LG webOS TV OLED65C9PUA Subtitle and HDR Issues

Plex Players Smart TVs
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Server Version#: 1.19.3.2831
Player Version#: 4.29.5
webOS Version#: 4.7.0

I’m having trouble getting HDR and Subtitles to work. I can HDR just fine. Subtitles work just fine too on anything 1080p. But once I try to have 4k subtitles and HDR, the HDR goes away. I have very strict living conditions (crazy stepmom) so I’m forced to used subtitles 90% of the time with the volume turned way down.

A very similar thread, that I’ve read through, is now closed is here:

The whole situation is weird. I saw that Plex developers were blaming LG because their software doesn’t do HDR and subtitles. This is wrong. I use the LG Netflix and LG Amazon apps and they work with HDR and subtitles just fine. I can see LG developers blaming PLEX, but that doesn’t make sense either because if I watch something on my Xbox One via PLEX it will do HDR and subtitles fine. So yeah, easy solution… use the Xbox. Problem is, I shouldn’t have to, and it gets HOT after a while. I also have a Raspberry Pi 4 that can direct stream everything just fine, so it’s not the TV.

I just don’t understand why a thread started back in 2018 referring to this problem still exists now in 2020 with no solution. Or has there been a solution I’m missing? Please help a guy out!

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For the Plex app on LG TVs:

  • Enabling image based subtitles, PGS & VOBSUB, results in a video transcode.
  • Text subtitles, SRT, direct play.
  • However, if the audio is transcoding, enabling SRT subtitles also results in a video transcode.

The TV direct plays AC3, EAC3, dts, & dts-HD audio. TrueHD audio will transcode.

Plex transcodes all video to 8-bit H.264. HDR information is lost in the process. Also, Plex does not tone-map HDR to SDR, so transcoded HDR video generally looks poor, with washed out colors.

So, when using the LG Plex app to watch HDR video:

  1. Never enable image based subtitles.
  2. If you listen to TrueHD audio, do not use subtitles of any type.

Note that movies on blu-ray discs with TrueHD audio also include an AC3 version of the audio track. Choose the AC3 version when possible.

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Thank you for the reply! It goes along with everything I was seeing. I had already tried all that external SRT stuff but it wasn’t working. Then on a whim I tried changing to the AC3 audio instead before you replied and seemed to be working like it should. So thanks for confirming that suspicion. I get the reasoning behind transcoding - when the playing end isn’t capable of rendering the streams. But why does it do it when everything on the audio end is being bitstreamed down to an surround receiver that supports it? That just seems odd to me. But yea, I only did this with 1 video (all I’ve got right now, nothing else to experiment with). It was in TrueHD which is apparently where the problem was. Using SRT with AC3 seemed to work.

Are their plans to tweak this in the future? Like not transcoding down TrueHD, or allowing image based subs? I have some 4K BluRay discs and I’m pretty sure they did subtitles fine. Is that because the BluRay player is doing all the work, rather than extracting and running through Plex?

In any case, thanks for your help!

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Regarding TrueHD & passing it to a receiver:

Both the TV and audio equipment must support HDMI-eARC to pass TrueHD or dts-HD audio from the TV to the audio gear. The original standard, HDMI-ARC, does not have enough bandwidth.

However, even if that is in place, no TV apps, Plex or other, can pass TrueHD audio via HDMI-eARC. This is true for all TVs, not just LG. This seems to be a limitation put in place by the TV manufacturers. Not sure why. Possibly due to the cost of licensing the TrueHD audio codec, but that is speculation on my part.

HDMI-eARC enabled TVs will passthrough TrueHD audio for devices attached to HDMI ports. So, for example, you could attach a blu-ray player to the TV, then pass TrueHD via HDMI-eARC to an attached receiver.

Regarding subtitles:

Plex will have to provide information on why the limitations exist. I do not know the details.

Also, Plex never discloses product plans, so even if it is technically possible to direct play PGS subtitles and they are working on it, we would never know until it was announced.

Net result:

If you want to hear TrueHD and TrueHD + Atmos audio, you’ll have to use a streaming box, not the Plex SmartTV app.

