Harry's GPS Suite Forum

Hi,

A question about video syncronization. I hope I'm not the 327th person asking over the same issue. In that case...just shoot me down

I was able to succesfully synchronize a video (shot with a GoPro Session) with my log on an iPhone 5S. It was quite easy since the phone was covered by the camera sight, so I could fix it perfectly after a couple of tests.

Problem is: both g-meter and map looked hugely lagging. So I made a second test moving the ending point by 1.15 seconds: g-meter and map were now quite in line with the video, just a small lag, but of course the timing was now completely in off-set with the video.

Here is the result of the two experiments: https://www.youtube.com/watch?v=uuYz_e6hXGI

Is there a way to "shift" g-meter data and map data forward vs the timing data when overlaying?

Thanks in advance for your support

Hi,

timing and position data are always in sync - the former is derived from the later. Video and data can be off due to unexpected video startup times and other runtime influences on processing. To calibrate the standard relation for your specific smartphone and cam, please adjust the Overlay Synchronization / Video Expert Setting. Please search for "sensor delay" here in the forum to find more information.

In case a video is off for some other reason which cannot be covered by the standard delay discussed above, you need to adjust the video sync point like what you have done to get the Time KO / Data OK result.

I assume the Time KO observation is a missing S/F line and timer sync? As said initially, data and timing are in sync by definition. In case you see a difference between timer start / stop and S/F line, this is due to a misplaced trigger. This means the track set used has the GPS position for the trigger set slightly ahead or behind the real position. This can happen due to inaccuracies when defining track sets using Google Earth or when users measure a wrong position and submit the track set. Official positions are rarely available. The good news is the type of gap is largely irrelevant because time starts early and finishes early. This may create a minimal gap to official timing, but will be mostly below accuracy achieved by a GPS based system.

The workaround for the trigger placement is to redefine the track set, export session data to e.g. .vbo and import it again. This will create new laps with adjusted splits. But you will lose some information and any video linking when doing this. In case you have better S/F coordinates, please submit them to Tracks@gps-laptimer.de and we will use them for the official track set.

- Harry