The Pull Point subscription is using a secure pulling mechanism with HTTPS connection to handle simple events from ONVIF cameras via PullMessages requests. To determine the behavior of the Pull Point subscription mechanism, configurations are provided as described below.

The Pull Point subscription is automatically activated if there are ONVIF Pull Point Subscription Factory configurations set. The ONVIF Driver will create a subscription for each configuration match. Thus a device can have multiple subscriptions, each with a different filter and different settings for the pulling mechanism.

ONVIF Pull Point Subscription Factory Configuration

The ONVIF Pull Point Factory configuration is presented below:

Most configuration properties are not required, except the label property. If it is null, the configuration will be ignored by the PullPointSubscription service and no subscription will be created.

The label property is not unique. For example, if two or more configurations have the same label, an operation like SetSynchronizationPoint can be executed to all of the subscriptions with this label.

The SetSynchronizationPoint operation can be used only programmatically via ONVIF PullPointSubscriptionService interface, since it is not available via operation within the functional item. For more information on how to use it, refer to the developer guide.

The pullMessagesLimit property affects the behavior of the Pulling mechanism. A very small value may reduce the performance, due to the increased number of requests sent to the device to read all of the messages, depending on the supported events topics.

For the supported Topics needed for the filters, the GetEventProperties operation of the Events Service functional item could be used.

The Factory configuration is not dynamic. If changed during runtime, it will not affect the subscriptions. The configurations are read when the device changes its offline/online state, on initial registration or when the bundle starts.

ONVIF Events Device Access Configuration

The ONVIF Events Device Access Configuration is presented below:

Alias Prefix

The alias is introduced to specify a unique UID to the registered functional item. This alias is user-defined.

Validation

It is mandatory to include a unique prefix (alias) to the Detector Topic declaration. The following conditions shall be met:

• The alias must be unique
• The alias must start with character '<'
• The alias must end with character '>'
• Empty aliases are not allowed
• The topic is mandatory

If the conditions are not met, the detector will not be registered.

Convention for default topics

It is not necessary for the user to follow the default convention. The user can define its own convention. The following convention is used only for the default topic aliases:

• The alias declaration shall answer to "Detect what"
• Optional prefix to the alias should be used to provide the context

Event Service Functional Item

The following functional item is used to provide support for the GetEventProperties operation and NOTIFICATION property changed events.

Operation GetEventProperties

The GetEventProperties command is used to fetch the supported event parameters from the ONVIF Device:

• Topic Set
• Message Descriptions
• Supported Filter Dialects

  

The Topic Set could be used, for example, to:

• add the desired supported topics in the ONVIF Events Device Access configuration, for which will be registered DetectorFI
• filter the subscription in the ONVIF PullPoint Subscription Factory configuration

Notification property

The functional item has property NOTIFICATION which represents the Notification events. This property is updated only for notifications for which there is no registered DetectorFI and for the Complex Type events.

Complex Type Events

Complex Type events are supported on the Driver layer. For their Device Access and Functional Item representation, support can be provided upon request.

For each complex type notification message the Data ElementItems are provided in XML raw data format.

Detector Functional Item

The detector functional item is registered only for topics specified within the ONVIF Events Device Access configuration and for which the following conditions are met:

• it is supported by the device
• has only one Item inside the Data Element
• the item is of Simple Type
• the type is boolean

  

The detector functional item has the onvif.notification.topic attribute, which represents the Notification Topic:

Monitoring Topics

Since the Monitoring topics could not be returned by the GetEventProperties, they can be used statically from the ONVIF Core Specification. All of the Monitoring Topics, which have a Boolean type of event value are eligible for registering a detector functional item if they are specified within the ONVIF Events Device Access Configuration.

For more information about the Type and the structure of the Monitoring events, refer to the ONVIF Core Specification.

The configuration is not dynamic. If the configuration is changed and new topics are added/removed, the functional items will not be unregistered and registered again. To receive the new data from the ONVIF Events Device Access Configuration the device has to be removed/invalidated and then registered again or the device has to change its online state.

To learn more about creating/registering configurations refer to Initial Configuration Loader.