How to check if a given subtitle file is the right one

subtitlesvideo

I very often use subtitles on my mkv player to watch movies. I have frequently observed that there is sometime a lag between the subtitles and the actual video. Even after setting the subtitle offset one would have to go on increasing it as the movie proceeds. This is something i find extremely annoying and would like to know if there is any way when one can check if a subtitle file is the ideal one for a given video.

Best Answer

There's no way to automatically check if given subtitles match a video perfectly. You would need the ideal ("gold standard") subtitles as well, or some way to match the audio track against the words in the subtitle file, and it goes without saying that this is not practical.

Your only chance is to …

  1. Align the subtitles manually at the beginning
  2. Skip to the end of the video and see if they still line up

Or, alternatively, manually export the subtitles and check their timestamps: How to extract subtitles from MP4 and MKV movies

The question why subtitles drift and run out of sync is very broad. There could be various reasons for that:

  • The video source and subtitle source are not the same. There are always different cuts of movies, or the version you have doesn't include a trailer, et cetera.

  • The video was converted. In that case, converting between different frame rates. For example, NTSC specifies 23.97 frames per second whereas for cinematographic material, this is sped up to 24 frames per second. And then there's 25 fps and 50 fps too, depending on the release.

Either way, the presentation timestamps of the subtitles don't match anymore, since they're not aligned to frames, but timecodes. Since the presentation timestamp of a frame can change with conversion, you see the subtitles drifting gradually.

To summarize, all you can do is check your given subtitles manually and try to replace them. If it happens with all material you have, then I'd rather suspect a hard- or software issue at the player side, which incorrectly demultiplexes the MKV container. Try another player or hardware solution and see if it fixes the problem.

Related Question