Author Topic: Time tagging  (Read 6093 times)

kaklik

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Time tagging
« on: July 15, 2021, 02:58:31 PM »
What is the best way to capture a video, which should be possible to time-align to absolute time (e. g. UTC.)? The required precision of time alignment should be comparable to the exposure time.
I noticed that there is possible to install the ntpd to the camera OS, which is a good base for timing. But I do not know how to mark the system time precisely to the video.

Also, I noticed that there is a time in the text overlay, It seems it always shows a time of around 17xxx seconds. But It is unclear for me which time is a zero?
« Last Edit: July 15, 2021, 11:37:41 PM by kaklik »

NiNeff

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Re: Time tagging
« Reply #1 on: July 19, 2021, 10:48:26 PM »
The timer in the video overlay always refers to your triggerpoint, and depending on the triggermode it couunts down (post trigger) or up (pre-trigger). The ~17 seconds are roughly the maximum record time for a 32GB RAM camera model, so they are somewhat expected.

As far as I know, the Cameras on-board Wallclock-time is only used for filenames and can't be embedded in the videos. Also, It's not really precise.
The best way to exactly align the shot to an external time reference would be to use capture the triggertime (e.g. via external hardware) and then sync to that afterwards.

Nikon1

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Re: Time tagging
« Reply #2 on: July 20, 2021, 06:13:08 AM »
As far as I know, the Cameras on-board Wallclock-time is only used for filenames and can't be embedded in the videos. Also, It's not really precise.

 I did save the Same Recording from RAM multiple times to different File Formats, and it will create Files with date and time Labeled after the moment you press the Save-Button on the UI (don't know how it exactly works for remote Controlled Saves), so that should be correct.

kaklik

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Re: Time tagging
« Reply #3 on: October 31, 2022, 02:09:15 PM »
I solved that by using an external trigger signal and GPS receiver with interrupt input. Specifically the https://github.com/UniversalScientificTechnologies/TIMESTAMPBOX01
But there are trouble logging metadata to recordings because the raw file format does not contain any information about the trigger position.

Therefore the more sophisticated variant of that use case is still unsolved https://forum.krontech.ca/index.php?topic=738.0