Will PMS transcode True HD atmos to DD+ atmos ? For ARC compatibility !

General Discussions
1

I have a 2017 oled tv and would like to carry on using the built in plex app rather than buy something like a nvidia sheild.

I am thinking of buying an atmos capable av receiver ( denon x2400 ) this weekend and I am wondering if PMS is capable of transcoding true hd atmos audio tracks to dolby digital plus atmos like the atmos streams you get on netflix.

This way I can use the built in lg plex app and pass the dolbly digital + atmos back through arc to my atmos receiver.

Anyone who knows if this is possible ??

And yes before any1 asks i know this will result in lossy audio compared to the true hd atmos but i am not that bothered and more interested in the 3d sound of atmos than absolutely perfect fidelity quality.

2

My setup: LG OLED55B7P <–HDMI–> Denon AVR-X4300H <–HDMI–> Nvidia Shield TV

Using the LG Plex app and playing a movie with only a TrueHD7.1+Atmos audio track results in zero sound. No audio is passed to the Denon.
Playing the same movie via Plex on my Nvidia Shield results in Atmos sound.

If the movie also has an AC3 5.1 track, then the LG Plex App will auto-fallback to that audio and send it to the Denon.

The LG Plex app does passthrough EAC3+Atmos to the Denon w/o issue. The Denon front display shows Atmos audio.

The results surprised me so I repeated it with a Dolby Atmos demo file. The results were the same. If the file has only a TrueHD+Atmos audio track, no audio is sent to my Denon receiver.

Here’s the MediaInfo audio portion for the blu-ray rip:

Original Movie Audio: MediaInfo for Blu-ray rip. Movie has two audio tracks: (a) TrueHD 7.1 + Atmos; and (b) AC3 5.1.
Playback via LG Plex App shows Dolby Digital on Denon receiver display.
Playback via ShieldTV shows Atmos on Denon receiver display.

! Audio #1
! ID : 2
! Format : TrueHD
! Format profile : TrueHD+Atmos / TrueHD
! Codec ID : A_TRUEHD
! Duration : 2 h 12 min
! Bit rate mode : Variable
! Bit rate : 3 901 kb/s
! Maximum bit rate : 7 407 kb/s
! Channel(s) : Object Based / 8 channels
! Channel positions : Object Based / Front: L C R, Side: L R, Back: L R, LFE
! Sampling rate : / 48.0 kHz
! Frame rate : 1 200.000 FPS (40 SPF)
! Compression mode : Lossless
! Stream size : 3.61 GiB (13%)
! Title : TrueHD Atmos 7.1
! Language : English
! Default : Yes
! Forced : No
!
! Audio #2
! ID : 3
! Format : AC-3
! Format/Info : Audio Coding 3
! Codec ID : A_AC3
! Duration : 2 h 12 min
! Bit rate mode : Constant
! Bit rate : 640 kb/s
! Channel(s) : 6 channels
! Channel positions : Front: L C R, Side: L R, LFE
! Sampling rate : 48.0 kHz
! Frame rate : 31.250 FPS (1536 SPF)
! Bit depth : 16 bits
! Compression mode : Lossy
! Stream size : 607 MiB (2%)
! Title : Dolby Digital 5.1
! Language : English
! Service kind : Complete Main
! Default : No
! Forced : No

Atmos Only movie audio: Audio from same movie with only the TrueHD 7.1 + Atmos track. AC3 5.1 track removed with MKVToolNix.
Playback via LG Plex app results in no audio from Denon receiver.
I also tried unchecking “TrueHD” in the LG Plex app audio settings to force a transcode. AC3 and EAC3 were both checked. PMS transcoded the audio to AAC, not to AC3 or EAC3.
Playback via Nvidia Shield shows Atmos on Denon receiver display.

