What kind of Spanish movies do you watch?
What I do with a film if I don't know its FPS is looking some film database like IMDB. There you can find the
duration of most of the films. If you change the FPS from 24 to 25 FPS, in practice it means you shorten the
film by 1 second every 24 seconds.
A 90 minute film would last 5,184 seconds or 86 minutes and 24 seconds. If your film duration is about 4 minutes less than that reported by the database you can say it has speed-up.
How to fix it? I use Gaupol but I think every decent program must have this functionality. I do it so:
- I write down the timing of the first and last subtitles in the actual film. You can get it looking at the elapsed time in the player.
- With Gaupol you can "shift positions" or "transform positions". The former is for adding a fixed time and the later for fixing this. In the dialog box I set both timings (first and last subtitle) and that's it.
Sometimes it may happen that you have some desynchronisation in the middle. Then I repeat the second step adding or subtracting some amount to the last subtitle.