Subtitles falling behind

[Mister Steve 28]

Recently a lot of subtitles started falling behind, at the start of a show they'll be in sync but after an hour the subtitles are 8 seconds behind for example.  The same issue exists whether playing via browser, LG tv, or Chromecast.   Ver 4.5.4.0 on Debian.  This may have happened with a recent update, not sure.   Other aspects of subtitles have improved, the search/download is working great.  Any suggestions?

Thanks

[Ronstang 202]

Are these subtitles that you extracted from a TV recording or those that come with a DVD or Blu-Ray?  Or are these ones you download from Open Subtitles?  If the latter then the issue is more than likely Emby had downloaded subtitles for a different FPS (frames per second) video and thus the longer you play the more the subtitles will either fall before or after the words are spoken in the video.  This is a huge problem for me since Emby has no way to compare your videos FPS to that of the subtitle file it downloads.  For this very reason I turned off automatic subtitle downloads and I fetch them manually so I can not only pick the right FPS but try several subs since not all are of decent quality.  For some movies/shows I have had to try 3 or 4 subtitles from Open Subtitles to find ones that are correct.....then I note the user who uploaded them and that user is at the top of my list for future sub choices.

Edited January 26, 2021 by Ronstang
clarity

[Mister Steve 28]

The issue may be only with open subtitle files.    I used some of the subtitles emby downloaded with VLC and they do not sync either, looks they are simply poorly timecoded.   It does not make sense to me that subtitles need a FPS match, the time is expressed to the millisecond and not to the frame. 

 

[Ronstang 202]

I know it doesn't make sense but it can definitely make a difference. When I have downloaded subs for 25 FPS and tried them on my 23.97 FPS files they get out of sync over time.  I have done some reading on this issue and it seems that the problem arises due to converting from one format to another and the presentation timestamps of the frames can change.  Once again time is time and so and SRT sub should stay in sync but my experiences say different.  

Edited January 26, 2021 by Ronstang

[rbjtech 4255]

As pointed out above - the issue is not the subtitles per say, the issue is the subtitle timestamps are simply not matching the movie playback speed.

To fix this, option 1 is to download the correct subtitle as @Ronstang says above, but if that's all you have/is available - then applications such as the excellent (and free..) subtitle edit allow you to correct/edit the timestamp by frame rate.  ie you can 'slow down' a 25 fps subtitle to match a 23.976 film

 

 

 

[crusher11 851]

11 hours ago, Mister Steve said:

The issue may be only with open subtitle files.    I used some of the subtitles emby downloaded with VLC and they do not sync either, looks they are simply poorly timecoded.   It does not make sense to me that subtitles need a FPS match, the time is expressed to the millisecond and not to the frame. 

 

Yes, but if you play a 24fps film at 25fps, it goes faster. A two-hour movie will end up about five minutes shorter.

[pwhodges 1527]

Some subtitle formats can specify the position by frame numbers.  If the wrong frame rate is used when converting such subtitles to a format which uses timestamps, then this kind of error occurs.  And PAL (European) encodings of videos often run faster, and so need a different choice of subtitles.

Paul

[Glin 7]

I found SubSync to be a very useful tool in order to synchronize subtitles with audio.

- Glin