[guessmyname]

I haven’t tried this command, but I believe the use case is as follows:

• Open audio/video file with —supposedly— synchronized file

• After a few seconds, I realize the subtitles appear before/after the dialogues

• I immediately close the multimedia player, and open the Terminal

• I execute the “subsync” command which does who knows what

• Open the SRT and discover that the subtitles are now in the correct timestamps

• ???

• Profit

[smacke]

Pretty much! Given the anecdotal success I've personally had with this approach, I'm hoping it could get picked up by VLC so that the algo can be run in there directly.

[zeotroph]

Previously: Fiddle with the subtitle/audio offset factor (and then they drift apart again slowly, driving you mad!)

Now: subsync

Soon: Players run subsync internally the press of one button or commandline switch.

The voice audio detection and then mapping is such a neat solution. I would have embedded parts of the surrounding audio in some base64 format into the subtitle file and then used that as an alignment clue. But this won't work when the languages don't match.

[smacke]

Actually, it unfortunately doesn't work if the drift gets worse over time -- so far, it only works with constant drift. Maybe fixing constant 1st derivative drift is the next step!

[acqq]

The drifts come from different speed of videos compared to the speed of the videos for which the titles were done.

E.g. if one subtitle is made for 24 frames per second speed (classic film speed) and you have a video presented in 25 frames per second (common in Europe). The original two hours video in 24 fps is then 5 minutes shorter in the Europe-origin version. Or the opposite: the subtitles for 120 minutes would at the end appear 5 minutes before!

Apparently there are some other speed changes, for which I don't know how they happen.

I have done one such correction once, using the linear function to model the correction ^based on the target times of the first and of the last title.

[aasasd]

> only works with constant drift

I hoped that this solution would sync parts that have really different offsets between the audio and the subs, including changes from negative to positive offsets. Because that's the cases where automatic fixes in e.g. Aegisub don't suffice.

This happens when the vid and the subs are from different releases which apparently were edited for some reason―regional releases or something. Like, after some point the subs are suddenly off by a minute.

[kumarharsh]

Oh! Yeah, that makes absolutely perfect sense! I just asked the same question here regarding the difference in FPS of video and subtitle.