Another use for an SRT file

As many of you probably know, if you enable “Video Captions” in the app, a “.SRT” file is generated along with the video file when capturing a movie. For example, with video captions enabled, you would see a pair of files on your SD card named something like this:

  • DJI_0001.MP4
  • DJI_0001.SRT

With an appropriate player, the contents of that SRT file can then be displayed as video captioning when viewing the video file.

That SRT file, among other things, contains a log of GPS coordinates and altitude information. From that information, one can re-create the path of the flight that was used in capturing that video. One limitation in doing this, results from the fact that neither the heading nor the gimbal pitch angle are stored in the SRT file. As a result, only the path of the drone can be re-created in a waypoint mission.

I have an “Air Data to Litchi Converter” that will convert flight logs into Litchi missions. To that converter, I have added the ability to convert the information contained within an SRT file into a Litchi mission CSV file. That waypoint mission can then be flown using Litchi or converted to a KMZ file and flown with DJI Fly.

If you would like to try this, use my “Air Data to Litchi Converter”.

I didn’t know that! I’ll look for it…

… it might be interesting to some that there is a way to strip an srt file from a DjiFly-made video if subtitles are enabled…I’ve used a Windows application “XMediaRecode”- a video converter (and somewhat of an editor too) that has the capability if you look hard. It can run in Linux wine too.

even easier, a tool named “Subtitleedit”

great to hear you have added this, lots of interesting and useful info in the .srt files, for those not aware, VLC can play .srt files where you see the data, as well as a low res video image of the subject. Some of the editing tools including Resolv also enable you to add .srt as overlays.

Interesting, I don’t remember seeing “Video Captions” option, will have to go looking for it(In Litchi and or Fly by chance?).
Did you know that with the DJI Mini SE at least, the .SRT data appears to be stored on a layer within the .MP4 file? Perhaps it would be easy to extract the data from any drone video file and not even have to enable .SRT creation(Maybe the .mp4 subtitle data holds more datafields? seems like a lot there…)? To see it just play a drone video in VLC and select Subtitle | Sub Track | Track 1…

For others reading this/new… If you don’t wish to share location where your filming; it’s important to strip that layer out(I use LossLessCut) and clear exif file location data (exiftool; Windows 8.1 clear exif data does not clear all location fields!, it won’t show you them all in windows details).

This might be advantageous if/when laws change and the nature of people trying to justify their advanced-welfare(government jobs). ie: Says here you were x elevation, park/other border/restriction… They send out fines for youtubers already…

Yes. It is available in DJI Go4, DJI Fly and Litchi.

I did not know that when I wrote the converter but later found that the newer drones store the subtitle information directly in the video file instead of creating a separate SRT file. The embedded subtitle track may be extracted from the video file using the following tool:

1 Like

The embedded srt that DJI video has can also be extracted “offline” with the aforementioned “Subtitleedit” (I corrected the link I hope)