! Audio
! ID : 2
! Format : TrueHD
! Format profile : TrueHD+Atmos / TrueHD
! Codec ID : A_TRUEHD
! Duration : 8 min 41 s
! Bit rate mode : Variable
! Bit rate : 4 145 kb/s
! Maximum bit rate : 7 407 kb/s
! Channel(s) : Object Based / 8 channels
! Channel positions : Object Based / Front: L C R, Side: L R, Back: L R, LFE
! Sampling rate : / 48.0 kHz
! Frame rate : 1 200.000 FPS (40 SPF)
! Compression mode : Lossless
! Stream size : 258 MiB (14%)
! Language : English
! Default : Yes
! Forced : No

3

@FordGuy61 said:
I also tried unchecking “TrueHD” in the LG Plex app audio settings to force a transcode. AC3 and EAC3 were both checked. PMS transcoded the audio to AAC, not to AC3 or EAC3.

OK so looks like PMS will not transcode True HD Atmos to Dolby Digital Plus Atmos :cry:

I wonder if this could be implemented in PMS as an option ?

4

Looks like no plans to do so.
See https://forums.plex.tv/discussion/comment/1641599#Comment_1641599

Check out the NVIDIA Shield for Plex. More expensive than other options, but worth it, imho. It direct plays almost everything. Probably the best off the shelf box for Plex on the market. Plex on the Shield is much better than the LG app. No ARC limits, so no problem playing HD/UHD material w/ Atmos & dts:X soundtracks. CAVEAT: For HDR video, Shield supports only HDR10. Dolby Vision and HLG videos either don’t play or transcode. This is a Shield limitation, not Plex.

I use the LG apps for Netflix & Amazon Video. I use my Shield for Plex and PS Vue streaming TV (no LG app for PS Vue).

With CEC/ARC, the Shield, LG, & Denon work well together.

With the Shield remote I can hit one button, turn on the TV & receiver, and switch the TV to the appropriate HDMI input. The Shield remote can control the volume level on the Denon (up/down, but unfortunately no mute).

With the LG remote I can switch from OTA TV/Netflix/etc to the Shield very easily. The LG picks up the HDMI naming from the Denon. The on-screen display list both the Shield and my FireTV. I pick the one I want and it switches the Denon to the correct HDMI input.

5

@FordGuy61 said:
Looks like no plans to do so.
See https://forums.plex.tv/discussion/comment/1641599#Comment_1641599

Check out the NVIDIA Shield for Plex. More expensive than other options, but worth it, imho. It direct plays almost everything. Probably the best off the shelf box for Plex on the market. Plex on the Shield is much better than the LG app. No ARC limits, so no problem playing HD/UHD material w/ Atmos & dts:X soundtracks. CAVEAT: For HDR video, Shield supports only HDR10. Dolby Vision and HLG videos either don’t play or transcode. This is a Shield limitation, not Plex.

I use the LG apps for Netflix & Amazon Video. I use my Shield for Plex and PS Vue streaming TV (no LG app for PS Vue).

With CEC/ARC, the Shield, LG, & Denon work well together.

With the Shield remote I can hit one button, turn on the TV & receiver, and switch the TV to the appropriate HDMI input. The Shield remote can control the volume level on the Denon (up/down, but unfortunately no mute).

With the LG remote I can switch from OTA TV/Netflix/etc to the Shield very easily. The LG picks up the HDMI naming from the Denon. The on-screen display list both the Shield and my FireTV. I pick the one I want and it switches the Denon to the correct HDMI input.

Thanks for your help @FordGuy61

Sounds like I may have to buy a Nvidia Shield then. Didn’t really want to as I like the Plex lg app and using the mouse thing.

Then again I was thinking about it for 24p playback and obviously will now need it if i want Atmos.

The only other option I am seeing for a Plex player that would do HDR, Atmos and 24p is the new Rock64 Single Board Computer running OpenPHT v2, but there is no ETA of when this will be available yet.

If I carry on using lg apps for Netflix and Amazon then the Nvidia Shield seems a bit overkill just for Plex.

Also now thinking I may get the Denon x3400 instead of x2400 for the eARC. I know i won’t use it yet but it adds a bit of future proofing.

Finger crossed LG add eARC to their 2017 oled’s. Doubt it though.