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DJI Streamer

Application based on the DJI Mobile SDK for streaming synchronized video data and flight data using websockets to a custom-made server. It provides basic control functionality, such as in the DJI Go 4 / DJI Fly apps. The app should be compatible with most of the DJI drones (tested on Mavic Mini 1, Mavic Pro, Mavic 2 Dual Enterprise).

How to connect to a server and receive the data

  • Implement a WebSocket server, here is our Unity example.
  • In the drone GUI, click the Server IP button and fill in the IP address of the server and port (make sure that the port is open).
  • The drone, as a WebSocket client, tries to establish the connection.
  • If successful, the drone sends a handshake message, with the information about the drone type (ctype 0 means the client is a drone): 
    {
   "type":"hello",
   "data":{
      "ctype":0,
      "drone_name":"MavicPro",
      "serial":"12345"
   }
}
  • The server needs to implement a handshake reply. The drone expects a reply message in the following format (client_id is handled by the server, can be any identification string, for instance, an ID of the websocket client): 
    {
   "type":"hello_resp",
   "data":{
      "client_id":"41f28cb6",
   }
}
  • When successfully exchanged handshake messages, the drone is ready to start sending its data. To start, press the Live button.
  • The drone starts sending its data in binary format, encoded as: 
    | First 4 bytes == JSON bytes length | JSON bytes | 4 bytes + JSON bytes length + 4 bytes == JPEG image bytes length | JPEG bytes |
|------------------------------------|------------|------------------------------------------------------------------|------------|
    Binary data is split into a JSON message containing the flight data and JPEG bytes containing the current frame of the drone video feed. The first 4 bytes tell you the length of the JSON message, and the 4 bytes starting from (4 + length of JSON message) tell you the length of the JPEG image.
  • When decoding the JSON bytes to a string using UTF-8, the following structure of the flight data should be received (filled with example data): 
    {
   "type":"data_broadcast",
   "data":{
      "client_id":"41f28cb6",
      "altitude":234.6,
      "relative_altitude":10,
      "gps":{
         "latitude":49.24031521243185,
         "longitude":16.613207555321484
      },
      "aircraft_orientation":{
         "pitch":-4.0,
         "roll":-1.2,
         "yaw":81.2,
         "compass":81.2
      },
      "aircraft_velocity":{
         "velocity_x":0.1,
         "velocity_y":1.0,
         "velocity_z":0.1
      },
      "gimbal_orientation":{
         "pitch":0.0,
         "roll":0.0,
         "yaw":81.1,
         "yaw_relative":0.0
      },
      "satellite_count":16,
      "gps_signal_level":3,
      "battery":60,
      "sticks":{
        "left_stick": {
          "x":0
          "y":0
        }
        "right_stick": {
          "x":0
          "y":0
        }
      }
      "timestamp":"2025-06-27 14:45:06.843"
   }
}
    Where:
    • altitude is AMSL (height above mean sea level), to work, the takeoff altitude needs to be manually set using the button Altitude.
    • relative_altitude stands for AGL (above ground level) altitude.
    • sticks report the current configuration of the physical remote controller. Values are in the range of [-660, 660]. Zero means the sticks are centered, in the default position.
  • JPEG byte array can be directly decoded and displayed in the remote GUI.

How to control the drone using virtual sticks

  • To create some level of autonomy, virtual sticks functionality can be used. To enable virtual stick mode, send from the server following message: 
    {
   "type":"enable_control",
   "data":{
      "enable":true,
   }
}
  • The drone starts listening for command messages with the velocities of individual drone axes, in the following format: 
    {
   "type":"control_command",
   "data":{
      "pitch":0,  
      "roll":0,
      "yaw":0,
      "throttle":0,
      "gimbal_pitch":0
   }
}
    Where:
    • pitch (forward / backward), roll (left / right), throttle (up / down) are velocities in m/s. For slow speed, use values around 0.1.
    • yaw is velocity in deg/s. For slow speed, use values around 10.
    • gimbal_pitch is velocity in deg/s for tilting the gimbal up/down. For slow speed, use values around 10.