Playback error with True HD 7.1 and subtitles

Plex Players Smart TVs
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I am having an issue that when I try and play a movie in true HD 7.1 with subtitles I get a playback error. The subtitles are srt and I have set urn subtitles to only image format.
Subtitles work when audio is 5.1
I am using the plex app on my LG bx, the TV is connected to a denon 1600 using earc.

I don’t really know what else I can try
Playing a movie in true HD 7.1 without subtitles works perfectly but as soon as I add even a srt subtitles track, I revive the playback error.
Any help would be most appreciated.
Thanks

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TrueHD + subtitles forces a video transcode. If your server is not powerful enough to transcode the video you’ll receive an error message.

Movies release on Blu-ray with TrueHD audio also include a Dolby Digital (AC3) version of the audio track.

If available, choose the AC3 audio track. It will direct play including when SRT subtitles are enabled.

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Some additional details…

If you want to direct play all audio formats, including TrueHD + Atmos and dts/dts-HD/dts:X, you’ll need to use a Nvidia Shield Pro or Xbox One connected directly to an HDMI input on the Denon receiver.

The Shield/Xbox cannot be connected to an HDMI input on the TV. The LG BX does not support passthrough of dts audio from external devices. Source: LG BX.

See [INFO] Plex, 4k, transcoding, and you - aka the rules of 4k .

Specific to your installation…

You are running into the limitations of Smart TVs and Plex Smart TV apps.

LG TVs do not support passthrough of dts or TrueHD audio from TV based apps (LG, not Plex, limitation). When playing dts or TrueHD audio using the LG Plex app, the audio will be transcoded to a supported format.

Furthermore, Plex Smart TV apps have very limited subtitle support.

With the Plex webOS app:

  • Enabling PGS or VOBSUB subtitles results in a video transcode & subtitle burning.
  • If the audio is transcoding, enabling any subtitle format results in a video transcode and subtitle burning.
  • If the audio is direct playing, text subtitles (SRT & VTT) direct play.

With SSA/ASS subtitles:

  • If Burn Subtitles = Automatic, enabling SSA/ASS subtitles results in a video transcode and subtitle burning.
  • If Burn Subtitles = Image Formats Only, SSA/ASS subtitles direct play, but formatting information is lost (color, position, etc).

Therefore, if your system cannot transcode video and burn subtitles in real time,

  • Avoid TrueHD & dts audio when using subtitles. Dolby Digital and Dolby Digital Plus audio formats are OK.
  • Use only SRT subtitles, or ASS/SAA with Burn Subtitles = Image Format Only. Never use PGS/VOBSUB subtitles.
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Thank you for the very quick and detailed reply.

So essentially there is nothing I can do to be able to have TrueHD 7.1 sound with subtitles without either upgrading my NAS or buying a shield.

Don’t know if it matters but I have a atmos speaker setup that was the reason I wanted to use the 7.1, wouldn’t using the 5.1 sound negate that.

I also checked a video earlier and before it was direct playing the video and trueHD 7.1 but now it is transcoding the audio to EAC3. I don’t have substitles enabled.
Is this normal?

Sorry I don’t understand all this very well.

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Then you need a Plex client which does support ATMOS. Your TV definitely doesn’t.

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What I don’t understand is my tv the LG BX says that it supports atmos.
Or does it only work with the internal speakers?

Does anyone know if there is a way to play plex directly through my av receiver? Can I plug my QNAP NAS directly into the receiver and do it that way?

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There are 2 different ATMOS:

  1. is based on “lossy” compression methods and isused by internet media streaming services
  2. is based on losslessly stored audio (TrueHD) and is found on Bluray discs (and files ripped off these)

Your TV only supports 1) and even that only when played through the officially supported apps of this TV. Plex is an additional app which is usually not allowed to use this ability.

No, your NAS is not a Plex media player.
It may be a media server, but not more.

The above mentioned nVidia Shield Pro is currently the only known device which is able to handle both high-res/lossless audio and 4K / HDR as a Plex player.

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You don’t need to upgrade your NAS, receiver, or TV.

You do need to upgrade your Plex client. Use a Nvidia Shield instead of the Plex LG app.

My setup:

Nvidia Shield Pro (2015) ← HDMI → Denon 4300 ← HDMI-ARC → LG B7
Plex Server: Synology DS918+

The Shield direct plays everything I throw at it, from DVD & HD Blu-ray rips to 4K HDR movies.
The Shield direct plays PGS (Blu-ray), VOBSUB (DVD), and SRT (text) subtitles.
The Denon supports all desired audio formats, including TrueHD Atmos, Dolby Digital Plus Atmos, and dts/dts-HD/dts:X.

The 2019 Shield Pro adds support for Dolby Vision, video upscaling, and other enhancements.

Do not buy the 2019 non-Pro Shield (aka “tube” model). It has problems with high bit rate media such as 4K HDR disc rips. It suffers from audio dropouts and other problems. You can search the forum with “Shield tube” to see the reports.

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Thank you both for the replies and help.
I thought I was finished with my setup, I guess there is always an extra expense.
I guess I’ll hold off on the Nvidia Shield for the moment and just use the 5.1 track.
Thanks again.

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