The Blue screen overlay is created on the phone when you export,
The software will create a PNG image for the dial overlays for each frame of the video and its default at 25 frames per second,
Once it has done the export to blue screen you would need to download a program called virtualdub, you will then need to set the frame rate in virtualdub to 25FPS in the settings menu then import video by using the 1st exported PNG image, this will then produce an .avi file which is already synced to the video (which is also at 25 frames per second)
You then need some software where you can overlay a blue screen (Chroma key) video over the top of the other video (such as adobe there are others) Then all you have to do is set both of the video streams to start at the same time and then create a new video from that.
And you’re done
Alternately if you have Racerender, RaceChrono or Vbox software you can export the data to a format that it understands (you can choose the type) and it will overlay data on the video that way.
The Software will do OBD2 link as well so as long as you have an OBD2 Bluetooth sender, it will measure and record RPM, TPS, MAF, Intake Press and Engine Load in addition to GPS etc to which can be exported to the above alternative overlay softwares (Racerender, RaceChrono or Vbox)
Too right about the others being like school kids, never doing a session like that ever again.
Looking forward to a proper track day on the 13th where there will be sensible people
I am afraid you need a bit of a meaty PC when your doing this stuff, even more so as its 720p still if your patient then you get good results