OBD2 data out of sync with video

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svtdoug
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OBD2 data out of sync with video

Post by svtdoug »

I just added the recommended OBDLink MX Bluetooth OBD II unit for last track event. It worked, although there seems to be a timing issue on the video. The video (and sound) lag the OBD II rpm and throttle position by about 2 seconds. Is there a fix for that, or an adjustment?

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Harry
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Re: OBD2 data out of sync with video

Post by Harry »

Have you tested this using a manual recording, or a triggered one (i.e. on track)?

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svtdoug
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Re: OBD2 data out of sync with video

Post by svtdoug »

On track.
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Re: OBD2 data out of sync with video

Post by Harry »

In case the gap is around 0.5s, you can adjust it using the Overlay Synchronization / Video delay in LapTimer's Expert Settings. Please nite that humans tend to judge the gap a lot bigger than it actually is and verify this option first. There are plenty of threads on this topic on the forum already.

In case the gap is bigger, this is not a standard situation and the standard delay above should not be used. Instead, adjust the sync point manually: Lap List ‣ your lap ‣ Video / Preview ‣ select lap in the bottom (showing the offset in seconds) ‣ adjust sync point.

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svtdoug
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Re: OBD2 data out of sync with video

Post by svtdoug »

Harry,'

Thanks for the info above. I was able to adjust the Overlay synch setting and got it closer. One thing I noticed is that no one single setting it going to achieve good synch with the OBD to video data. One setting works well for most of a lap, but the next session it will be off by .5 sec or so. So I assume that the OBD data is drifting in timing. No sure why this is. It could the BlueTooth signal fluctuating in timing? Could it be the Android device? Or is it the Lap timer app? My guess is it not the app. Any thoughts on the reason?

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Harry
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Re: OBD2 data out of sync with video

Post by Harry »

The only sensor source coming in with a "true timestamp" is GPS. OBD does not have information when the data has been measured, neither has video. So for both you can get runtime effects shifting data a bit forward or backward. The fast a smartphone is, the less effects you will get.

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Re: OBD2 data out of sync with video

Post by n664dc »

For what it's worth, I also have this exact problem with the OBDLink LX and RaceChrono Pro on a Google Pixel. Great sync at the start of the video, then 20 minutes later it's off by a half a second or so. It steadily looses sync throughout the video. I think the only way to properly solve this is to support multiple sync points throughout the video. I was considering trying out Harry's lap timer as a solution to this problem, but looks like it's not solved there either.
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Re: OBD2 data out of sync with video

Post by Harry »

To be clear: in case such a drift occurs for a comparable short time, this is an issue with the hardware / the operating system. Multiple sync points are no option from my point of view. This is by far too complicated to address a small number of flawed device configurations. But there is a workaround for this: simply swap out the video to your desktop and let a capable video editor increase or slow down the video. Finally, transfer the video back for overlay. One possible option: https://trac.ffmpeg.org/wiki/How%20to%2 ... 0a%20video

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damntall
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Re: OBD2 data out of sync with video

Post by damntall »

Why don't you put in a button to reset sync points to the way they were captured? I changed mine by accident (video on phone, overlays from OBDLink MX) and this whole huge process to frame by frame it by eyeball is stupid.

The system knows how it captured it. Why not put a "use original sync point" button in that does... Exactly that?
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