MessageQueue was closed error.

AkshayKumar

Hi All,

I am currently using an OAK-4S camera. Occasionally, after connecting to the camera and building the pipeline, I encounter a "MessageQueue was closed" error when attempting to read frames. This issue does not occur consistently but happens intermittently.

I have attached a images containing the pipeline setup code and the frame-processing thread for reference.

Could you please help identify the possible root cause of this issue and suggest a solution?

Logs:
2026-03-17 15:50:55.093 | INFO | camera | Device already connected for Camera_5

2026-03-17 15:50:55.093 | INFO | camera | Pipeline already running for Camera_5

2026-03-17 15:50:55.093 | ERROR | depthai | MJPEG loop error for Camera_5: MessageQueue was closed

Thank you.

Oskar-Luxonis

Hey AkshayKumar - hm hard to say just from this. This error usually means the output queue was closed because the pipeline or device state changed, not just that no frame was available. In your case the most likely cause is a race between the frame-reading thread and pipeline restart/rebuild, so the thread sometimes calls tryGet() on an old queue after the pipeline has already been stopped or replaced. A transient disconnect/reconnect can produce the same symptom as well.

I would make sure the frame thread is stopped and joined before rebuilding the pipeline, and recreate the queue every time the pipeline is recreated. If the issue still happens, please enable DEPTHAI_LEVEL=debug and XLINK_LEVEL=debug and check for reconnect/disconnect logs.

Thanks,
Oskar