How do subtitles work?

[xtrips]

:confused:Hello,

I always wondered why some sub files sync well with movies and some don't.
I usually see HighDef movies (720 or 1080) in mkv formats but not only (sometimes ts, avi, wmv, mp4).
The subs I usually find are srt.
I don't understand why sometimes they lose sync constantly.
I thought it might have to do with the framerate (mkv are usually 23.976fps while dvd can be 25fps for exemple right?).
But then again if i look inside the srt the only reference is the time, and the time (movie length) is absolute.
So how does it work?

Thanks

[dat720]

The Sub's maybe from a different source, which has more or less content in it or starts at a different time or has a longer intro, there are many reason's why sub's can be out of sync, the only sure fire way to get the sub's in sync is convert them yourself off the original DVD!

(mkv are usually 23.976fps while dvd can be 25fps for exemple right?).
Yes and No if you are refering to HD/BR MKV's they are generally 23.976fps but DVD can also be 23.976, DVD Rip's should be the same fps you find on the disk if if the disk is PAL your dvd rip will end up at 25fps, if it is NTSC on the other hand it will end up at 29.97 or 23.976 fps.

Be careful with what you say next, your post is borderline rule 6, don't want to know where you get these files or why you don't do the sub's yourself, don't get me wrong there is nothing wrong with downloading sub's but you can just as easily do it yourself in the time it takes to download and test 4 or 5 different srt files.

[davexnet]

The other thing to mention regarding subtitle synch - subtitles sourced from a PAL
movie will not synch up with an NTSC sourced version of the same movie .
It's because the running times are different, PAL is generally speed up 4%.

With a bit of patience SRT files can be re-timed and made to work.