dual_cameras_recorder

Website · GitHub · by Roman Slack

Record the front and back cameras simultaneously into a single composited .mp4 (and photo), with a live composited preview. Android + iOS.

The OS APIs can do this, but no Flutter plugin records the composited result — they stop at preview or unmerged photos. dual_cameras_recorder owns a unified manual GPU compositor (OpenGL ES on Android, Metal on iOS) so one composite per frame feeds the encoder and the preview, producing a clean PiP/split clip that drops straight into your existing media pipeline.

Hardware-gated. Simultaneous front+back requires concurrent-camera support: ~A12+/iOS 13+ on iOS, and a subset of Android devices (Pixel 6+, Galaxy S22+, …) capped at 720p per camera. Always check isSupported() and provide a single-camera fallback.

Install

dependencies:
  dual_cameras_recorder: ^0.1.0

Add permissions in the consuming app:

• iOS Info.plist: NSCameraUsageDescription, NSMicrophoneUsageDescription
• Android AndroidManifest.xml: CAMERA, RECORD_AUDIO (minSdkVersion 24)

Request them at runtime (e.g. with permission_handler) before initialize.

Usage

import 'package:dual_cameras_recorder/dual_cameras_recorder.dart';

final cam = DualCameraController();

if (!await DualCameraController.isSupported()) {
  // fall back to single-camera capture
}

await cam.initialize(
  layout: DualLayout.pictureInPicture(
    primary: CameraLens.back,
    insetCorner: Corner.bottomRight,
    insetScale: 0.28,
    cornerRadius: 18,
    margin: 12,
  ),
  resolution: DualResolution.hd720, // capped by hardware
);

// Live composited preview:
DualCameraPreview(cam);

await cam.startRecording();
cam.swapPrimary();                            // flip the full-frame camera, live
final String clip  = await cam.stopRecording(); // single composited mp4
final String photo = await cam.takePhoto();      // single composited still
await cam.dispose();

Layouts

DualLayout.pictureInPicture(...), DualLayout.splitVertical(...), DualLayout.splitHorizontal(...). The geometry is computed once and applied identically to preview, recording, and photo so they never drift. Pass an updated layout to cam.setLayout(...) live.

Performance HUD

DualCameraStatsOverlay(cam) renders a debug overlay (FPS, composite ms, dropped frames, thermal state) sourced from native telemetry — useful for validating the lag-free targets on real hardware.

How it works

dual_cameras_recorder is a federated plugin. The Android side feeds two concurrent SurfaceTextures into a single-GL-thread compositor → MediaCodec/MediaMuxer; iOS uses AVCaptureMultiCamSession → a Metal compositor → AVAssetWriter. Audio and video share one monotonic clock so they stay in sync. See ARCHITECTURE.md in the repository for the full engine design and performance discipline.

License

MIT © RomanSlack