Should a forced subtitle stream (in an MKV) always be the default subtitle stream?

Plex Media Server
7

That is the “forced” one.

That is a regular subtitle.

That is a “SDH” subtitle (“subtitles for the deaf and hard of hearing”), sometimes referred to as “closed caption”/CC.
You enable the “Hearing impaired” flag for that one in MKVtoolnix.
(the flag will light up automatically, if you name the file like shown below)

There is no need to fill in the “track name” in MKVtoolnix for any of these subtitle tracks. Plex can extract all the necessary information just from the flags. This helps keeping the subtitle selector in Plex clean from any duplicate text.

Maigret (2006).mkv
Maigret (2006).eng.aac <--  English audio track, will set the right language tag when dragged into MKVtoolnix
Maigret (2006).ger.aac <--  German audio track, will set the right language tag when dragged into MKVtoolnix
Maigret (2006).eng.srt <-- regular subs for English speaking audience
Maigret (2006).eng.sdh.srt <-- CC/SDH subs for English speaking audience
Maigret (2006).eng.forced.srt <-- signs/foreign language subs for English audience
Maigret (2006).ger.forced.srt <-- signs/foreign language subs for German audience

The above is just an example. I’ve already made more complicated ones with 3 languages involved and additonal “commentary” audio and subtitles.

IMO this flag is only useful for audio tracks. You should set it only on audio tracks which have the movie’s original audio language. (and not on special audio tracks, like “commentary” tracks etc.)
It is intended for people who like to watch movies always in their original language, (with subtitles or not – depending on the user’s preferences.) Using this flag, a player can know which audio track to enable automatically if it’s instructed to play a movie “with original audio”.
While Plex doesn’t do that currently, it has been equipped to read this flag and store it in its own database. So it could support the above use case in the future. If you start tagging your movies accordingly now, they will be ready to use that feature if it gets implemented.

Here is the Plex mediainfo XML of one such stream. Notice the original="1" XML property on it. This has been read from the original flag in the MKV file.

<Stream id="2129844" streamType="2" selected="1" codec="aac" index="2" channels="2" bitrate="221" language="Englisch" languageTag="en" languageCode="eng" audioChannelLayout="stereo" original="1" profile="lc" samplingRate="48000" displayTitle="Englisch (AAC Stereo)" extendedDisplayTitle="Englisch (AAC Stereo)"> </Stream>

The language tag of a forced subtitle stream should be enough to enable a player to make a decision whether to enable it or not.
As I said above, “original” only really makes sense for audio tracks.

2 Likes