Asynchronous Camera Event Handling

The GVCP asynchronous message channel is available only to applications using the primary control channel. Support for it is automatically enabled when a camera is opened with access mode GevExclusiveMode or GevControlMode.

The supported EVENT_CMD and EVENTDATA_CMD events are found in the device’s XML file. Signaling of these events needs to be enabled via calls to GevWriteReg using the proper address and enable values.

GigE-V Framework API allows an application to register two actions for an event. On receipt of an event, an application may have a callback function invoked and/or an event object can be signaled. In this case the application event is signaled before the callback function is invoked. A single call to GevUnregisterEvent will cause both the application event and the callback function to be unregistered.

Note that the callback is performed synchronously with the delivery of the event message from the camera. Care should be taken to complete the callback processing quickly so that subsequent messages are not lost. If lengthy processing is required, the callback is responsible for saving the contents of the EVENT_MSG data structure and the “data” buffer and signaling some other asynchronous processing context (thread) to perform that processing. Once the callback function returns, the contents of the EVENT_MSG structure (msg) and the ‘data’ buffer are no longer valid and will be overwritten by the asynchronous message.

The following functions provide this service.