Demuxing playlists with missing streams in first .m2ts file

[TrippyMoose]

Currently DGDemux is unable to properly demux from playlists that don't have all of its stream present in the first .m2ts file. Reading the info on the -sf switch, it seems that was made specifically for this problem. I was wondering if it is possible to implement proper demuxing of these types of playlists, by for example probing all relevant .m2ts files before demuxing and adding appropriate delays to streams that miss in that first file. Eac3to seems to have implemented something like this somewhere between 3.34 and the current version, but only for subtitles, probably to deal with discs that don't have any subs present for the runtime of the first .m2ts file, which is of course way more common than not having an audio stream in the first .m2ts.

I have encountered this problem in 2 discs;
Arrows UK regular edition "Versus (2000)", https://www.blu-ray.com/movies/Versus-Blu-ray/317216/
and Kino's "Boys (1996)", https://www.blu-ray.com/movies/Boys-Blu-ray/25966/

Thanks for all the hard work on these tools and reading this post !

[Rocky]

Welcome to the forum and thank you for your question.

What is in the first M2TS and why wouldn't you want to skip it? In all these type disks I have seen it is just blackness or color bars.

[TrippyMoose]

Well, to be completely fair, for the mentioned discs it doesn't really matter of course. But this would more prevent issues with potential other discs that might have only video and audio on the first .m2ts with a logo and commentary and sub tracks in the other .m2ts files. For the playlists with only video in the first file it's obvious that something is wrong when dgdemuxgui only shows video and chapters but there might be discs where you could miss some sub files while demuxing and be none the wiser.

I understand that this might be a lot of effort for some logos, and I'm not sure if dgdemux has special handling for sub files that don't appear in the first file, if it has then there might not be any point to implementing this. But there currently is no tool that properly demuxes full playlists like these with seamless branching dts/truehd (ffmpeg's bluray protocol has the full playlist and all the streams in sync but does not have any special handling of duped dts/truehd frames with seamless branching afaik) and I think implementing this would improve the coverage of dgdemux and preemptively fix potential edge cases.

[Rocky]

Sorry but I don't have time or energy to make a complex fix for a potential issue. If you can point to an actual instance of a disk that would benefit from it, I would reconsider.

[TrippyMoose]

I understand, if I ever have any actual issues with a disc like this I'll let you know.

[Rocky]

Thanks for your understanding. Squirrels only live about 6 years and I'm pretty far along on the progress bar of life. So gotta pick my battles carefully.