Dolby TrueHD transcode on Shield TV

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Hello,

I have some issues with some files playing from my Windows PC to an nVidia Shield. The files are pretty big (2160p remux) and when playing on Shield are totally stuttering. I figured out this was due to Plex actually transcoding the stream and choking my PC CPU, and after checking about the subtitles problem i now only facing this issue whith Dolby TrueHD selected as audio track. If i play AC3 or DTS, the CPU of my PC is only at 15%, thus i imagine it’s not transcoding.
My concern is that my receiver (Sony DN1080) is capable of Dolby TrueHD decoding and i don’t understand why Plex wants to transcode. Also if i play the same file locally on Shield TV with Kodi, it works and my receiver is audio receiver is actually showing that it is decoding TrueHD. I checked in Shield TV audio section, and Dolby TruHD is manually activated so it should be fine. So what am i missing on Plex Server/Player? Or is it a known issue ? Thanks

is the shield plugged directly into the RECEIVER? or is it plugged into the tv?

is your hdmi compatible with 4k/hdmi 2.0/hdcp 2.2?

what are your exact shield device, and plex quality settings? you want to have hdmi pass-though enabled.

kodi and plex are not the same, you cannot compare them.

post a screenshot of your server dashboard with the problem playing. you can copy/paste the image directly into a reply. actually without plex pass the dashboard won’t tell you much.

you could also try installing tautulli for better details into the streaming

if you have not already read @ Plex, 4k, transcoding, and you it might be useful, however the shield itself should play truehd fine assuming everything is configured correctly and compatible.

play the problem movie, then download logs and drag them into a reply.

Plex Web > settings > troubleshooting > download logs

Do not manually choose audio formats in the Shield audio settings. Leave the Shield set to Auto.

I have a Shield Pro 2015. When I manually select audio formats Plex always transcodes the audio, even if it is a supported format. When set to Auto, the audio direct plays.

Example:

Shield audio settings, Available formats = Auto. Play a movie with TrueHD audio. It direct plays.

Shield audio settings, Available formats = Manual. Selected formats left at default values - both Dolby Atmos & TrueHD are enabled. Play a movie with TrueHD audio. PMS transcodes the audio to AAC 5.1.

Hi,

Thanks both of you for your answers. I found the issue!
I’ve put the Shield available formats setting to Auto. This didn’t solve my issue but i’m sure this is better that way indeed.
My Shield is directly plugged into the audio receiver DN1080, but the audio is then routed to and back from TV (Panasonice EZ950) via ARC system to ensure AV sync. I knew it could be the issue but while testing yesterday i tried to deactivate “eARC” on audio receiver without change. Apparently this setting is not effective to avoid ARC routing so i was messing up my tests…
After looking at TV settings today, audio HDMI was set to bitstream as exepected but TV audio system was set to to “TV” instead of “Home Cinema”. So in a way i think TV was decoding audio audio before sending it back to receiver, and TV is maybe not compatible with TrueHD.
Now with TV settings right everything is fine with Plex and audio in Dolby TrueHD or DTS HD-MA formats.
The only thins that still causes Plex to transcode is when using VOB subtitles, but i think it’s normal and i’m ok using SRT subtitles instead.

Thanks!

Having the same issue with truehd on plex with shield. Server is running unraid with newest PMS update. I’ve tried changing all the settings to do some form of ABA testing. But in the end i can only get directplay when using kodi and plex plug-in. It works ok, but plex android app is much faster and cleaner. Did this work for like 2/3 years ago, but somehow this got broken. Video is always directplay, but the truehd is just not working. I have a samsung home theatre: HT-H7500WM which is running ARC up to my LG 4k TV. The home theatre should be capable of playing the truehd, so i dont know why it does not work, when it works flawless on kodi

Have you checked all options in your TV ? Alternatively you could try to first test without ARC loop to check if this comes from this part (best way is to use a TV HDMI input without ARC because sometimes the ARC option in menu is not effective)
I don’t know about LG TV menus but in my case the problem was that my TV somehow decoding the audio signal for itself in the middle of the ARC loop.
This was happening even if the HDMI was set to “bitstream” because the Audio Type was “TV”.

“ARC loop” does not exist.

With Shield, or any device, connected to the receiver/soundbar, the audio is processed when it is passed from the device to the receiver/soundbar. It is not somehow looped through the TV, returning via HDMI-ARC.

That would not work and it would make zero sense. HDMI-ARC does not have the bandwidth to handle lossless audio such as TrueHD and dts-HD. Furthermore, why would you unnecessarily loop audio through the TV? The entire point of connecting the Shield to the receiver is to have the shortest possible audio path and get around the limitations of HDMI-ARC.

Old HDMI ARC is limited in bandwith but eARC has the bandwith to handle formats up to Dolby Atmos and DTS:X https://www.hdmi.org/spec21Sub/EnhancedAudioReturnChannel
So i made a mistake about name but this is what you have now in TVs and receivers.
And the point of using it is to keep the audio and video in sync. If you decode the audio on receiver and then send the video to TV, the Video will take some more time to decode, resulting in audio and video out of sync. This is the point of eARC. You send both audio and video to TV, which are delayed the same and the audio is then routed back with HDMi audio return channel to audio receiver. Of course you could manually set the audio/video delay (for example in Shield TV there is an option for that or on more audio receiver), but using eARC is a bit more easier, and ensure to have correct delay compensation over different formats (because TV delay is not the same depending of what it receive and the settings (1080p, 4k, HDR or not, game mode or not…)
Also eARC allows to listen TV apps and channels into audio receiver without having another cable between the two

Well it did not work on when using my old 2015 samsung ju7005 either. The fact that it works flawless when using kodi with plex plug in makes the whole thing strange. Also i am 99% sure that the Android plex app could directplay truehd back in 2017 with the same config i am running now. Only the tv has changed, but didnt work with the samsung either.

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