My roku uses optical out to my receiver and is thus limited to AC3 5.1. When I play a movie via Plex that has a primary soundtrack like DTS-HD MA 7.1 and an AC3 5.1, if I keep playback using the DTS-HD soundtrack, playback works just fine as Plex is transcoding to AC3 5.1. If I select the AC3 5.1 soundtrack, the audio is Direct Steam but playback ends very shortly after is starts. If a play a movie where the primary audio track is AC3 5.1 then playback via Direct Stream works without issues. Anyone know why this occurs? Also would the quality of the transcoded AC3 5.1 be the same as that of the AC3 track on the movie? If that’s the case trying to get Plex to direct stream the AC3 5.1 track may not be worth the trouble.
Are you using an Ultra? What are the audio settings for the device?
Yes, it is the Ultra 4640. Later Ultra models do not have the optical out. Audio mode is Auto (DD). HDMI S/PDIF is Dolby Digital.
probably need to see the logs from the app after it stops to determine why it is stopping when direct playing ac3.
I will review and post the log. Is the transcoded AC3 5.1 the same quality as of the AC3 track?
If you can’t tell, who cares? 
Plex uses a decent encoder, but mixdown is always hard. Sometimes the versions on disk are mastered differently, too - the AC3 5.1 version might have significantly louder dialog.
(I have better luck with my Roku TV + HDMI ARC if it’s set to DD. When it’s set to Auto it occasionally breaks and I have to reboot the TV (ugh!) to get audio back. But share logs w/ BigWheel for a real answer.)
Afaik it should.
If it is possible to get a sample file that does this it would be appreciated. (you can put it on google drive, drop box or similar and message me a link)
Here’s the log.
{ log removed}
I’ll have top see about a sample but the files that have the AC3 as a secondary audio track are typically from a bluray and are 20G+.
lol I thought I did. I’ll start from a fresh file.
1 Like
removed
No tax account numbers 
(yay!) but I don’t think that has what BigWheel will need in it.
Try enabling logging on the client, playing until the problem, and THEN grabbing the log.
those don’t look like your roku logs. they seem to be the web app logs. You need to turn local logging on in the app then there will be a URL on the bottom telling you which IP:port/logs to go to on a computer to pull up the roku logs. Reproduce issue refresh the page to get the logs to update then copy to a text file.
feel free to message them to me if you don’t want to post publicly. ( click on my username them message button)
Yes, this is the log from the web app. Let me see how to get the ones from the Roku. The Plex server itself is on a Pi 4. Sorry I haven’t played out with logs previously.
This is weird. It thinks it is finished and also shows only 8% finished.
does the file have forced PGS subtitles enabled
also can you run the the file through mkvclean.
If the file is too large to upload, Is it possible to create a smaller sample that still does it. Generating Sample Files from Media | Plex Support
Thanks for reviewing. I’ll check about the subtitles but these are typically created via makemkv from my BRDs and I do not change the settings nor have I changed anything related to subtitles for playback. I’ll also try the mkvclean and look into providing a sample but since this happens on many titles I have a feeling the issue isn’t with the files unless the issue is how they are created by makemkv. I’ve had to handbrake some mkv file when the video is VC1 as it isn’t supported by the Roku and these files are encoded with AC3 5.1 and work flawlessly.
Just a quick update, I moved my plex server from the Pi4 to an i5 and Plex no longer has issues transcoding to EAC3. I still get the error where playback stops suddenly if I select the AC3 track (when it exists) for playback on the Roku Plex client but that’s no longer a problem as I can now leave playback on the primary audio track (DTS HD or TrueHD) and let Plex transcode. I did create a m4v with ffmpeg to copy the video and ac3 track as is and this plays just fine on the Roku. I will also be upgrading my receiver so it will be able to decode the primary audio track going forward. So it does appear there’s a playback bug when choosing a different audio track but I’m no longer impacted by it.
This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.
