Subtitle forcing transcode on 4k hdr content

Server Version#: 1.23.2.4656
Player Version#: 5.17.0
Platform Version# : 3

My tv is a samsung (model QE49C7CAM) and whenever I try to play some 4k HDR content with .srt subtitle enabled it tries to transcode and fails since I have it disabled on my server (RaspberryPi 3b+).

I made sure that the files were not over the bitrate and tracks limits that Samsung imposes.
I made sure that audio was not transcoding as that + sub triggers a video transcode.

mediainfo of the file I was playing

General
Unique ID : 39542156358437459674159070168336393783 (0x1DBF8AD4261FE5635B2CD469D1356637)
Complete name : Fury (2014) [2160p HDR H265] [ENG ITA].mkv
Format : Matroska
Format version : Version 4
File size : 21.8 GiB
Duration : 2 h 14 min
Overall bit rate : 23.2 Mb/s
Movie name : Fury
Encoded date : UTC 2021-06-16 21:15:35
Writing application : mkvmerge v57.0.0 (‘Till The End’) 64-bit
Writing library : libebml v1.4.2 + libmatroska v1.6.4

Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format profile : Main 10@L5@Main
HDR format : SMPTE ST 2086, HDR10 compatible
Codec ID : V_MPEGH/ISO/HEVC
Duration : 2 h 14 min
Bit rate : 21.9 Mb/s
Width : 3 840 pixels
Height : 1 608 pixels
Display aspect ratio : 2.40:1
Frame rate mode : Constant
Frame rate : 23.976 (24000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 10 bits
Bits/(Pixel*Frame) : 0.148
Stream size : 20.6 GiB (94%)
Writing library : x265 2.8+19-bcdc610cf5f0:[Windows][GCC 7.3.0][64 bit] 10bit
Encoding settings : cpuid=1111039 / frame-threads=3 / numa-pools=8 / wpp / no-pmode / no-pme / no-psnr / no-ssim / log-level=2 / input-csp=1 / input-res=3840x1608 / interlace=0 / total-frames=193680 / level-idc=0 / high-tier=1 / uhd-bd=0 / ref=4 / no-allow-non-conformance / repeat-headers / annexb / no-aud / no-hrd / info / hash=0 / no-temporal-layers / open-gop / min-keyint=23 / keyint=250 / gop-lookahead=0 / bframes=4 / b-adapt=2 / b-pyramid / bframe-bias=0 / rc-lookahead=25 / lookahead-slices=4 / scenecut=40 / radl=0 / no-intra-refresh / ctu=64 / min-cu-size=8 / rect / no-amp / max-tu-size=32 / tu-inter-depth=1 / tu-intra-depth=1 / limit-tu=0 / rdoq-level=2 / dynamic-rd=0.00 / no-ssim-rd / signhide / no-tskip / nr-intra=0 / nr-inter=0 / no-constrained-intra / strong-intra-smoothing / max-merge=3 / limit-refs=3 / limit-modes / me=3 / subme=3 / merange=57 / temporal-mvp / weightp / no-weightb / no-analyze-src-pics / deblock=0:0 / sao / no-sao-non-deblock / rd=4 / no-early-skip / rskip / no-fast-intra / no-tskip-fast / no-cu-lossless / no-b-intra / no-splitrd-skip / rdpenalty=0 / psy-rd=2.00 / psy-rdoq=1.00 / no-rd-refine / no-lossless / cbqpoffs=0 / crqpoffs=0 / rc=crf / crf=18.0 / qcomp=0.60 / qpstep=4 / stats-write=0 / stats-read=0 / ipratio=1.40 / pbratio=1.30 / aq-mode=3 / aq-strength=1.00 / cutree / zone-count=0 / no-strict-cbr / qg-size=32 / no-rc-grain / qpmax=69 / qpmin=0 / no-const-vbv / sar=0 / overscan=0 / videoformat=5 / range=0 / colorprim=9 / transfer=16 / colormatrix=9 / chromaloc=0 / display-window=0 / master-display=G(13250,34500)B(7500,3000)R(34000,16000)WP(15635,16450)L(40000000,50) / max-cll=910,310 / min-luma=0 / max-luma=1023 / log2-max-poc-lsb=8 / vui-timing-info / vui-hrd-info / slices=1 / no-opt-qp-pps / no-opt-ref-list-length-pps / no-multi-pass-opt-rps / scenecut-bias=0.05 / no-opt-cu-delta-qp / aq-motion / hdr / hdr-opt / no-dhdr10-opt / no-idr-recovery-sei / analysis-reuse-level=5 / scale-factor=0 / refine-intra=0 / refine-inter=0 / refine-mv=0 / no-limit-sao / ctu-info=0 / no-lowpass-dct / refine-mv-type=0 / copy-pic=1 / max-ausize-factor=1.0 / no-dynamic-refine / no-single-sei
Default : Yes
Forced : No
Color range : Limited
Color primaries : BT.2020
Transfer characteristics : PQ
Matrix coefficients : BT.2020 non-constant
Mastering display color primaries : Display P3
Mastering display luminance : min: 0.0050 cd/m2, max: 4000 cd/m2
Maximum Content Light Level : 910 cd/m2
Maximum Frame-Average Light Level : 310 cd/m2

