Use case

This issue will be the main issue that tracks various threading problems in iOS camera plugin.

Proposal

We wrote up a formal proposal to improve the thread model, with detailed execution plan in the end. There are also a couple non-threading issues that we'd like to address in the spirit of "yak shaving".

Action Items

We need to fix these threading related issues:

• Rename "dispatchQueue" to "sessionQueue"
• Dispatch engine API calls on iOS main queue
• Handle all SampleBuffer callbacks on the session queue
• Write photo file in IO queue
• Thread safety for state access
  • Fix _dispatchQueue race condition which is causing a known crash
  • Fix FLTSavePhotoDelegate's reference
  • Fix _camera ivar
  • Fix dispatch orientation change on the session queue (_deviceOrientation, _lockedCaptureOrientation, _isRecording)
• Pixel buffer with queues

These are optional cleanups not related to threading:

• Handle system pressure for video writes
• Remove selfReference [camera]remove "selfRef" for SavePhotoDelegate and ensure thread safety plugins#4780
• Break up CameraPlugin.m
• Clean up properties and ivars