Transcoding 4K - Why?

Plex Players Smart TVs
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1

I want to get to the bottom of why my media is transcoding and not direct playing.

My setup is as follows:

  • Plex Media Server is stored on a Widows 10 PC (Local Wired)
  • Plex App on my Hisense H75B7510UK TV (4K Compatible)
  • 5.1 Yamaha HTR 2071 AV Receiver (4K Compatible)

1080p media plays fine, however, when attempting to watch 4K movies, Plex is transcoding it, causing the image to have an orange/dark tinge to it.

I turned on DLNA and tried playing through that, which it does appear to play in true 4K as the colours are vibrant, however, it buffers every 1.5 seconds making it unplayable.

The Audio track on the file states 7.1 but also has the option to select 5.1, when selecting 5.1, within Plex Media Server it is showing the Video as transcoding but the Audio as direct playing.

I want to know why it is transcoding when to my knowledge everything is 4K compatible.

Please see relevant logs attached. If someone could advise before I pull all of my hair out it would be much appreciated.

Plex Transcode Log.txt (3.7 KB)

Plex Media Server Version 1.18.7.2457
Plex TV App Plex for Hisense Version 3.13.13

2

Hisense is no longer listed as a supported Smart TV by Plex: Which Smart TV models are supported?

The Plex app for Hisense TVs was last updated in Jan 2018: Plex for Smart TVs & Tivo

You may have to use a Roku / Nvidia Shield / etc to successfully play HDR video.

Regarding the log file you attached:

It shows Plex believes the TV does not support 10-bit (HDR) video. This could be due to a misconfiguration of the app or the TV, or that the app itself does not support HDR (see above WRT age, lack of support, etc).

Mar 13, 2020 18:25:43.952 [13392] DEBUG - Thor: Ragnarok - video.bitDepth limitation applies: 10 > 8

Regarding the audio, you do not mention how things are connected. Note that neither HDMI-ARC nor Toslink/Optical support 7.1 audio due to bandwidth limitations. Choose Dolby Digital or dts 5.1 audio tracks when possible to avoid audio transcoding.

3

Thanks for the reply.

I did think it was the Hisense App itself, however, I have an Xbox One (original, not X or S), and trying to watch on there (has a better app), it still transcodes, however, to my knowledge I would hazard a guess this is due to the fact the Xbox One does not support 4K? Would I be correct in saying that?

So the potential fix would be to buy an Xbox One X or the new Xbox that comes out later this year and use those? Would that resolve the issue do you think?

Regarding the audio it is connected via HDMI-ARC and this particular file has the option to select 5.1 AC3 Audio track, which is what I have been doing? The audio states Direct Play on the Plex Media Server, so from what I can tell it is the video that is causing the issue?

Is all of the above correct and would you suggest the TV app is the issue and an Xbox One X would resolve the issue and allow direct play?

4

xbox is not a very good plex client.

the best for 4k is nvidia shield, it is the ONLY mainstream streaming device to support truehd+atmos.

other good alternatives are ROKU 4k devices or perhaps appletv if you are an apple fan.

amazon fire devices can work, but are more limited (no dts and other limitations), and are more problematic (in my experience).

you may also want to read the whole thread @ Plex, 4k, transcoding, and you to learn about 4k plex in general, common pitfalls/problems/etc.

5

Thanks for the link, I had read through that quite a few times now.

From the logs, what do you think is causing it to not direct play?

6

I think it is exactly what FordGuy said, your tv doesn’t support hdr via the plex app.

the first 2 lines says it all.

Mar 13, 2020 18:25:43.952 [13392] DEBUG - Thor: Ragnarok - video.bitDepth limitation applies: 10 > 8
Mar 13, 2020 18:25:43.952 [13392] DEBUG - Thor: Ragnarok - audio.channels limitation applies: 8 > 2
Mar 13, 2020 18:25:43.952 [13392] DEBUG - MDE: Thor: Ragnarok (2017): no remuxable profile found, so video stream will be transcoded
Mar 13, 2020 18:25:43.952 [13392] DEBUG - MDE: Cannot direct stream video stream due to profile or setting limitations
Mar 13, 2020 18:25:43.952 [13392] DEBUG - Scaled up video bitrate to 221530Kbps based on 4.500000x fudge factor.
Mar 13, 2020 18:25:43.952 [13392] DEBUG - Scaled maximum bitrate for resolution reduction to 77808Kbps.
Mar 13, 2020 18:25:43.953 [13392] DEBUG - Codecs: testing aac_mf (encoder)
Mar 13, 2020 18:25:43.953 [13392] INFO - [FFMPEG] - MFT name: 'Microsoft AAC Audio Encoder MFT'
Mar 13, 2020 18:25:43.955 [13392] DEBUG - Thor: Ragnarok - audio.channels limitation applies: 6 > 2
Mar 13, 2020 18:25:43.955 [13392] DEBUG - MDE: Cannot direct stream audio stream due to profile or setting limitations
7

Even when casting the file directly (outside of Plex) to the TV it has issues.

