Request: "Check for Forced Subs" Option!

[samtoy]

Hi all,

as we all know, sometimes there are forced subtitles embedded into the normal subtitle stream. These forced subtitles have to be extracted to a separate stream, which MakeMKV thankfully is capable of.

But we never know in advance *if* there such forced subtitles are inside the chosen subtitle stream. So a "Check for forced subs" option would be super-helpful.

Right now I always have to extract the subtitle stream using TSMuxer and then check it for forced subs using BDSup2Sub. This is very time consuming and annoying.

So, is there any chance that this option will be added to MakeMKV?

Cheers,
S.

[mike admin]

The whole file must be scanned to see if forced subs are there. It's recommended to always enable forced streams - if it turns out that there was no single forced subtitle in a stream, MakeMKV would remove track from output file automatically.

Do you suggest a separate scanning pass to figure out if forced subtitles are present? Sounds like a waste of time.

[samtoy]

Thanks for the fast reply, mike admin!

OK, I see. I didn't know that MakeMKV removes an empty forced subtitle track automatically. Wow, that's perfect!

Out of curiousity: How is this technically possible? MakeMKV only knows at the *end* of the muxing process that there are no forced subs in that extra (and already muxed in) subtitle stream. And I guess there still must be *some* kind of (meta)data even in an empty subtitle stream. So, how can this useless subtitle stream be removed without muxing the file again?

Cheers, S.

[samtoy]

OK, I found it out (partly by accident):

Those "empty"/unneeded forced subtitle streams are still present in the MKV files and take up up to 20 MB, just like normal PGS subtitles. They get deleted by MakeMKV only in the header information and still appear as subtitle streams (although without Track ID/Name) in MKVExtractGUI2.

So IMHO, a scan *before* the the muxing could avoid potentially muxing an unneccesary 20MB subtitlestream into the MKV file. Even if it would take up more time, I would prefer it. But that's just me, of course.

Cheers,
S.

[mike admin]

Those "empty"/unneeded forced subtitle streams are still present in the MKV files and take up up to 20 MB, just like normal PGS subtitles. They get deleted by MakeMKV only in the header information and still appear as subtitle streams (although without Track ID/Name) in MKVExtractGUI2.

This is not how it should be. If the track is empty, then it has no data. You are correct, track header information gets erased but it's tiny. The only consequences would be:
1. empty space from the header, about 100 BYTES.
2. Track IDs will have gaps, so you ill have like track #1, track #2, track #4.

I guess MKVExtractGUI2 is confused by gap in track numbers. But in no case the data is in MKV file.