Perception
Camera stream under 6 Hz
A camera stream from simulation fell from 15 Hz to under 6 Hz, but only in some sessions.
- camera
- DDS QoS
- WebRTC
- operator
6→15 Hz
camera stream restored
- ROS 2
- DDS QoS
- WebRTC
- NVIDIA Isaac Sim
Problem
The camera topic published at 15 Hz, yet the operator's WebRTC stream intermittently fell under 6 Hz and frames visibly dropped. The lag came and went between test sessions, so it could not be reproduced on demand.
Investigation
Ruled out causes one at a time: system load first (several cobot emulators and Isaac Sim instances shared one machine), then network stability (smooth in some sessions, laggy in others). Comparing the affected ZED camera stream with an unaffected RealSense stream on the same rig isolated the difference to the topic's DDS QoS profile: the ZED stream used Best Effort reliability, which silently drops samples whenever the system is under load.
Root cause
The camera topic used Best Effort QoS, which drops samples whenever the system is under load.
Fix
Switched the camera topic's QoS reliability policy to Reliable.
Outcome
The stream held a steady 15 Hz under the same load that used to break it.
- → Under 6 Hz → steady 15 Hz under identical load
- → Intermittent bug isolated by A/B comparison against a second camera stream