[Bug]: macOS Presenter Overlay Small interrupts the independent camera recording without a warning #1378

Search existing issues

• I have searched the existing issues. Related camera-preview and long-recording reports do not describe this Presenter Overlay interaction.

Describe the bug

On macOS, enabling Presenter Overlay → Small while OpenScreen's own camera recording is enabled can leave the independent camera sidecar with a system screen/person placeholder and only the first moments of video. OpenScreen does not explain the conflict during capture.

In the affected take, camera access was granted and the camera indicator remained active, so this looked like a working recording. Export subsequently reported success but produced an unreadable, approximately 262-byte MP4 with no media tracks.

Related PR: #1377 rejects unreadable camera clips and empty exports. It does not fix Presenter Overlay compatibility, camera recovery, or capture-time conflict detection. Please treat this issue as separate recording-side follow-up; merging that PR should not automatically close this issue.

Expected behavior

If Presenter Overlay interrupts the independently recorded camera feed, OpenScreen should clearly explain the conflict and how to proceed. It should not silently save an unusable camera track or imply that a complete editable camera recording was captured. The exact compatibility/recovery policy is for maintainers to decide.

To Reproduce

Reported sequence from the affected recording:

1. Use the macOS arm64 release with screen recording and camera access granted.
2. Enable OpenScreen's built-in-camera recording.
3. Select a display through the macOS system screen-sharing UI.
4. Enable Presenter Overlay → Small, expecting this to show the face alongside the recording.
5. Record for approximately 36 seconds, stop, and open the project.
6. Preview/export with the linked camera track.

This is an observed affected take, not a claim that every attempt or every Mac reproduces it.

Actual results and diagnostic evidence

• The screen video contains about 35.43 seconds of video.
• The camera sidecar declares about 36.91 seconds, but contains only 51 decoded frames, ending at 1.670 seconds.
• At about 1.310 seconds, the camera image changes to the system screen/person placeholder.
• The saved camera offset is −1,693 ms, so the editor/export needs camera footage beyond the available frames at the screen clip's start.
• Local system diagnostics identify presenterOverlayMode: Optional(.small) for OpenScreen's display-sharing stream. The user subsequently confirmed selecting Small.
• The camera encoder session remained open until the take ended; a green camera indicator alone therefore did not establish that the independent recording remained usable.

OS

macOS

OS Version

15.7.1

Device Type

Laptop — MacBook Air M2, 16 GB RAM, built-in camera

Application version

OpenScreen 2.1.2, official Apple-silicon build. Browser: not applicable (desktop app).

Additional context

Apple documents that Presenter Overlay uses the camera in the shared-content stream and that AVCaptureSession no longer supplies its usual live camera stream while the effect is active:

• WWDC23: What's new in ScreenCaptureKit
• SCStreamDelegate.outputVideoEffectDidStart(for:)
• SCStreamDelegate.outputVideoEffectDidStop(for:)

Static inspection of the capture helper on the investigated main baseline (264975d8) found an SCStreamDelegate implementation without those Presenter Overlay start/stop callbacks. This is a possible integration point, not an implemented or tested fix.

Workaround: leave macOS Presenter Overlay off and use OpenScreen's camera overlay for an independently editable camera track; start a fresh take rather than relying on recovery of an already interrupted recording.

Control and limits: a subsequent clean GUI recording/export on the same installed v2.1.2, using the legacy-picker diagnostic launch, retained 1,463 camera frames and exported a valid 48.2-second, 1080p/30 MP4 (1,446 video frames, approximately 33.5 MB). Full-file decoding completed without errors. The control used a different picker/launch path; a clean same-path system-picker On/Off comparison, mid-take recovery, other OS versions, and any compatibility fix remain unverified. Earlier zoom-preview performance issues are outside this report.

No private recording, camera image, personal filesystem path, or raw system log is attached.