Server Version#: 1.24.2.4973-2b1b51db9
Player Version#: 4.62.1
Hi guys,
I’m running into an issue with the Plex app on my LG OLED55CXPUA. I’m using an Asustor AS5304T NAS as a media server (ADM version 3.5.7.RKU2 in case it matters) over a wired network connection.
Basically, enabling subtitles causes long buffer times every few seconds and effectively makes movies unwatchable. I understand that transcoding is very resource intensive and my first thought was that the NAS wasn’t able to handle it, but every other device I have tried to watch on does not have this issue. It even works fine if I go directly to the Plex site via the TV’s web browser, so the TV itself doesn’t appear to be the issue.
Is this a known problem with the Plex LG WebOS app? Are there any settings to mitigate fix this? Going in through the web browser is incredibly clunky.
I’ve tried SRT and VOBSUB and they both have the same issue. To be honest this is where I get a bit out of my depth as I don’t really know the difference between different types. In case it matters I am also using the highest quality media available so the bitrates can get high - but again, not a problem when watching on other devices or via the TV’s web browser.
VOBSUB is sourced from DVD and Bluray discs.
It is a picture-based format, (i.e. the text is actually pictures)
SRT on the other hand is a text-based format.
You can only find it on the web or get it by performing “optical character recognition” (OCR) on picture-based subtitles.
Its big pro over image-based subs is that you can
edit it easily
change the font, color or size in most players
most player devices can handle text-based subs better, so that the plex server doesn’t have to “burn” the subs into the video picture (i.e. avoiding transcoding)
Could you please copy the first ~20 lines from the Plex XML info of an affected video?
(do NOT post the URL to the XML file)
Thanks for the explanation of subtitle types. Below is the first chunk of the XML file. I got this from my laptop, which is working fine and does not experience any buffering. Not sure if there is a way to generate this from the Plex TV app that is having issues or if that makes a difference for what you are looking for.
MediaContainer size="1" allowSync="1" identifier="com.plexapp.plugins.library" librarySectionID="1" librarySectionTitle="Movies" librarySectionUUID="708d6719-6899-4edf-bd22-24ebe19eb96c" mediaTagPrefix="/system/bundle/media/flags/" mediaTagVersion="1629993823">
Video ratingKey="544" key="/library/metadata/544" guid="plex://movie/5d9f3513ca3253001ef27e38" studio="Daiei Film" type="movie" title="Ugetsu" librarySectionTitle="Movies" librarySectionID="1" librarySectionKey="/library/sections/1" originalTitle="雨月物語" contentRating="Not Rated" summary="In 16th century Japan, peasants Genjuro and Tobei sell their earthenware pots to a group of soldiers in a nearby village, in defiance of a local sage's warning against seeking to profit from warfare. Genjuro's pursuit of both riches and the mysterious Lady Wakasa, as well as Tobei's desire to become a samurai, run the risk of destroying both themselves and their wives, Miyagi and Ohama." rating="10.0" audienceRating="9.4" viewOffset="799000" lastViewedAt="1631378643" year="1953" thumb="/library/metadata/544/thumb/1631340167" art="/library/metadata/544/art/1631340167" duration="5831455" originallyAvailableAt="1953-03-26" addedAt="1631317126" updatedAt="1631340167" audienceRatingImage="rottentomatoes://image.rating.upright" chapterSource="media" ratingImage="rottentomatoes://image.rating.ripe">
Media id="978" duration="5831455" bitrate="14488" width="1488" height="1080" aspectRatio="1.33" audioChannels="1" audioCodec="flac" videoCodec="h264" videoResolution="1080" container="mkv" videoFrameRate="24p" videoProfile="high">
Part accessible="1" exists="1" id="1016" key="/library/parts/1016/1631310018/file.mkv" duration="5831455" file="/share/Plex/Movies/Ugetsu/Ugetsu.mkv" size="10561915343" container="mkv" deepAnalysisVersion="6" requiredBandwidths="29332,27811,24769,21477,20083,19239,16487,14606" videoProfile="high">
Stream id="2759" streamType="1" default="1" codec="h264" index="0" bitrate="13899" language="English" languageTag="en" languageCode="eng" bitDepth="8" chromaLocation="left" chromaSubsampling="4:2:0" codedHeight="1088" codedWidth="1488" frameRate="23.976" hasScalingMatrix="0" height="1080" level="41" profile="high" refFrames="4" requiredBandwidths="28773,27252,24210,20883,19493,18658,15905,14018" scanType="progressive" width="1488" displayTitle="1080p (H.264)" extendedDisplayTitle="1080p (H.264)"> </Stream>
Stream id="2760" streamType="2" selected="1" default="1" codec="flac" index="1" channels="1" bitrate="589" language="Japanese" languageTag="ja" languageCode="jpn" audioChannelLayout="mono" bitDepth="24" requiredBandwidths="591,591,591,591,591,591,591,591" samplingRate="48000" displayTitle="Japanese (FLAC Mono)" extendedDisplayTitle="Japanese (FLAC Mono)"> </Stream>
Stream id="2761" streamType="3" selected="1" default="1" forced="1" codec="srt" index="2" bitrate="0" language="English" languageTag="en" languageCode="eng" requiredBandwidths="1,1,1,1,1,1,1,1" title="forced" displayTitle="English Forced (SRT)" extendedDisplayTitle="forced (English SRT)"> </Stream>
/Part>
The problem with your TV might be this:
It doesn’t understand FLAC audio (and mono audio at that)
so the plex server has to transcode it to mp3 or AAC.
