RTTrPM

showstack / protocols / rttrpm

Also called Real Time Tracking Protocol Motion, RTTrP Motion, BlackTrax protocol.

The packet format BlackTrax uses to stream tracked position and orientation to third party systems. It carries centroid and individual point positions, quaternion or Euler orientation, velocity, acceleration and zone collisions for lighting, video and audio consumers.

Tracking and positionOpenCAST GroupReported

Stewarded by CAST Group (BlackTrax).

Control Small, urgent, must arrive

Small messages that either repeat constantly or fire once. Bandwidth is almost never the problem.

What kills it. Latency and loss on the messages that fire once. A repeating level survives a dropped packet; a GO does not.

The four flows, and why the model is worth having →

What goes wrong

The RTTrP header carries both a big-endian signature (0x4154) and a little-endian one (0x5441). Read the signature first and byte-swap the rest of the packet accordingly, or every position you decode looks like noise.

A packet is a header plus a variable list of modules, each with its own type and size. Do not assume fixed offsets. Walk the module list by declared size or you will break on the next firmware release.

Centroid position and tracked point position are separate module types. A beacon taped to a performer's shoulder is not the centroid of the trackable, and consuming the wrong one puts the light in the wrong place.

RTTrPM (motion) and RTTrPL (lighting) share the same header. Motion is a fixed-rate stream, lighting is event-driven, so a receiver that assumes a steady packet rate will time out on the lighting side.

The wiki documents no default port and no default address. Whatever the BlackTrax output configuration says is the truth, so get it from the tracking operator rather than guessing.

What speaks RTTrPM (12)

Product	Direction	Notes
disguise Designer disguise	in	Used for BlackTrax tracking data.
Hippotizer Green Hippo (an ACT Entertainment brand)	in	BlackTrax is listed among MultiController automation readers; the manual names the product rather than the RTTrPM protocol version, so the exact wire format is not confirmed in vendor docs.
L-ISA Controller L-Acoustics	in	Performer position from tracking systems.
Notch Notch (10bit FX Limited)	in needs licence	BlackTrax is listed among supported tracking systems, but the docs name the product rather than the RTTrPM protocol version. Tracking support is an RFX-tier feature: Indie and VFX tiers have no tracking systems.
Stage Precision Stage Precision	bidirectional	RTTrPM in and out.
BlackTrax CAST Group	out	RTTrP is CAST's open real-time tracking protocol, with RTTrPM and RTTrPL variants for third-party systems.
d&b audiotechnik DS100 Signal Engine d&b audiotechnik	in	Positional data from BlackTrax and other RTTrPM sources, usually via a bridge.
disguise gx 3 disguise	in	BlackTrax position data.
Hippotizer Boreal+ MK2 Green Hippo	in	BlackTrax tracking input via RTTrPM.
Modulo Kinetic Modulo Pi	in	RTTrPM tracking input.
TTA StageTracker II TTA — Track The Artist	out	Position output.
zactrack PRO zactrack	out	RTTrPM output for audio object positions.

Open source implementations

RTTrP reference stub code (C++ and Python) — C++, MIT
RTTrPMtoOSC bridge — C++

Typical use

BlackTrax feeding media servers for projection onto moving objects
Driving moving lights and followspot systems from beacon positions
Positioning sources in object-based audio renderers
Triggering show events from zone collision detection

Sources

Real-Time Tracking Protocol — RTTrPM — CAST Group primary
Real-Time Tracking Protocol (RTTrP overview, RTTrPM vs RTTrPL) — CAST Group primary
BlackTrax developer resources (simulator, UDP player, sample code) — CAST Group primary

Understand the mechanism

How it all runs together Node graphs and game engines How a machine reads the world Being somewhere

Something wrong, or missing?

Known gaps on this entry: default_ports, first_published. If you can source one of them, that is a ten minute pull request.

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