[FAQ] Fixing video / data alignment

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[FAQ] Fixing video / data alignment

Post by Harry »

When using LapTimer with video operation enabled, it stores sync information between data and video that allows a later overlay (see Video Documentation on http://www.gps-laptimer.de/documentation). This is the same for both using the internal or external cams.

There are situations however, this doesn't work. Examples are some cam startup issues / delays, or when sync has been changed accidentally using LapTimer's user interface. The steps below describe how to fix a misalignment for situations like this.

NB: in case all your videos show the same offset to lap data, the sensor / cam timing does not match LapTimer's standard settings. You need to adjust the data / video offset using the Overlay Synchronization / Video value in LapTimer's Expert Settings in this case. Do not adjust the alignment individually in this case.

Steps to adjust an individual misalignment:
  1. Make sure your lap has the original video assigned: select the lap from Lap List and scroll down to the Video section. In case the type shown is Overlaid Video, press Revert (or Original).
  2. For iOS, switch to edit mode using Edit and select the video in row Preview. You are in the Video Synchronization dialog now.
  3. For Android, memorize the lap number shown in the top left (e.g. Lap #4) and select the video in row Preview. Scroll to the bottom of the page and select LapTimer Integration / Lap #4 (or the number memorized). You are in the Video Synchronization dialog now.
  4. As described in Video Documentation, this is the dialog showing the alignment of the end of the lap to a video frame in the video. The frame you see should match the finish line roughly.
  5. In case you see the finish line already, please use the blue buttons to adjust the sync slightly. Take care to use small steps. 0.5 seconds do not sound a lot, but are perceived as complete mis-alignment. Do not use the video frame shown to fine-adjust things. Especially for the Android version, the frame shown is probably only one of the "key frames" and not precise.
  6. In case the frame shown is completely off, select a frame showing the finish line. Take care to select the correct lap!
  7. To verify the result, press Set. When asked whether you want to adjust just the lap or the complete session, select Session. For Android, press the back button to get back to Lap Details.
  8. Press Play to test the result. Acceleration and RPMs (OBD) are the best indicators to verify the alignment. Repeat starting with steps 2. or 3. in case the alignment is not perfect yet.
- Harry
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