Human motion tracking systems typically follow a top-down pipeline (detect → crop → estimate). In practice, especially in lab setups or tools like #freemocap and #pose2sim, this means a person detector runs independently, and the pose model operates on fixed-resolution crops.
There is a licensing problem here. Since YOLOv5, Ultralytics models use AGPL-3.0. If you build proprietary commercial software (e.g., motion tracking SaaS), you must either open-source your system or purchase an enterprise license. For that reason, many open-source pipelines (#rtmlib, #sports2d, #pose2sim) still rely on YOLOX (2021), the last Apache-2.0 YOLO variant.
After ~1.5 years of using YOLOX in motion tracking setups, I’ve found it poorly suited for high-quality lab tracking. It is highly sensitive to object orientation and produces significant frame-to-frame box jitter, even for nearly static subjects. That instability propagates to pose outputs. You can smooth it offline or add causal filters online, but then you introduce lag. For real-time use cases (e.g., VR animation), that trade-off is undesirable.
A better alternative is now available: RF-DETR (ICLR 2026, Apache-2.0) by Roboflow. In my side-by-side comparisons against YOLOX, it is noticeably more stable in low-motion scenes, with far less bounding box wobble. It also avoids NMS, eliminating manual tuning and associated false positives. While YOLOX can be faster, detector stability often matters more for downstream pose quality than raw FPS.
To make adoption easier, I built #OpenDetect: a minimal wrapper around RF-DETR (and YOLOX) using ONNX Runtime, with CUDA, TensorRT, and Apple acceleration supported out of the box. While I focus on person class for pose estimation, detection for all COCO classes is supported. Apache-2.0 license, free for commerical use. No obligation to make your code public.
🚀 GitHub: https://lnkd.in/dFwwg4e5
🤓 Docs: https://lnkd.in/d67qCQKj
If your subject is mostly static and your keypoints still jitter, improve the detector first. A stable detector can clean up your entire pose pipeline without modifying the pose model.
#computervision #poseestimation #opensource