Your subtitles are well set at the beginning of your video, but gradually you notice a discrepancy that quickly becomes unbearable?
There is a simple solution to remedy it.
It's probably a problem related to the FPS and it's easy to settle with the appropriate software.
The FPS: Frame Per Second is the number of frames per seconds of your video. There are mainly two values FPS: 23.976 and 25 frames per second.
Well, the subtitle may have been synchronized to a video that has an FPS rate different from yours.
Your subtitles file associates the text with timing, and not to a number of images. So if your video doesn't have the same FPS than the one use to sync the subtitle, there will be a gradaul offset of your subtitles with the image.
To handle this issue, we need software to edit subtitles, namely Subtitle Workshop, available here.
Chage the FPS
Unpack the archive you downloaded and then install the software on your computer.
Launch the software, and you will be able to edit the FPS.
To do this:
Load subtitles, select file.
It remains only to modify the FPS entry of the subtitles:
If you had an FPS of 23,976, change it to 25;
you had one of 25, then change it to 23,976.
Once this change is made, you will find that the timing of your subtitles have been altered.
qNow, the gap between your subtitles and your video should be gone.