BUT, if the audio is transcoded AND you need subtitles, the video has to be transcoded as well.
Otherwise the audio/video synchronicity cannot be guaranteed.
So the server has to transcode the video, which causes a high CPU load on the server.
Is the audio transcoding? Check playback via Plex Dashboard.
With the Plex webOS app, if the audio is transcoding, enabling any form of subtitles results in a video transcode.
Plex Media Server will burn the subtitles into the video stream. On Linux based systems, subtitle burning occurs on the CPU, even when using hardware accelerated transcoding. Furthermore, the process is single threaded. Systems with low power CPUs, such as the Celeron in your NAS, struggle with the subtitle burning process, as they may not be able to burn subtitles in real time.
How the Plex webOS app handles subtitles:
Enabling PGS or VOBSUB subtitles results in a video transcode.
If the audio is transcoding, enabling any subtitle results in a video transcode.
If the audio is direct playing, text subtitles, SRT & VTT, direct play.
For SSA/ASS subtitles:
If Burn Subtitles = Automatic, enabling SSA/ASS subtitles results in a video transcode.
If Burn Subtitles = Image Formats Only, SSA/ASS subtitles direct play, but formatting information (location, color, etc) is lost.
Thanks for taking the time to explain this guys - this is helpful. So when bypassing the Plex WebOS app and using the TV’s browser to go to the Plex site the incompatibility with FLAC audio is not relevant? Or the encoding is handled differently? I’m just trying to understand why it works one way and not the other.
The web browser doesn’t force the workaround to prevent the drifting of the audio/video synchronicity.
In your case that is good, because it prevents video transcoding. But it could also mean that picture and sound may drift apart over time.
No. The only way I was able to get around this was to convert audio of the video file to AC-3 and include SRT subtitles (instead of PGS and other standards). WebOS is able to chew through that natively.
It was a ■■■■■ and a half going through my ~300 movies library and converting everything, but I did it in ~3 months I hope you find a better solution. I couldn’t and the PLEX team wouldn’t.
Cheers
I don’t know if it was what you meant, but I found a decent workaround: Optimizing all movies within Plex. I’ve seen people suggesting an external conversion application and that seem somewhat time intensive. In Plex it’s annoying but it took less than 10 minutes for me to start the process for around 10 series and 80 movies. Now it will take some days for the server to do the work.
Instructions:
Library - Sort the movies the movies the client can’t play with subtitles. - Right click - Optimize - Optimized for TV (Original quality might work too, I don’t know the difference) - Optimize - Repeat for all movies/series you want.
Result:
-Can play everything with subtitles in same quality (as far as I see and hear).
-Takes up double the space on the hdd.
This worked for me with LG tv and NAS QNAP TS-453D.
Edit:
I found a new way that makes it even faster:
Enter the library and find the three dots to the right and you can optimize the whole library in one click. To me it’s a bit hidden since not all “three-dot-buttons” have the “optimize” option. I needed to look around to find it. Then you can also use the sort function to only optimize part of your library.
Without subtitles, my media plays just fine without any sort of transcoding, so long as I select 3.1 Audio from the audio section (and not TrueHD 7.1). Strangely though, its logged as being Direct Play TrueHD 5.1…
If I enable subtitles and set audio to TrueHD 7.1, it for some reason transcodes the audio, video and converts the container
See my earlier post regarding how the LG Plex app handles subtitles.
Any TrueHD audio should transcode. Possibly an issue with Tautulli displaying incorrect information. You can also look at Plex Dashboard → Now Playing or pull the server logs to confirm how TrueHD is being handled.