This time you can tell the file is playing correctly with the correct colours/4K quality, however it still buffers, every half a second?

8

its difficult to say, there isn’t enough information to determine why.

you need to try to isolate if it is a network issue or tv issue or server (transcoding) issue.

it doesn’t look like anyone else has posted about this tv on this forum

https://forums.plex.tv/search?q=H75B7510U

some guesses, assuming you are trying to play a full 4k remux

  • if you are plugged into lan, tv ethernet ports are almost all 100m (which is not enough for some 4k remuxes
  • if you are using wifi, it can work but it depends on your wifi and invironment (ie both tv and router wifi speed, how much interference, other traffic, distance)
  • if server is transcoding, it might not be keeping up with the load
  • maybe the tv itself just isn’t designed to handle full 4k remuxes via plex, smart tvs and streaming devices are designed for LOW BIT RATE streaming from netflix etc.
9

Just tried on WiFi as well, and with not even using Plex, so casting directly from the file itself, still buffers every half a second.

Using Plex it transcodes, but casting directly from the file is causing issues.

I have another 4K movie but this is only 10GB in size and doesn’t buffer once.

The one that is buffering non stop is 49GB but you can tell has much more detail.

So I guess seperately, the “4K” 10GB file has had some sort of downsizing in terms of conversion and the 50GB file is proper 4K?

Could file size be a factor in why these issues are happening?

10

of course, but more likely its the bitrate of the files and whether or not the tv SOC can handle it.

trying to stuff 4k bluray remuxes to smart tvs is like driving a semi-truck/trailer down a dirt road at 100mph.

11

Is there a way I can see what the bitrate of the file is and how would I find out whether the TV can handle that?

12

you can find the bitrate/details of any video file with ‘mediainfo’ (google it).

within plex, you can ‘get info’

image

image

image

do note, displayed bitrates are only AVERAGE.

hevc files can have double or more peak bitrates.

see also @ https://www.reddit.com/r/PleX/comments/eoa03e/psa_100_mbps_is_not_enough_to_direct_play_4k/

13

So the info I have gathered is as follows:

Width 3840
Height 2160
Aspect Ratio 1.78
Video Resolution 4K
Container MKV
Video Frame Rate 24p
Video Profile main 10

Part

Duration 2:10:30
File Thor Ragnarok
Size 49.38 GB
Container MKV
Video Profile main 10

Codec HEVC
Bitrate 49229 kbps
Language English
Bit Depth 10
Chroma Subsampling 4:2:0
Coded Height 2160
Coded Width 3840
Color Primaries bt2020
Color Range tv
Color Space bt2020nc
Color Trc smpte2084
Frame Rate 23.976 fps
Height 2160
Level 5.1
Profile main 10
Ref Frames 1
Width 3840
Display Title 4K (HEVC Main 10 HDR)

Codec TRUEHD
Channels 8
Bitrate 4051 kbps
Language English
Audio Channel Layout 7.1
Bit Depth 24
Sampling Rate 48000 Hz
Title Surround 7.1
Display Title English (TRUEHD 7.1)

Codec AC3
Channels 6
Bitrate 640 kbps
Language English
Audio Channel Layout 5.1(side)
Sampling Rate 48000 Hz
Title Surround 5.1
Display Title English (AC3 5.1)

Codec PGS
Bitrate 38 kbps
Language English
Display Title English (PGS)

At this stage I am not sure what else to try? What can / do I need to do to play the file without buffering?

14

if it won’t play outside of plex, then there is probably nothing you can do, the tv simply isn’t powerful enough to do so.

trying to play 4k from plex is not the same thing as playing a 4k from a bluray player (the bluray player takes care of all the video/audio processing).

15

One thing I want to try is streaming via an Xbox One X. I don’t have it to test, but I know from just using them that the Xbox Plex App is superior to the Hisense Plex TV App.

I know on my Xbox One is streams 1080p better than the TV App, but the Xbox One still needs the file transcoding as I believe the original Xbox One cannot stream 4K.

My hope is either the Xbox One X (Or I may wait until the Xbox Series X), and one of those are capable of streaming 4K, which I hope would resolve this issue?

16

You are using an old app that was never updated to handle 4K video. There is no work around.

17

I have an xbox one x, and I can tell you from experience, that you should not buy an xbox x just for plex.

Search or browse the xbox section of this forum for plenty other people experiences.

Shield, roku/appletv4k are the only 3 you should seriously consider.

18

Just a quick update on this.

I bought an Xbox One X yesterday, it is now playing all of the 4K files, and within Plex it states “Direct Play” for both video and audio, which it previously wasn’t, is now not buffering once, doesn’t have the dark tinge (where it was transcoding I belive), and sounds great.

1 Like
19

fyi Apple 4k doesn’t do atmos/dts x on plex.

20

Try deleting the Display Title English (PGS) from the MKV. You can use mkvtoolnix for that. If you need the captions use only SRT (Subtitle Edit takes some time but works great converting files to SRT). Everytime I play a movie with a PGS or VOBSUB subtile on it, my PLEX server needs to transcode (except with the shield). Hope this help.