General question about discs with multiple PGS files

[BrianInSC]

Hello!

Just curious why some discs have multiple, in my case, English PGS files. Here's just one example from Mission Impossible Final Reckoning.

Screenshot 2026-04-21 074437.png (92 KiB) Viewed 244 times

[tomty89]

Sometimes they just dup things for no reason. I have a UHD BD that dup the video track of the whole movie in another M2TS (but without the audio tracks and subtitles). The two video bitstream has been proven to be bit-exact identical.

Also maybe some of them are not dups, but like "closed caption" (i.e. with text for "sounds") and "subtitle"? And maybe subtitles for commentary audio track?

[Woodstock]

The "forced only" is a constructed subtitle track, pulling just those subtitles flagged as forced. Generally, it will be empty and tossed out, because ...

Multiple tracks for the same language usually mean the "full subtitles" and "just the forced subtitles". Sometimes, there will be subtitle tracks for commentary, so there can be 3 or more for the same language. I remember a Star Wars movie that had multiple commentary tracks, for different actors in the movie. Oh, and it also had "forced only" tracks for those secondary subtitle tracks.

[BrianInSC]

Thanks folks.