Rundown Server

Controlling the Motion Design playout can be accomplished by combining two APIs. The Rundown Server API is used to load the rundown assets and the page’s templates, and contains an embedded Remote Control Preset (RCP).

The RCP for the corresponding page can be accessed and modified via the Remote Control API, then saved back in the rundown page for immediate or later playout.

Architecture Overview

Project Configuration

1. Set Up WebSocket Messaging Plugin in Server Mode

The Rundown Server API is exposed to WebSocket through the WebSocket Messaging bridge plugin. This plugin allows any internal message bus end points to be exposed through a WebSocket.

It can be enabled in the plugin browser by searching for web socket:

Once enabled, the plugin can be configured in Project Settings > Json.

Enter the desired listen port and configure the serialization to JSON.

2. Enable Rundown Server

In the Editor settings:

Enable the auto start for the Rundown server on the next editor restart. Leaving the server name blank will use the computer’s name instead.

Alternatively, there is a console command to start the rundown server immediately: "MotionDesignRundownServer.Start [ServerName]". The server name is an optional argument.

Finally, the UE process can be launched with a command line argument: -MotionDesignRundownServerStart[=ServerName].

If the server is running, the console command MotionDesignRundownServer.Status should provide some information about the status of the server.

3. Set Up Remote Control

Follow the instructions on the Remote Control API WebSocket Reference page.

If using the http server, it is binding to localhost by default, which may not be the adapter you need. To let it bind to any adapter, add the following lines to DefaultEngine.ini:

[HTTPServer.Listeners]

DefaultBindAddress=any

Using WebSocket Messaging

The WebSocket Messaging plugin exposes all messages going through the UE message bus. Each internal message-bus message is wrapped in a .json message with additional routing information.

Anatomy of the a WebSocket Messaging bridge message:

Example of a request GetRundowns and the response from the server:

{
  "Sender": "F2DCD99C267C4F84B50CF091AA4ED608",
  "Recipients": [
    "139696A842C8861F52E756BB60AA8661"
  ],
  "MessageType": "/Script/AvalancheMediaEditor.AvaRundownGetRundowns",
  "Expiration": 253402300799,
  "Scope": "Network",
  "Annotations": {},
  "Message": {}
}
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{
  "Sender": "139696A842C8861F52E756BB60AA8661",
  "Recipients": [
    "F2DCD99C267C4F84B50CF091AA4ED608"
  ],
  "MessageType": "/Script/AvalancheMediaEditor.AvaRundown**Rundowns**",
  "Expiration": 253402300799,
  "TimeSent": 1660878367,
  "Scope": "Network",
  "Annotations": {},
  "Message": {
 **   "rundowns": [
      "/Game/AvaRundown.AvaRundown",
      "/Game/AvalancheExamples/ExampleRundown.ExampleRundown",
      "/Game/AvalancheExamples/DemoRC.DemoRC"
    ]
**  }
}
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The message type specifies the content of Message. In API terms, for the client, the message type is the command and the content of Message is the arguments of the command.

Message Bus Handshake with Rundown Server

In order to get the UUID of the Rundown server on the message bus, which is then used as Recipient for the messages, a WebSocket client must broadcast a ping message to the WebSocket and listen for the pong reply to get the UUID of the server. In the message bus, the Rundown server is subscribed to the AvaRundownPing message and will reply to its sender with a AvaRundownPong message.

{
  "Sender": "F2DCD99C267C4F84B50CF091AA4ED608",
  "Recipients": [],
  "MessageType": "/Script/AvalancheMediaEditor.AvaRundownPing",
  "Expiration": 253402300799,
  "Scope": "Network",
  "Annotations": {},
  "Message":
    {
        "bAuto": false 
    }
}
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{
        "Sender": "**69C67BCB4B61795764D1E596D9F01214**",
        "Recipients": [ "F2DCD99C267C4F84B50CF091AA4ED608 ],
        "MessageType": "/Script/AvalancheMediaEditor.AvaRundownPong",
        "Expiration": 253402300799,
        "TimeSent": 1661023146,
        "Scope": "Network",
        "Annotations": { },
        "Message":
        {
                "bAuto": false,
                "hostName": "TEST-SERVER-01"
        }
}
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The Pong message Sender field is the UUID of the Rundown server’s endpoint in the message bus system. This is then used as the Recipients field for all other messages from the Websocket client.

Rundown Server API

Existing commands and response messages can be found in the source code here:

Engine\Plugins\Experimental\Avalanche\Source\AvalancheMediaEditor\Private\Rundown\AvaRundownMessages.h
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The path of the USTRUCT is the MessageType field of the WebSocket message, while the content is serialized in the Message field as previously shown.

Editing the Page RCP with Remote Control API

The GetPageDetails is used with bLoadRemoteControlPreset set to true to inject the page’s RC values into the managed RCP for that asset. The server response will include the following fields:

'remoteControlPresetName': '/Temp/Managed/ESPYS/Blueprint/Avalanche/9021',

'remoteControlPresetId': '984A4E0146010512D839538C0AF265FA',

These can be used with Remote Control API as the PresetName field.

The RC values are saved back in the page with the UpdatePageFromRCP request.