Starts providering the devices. This will cause #GST_MESSAGE_DEVICE_ADDED
and #GST_MESSAGE_DEVICE_REMOVED messages to be posted on the provider's bus
when devices are added or removed from the system.
Since the #GstDeviceProvider is a singleton,
gst_device_provider_start() may already have been called by another
user of the object, gst_device_provider_stop() needs to be called the same
number of times.
Starts providering the devices. This will cause #GST_MESSAGE_DEVICE_ADDED and #GST_MESSAGE_DEVICE_REMOVED messages to be posted on the provider's bus when devices are added or removed from the system.
Since the #GstDeviceProvider is a singleton, gst_device_provider_start() may already have been called by another user of the object, gst_device_provider_stop() needs to be called the same number of times.