dual_cameras_recorder #

[Dual Cameras — record the front and back cameras simultaneously in Flutter, composited into one portrait video]

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