When multiple audio streams and forced subtitles available, select forced subtitles based on selected language

This is somewhere in-between a bug report and a feature request.

Background

I have a video with these streams packed in the container (sample included):

• Video stream
• Audio stream 1: English
• Audio stream 2: French
• Subtitle stream 1: English, default: no, forced: yes
• Subtitle stream 2: English, default: no, forced: no
• Subtitle stream 3: French, default: no, forced: yes
• Subtitle stream 4: French, default: no, forced: no

In my video, English is the original language, French is dubbed. The forced subtitles are included because somewhere in the movie a language is spoken other than English or French.

Current behaviour

When I change the playback language from English to French, the active forced subtitle is not changed accordingly

Expected behaviour

When I change the language from English to French, the active forced subtitle is changed from the English one to the French one. This would be according to Matroska Specifications:

When there are multiple "forced" tracks, the player should decide on the language of the forced flag or use the default flag if no track matches the use languages.

I hope this can be fixed/implemented!

Multiple forced subtitles, test file

Added attachment:

• Multiple_forced_subtitles_test.mkv

Sorry, I disagree.

Changing audio track lang should not change subtitle lang.

That's unfortunate. I think it's against the idea of the Matroska developers. But I'll rest my case. Ticket can be closed then.

The Matroska specs explains what you have to do to select the track the first time.

It does not say to change something when something else changes.

Fair point. But then take this scenario: I'm French and I've set French as the preferred audio language in the general settings of VLC. When playing the example file, VLC will now play French audio with forced English subtitles. I think that's a case where VLC should know to play French subtitles from start (and of course the user can still decide to select different subtitles if wanted). It's indeed different than what I started the ticket with, but it would still be an enhancement in my opinion.

I think that's a case where VLC should know to play French subtitles from start (and of course the user can still decide to select different subtitles if wanted).

I also tried the behaviour of another well-known video player, Kodi, in this situation. Kodi does select the matching forced subtitles. Even when changing the audio-language while watching.

Replying to [comment:4 madada]:

But then take this scenario: I'm French and I've set French as the preferred audio language in the general settings of VLC. When playing the example file, VLC will now play French audio with forced English subtitles. I think that's a case where VLC should know to play French subtitles from start (and of course the user can still decide to select different subtitles if wanted).

Sure, that's a valid bug.

assigned to @robUx4

added Component::Core label

marked this issue as related to #1135