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GoProVideoSupport / SynchronisationAccuracy

GoPro video Sync Accuracy

How accurate is the synchronisation between the video and the data?

The video and data is automatically synchronised using GPS. The GoPro embeds GPS data and accelerometer data inside the video file which the Race Technology software decodes.

The software initially automatically synchronises the video and data within <0.5s using GPS only; this error is caused be latency from the GPS data calculation which varies between GoPro models and settings.The software will attempt to improve the synchronization by ‘shifting’ the data forwards/backwards matching accelerometer data which was no significant latency giving a typical accuracy of <0.1s.

If higher accuracy is required the Race Technology software offers the ability to sync the data manually by selecting a video frame that matches a data point.

It is this manual synchronization that is tested for accuracy in this page.



Test overview

The test consisted of videoing a flashing LED connected to the data logger's analogue input. Graphing the analogue input would show a switching voltage corresponding to the LED being on or off. Selecting data points before and after each transition would display the videos frames showing LED on/off.

  • Race Technology data logger set to record at 100Hz.
  • The camera used was the GoPro hero 8 black configured to record at 240fps @ 1080p.



Video capture is playing the Analysis in slow motion. When graph transitions down the LED should go on and when transition up should go off.

This is using GPS time only to sync the data. It is not possible to sync using accelerometer data when stationary. The sync error is 0.49s.



In the Run Manager you can manually set the a corresponding data point and video frame.

In this example the data point 19.64s is the point the graph transitions down and the video from 9079 is the frame the LED comes on.



Once sync is clicked in the Run Manager the video and data will take on the new synchronization.

The screen capture now shows the LED going on and off perfectly in sync with the transition of the graph.



After approx. 5 minutes of recording the synchronization is still within 1 data sample 0.01s.



Summary

The synchronization is accurate within 1 data sample (0.01s) after 5 minutes of recording.

Due to the different logging rates a varying sample maybe sync’d. For example video recording at 30fps with data logged at 100hz will have 3.333 data samples for each video frame. This will cause the video to switch either side of a particular syncing data point.

Page last modified on January 06, 2022, at 09:22 AM