Mavlink / TFLite / Camera server timestamps

[Plingaas02]

Hi ModalAI team,

We are working on high-speed mapping. We are currently looking at matching timestamps, but there seems to be a lot of different implementations in the source code. Can you confirm which clock these timestamps are in, and if any of them are synced?

voxl-camera-server, timestamp for image capture at exposure start, or at image published to pipe?
voxl-tflite-server, we use the image metadata to overwrite the ai_detection_t timestamp.
voxl-mavlink-server, we need to match odometry to image exposure time, this is our biggest confusion atm.

And in general, which function should we be using to get the current time on the voxl?
apps_time_monotonic_ns()?

Best regards,
Peter

[Eric Katzfey]

@Plingaas02 Regarding odometry in voxl-mavlink-server, it will not modify timestamps on this message. There will be, potentially, VIO odometry messages going to the flight controller from voxl-vision-hub via voxl-mavlink-server and flight controller odometry messages being routed out to the GCS and to the onboard stream. The odometry messages coming from PX4 will have the DSP monotonic timestamp which is different than the Linux monotonic clock and these will drift with respect to each other over time. PX4 runs the timesync service so it can correct the incoming messages from VIO.