Server Version#: 1.21.3.4046 (Synology NAS)
Player Version#:8.13.1.23036 (SHIELD Android TV)
I’ve come across a bug in which I thought worthwhile to bring to the attention of the forum.
I’ve recently purchased the new LoTR trilogy extended edition in 4K and wanted to copy them to my plex library. I made an MKV of each disc (due to the length, the films are presented over 2 discs) and them muxed the two together using MKVToolnix. I added the chapter names and thought that was it.
Being a SONOS user I only opted to save the TrueHD 7.1 / Atmos track for each but on the first watch through of Fellowship of the Ring (FoTR) I noticed that after the council of elrond scene as the movie transitioned from Disc 1 to 2 portions, the audio went out of sync. It is also noticeable on The Return of the King (TROTK), but for an explainable reason, The Two Towers(TTT) works perfectly.
Through much analysis, my only conclusion has been due to the second discs of FoTR & TROTK having an audio duration longer than the video. Therefore, when muxing them together the audio track duration is longer than the video track, by longer I mean a nanosecond! You can see this if you use mediainfo and select JSON to view the attributes of the media file. The same is not present for TTT in which the Audio and Video duration is exact on both discs and also when muxed!
To prove the issue is not on my muxed file I have tested on both VLC (PC and Shield) and PlexKodiConnect(Sheild) and they play the combined mkv fine - audio keeps in sync when bitstreaming the TrueHD track.
The problem also goes away if I transcode the audio in Plex and don’t bitstream. If I transcode to my Sonos ARC it’s fine, if I bitstream i get the sync issue.
Why this causes Plex to error I don’t know, I also noticed that simply rewinding 10s solved the sync issue (once on the second disc portion of the movie)
One fix I found was to keep the the two mkv files seperate on a pt1.mkv and pt2.mkv format and have them stacked. This of course isn’t supported on the new player on the Nvidia Shield so I had to disable that and watch on the old player. A downside to that is I no longer have the chapter thumbnails and their description!
I can’t think of any other releases that may have had a TrueHD / Atmos track and needed to be muxed together to create a single file so perhaps this is a first time kind of file presented to Plex.
