Short SRT subtitles created from Drone


One of the features of my drone is that when recording video it can create external SRT subtitles containing stats (e.g. altitude / longitude / latitude etc.)

However, while it creates totally valid SRT files, these will not play in either Infuse on the iPad, or Apple TV. When playing, a subtitle will appear briefly for a fraction of a second, then disappear, and no further subtitles will appear. The also happens if you seek to a new location in the video.

There are 2 problems:

  1. the srt file is written with an uppercase SRT extension. Infuse won’t recognise these files as subtitle files at all. Changing the extension to lowercase srt fixes the issue.
  2. There appears to be a problem in Infuse with really short subtitles. The drone creates touching subtitles with a duration of 1/60th second each.

Here’s an example 2 subtitles:

00:00:06,752 → 00:00:06,769
SrtCnt : 406, DiffTime : 17ms
2020-06-23 19:56:13,137,196
[iso : 100] [shutter : 1/400.0] [fnum : 280] [ev : 0] [ct : 5759] [color_md : default] [focal_len : 240] [latitude: 0.931526] [longtitude: -0.023676] [altitude: 114.500000]

00:00:06,769 → 00:00:06,786
SrtCnt : 407, DiffTime : 17ms
2020-06-23 19:56:13,153,867
[iso : 100] [shutter : 1/400.0] [fnum : 280] [ev : 0] [ct : 5759] [color_md : default] [focal_len : 240] [latitude: 0.931526] [longtitude: -0.023676] [altitude: 114.400000]

If I increase the duration and change the file extension, then I can get the subtitles to play in Infuse. In fact, I wrote a script to fix up the subtitles to get them to work.

Are there some known limitations with short subtitle durations when using Infuse?