Confusion: Forced Subtitles

[Krawk]

I have a bit of confusion with regards to subtitles.
Regardless of the disc, if the film has subtitles, I am always presented with the option to rip subtitles, "PGS forced only".
The confusion is that literally less than .1% of the discs I have ripped actually have forced subtitles. Based on program usage though, every single disc has forced subtitles, which is very far from the truth. Is this merely a disc structure component? Is there a site to use that shows what discs truly need forced subs?
This is the only site I have found to determine if it is wise to rip the subs:
https://docs.google.com/spreadsheets/d/ ... k/htmlview

[Radiocomms237]

To begin with, there are no separate "forced" subtitle tracks on the disc, these are generated by MakeMKV itself and added to the .mkv container as a whole new subtitle track.

Within each subtitle file on the disc, it's possible to mark certain lines of text as "forced", which means the disc menu will display those individual lines even if subtitles aren't selected. This is typically used for translations of on-screen text or for sections of the audio track in a foreign language.

The disc menu does this using the language selected for the audio track (so if you select the French audio track, it automatically displays only the subtitle text marked as "forced" within the French subtitle track). For example, in the French parts of Canada it's law that any text (street signs, restaurant menus, on-screen text within videos, etc.) has to be provided bilingually, in both English and French, so a title for sale in this area must have the French translations for any English text displayed.

The problem is, once we rip the title to an .mkv file, we no longer have the benefit of the disc menu to pick-out these lines of forced text for us, so MakeMKV picks them out and places them in a new subtitle track, IE. "Forced-only" subtitles.

Circling back to your original question, MakeMKV doesn't know what's in a subtitle file until after it rips it, so there's no way to tell in advance whether any of the lines are marked as "Forced". But we need the option to tag these lines before ripping the disc so they can be identified afterward, so MakeMKV adds a 'placeholder' for these forced subtitle tracks in advance, and then removes them again if they turn out to be empty at the end of the ripping process.

The upshot of all that is, unfortunately, there's no way to tell whether you need these forced subtitles without ripping them and having a look. I will say that some titles need these lines of forced text even in English, so it comes down to the individual disc and how it's been authored, there's no blanket answer.

Clear as mud?

[schlurfi]

I hope it's okay to join this thread.

Thank you for your detailed explanation. I think I understood it. In the logs I find several entries that forced subtitles are empty and therefore removed from the output file. This will probably always be the case if MakeMKV didn't find any subtitle that was flagged as "forced" during ripping.

so MakeMKV adds a 'placeholder' for these forced subtitle tracks in advance

I can see these placeholders when ripping BluRays, unfortunately this option is not available when ripping DVDs.At least not for the ones that I tested. The first "Men in Black" movie and Triple X for instance have both these "forced subtitles". Men in Black for the alien language and Triple X e.g. in the club scene at the beginning of the movie.

When I'm ripping these movies I only get one subtitle track (in my case german) with all the subtitles in it. The ones that should be "forced" and the "normal" ones. So when watching the movie I only have the possibility to miss out the meaning of the parts with foreign language spoken or to display subtitles even when the dialogues are in german.

Am I missing some configuration option that enables this "PGS forced only" also for DVDs?

[Sunoo]

Most likely the DVD is forcing one of the “normal” subtitle tracks on and using that for the alien subtitles. I don’t have the movie, so I unfortunately can’t tell you which it would be. In your example of German, I’d expect there to be two different subtitle tracks both labeled as German, and one would be “normal” and the other would be “forced”. However, I’ve also seen forced subs flagged as some other language.

[Chetwood]

Clear as mud?

Mmh, some of your statements appear not to be entirely correct. AFAIK there are (at least) three methods for forced subs on BDs:

1. a separate track that only has forced subs (the items themselves may be flagged as such or not)
2. a separate track that has only forced subs but is not flagged (nor are the items - they are turned on by navigational commands)
3. a general track that also has several items which are flagged as forced.

MakeMKV recognizes #3, items that are flagged as forced inside a track of regular items. This happens rarely on US BDs (notable exeption which is often mentioned on this forum: Avatar) but a lot on German BDs where e.g. signs are translated. With the option checked, MakeMKV will create an extra track and that will be discarded when no such items are found during ripping.

[Chetwood]

Am I missing some configuration option that enables this "PGS forced only" also for DVDs?

No. Both MIB and xXx have forced items inside their regular tracks but unlike with BD PGS, MakeMKV does not recognize them. You have to extract them with e.g. VSRip and then extract all forced items into a new track with BDSup2Sub, then mux this new one into the MKV with MKVToolnix. It's easier to just convert the BD instead.

[schlurfi]

Thank you for all your answers.

In your example of German, I’d expect there to be two different subtitle tracks both labeled as German, and one would be “normal” and the other would be “forced”.

I found some DVDs (like "Alien" with Sigourney Weaver) which have different tracks like you explained. Unfortunately this is not the case for every DVD.

No. Both MIB and xXx have forced items inside their regular tracks but unlike with BD PGS, MakeMKV does not recognize them. You have to extract them with e.g. VSRip and then extract all forced items into a new track with BDSup2Sub, then mux this new one into the MKV with MKVToolnix.

Ok, thanks for the clarification and especially for the names of the tools in the toolchain. BDSup2Sub is just great and exactly the tool that I was looking for. In the meantime I made some more tests and found out that, although MakeMKV isn't capable of exporting the forced ones only like with BD PGS, MakeMKV preserves the forced flag for individual subtitles within the track. It wasn't easy to find out because VLC doesn't display only forced ones. With this software it's all or nothing. Kodi on the other hand can display only the forced subtitles out of the track with normal and forced ones.

So my current workflow looks like this:
- Ripping a DVD with MakeMKV
- Exporting all subtitle tracks with MKVcleaver
- Checking the content of the subtitle tracks with BDSup2Sub
- If there is no separate track with forced subtitles: Loading the normal track in BDSup2Sub. Thankfully it displays at the end of the loading process wether it found forced subtitles or not
- If forced subtitles were found: Exporting them into a separate file and merging them with MKVToolnix

It's easier to just convert the BD instead.

You're right but this only works if I have the movie also on BD. In that case I wouldn't bother ripping the DVDs first. But I'm still hesitating to buy all movies which I own on DVD another time on BD.

There is just one thing missing, perhaps you can help me with a hint for another tool: Sometimes the subtitles are missing the forced flag. This is for instance the case in Monty Pythons "The Meaning of Life". Like MiB and xXx the forced subtitles and the normal ones are within one track but for example the german subtitles for the english song doesn't have the forced flag. Do you know a tool with which I can edit the forced flag of individual subtitles? As far as I could see, with BDSup2Sub I can only set the flag for an entire track.

[Chetwood]

In the meantime I made some more tests and found out that, although MakeMKV isn't capable of exporting the forced ones only like with BD PGS, MakeMKV preserves the forced flag for individual subtitles within the track. It wasn't easy to find out because VLC doesn't display only forced ones.

Haven't tested this in a while but IIRC VLC does react differently to default/forced subs when a default language is set. MPC-HC does show items flagged as forced even when the track is not.

Do you know a tool with which I can edit the forced flag of individual subtitles?

Nope. That might be a worthy feature request for BDSup2Sub(++) in case there's someone still working on it. Alternatively you could post on the subtitle sub forums of Doom9 or Videohelp.com or maybe even Reddit. Good luck.