The BlackTrax Implementation of RTTrPM and RTTrPL


Applications like the BlackTrax real-time tracking system use RTTrPL and RTTrPM to interface with other lighting and third party applications (such as media servers, robotic cameras, and spatial audio systems) to provide tracking for automated lights, and projection mapping. With BlackTrax, RTTrPM is sent at a fixed rate of 100Hz.

BlackTrax - RTTrPM

The BlackTrax tracking system generates RTTrPM to output to third-party listeners, such as media servers. BlackTrax outputs tracking information for individual Beacons' tracked points using Tracked Point modules. Each BlackTrax Beacon can have up to three individual LEDs/tracked points. Alternatively, the system can also output Centroid modules, which calculate the center position of a tracked object (Trackable) based on the centroid of each individual LED attached to a Beacon. Some other general points regarding the BlackTrax implementation of RTTrPM:

  • BlackTrax sends out RTTrPM packets at a rate of 100Hz

  • BlackTrax by default sends out a heartbeat, or empty RTTrP header with an RTTrPM signature if no Beacon or LED data is available in the current frame

  • BlackTrax has the ability to add and remove different modules at any given time

  • In the BlackTrax implementation of the Trackable module with Timestamp, the Timestamp value is equal to the frame ID of the cameras in the BlackTrax system, as determined by the TimeKeeper

  • Euler Orientation modules always send with an order of 0x0123 (X1, Y1, Z1)

  • The Tracked Point modules correspond to the LEDs on a BlackTrax Beacon (trackable), the Index is either 0x01, 0x02 or 0x03

  • The context field in the RTTrP header is always set to the value of the current BlackTrax chapter (0x00000001, etc.), regardless if the current Trackable is present in the chapter, or if no Trackables are present in the RTTrPM packet (i.e. just the heartbeat is being sent). When in standby the Context field is set to 0xFFFFFFFF.

  • The Zone Collision Detection module should only send Zone Sub-Modules that the Trackable is actively colliding (inside) with. If a Zone Sub-Module is not sent, it is assumed the collision is not happening and the Trackable is outside of the Zone.

BlackTrax - RTTrPL

The BlackTrax tracking system uses RTTrPL in a specific manner, the following are some points related specifically to the BlackTrax tracking system and its implementation and use of RTTrPL:

  • BlackTrax's default UDP lighting packet output address: (Multicast)

  • BlackTrax's default UDP lighting packet synchronization address: (Multicast)

  • BlackTrax keeps a buffer of channels (of all universes) that it is controlling, the lighting node (Peer) should keep the same buffer as well

  • BlackTrax may release all channels and may also release only specific channels when running, it utilizes the Xfade field in a Channel Block module to define when to take control and release a channel

  • If the hold time is set to 0x00, the Peer should never release control automatically as BlackTrax may hold a channel for a long time

To get a Snapshot earlier, the Peer may send out a Lighting Sync packet and BlackTrax will react with a Snapshot, this is used to help sync the two buffers together. This feature is not currently implemented and so the Lighting Sync Module is an optional module. The module structure is as follows:

Packet Modules - BlackTrax Specific

Lighting Sync 0x08

Packet Module - Lighting Sync Module

Field Name Type Size (bytes) Description
0 Type UInt8 1 Value = 0x07
1 Size UInt16 2 Size of packet module including type and size
2 Device ID UInt32 4 User defined (Cast assigned)
3 Device Sub ID 0 UInt32 4 User Defined
4 Device Sub ID 1 UInt32 4 User Defined
5 Sequence Number UInt32 4 Last mismatch sequence. 0 if unknown

Tools and Testing Applications

Some tools have been provided by the BlackTrax tracking system to be used for integration with other systems.

  • Simulator: The Simulator is a testing application which will simulate positional and rotational data of a Beacon sent from the BlackTrax tracking system. Download the ZIP package and double-click on the setup.exe. The Setup Instruction PDF file will help you configure all the communication settings.

  • Rigid Body Files: This is a seperate package for Third Parties that are interested in using BlackTrax's Rigid Bodies. You can download this ZIP package which contains recordings and sample files for use with a BlackTrax tracking system.

    • Please Note: You need either a BlackTrax server or a BTX dongle in order to run the included files. Please get in contact with BlackTrax support ( if you require a dongle.

  • Some recorded RTTrPL data from the BlackTrax tracking system has been provided, along with tools to output this data, in order to test implementations of RTTrPL

  • The use of the UDP Player is required to play back the provided RTTrPL recordings

    • Documentation on the use of the UDP Player to play back BlackTrax RTTrPL recordings can be found in the UDP Player package