Discover() and Open()

Programming Questions C++ API
1

Hi,

I am writing an application (Cvb++, Qt, GenICam) and I would like to present a list of cameras to the user so that the user can chose one of the detected cameras and use it.
Obtaining a list of cameras via Cvb::DeviceFactory::Discover() works nicely; however, I did not find a way to Cvb::DeviceFactory::Open() a specific camera detected.

Is there a way to obtain the Vin driver path (optional, I could of course provide this) and open one of the detected camaras (e.g. via serial number, Id, …)?
Alternatively, is there a way to list the cameras on a vin driver and select one of them?

I would like to avoid having to use an external tool to select the camera to be used.

2

Hi,

you can open a discovered device info by calling:

auto device = Cvb::DeviceFactory::Open(info.AccessToken());

This opens a device (GenICam.vin) directly via the access token. No preconfiguration via the GenICam.ini is necessary.

1 Like
3

I was wondering why DO_DISCOVER_INFO_ACCESS_TOKEN was missing from DiscoveryProperties, but of course that´s the reason - it´s in a separate function.

Thanks!

4

Yes,

we put it in a function as this property is always available and needed most :slight_smile:.

1 Like
5

One more question in this context: how do I close a device?

Discover() works nicely as long as the camera has not been Open()ed, but Discover() obviously cannot access open devices.

P.S.: pDevice.reset() seems to work, but is this safe?

6

Hi @Jakob,

yes that is safe. It is the intended way (or let the std::shared_ptr run out of scope).

But keep in mind that you have shared ownership with the returned device (std::shared_ptr<Cvb::Device>). That means if you have stored the device std::shared_ptr in multiple places (e.g. objects), the Device is unloaded when the last std::shared_ptr is .reset or runs out of scope.

7

Regarding inaccessible devices (e.g. opened): if the transport technology supports it, .Discover() filters these out. You can still show them by providing the DiscoverFlags::IncludeInaccessible to the .Discover() call. But you still won’t be able to open the device in a different process.

Also note that if you simply call .Discover(), it is the same as calling .Discover(DiscoverFlags::IgnoreVins | DiscoverFlags::IgnoreGevSD). This is the same as the default Management Console/GenICam Browser output.

8

Hi,

Ok, that´s fine then - I can keep track of the number of references to the pointer, I was just afraid there might be copies stored somewhere in the Cvb++ part.

Thanks for the answer!

9

We only keep weak references (std::weak_ptr). Opening the same device returns the same Device object.