recorded duration — freezes while paused, derived from actual sample timestamps
• 🔍 Native zoom: lens-switch pills (0.5x/1x/tele on multi-camera devices), smooth digital 2x on single-lens devices, pinch-to-zoom
• ☀️ Tap to focus/expose with a stock-camera-style EV slider (drag to adjust exposure bias)
• 🔄 Front/back camera flip (while idle)
• 🖼️ Last-clip thumbnail with in-app playback (session-only, like the stock Camera)
• 🎛️ Control Center launch button (iOS 18+) — replace the stock Camera control with PauseCam
• 🎤 Microphone optional: records video-only if mic access is denied
• 📱 iPhone + iPad, all orientations, saves to Photos with add-only permission

Why the obvious API can't do this

AVCaptureMovieFileOutput — the standard "record a movie" API — has no pause. The only way to get true in-camera pause into one file is to build the pipeline yourself:

AVCaptureVideoDataOutput + AVCaptureAudioDataOutput → your code → AVAssetWriter

The pause trick is timestamp surgery, in CameraController.swift:

1. Keep a cumulative timeOffset (CMTime).
2. While paused, drop every incoming sample buffer.
3. On resume, add the elapsed gap (currentPTS − lastAppendedPTS, less one frame duration) to timeOffset.
4. Subtract timeOffset from every subsequent sample's presentation/decode timestamps (CMSampleBufferCreateCopyWithNewTiming) before appending.
5. Use the same offset for video and audio so A/V never drift.

The writer session starts on the first video buffer (earlier audio is dropped), timestamps are guarded to stay monotonic on both tracks, and all writer bookkeeping runs on one serial queue — the delegate queue for both outputs — so the state machine is single-threaded by construction.

Architecture

File	Role
PauseCam/PauseCamApp.swift	@main SwiftUI app
PauseCam/CameraController.swift	The engine: capture session, asset-writer pipeline, pause/resume timestamp math, zoom, exposure, rotation
PauseCam/CameraPreview.swift	Preview layer host + tap-to-focus, EV drag, pinch-zoom gestures
PauseCam/ContentView.swift	Controls overlay, timer, permission/error UI, last-clip player
Shared/LaunchPauseCamIntent.swift	App intent compiled into both targets (see below)
PauseCamControls/	Control Center widget extension (iOS 18+)

Orientation uses AVCaptureDevice.RotationCoordinator (iOS 17+): the preview tracks the horizon continuously; the capture angle is fixed at record start for the whole clip.

The Control Center gotcha

A Control Center button that launches its app cannot host its AppIntent only in the widget extension: openAppWhenRun is rejected there (LNContextErrorDomain 2001), and a returned OpenURLIntent gets dropped because the extension sandbox can't read the LaunchServices database. The intent must be compiled into the app target too — then the system runs perform() in the app process and the launch works. That's why the intent lives in Shared/ with membership in both targets.

Requirements

• Xcode 16+
• iOS/iPadOS 17.0+ (Control Center button requires 18.0+)
• A physical device — camera capture does not work in the Simulator

Building

Open PauseCam.xcodeproj, select your development team under Signing & Capabilities (both targets), pick your device, and run.

Or from the command line:

xcodebuild -project PauseCam.xcodeproj -scheme PauseCam \
  -destination 'generic/platform=iOS' \
  DEVELOPMENT_TEAM=YOUR_TEAM_ID -allowProvisioningUpdates build

To use the Control Center button: launch the app once, then Control Center → + → Add a Control → PauseCam.

License

MIT