Multi-Part File Merge Dropping Audio Track

[bplewis24]

Server Version#: 1.21.3.4046
Player Version#: 8.13.0.22986

I recently added Lord of the Rings 4K UHD .mkv files to my library. Each movie is on two separate discs. When the files are not utilizing the " - ptx.mkv" naming convention they show up separately in plex. When they show up separately, both audio tracks show up in plex, the default TrueHD 7.1 track, and the core AC3 5.1 track.

However, when I name them using the multi-part convention, plex merges the files as expected, but then inexplicably drops the TrueHD audio track from the metadata and the track is unable to be selected under playback settings. It’s like it just disappears.

If I change the file name for either one of the parts in a way that splits them apart in plex, the TrueHD audio track shows up again:

Any ideas?

[bplewis24]

So, I’m not sure why…but I kept removing the files and adding them back into the folder and eventually plex picked up the audio tracks. It’s like a crapshoot…sometimes when I moved the files out and back in, it dropped the audio, and other times it didn’t.

The other interesting thing is that when it drops the audio, it also drops the Dolby Vision flag (for lack of a better term). When I play back the file with the missing data/flags, not only is the TrueHD track not available, but Dolby Vision isn’t. When the metadata is present for TrueHD, it also plays in Dolby Vision.

[OttoKerner]

I recommend you to simply avoid multi-part videos.
Use [HowTo]: joining multi-part movies files with MKVtoolnix GUI