2. Integration Architecture - Understanding Plugins

What is a Plugin?

Every Plugin is a dynamic library (*.dll/*.so) which can be used to add new capabilities to Nx Meta.

A Plugin implements several abstract classes:

• Engine — a class representing a Video Analytics solution. Technically it is a factory of DeviceAgents; each Engine receives its own settings set by the user
• DeviceAgent — a special "worker" for a specific camera, for example, for processing its video stream

Each class declares a manifest — a JSON object declaring its capabilities and settings.

The Plugin Lifecycle

1. When Nx Meta Server starts, it loads all the Plugin libraries from Plugins directory
2. Inside each Plugin library, Nx Meta Server looks for "Engine factory"
3. Nx Meta Server creates an Engine object using the factory
4. Once an Engine is in the system, it becomes available to the user; they can enable it on specific cameras and configure it using the Desktop Client interface
5. Once an analytic Plugin is enabled on the camera, Nx Meta Server creates instances of DeviceAgents to do the work

For Video Analytics Plugins:

• Nx Meta Server sends a video frame-by-frame to a special method of a DeviceAgent.
• DeviceAgent does the internal work and sends metadata (detected objects and events) back to Nx Meta Server.
• Metadata goes to the object database and is used for search and visualization
• Events go to Event Rules Engine. The user can then configure specific actions for those events.
• If a DeviceAgent provides context actions for metadata objects, Nx Meta Server calls them when the user clicks a corresponding button in the context menu of an object in the Objects panel inside Nx Meta Desktop.

Integrating with a Remote Analytic Product

In cases where a video analytics product works as an independent application or service (not running on the same machine as the Plugin, e.g. cloud-based or “boxed” video analytics solutions),  Plugins should be implemented in a way that will connect to the remote solution and transfer data between Nx Meta Server and the remote video analytics software.