Video buffering constantly when HDR tone mapping enabled

Plex Media Server Desktops & Laptops
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Hello guys. I’m wondering if there is a solution for my constant buffering issues when i’v got hdr tone mapping enabled. My plex server is on my local computer, pretty beefy machine, the plex player is on my lg cx tv. Is it possible that the tv is just not capable enough so it can decode my video without buffering issues ?

If i disable hdr tone mapping my video plays fine, but then the colors are not correct which is not really acceptable on hdr content. I can play the content fine directly on my machine, but then i defeat the whole point of plex, which is watching stuff via the inbuilt plex app on the tv.

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The real problem is that your system is transcoding the TV show.

Play the episode without subtitles enabled.

Does the episode direct play or transcode?

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The subs are srt, this is odd behavior for CX model

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I tried it both. Direct play and transcoding. I can try without subs. Like i said, it only starts buffering if i have hdr mapping enabled. And even when it buffers for some time, when it starts playing again, the footage stutters. Tried a different release, same story.

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Its working fine without subs enabled. Would it help if i load in external subs, and not play the burned in ones, i asume that is the problem ?

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Your TV should direct play (not transcode) HDR10 video, EAC3 audio, and SRT subtitles without issue.

What does the Plex Dashboard show with subs disabled? Is the video or audio transcoding or direct streaming?

No.

With the LG Plex app, if the media is direct streaming, such as when audio is transcoding, enabling any form of subtitle forces a video transcode.

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I think i found a solution. It didn’t have anything to do with subs it seems but with the sound. As soon as i enabled ac3 and eac3 in my plex settings in the tv, the movie stopped buffering and stuttering. I opened up the container info when i was playing the show, and it showed some errors with the sound, that’s why i decided to enable ac3 and eac3…

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Yes. If they were disabled, then Plex would transcode the audio, and subtitles + transcoded audio = video transcoding with the Plex LG app.

Make sure both Direct Play and Direct Stream are also enabled in the LG Plex app.

For future reference, this is how the Plex LG app behaves with subtitles. It is easy to force a video transcode, especially if the audio is transcoding.

  1. Enabling image based subtitles, PGS or VOBSUB, results in a video transcode.
  2. If audio is transcoding, enabling any subtitle results in a video transcode.
  3. If audio is direct playing, text subtitles, SRT & VTT, direct play.
  4. For ASS/SSA subtitles:
    1. If Burn Subtitles = Automatic in the Plex LG app, enabling ASS/SSA subtitles results in a video transcode.
    2. If Burn Subtitles = Only Image Formats, ASS/SSA subtitles, direct play, but formatting information (color, location, etc) may be lost.

Basically, to use the Plex LG app with subtitles and avoid video transcoding:

  • Use text subtitles - SRT/VTT
  • Choose audio tracks that direct play - AC3/EAC3/AAC
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