The Nvidia Shield is the only off the shelf device that bitstreams TrueHD audio, including TrueHD + Atmos. The Shield also direct plays image based subtitles (text too), so no video transcoding when you turn on PGS or VOBSUB subtitles.

The AppleTV 4K decodes TrueHD to PCM before passing it to the attached device. There is no loss in audio quality. However, Atmos data is lost in the process. This is an Apple limitation. They do not permit TrueHD passthrough.

You’ll end up with the following:

Shield <–HDMI–> Audio Gear <–HDMI–> TV
or
Shield <–HDMI–> TV <–HDMI-eARC–> Audio Gear

If you do get a Shield, buy the 2019 Pro model. The non-Pro model has issues with Plex right now.

My setup:
Shield <–HDMI–> Denon AVR-x4300H <–HDMI–> LG 55B7OLED

The Shield is used almost exclusively as a Plex client. I still use the Netflix & Amazon apps on the TV. Hitting the button on the TV remote for those apps is just too convenient.

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Here’s a good thread with additional information:

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I recently bought a Raspberry Pi 4 with the hopes of running Kodi on it and accessing my Plex server through that. So far, it’s been a big whammy. The standard 4K movie I got to test it with resulted in really bad pixelization and bleeding with a white horizontal bar just above the video frame. I took a video of it and posted it over at my thread for the OS I’m running, might be something fun to look at. I thought maybe it was a bad rip/encode but I only see that result with the Pi 4. When I stream the same video to the TV or through my Xbox One X, the picture is perfect. Audio needed to be AC3 to have subs, but without subs the TrueHD transcoding happened (and actually got stuck buffering).

Since I was having trouble, I went and got a REMUX version of the same video. The Pi 4 had much better success with that, but because the audio still needed transcoded down I was lost in a buffer hell. Surprisingly though, the REMUX really bonked playing direct to the TV. It gave me a big white screen with a small 1/8th screen in the top left corner that was all garbled. Played fine on the xbox though, but still had buffering issues. I think my first video was the best result, even though I have the HDR/Sub issue.

I’m hoping the Raspberry Pi 4 will mature as Kodi v19 comes into play with it. If not, I’m really only out like $40. My main goal right now is to direct stream what I can on the TV, and use the Pi 4 for it’s myriad of 3rd party addons.

Now that I think about it, I wonder how well this works with Emby. I have it running too, because it was my first media server. But I’m wanting to use Plex now because of it’s sharing capabilities, and it’s “built-in” capability with my TV. Might have to tinker more tomorrow. I’m recovering from a surgical procedure and have another 2 weeks before I have to return to work. :slight_smile:

Thanks again!

Ps; (off-topic) Is it worth it to get Plex Pass? I see a lot of people in the forums have it, but I don’t see the benefit of getting it just yet. I’ve only been a user for about 2 weeks now. I’d like to have all the bells and whistles, but the website advertisement is kind of vague. Are there features you’d miss if you didn’t have it? Thanks!

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Can’t help you with Pi/Kodi/Emby. I run none of those.

Regarding the Plex Pass, it does open up some additional capabilities, but if you don’t need it, there is no reason to purchase one. See Plex: Free vs Paid.

A Plex Pass enables hardware accelerated transcoding, taking advantage of a GPU instead of relying completely on the CPU. This can help if you’ve a low powered system and/or need to transcode multiple streams simultaneously.

Another advantage is it unlocks the mobile Android & iOS apps, eliminating the 1 minute limit on video playback (you can pay $4.99 USD one time to do the same thing).

A Plex Pass is required for other features such as Live TV & DVR, the recently announced Intro Skipping for TV shows, and PlexAmp for streaming audio.

A Plex Pass also opens up some additional controls for certain features. For example, you can limit rate of remote streams with a Plex Pass (Remote Access).

You can try Plex Pass for $4.99 USD/mo. and cancel any time. At the end of the 30 day period your account reverts to a standard non Plex Pass account.

Plex occasionally sends discounted offers to non Plex Pass users, encouraging them to purchase a lifetime Plex Pass. There is no fixed schedule. It seems to happen a couple of times per year.

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Thanks. I’ll hold on to my money for the time being. :slight_smile: I might drop and get the lifetime once I return back to work. Thanks again for your help and input!

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