Problems with Overlay Snychronization

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jonny-h@gmx.com
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Problems with Overlay Snychronization

Post by jonny-h@gmx.com » Tue Apr 12, 2016 8:46 am

Hey Harry,

bought myself an XGPS150 and a Gopoint BT1 in Winter which I now used when driving over the Nordschleife.
I use Harry's Laptimer Grand Prix Edition, starting screen says version v19.0.31(64) on my iPhone 5s (Version 9.2.1)

When tapping onto Overlay I come into Overlay Konfiguration Menu. I can choose between "Vorlauf" and "Nachlauf" (standard: 0s, 0s). (sorry for German description).
But the only adjustment I can do is to choose for "Nachlauf" (should be delay in English) between 0s and 1s. Which is the first thing I'd imagine is not normal.

When using standard setting (0s, 0s) the OBD-Data in Overlay Video is about 1,5seconds ahead in comparison to reality (sound, video).

So I have two questions:
1. How can I fix this issue, how can I create the overlay video with correct OBD synchronization? Found in expert settings a menu point called Overlay synchronization "Video (0.0-9.0s) which is set to 1 (i didn't change that).
2. For my next laps using the Laptimer: Should I change (in expert settings under menu Sensor Delays) the delay of "any OBD (0.0-3.0) from 1 to 2,5?

Thank you in advance for your help and best regards,

Jonathan
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Harry
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Re: Problems with Overlay Snychronization

Post by Harry » Wed Apr 13, 2016 10:22 pm

Intro / Extro (Vorlauf / Nachlauf) are not related to video / data synchronization. This is about adding some footage ahead of the lap's start or behind the end of the lap. For Nordschleife BTF, with separate start and stop positions, videos will start around 1 second after the bridge (video has some latency during startup) and slightly after gantry. This is the reason you can't add intro and only a small amount of extro. To extend this range, start video recording manually in the pits and stop the cam back in the pits again. See "mixed mode" recording in Video Documentation (www.gps-laptimer.de/documentation).

In case video recorded and synced automatically show always some misalignment with data overlaid, change the Overlay Synchronization. In case the video behind data, increase the 1s setting and vice versa. Try 0.5s steps, small mis-adjustment are usually perceived bigger than they are.

- Harry
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Re: Problems with Overlay Snychronization

Post by jonny-h@gmx.com » Thu Apr 14, 2016 2:10 pm

Hey Harry,

thank you for your note. Don't needed any intro, only issue was bad synchro between video and OBD data (especially gear shifts, throttle etc).

Solutions was:
I changed (in expert settings under menu Sensor Delays) the delay of "any OBD (0.0-3.0)" from value "1" to "0".

Now it's nearly synchronized. (maybe a lag of 0.1/0.2 seconds which is no problem).

Best,

Jonathan
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Re: Problems with Overlay Snychronization

Post by RacerEric » Sun Oct 25, 2020 4:59 pm

Hi Harry,
This topic has been covered in a couple threads. I've been using LapTimer for years, but when I upgraded my phone from a Galaxy 6 to a 10, I now have the DATA being AHEAD of the video by a good 2 seconds. Im not using any external hardware. I believe you have mentioned INCREASING the overlay synchronization setting in this situation. However, when I do this the misalignment gets worse. Decreasing the setting to 0 helps, but still not perfect. Is it possible to go to a negative number like -0.5? Or is there another setting I should change like GPS delay?

Thanks,
Fred
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Re: Problems with Overlay Snychronization

Post by Harry » Mon Oct 26, 2020 12:24 pm

Data ahead video means video behind data. This means the video is coming later in as expected thus its delay is too small. So if the initial observation is correct, you need to increase Overlay Synchronization / Video. Please keep in mind that we typically overestimate the gap. So 2s is probably far too much and "overshoots". Try +0.5s instead and use Play to test. Increase step by step until it is o.k.

There is no negative delay - this wouldn't make sense because it means measurements are coming in before they actually happened. :-) But it is certainly possible that the GPS delay is wrong. Adding x to Overlay Synchronization / Video is like subtracting x from GPS, OBD, IMU. So in case you really find "-0.5s" to be correct, you'd need to add to the other sensor delays. But: this has no effect on existing recordings. So in case you need to repair existing recordings, you need to align video and data manually. This can be done from Video List / any video in the bottom of the screen where the sync points for referencing laps are listed. Tap this row to change the alignment by an arbitrary value.

- Harry
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