7788feea5d
Apple recommends starting/setting up a session (AVCaptureSession) on a special queue and in the past we did this on the writer's queue. Unfortunately, we also can access the same session from a different thread and this results in race conditions and different weird crashes, for example, we're calling start/stopRunning from the writer's queue, while the session is being configured (in between beginConfiguration/commitConfiguration on the recorder control's thread). So we have to limit access to the session by the control's thread. Apple docs say we have to ensure all appendSampleBuffer calls done _before_ finishWriting. We ensure this by dispatching_sync an empty block on the writer's queue after store-release of m_state. We also do the same with video queue to ensure it does not try to access viewfinder's data after stop/abort executed. All these changes also make lock/mutex unneeded. Task-number: QTBUG-54890 Change-Id: I38e86c879b6b62306bdfbeade65405d6ac3be9f3 Reviewed-by: Yoann Lopes <yoann.lopes@qt.io>