Argus::CameraProvider behaves like a singleton

Robotics & Edge Computing Jetson & Embedded Systems Jetson Orin Nano
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• Hardware Platform (Jetson / GPU): Jetson Orin Nano
• JetPack Version: JetPack5 (r35.5), JetPack 6.1 (r36.4.0)
• Issue Type( questions, new requirements, bugs): questions

nvargus entry point (Argus::CameraProvider) object to enumerate cameras seems to behave as a singleton, but this behavior does not appear to be documented.

Both in multi-process (with daemon) and single-process (without daemon) flavors of the library, an application cannot create more than one provider without encountering issues.

In particular:

Multi-process flavor

If using nvargus_socketclient library, creating a second provider results in the following errors:

(NvCameraUtils) Error InvalidState: Mutex already initialized (in Mutex.cpp, function initialize(), line 41)
(Argus) Error InvalidState:  (propagating from src/rpc/socket/client/ClientSocketManager.cpp, function open(), line 54)
(Argus) Error InvalidState:  (propagating from src/rpc/socket/client/SocketClientDispatch.cpp, function openSocketConnection(), line 263)
(Argus) Error InvalidState: Cannot create camera provider (in src/rpc/socket/client/SocketClientDispatch.cpp, function createCameraProvider(), line 107)

Single-process flavor

If using nvargus library, creating a second provider succeeds, but destroying it causes the underlying instance of any other provider to be destroyed as well, resulting in dangling pointers and segmentation fault.

As a consequence the Argus::CameraProvider must be used as a singleton.

This gist illustrates minimal repro case with build instructions.

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What’s the reason for creating seconder CameraProvider?

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Our application ended up in this state because it had two different components in charge of opening camera streams vs. just enumerating camera properties like serial numbers.

I can also see this happening if e.g. we had two cameras and manage them in such a way two completely independent instances of our classes open each camera.

Anyway, this can easily worked around by wrapping the CameraProvider in a singleton, however I think this should be enforced at Argus API level, rather than discovered by developers with a segfault?

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You should use multiple session or multiple source in single session for opening multiple cameras.

Thanks

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