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GPS-video-OBD sync

Hello
I've tested last weekend RaceChrono with a good external GPS (my phone gps is useless). I have used a TomTom Bandit camera for recording the video and a cheap OBD reader for car data.
I have synced the video with the GPS data without a problem, BUT the OBD is about 3 to 5 second earlier then GPS/video.
Is there any way to move it?
Thanks

Comments

  • aolaol
    edited May 2018
    Hi, device independent time shift filter is on my TO-DO list, but currently there's no way to do it. Normally GPS/OBD-II sync should be within 300-400 ms, so for most people it doesn't matter. Which GPS did you use, 3-5 seconds sounds like a lot, maybe some issue with the Bluetooth stream maybe?
  • I've just checked and the OBD data is about 6 second earlier than GPS
    The GPS is a custom module based on ublox VK2828U7G5LF chip with a serial to Bluetooth converter, but also with another external gps (I don't remember the brand, it was borrowed) I got the same 6 second delay.
    Using the internal GPS the sync is very good
  • Sounds weird that both GPS have such long delay. RaceChrono joins the feeds from the two sources based on the reception time, so clearly the GPS feed is received with 3-5 second delay you mention. Usually the delay on GPS is maximum one second. There's some delay on OBD-II too, but usually only 200-300ms at max.
  • I've checked an old session (made with the free app) with internal gps and the data are perfectly synced, so maybe there is some problem with the bluetooth communication between my phone (Huawei P9) and the external GPS.
    Thanks for the support!!!
  • Update to this...
    I was editing a video made the other day, when I've found some weird things.
    In all the tracks I have been in with RaceChorno the start/finish line in the maps is in the right point, but the lap timer start/end is around 6 seconds later.
    Maybe this is the root cause of the problem?
  • aolaol
    edited April 9
    I remain with my original analysis, that your GPS has a delay problem. Probably caused by combination of slow Bluetooth transmission and large transfer buffer. It could easily cause all the symptoms you describe.
  • I think I've found my problem, done a quick test on my way to work today.
    The probelm is/was the GPS/bluethooth adapter speed, I don't know why it was set to 9600bps, changed to 115200 and now I have a pretty good sync.
    I was sure to have changed it at the beginnig, and never checked.

    THANKS for the tips
  • Makes sense.
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