Audio #1
ID : 2
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : A_AAC-2
Duration : 2 h 14 min
Bit rate : 662 kb/s
Channel(s) : 8 channels
Channel layout : C L R Ls Rs Lb Rb LFE
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Delay relative to video : 20 ms
Stream size : 635 MiB (3%)
Language : English
Default : Yes
Forced : No

Audio #2
ID : 3
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : Dolby Digital
Codec ID : A_AC3
Duration : 2 h 14 min
Bit rate mode : Constant
Bit rate : 640 kb/s
Channel(s) : 6 channels
Channel layout : L R C LFE Ls Rs
Sampling rate : 48.0 kHz
Frame rate : 31.250 FPS (1536 SPF)
Compression mode : Lossy
Stream size : 616 MiB (3%)
Language : Italian
Service kind : Complete Main
Default : No
Forced : No

Text #1
ID : 4
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Duration : 1 h 36 min
Bit rate : 1 b/s
Count of elements : 77
Stream size : 1.29 KiB (0%)
Title : Forced
Language : English
Default : No
Forced : Yes

Text #2
ID : 5
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Duration : 2 h 3 min
Bit rate : 45 b/s
Count of elements : 1469
Stream size : 41.1 KiB (0%)
Language : English
Default : No
Forced : No

Text #3
ID : 6
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Duration : 1 h 53 min
Bit rate : 2 b/s
Count of elements : 86
Stream size : 1.88 KiB (0%)
Title : Forced
Language : Italian
Default : No
Forced : Yes

Text #4
ID : 7
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Duration : 2 h 3 min
Bit rate : 41 b/s
Count of elements : 1477
Stream size : 37.3 KiB (0%)
Language : Italian
Default : No
Forced : No

Menu
00:00:00.000 : Chapter 01
00:07:57.894 : Chapter 02
00:20:24.681 : Chapter 03
00:26:38.722 : Chapter 04
00:37:26.035 : Chapter 05
00:43:24.059 : Chapter 06
00:51:59.407 : Chapter 07
01:01:19.967 : Chapter 08
01:13:46.547 : Chapter 09
01:18:29.413 : Chapter 10
01:26:21.426 : Chapter 11
01:29:50.426 : Chapter 12
01:35:39.191 : Chapter 13
01:48:11.985 : Chapter 14
01:57:49.896 : Chapter 15
02:00:41.609 : Chapter 16

I can’t figure out what I’m doing wrong of if this is a bug,

Have similar issue with Plex Server on Windows 1.23.4.4712. Using Plex player on my LG OLED55C8. If I use subtitles I suddenly see my 4K HDR content being streamed to my TV with massive throughput (not visible in Plex Dash, but in Task Manager - see attached screenshot). If I don’t use subtitles the throughput returns to normal value - 65Mbps. My library is on SMB fileshare (QNAP NAS).

Does it give you a reason for transcode? You can open playback information and it should say there. Otherwise, we’ll need some logs to diagnose (enable Log to Server in settings first, and reproduce the transcode before sending us the logs)

@sLumpy sorry for the late replay, later this evening I’ll recreate the issue and upload the logs here

I’m really really sorry for the delay but I just didn’t have time last week to reproduce the issue…I’ll post the logs as soon as I can

I was not able to reproduce the issue and when I checked i saw that the Plex client has been updated (now 5.19.1) since I was last able to use it, and in the patch notes I saw

Use DASH on Tizen 5.5 devices, if their PMS version is at least 1.22.1

So i guess the fix to this issue is update your Plex client and server as stated above

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