04-25-2019 06:31 AM
I am currently working with the official github repo (https://github.com/gopro/gpmf-parser) of gopro which allows to extract GPS data from the MP4 Gopro video stream. I am using a gopro fusion.
I want to create an XML file (GPX like) which would bind each frame with a GPS location (I know some frame will get the same GPS coordinate). I want the highest possible quality of synchronisation.
With this repo I can get each GPS coordinates with the right timestamp. But as far as I know I cannot get an absolute timestamp of the frames.
I would need to know how to know the delay between the first frame and the first GPS location?
With ffmpeg I get to know the creation time of the video (which seems to have 2 minutes of delays comparing to the GPS timestamp). This 2 minutes delays let me think there is no real syncronisation betwwen the camera clock and the GPS.
Unless, the go pro fusion wait for the next gps location to start the recording? If the go pro wait for it we know that the first GPS location correspond to the first frame of the video.
Is my understanding correct, otherwise can you enlighten me ? ;)
05-04-2019 07:50 AM
You can start the video recording at any time and the camera doesn't have the feature to only automatically start recording when GPS is available.
To record GPS data, your GoPro needs to lock onto a GPS satellite signal. Once GPS is enabled, you will see the GPS icon turns solid black on the camera display, confirming that GPS has been found and locked.