Subsync is a program that will sync any subtitle file based on either audio or another subtitle. It is remarkably good at syncing any subtitle you throw at it. I never encountered anything even remotely as good as Subsync for that task.

Unfortunately, the author archived it due to some technical reasons as well as bad interactions with users. I don't believe there is anything as good out there when it comes to syncing broken subtitles. Subsync still works, but I don't know for how long. I am not a programmer. I am posting this as a call for help: if anyone is interested in maintaining this program, I think it would be of great help to a lot of people.

Right now, Subsync is a manual tool with a graphical interface. But I foresee it working in the background with programs like VLC, Plex, or Stremio. That would be awesome.

EDIT

Subsync is automated and language aware. It will sync individual lines using audio or another subtitle as a reference. It won't just shift everything; it will adjust them individually. It is usually not necessary to go through the entire file, but you can do it for badly synced subtitles. Adjusting every single subtitle will take more time, but you can do it.

Merely shifting all the subtitles won't work for older TV shows because of the breaks. Depending on the version (DVD, Blu-Ray, WEB, or recorded directly from TV), the ad breaks will be edited slightly differently, with different delay times before resuming the show. That is enough for the subtitles to lose sync after every act. There is also the issue of frame rate and perhaps other video features, which I believe can also unsync subtitles. I probably have more issues with subtitles than most because I mostly watch older or classic TV content.

(Adapted for clarification from my response below)

On my desk I have two screens -- one off to the side for movies, TV, etc and my main in front. Sometimes I find myself wanting subtitles on my main screen. The main issue I've found, at least with macOS, is that the SRT players suck.

I figured, why not just generate a tiny black video with embedded subtitles?

ffmpeg -i subs.srt -t 3:00:00 -s 40x10 -f rawvideo -pix_fmt rgb24 -r 25 -i /dev/zero subs.mpeg

Set the ratio to be super small without being too small. This video is 40px by 10px and the video only takes a few seconds to generate. For me, this generated at ~850x speed.

From there, jack up the subtitle font size and shift it up a little bit so nothing gets cut off. This also works really well with tiling window managers.

Screenshot

Eternal Love is a very popular Chinese romantic drama currently available on Netflix Canada. I originally had the English subtitles on, but eventually turned them off (as they were distractingly poor). As with a lot of period Chinese dramas with a female protagonist, there's crossdressing. Our main character pretends to be a guy, is accepted under a great master and trains alongside 16 other (all male) disciples.

I should mention here that Chinese is generally not gender specific. Written pronouns are basically for everyone, for female only (not really used, but seeing more use now for translating foreign media), for living creatures (like dogs and cats) and really specific uses (such as inanimate objects). When spoken, they all sound the same.

In this show's substitles, I noticed a very inconsistent use of pronouns for our main character. Since no one knows she's a woman, I expect the masculine form to be used. However, it often jumped to the feminine. My sister pointed out that it seemed like they stuck with the masculine in general, but switch to the feminine when talking about her romantically. So you end up with lines like "Shouldn't he be here?" and "Master's always had a soft spot for her." said by the same people.

This obviously made the show really confusing for me where I wasn't sure if everyone knew she was a woman. I know there's often ideas, feelings and more lost in translation, but this is one of the few times I felt very different message was sent in the original Chinese language (where a gay relationship was implied and accepted) to English (where there clearly wasn't a gay relationship).

Here, I should note that gay relationships in media and in public is not legally accepted in China. So I don't believe this was malicious. The Chinese version heavily implied a lot that couldn't be outright said, but translating it probably didn't afford the same liberties.

Thoughts? With so much international media easily available now, have you noticed anything similar?