Application nodes

Nodes are models, code, camera streams, output, and parameters. A node has an interface, which defines its inputs and outputs. The interface can be defined in a package in your account, a package provided by AWS Panorama, or a built-in type.

In the following example, code_node and model_node refer to the sample code and model packages included with the sample application. camera_node uses a package provided by AWS Panorama to create a placeholder for a camera stream that you specify during deployment.

Example graph.json – Nodes

        "nodes": [
            {
                "name": "code_node",
                "interface": "123456789012::SAMPLE_CODE.interface"
            },
            {
                "name": "model_node",
                "interface": "123456789012::SQUEEZENET_PYTORCH_V1.interface"
            },
            {
                "name": "camera_node",
                "interface": "panorama::abstract_rtsp_media_source.rtsp_v1_interface",
                "overridable": true,
                "overrideMandatory": true,
                "decorator": {
                    "title": "IP camera",
                    "description": "Choose a camera stream."
                }
            }
      ]

Edges

Edges map the output from one node to the input of another. In the following example, the first edge maps the output from a camera stream node to the input of an application code node. The names video_in and video_out are defined in the node packages' interfaces.

Example graph.json – edges

        "edges": [
            {
                "producer": "camera_node.video_out",
                "consumer": "code_node.video_in"
            },
            {
                "producer": "code_node.video_out",
                "consumer": "output_node.video_in"
            },

In your application code, you use the inputs and outputs attributes to get images from the input stream, and send images to the output stream.

Example application.py – Video input and output

    def process_streams(self):
        """Processes one frame of video from one or more video streams."""
        frame_start = time.time()
        self.frame_num += 1
        logger.debug(self.frame_num)
        # Loop through attached video streams
        streams = self.inputs.video_in.get()
        for stream in streams:
            self.process_media(stream)
        ...
        self.outputs.video_out.put(streams)

Abstract nodes

In an application manifest, an abstract node refers to a package defined by AWS Panorama, which you can use as a placeholder in your application manifest. AWS Panorama provides two types of abstract node.

• Camera stream – Choose the camera stream that the application uses during deployment.

  Package name – panorama::abstract_rtsp_media_source

  Interface name – rtsp_v1_interface

• HDMI output – Indicates that the application outputs video.

  Package name – panorama::hdmi_data_sink

  Interface name – hdmi0

The following example shows a basic set of packages, nodes, and edges for an application that processes camera streams and outputs video to a display. The camera node, which uses the interface from the abstract_rtsp_media_source package in AWS Panorama, can accept multiple camera streams as input. The output node, which references hdmi_data_sink, gives application code access to a video buffer that is output from the appliance's HDMI port.

Example graph.json – Abstract nodes

{
    "nodeGraph": {
        "envelopeVersion": "2021-01-01",
        "packages": [
            {
                "name": "123456789012::SAMPLE_CODE",
                "version": "1.0"
            },
            {
                "name": "123456789012::SQUEEZENET_PYTORCH_V1",
                "version": "1.0"
            },
            {
                "name": "panorama::abstract_rtsp_media_source",
                "version": "1.0"
            },
            {
                "name": "panorama::hdmi_data_sink",
                "version": "1.0"
            }
        ],
        "nodes": [
            {
                "name": "camera_node",
                "interface": "panorama::abstract_rtsp_media_source.rtsp_v1_interface",
                "overridable": true,
                "decorator": {
                    "title": "IP camera",
                    "description": "Choose a camera stream."
                }
            },
            {
                "name": "output_node",
                "interface": "panorama::hdmi_data_sink.hdmi0"
            }
        ],
        "edges": [
            {
                "producer": "camera_node.video_out",
                "consumer": "code_node.video_in"
            },
            {
                "producer": "code_node.video_out",
                "consumer": "output_node.video_in"
            }
        ]
    }
}