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time4tea / gopro-dashboard-overlay

Programs to process GoPro MP4 & Generic GPX/FIT files and create video dashboards & maps
GNU General Public License v3.0
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Discrepancy between video and GPS data #147

Open Trigve opened 1 year ago

Trigve commented 1 year ago

Hi, I've found your wonderful project and started to test it (using docker). But I think I found a bug.

I've got a GoPro 9 timewarp x10 video. I want to add some overlays to it. The problem is that the longer/bigger the video is the more discrepancy there is between the video and the overlays (speed, map position, ...). For instance if the video is 40 seconds long everything looks ok. But if the video is for instance 3 minutes long, the overlays doesn't match the original video (for instance, overlay is saying that the speed is 16 KPH, but the "video" isn't moving for another 2 seconds). I could send you the testing video if needed.

time4tea commented 1 year ago

Hi. Thanks for your interest in the project.

Yes, please can you send me the file.

Please could you send a link to gopro-overlay@time4tea.net wetransfer can be good for this.

I'll just use the file for diagnostic purposes, and it will stored on encrypted drives, and removed when I solve the issue.

Thanks!

James

Trigve commented 1 year ago

So I've tried to prepare video for you, but unfortunately I've accidentally deleted the (testing) video that was causing problem. With the another one, everything is OK. So I would try the other ones I have and will report back if there is same problem.

time4tea commented 1 year ago

No worries. Well I guess it is good that it is working some of the time at least. :-)

To be honest the timewarp code is not much used by me, so I can imagine there are edge cases that don't work 100%

In particular, I think switching timewarp settings while a video is recording will not work properly.

If you have a video that shows a problem please do let me know!

Cheers

James

bphilli7 commented 2 months ago

I can provide potentially relevant sample data if you are interested in looking into this.

I have a timewarp video taken from a GoPro Hero 10. I used timewarp for the duration of a 3 hour filming session which results in a ~20 min file, four parts of ~5 min each. The video is quite lengthy, and there are moments where the GPS data is clearly unsynchronized from the images in the frame.

If timewarp is supported by gopro-dashboard-overlay, then my video files have broken GPS timestamps leading to de-synchronization issue similarly noted by original poster. I have never used the feature to enter "Real Speed" mode during the timewarp video, so the issues may be unrelateable.

https://community.gopro.com/s/article/what-is-timewarp-video?language=en_US

One key aspect of my video is that my timewarp videos use "Auto" timescaling, allowing the firmware of the GoPro to dynamically adjust the timescaling based on the motion of the camera (see section on Capture rate info). Perhaps this breaks the GPS time synchronization of gopro-dashboard-overlay? Maybe timewarp is only supportable for fixed multiple of capture rate (2x, 10x, etc)? Just my guesses.